ncbi.nlm.nih.gov
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`http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3133978/
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`Short Bowel Syndrome: A Review of Management Options
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`Saudi J Gastroenterol. 2011 Jul-Aug; 17(4): 229–235.
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`doi: 10.4103/1319-3767.82573
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`PMCID: PMC3133978
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`Prasad Seetharam and Gabriel Rodrigues
`This article has been cited by other articles in PMC.
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`Abstract
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`Extensive resection of the intestinal tract frequently results in inadequate digestion and/or absorption of nutrients, a
`condition known as short bowel syndrome (SBS). This challenging condition demands a dedicated multidisciplinary
`team effort to overcome the morbidity and mortality in these patients. With advances in critical care management,
`more and more patients survive the immediate morbidity of massive intestinal resection to present with SBS. Several
`therapies, including parenteral nutrition (PN), bowel rehabilitation and surgical procedures to reconstruct bowel have
`been used in these patients. Novel dietary approaches, pharmacotherapy and timely surgical interventions have all
`added to the improved outcome in these patients. However, these treatments only partially correct the underlying
`problem of reduced bowel function and have limited success resulting in 30% to 50% mortality rates. However,
`increasing experience and encouraging results of intestinal transplantation has added a new dimension to the
`management of SBS. Literature available on SBS is exhaustive but inconclusive. We conducted a review of scientific
`literature and electronic media with search terms 'short bowel syndrome, advances in SBS and SBS’ and attempted to
`give a comprehensive account on this topic with emphasis on the recent advances in its management.
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`Keywords: Intestinal adaptation, intestinal failure, malabsorption, short bowel syndrome, total parenteral nutrition
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`Short bowel syndrome (SBS) is an intestinal failure resulting from an inadequate length of intestine following intestinal
`resection. Intestinal failure refers to a condition that results in inadequate digestion or absorption of nutrients or both,
`so that an individual becomes malnourished and requires specialized medical and nutritional support.[1]
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`The prevalence of SBS is 3-4 per million.[1] It occurs in about 15% of adult patients who undergo intestinal resection,
`with 3/4th of these cases resulting from massive intestinal resection and 1/4th from multiple sequential resections.[2]
`About 70% of patients in whom SBS develops are discharged from the hospital and a similar percentage remain alive
`a year later.[3] This improved survival rate has been achieved primarily by the ability to deliver long-term nutritional
`support.
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`ETIOLOGY AND PATHOPHYSIOLOGY
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`Several conditions requiring intestinal resection lead to SBS. In a reported series of 210 cases, these conditions
`included postoperative 52 (25%), irradiation/cancer 51 (24%), mesenteric vascular disease 46 (22%), Crohn's disease
`34 (16%) and other benign causes 27 (13%).[4] The manifestations of SBS are due to:
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`1. Loss of absorptive surface area
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`2. Loss of site-specific transport processes
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`3. Loss of site-specific endocrine cells and gastrointestinal (GI) hormones
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`4. Loss of ileocecal valve
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`The major consequence of extensive intestinal resection is loss of absorptive surface area, which results in
`malabsorption of macro and micronutrients, electrolytes and water.[5] Most macronutrients are absorbed in the
`proximal 100–150 cm of intestine.[6] Specific micronutrients are absorbed from specific areas of small intestine.
`Intestinal remnant length is the primary determinant of outcome in patients with SBS. Resection of up to half of small
`intestine is generally well tolerated. SBS is likely to develop in patients with loss of two-thirds length of small intestine.
`Permanent total PN (TPN) support is likely to be needed in patients with less than 120 cm of intestine without colon in
`continuity and less than 60 cm with colonic continuity.[7] Besides, malabsorption of macro and micronutrients with a
`loss of intestinal absorptive surface area results in water and electrolyte malabsorption, which manifests as
`voluminous diarrhea, hypovolemia, hyponatremia and hypokalemia.
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`The absorption of some compounds is restricted to certain areas of small intestine. Iron, phosphorus and water soluble
`vitamins are predominantly absorbed in proximal small intestine. As most patients with SBS have intact duodenum
`and proximal jejunum, deficiencies of these entities are rare but tend to develop calcium and magnesium deficiency.[8]
`Having lost part or whole of the ileum, vitamin B12 and bile salt malabsorption also develops. Even hormones in the
`GI mucosa are distributed in a site specific manner. Gastrin, cholecystokinin, secretin, gastric inhibitory polypeptide
`and motilin are produced by endocrine cells in proximal gastrointestinal tract (GIT). In SBS, the status of these
`hormones remains intact. Glucagon-like peptide (GLP) 1 and 2, neurotensin, and peptide YY are produced in ileum
`and proximal colon. In SBS, deficiency of these hormones is common and this results in rapid gastric emptying,
`shortened intestinal transit and hypergastrinemia.[9,10] The presence of ileocecal junction improves the functional
`capacity of intestinal remnant.[11] Although previously this had been attributed to a barrier function and transit
`prolonging property of ileocecal valve, this advantage may actually be related to the specialized property of the
`terminal ileum itself.
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`INTESTINAL ADAPTATION
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`The small intestine is able to adapt to compensate for the reduction in absorptive surface area caused by intestinal
`resection. This process occurs in the first couple of years following resection.[12] This adaptive response results from
`changes in the intestinal structure, motility and function. Structural adaptation following intestinal resection involves all
`the layers of the intestine.[13] The process is characterized by crypt cell proliferation, lengthening of the villi, increase
`in the ratio of the crypts to villi, increase in microvilli along the epithelial surface and an overall increase in the mucosal
`weight. The thickness and length of muscle layers increase as a result of hyperplasia.
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`Intestinal motor activity is also altered by intestinal resection.[ 14] Motor adaptation seems to be more prominent in the
`jejunum than in the ileum. There is disrupted motor activity in the first few months after resection followed by
`adaptation. Studies demonstrate a shorter duration of migrating motor complex cycle and fed pattern after resection.
`[15] Functional adaptation results in improved absorption by individual enterocytes.[1] This process is facilitated by
`structural and motor adaptation which results in prolonged intestinal transit time.
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`The mechanism of intestinal adaptation is not entirely understood. The degree of intestinal adaptation is related to the
`extent and site of intestinal resection.[13] Adaptation is greater with extensive intestinal resection and ileum has a
`greater adaptive capacity than jejunum. Factors which influence intestinal adaptation include GI regulatory peptides,
`growth factors, hormones, cytokines, and tissue factors which include immunity, blood flow and neural influences.
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`MEDICAL MANAGEMENT
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`The early management of a patient with SBS is that of a critically ill surgical patient who has recently undergone
`intestinal resection and other concomitant procedures. Thus, control of sepsis, maintenance of fluid and electrolyte
`balance and initiation of nutritional support are important in the early management of these patients. For patients who
`have survived this early phase, the primary goals of management are to maintain adequate nutritional status and
`prevent development of complications related to both underlying pathophysiology and nutritional therapy.
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`Maintenance of nutritional status
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`This is the primary objective in the management of SBS. Fluid and electrolyte losses from the GIT may be great in the
`early postoperative period and must be monitored and replaced. TPN will be required in the early postoperative period
`and enteral nutrition should be initiated as soon as possible.
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`Patients with limited ileal resection (less than 100 cm) with or without right hemicolectomy can resume intake of solid
`food in late postoperative phase. These patients may develop diarrhea or steatorrhea with consumption of a regular
`diet due to fat malabsorption, which in turn can lead to deficiencies of fat soluble vitamins, vitamin B12, calcium and
`magnesium. The deficiencies of these nutrients should be looked for and these nutrients should be supplemented if
`needed. Maintenance of nutritional status becomes all the more important in the setting of diarrhea, which is quite
`common in SBS and may be due to gastric acid hypersecretion, rapid intestinal transit time and fat malabsorption. H2
`blockers, proton pump inhibitors (PPI), antidiarrheals, cholestyramine and octreotide have all been used to control
`diarrhea. Octreotide acts by slowing intestinal transit and increasing sodium and water reabsorption,[16] but carries
`potential risk of decreasing splanchnic protein synthesis, thereby inhibiting intestinal adaptation and also a risk of
`cholelithiasis. These medications should be taken one hour before meals and their effect on diarrheal volume should
`be evaluated before they are recommended for long-term treatment.
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`Glucose polymer-based oral rehydration salts (ORS) are recommended for patients to improve hydration and thereby
`reduce TPN requirements. Glucose and sodium are absorbed through the same active transport mechanisms and
`stimulate the absorption of each other. In addition, glucose promotes sodium and water absorption by means of
`solvent drag.
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`Dietary management and special diets
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`Patients with SBS should be encouraged to eat substantially more than usual (a hyperphagic diet) to compensate
`malabsorption. Patients should be encouraged to eat small portions throughout the day rather than at defined meal
`times. Those with colonic continuity should be provided with a high complex carbohydrate diet containing starch, non-
`starch polysaccharides and soluble fibers. These food stuffs which are typically not absorbed by human small
`intestine get fermented by colonic bacteria into butyrate, acetate and propionate. Butyrate is the preferred fuel for
`colocyte.[17] Studies have indicated that up to 525 to 1170 kcals per day can be absorbed from an intact colon from
`fermentation of unabsorbed carbohydrates and soluble fibers.[18] The amount of energy absorbed is proportional to
`the length of residual colon and may increase as a part of adaptive response to enterectomy.
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`Treatment of steatorrhea associated with ileal resection
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`Fat maldigestion due to bile salt malabsorption occurs when more than 100 cm of terminal ileum has been resected.
`Various therapeutic options have been suggested for the treatment of the resulting steatorrhea. Use of bile salt
`replacement therapy with ox bile or a synthetic conjugated bile acid (cholesarcosine) has been reported.[18] The bile
`acid sequestering agent cholestyramine may be useful in decreasing bile salt related diarrhea in patients with less
`than 100 cm of terminal ileum loss, but may worsen steatorrhea in those patients who have undergone a more
`significant resection, because of its binding with dietary lipid.[19] Also cholestyramine interferes with absorption of
`many medications. These patients may be put on low-fat high-carbohydrate diet.[20] Low fat may decrease
`steatorrhea, but it also results in decreased energy intake which may worsen patients energy balance. However, a
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`high fat intake is associated with malabsorption of divalent cations, delayed gastric emptying, early satiety and
`increased water loss from colon. Since medium chain triglycerides (MCT) are absorbed in colon, dietary
`supplementation with MCT may lead to increased energy consumption.[20,21] Limitations of MCT include the fact that
`they do not provide essential fatty acids (FAs) and can cause nausea, vomiting and ketosis.
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`Another important aspect of dietary management is to provide a diet that will maximize intestinal adaptive response.
`[22] Provision of fat and dietary fibers may be particularly important in this regard. Long and short chain FA appear to
`have a greater trophic effect on the intestine than medium chain FA do. Although these nutrients directly stimulate
`intestinal adaptation, they also bring about intestinal adaptation through endocrine and paracrine effects.
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`Pharmacologic therapy for SBS is a rapidly expanding area of investigation. Recent evidence suggests that provision
`of appropriate diet, nutritional supplements such as glutamine and growth factors such as growth hormone improves
`intestinal absorption and perhaps modifies the adaptive response in patients with established SBS.[23] Currently
`GLP-2 appear to have the most promising results.[24]
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`Home parenteral nutrition
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`Home parenteral nutrition is an option for patients who require long-term TPN. To prepare the patient for home TPN,
`the regime should be compressed gradually in 2 to 4 h daily increments so that the total volume can be infused over a
`10–12-h period, typically over night. The TPN infusion is generally tapered off over a 30–60-min period to avoid
`hypoglycemia. Additional fluid allowances may be needed for patients with a permanent jejunostomy. The TPN
`solutions should be infused into a central vein such as superior or inferior venacava through a tunneled catheter to
`decrease the risks of infection and thrombosis.[25]
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`Prevention of complications
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`Complications in SBS could be related to either the underlying pathology or the nutritional therapy. Among patients
`who require long-term TPN for survival, sepsis and liver disease related to TPN are important factors governing
`morbidity and mortality. The incidence of sepsis varies from 0.1 to 0.3 episodes per patient per year of TPN. Sepsis
`may be associated with catheter thrombosis. In cases with catheter-related sepsis an attempt at line sterilization
`before removal is appropriate when infections are caused by coagulase-negative staphylococci and gram-negative
`bacteria.
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`End-stage liver disease develops in about 15% of patients on long-term TPN and is associated with a survival time of
`about 1 year without liver transplantation.[26] The etiology of TPN-associated liver disease is not completely
`understood and seems to be multifactorial. This is reversible in initial stages, but ultimately leads to severe steatosis,
`cholestasis and cirrhosis. The liver function tests (LFTs) of patients on long-term TPN should be monitored regularly
`and patients with abnormal LFT should undergo ultrasound evaluation of gall bladder and bile ducts and should have
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