Gastroenterology and Hepatology Board Review: Pearls of Wisdom, Third Edition
Section VII NUTRITION
CHAPTER 42. Short Bowel Syndrome
Carol Rees Parrish, MS, RD and Nora Decher, MS, RD, CNSC
Adults with what remaining length of small intestine are at risk of developing malabsorption consistent with short bowel syndrome?
Approximately 200 cm (6.5 ft). This length is often used as a guideline for the definition of short bowel syndrome; however, the absolute length varies considerably among individuals.
True/False: The length of small bowel differs between men and women.
True. The length of small intestine is approximately 630 cm in men and approximately 590 cm in women. The length of colon is about 150 cm in both sexes.
What are the major causes of short bowel syndrome in adults?
Postoperative complications, mesenteric infarction, radiation enteritis, Crohn’s disease, trauma, and volvulus.
What is the leading cause of short bowel syndrome in children?
Congenital abnormalities such as intestinal atresia, gastroschisis, malrotation with midgut volvulus, and aganglionosis.
What is the difference in villi shape in different parts of small intestine?
The villi are taller and crypts deeper in the jejunum than the ileum. The activity of microvillus enzymes and nutrient absorptive capacity per unit length of intestine is several-fold higher in the proximal than in distal small bowel.
True/False: The majority of digestion and absorption of most nutrients occurs in the distal ileum.
False. The digestion and absorption of most macro- and micronutrients occur in the first 100 cm of jejunum. Therefore, patients with short bowel syndrome in general can maintain nutritional balance on oral feeding if more than 100 cm of jejunum remains. Conversely, most patients with a jejunal length of less than 100 cm will require long-term parenteral nutrition (PN), depending on the presence of the colon.
Where is the site of absorption of macronutrients (fat, protein, and carbohydrate) and micronutrients (calcium, magnesium, and iron)?
The primary site for iron and folate absorption is the duodenum. Macronutrients and most other micronutrients, including calcium, are absorbed in the proximal jejunum. Bile acids and food-bound vitamin B12 are only absorbed in the ileum (synthetic B12 is absorbed throughout the small intestine). Electrolytes and water are absorbed in both the small and large intestines.
What is the absorptive efficiency of fluids received by the small intestine?
The proximal small intestine receives about 9 L/day of water and electrolytes from food and secretions. About 8 L of this is reabsorbed throughout the small intestine.
What is an appropriate concentration of sodium and glucose in oral rehydration solutions to achieve net sodium and water absorption in the jejunum?
A mixture of 13–20 g glucose and 75–90 mEq (1725–2070 mg) sodium per liter.
True/False: Moderate bile acid malabsorption can occur with less than 100 cm of ileum resected.
True. More extensive resection causes bile acid depletion resulting in fat malabsorption and steatorrhea.
What length of terminal ileal resection may result in vitamin B12 deficiency?
More than 50–60 cm.
True/False: Unabsorbed hydroxylated fatty acids and bile salts following extensive ileal resection cause diarrhea by stimulating colonic secretion and motility.
True. The stimulation of colonic electrolyte and water secretion is sometimes referred to as “cholerrheic diarrhea.”
What is the effect of extensive small intestinal resection on the serum gastrin level during the first 6–12 months postoperatively?
Hypergastrinemia occurs within 24 hours of extensive small bowel resection and may last up to a year. This may lead to gastric acid and volume hypersecretion, peptic complications, inactivation of pancreatic enzymes, and destabilization of bile salts.
What is the most prominent clinical symptom in patients with short bowel syndrome?
Diarrhea, steatorrhea, or both.
What type of solution should be started postoperatively in patients with high output end-jejunostomy syndrome?
Oral rehydration solution. Hypotonic solutions may result in paradoxical jejunal sodium and water secretion.
A 59-year-old man with ischemic bowel disease underwent intestinal resection 9 months ago and the total length of jejunum remaining is 120 cm with an intact colon. He has lost a substantial amount of weight despite eating his previous diet. What type of oral diet should be recommended for this patient?
A hyperphagic diet high in complex carbohydrates and low in fat is recommended. Oxalate restriction is also recommended in this setting.
What is the first-line treatment of diarrhea in a patient with limited ileal resection less than 100 cm?
Cholestyramine to bind unabsorbed bile salts.
What is the first-line treatment of diarrhea in a patient with extensive ileal resection more than 100 cm?
What is the effect of resection of the ileocecal valve on absorption of nutrients?
Although conflicting evidence exists, loss of the ileocecal valve is thought to facilitate small bowel bacterial overgrowth, which can lead to maldigestion.
True/False: A patient with a remaining jejunal length of 150 cm and an intact colon should be able to avoid the need of permanent PN support.
True. Patients with a jejunal length of 100 cm in continuity with the colon can usually be managed by oral intake alone depending upon the health of the remaining bowel. Permanent PN support will likely be needed in those with < 100 cm jejunum without any colon remaining.
What medications may be useful in a patient with an end-jejunostomy whose stomal losses exceed liquid intake?
Antisecretory agents such as H2 receptor antagonists, proton pump inhibitors, and somatostatin analogues may be useful in this setting. High doses of nonspecific antidiarrheals may also be of benefit.
What is the risk of oxalate kidney stones in patients with short bowel syndrome and colectomy?
None. Oxalate requires an intact colon for absorption.
How is hyperoxaluria in patients with short bowel syndrome and preserved colon treated?
Restriction of oxalate-containing food products such as tea, chocolate, cola beverages, certain fruits, and vegetables. Adequate fluid intake is to ensure a urine output greater than 1200–1500 mL/day. Oral calcium citrate may also be helpful to bind oxalate and prevent its absorption.
A patient with short bowel syndrome and a preserved colon presents with episodes of confusion, ataxia, and inappropriate behavior. What is the most likely diagnosis?
D-lactic acidosis is a rare complication observed only in short bowel patients with an intact colon. The episodes of acidosis are usually precipitated by an increased oral intake of refined carbohydrate. Malabsorbed carbohydrates are metabolized by colonic bacteria to short chain fatty acids and lactate.
What is the appropriate management of a patient with D-lactic acidosis?
Correction of acidosis by sodium bicarbonate and restricting concentrated carbohydrate intake. The potential benefit of oral antibiotics is debated.
What is the nutritional value of a clear liquid diet in patients with short bowel syndrome?
None. In addition, it is hyperosmolar and may provoke osmotic diarrhea.
What is the value of a full liquid diet in patients with short bowel syndrome?
None. A full liquid diet may be poorly tolerated because it contains lactose, is highly osmotic, and in those who are fat intolerant, can aggravate fat malabsorption. It is important to note that not all patients with short gut are lactose intolerant; many can take small amounts over the day without exacerbating symptoms.
Where is the border between the jejunum and the ileum?
In general, the proximal two-fifths (about 240 cm) of the small bowel is called the jejunum and the distal three-fifths (about 360 cm) the ileum.
What are the major bowel factors responsible for adaptation in short bowel syndrome?
Amount of intestine remaining, the sections remaining, the presence of an ileocecal valve, and the condition of the residual intestine. In addition to bowel factors, a number of nutritional and hormonal factors play a role in the adaptation process.
What are the major mechanisms by which enteral nutrients stimulate intestinal adaptation?
Direct contact with epithelial cells, stimulation of trophic gastrointestinal hormone secretion, and stimulation of pancreatic and biliary secretions.
What are the adaptive changes to the small intestine after an extensive small intestinal resection?
Luminal dilation, thickening and lengthening of gastrointestinal tract, and hyperplasia of the crypt-villus axis leading to increased surface area. This occurs primarily in the ileum, less so in the jejunum.
Which hormones have a trophic effect on the small intestine?
Gastrin, secretin, cholecystokinin, epidermal growth factor, corticosteroids, enteroglucagon, prostaglandins and growth hormone releasing factor, and glucagon-like peptide 2(GLP-2). Somatostatin has a negative effect on gut adaptation.
Resection of which part of small intestine has only a limited effect on the ability of the small intestine to adapt?
Jejunum. The ileum has the greatest capacity for adaptation and is able to compensate for and take over almost all of the jejunum’s absorptive function. Unfortunately, the ileum is most often resected in patients with short gut.
What are the major regulatory hormones in the proximal gastrointestinal tract?
Gastrin, cholecystokinin, secretin, motilin, and gastrin inhibitory peptide.
What are the major regulatory hormones in the distal gut?
Peptide YY, GLP-1, and GLP-2.
Why do some patients with short bowel syndrome have rapid gastric emptying of liquids and rapid intestinal transit time?
Lack of GLP-1 and peptide YY secreted by the L-cells of the resected distal ileum (ileal brake slows gastric emptying and small bowel transit) and proximal colon.
True/False: A barium contrast small bowel series is the best way to estimate the length of a patient’s remaining bowel.
False. The most accurate assessment of remaining small bowel length is to measure it at the time of surgery. Unfortunately, this is often not done or only the length resected is measured. A small bowel series is useful as an alternative.
What are the major electrolyte and trace element losses in a patient with a high output end-jejunostomy?
Sodium, potassium, calcium, magnesium, iron, zinc, and copper.
Why are patients with short bowel syndrome prone to develop cholesterol gallstones?
Decreased hepatic bile secretion, supersaturation of bile with cholesterol, gallbladder hypomotility, and formation of gallbladder sludge. The use of medications such as somatostatin analogues may also contribute.
What is the time period of maximal small intestinal adaptive response in humans after extensive small intestinal resection?
One year, although adaptation may occur over a longer period of time.
What segment of small intestine has the highest adaptive capability?
What is the most critical determinant of the need for permanent PN support after extensive small bowel resection and colectomy?
Length of remaining ileum. Patients with ileal length of less than 100 cm cannot maintain adequate nutrient absorption. These patients will usually require long-term PN. Jejunal resection is better tolerated than ileal resection due to unique characteristics of the ileum and its potential for adaptation.
What type of magnesium supplement is most likely to be tolerated best in patients with short bowel syndrome?
Magnesium gluconate is less likely to cause an osmotic diarrhea than other magnesium-containing compounds.
What are the major vitamin deficiencies in a patient with extensive jejunal resection?
The fat-soluble vitamins A, D, E, and K.
What is the ideal caloric intake in a patient with short bowel syndrome?
Caloric needs for patients with short bowel syndrome may range from 30 to 40 kcal/kg/day, depending on the patient’s absorptive capacity, and the amount necessary for maintenance of the patient’s goal weight.
What percentage of patients with short bowel syndrome requires total PN in the immediate postoperative period?
What are the indications for small bowel transplantation in short bowel syndrome?
Permanent need for PN support along with one or more of the following serious complications of PN: progressive liver disease, loss of vascular access sites, and recurrent episodes of central venous catheter sepsis (single episode of fungal sepsis).
What trophic factor has recently shown promising results in promoting mucosal growth in patients with short bowel syndrome and may become available for use in the relatively near future as an aid to weaning PN?
GLP-2 analogue (teduglutide). Recombinant human growth hormone with or without glutamine is currently approved for use for the same indication.
What are the major causes of morbidity and mortality following small bowel transplantation?
Infection and graft rejection.
What nontransplant surgical options exist to enhance the function of the existing bowel in selected short bowel patients?
Intestinal lengthening (eg, Bianchi procedure and serial transverse enteroplasty [STEP]), intestinal tapering, and reversed intestinal segment. Performance of these procedures is also referred to as autologous gastrointestinal reconstruction.
What is the single most effective surgical procedure to allow discontinuation of PN support in short bowel syndrome?
Restoration of bowel continuity.
True/False: Plasma citrulline level is a reliable marker for a patient’s potential to be weaned from PN.
False. Citrulline may reflect remnant intestinal mucosal mass and has been shown to correlate with the need of permanent PN support in short bowel patients; however, it does not reflect how well the patient will utilize this mass. It is unlikely that the citrulline concentration reflects the various aspects of gut absorption since the latter involves not only the small bowel mucosa but also the trophic effects of pancreatic-biliary secretions, gut motility, and colonic absorption. Finally, given the alternative, making every effort to wean a patient from PN should always be attempted as opposed to relying on a lab value or other biomarker.
• • • SUGGESTED READINGS • • •
Langnas AN, Goulet O, Quigley EMM, Tappenden KA, eds. Intestinal Failure: Diagnosis, Management and Transplantation. Malden, MA: Blackwell Publishing; 2008.
Parrish CR. The Clinician’s Guide to Short Bowel Syndrome. Practical Gastroenterology. 2005;XXIX(9):67.
Efsen E, Jeppesen PB. Modern treatment of adult short bowel syndrome patients. Minerva Gasterol Dietol. 2011;57(4):405-417.