Intestinal adaptation following jejuno-ileal bypass

Muscle hypertrophy and neuroplasticity in the small bowel in short bowel syndrome

Short bowel syndrome (SBS) is a severe, life-threatening condition and one of the leading causes of intestinal failure in children. Here we were interested in changes in muscle layers and especially in the myenteric plexus of the enteric nervous system (ENS) of the small bowel in the context of intestinal adaptation. Twelve rats underwent a massive resection of the small intestine to induce SBS. Sham laparotomy without small bowel transection was performed in 10 rats. Two weeks after surgery, the remaining jejunum and ileum were harvested and studied. Samples of human small bowel were obtained from patients who underwent resection of small bowel segments due to a medical indication. Morphological changes in the muscle layers and the expression of nestin, a marker for neuronal plasticity, were studied. Following SBS, muscle tissue increases significantly in both parts of the small bowel, i.e., jejunum and ileum. The leading pathophysiological mechanism of these changes is hypertrophy. Additionally, we observed an increased nestin expression in the myenteric plexus in the remaining bowel with SBS. Our human data also showed that in patients with SBS, the proportion of stem cells in the myenteric plexus had risen by more than twofold. Our findings suggest that the ENS is tightly connected to changes in intestinal muscle layers and is critically involved in the process of intestinal adaptation to SBS.

Decreased Expression of KLF4 Leading to Functional Deficit in Pediatric Patients with Intestinal Failure and Potential Therapeutic Strategy Using Decanoic Acid

Pediatric intestinal failure (IF) is the reduction in gut function to below the minimum necessary for the absorption of macronutrients and/or water and electrolytes, such that intravenous supplementation is required to maintain health and/or growth. The overall goal in treating IF is to achieve intestinal adaptation; however, the underlying mechanisms have not been fully understood. In this study, by performing single-cell RNA sequencing in pediatric IF patients, we found that decreased Kruppel-Like Factor 4 (KLF4) may serve as the hub gene responsible for the functional deficit in mature enterocytes in IF patients, leading to the downregulation of solute carrier (SLC) family transporters (e.g., SLC7A9) and, consequently, nutrient malabsorption. We also found that inducible KLF4 was highly sensitive to the loss of certain enteral nutrients: in a rodent model of total parenteral nutrition mimicking the deprivation of enteral nutrition, the expression of KLF4 dramatically decreased only at the tip of the villus and not at the bottom of crypts. By using IF patient-derived intestinal organoids and Caco-2 cells as in vitro models, we demonstrated that the supplementation of decanoic acid (DA) could significantly induce the expression of KLF4 along with SLC6A4 and SLC7A9, suggesting that DA may function as a potential therapeutic strategy to promote cell maturation and functional improvement. In summary, this study provides new insights into the mechanism of intestinal adaptation depending on KLF4, and proposed potential strategies for nutritional management using DA.

Intestinal adaptation and rehabilitation

Massive intestinal resection is a regrettably necessary but life-saving intervention for progressive or fulminant necrotizing enterocolitis (NEC). However, the resultant short bowel syndrome (SBS) poses its own array of challenges and complications. Within hours of such an abrupt loss of intestinal length, the intestine begins to adapt. Our ability to understand this process of intestinal adaptation has proven critical in our ability to clinically treat the challenging problem of short bowel syndrome. This review first highlights key data relating to intestinal adaptation including structural and functional changes, biochemical regulation, and other factors affecting the magnitude of intestinal adaptation responses. We then focus on intestinal rehabilitation as it relates to strategies to enhance intestinal adaptation while meeting nutritional needs and preventing complications of parenteral nutrition.

Anatomical and physiological considerations in short bowel syndrome: Emphasis on intestinal adaptation and the role of enterohormones

Short bowel syndrome (SBS)-associated intestinal failure (IF) is a complex, life-threatening condition that requires complex care of multiple factors impacting the patient's long-term prognosis. Various etiologies result in SBS-IF, with three primary anatomical subtypes occurring following intestinal resection. Depending on the extent and segment(s) of the intestine resected, malabsorption can be nutrient specific or sweeping; however, such issues and the associated prognosis for the patient can be predicted with analysis of the residual intestine, along with baseline nutrient and fluid deficits and extent of malabsorption. The provision of parenteral nutrition/intravenous (PN-IV) fluids and antisymptomatic agents is fundamental; however, optimal management should focus on intestinal rehabilitation, wherein intestinal adaptation is prioritized and PN-IV fluids are weaned over time. Key strategies to maximize intestinal adaptation include hyperphagic consumption of an individualized SBS diet and the appropriate use of trophic agents, such as a glucagon-like peptide 2 analog.

Concise review on short bowel syndrome: Etiology, pathophysiology, and management

Adults have approximately 20 feet of small intestine, which is the primary site for absorbing essential nutrients and water. Resection of the intestine for any medical reason may result in short bowel syndrome (SBS), leading to loss of major absorptive surface area and resulting in various malabsorption and motility disorders. The mainstay of treatment is personalized close dietary management. Here we present SBS with its pathophysiology and different nutritional management options available. The central perspective of this paper is to provide a concise review of SBS and the treatment options available, along with how proper nutrition can solve major dietary issues in SBS and help patients recover faster.

Short Bowel Syndrome in Adults

Short bowel syndrome (SBS) is a rare disorder characterized by severe intestinal dysfunction leading to malabsorption of macronutrients and micronutrients that often results in permanent need of parenteral nutrition support. Patients can develop SBS because of massive intestinal resection or loss of intestinal function and consequently experience significant morbidity and increased healthcare utilization. The remaining anatomy and length of bowel after intestinal resection have important prognostic and therapeutic implications. Because patients with SBS constitute a heterogenous group, management is complex and multifaceted, involving nutrition support, fluid and electrolyte management, and pharmacologic therapies in particular to control diarrhea. Surgical interventions including intestinal transplantation may be considered in selected individuals. Successful care of these patients is best accomplished by a multidisciplinary team that is experienced in the management of this syndrome.

Optimized In Silico Modeling of Drug Absorption after Gastric Bypass: The Case of Metformin

Bariatric surgery is an effective treatment for severe obesity and related comorbidities, such as type II diabetes. Gastric bypass surgery shortens the length of the intestine, possibly leading to altered drug absorption. Metformin, a first-line treatment for type II diabetes, has permeability-dependent drug absorption, which may be sensitive to intestinal anatomic changes during bypass surgery, including Roux-en-Y gastric bypass (RYGB). Previous computer simulation data indicate increased metformin absorption after RYGB. In this study, we experimentally determined the region-dependent permeability of metformin, using the rat single-pass intestinal perfusion method (SPIP), which we then implemented into GastroPlus^TM to assess the contribution of our SPIP data to post-RYGB metformin absorption modeling. Previous simulations allowed a good fit with in vivo literature data on healthy and obese control subjects. However, it was revealed that for post-RYGB drug absorption predictions, simply excluding the duodenum/jejunum is insufficient, as the software underestimates the observed plasma concentrations post-RYGB. By implementing experimentally determined segmental-dependent permeabilities for metformin in the remaining segments post-surgery, GastroPlus^TM proved to fit the observed plasma concentration profile, making it a useful tool for predicting drug absorption after gastric bypass. Reliable evaluation of the parameters dictating drug absorption is required for the accurate prediction of overall absorption after bariatric surgery.

Short bowel syndrome: treatment options

Introduction Short bowel syndrome (SBS) refers to the malabsorptive state that occurs following extensive intestinal resection and is associated with several complications.

Methods The research for this review was conducted in the Pubmed database. Relevant scientific articles dated between 1991 and 2015 and written in Portuguese, Spanish or English were selected.

Results Several therapies, including nutritional support, pharmacological options and surgical procedures have been used in these patients.

Conclusions Over the last decades new surgical and pharmacological approaches emerged, increasing survival and quality of life (QoL) in patients with SBS. All SBS patients ought to have an individualized and multidisciplinary care that promotes intestinal rehabilitation.

Stem cell and niche regulation in human short bowel syndrome

Loss of functional small bowel surface area following surgical resection for disorders such as Crohn’s disease, intestinal ischemic injury, radiation enteritis, and in children, necrotizing enterocolitis, atresia, and gastroschisis, may result in short bowel syndrome, with attendant high morbidity, mortality, and health care costs in the United States. Following resection, the remaining small bowel epithelium mounts an adaptive response, resulting in increased crypt cell proliferation, increased villus height, increased crypt depth, and enhanced nutrient and electrolyte absorption. Although these morphologic and functional changes are well described in animal models, the adaptive response in humans is less well understood. Clinically the response is unpredictable and often inadequate. Here we address the hypotheses that human intestinal stem cell populations are expanded and that the stem cell niche is regulated following massive gut resection in short bowel syndrome (SBS). We use intestinal enteroid cultures from patients with SBS to show that the magnitude and phenotype of the adaptive stem cell response are both regulated by stromal niche cells, including intestinal subepithelial myofibroblasts, which are activated by intestinal resection to enhance epithelial stem and proliferative cell responses. Our data suggest that myofibroblast regulation of bone morphogenetic protein signaling pathways plays a role in the gut adaptive response after resection.

LGR5+ stem cells are expanded and BMP signaling regulates the stem cell niche in human short bowel syndrome.

Systematic review: the effect of right hemicolectomy for cancer on postoperative bowel function

BACKGROUND

Right-sided cancer accounts for approximately 30% of bowel cancer in women and 22% in men. Colonic resection can cause changes in bowel function which affect daily activity. The aims are to assess the impact of right hemicolectomy for cancer on bowel function and to identify useful treatment modalities for managing bowel dysfunction after right hemicolectomy.

METHOD

The review was conducted in line with PRISMA. Eligible studies evaluated the impact of right hemicolectomy on bowel function in those treated for colorectal neoplasia or assessed the effect of surgical technique or other intervention on bowel function after right hemicolectomy. Right hemicolectomy for inflammatory bowel disease or benign cases only were excluded. Articles were limited to studies on human subjects written in English published between January 2008 and December 2018.

RESULTS

The searches identified 7531 articles. Nine articles met the inclusion criteria, of which eight were cohort studies and one was a randomised trial. Loose stool, increased bowel frequency and/or nocturnal defaecation following right-sided colectomy occurs in approximately one in five patients. Some of these symptoms may improve spontaneously with time. Bile acid malabsorption and/or small bowel bacterial overgrowth may be the cause for chronic dysfunction. Some studies report that no or little difference in outcome between right-sided and rectal resections likely suggests poor function after right-sided resection.

CONCLUSION

Right hemicolectomy can result in changes to bowel function. Patients should be counselled preoperatively, and follow-up should be designed to identify and effectively treat significantly altered bowel function.

Parenteral Nutrition-Dependent Children With Short-Bowel Syndrome Lack Duodenal-Adaptive Hyperplasia but Show Molecular Signs of Altered Mucosal Function

BACKGROUND

Although adaptive mucosal growth of the remaining small intestine is an essential compensatory mechanism to bowel resection in experimental short-bowel syndrome (SBS), only scarce clinical data are available. We studied structural and molecular mechanisms of intestinal adaptation in children with SBS.

METHODS

Fourteen patients, who had been dependent on parenteral nutrition (PN) since neonatal period for a median (interquartile range)1.4 (0.7-6.5) years, were studied at the age of 1.5 (1.0-6.5) years. Median length of remaining small bowel was 33 (12-60) cm, and 6 patients had their ileocecal valve preserved. Six children without gastrointestinal disorders served as age-matched and gender-matched controls. All patients underwent duodenal biopsies. Mucosal microarchitecture, proliferation, apoptosis, inflammation, and epithelial-barrier function were addressed using histology, immunohistochemistry, and quantitative real-time polymerase chain reaction.

RESULTS

Villus height, crypt depth, enterocyte proliferation, and apoptosis were similar in patients and matched controls. Messenger RNA (mRNA) expression of numerous genes regulating gut epithelial-barrier function (TGFB2, CAV1, CLDN1, MUC2, and NLRC4) was significantly altered. Of various nutrient transporters studied, only expression of SLC2A1 encoding facilitative glucose transporter GLUT1 was increased among patients, whereas RNA expression of genes encoding sodium-dependent glucose, sterol, fatty-acid, and peptide transport remained unchanged.

CONCLUSION

Duodenal mucosal hyperplasia has a limited role in mediating physiological adaptation following intestinal resection among PN-dependent children with SBS. Further clinical studies addressing functional significance of the observed alterations in mucosal RNA expression are warranted.

Intestinal Failure and Rehabilitation

The rendering of proper care for the patient with intestinal failure requires the provider to have a functional understanding of digestion and absorption, nutrient requirements, and intestinal adaptation. Inherent in those concepts is that not only is nutritional absorption compromised, but medication absorption is as well. The principles of the management of home parenteral nutrition must be mastered and then proper and controlled weaning of parenteral nutrition may be commenced by use of dietary and pharmacologic means with appropriate clinical outcome measures followed. This complicated management requires a team experienced in both medical and surgical management of intestinal failure.

Host-Gut Microbiota Crosstalk in Intestinal Adaptation

Short-bowel syndrome represents the most common cause of intestinal failure and occurs when the remaining intestine cannot support fluid and nutrient needs to sustain adequate physiology and development without the use of supplemental parenteral nutrition. After intestinal loss or damage, the remnant bowel undergoes multifactorial compensatory processes, termed adaptation, which are largely driven by intraluminal nutrient exposure. Previous studies have provided insight into the biological processes and mediators after resection, however, there still remains a gap in the knowledge of more comprehensive mechanisms that drive the adaptive responses in these patients. Recent data support the microbiota as a key mediator of gut homeostasis and a potential driver of metabolism and immunomodulation after intestinal loss. In this review, we summarize the emerging ideas related to host-microbiota interactions in the intestinal adaptation processes.

Prolonged Absence of Mechanoluminal Stimulation in Human Intestine Alters the Transcriptome and Intestinal Stem Cell Niche

BACKGROUND & AIMS

For patients with short-bowel syndrome, intestinal adaptation is required to achieve enteral independence. Although adaptation has been studied extensively in animal models, little is known about this process in human intestine. We hypothesized that analysis of matched specimens with and without luminal flow could identify new potential therapeutic pathways.

METHODS

Fifteen paired human ileum samples were collected from children aged 2-20 months during ileostomy-reversal surgery after short-segment intestinal resection and diversion. The segment exposed to enteral feeding was denoted as fed, and the diverted segment was labeled as unfed. Morphometrics and cell differentiation were compared histologically. RNA Sequencing and Gene Ontology Enrichment Analysis identified over-represented and under-represented pathways. Immunofluorescence staining and Western blot evaluated proteins of interest. Paired data were compared with 1-tailed Wilcoxon rank-sum tests with a P value less than .05 considered significant.

RESULTS

Unfed ileum contained shorter villi, shallower crypts, and fewer Paneth cells. Genes up-regulated by the absence of mechanoluminal stimulation were involved in digestion, metabolism, and transport. Messenger RNA expression of LGR5 was significantly higher in unfed intestine, accompanied by increased levels of phosphorylated signal transducer and activator of transcription 3 protein, and CCND1 and C-MYC messenger RNA. However, decreased proliferation and fewer LGR5+, OLFM4+, and SOX9+ intestinal stem cells (ISCs) were observed in unfed ileum.

CONCLUSIONS

Even with sufficient systemic caloric intake, human ileum responds to the chronic absence of mechanoluminal stimulation by up-regulating brush-border enzymes, transporters, structural genes, and ISC genes LGR5 and ASCL2. These data suggest that unfed intestine is primed to replenish the ISC population upon re-introduction of enteral feeding. Therefore, the elucidation of pathways involved in these processes may provide therapeutic targets for patients with intestinal failure. RNA sequencing data are available at Gene Expression Omnibus series GSE82147.

Short Bowel Syndrome: Clinical Guidelines for Nutrition Management

Intestinal failure is a condition in which inadequate digestion or absorption of fluid, electrolytes, and nutrients leads to dehydration or malnutrition. The most common cause of intestinal failure is short bowel syndrome (SBS) defined as <200 cm of functional small intestine. SBS may result from congenital abnormalities or from surgical resection. For the past 3 decades, patients with severe SBS were managed with home parenteral nutrition (HPN). With the emergence of new therapies, the clinician now has multiple options to treat these patients. These include intestinal rehabilitation regimens whereby patients are treated with specialized oral diets, soluble fiber, oral rehydration solutions (ORS), and trophic factors to enhance absorption. There are also a variety of surgical techniques available to preserve intestinal length. Small bowel and multivisceral transplantation has evolved during the last decade to be a valid therapeutic option for those patients who cannot be rehabilitated or who fail HPN. These are interrelated services designed to offer the patient the best therapeutic options to meet their individual needs. This article reviews the principles associated with the nutrition management of this very complex and diverse group of patients.

Teduglutide for the Treatment of Short Bowel Syndrome

Objective:

To summarize the pharmacology, development, and clinical application of teduglutide (ALX-0600), a glucagon-like peptide-2 (GLP-2) analog for the treatment of short bowel syndrome (SBS).

Data Sources:

Clinical literature, including both primary sources and review articles, was accessed through a search of the MEDLINE databases (1980–March 2006). Key search terms included teduglutide, ALX-0600, glucagon-like peptide-2, short bowel syndrome, short gut, and intestinal adaptation. Clinical trial and drug data were supplied by the manufacturer, NPS Pharmaceuticals.

Study Selection and Data Extraction:

Review articles, abstracts, and clinical studies related to GLP-2 and its analog, teduglutide, were analyzed. An evaluation of the research exploring teduglutide for the management of SBS was conducted. Relevant information was then selected.

Data Synthesis:

Research has revealed that administration of GLP-2 to patients following major small bowel resection improves intestinal adaptation and nutrient absorption. Teduglutide is an enzyme-resistant GLP-2 analog that shows promise in preventing intestinal injury, restoring mucosal integrity, and enhancing intestinal absorptive function.

Conclusions:

Data from ongoing clinical trials indicate that teduglutide may have the ability to enhance intestinal absorptive capacity in patients with SBS. Further studies and the completion of Phase III trials are necessary to determine the appropriate dosage and length of treatment for patients with SBS to gain optimal therapeutic benefit from this drug.

Management of Crohn's Disease in the New Era of Gut Rehabilitation and Intestinal Transplantation

Despite recent therapeutic advances, patients with Crohn's disease (CD) continue to experience high recurrence with cumulative structural damage and ultimate loss of nutritional autonomy. With short bowel syndrome, strictures, and enteric fistulae being the underlying pathology, CD is the second common indication for home parenteral nutrition (HPN). With development of intestinal failure, nutritional management including HPN is required as a rescue therapy. Unfortunately, some patients do not escape the HPN-associated complications. Therefore, the concept of gut rehabilitation has evolved as part of the algorithmic management of these patients, with transplantation being the ultimate life-saving therapy. With type 2 intestinal failure, comprehensive rehabilitative measures including nutritional care, pharmacologic manipulation, autologous reconstruction, and bowel lengthening is often successful, particularly in patients with quiescent disease. With type 3 intestinal failure, transplantation is the only life-saving treatment for patients with HPN failure and intractable disease. With CD being the second common indication for transplantation in adults, survival outcome continues to improve because of surgical innovation, novel immunosuppression, and better postoperative care. Despite being a rescue therapy, the procedure has achieved survival rates similar to other solid organs, and comparable to those who continue to receive HPN therapy. With similar technical, immunologic, and infectious complications, survival is similar in the CD and non-CD recipients. Full nutritional autonomy is achievable in most survivors with better quality of life and long-term cost-effectiveness. CD recurrence is rare with no impact on graft function. Further progress is anticipated with new insights into the pathogenesis of CD and mechanisms of transplant tolerance.

The Pathogenesis of Resection-Associated Intestinal Adaptation

After massive small-bowel resection, the remnant bowel compensates by a process termed adaptation. Adaptation is characterized by villus elongation and crypt deepening, which increases the capacity for absorption and digestion per unit length. The mechanisms/mediators of this important response are multiple. The purpose of this review is to highlight the major basic contributions in elucidating a more comprehensive understanding of this process.

The concept of gut rehabilitation and the future of visceral transplantation

In the 1990s, the introduction of visceral transplantation fuelled interest in other innovative therapeutic modalities for gut rehabilitation. Ethanol lock and omega-3 lipid formulations were introduced to reduce the risks associated with total parenteral nutrition (TPN). Autologous surgical reconstruction and bowel lengthening have been increasingly utilized for patients with complex abdominal pathology and short-bowel syndrome. Glucagon-like peptide 2 analogue, along with growth hormone, are available to enhance gut adaptation and achieve nutritional autonomy. Intestinal transplantation continues to be limited to a rescue therapy for patients with TPN failure. Nonetheless, survival outcomes have substantially improved with advances in surgical techniques, immunosuppressive strategies and postoperative management. Furthermore, both nutritional autonomy and quality of life can be restored for more than two decades in most survivors, with social support and inclusion of the liver being favourable predictors of long-term outcome. One of the current challenges is the discovery of biomarkers to diagnose early rejection and further improve liver-free allograft survival. Currently, chronic rejection with persistence of preformed and development of de novo donor-specific antibodies is a major barrier to long-term graft function; this issue might be overcome with innovative immunological and tolerogenic strategies. This Review discusses advances in the field of gut rehabilitation, including intestinal transplantation, and highlights future challenges. With the growing interest in individualized medicine and the value of health care, a novel management algorithm is proposed to optimize patient care through an integrated multidisciplinary team approach.

Intestinal adaptation following resection

Intestinal adaptation is a natural compensatory process that occurs following extensive intestinal resection, whereby structural and functional changes in the intestine improve nutrient and fluid absorption in the remnant bowel. In animal studies, postresection structural adaptations include bowel lengthening and thickening and increases in villus height and crypt depth. Functional changes include increased nutrient transporter expression, accelerated crypt cell differentiation, and slowed transit time. In adult humans, data regarding adaptive changes are sparse, and the mechanisms underlying intestinal adaptation remain to be fully elucidated. Several factors influence the degree of intestinal adaptation that occurs post resection, including site and extent of resection, luminal stimulation with enteral nutrients, and intestinotrophic factors. Two intestinotrophic growth factors, the glucagon-like peptide 2 analog teduglutide and recombinant growth hormone (somatropin), are now approved for clinical use in patients with short bowel syndrome (SBS). Both agents enhance fluid absorption and decrease requirements for parenteral nutrition (PN) and/or intravenous fluid. Intestinal adaptation has been thought to be limited to the first 1-2 years following resection in humans. However, recent data suggest that a significant proportion of adult patients with SBS can achieve enteral autonomy, even after many years of PN dependence, particularly with trophic stimulation.

Complications of enterocutaneous fistulas and their management

Complications related to enterocutaneous fistulas are common and include sepsis, malnutrition, and fluid or electrolyte abnormalities. Intestinal failure is one of the most feared complications of enterocutaneous fistula management and results in significant patient morbidity and mortality. The authors review emerging trends in the medical and surgical management of patients with intestinal failure.

The citrulline generation test: proposal for a new enterocyte function test

BACKGROUND

The amino acid citrulline is mainly produced by enterocytes from conversion of glutamine. As fasting plasma citrulline proved disappointing as a biomarker for enterocyte dysfunction in clinical practice, we propose a citrulline generation test (CGT) to assess enterocyte function.

AIM

To assess the feasibility of a CGT in healthy subjects and patients with decreased enterocyte mass.

METHODS

Nineteen healthy subjects, 16 patients with intestinal villous atrophy and nine patients with short bowel syndrome (SBS) were given an oral bolus of 20 g of the dipeptide alanine-glutamine. Subsequent changes in plasma citrulline and other amino acid concentrations were determined using reverse-phase high-performance liquid chromatography.

RESULTS

Following the oral bolus of alanine-glutamine, plasma citrulline concentrations showed a time dependent rise in healthy subjects of 44 +/- 13% (38-55 micromol/L, P < 0.0001). The slope from baseline plasma citrulline to peak concentrations was 0.22 +/- 0.08, 0.13 +/- 0.04 and 0.09 +/- 0.04 micromol/L/min in healthy subjects, patients with coeliac disease (CeD) and refractory CeD, respectively (healthy subjects vs. CeD P < 0.05, healthy subjects vs. refractory CeD P < 0.001). In patients with SBS, the CGT was able to distinguish between non-adapted and adapted SBS by means of the incremental area under the CGT curve till 90 min (iAUC T90). The iAUC T90 was 447 +/- 179 and 1039 +/- 178 micromol/L/min in non-adapted and adapted SBS, respectively (P = 0.04).

CONCLUSION

An oral bolus of alanine-glutamine induces a time-dependent rise in plasma citrulline concentration to an extent dependent on the existence of villous atrophy or enterocyte hyperplasia in CeD, and adapted SBS, respectively.

Short bowel syndrome: parenteral nutrition versus intestinal transplantation. Where are we today?

Current management of short bowel syndrome (SBS) revolves around the use of home TPN (HPN). Complications include liver disease, catheter-related infections or occlusions, venous thrombosis, and bone disease. Patient survival with SBS on TPN is 86% and 75% at 2 and 5 years, respectively. Surgical management of SBS includes nontransplant surgeries such as serial transverse enteroplasty and reanastomosis. Small bowel transplant has become increasingly popular for management of SBS and is usually indicated when TPN cannot be continued. Posttransplant complications include graft-versus-host reaction, infections in an immunocompromised patient, vascular and biliary diseases, and recurrence of the original disease. Following intestinal-only transplants, patient and graft survival rate is 77% and 66% after 1 year. After 5 years the survival figures are 49% and 34%, respectively. Future improvements in survival and quality of life will enhance small bowel transplant as a viable treatment option for patients with SBS.

Short bowel syndrome: current medical and surgical trends

Short bowel syndrome is a chronic malabsorptive state usually resulting from extensive small bowel resections. A combination of diarrhea, nutrient malabsorption, dysmotility, and bowel dilatation may constitute the clinical symptomatology of this syndrome. The remaining bowel undergoes a process called adaptation, which may replace lost intestinal function. Chronic complications include nutrient, electrolyte, and vitamin deficiencies. Therapy depends largely on the administration of various factors stimulating intestinal adaptation of the remaining bowel. If the patient despite medical therapy fails to return to oral diet alone, then long-term parenteral nutrition is required. However, long-term parenteral nutrition may gradually induce cholestatic liver disease. Surgical methods may be required for treatment including intestinal transplantation, as a last resort for the treatment of end-stage intestinal failure. The goal of this review is to analyze the clinical spectrum and pathophysiologic aspects of the syndrome, the process of intestinal adaptation, and to outline the medical and surgical methods currently used to treat this complicated group of patients.

Dietary and medical management of short bowel syndrome in adult patients

Resection of the small bowel can lead to malabsorption of fluid, electrolytes, minerals, and other essential nutrients, resulting in malnutrition and dehydration. Individualized and tailored nutritional management for patients with short bowel syndrome (SBS) helps to optimize intestinal absorption, leading to nutritional independence such that a patient can resume as normal a lifestyle as possible. Parenteral nutrition (PN), used to supply the required nutrients following resection, is associated with a number of complications affecting patient morbidity and mortality. Attempts should be made to wean patients from PN to an oral diet as soon as possible. Dietary management is complex and needs to be individualized for each patient on the basis of his or her specific gastrointestinal anatomy, underlying disease, and lifestyle. In addition to nutrient intake, management of SBS also requires appropriate oral rehydration, vitamin and mineral supplementation, and pharmacotherapy. Several medications provide a useful adjunctive function to dietary intervention, including antidiarrheal agents, H2 antagonists and proton pump inhibitors, pancreatic enzymes, somatostatin analogs, antimicrobials, and trophic factors.

Strategies for parenteral nutrition weaning in adult patients with short bowel syndrome

The development of parenteral nutrition (PN) was an important, life-saving advance in the care of patients with short bowel syndrome (SBS). Nevertheless, its long-term use is often associated with complications. Therefore, it is desirable, when possible, to wean SBS patients to an oral diet. Given the complexity of PN weaning and the lack of published guidelines, the purpose of this article is to describe strategies of PN weaning and illustrate important clinical considerations during the weaning process. Patient education and motivation are key factors in successful PN weaning. The patient should have clearly defined care protocols and understand the importance of each aspect of the weaning program. Other factors likely to influence weaning success include the length and health of the remnant bowel, the presence of a colon, and the degree to which bowel adaptation has occurred. It is imperative that daily oral fluid and caloric intake goals are met prior to initiating PN weaning and that the patient receives an optimized dietary and medication plan. During weaning, the most practical measures for assessing adequate hydration and nutritional status are oral intake, stool and urine output, serum electrolytes and visceral proteins, and body weight. PN reductions can be made by either decreasing the days of PN infusion per week or decreasing the PN infusion volume equally across all days of the week. Use of recombinant human growth hormone, with or without glutamine, may play a role in facilitating the PN weaning process.