Peritoneal defences and peritoneum-associated lymphoid tissue

Gastric Acid Suppression Therapy and Its Association with Peritoneal Dialysis-Associated Peritonitis in the Peritoneal Dialysis Outcomes and Practice Patterns Study (PDOPPS)

Key Points

In a large multinational cohort of PD patients, any GAS use was not associated with an increased risk of all-organism peritonitis. For peritonitis, risks were particularly high among certain classes of organisms particularly for Gram-negative, enteric, and streptococcal peritonitis episodes. The association with enteric peritonitis appeared to be stronger among H2RA users.

Background

Peritonitis is a major peritoneal dialysis–related complication. We determined whether gastric acid suppression (GAS) (proton pump inhibitor [PPI] or histamine-2 receptor antagonists [H2RAs]) use was associated with all-cause and organism-specific peritonitis in peritoneal dialysis patients.

Methods

In the Peritoneal Dialysis Outcomes and Practice Patterns Study (595 facilities, eight countries, years 2014–2022), associations between GAS use and time to first episode of all-cause peritonitis were examined using Cox proportional hazards models. The primary exposure of interest was GAS and secondarily PPI or H2RA use. Secondary outcomes were organism-specific peritonitis, peritonitis cure rates, and death.

Results

Among patients (N =23,797) at study baseline, 6020 (25.3%) used PPIs, and 1382 (5.8%) used H2RAs. Overall risks of GAS use and peritonitis risk (adjusted hazard ratio [AHR]=1.05, 95% confidence interval [CI], 0.98 to 1.13]) and use of PPI (AHR 1.06 [95% CI, 0.99 to 1.14]) or H2RA (AHR 1.02 [95% CI, 0.88 to 1.18]) did not reach statistical significance. In organism-specific analyses, GAS users displayed higher peritonitis risks for Gram-negative (AHR 1.29, 95% CI, 1.05 to 1.57), Gram-positive (AHR 1.15, 95% CI, 1.01 to 1.31), culture-negative (AHR 1.20, 95% CI, 1.01 to 1.42), enteric (AHR 1.23, 95% CI, 1.03 to 1.48), and particularly Streptococcal (AHR 1.47, 95% CI, 1.15 to 1.89) peritonitis episodes. GAS was also associated with higher overall mortality (AHR 1.13 [95% CI, 1.05 to 1.22]).

Conclusion

The association between GAS use and peritonitis risk was weaker (hazard ratio [HR] 1.05 [0.98 to 1.13]) than for streptococcal (HR 1.57 [1.15 to 1.89]) and Gram-negative (HR 1.29 [1.05 to 1.57]) peritonitis. A better understanding of mechanisms surrounding the differential effects of GAS subtype on peritonitis risks is needed. Clinicians should be cautious when prescribing GAS. The impact of GAS deprescribing on peritonitis risk requires further evaluation.

Surface material of acoustic transmitters influences the inflammatory response of rainbow trout (Oncorhynchus mykiss) during long-term implantation

Telemetry tags are a widely used technology for tracking animals that are difficult to observe in their natural environment. This technology has been increasingly used to monitor and study populations of high value salmonid species in Canadian waters. This study expands on a previous study of the impacts of tag implantation on the immune system of Rainbow Trout (Oncorhynchus mykiss). Pro-inflammatory cytokines and protein level markers were examined in fish that underwent peritoneal implantation of three tag types and compared to a sham surgery control group. The different materials on the surface of the tags showed differential immune induction extending over a two-month period. This included peritoneal total protein, IL-1β protein, the immunoglobulins IgT and IgM, as well as pro-inflammatory transcripts in the spleen. These results are suggestive of a prolonged, costly foreign body response which may be differentially induced by the different types of tag coating, with ceramic tags being least immunogenic. Examining tag impacts at the level of the immune system will facilitate the development of more biocompatible tags which will improve data fidelity. This will support more effective strategies for the management of fisheries resources.

Clinical Significance of Ascitic Fluid Polymorphonuclear Leukocyte Percentage in Patients With Cirrhosis Without Spontaneous Bacterial Peritonitis

INTRODUCTION

Absolute polymorphonuclear leukocyte (PMN) count (PMN-C) ≥250 cells/mm 3 in ascites is the diagnostic hallmark of spontaneous bacterial peritonitis (SBP) and is associated with high morbidity and mortality. However, the clinical significance of ascitic PMN percentage (PMN-%) and PMN-C in the absence of SBP as additional biomarkers for mortality and future incidence of SBP has not been determined.

METHODS

This retrospective cohort included adults with cirrhosis undergoing first-recorded paracentesis with initial PMN-C < 250 cells/mm 3 at 2 tertiary medical centers between 2015 and 2020. Patients with prior SBP were excluded. Outcomes were death and SBP development. Cox regression estimated hazard ratios (HRs) for risk of death and SBP development and Akaike information criterion to compare model fit.

RESULTS

Three hundred eighty-four adults (73% male, median age 58 years, 67% with alcohol-associated cirrhosis, median PMN-C 14 cells/mm 3 [interquartile range 5-34], and median PMN-% 10% [interquartile range 4-20]) were included in this study. Univariate risk of death increased 10% per 25-unit increase in PMN-C (95% confidence interval 1.01-1.21, P = 0.03) and 19% per 10-unit increase in PMN-% (95% confidence interval 1.06-1.33, P = 0.003) with PMN-% demonstrating better model fit in assessing mortality risk (Akaike information criterion: 1,044 vs 1,048, respectively). In models adjusted for age, chronic hepatitis C virus infection, and Model for End-Stage Liver Disease-Sodium, PMN-% was associated with risk of death (PMN-% 10%-29%, HR 1.17, P = 0.50; PMN-% ≥ 30% group, HR 1.94, P = 0.03; vs PMN-% < 10%) and SBP development (PMN-% 10%-29%, HR 1.68, P = 0.07; PMN-% ≥ 30%, HR 3.48, P < 0.001; vs PMN-% < 10%).

DISCUSSION

Our results suggest PMN-% at first paracentesis represents a better biomarker compared with PMN-C for assessing risk of death and future SBP development in patients with PMN-C < 250 cells/mm 3 .

Prophylactic abdominal drainage following appendectomy for complicated appendicitis: A meta-analysis

Background

To date, the value of prophylactic abdominal drainage (AD) following appendectomy in patients with complicated appendicitis (CA), including adults and children, has yet to be determined. This paper presents a meta-analysis of the effects of prophylactic AD on postoperative complications in patients with CA, with the goal of exploring the safety and effectiveness of prophylactic AD.

Methods

PubMed, Science Direct, Web of Science, Cochrane Library, and Embase databases were searched for relevant articles published before August 1, 2022. The primary outcomes were the complication rates [overall incidence of postoperative complications, incidence of intra-abdominal abscess (IAA), wound infection (WI), and postoperative ileus (PI), and the secondary outcome was the perioperative outcome]. The meta-analysis was performed with STATA V. 16.0A.

Results

A total of 2,627 articles were retrieved and 15 high-quality articles were eventually included after screening, resulting in a total of 5,123 patients, of whom 1,796 received AD and 3,327 did not. The results of this meta-analysis showed that compared with patients in the non-drainage group, patients in the drainage group had longer postoperative length of hospitalization (LOH) (SMD = 0.68, 95% CI: 0.01-1.35, P = 0.046), higher overall incidence of postoperative complications (OR = 0.50, 95% CI: 0.19-0.81, P = 0.01), higher incidence of WI (OR = 0.30, 95% CI: 0.08-0.51, P = 0.01) and PI (OR = 1.05, 95% CI: 0.57-1.54, P = 0.01), the differences were statistically significant. However, there was no significant difference in the incidence of IAA (OR = 0.10, 95% CI: -0.10 to 0.31, P = 0.31) between the two groups. The results of subgroup meta-analysis showed that in the adult subgroup, the overall incidence of postoperative complications in the drainage group was higher than that in the non-drainage group (OR = 0.67, 95% CI: 0.37-0.96, P = 0.01). However, there were no significant differences in IAA (OR = 0.18, 95% CI: -0.28 to 0.64, P = 0.45) and WI (OR = 0.13, 95% CI: (-0.40 to 0.66, P = 0.63) and PI (OR = 2.71, 95% CI: -0.29 to 5.71, P = 0.08). In the children subgroup, there were no significant differences in the incidence of IAA (OR = 0.51, 95% CI: -0.06 to 1.09, P = 0.08) between the two groups. The overall incidence of postoperative complications (OR = 0.46, 95% CI: 0.02-0.90, P = 0.04), incidences of WI (OR = 0.43, 95% CI: 0.14-0.71, P = 0.01) and PI (OR = 0.75, 95% CI: 0.10-1.39, P = 0.02) were significantly higher than those in the non-drainage group.

Conclusion

This meta-analysis concluded that prophylactic AD did not benefit from appendectomy, but increased the incidence of related complications, especially in children with CA. Thus, there is insufficient evidence to support the routine use of prophylactic AD following appendectomy.

Pigment epithelium-derived factor promotes peritoneal dissemination of ovarian cancer through induction of immunosuppressive macrophages

Peritoneal dissemination of ovarian cancer (OC) correlates with poor prognosis, but the mechanisms underlying the escape of OC cells from the intraperitoneal immune system have remained unknown. We here identify pigment epithelium–derived factor (PEDF) as a promoting factor of OC dissemination, which functions through induction of CD206⁺ Interleukin-10 (IL-10)–producing macrophages. High PEDF gene expression in tumors is associated with poor prognosis in OC patients. Concentrations of PEDF in ascites and serum are significantly higher in OC patients than those with more benign tumors and correlated with early recurrence of OC patients, suggesting that PEDF might serve as a prognostic biomarker. Bromodomain and extraterminal (BET) inhibitors reduce PEDF expression and limit both OC cell survival and CD206⁺ macrophage induction in the peritoneal cavity. Our results thus implicate PEDF as a driver of OC dissemination and identify a BET protein–PEDF–IL-10 axis as a promising therapeutic target for OC.

Endogenously expressed pigment epithelium–derived factor (PEDF) promotes increased survival of ovarian cancer cells in the peritoneal cavity by inducing IL-10 expression in CD206 ⁺ peritoneal macrophages.

Plasticity of monocytes and macrophages in cirrhosis of the liver

Cirrhosis of the liver is a systemic condition with raising prevalence worldwide. Patients with cirrhosis are highly susceptible to develop bacterial infections leading to acute decompensation and acute-on-chronic liver failure both associated with a high morbidity and mortality and sparse therapeutic options other than transplantation. Mononuclear phagocytes play a central role in innate immune responses and represent a first line of defence against pathogens. Their function includes phagocytosis, killing of bacteria, antigen presentation, cytokine production as well as recruitment and activation of immune effector cells. Liver injury and development of cirrhosis induces activation of liver resident Kupffer cells and recruitment of monocytes to the liver. Damage- and pathogen-associated molecular patterns promote systemic inflammation which involves multiple compartments besides the liver, such as the circulation, gut, peritoneal cavity and others. The function of circulating monocytes and tissue macrophages is severely impaired and worsens along with cirrhosis progression. The underlying mechanisms are complex and incompletely understood. Recent 'omics' technologies help to transform our understanding of cellular diversity and function in health and disease. In this review we point out the current state of knowledge on phenotypical and functional changes of monocytes and macrophages during cirrhosis evolution in different compartments and their role in disease progression. We also discuss the value of potential prognostic markers for cirrhosis-associated immuneparesis, and future immunotherapeutic strategies that may reduce the need for transplantation and death.

T cells in the peritoneum

The peritoneal cavity is a fluid-packed area that houses most of the abdominal organs, including the omentum, a visceral adipose tissue with milky patches or groups of leukocytes organized in the same way to those observed in typical lymphoid tissues. A distinct population of leukocytes patrols the peritoneal cavity and travels in and out of the milky spots, facing antigens or pathogens in the peritoneal fluid and responding appropriately. T cells may play a crucial function in regulating adaptive immune responses to antigens in the peritoneal cavity to ensure tissue homeostasis and healing. When peritoneal homeostasis is interrupted by inflammation, infection, obesity, or tumor metastasis, the omentum's dedicated fibroblastic stromal cells and mesothelial cells control peritoneal leukocyte recruitment and activation in unique ways. T cells, which employ their T cell receptor to target specific antigens, are an important component of the acquired immune response since they are present in the peritoneal cavity. The peritoneum provides a different environment for T cells to respond to pathogens. This chapter outlines the anatomy relevant to T cell function and biology, such as antigen processing/presentation, T cell activation, and the many T cell subpopulations in the peritoneal cavity, as well as their role in cancer or other infection.

Recent insights into the characteristics and role of peritoneal macrophages from ascites of cirrhotic patients

Macrophages are a diverse myeloid cell population involved in innate and adaptive immune responses, embryonic development, wound repair, and regulation of tissue homeostasis. These cells link the innate and adaptive immunities and are crucial in the development and sustainment of various inflammatory diseases. Macrophages are tissue-resident cells in steady-state conditions; however, they are also recruited from blood monocytes after local pathogen invasion or tissue injury. Peritoneal macrophages vary based on their cell complexity, phenotype, and functional capabilities. These cells regulate inflammation and control bacterial infections in the ascites of decompensated cirrhotic patients. Our recent work reported several phenotypic and functional characteristics of these cells under both healthy and pathological conditions. A direct association between cell size, CD14/CD16 expression, intracellular level of GATA-6, and expression of CD206 and HLA-DR activation/maturation markers, indicate that the large peritoneal macrophage CD14^highCD16^high subset constitutes the mature phenotype of human resident peritoneal macrophages during homeostasis. Moreover, elevated expression of CD14/CD16 is related to the phagocytic capacity. The novel large CD14^highCD16^high peritoneal subpopulation is increased in the ascites of cirrhotic patients and is highly sensitive to lipopolysaccharide (LPS)-induced activation, thereby exhibiting features of inflammatory priming. Thus, phosphorylation of ERK1/2, PKB/Akt, and c-Jun is remarkably increased in response to LPS in vitro, whereas that of p38 MAPK is reduced compared with the monocyte-derived macrophages from the blood of healthy controls. Furthermore, in vitro activated monocyte-derived macrophages from ascites of cirrhotic patients secreted significantly higher levels of IL-6, IL-10, and TNF-α and lower amounts of IL-1β and IL-12 than the corresponding cells from healthy donor’s blood. Based on these results, other authors have recently reported that the surface expression level of CD206 can be used to identify mature, resident, inflammatory peritoneal macrophages in patients with cirrhosis. Soluble CD206 is released from activated large peritoneal macrophages, and increased concentrations in patients with cirrhosis and spontaneous bacterial peritonitis (SBP) indicate reduced odds of survival for 90 d. Hence, the level of soluble CD206 in ascites might be used to identify patients with SBP at risk of death. In conclusion, peritoneal macrophages present in ascites of cirrhotic patients display multiple phenotypic modifications characterized by reduced ratio of cells expressing several membrane markers, together with an increase in the ratios of complex and intermediate subpopulations and a decrease in the classic-like subset. These modifications may lead to the identification of novel pharmaceutical targets for prevention and treatment of hepatic damage.

The "Dark Side" of Pneumoperitoneum and Laparoscopy

Laparoscopic surgery has been one of the most common procedures for abdominal surgery at pediatric age during the last few decades as it has several advantages compared to laparotomy, such as shorter hospital stays, less pain, and better cosmetic results. However, it is associated with both local and systemic modifications. Recent evidence demonstrated that carbon dioxide pneumoperitoneum might be modulated in terms of pressure, duration, temperature, and humidity to mitigate and modulate these changes. The aim of this study is to review the current knowledge about animal and human models investigating pneumoperitoneum-related biological and histological impairment. In particular, pneumoperitoneum is associated with local and systemic inflammation, acidosis, oxidative stress, mesothelium lining abnormalities, and adhesion development. Animal studies reported that an increase in pressure and time and a decrease in humidity and temperature might enhance the rate of comorbidities. However, to date, few studies were conducted on humans; therefore, this research field should be further investigated to confirm in experimental models and humans how to improve laparoscopic procedures in the spirit of minimally invasive surgeries.

C1 inhibitor mitigates peritoneal injury in zymosan-induced peritonitis

Peritonitis, due to a fungal or bacterial infection, leads to injury of the peritoneal lining and thereby forms a hazard for the long-term success of peritoneal dialysis (PD) and remains a lethal complication in patients with PD. This study investigated whether C1 inhibitor (C1-INH) could protect against the progression of peritoneal injuries with five daily administrations of zymosan after mechanical scraping of the rat peritoneum to mimic fungal peritonitis. Severe peritoneal injuries were seen in this model, accompanied by fibrinogen/fibrin exudation and peritoneal deposition of complement activation products such as activated C3 and C5b-9. However, intraperitoneal injection of C1-INH decreased peritoneal depositions of activated C3 and C5b-9, ameliorated peritoneal thickening, reduced the influx of inflammatory cells, and prevented the production of peritoneal fibrous layers with both one and two doses of C1-INH each day. Our results suggest that C1-INH might be useful to protect against peritoneal injuries after causes of peritonitis such as fungal infection. This clinically available agent may thus help extend the duration of PD.NEW & NOTEWORTHY Peritoneal injuries associated with peritonitis comprise an important issue to prevent long-term peritoneal dialysis (PD) therapy. Here, we showed that C1 inhibitor (C1-INH), as an anticomplement agent, protected against peritoneal injuries in a peritonitis animal model related to fungal infection. Therefore, C1-INH might be useful to protect against peritoneal injuries after peritonitis due to fungal infection. This clinically available agent may thus help extend the duration of PD.

Macrophages in Chronic Liver Failure: Diversity, Plasticity and Therapeutic Targeting

Chronic liver injury results in immune-driven progressive fibrosis, with risk of cirrhosis development and impact on morbidity and mortality. Persistent liver cell damage and death causes immune cell activation and inflammation. Patients with advanced cirrhosis additionally experience pathological bacterial translocation, exposure to microbial products and chronic engagement of the immune system. Bacterial infections have a high incidence in cirrhosis, with spontaneous bacterial peritonitis being the most common, while the subsequent systemic inflammation, organ failure and immune dysregulation increase the mortality risk. Tissue-resident and recruited macrophages play a central part in the development of inflammation and fibrosis progression. In the liver, adipose tissue, peritoneum and intestines, diverse macrophage populations exhibit great phenotypic and functional plasticity determined by their ontogeny, epigenetic programming and local microenvironment. These changes can, at different times, promote or ameliorate disease states and therefore represent potential targets for macrophage-directed therapies. In this review, we discuss the evidence for macrophage phenotypic and functional alterations in tissue compartments during the development and progression of chronic liver failure in different aetiologies and highlight the potential of macrophage modulation as a therapeutic strategy for liver disease.

Cytokine clearance in serum and peritoneal fluid of patients undergoing damage control surgery with abdominal negative pressure therapy for abdominal sepsis

Objectives

Open abdomen technique with negative pressure therapy (NPT) is widely used in patients with severe abdominal sepsis. The aim of this study was to evaluate cytokine clearance in serum and peritoneal fluid during NPT.

Methods

This prospective pilot study included six patients with severe abdominal sepsis requiring discontinuity resection and NPT for 48 h followed by planned reoperation. Cytokines (IL6, IL8, IL10, TNFalpha, and IL1beta) were measured in the serum and peritoneal fluid during index operation, on postoperative days 0, 1, and 2.

Results

Concentrations of cytokines in peritoneal fluid were higher than in serum. IL10 showed a clearance both in serum (to 16.6%, p=0.019) and peritoneal fluid (to 40.9%, p=0.014). IL6 cleared only in serum (to 24.7%, p=0.001) with persistently high levels in peritoneal fluid. IL8 remained high in both serum and peritoneal fluid. TNFalpha and IL1beta were both low in serum with wide range of high peritoneal concentrations. Only TNFalpha in peritoneal fluid showed significant differences between patients with ischemia vs. perforation (p=0.006).

Conclusions

The present pilot study suggests that cytokines display distinct patterns of clearance or persistence in the peritoneal fluid and serum over the first 48 h of treatment in severe abdominal sepsis with NPT.

Specialized immune responses in the peritoneal cavity and omentum

The peritoneal cavity is a fluid filled space that holds most of the abdominal organs, including the omentum, a visceral adipose tissue that contains milky spots or clusters of leukocytes that are organized similar to those in conventional lymphoid tissues. A unique assortment of leukocytes patrol the peritoneal cavity and migrate in and out of the milky spots, where they encounter Ags or pathogens from the peritoneal fluid and respond accordingly. The principal role of leukocytes in the peritoneal cavity is to preserve tissue homeostasis and secure tissue repair. However, when peritoneal homeostasis is disturbed by inflammation, infection, obesity, or tumor metastasis, specialized fibroblastic stromal cells and mesothelial cells in the omentum regulate the recruitment of peritoneal leukocytes and steer their activation in unique ways. In this review, the types of cells that reside in the peritoneal cavity, the role of the omentum in their maintenance and activation, and how these processes function in response to pathogens and malignancy will be discussed.

T Lymphocytes: The “Cellular” Arm of Acquired Immunity in the Peritoneum

T cells are an important part of the acquired immune response and target specific antigen with their T cell receptor. The peritoneum is a special milieu within which T cells react. We describe briefly the anatomy important for T cell function. T cell biology including antigen presentation, T cell activation, and the different T cell subpopulations are reviewed. We also define innate and acquired immunity and describe the role of polymorphonuclear cells and peritoneal mesothelial cells in the regulation of leukocyte population recruitment during peritonitis. We focus particularly on peritoneal lymphocytes and compare them to the regular lymphocyte populations in the circulation. We illustrate the role of PMCs in antigen presentation and discuss the changes of CD4+ helper T cell subtypes (Th1 and Th2) during peritoneal dialysis. The role of CD8+ cytotoxic T lymphocytes and their possible destructive role for the peritoneal membrane modified by advanced glycation end products are discussed. Polymorphonuclear cells play an important role in the regulation of inflammation and immunity. We describe their possible role in supporting T cells and particularly for generating memory CD8+ T cells by secretion of interleukin-15, a potent T cell growth factor. Light is shed on γδ T cells, a special T cell population that is able to recognize antigens without the restriction of antigen presentation. We end our review with a description of regulatory T cells. This cell population is extremely important in preventing autoimmunity and in the regulation of acquired immunity.

The Peritoneum: Beyond the Tissue - A Review

Background: Despite its complexity, the peritoneum is usually underestimated in classical medical texts simply as the surrounding tissue (serous membrane) of the gut. Novel findings on physiology and morphology of the peritoneum and mesothelial cell exist but they are usually focused or limited to Continuous Ambulatory Peritoneal Dialysis research and practice. This review aims to expose, describe and analyze the most recent evidence on the peritoneum’s morphology, embryology and physiology.

Materials and Methods: A literature review was performed on Pubmed and MEDLINE. With no limit of publication date, original papers and literature reviews about the peritoneum, the peritoneal cavity, peritoneal fluid, and mesothelial cells were included (n = 72).

Results: Peritoneum develops in close relationship to the gut from an early period in embryogenesis. Analyzing together the development of the primitive gut and the surrounding mesothelium helps understanding that the peritoneal cavity, the mesenteries and other structures can be considered parts of the peritoneum. However, some authors consider that structures like the mesenteries are different to the peritoneum. The mesothelial cell has a complex ultrastructural organization with intercellular junctions and apical microvilli. This complexity is further proven by the large array of functions like selective fluid and cell transport; physiological protective barrier; immune induction, modulation, and inhibition; tissue repair and scarring; preventing adhesion and tumoral dissemination; cellular migration; and the epithelial-mesenchymal transition capacity.

Conclusion: Recent evidence on the anatomy, histology, and physiology of the peritoneum, shows that this structure is more complex than a simple serous membrane. These results call for a new conceptualization of peritoneum, and highlight the need of adequate research for identifying clinical relevance of this knowledge.

Abdominal Drainage After Laparoscopic Appendectomy in Children: An Endless Controversy?

BACKGROUND

Routine prophylactic abdominal drains after laparoscopic appendectomy for perforated appendicitis in children are still controversial. Throughout the history of surgery, potential benefits of the abdominal drains have been described. However, in recent studies, no benefits were observed and serious complications have been reported.

METHODS

From January 2000 to December 2013, all charts of the pediatric patients who underwent laparoscopic appendectomy in our tertiary center were revised. The data from 1736 appendectomies were analyzed. We only included those patients with perforated appendicitis treated with early appendectomy (n = 192). Prophylactic drains were established according to the surgeon's preference. The sample was divided into two groups, those with drain (n = 117) and those without drain (n = 75). Demographics, operative findings, and postoperative outcomes were analyzed in both groups.

RESULTS

Of all patients, 121 were male and 71 were female with a mean age of 7.77 ± 3.4 years. There were not statistically significant differences between the groups in gender (p = 0.82) and mean age (p = 0.31). There were no statistically significant differences between the two groups in the rate of intra-abdominal abscess, wound infection, and bowel obstruction. However, the drainage group has been statistically associated with an increased requirement of antibiotic and analgesic medication, fasting time, operative time, and length of hospital stay.

CONCLUSION

The prophylactic use of abdominal drainage after laparoscopic appendectomy for perforated appendicitis in children does not prevent postoperative complications and may be associated with negative outcomes. Prospective randomized studies will be necessary to verify this question.

The peritoneum: healing, immunity, and diseases

The peritoneum defines a confined microenvironment, which is stable under normal conditions, but is exposed to the damaging effect of infections, surgical injuries, and other neoplastic and non-neoplastic events. Its response to damage includes the recruitment, proliferation, and activation of a variety of haematopoietic and stromal cells. In physiological conditions, effective responses to injuries are organized; inflammatory triggers are eliminated; inflammation quickly abates; and the normal tissue architecture is restored. However, if inflammatory triggers are not cleared, fibrosis or scarring occurs and impaired tissue function ultimately leads to organ failure. Autoimmune serositis is characterized by the persistence of self-antigens and a relapsing clinical pattern. Peritoneal carcinomatosis and endometriosis are characterized by the persistence of cancer cells or ectopic endometrial cells in the peritoneal cavity. Some of the molecular signals orchestrating the recruitment of inflammatory cells in the peritoneum have been identified in the last few years. Alternative activation of peritoneal macrophages was shown to guide angiogenesis and fibrosis, and could represent a novel target for molecular intervention. This review summarizes current knowledge of the alterations to the immune response in the peritoneal environment, highlighting the ambiguous role played by persistently activated reparative macrophages in the pathogenesis of common human diseases. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Predicting Value of Serum Procalcitonin, C-Reactive Protein, Drain Fluid Culture, Drain Fluid Interleukin-6, and Tumor Necrosis Factor-α Levels in Anastomotic Leakage after Rectal Resection

BACKGROUND

Anastomotic leak is the most dreaded septic complication of colorectal surgical procedures. Death is proportional to the time between occurrence and diagnosis of the leakage. Biomarkers, which may help to predict anastomotic leakage before appearance of its clinical features, may be beneficial in preventing adverse outcomes. This study investigates a biomarker that might be useful to predict rectal anastomotic leakage before its clinical presentation.

PATIENTS AND METHODS

Serum procalcitonin and C-reactive protein (CRP) levels, bacterial proliferation, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels of drain fluid were evaluated in 50 consecutive patients who underwent low anterior resection without diverting ostomy for rectal carcinoma.

RESULTS

Anastomotic leakage occurred in seven of 50 (14%) patients. Serum CRP and procalcitonin levels at post-operative day three were higher in patients with anastomotic leakage (p = 0.01, p = 0.02 respectively). Drain TNF-α values were increased 63.2% on post-operative day five when compared with post-operative day three in patients with anastomotic leakage, but were decreased in patients without leakage. There was no statistical difference for drain IL-6 levels between groups. The bacterial proliferation rate of drain fluid culture in the leakage group was 42.9% at post-operative day three and 85.7% at post-operative day five (p = 0.29 and p = 0.0001, respectively).

CONCLUSIONS

High serum CRP and procalcitonin values on post-operative day three are alarming, and assessment of anastomotic leakage by abdominal imaging with rectal contrast is suggested. In addition, increasing levels of TNF-α and bacterial proliferation in drain fluid are predictive, whereas IL-6 is not.

[Pathophysiology of peritonitis]

Despite intensive research efforts peritonitis leading to subsequent sepsis remains associated with a high mortality. The initial effector cells are the locally residing cells of the peritoneum, such as mesothelial cells, mast cells, macrophages and lymphocytes. Through the secretion of chemokines, an influx of neutrophils initially takes place followed by monocytes. The latter can differentiate into inflammatory macrophages. The non-directed activity of neutrophilic granulocytes is limited by the induction of apoptotic programs. Through the breaching of cytokines, bacteria and microbial products into the circulation, a systemic reaction in the sense of systemic inflammatory response syndrome (SIRS) or sepsis arises. This is viewed as a concomitant derailing of inflammatory as well as anti-inflammatory responses, which leads to extensive apoptosis of lymphocytes. The presentation of apoptotic cells leads to a strong immunosuppression. Due to the coexistence of hyperinflammation and immunosuppression, exact knowledge of the current immune status of the patient is a prerequisite in the development of immunotherapies for the treatment of sepsis.

Pediatric appendectomy: the outcome differences between pediatric surgeons and general surgeons

PURPOSE

The aim of this study was to review our experience of pediatric appendectomy performed by either a general surgeon (GS) or a pediatric surgeon (PS) to determine any differences in outcomes.

METHODS

We reviewed the medical records of pediatric appendicitis patients, 4 years before (GS group, 2007-2010) and after (PS group, 2011-2014) the introduction of a pediatric surgical practice. The records were reviewed for the following variables: operation time, length of hospital stay, complications, readmission in ≤30 days, type of operation, negative for appendicitis, drainage, open conversion, and reoperation in ≤30 days.

RESULTS

Over 8 years, 400 patients were operated on for acute appendicitis, with the PS group comprising 61 % (N = 244) of patients. The operation time (55.1 vs 43.2 min, p = 0.0001) and postoperative length of hospital stay (3.5 vs 2.7 days, p = 0.001) were shorter, more patients were treated by laparoscopy (61.3 vs 91.2 %, p = 0.0001), and a fewer patients required peritoneal drainage (29.5 vs 63.2 %, p = 0.023) in the PS group than in the GS group. The negative appendectomy rate was slightly lower in the PS group, but not to a statistically significant degree.

CONCLUSION

The patients in the PS group enjoyed a reduced operation time and length of hospital stay, greater likelihood of laparoscopic operation, and less peritoneal drainage than the patients in the GS group.

Drain insertion after appendectomy in children with perforated appendicitis based on a single-center experience

PURPOSE

Management of appendicitis in children has always been an issue in pediatric surgery. Both diagnostic methods and treatment vary significantly among medical centers, and little consensus exists in many aspects of the care for patients with appendicitis. Here, we assessed the value of drain insertion after appendectomy in children.

METHODS

This study is a retrospective review of pediatric patients who underwent appendectomy for perforated appendicitis at a tertiary medical center between 2003 and 2012. Patients who had a peritoneal drain inserted after appendectomy were compared with patients without drains regarding preoperative features and postoperative outcomes. Statistical analyses included a 2-tailed Student t-test and a chi-square or Fisher exact test.

RESULTS

In total, 958 patients were reviewed. Of 342 patients with perforated appendicitis, 108 (31.6%) had Jackson-Pratt (JP) drains inserted. The JP group had a longer hospital stay compared with the non-JP group (6.38 ± 3.59 days vs. 3.87 ± 2.38 days, P < 0.001). The JP group also had higher complication rates (22.2% vs. 6.8%, P = 0.003), including the formation of intra-abdominal abscesses.

CONCLUSION

According to our results, there seems to be little evidence to support peritoneal drain insertion after appendectomy, even in perforated appendicitis cases.

Production of intraperitoneal interleukin-6 following open or laparoscopic assisted distal gastrectomy

The interleukin (IL)-6 concentration in plasma or serum has been considered to represent the degree of stress resulting from surgery. However, IL-6 in peritoneal fluid has rarely been considered. The aim of this study was to assess the concentration and amount of IL-6 in peritoneal fluid as indicators of surgical stress. To obtain basic data on peritoneal release of IL-6 during gastric cancer surgery, we measured IL-6 in peritoneal drainage samples, stored for up to 72 hours postoperatively, from patients who had undergone conventional open (ODG group, n = 20) and laparoscopic-assisted (LADG group, n = 19) distal gastrectomy. Within 24 hours, 61 and 77% of the IL-6 was released into the peritoneal cavity in the LADG and ODG groups, respectively. In both groups, the concentration and amount of peritoneal fluid IL-6 were significantly correlated with each other (LADG group: Spearman's rank correlation test [rS] = 0.48, P = 0.04; ODG group: rS = 0.58, P = 0.01). The concentration and amount of IL-6 in peritoneal fluid was 2.8- and 3.6-fold higher in the ODG than in the LADG group, respectively (P < 0.01). With regard to the relationship between the serum C-reactive protein (CRP) peak and the concentration or amount of peritoneal fluid IL-6 released within 24 hours, only the concentration of peritoneal fluid IL-6 in the LADG group was significantly correlated (rS = 0.60, P = 0.01) with the serum CRP peak. Our findings suggest that the amount and concentration of IL-6 released into the peritoneal cavity for up to 24 hours after surgery can each be a reliable parameter for assessment of surgical stress.

Effect of gastric acid suppressants and prokinetics on peritoneal dialysis-related peritonitis

AIM: To investigate the effect of gastric acid suppressants and prokinetics on peritonitis development in peritoneal dialysis (PD) patients.

METHODS: This was a single-center, retrospective study. The medical records of 398 PD patients were collected from January 2000 to September 2012 and analyzed to compare patients with at least one episode of peritonitis (peritonitis group, group A) to patients who never had peritonitis (no peritonitis group, group B). All peritonitis episodes were analyzed to compare peritonitis caused by enteric organisms and peritonitis caused by non-enteric organisms.

RESULTS: Among the 120 patients who met the inclusion criteria, 61 patients had at least one episode of peritonitis and 59 patients never experienced peritonitis. Twenty-four of 61 patients (39.3%) in group A and 15 of 59 patients (25.4%) in group B used gastric acid suppressants. Only the use of H2-blocker (H2B) was associated with an increased risk of PD-related peritonitis; the use of proton pump inhibitors, other antacids, and prokinetics was not found to be a significant risk factor for PD-related peritonitis. A total of 81 episodes of peritonitis were divided into enteric peritonitis (EP) or non-enteric peritonitis, depending on the causative organism, and gastric acid suppressants and prokinetics did not increase the risk of EP in PD patients.

CONCLUSION: The use of H2B showed a trend for an increased risk of overall PD-related peritonitis, although further studies are required to clarify the effects of drugs on PD-related peritonitis.

Randomized comparison of surgical stress and the nutritional status between laparoscopy-assisted and open distal gastrectomy for gastric cancer

BACKGROUND

Laparoscopy-assisted distal gastrectomy (LADG) for gastric cancer may prevent the development of an impaired nutritional status due to reduced surgical stress compared with open distal gastrectomy (ODG).

METHODS

This study was performed as an exploratory analysis of a phase III trial comparing LADG and ODG for stage I gastric cancer during the period between May and December of 2011. All patients received the same perioperative care via fast-track surgery. The level of surgical stress was evaluated based on the white blood cell count and the interleukin-6 (IL-6) level. The nutritional status was measured according to the total body weight, amount of lean body mass, lymphocyte count, and prealbumin level.

RESULTS

Twenty-six patients were randomized to receive ODG (13 patients) or LADG (13 patients). The baseline characteristics and surgical outcomes were similar between the two groups. The median IL-6 level increased from 0.8 to 36.3 pg/dl in the ODG group and from 1.5 to 53.3 pg/dl in the LADG group. The median amount of lean body mass decreased from 48.3 to 46.8 kg in the ODG group and from 46.6 to 46.0 kg in the LADG group. There are no significant differences between two groups.

CONCLUSIONS

The level of surgical stress and the nutritional status were found to be similar between the ODG and LADG groups in a randomized comparison using the same perioperative care of fast-track surgery.

Drainage vs no drainage in secondary peritonitis with sepsis following complicated appendicitis in adults in the modern era of antibiotics

AIM

To compare the profile of postoperative outcome in secondary peritonitis with sepsis due to complicated appendicitis in two cohorts (drainage vs no-drainage) after appendicectomy in adults in the modern era of effective antibiotics.

METHODS

A retrospective review of all adult patients who were operated for secondary peritonitis with sepsis due to complicated appendicitis was carried out. Total of 209 patients were identified from May 2005 to April 2009 with operative findings of gangrenous or perforated appendix. The patients were divided into two cohorts, those where prophylactic drainage was established (n = 88) and those where no drain was used (n = 121). Abdominal drain was removed once the drainage ceased or decreased (< 10-20 mL/d in closed system of drainage or when once daily dressing was minimally soaked in open system). Broad spectrum antibiotics to cover the gut flora were started in both cohorts at diagnosis and were stopped once septic features resolved. Peritoneal fluid for aerobic culture and sensitivity were routinely obtained intra operatively; however antibiotic regimens were not changed unless patient failed to respond to the antibiotics based on the institutional protocol. The co-morbidities and their influence on primary end points were noted. Immunocompromised patients, appendicitis complicated by inflammatory bowel disorder and tumors were excluded from the study.

RESULTS

Disease stratification and other demographic features were comparable in both cohorts. There was zero mortality in drainage group while as one patient (0.82%) died in the non-drainage group. The median duration (in days) of hospital stay (6.5 vs 4); antibiotic use (5 vs 3.5); regular parental analgesic use (5 vs 3.5) and paralytic ileus (2.5 vs 2) was more common in the drainage group. Incidence of major wound infection in patients 14 (15.9%) vs 22 (18.18%) and residual intra-abdominal sepsis (inter loop collection/abscess) -7 (8%) vs 13 (10.74%) requiring secondary intervention was not significantly different in drainage and non-drainage cohorts respectively. One patient in the drainage cohort had faecal fistula (1.1%).

CONCLUSION

The complicated appendicitis in the modern era of antibiotics does not necessitate the use of prophylactic drain placement which at times may even prove counterproductive.

Advantages of abandoning abdominal cavity irrigation and drainage in operations performed on children with perforated appendicitis

PURPOSE

This study evaluates the effect of peritoneal irrigation and drainage on postoperative morbidity when used together for perforated appendicitis.

MATERIAL AND METHODS

This study was conducted on children undergoing open appendectomy for perforated appendicitis. Sixty-one children with perforated appendicitis operated on with irrigation and drainage between July 1998 and September 2001 (group DI) and 173 children with perforated appendicitis who underwent surgery without irrigation and drainage (group NDI) between October 2001 and November 2011 were retrospectively evaluated (a total of 234 patients). All patients were treated and followed up by the same pediatric surgeon using the same protocol. Both groups were compared in respect to postoperative complications, including wound infection, wound dehiscence, intraabdominal abscess, prolonged ileus, the presence of small bowel obstruction requiring surgery, operative time, and length of postoperative hospital stay.

RESULTS

Of the total 234 patients, 151 were male and 83 were female with a mean age of 8.9 ± 3.7 years (range, 1.5-15 years). The wound infection rates were 4.9% in group DI and 1.7% in group NDI (P = .184). Wound dehiscence was seen in 1.6% vs 0%, prolonged ileus in 8% vs 2.3%, intraabdominal abscess in 4.9% vs 1.7%, and small bowel obstruction requiring surgery in 1.6% vs 0.6% of the patients (P = .261, P = .054, P = .184, and P = .454, respectively). No statistically significant difference in postoperative infectious complications was found between both groups. The length of postoperative hospital stay was 9.9 ± 4.1 days in group DI vs 6.3 ± 2.4 days in group NDI (P < .001). The operation times were 39 ± 8 and 31 ± 11 minutes, respectively (P < .001).

CONCLUSION

This study demonstrates that peritoneal irrigation and drainage in children with perforated appendicitis is not required, and in fact, these procedures cause an increase in operative time.

Cellular therapies supplement: the peritoneum as an ectopic site of hematopoiesis following in utero transplantation

BACKGROUND

In utero transplantation (IUT) has the potential to treat birth defects early before full development of the immune system. Relatively small grafts, which are not matched for major histocompatibility antigens, can be delivered even before onset of disease symptoms. IUT of hematopoietic stem cells is usually performed via intraperitoneal injection, yet the fate of donor cells in the peritoneal cavity is not fully understood. We review our recent work and present new data demonstrating that the peritoneum can be a site of ectopic hematopoiesis with implications for IUT and immune tolerance induction.

STUDY DESIGN AND METHODS

Haplogeneic and allogeneic fetal transplants were performed in mice and engraftment tracked by flow cytometry. Immune tolerance was studied by mixed lymphocyte reactions and skin transplantation. Adult syngeneic murine transplants and xenogeneic human into immunodeficient mouse transplants were performed to follow hematopoietic retention in the peritoneum and engraftment of the marrow.

RESULTS

Although most transplanted cells rapidly clear the peritoneum, hematopoietic cells and cells with the phenotype of hematopoietic precursors can remain in the peritoneal cavity for months after transplant. The presence of donor cells in the peritoneum can contribute to donor-specific tolerance, but sufficient peripheral blood chimerism is required to ensure acceptance of donor skin grafts.

CONCLUSION

Ectopic hematopoiesis and the survival of stem cells in the peritoneum offer the possibility of better using the peritoneal cavity to delivery stem cells and foster the development of immune tolerance to alloantigens or other foreign antigens.

Kinetics of proinflammatory cytokines after intraperitoneal injection of tribromoethanol and a tribromoethanol/xylazine combination in ICR mice

Tribromoethanol (2,2,2-tribromoethanol, TBE) is a popular injectable anesthetic agent used in mice in Korea. Our goal was to assess the risks associated with side effects (lesions) in the abdominal cavity, especially at high doses. To understand the underlying pathophysiological changes, we examined levels of cytokines through ELISA of abdominal lavage fluid and spleen collected from mice treated with low and high-dose TBE. ICR mice were anesthetized using one of the following protocols: a combination of TBE 200 mg/kg (1.25%) and xylazine 10 mg/kg; TBE 400 mg/kg (1.25%); and TBE 400 mg/kg (2.5%). Administration of high-dose TBE (400 mg/kg) increased the interleukin-1β and interleukin-6 levels in the peritoneal cavity over the short term (<1 day) compared with sham controls and low-dose TBE (200 mg/kg) groups. Cytokine expression in the low-dose TBE group was similar to the control group, whereas in the high-dose TBE group cytokine levels were higher in abdominal lavage fluid and spleen over the long term (10 days post-injection). We conclude that a combination of TBE 200 mg/kg (1.25%) and xylazine (10 mg/kg) is a safe and effective anesthetic for use in animals.

The in vivo mechanism of action of CD20 monoclonal antibodies depends on local tumor burden

BACKGROUND

CD20 monoclonal antibodies are widely used in clinical practice. Antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity and direct cell death have been suggested to be important effector functions for CD20 antibodies. However, their specific contributions to the in vivo mechanism of action of CD20 immunotherapy have not been well defined.

DESIGN AND METHODS

Here we studied the in vivo mechanism of action of type I (rituximab and ofatumumab) and type II (HuMab-11B8) CD20 antibodies in a peritoneal, syngeneic, mouse model with EL4-CD20 cells using low and high tumor burden.

RESULTS

Interestingly, we observed striking differences in the in vivo mechanism of action of CD20 antibodies dependent on tumor load. In conditions of low tumor burden, complement was sufficient for tumor killing both for type I and type II CD20 antibodies. In contrast, in conditions of high tumor burden, activating FcγR (specifically FcγRIII), active complement and complement receptor 3 were all essential for tumor killing. Our data suggest that complement-enhanced antibody-dependent cellular cytotoxicity may critically affect tumor killing by CD20 antibodies in vivo. The type II CD20 antibody 11B8, which is a poor inducer of complement activation, was ineffective against high tumor burden.

CONCLUSIONS

Tumor burden affects the in vivo mechanism of action of CD20 antibodies. Low tumor load can be eliminated by complement alone, whereas elimination of high tumor load requires multiple effector mechanisms.

Use of attenuated paramyxoviruses for cancer therapy

Paramyxoviruses, measles virus (MV), mumps virus (MuV) and Newcastle disease virus (NDV), are well known for causing measles and mumps in humans and Newcastle disease in birds. These viruses have been tamed (attenuated) and successfully used as vaccines to immunize their hosts. Remarkably, pathogenic MuV and vaccine strains of MuV, MV and NDV efficiently infect and kill cancer cells and are consequently being investigated as novel cancer therapies (oncolytic virotherapy). Phase I/II clinical trials have shown promise but treatment efficacy needs to be enhanced. Technologies being developed to increase treatment efficacy include: virotherapy in combination with immunosuppressive drugs (cyclophosphamide); retargeting of viruses to specific tumor types or tumor vasculature; using infected cell carriers to protect and deliver the virus to tumors; and genetic manipulation of the virus to increase viral spread and/or express transgenes during viral replication. Transgenes have enabled noninvasive imaging or tracking of viral gene expression and enhancement of tumor destruction.

Early detection of anastomotic leakage after elective low anterior resection

BACKGROUND

Colorectal anastomotic leakage is a serious complication leading to major postoperative morbidity and mortality. In the present study, we investigated the early detection of anastomotic leakage before its clinical presentation.

METHOD

Fifty-six patients with rectal cancer were included prospectively in this study. All patients underwent elective low anterior resection. Peritoneal samples were collected from the abdominal drains at the first, third, and fifth days postoperatively for bacteriological study (quantitative cultures for both aerobes and anaerobes) and cytokines (IL-6, IL-10, TNF) measurement. Patients were divided into two groups: those without symptomatic or clinical evidence of anastomotic leakage (AL; group 1) and those with clinical evidence of AL (group 2). Study variables included hospital stay, wound infection, operative time, blood loss, height of anastomosis, intraperitoneal cytokines, and microbiological study of peritoneal fluid.

RESULT

Clinically evident AL occurred in eight patients (14.3%) and diagnosed postoperatively on median day 6. Intraperitoneal bacterial colonization and cytokine levels were significantly higher in patients with clinical evidence of AL. Wound infection was significantly higher in anastomotic leakage group. The hospital stay for the patients with anastomotic leakage was significantly longer than those without AL (14 ± 1.41 vs. 5.43 ± 0.89 days). A significant difference among two groups was observed regarding operative time, blood loss, blood transfusion, and height of the anastomosis.

CONCLUSION

The peritoneal cytokines levels and intraperitoneal bacterial colonization might be an additional diagnostic tool that can support the decision making of surgeons for early detection of anastomotic leak in colorectal surgery.

Peritoneal changes due to laparoscopic surgery

Background

Laparoscopic surgery has been incorporated into common surgical practice. The peritoneum is an organ with various biologic functions that may be affected in different ways by laparoscopic and open techniques. Clinically, these alterations may be important in issues such as peritoneal metastasis and adhesion formation.

Methods

A literature search using the Pubmed and Cochrane databases identified articles focusing on the key issues of laparoscopy, peritoneum, inflammation, morphology, immunology, and fibrinolysis.

Results

Laparoscopic surgery induces alterations in the peritoneal integrity and causes local acidosis, probably due to peritoneal hypoxia. The local immune system and inflammation are modulated by a pneumoperitoneum. Additionally, the peritoneal plasmin system is inhibited, leading to peritoneal hypofibrinolysis.

Conclusion

Similar to open surgery, laparoscopic surgery affects both the integrity and biology of the peritoneum. These observations may have implications for various clinical conditions.

Peritoneal damage: the inflammatory response and clinical implications of the neuro-immuno-humoral axis

BACKGROUND

The peritoneum is a bilayer serous membrane that lines the abdominal cavity. We present a review of peritoneal structure and physiology, with a focus on the peritoneal inflammatory response to surgical injury and its clinical implications.

METHODS

We conducted a nonsystematic clinical review. A search of the Ovid MEDLINE database from 1950 through January 2009 was performed using the following search terms: peritoneum, adhesions, cytokine, inflammation, and surgery.

RESULTS

The peritoneum is a metabolically active organ, responding to insult through a complex array of immunologic and inflammatory cascades. This response increases with the duration and extent of injury and is central to the concept of surgical stress, manifesting via a combination of systemic effects, and local neural pathways via the neuro-immuno-humoral axis. There may be a decreased systemic inflammatory response after minimally invasive surgery; however, it is unclear whether this is due to a reduced local peritoneal reaction.

CONCLUSIONS

Interventions that dampen the peritoneal response and/or block the neuro-immuno-humoral pathway should be further investigated as possible avenues of enhancing recovery after surgery, and reducing postoperative complications.

Meta-analysis of the effect of peritoneal lavage on survival in experimental peritonitis

Background

Morbidity and mortality associated with bacterial peritonitis remain a challenge for contemporary surgery. Despite great surgical improvements, death rates have not improved. A secondary debate concerns the volume and nature of peritoneal lavage or washout—what volume, what carrier and what, if any, antibiotic or antiseptic?

Methods

A literature search of experimental studies assessing the effect of peritoneal lavage following peritonitis was conducted using Medline, EMBASE and Cochrane databases. Twenty-three trials met predetermined inclusion criteria. Data were pooled and relative risks calculated.

Results

In an experimental peritonitis setting a mortality rate of 48·9 per cent (238 of 487) was found for saline lavage compared with 16·4 per cent (106 of 647) for antibiotic lavage (absolute risk reduction (ARR) 32·5 (95 per cent confidence interval (c.i.) 27·1 to 37·7) per cent; (P &lt; 0·001). An ARR of 25·0 (95 per cent c.i. 17·9 to 31·7) per cent P &lt; 0·001) was found for the use of saline compared with no lavage at all. The survival benefit persisted regardless of systemic antibiotic therapy. Antiseptic lavage was associated with a very high mortality rate (75·0 per cent).

Conclusion

Pooled data from studies in experimental peritonitis demonstrated a significant reduction in mortality with antibiotic lavage.

Peritoneal macrophages are important for the early containment of Enterococcus faecium peritonitis in mice

The increasing incidence of infections with multi-drug resistant Enterococcus faecium necessitates studies to increase knowledge on the pathogenesis of these infections. In this study, the contribution of peritoneal macrophages during E. faecium peritonitis was investigated. In an ex vivo setting, peritoneal macrophages harvested from C57BL/6 mice were responsive to, and able to phagocytose and kill, E. faecium. In vivo, peritoneal macrophages were depleted by intraperitoneal injection of clodronate-encapsulated liposomes, prior to inducing E. faecium peritonitis. Depletion of resident peritoneal macrophages caused a clear delay in peritoneal clearance of E. faecium with increased systemic dissemination. Mice depleted of peritoneal macrophages were able to recruit macrophages and neutrophils to the peritoneal cavity after infection, comparable to control mice. Furthermore, increased levels of peritoneal cytokines and chemokines were found in mice depleted of peritoneal macrophages. This study indicates that peritoneal macrophages are important in the early containment of E. faecium peritonitis and for the regulation of the inflammatory response.

Abdominal surgical interventions: local and systemic consequences for the immune system--a prospective study on elective gastrointestinal surgery

BACKGROUND

Little is known about the local accumulation and function of immune cells in peritoneal fluid after elective surgery of the upper and lower gastrointestinal tract. Our study was designed to investigate whether systemic immune cell response mirrors the local response. We focused on the cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha and on monocytes, natural killer (NK) cells, and T cells that play an important role in eliciting the innate and adaptive immune response.

METHODS

Blood samples were taken prospectively from 25 patients 24 h before surgery, as well as 24 h and 48 h afterward. Abdominal drainage fluids were collected intraoperatively 1 h after the abdomen was opened and 24 h and 48 h postoperatively. Apart from the white blood cells, intracellular T-helper-cell (TH1/TH2) cytokine production (interferon-gamma, IL-2, IL-4, IL-13) and HLA-DR on monocytes were measured by four-color flow cytometry, IL-6, and TNF-alpha with the fast immunoluminescence method.

RESULTS

Cells of the innate immune system (NK cells, monocytes, NK-T cells, CD5(+) B cells) rapidly decreased in abdominal fluids (P < 0.05: +24 h; +48 h) after surgery, which was paralleled by a concomitant decline in peripheral blood. The percentage of abdominal interferon-gamma, IL-2, IL-4, and IL-13-producing TH cells increased in a way that distinctly counteracted the decrease of the natural immune cells. HLA-DR expression on monocytes in peripheral blood declined significantly (P < 0.05: +24 h; +48 h). In contrast, monocytes in abdominal fluids had high HLA-DR expression. Furthermore, abdominal fluids contained significantly higher concentrations of TNF-alpha (P < 0.05: +24 h; +48 h) and IL-6 (P < 0.05: +24 h) compared with peripheral blood.

CONCLUSIONS

Specific immune cell recruitment and cytokine production play an important role in post-trauma events. Measuring distinct local immune cell repertoires and cytokines provides answers as to how the different phases of postoperative immune events proceed. The evaluation of the local response may provide additional criteria for the evaluation of operative trauma. This knowledge may be helpful in detecting postoperative pathological aberrancies.

Suppression of peritoneal implantation of gastric cancer cells by adenovirus vector-mediated NK4 expression

Peritoneal dissemination is the most common mode of metastasis in gastric cancer. We previously reported the importance of milky spots (MS), peritoneal lymphoid tissues, as selective sites of cancer implantation in peritoneal dissemination. In the present study, we first demonstrated that intraperitoneal injection of adenovirus vector encoding the GFP gene into tumor-free nude mice resulted in GFP expression at omental and mesenteric MS; MS macrophages were target cells for adenovirus infection. We confirmed that intraperitoneal injection of adenovirus vector encoding the NK4 gene (AdNK4) resulted in NK4 production localized to the peritoneal cavity, especially the omentum. Adenovirus vector-mediated MS-selective transgene expression was markedly impaired in tumor-bearing mice whose MS had already been replaced by infiltrating cancer cells. However, prior injection of AdNK4 successfully inhibited MS-selective cancer cell implantation, resulting in suppression of peritoneal dissemination and prolongation of survival. Adenovirus vector-mediated MS-selective delivery of a therapeutic gene may prevent peritoneal dissemination of gastric cancer.

Intraperitoneal cytokine productions and their relationship to peritoneal sepsis and systemic inflammatory markers in patients with inflammatory bowel disease

PURPOSE

This prospective, blinded study was designed to assess intraperitoneal cytokine productions and their relationship to clinical presentations and systemic inflammatory markers in patients with inflammatory bowel disease.

METHODS

Fifty patients who required abdominal surgery for active inflammatory bowel disease (ulcerative colitis, 27; and Crohn's disease, 23) were investigated. Interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha levels in intraperitoneal fluid (obtained by intraoperative lavage) and plasma were measured by enzyme-linked immunosorbent assay. To compare intraperitoneal cytokine productions between diseases with a different degree of inflammation, intraperitoneal cytokine measurement also was performed for patients who required surgery for colorectal cancer (n = 25) and acute appendicitis (n = 25).

RESULTS

The median intraperitoneal cytokine (interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha) levels were significantly higher in patients with inflammatory bowel disease than in patients with colorectal cancer and acute appendicitis. In patients with inflammatory bowel disease, intraperitoneal cytokine levels were significantly higher in patients with intraperitoneal sepsis (abscess/fistula) than in patients without intraperitoneal sepsis at laparotomy. Intraperitoneal cytokine levels did not correlate with type of disease (ulcerative colitis/Crohn's disease), age, gender, duration of disease before surgery, preoperative medical treatment, and the extent or site of disease. There were no significant correlations between intraperitoneal cytokine levels and the following systemic inflammatory markers: plasma cytokine levels, white blood cell count, platelet count, erythrocyte sedimentation rate, and C-reactive protein levels. Postoperative intraperitoneal septic complications (anastomotic leak/abscess/enterocutaneous fistula) more frequently occurred in patients with higher intraperitoneal cytokine levels.

CONCLUSIONS

Intraperitoneal cytokine productions were greatly elevated in patients with inflammatory bowel disease, and their levels correlated with the presence of intraperitoneal sepsis at laparotomy and development of postoperative intraperitoneal septic complications. Intraperitoneal cytokine levels showed no correlations with systemic inflammatory markers.

PERITONEAL AND SYSTEMIC INFLAMMATORY MEDIATORS OF LAPAROSCOPIC BOWEL INJURY IN A RABBIT MODEL

PURPOSE

Unrecognized bowel injury following laparoscopy has a subtle and delayed clinical presentation compared with that after open surgery. We determined peritoneal and systemic immune function in laparoscopic and open bowel injury cases. We propose that laparoscopy does not activate immune responses to the same extent as open surgery.

MATERIALS AND METHODS

A total of 40 rabbits were divided into 4 groups. Two study groups were subjected to laparoscopic and open bowel injury, and 2 control groups underwent pneumoperitoneum and sham open surgery, respectively, without bowel injury. Animals were sacrificed 1 day, 3 days and 1 week postoperatively. Macroscopic and histological findings were analyzed. Peritoneal fluid, systemic white blood count (WBC) and differentials were done with a hemocytometer. Peritoneal fluid and serum interleukin (IL)-8 concentrations were measured by enzyme-linked immunosorbent assay.

RESULTS

Macroscopic and histological findings were indistinguishable in the 2 study groups. However, study groups demonstrated higher peritoneal WBCs than their respective controls at 1 and 3 days (p <0.05). Peritoneal WBC was lower in the laparoscopy than in the open study group at 3 days (p <0.05). There was a significant decrease in peritoneal lymphocytes and monocytes in the laparoscopic vs the open study group at 3 days. No differences were found in systemic WBC or differentials among all groups. Peritoneal IL-8 concentrations were higher in the laparoscopic bowel injury than in the laparoscopic control group at 1 and 3 days (p <0.05). However, there were no differences in peritoneal or serum IL-8 concentrations between both study groups.

CONCLUSIONS

Laparoscopic surgery seems to be unable to sustain peritoneal immune responses, which may mask reliable clinical signs and symptoms of peritonitis associated with bowel injury.

Pneumoperitoneum and peritoneal surface changes: a review

BACKGROUND

Recent evidence suggests that the use of carbon dioxide to create a pneumoperitoneum during laparoscopy can lead to adverse structural, metabolic, and immune derangements within the peritoneal cavity, and that these can be dependent on the specific insufflation gas used. These changes include structural alterations in the mesothelial lining, pH disturbances, and alterations in peritoneal macrophage responsiveness. This contrasts with an apparent systemic benefit associated with laparoscopic, as compared with open, surgery.

METHODS

Recently published clinical and experimental studies related to the effect of pneumoperitoneum on the peritoneal surface are reviewed, and their relevance is discussed.

RESULTS

Structural changes in the peritoneal mesothelial surface layer such as widening of the intercellular junctions can be demonstrated with electron microscopy. Acidification of the peritoneum in response to carbon dioxide insufflation occurs not only at the peritoneal surface, but also in the underlying connective tissue, resulting in disturbances in the electrical surface charge and the release of various immune mediators such as endotoxin. Pneumoperitoneum also affects the local peritoneal immune environment resulting in alterations in cytokine production and phagocytic function, as well as diminished antitumor cell cytotoxicity.

CONCLUSIONS

Ultrastructural, metabolic, and immune alterations are observed at the peritoneal surface in response to a pneumoperitoneum. Experimental evidence suggests that these changes are carbon dioxide-specific effects. The consequences of these alterations to the local peritoneal environment are not well understood, but they may facilitate tumor implantation within the peritoneal cavity and adversely affect the ability to clear intraperitoneal infections. Further investigation into this area is warranted.

Laparoscopic port-site metastases: etiology and prevention

OBJECTIVE

The purpose of this article is to summarize current hypotheses for the possible sources of laparoscopic port-site metastasis, to review the results of experimental models that support such hypotheses, and to discuss the potential options for preventing these metastases.

METHODS

We performed a Medline search to identify in vitro and in vivo studies and clinical trials that analyzed port-site metastases associated with laparoscopic surgery. We report the incidence of port-site metastases and causative factors associated with this condition.

RESULTS

The estimated incidence of port-site metastases in all patients undergoing laparoscopic surgery for malignant disease is approximately 1-2%. Multiple factors are associated with this complication. Among the most common proposed etiologies are the wound implantations caused by the surgical technique and instrumentation; the leakage of insufflation gas through the ports, known as the "chimney effect"; and the impact of pneumoperitoneum on local immune reactions. Several preventive measures, have been suggested, including careful patient selection, lavage of the peritoneal cavity as well as of the port wounds with cytotoxic agents, and modifications of surgical technique.

CONCLUSIONS

Only through the results of well-conducted large multi-institutional prospective randomized trials will we learn not only the true incidence of port-site metastases, but also the potential factors that lead to the occurrence of this complication.

Role of peritoneal mesothelial cells in peritonitis

Background

Peritoneal mesothelial cells have a remarkable capacity to respond to peritoneal insults. They generate an intense biological response and play an important role in the formation of adhesions. This review describes these activities and comments on their relationship to surgical drainage, peritoneal lavage and laparostomy in the management of patients with peritonitis.

Methods and results

Material was identified from previous review articles, references cited in original papers and a Medline search of the literature. The peritoneal mesothelium adapts to peritonitis by facilitating the clearance of contaminated fluid from the peritoneal cavity and inducing the formation of fibrinous adhesions that support the localization of contaminants. In addition, the fluid within the peritoneal cavity is a battleground in which effector mechanisms generated with the involvement of peritoneal mesothelial cells meet the contaminants. The result is a complex mix of cascading processes that have evolved to protect life in the absence of surgery.

Conclusion

Future advances in the management of patients with severe peritonitis may depend upon molecular strategies that modify the activity of peritoneal mesothelial cells.

Granulocyte colony-stimulating factor but not peritoneal lavage increases survival rate after experimental abdominal contamination and infection

BACKGROUND

The value of peritoneal lavage for intra-abdominal contamination and infection has never been proven scientifically. In contrast, the stimulation of host defence mechanisms with cytokines such as granulocyte colony-stimulating factor (G-CSF) has appeared promising in recent clinical trials.

METHODS

Clinic modelling randomized trials (CMRTs), which model the complexity of the clinical reality, were used in rats in which peritoneal contamination and infection (PCI) was produced with human stool bacteria. The following groups were compared: trial 1, intraoperative peritoneal lavage with saline versus taurolin (18 rats per group); trial 2, no lavage versus saline lavage versus saline lavage plus subcutaneous administration of G-CSF (18 rats per group); trial 3, lavage with saline versus no lavage (30 rats per group). The primary endpoint was mortality at 120 h. Secondary endpoints were the phagocytic activity of granulocytes, and systemic and peritoneal cytokine levels.

RESULTS

In trial 1 lavage with taurolin was not superior to that with saline (five of 18 versus eight of 18 animals survived; P = 0.32). In trial 2, six of 18 animals having no lavage and three of 18 receiving saline lavage survived. The combination of lavage and G-CSF increased the number of animals surviving to 11 of 18 (P < 0.05). Lavage combined with G-CSF stimulated granulocyte phagocytic activity (P < 0.01) and reduced the levels of interleukin (IL) 6 (P < 0.01) and tumour necrosis factor alpha (P < 0.05) in peritoneal fluid, as well as plasma levels of IL-6 (P < 0.05) and IL-10 (P < 0.01). In trial 3, survival was not significantly different in animals having lavage (14 of 30) and no lavage (19 of 30) (P = 0.14).

CONCLUSION

In these CMRTs of intra-abdominal contamination and infection, peritoneal lavage was not beneficial, but when lavage was combined with subcutaneous administration of G-CSF mortality was reduced and the local and systemic cytokine response was downgraded. Results from these CMRTs were used directly to define the trial conditions of a randomized clinical trial with G-CSF. Peritoneal lavage is not recommended.

Potential involvement of hemoglobin and heme in the pathogenesis of peritoneal endometriosis

OBJECTIVE

To test whether hemoglobin may accumulate in the peritoneal cavity in case of endometriosis and to assess whether heme oxygenases (HO), detoxifying heme, are expressed in ectopic endometrium and peritoneal cells.

DESIGN

Prospective study involving patients with and without endometriosis.

SETTING

Department of gynecology in a university hospital.

PATIENT(S)

Seventy-six patients undergoing laparoscopy for tubal sterilization or infertility and/or pelvic pain.

INTERVENTION(S)

Collection of peritoneal fluid (PF), blood samples, and biopsies from endometrium and peritoneum.

MAIN OUTCOME MEASURE(S)

Measurement of free hemoglobin and its byproduct, total and direct bilirubin, in serum and PF and analysis of HO-1 and HO-2 expression in biopsies by reverse transcription polymerase chain reaction and semiquantitative immunohistochemistry.

RESULT(S)

Higher levels of hemoglobin were found in the PF of patients with endometriosis. There was no concomitant increase in bilirubin concentrations in the PF, and HO-1 was poorly expressed in peritoneal mesothelium and macrophages. Heme oxygenase-1 and HO-2 were strongly expressed in ectopic endometrium, especially in red lesions.

CONCLUSION(S)

Our results suggest that heme may be involved in the pathogenesis and/or development of endometriosis and that the HO system, although expressed, might be insufficient to detoxify heme in women with endometriosis.

Laparoscopic surgery and surgical infection

Laparoscopic surgery (LS) has improved our knowledge of some aspects of surgical physiopathology. Other advantages include a lower incidence of postoperative infections, as evidenced by a lower inflammatory response which is related to a better preserved immune response to infection. But, the differential aspects of LS may influence the intraperitoneal environment and, in case of infection, must be evaluated in two different situations: during clean and potentially-contaminated surgery or in the presence of established infection. The most important differential factors of LS are the pneumoperitoneum and the use of CO2. The influence of both these on the evolution of an intraperitoneal infecton has been of interest in recent years. Our department developed an experimental study with mice to evaluate the local and systemic inflammatory response to perioperative intra-abdominal contamination with a known inoculum of Escherichia coli. The animals were distributed in four groups: control, laparotomy, laparoscopy with CO2 pneumoperitoneum, and laparoscopy with wall traction. Peritoneal liquid and blood cultures such as peritoneal and systemic cytokine levels were analyzed. The results showed a better tolerance to perioperative contamination in LS groups while the CO2 pneumoperitoneum had no influence. But, in the presence of peritonitis, an elevated CO2 pneumoperitoneum can be dangerous and the operative time is an important factor to be considered. The literature is reviewed on the relationship between LS and surgical infection.

Differential responses of rat alveolar and peritoneal macrophages to man-made vitreous fibers in vitro

Different approaches, including inhalation and intraperitoneal injection assays, have been used to assess the potential health effects of man-made vitreous fibers (MMVF). The purpose of this study was to compare the phagocytic activity and the formation of reactive oxygen species by rat alveolar macrophages (AM) and peritoneal macrophages (PM) upon exposure to MMVF10 glass wool and MMVF21 rock wool fibers. Macrophage (Mphi) phagocytosis of mineral fibers was assessed by optical videomicroscopy and computer-aided image analysis. Mphi were classified as cells not associated with fibers, cells with attached fibers, cells with incompletely phagocytized fibers (an appearance known as "frustrated phagocytosis"), and cells with completely phagocytized fibers. The production of superoxide anions by AM and PM upon incubation with MMVF10 and MMVF21 fibers was determined by the superoxide dismutase-inhibitable reduction of ferricytochrome C. PM were found to have a lower phagocytic activity than AM. A significantly higher percentage of AM than of PM underwent frustrated phagocytosis of MMVF10 and MMVF21 fibers. In line with these findings, AM generated higher levels of oxygen radicals than PM upon exposure to MMVF21 fibers. In contrast, MMVF10 fibers failed to induce the generation of reactive oxygen species by both AM and PM. Our in vitro results show that the phagocytic activity, in particular the frustrated phagocytosis of mineral fibers, was significantly lower in PM than in AM. The data support the idea that the durability and biopersistence of mineral fibers are higher in the peritoneal cavity than in the lung.