The Peritoneum: Anatomy, Pathologic Findings, and Patterns of Disease Spread

Disease spread in the abdomen and pelvis generally occurs in a predictable pattern in relation to anatomic landmarks and fascial planes. Anatomically, the abdominopelvic cavity is subdivided into several smaller spaces or compartments by key ligaments and fascial planes. The abdominal cavity has been traditionally divided into peritoneal, retroperitoneal, and pelvic extraperitoneal spaces. Recently, more clinically relevant classifications have evolved. Many pathologic conditions affect the abdominal cavity, including traumatic, inflammatory, infectious, and neoplastic processes. These abnormalities can extend beyond their sites of origin through various pathways. Identifying the origin of a disease process is the first step in formulating a differential diagnosis and ultimately reaching a final diagnosis. Pathologic conditions differ in terms of pathways of disease spread. For example, simple fluid tracks along fascial planes, respecting anatomic boundaries, while fluid from acute necrotizing pancreatitis can destroy fascial planes, resulting in transfascial spread without regard for anatomic landmarks. Furthermore, neoplastic processes can spread through multiple pathways, with a propensity for spread to noncontiguous sites. When the origin of a disease process is not readily apparent, recognizing the spread pattern can allow the radiologist to work backward and ultimately arrive at the site or source of pathogenesis. As such, a cohesive understanding of the peritoneal anatomy, the typical organ or site of origin for a disease process, and the corresponding pattern of disease spread is critical not only for initial diagnosis but also for establishing a road map for staging, anticipating further disease spread, guiding search patterns and report checklists, determining prognosis, and tailoring appropriate follow-up imaging studies. ©RSNA, 2024 Supplemental material is available for this article.

Retroperitoneum revisited: a review of radiological literature and updated concept of retroperitoneal fascial anatomy with imaging features and correlating anatomy

PURPOSE

Spread of disease in the retroperitoneum is dictated by the complex anatomy of retroperitoneal fasciae and is still incompletely understood. Conflicting reports have led to insufficient and incorrect anatomical concepts in radiological literature.

METHODS

This review will discuss previous concepts prevalent in radiological literature and their shortcomings will be highlighted. New insights from recent anatomical and embryological research, together with imaging examples, will be used to clarify patterns of disease spread in the retroperitoneum that remain unexplained by these concepts.

RESULTS

The fusion fascia and the renal fascia in particular give rise to planes and spaces that act as vectors for spread of disease in the retroperitoneum. Some of these planes and structures, such as the caudal extension of the renal fascia, have previously not been described in radiological literature.

CONCLUSION

New insights, including the various fasciae, potential spaces and planes, are incorporated into an updated combined retroperitoneal fascial concept.

Navigating the labyrinth of peritoneal and extraperitoneal anatomy: abdominal spread made easy with a case based review

Essential to understanding disease spread in abdomen is to separate the peritoneum from the extraperitoneum. These areas have distinct anatomy with well-define separate pathways. The peritoneum is comprised of connected recesses that are potential spaces, normally not imaged except when containing excess fluid or air. Peritoneal recesses are formed by the opposing peritoneal surfaces and subdivided by the attachments of the ligaments and mesenteries to the parietal peritoneum. Disease flows within the recesses by changes in abdominal pressure. This forms a distinct spread pattern. The extraperitoneum is traditionally stratified by the renal fascia into the anterior and posterior pararenal spaces and the perirenal space. The fascia contains and directs spread from the contained organs with the compartments. Each space has a unique spread pattern defined by the containing fascia. The extraperitoneum is connected to the mesenteries and ligaments forming the subperitoneal space. This space interconnects the extraperitoneum with the mesenteries allowing for the normal continuum of blood vessels, lymphatics, and nerves but also forms the pathways for bidirectional spread of disease.

Overview of F18-FDG uptake patterns in retroperitoneal pathologies: imaging findings, pitfalls, and artifacts

INTRODUCTION

Retroperitoneum can be the origin of a wide variety of pathologic conditions and potential space for disease spread to other compartments of the abdomen and pelvis. Computed tomography (CT) and magnetic resonance imaging (MRI) are often the initial imaging modalities to evaluate the retroperitoneal pathologies, however given the intrinsic limitations, F18-FDG PET/CT provides additional valuable metabolic information which can change the patient management and clinical outcomes. We highlight the features of retroperitoneal pathologies on F18-FDG PET/CT and the commonly encountered imaging artifacts and pitfalls. The aim of this review is to characterize primary and secondary retroperitoneal pathologies based on their metabolic features, and correlate PET findings with anatomic imaging.

CONCLUSION

Retroperitoneal pathologies can be complex, ranging from oncologic to a spectrum of non-oncologic disorders. While crosse-sectional imaging (CT and MRI) are often the initial imaging modalities to localize and characterize pathologies, metabolic information provided by F18-FDG PET/CT can change the management and clinical outcome in many cases.

Retroperitoneal anatomy with the aid of pathologic fluid: An imaging pictorial review

The retroperitoneum, a complex anatomical space within the abdominopelvic region, encompasses various vital abdominal organs. It is compartmentalized by fascial planes and contains potential spaces critical in multiple disease processes, including inflammatory effusions, hematomas, and neoplastic conditions. A comprehensive understanding of the retroperitoneum and its potential spaces is essential for radiologists in identifying and accurately describing the extent of abdominopelvic disease. This pictorial review aims to describe the anatomy of the retroperitoneum while discussing commonly encountered pathologies within this region. Through a collection of illustrative images, this review will provide radiologists with valuable insights into the retroperitoneum, facilitating their diagnostic proficiency to aid in appropriate patient clinical management.

Primary retroperitoneal squamous cell carcinoma: a literature review

PURPOSE

Retroperitoneal squamous cell carcinoma is an extremely rare histological variant of retroperitoneal tumors. The exact etiology and origin of the same is still unknown. To date, only a few case reports have been published in the literature. Due to rarity, standard treatment protocol is not available. The article aims to review the literature and treatment options available for this uncommon entity, based on available data.

METHODS

We searched the databases like PubMed, PubMed Central, Scopus, and Google Scholar with the keywords "Squamous cell carcinoma" and "retroperitoneal tumors". Peer-reviewed and recent articles were screened.

RESULTS

Seven relevant articles comprising 14 cases were found. Due to the small number of reports, tabulation of treatment details and outcome was done. Like the sarcoma variant, these tumors also present with a large mass in the abdomen and abdominal discomfort. Association with human papillomavirus appears to be the most common factor that gives rise to squamous histology.

CONCLUSION

Retroperitoneal SCC is an uncommonly diagnosed entity. Although no specific treatment guidelines exist for this uncommon malignancy; surgery followed by adjuvant or definitive radiotherapy with concurrent chemotherapy (in inoperable cases) seems a feasible option. Multicentre trials should be conducted for establishing definitive treatment strategies for this ailment.

Unravelling Peritoneal Carcinomatosis Using Cross-Sectional Imaging Modalities

Peritoneal carcinomatosis (PC) refers to malignant epithelial cells that spread to the peritoneum, principally from abdominal malignancies. Until recently, PC prognosis has been considered ill-fated, with palliative therapies serving as the only treatment option. New locoregional treatments are changing the outcome of PC, and imaging modalities have a critical role in early diagnosis and disease staging, determining treatment decision making strategies. The aim of this review is to provide a practical approach for detecting and characterizing peritoneal deposits in cross-sectional imaging modalities, taking into account their appearances, including the secondary complications, the anatomical characteristics of the peritoneal cavity, together with the differential diagnosis with other benign and malignant peritoneal conditions. Among the cross-sectional imaging modalities, computed tomography (CT) is widely available and fast; however, magnetic resonance (MR) performs better in terms of sensitivity (92% vs. 68%), due to its higher contrast resolution. The appearance of peritoneal deposits on CT and MR mainly depends on the primary tumour histology; in case of unknown primary tumour (3-5% of cases), their behaviour at imaging may provide insights into the tumour origin. The timepoint of tumour evolution, previous or ongoing treatments, and the peritoneal spaces in which they occur also play an important role in determining the appearance of peritoneal deposits. Thus, knowledge of peritoneal anatomy and fluid circulation is essential in the detection and characterisation of peritoneal deposits. Several benign and malignant conditions show similar imaging features that overlap those of PC, making differential diagnosis challenging. Knowledge of peritoneal anatomy and primary tumour histology is crucial, but one must also consider clinical history, laboratory findings, and previous imaging examinations to achieve a correct diagnosis. In conclusion, to correctly diagnose PC in cross-sectional imaging modalities, knowledge of peritoneal anatomy and peritoneal fluid flow characteristics are mandatory. Peritoneal deposit features reflect the primary tumour characteristics, and this specificity may be helpful in its identification when it is unknown. Moreover, several benign and malignant peritoneal conditions may mimic PC, which need to be considered even in oncologic patients.

Intraperitoneal anatomy with the aid of pathologic fluid and gas: An imaging pictorial review

The peritoneum is a large serosal membrane enveloping the abdomen and pelvic organs and forming the peritoneal cavity. This complex relationship forms many named abdominopelvic spaces, which are frequently involved in infectious, inflammatory, neoplastic, and traumatic pathologies. The knowledge of this anatomy is essential to the radiologist to localize and describe the extent of the disease accurately. This manuscript provides a comprehensive pictorial review of the peritoneal anatomy to describe pathologic fluid and gas.

"Flexures and bends of the large intestine: Current terminology and a suggestion to simplify it"

There are a number of inconsistencies in the description of the bends of the colon down to the anus. This is historically based on the fact that anatomists saw the colon in its position in the abdominal cavity down to the pelvis and thus from the "outside" and also described it in this way. This view is still useful in clinical practice today (e.g. for the abdominal surgeons). For the greater part of clinicians, however, the view has shifted due to modern endoscopy. This allows examiners to see the terminal section of the intestine and the colon from the "inside". To accommodate both "ways of looking" in terms of modern medicine, we have been guided by today's clinical needs, and here we attempt to reconcile these with the historically evolved anatomical terms to create a nomenclature that meets all the needs of students, anatomists and clinicians looking at the large intestine from the inside and outside. With this in mind, we propose to speak of colic flexures (right colic flexure = RCF = hepatic flexure, flexura coli sinistra; left colic flexure = LCF = splenic flexure, flexura coli dextra; descending-sigmoid flexure = DSF; sigmoid-rectum flexure = SRF) for the colon (colon). For the rectum (rectum), we suggest the term bend (superior, intermediate and inferior) when viewed in the frontal plane, the term curvature (sacral curvature; anorectal curvature = perineal curvature) when viewed in the sagittal plane.

The presence of intraperitoneal, retroperitoneal and pleural fluid in acute Puumala hantavirus infection

BACKGROUND

Puumala hantavirus (PUUV) causes most cases of haemorrhagic fever with renal syndrome (HFRS) in Europe. PUUV infection is characterised by acute kidney injury, thrombocytopenia and increased capillary leakage. Typical symptoms are fever, headache, nausea, abdominal and back pain. This study aimed to evaluate the amount and distribution of intraperitoneal, retroperitoneal and pleural fluid and the association of fluid collections to the symptoms and clinical findings in patients with acute PUUV infection.

METHODS

Abdominal magnetic resonance imaging (MRI) was performed on 27 hospitalised patients with acute PUUV infection. The clinical and laboratory findings and patients' symptoms were analysed in relation to the imaging findings. The thickness of the fluid collections was measured in millimetres (mm) from axial images.

RESULTS

Fluid collections were found in all patients. The amount of intraperitoneal fluid correlated positively with plasma C-reactive protein (CRP) level (r = 0.586, p = .001), while it had an inverse correlation with serum creatinine concentration (r = -0.418, p = .030). Retroperitoneal fluid also correlated inversely with serum creatinine and cystatin C concentrations (r = -0.501, p = .008 and r = -0.383, p = .048, respectively). The amount of fluid was not greater in patients with abdominal or back pain. Patients with back pain had higher serum creatinine compared with patients without back pain, 452 µmol/L (range 88-1071) vs. 83 µmol/L (range 60-679), p = .004.

CONCLUSIONS

Fluid collections were found in all patients. A greater amount of intraperitoneal fluid associates with higher CRP concentrations but not with higher serum creatinine levels. Back pain associates with higher creatinine level but not with the presence of fluids.

Wandering liver, spleen, and kidney: what the radiologist needs to know

The wandering spleen, wandering liver, and wandering kidney are rare diagnoses that can be asymptomatic or are associated with nonspecific symptoms, making the clinical diagnosis elusive. In addition, given the small number of cases, these conditions are not well understood. Major complications of wandering spleen result from torsion of the vascular pedicle with resultant ischemia, physiologic dysfunction, and/or infarction. Wandering liver is commonly associated with bowel obstruction, particularly colonic volvulus, with very rare reports of hepatic ischemia or infarct. Wandering kidneys are not commonly associated with serious complications. In many cases, the wandering spleen, liver or kidney can be found in their anatomic position on static imaging and are only diagnosed during ultrasound or with serial radiographic or cross-sectional imaging with different patient positioning, or with prior studies demonstrating different locations of the involved organ. Treatment approaches for uncomplicated wandering spleen, liver, or kidney include watchful waiting and splenopexy, hepatopexy, or nephropexy, respectively. Complicated wandering spleens are treated with splenectomy. Given the variable clinical presentation of these conditions, imaging plays a pivotal role in diagnosing these rare and often incidentally discovered phenomena.

Morrison's Pouch: Anatomy and Radiological Appearance of Pathological Processes

Morrison's pouch is the intraperitoneal space in the supramesocolic compartment located between the right liver lobe and right kidney. Pathological conditions that can involve this peritoneal space include fluid collections, infectious or inflammatory processes, and neoplasms. Frequent involvement by disease entities can be attributed to its dependent location, communication with the inframesocolic compartment, close proximity to the adjacent organs and peritoneal fluid dynamics. Knowledge of the appearance of pathological entities on various imaging modalities helps the radiologist in making the correct diagnosis.

Is MDCT an accurate tool to differentiate between benign and malignant etiology in diffuse peritoneal disease?

PURPOSE

There is often considerable overlap of imaging findings in benign and malignant peritoneal diseases. We evaluated patients with diffuse peritoneal disease, to assess the diagnostic value of MDCT in predicting benign or malignant etiology in patients with unknown etiology, by analyzing the various patterns of involvement, particularly tuberculosis (TB) vs malignancy.

METHODS

One hundred and thirty-six patients with diffuse peritoneal disease who had abdominal CT and subsequently underwent omental biopsies were included in the study. Peritoneal, mesenteric and omental involvement by disease was evaluated on CT using specific parameters. The presence of lymphadenopathy, ascites, scalloping of organs, involvement of liver and spleen, were also compared between benign and malignant conditions using histopathology as the gold standard.

RESULTS

In 136 patients, 72 benign and 64 malignant pathologies were classified as per histopathology. Higher age (p < 0.001), increasing omental thickness (mean 25.2 mm, p = 0.004), omental caking (p < 0.001), > 10 mm mesenteric/peritoneal nodules (p < 0.03), visceral scalloping (p = 0.001), free ascites (p = 0.003), serosal involvement (p = 0.004) and bilateral pleural effusion (p = 0.02) were associated with malignant etiology. Mesenteric thickening/stranding (p = 0.02), mesenteric adenopathy (p < 0.001), necrotic nodes (p = 0.02), splenomegaly (p =  < 0.001) and higher attenuation (> 20HU) of ascitic fluid (p < 0.001) were associated with benign etiology. The presence of mesenteric thickening or stranding (p = 0.01), splenomegaly (p = 0.02), higher ascitic fluid attenuation > 20HU (p =  < 0.01), mesenteric adenopathy (p < 0.01), necrotic nodes (p = 0.03) favored tuberculosis. CT had diagnostic accuracy (79.3, 86.7%), sensitivity (79.2, 74.6%) and specificity (79.4, 97%) for observers 1 and 2, respectively (Kappa 0.713).

CONCLUSION

Contrast-enhanced MDCT has good sensitivity, specificity and accuracy in differentiating benign and malignant etiologies of diffuse peritoneal disease. Multiple common parameters can be used to differentiate between tuberculous peritonitis and peritoneal carcinomatosis.

CT imaging features of fat stranding in cats and dogs with abdominal disorder

BACKGROUND

Fat stranding is a non-specific finding of an increased fat attenuation on computed tomography (CT) images. Fat stranding is used for detecting the underlying lesion in humans.

OBJECTIVES

To assess the clinical significance of fat stranding on CT images for identifying the underlying cause in dogs and cats.

METHODS

In this retrospective study, the incidence, location, extent, distribution, and pattern of fat stranding were assessed on CT studies obtained from 134 cases.

RESULTS

Fat stranding was found in 38% (51/134) of all cases and in 35% (37/107) of tumors, which was significantly higher in malignant tumors (44%) than benign tumors (12%). Moreover, fat stranding was found in more than two areas in malignant tumors (16/33) and in a single area in benign tumors (4/4). In inflammation, fat stranding was demonstrated in 54% (7/13) in a single area (7/7) as a focal distribution (6/7). In trauma, fat stranding was revealed in 50% (7/14) and most were in multiple areas (6/7). Regardless of the etiologies, fat stranding was always around the underlying lesion and a reticular pattern was the most common presentation. Logistic regression analysis revealed that multiple areas (p = 0.040) of fat stranding and a reticulonodular pattern (p = 0.022) are the significant predictors of malignant tumor.

CONCLUSIONS

These findings indicated that CT fat stranding can be used as a clue for identifying the underlying lesion and can be useful for narrowing the differential list based on the extent and pattern.

Ovarian cancer reporting lexicon for computed tomography (CT) and magnetic resonance (MR) imaging developed by the SAR Uterine and Ovarian Cancer Disease-Focused Panel and the ESUR Female Pelvic Imaging Working Group

OBJECTIVES

Imaging evaluation is an essential part of treatment planning for patients with ovarian cancer. Variation in the terminology used for describing ovarian cancer on computed tomography (CT) and magnetic resonance (MR) imaging can lead to ambiguity and inconsistency in clinical radiology reports. The aim of this collaborative project between Society of Abdominal Radiology (SAR) Uterine and Ovarian Cancer (UOC) Disease-focused Panel (DFP) and the European Society of Uroradiology (ESUR) Female Pelvic Imaging (FPI) Working Group was to develop an ovarian cancer reporting lexicon for CT and MR imaging.

METHODS

Twenty-one members of the SAR UOC DFP and ESUR FPI working group, one radiology clinical fellow, and two gynecologic oncology surgeons formed the Ovarian Cancer Reporting Lexicon Committee. Two attending radiologist members of the committee prepared a preliminary list of imaging terms that was sent as an online survey to 173 radiologists and gynecologic oncologic physicians, of whom 67 responded to the survey. The committee reviewed these responses to create a final consensus list of lexicon terms.

RESULTS

An ovarian cancer reporting lexicon was created for CT and MR Imaging. This consensus-based lexicon has 6 major categories of terms: general, adnexal lesion-specific, peritoneal carcinomatosis-specific, lymph node-specific, metastatic disease -specific, and fluid-specific.

CONCLUSIONS

This lexicon for CT and MR imaging evaluation of ovarian cancer patients has the capacity to improve the clarity and consistency of reporting disease sites seen on imaging.

KEY POINTS

• This reporting lexicon for CT and MR imaging provides a list of consensus-based, standardized terms and definitions for reporting sites of ovarian cancer on imaging at initial diagnosis or follow-up. • Use of standardized terms and morphologic imaging descriptors can help improve interdisciplinary communication of disease extent and facilitate optimal patient management. • The radiologists should identify and communicate areas of disease, including difficult to resect or potentially unresectable disease that may limit the ability to achieve optimal resection.

Abdominal CT findings in Puumala hantavirus-infected patients

BACKGROUND

Previous clinical studies have reported abdominal findings on ultrasonography or MRI in Puumala hantavirus-infected patients.

PURPOSE

To determine if abdominal computed tomography (CT) can lead to a diagnosis of Puumala virus infection in the presence of a suggestive clinical picture.

MATERIAL AND METHODS

CT findings were studied retrospectively in 30 patients who presented to the emergency department of two (Belgian) hospitals with serologically confirmed Puumala hantavirus infection.

RESULTS

The most frequent finding was perirenal fascial thickening (90%), followed by perirenal fat stranding (87%). Retroperitoneal fat stranding was found in 19 patients (64%) in the perivesical spaces along the fascia of the external iliac vessels with or without involvement of the presacral fat. Half of the patients had pelvic ascites, and pleural fluid was found in 7 of them. The right and left mean pole-to-pole kidney's lengths were respectively 125.7 mm and 127.8 mm in 28 patients.

CONCLUSION

Retroperitoneal fat stranding, perirenal fascial thickening and/or perirenal fat stranding were found in most patients with acute Puumala virus infection who have undergone CT. Although nonspecific, these findings may help to suggest Puumala hantavirus infection in the right clinical settings.

Retroperitoneal Sarcoma Care in 2021

Soft-tissue sarcomas are biologically heterogenous tumors arising from connective tissues with over 100 subtypes. Although sarcomas account for <1% of all adult malignancies, retroperitoneal sarcomas are a distinct subgroup accounting for <10% of all sarcomatous tumors. There have been considerable advancements in the understanding and treatment of retroperitoneal sarcoma in the last decade, with standard treatment consisting of upfront primary surgical resection. The evidence surrounding the addition of radiation therapy remains controversial. There remains no standard with regards to systemic therapy, including immunotherapy. Adjunctive therapy remains largely dictated by expert consensus and preferences at individual centers or participation in clinical trials. In this 2021 review, we detail the anatomical boundaries of the retroperitoneum, clinical characteristics, contemporary standard of care and well as recent advancements in retroperitoneal sarcoma care. Ongoing international collaborations are encouraged to advance our understanding of this complex disease.

Magnetic resonance imaging glossary of findings of pediatric pancreatitis and the revised Atlanta classification

While still uncommon, the incidence of acute pancreatitis in children has been increasing over the last two decades. The Atlanta classification for acute pancreatitis, developed for adults, stratifies cases of acute pancreatitis based on imaging and clinical criteria. This classification scheme allows for standardized use of terminology to facilitate treatment and prognostication. Although US and CT should be used in critical or unstable patients, MRI is an ideal imaging modality in pediatric patients with acute pancreatitis because of its ability to characterize tissue without ionizing radiation. We review MRI examples specific to Atlanta classification terminology in pediatric patients. Chronic pancreatitis has also been increasingly diagnosed in children, and imaging plays a key role in the diagnosis and management of this insidious disease. MRI with magnetic resonance cholangiopancreatography is the optimal modality for assessing the pancreas in a child with known or suspected chronic pancreatitis because it provides tissue characterization and high-contrast imaging of the pancreatic duct without the use of invasive instrumentation or ionizing radiation. We also review and demonstrate accepted MRI findings of chronic pancreatitis.

Peritoneal disease: key imaging findings that help in the differential diagnosis

The peritoneum is a unique serosal membrane, which can be the site of primary tumors and, more commonly, secondary pathologic processes. Peritoneal carcinomatosis is the most common malignant condition to affect the peritoneal cavity, and the radiologist plays an important role in making the diagnosis and assessing the extent of disease, especially in sites that may hinder surgery. In this review, we address the role of the radiologist in the setting of peritoneal pathology, focusing on peritoneal carcinomatosis as this is the predominant malignant process, followed by revising typical imaging findings that can guide the differential diagnosis.We review the most frequent primary and secondary peritoneal tumor and tumor-like lesions, proposing a systemic approach based on clinical history and morphological appearance, namely distinguishing predominantly cystic from solid lesions, both solitary and multiple.

How Useful Is Endoscopic Ultrasound in Differentiating T3/T4a T Stage of Colorectal Cancer: A Prospective Study

Objective

Endoscopic ultrasound (EUS) is an established method for staging of colorectal cancer. Nevertheless, prior assessments of its T stage accuracy have been limited, particularly ambiguity in assessed T3 and T4a stage. This study was to characterize the EUS image features and pay attention to distinguish T3 from T4a T stage.

Methods

A total of 638 patients who prospectively underwent colorectal EUS were recorded. The final diagnoses were compared with the concurrent or follow-up histopathology. Univariate and multivariate logistic regressions were used to assess variation in diagnostic performance with case attributes.

Results

The accuracies of EUS in classifying colorectal cancer for overall, T1, T2, T3, and T4a stages are 73.04, 62.32, 67.46, 71.26, and 83.52%, respectively. With attention to EUS image features, the lesion penetrates the entire wall and locates below the seminal vesicles or cervix is T3 stage. If the lesion locates above clearly-defined space between the anterior rectal wall and the posterior surface of the seminal vesicles or cervix, we identify as T4a stage; However, when located above seminal vesicles or cervix but on the posterior wall of the rectum, the lesion still considers as T3 stage. The tumor location and histological type are associated with inaccuracy T stage.

Conclusions

EUS provides reliable diagnostic accuracy in the colorectal cancer stage. The seminal vesicles and cervix are the important markers to predict infiltration depth for T3/T4a stage. Furthermore, the tumor location, histological type, and EUS image features for each tumor T stage should warrant attention.

The role of cytology as an effective tool in management of omental and peritoneal lesions: Experience of a large health care system

BACKGROUND

The aim of this study is to assess the efficacy of cytology in omental or peritoneal lesions.

METHODS

A retrospective review of the pathology database for cytology cases of peritoneal or omental nodules over a 3-year period (2016-2018) was conducted. The cases consisted of either FNA only (FO); FNA and Core biopsy (FCB) or Touch prep and core biopsy (TCB). Cases were further divided based on the prior history of carcinoma. Concordance rates of cytologic diagnosis with histologic diagnosis were studied.

RESULTS

Out of 104 cytology cases reviewed, 60 (57.7%) had prior history of cancer (PHC) and 44 (42.3%) had no prior history of cancer (NPHC). Of the cases with PHC, 43(71.66%) were recurrence, 10 (16.66%) were second cancer, and 7 (11.66%) were non-neoplastic lesions. Of the cases with NPHC, 38 (86.4%) had a second cancer diagnosis, while 6 (13.6%) were non-neoplastic. For FO only cases, 11 of 35 (31.4%) had follow up and 9 of 11 (81.8%) were concordant. For FCB cases, 6 out of 39 (15.4%) had follow up and 6 (100%) were concordant. For TCB cases, 9 out of 30 (30%) had follow up and 9 (100%) were concordant. A definite diagnosis was reached in 30/35, 39/39, and 29/30 cases in FO, FCB, and TCB, respectively.

CONCLUSION

In summary, cytologic evaluation of omental lesions is an effective tool in providing accurate diagnosis and guiding further management. Also, the results based on our study show that the combined techniques are superior at reaching a definitive diagnosis.

Initial Experience with the Comprehensive Modified Laparoscopic Pyeloplasty Technique Based on Membrane Anatomy for Treating Ureteropelvic Junction Obstruction

OBJECTIVE

The aim of the objective was to present our initial experience and evaluate the feasibility of the novel comprehensive modified laparoscopic pyeloplasty (CMLP) technique based on membrane anatomy.

MATERIALS AND METHODS

Forty-eight patients underwent CMLP from February 2016 to October 2020. CMLP involves the following: dissection of the ureter was based on the fascia or fusion fascia formed by embryonic development. The ureter was separated from the ureteral sheath, and the pelvis and ureter were incised with incomplete amputation. The first stitch was placed between the lower point of the spatulated ureter and the lowest corner of the renal pelvis to ensure correct orientation of the anastomosis; anastomosis of the renal pelvis and ureter was performed using the touchless technique.

RESULTS

All CMLPs were completed successfully without conversion. The mean overall operating time was 230.96 min. The median estimated blood loss was 50.00 (interquartile range 20.00-57.50) mL. The average postoperative hospital stay was 9.31 days. The average follow-up time was 24.73 months. No major complications occurred. In 1 case, revision laparoscopic pyeloplasty was performed, but the obstruction persisted after double J stent removal, so ultimately, the double J stent required regular replacement. Another asymptomatic patient with hydronephrosis experienced failed treatment and is still under follow-up. The overall success rate was 95.83% (46/48). The success rate in patients with recurrent ureteropelvic junction obstruction (UPJO) was 87.5% (7/8).

CONCLUSIONS

CMLP is a practical and effective treatment option for UPJO with a high success rate. An advantage of CMLP is the clear surgical field.

Multidisciplinary Management of Retroperitoneal Sarcoma: Diagnosis, Prognostic Factors and Treatment

Simple Summary

The management of retroperitoneal sarcomas can be challenging due to the variety of their presentation, histopathological types, and behaviours. This literature review provides a comprehensive and practical overview of the management of retroperitoneal sarcomas, focusing on diagnostic challenges, prognostic factors, multidisciplinary aspects of treatment and new research perspectives.

Abstract

Retroperitoneal sarcomas (RPS) are rare cancers whose management can be challenging due to various presentation patterns, multiple organ involvement, and a high local and distant recurrence rate. Histopathology and prognostic factors analysis are essential to predict the behaviour of the disease and plan the best therapeutic strategy. To date, surgery is still the main therapeutic option that guarantees a chance of cure from the primary disease. While chemotherapy and radiotherapy seem to be good options for controlling metastatic and recurrent irresectable disease, their role in the treatment of primary RPS remains unclear. This literature review aims to provide a comprehensive overview of the multidisciplinary aspects of RPS management in high-volume centres, summarising the diagnostic path, the prognostic factors, and the most suitable therapeutic options.

Puncture needle with a hard plastic sheath and plastic wings minimizes repuncture attempts in ultrasound-guided paracentesis

Background

This study was performed to evaluate periprocedural factors, complications, and repuncture rate of the newly developed puncture needle and compare it with the routinely used puncture needle for ultrasound (US)-guided paracentesis.

Methods

We retrospectively identified 137 patients who underwent US-guided paracentesis between July 2018 and March 2019. Among them, 82 patients underwent US-guided paracentesis with a newly developed puncture needle. The other 55 patients underwent US-guided paracentesis with a routinely used puncture needle. The periprocedural factors, complications, and repuncture rate were compared between the two groups using the Mann-Whitney U test and Fisher exact test. The repuncture-associated factors were assessed using logistic regression analysis.

Results

There were no major or minor complications in either group. The rate of repuncture was significantly lower in the group using the newly developed puncture needle compared with the group using the routinely used puncture needle (p=0.01). The duration of the procedure was significantly shorter with the newly developed puncture needle compared with the routinely used puncture needle (p=0.01). In univariate analysis, the thickness of the abdominal wall (p=0.04) and the use of the newly developed puncture needle (p=0.01) were significantly associated with the rate of repuncture. In multivariate analysis, only the use of the newly developed puncture needle was significantly associated with the rate of repuncture.

Conclusion

Using this novel puncture needle with a hard plastic sheath and plastic wings, the rate of repuncture and the duration of the procedure were decreased without complications of US-guided paracentesis.

Radiologic-Pathologic Correlation of Primary Retroperitoneal Neoplasms

An earlier incorrect version of this article appeared in print. The online version is correct.

Update on the Role of Imaging in Clinical Staging and Restaging of Renal Cell Carcinoma Based on the AJCC 8th Edition, From the AJR Special Series on Cancer Staging

This article reviews the essential role of imaging in clinical staging and restaging of renal cell carcinoma (RCC). To completely characterize and stage an indeterminate renal mass, renal CT or MRI without and with IV contrast administration is recommended. The critical items for initial clinical staging of an indeterminate renal mass or of a known RCC according to the TNM staging system are tumor size, renal sinus fat invasion, urinary collecting system invasion, perinephric fat invasion, venous invasion, adrenal gland invasion, invasion of the perirenal (Gerota) fascia, invasion into other adjacent organs, the presence of enlarged or pathologic regional (retroperitoneal) lymph nodes, and the presence of distant metastatic disease. Larger tumor size is associated with higher stage disease and invasiveness, lymph node spread, and distant metastatic disease. Imaging practice guidelines for clinical staging of RCC, as well as the role of renal mass biopsy, are highlighted. Specific findings associated with response of advanced cancer to antiangiogenic therapy and immunotherapy are discussed, as well as limitations of changes in tumor size after targeted therapy. The accurate clinical staging and restaging of RCC using renal CT or MRI provides important prognostic information and helps guide the optimal management of patients with RCC.

Overview of spontaneous intraabdominal tumor hemorrhage: etiologies, imaging findings, and management

Hemorrhage is a potential complication of benign and malignant tumors and tumor-like conditions in the abdomen. Patients often have non-specific presentations, although they may present critically ill and hemodynamically unstable. Imaging plays an important role not only in the diagnosis of hemorrhage but also in the detection and characterization of an underlying mass. Ultrasound, computed tomography, and magnetic resonance imaging are utilized in evaluating these patients, with each having particular strengths and limitations. Spontaneous tumor hemorrhage is most commonly seen in hepatic and renal lesions, although it can arise from nearly every abdominal organ. In this article, we will review principles of tumor hemorrhage, illustrate common and uncommon imaging features, and highlight different options for management.

The contribution of surgical clips for optimizing highly-conformal image-guided flank irradiation in pediatric renal tumors: A single center experience

BACKGROUND AND AIMS

Two-opposing photon beams are considered standard of care for flank irradiation in pediatric patients with renal tumors. Nowadays, Image-Guided Radiotherapy (IGRT) techniques allow high-precision dose delivery to complex flank target volumes taking into account postoperative organ shifts and tumor bed motion. This study examines the contribution of a lateral and superior surgical clip on flank target volume delineation intended for IGRT.

METHODS

Between 01-2015 and 09-2019, 30/162 newly-diagnosed pediatric patients with renal tumors, lateral/superior surgical clips (n = 30/30) and available 4D-CT-scans (n = 27/30), underwent postoperative flank irradiation. The lateral and superior clip, as respective markers for the lateral tumor extension and intrafraction motion, were analyzed. The positive and negative values depict the lateral/dorsal/cranial or the medial/ventral/caudal direction, respectively. Planning target volumes (PTV) were generated based on lateral clips (PTV_latclip), superior clips with 4D-CT technology (PTV_supclip), and both clips combined (PTV_combined), and compared to an approach without clips (PTV_noclip).

RESULTS

Indicated by clips, the mean lateral tumor bed extension along the posterior wall was 74° (range: 50°-93°), while mean intrafraction motion was +1.2 mm (range: -1.8/+4.8 mm), +0.6 mm (range: +0.6/+4.9 mm), -0.3 mm (range: -3.8/+0.7 mm) in craniocaudal, ventrodorsal, mediolateral direction, respectively. The median PTV_noclip (556 mL) was statistically different from the median PTV_latclip (454 mL, p = <0.01), median PTV_supclip (373 mL, p = <0.01) and median PTV_combined (348 mL p = <0.01).

CONCLUSION

In pediatric patients with renal tumors, surgical clips at the lateral and superior border of the tumor bed can optimize flank target volume delineation and, consequently, reduce the normal tissue volume receiving high-dose irradiation when IGRT techniques are applied.

MR Imaging of the Perihepatic Space

The perihepatic space is frequently involved in a spectrum of diseases, including intrahepatic lesions extending to the liver capsule and disease conditions involving adjacent organs extending to the perihepatic space or spreading thanks to the communication from intraperitoneal or extraperitoneal sites through the hepatic ligaments. Lesions resulting from the dissemination of peritoneal processes may also affect the perihepatic space. Here we discuss how to assess the perihepatic origin of a lesion and describe the magnetic resonance imaging (MRI) features of normal structures and fluids that may be abnormally located in the perihepatic space. We then review and illustrate the MRI findings present in cases of perihepatic infectious, tumor-related, and miscellaneous conditions. Finally, we highlight the value of MRI over computed tomography.

Impact of visceral adipose tissue on the accuracy of T-staging by CT in colon cancer

OBJECTIVE

Accuracy of preoperative T-staging for colon cancer remains disappointing and may potentially influenced by patients' individual characteristics including visceral adipose tissue (VAT). We sought to clarify the impact of VAT on the accuracy of T-staging by CT.

METHODS

This study of 216 consecutive patients who underwent elective surgery was conducted in a single cancer center, to control other potentially confounding factors. Patients were divided into accurate- and mis-staging groups according to the comparison between preoperative CT-defined (cT) and postoperative pathologic T-stages (pT). Patients' individual characteristics, including CT-based VAT at L2/L3 level, age, sex, body mass index (BMI), tumor location, present of bowel obstruction and pathologic subtype, were compared between the two groups. Association between VAT and mis-staging was assessed using multivariate logistic regression to adjust for confounders.

RESULTS

Of the 216 patients, 84 (39%) were mis-staged by CT. The mean VAT in accurate-staging group was significantly higher than that in mis-staging group (146.8 ± 66.1 cm² vs 98.1 ± 44.7 cm², P < 0.001), with an optimal cutoff point of 122 cm² for predicting mis-staging. After partial adjustment, a lower VAT (< 122 cm², P < 0.001) and proximal location of tumor (P = 0.004) were independent factors associated with higher probability of mis-staging. Compared to VAT ≥ 122 cm² as the reference, VAT < 122 cm² exhibited an odds ratio of 2.701 (95% confidence intervals [CI], 1.618-3.907) for the probability of mis-staging.

CONCLUSION

A lower-VAT is associated with an increased probability of inaccurate clinical T-staging in colon cancer.

Tumor-mesoporous silica nanoparticle interactions following intraperitoneal delivery for targeting peritoneal metastasis

The use of intraperitoneal administration of nanoparticles has been reported to facilitate higher concentrations of nanoparticles in metastatic peritoneal tumors. While this strategy is appealing for limiting systemic exposure of nanocarrier delivered toxic cargoes and increasing nanoparticle concentrations in avascular peritoneal tumors, little is known about the mechanism of nanoparticle accumulation on tumor tissues and currently, no nanoparticle-based product has been approved for intraperitoneal delivery. Here, we investigated the nanoparticle-specific characteristics that led to increased peritoneal tumor accumulation using MCM-41 type mesoporous silica nanoparticles as our model system. We also investigated the components of the peritoneal tumor stroma that facilitated nanoparticle-tumor interaction. The tumor extracellular matrix is the main factor driving these interactions, specifically the interaction of nanoparticles with collagen. Upon disruption of the collagen matrix, nanoparticle accumulation was reduced by 50%. It is also notable that the incorporation of targeting ligands did not increase overall tumor accumulation in vivo while it significantly increased nanoparticle accumulation in vitro. The use of other particle chemistries did not grossly affect the tumor targetability, but additional concerns arose when those tested particles exhibited significant systemic exposure. Mesoporous silica nanoparticles are advantageous for intraperitoneal administration for the treatment of peritoneal metastasis due to their physical stability, tumor targetability, strong interaction with the collagen matrix, and extended peritoneal residence time. Maximizing nanoparticle interaction with the tumor extracellular matrix is critical for developing strategies to deliver emerging therapeutics for peritoneal cancer treatment using nanocarriers.

Mesentery - a 'New' organ

The mesentery is the organ in which all abdominal digestive organs develop, and which maintains these in systemic continuity in adulthood. Interest in the mesentery was rekindled by advancements of Heald and Hohenberger in colorectal surgery. Conventional descriptions hold there are multiple mesenteries centrally connected to the posterior midline. Recent advances first demonstrated that, distal to the duodenojejunal flexure, the mesentery is a continuous collection of tissues. This observation explained how the small and large intestines are centrally connected, and the anatomy of the associated peritoneal landscape. In turn it prompted recategorisation of the mesentery as an organ. Subsequent work demonstrated the mesentery remains continuous throughout development, and that abdominal digestive organs (i.e. liver, spleen, intestine and pancreas) develop either on, or in it. This relationship is retained into adulthood when abdominal digestive organs are directly connected to the mesentery (i.e. they are 'mesenteric' in embryological origin and anatomical position). Recognition of mesenteric continuity identified the mesenteric model of abdominal anatomy according to which all abdominal abdomino-pelvic organs are organised into either a mesenteric or a non-mesenteric domain. This model explains the positional anatomy of all abdominal digestive organs, and associated vasculature. Moreover, it explains the peritoneal landscape and enables differentiation of peritoneum from the mesentery. Increased scientific focus on the mesentery has identified multiple vital or specialised functions. These vary across time and in anatomical location. The following review demonstrates how recent advances related to the mesentery are re-orientating the study of human biology in general and, by extension, clinical practice.

Update on MR Imaging of cystic retroperitoneal masses

OBJECTIVE

This article reviews the MRI appearance of cystic retroperitoneal (RP) masses.

CONCLUSION

Lymphangiomas are the most common RP cystic masses and typically appear simple; microscopic fat is a specific but insensitive finding. Location, internal complexity, and enhancement pattern suggest alternative diagnoses which range from normal anatomic variants to congenital abnormalities and importantly include benign, neurogenic, and malignant neoplasms. An approach to the MR imaging of cystic RP masses is presented.

The Peritoneum: What Nuclear Radiologists Need to Know

The peritoneum is the largest and most complex serous membrane in the human body. The peritoneal membrane is composed of a layer of mesothelium supported by a thin layer of connective tissue. The peritoneum is one continuous sheet, forming two layers and a potential space between them - the peritoneal cavity- which is subdivided into multiple communicating spaces containing small amount of serous fluid that facilitates frictionless movement of mobile intraabdominal viscera. Peritoneum also contributes to fluid exchange mechanism and plays a role in immune response. The peritoneum is subject to many neoplastic and non-neoplastic processes including infections, trauma, developmental and inflammatory processes. Different Nuclear Medicine imaging techniques can be used to diagnose peritoneal diseases, most of these techniques can be customized depending on the clinical scenario and expected findings. Peritoneal scintigraphy can detect abnormal peritoneal communication or compartmentalization. Several nuclear medicine techniques can help characterize intraperitoneal fluid collections and differentiate sterile from infected fluid. PET imaging plays an important role in imaging of different neoplastic and non-neoplastic peritoneal pathologies. Nuclear radiologists need to be familiar with peritoneal anatomy and pathology to interpret peritoneal findings in dedicated peritoneal nuclear medicine imaging studies, as part of more general nuclear medicine scans, or on CT or MRI component of hybrid imaging studies. The purpose of this article is to review the normal peritoneal anatomy, various pathologic processes involving the peritoneum, and different nuclear medicine and hybrid imaging techniques that can help detect, characterize, and follow up peritoneal pathology.

Pancreatic abscess within hepato-gastric ligament: case report of an extremely rare disease

Background

Pancreatic pseudocyst is a very common benign cystic lesion of the pancreas. It develops in 5–15% of patients with peri-pancreatic fluid collection following acute pancreatitis. Collection usually occurs within the lesser sac of the omentum (near the pancreatic head and body region). But in 20–22% cases, that may be extra-pancreatic like in the mediastinum, pleura, in the peritoneal cavity including the pelvis. The pancreatic pseudocyst typically contains brownish fluid with necrotic tissue sludge which may get infected giving rise to infected pseudocyst or pancreatic abscess. The present case is an unusual condition of a young alcoholic subject who was finally diagnosed as a case of a pancreatic abscess within hepato-gastric ligament and was managed with operative intervention.

To the best of the author’s knowledge, it is the first-ever reported case of a pancreatic abscess within the hepato-gastric ligament in the world. Literature was reviewed to explore potential etiopathogenesis and therapeutic strategies of this extremely rare condition.

Case presentation

A 38 years old gentleman, chronic alcoholic, having a previous history of acute pancreatitis 3 months back, presented with fever (102 degrees Fahrenheit) and a huge [20 cm (horizontal) X 15 cm (vertical)] severely painful swelling in the epigastric region. The swelling was round-shaped, intra-abdominal, fixed to deeper tissue, tense-cystic, poorly trans-illuminant, non-pulsatile and irreducible. Routine blood tests showed leucocytosis (14,500/mm³) with neutrophilia and elevated plasma pancreatic amylase and lipase levels. USG and MDCT scan of the whole abdomen revealed a thick-walled echogenic cystic swelling of size 18 cm × 12 cm in the epigastric region. USG guided aspiration of the cyst revealed mixed purulent brownish fluid. The cyst fluid was negative for mucin stain and contained high amylase level with low CEA level, suggesting infected pancreatic pseudocyst.

An open drainage procedure was considered through an upper midline laparotomy. Aspiration of the pus mixed cyst fluid along with tissue debris was done. Through irrigation of the cyst was done with normal saline. The cyst wall was de-roofed leaving a small part adherent to the inferior surface of the left lobe of the liver. Later the cyst fluid culture showed significant growth of Escherichia coli. He was put on IV antibiotics. The patient was discharged in a stable condition after 5 days. The histopathological examination confirmed pancreatic abscess.

Six months after the operation, the patient is doing well, remaining asymptomatic and there is no sign of recurrence.

Conclusions

Due to extreme rarity, pancreatic abscess formation within hepato-gastric ligament may be a diagnostic dilemma and requires a high index of suspicion. Surgeons should be aware of this rare clinical entity for prompt management of potential morbidity.

Direct Puncture Tunnel Method for Establishing the Retroperitoneal Cavity: Anatomic Confirmation and Clinical Experience

Purpose: The feasibility and safety of the direct puncture tunnel method to establish the retroperitoneal cavity was assessed by CT and clinical experience. Materials and Methods: Ten patients who underwent retroperitoneoscopic procedure were scanned by CT in the lateral decubitus position. The distance between the lumbar fascia and psoas major muscle (L-P distance) on the puncture line was measured. The angle between the puncture line and the posterior colon margin (P-C angle) was also measured. In total, 292 patients who underwent retroperitoneoscopic procedure were used to establish the retroperitoneal cavity using the direct puncture tunnel method, and complications in these patients were evaluated. Results: The average L-P distance was 25.0 mm (left side) and 25.5 mm (right side) in the lateral decubitus position. The average P-C angle was 26.8° (left side) and 29.7° (right side). The retroperitoneal cavity was well established in all 292 patients, and no visceral or blood vessel injury occurred. Conclusions: CT scans in the lateral recumbent position indicate that there are no visceral and large blood vessels on the puncture path. The scans also provide a window for inserting the first trocar blindly into the retroperitoneum. A high success rate and low complication rate were observed clinically for the direct puncture tunnel method. We consider the direct puncture tunnel method to be a simple, effective, and safe way to establish the retroperitoneal cavity.

Detection of Uterine Leiomyosarcoma Peritoneal Lesions by SPECT/CT and ROLL Technique

We reported the preoperative radio-guided localization of 4 peritoneal metastatic nodules in the case of a 45-year-old woman with uterine leiomyosarcoma. Three lines of chemotherapy were tried, but cardiotoxicity occurred. Within the context of so-called GOSTT (guided intraoperative scintigraphic tumor targeting), preoperative radio-guided localization of peritoneal metastases enabled their subsequent radio-guided excisional biopsy. SPECT/CT allowed for anatomical localization of the hot lesions and generated a 3-dimensional volume-rendering roadmap, facilitating a surgical approach.

Imaging of infracolic and pelvic compartment by linear EUS

The peritoneal cavity is subdivided into supracolic and infracolic compartments by transverse mesocolon, which attaches the colon to the posterior abdominal wall. Infracolic compartment is subdivided into right and left compartment by small bowel mesentery. Left infracolic space freely communicates with pelvic compartment. The infracolic compartment contains the coils of small bowel which is separated from paracolic gutter on either side by ascending and descending colon. Pelvic compartment mainly contains bladder, rectum and genital organ (prostate, seminal vesicle in male and uterus in female). The evaluation of different compartments of peritoneum is gaining importance in multimodality imaging. It has become essential that clinicians and endosonographers thoroughly understand the peritoneal spaces and the ligaments and mesenteries that form their boundaries in order to localize disease to a particular peritoneal/subperitoneal space and formulate a differential diagnosis on the basis of that location. In this article we describe the applied EUS anatomy of peritoneal ligaments, infracolic and pelvic compartments of peritoneum and there technique of imaging from stomach, duodenum, sigmoid colon and rectum. Imaging from stomach images the infracolic compartment through transverse mesocolon, imaging from duodenum images the infracolic compartment through the mesentery and imaging from rectum and sigmoid images the infracolic and pelvic compartments through the sigmoid mesocolon and pelvic peritoneum.

[Systematic surgery of retroperitoneal sarcomas : Imaging-guided planning of surgical strategy]

Abdominal and retroperitoneal sarcomas (RPS) represent approximately 25-30% of all soft tissue sarcomas, if besides typical retroperitoneal tumors gastrointestinal stromal tumors (GIST) are also included. The surgical R0 en bloc resection with histopathologically free margins is basically the only potentially curative treatment procedure. When planning the surgical strategy, the histopathological subtype and tumor localization are pivotal. The extent of resection should be guided by the goal to reach an en bloc resection with histopathologically negative margins. Due to the frequently found vast dimensions of RPS and ultimately topographic proximity to vital structures at primary diagnosis, R0 resections are not always achievable. Despite the introduction of multimodal treatment regimens and the development of standardized extended surgical procedures, such as systematic retroperitoneal compartmental resection (SRCR), local recurrences remain the most common cause of tumor-associated death. Finally, the results of the transatlantic RPS working group (TARPSWG) could show that treatment of RPS in specialized high-volume centers contributes to better long-term survival. Particularly in Germany there is an urgent demand for centralization of sarcoma patient treatment.

The hepatoduodenal ligament revisited: cross-sectional imaging spectrum of non-neoplastic conditions

INTRODUCTION

The hepatoduodenal ligament is frequently involved by conditions affecting the portal triad and surrounding structures, including a vast array of non-neoplastic conditions. Due its unique location between the retroperitoneum and the peritoneal space, the hepatoduodenal ligament is also targeted by inflammatory conditions involving the retroperitoneum and the liver. Finally, the presence of lymphatics and of the biliary tracts makes the hepatoduodenal ligament a route of spread for a variety of infections. The purpose of this pictorial essay is twofold: to review the cross-sectional radiological anatomy and variants of the structures within the hepatoduodenal ligament, and to illustrate the non-neoplastic conditions that may arise within the hepatoduodenal ligament.

CONCLUSION

Familiarity with these specific entities and their cross-sectional imaging findings is fundamental for a more accurate diagnosis.

Duodenal obstruction induced by retroperitoneal progression of bladder cancer: a report of two cases

Bladder cancer usually forms a papillary structure. Progression along the cavity or membranous structures surrounding the bladder, rectum, or retroperitoneum without formation of a discrete mass is rare. We here present two patients with duodenal obstruction caused by retroperitoneal progression of bladder cancer, in both of whom computed tomography revealed bladder and rectal wall thickening with a malignant target sign, thickened mesorectal fascia with abnormal tissue stranding, and increased perirectal fat density. Both cancers progressed despite treatment, as indicated by faint abnormal tissue stranding and increased retroperitoneal fat density along the retromesenteric plane from the pelvis to the duodenum. Subsequently, both patients developed obstruction in the horizontal portion of the duodenum, still without formation of a mass lesion. These two patients highlight the challenges associated with retroperitoneal invasion by bladder cancer in the absence of a mass lesion and underscore the importance of considering cancer progression in patients with bowel obstruction, even when there is no obvious mass lesion and/or only minor retroperitoneal findings. Progression along the retromesenteric plane may be the key pathway via which progressive bladder cancer results in duodenal obstruction without or with a minor mass lesion.

Unusual case of extraperitoneal gas in the abdomen

The retroperitoneal space is made up of multiple communicating compartments. Here we detail an unusual case of ectopic gas almost exclusively isolated to the properitoneal space, a space in communication with the retroperitoneum. This case is a reminder that when extraperitoneal gas is identified, the retroperitoneal structures should be interrogated carefully to identify a cause.

Anatomy of the mesentery: Historical development and recent advances

Recent appraisals of mesenteric anatomy clarify its structure and show a continuous and helical-shaped organ. This new model signifies a departure from the conventional model which described multiple, separate "mesenteries". Renaissance anatomists depicted the mesentery as a continuous structure. Events that led to replacement of a continuous with a fragmented model span several centuries. In effect, the scientific and clinical community has come full circle and back to the Renaissance model. Here we review the historical development of our understanding of the mesentery. We discuss how the fragmented model replaced the continuous model. Additionally, we examine factors that contributed to recent advances in mesenteric anatomy as these present new opportunities for systematic investigation.