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13.09.12 Short bowel syndrome

Types
  • Jejunoileal resection and a jejunocolic anastomosis (jejunum-colon)
  • Predominantly jejunal resection with more than 10 cm of terminal ileum and the colon remaining (jejunum-ileum)
  • Jejunoileal resection, colectomy, and formation of a stoma (jejunostomy)

Clinical pictures
  • Jejunum-ileum
    • Rarely need long term enteral or parenteral nutrition
  • Jejunum-colon
    • Gradual undernutrition dominates the clinical picture
    • Due to adaptation, nutritional requirements may reduce with time
    • May need parenteral nutrition if less than 50 cm small intestine remains 
    • Need a high carbohydrate low oxalate diet
    • The volume of food may increase diarrhoea (grade A)
  • Jejunostomy
    • Fluid and electrolyte losses dominate the clinical picture
    • Adaptation does not occur so nutritional and fluid requirements do not reduce with time
    • If less than 200 cm of jejunum remains, oral hypotonic fluids may need to be restricted 
      • A glucose-saline supplement (sodium concentration of about 100 mmol/l) is sipped to reduce stomal losses of sodium
    • Hypomagnesaemia is common and is treated by correcting sodium depletion, oral or intravenous magnesium supplements
      • And occasionally with oral 1 alpha hydroxycholecalciferol
    • Jejunal output may be further reduced by drugs that reduce motility (loperamide) 
      • Or, if the bowel is very short (less than 100 cm), drugs that reduce gastric acid secretion (H2 antagonists, PPIs, or somatostatin analogues) 

Common causes of a short bowel
  • Jejunum-colon
    • Crohn’s disease 
    • Mesenteric ischaemia 
    • Irradiation 
    • Small bowel volvulus 
    • Adhesions 
  • Jejunostomy
    • Crohn’s disease
    • UC
    • Irradiation
    • Mesenteric ischaemia
    • Desmoid

Physiological consequences
  • Gastrointestinal motility
    • Gastric emptying and small bowel transit for liquid is normal in jejunum-colon patients but fast in patients with a jejunostomy 
      • Ileal and colonic braking mechanisms have been resected
    • May relate to circulating plasma levels of peptide YY and glucagon-like peptide 2 (GLP-2) 
  • Gastrointestinal secretions
    •  The majority of this fluid is reabsorbed in the upper jejunum
    • Jejunum-colon patients can reabsorb unabsorbed fluid in their colon but this is not the case for jejunostomy patients who lose much salt and water from their stoma
    • Jejunal mucosa is ‘‘leaky’’ and rapid sodium fluxes occur across it
      • If water or any solution with a sodium concentration of less than 90 mmol/l is drunk there is a net efflux of sodium from the plasma into the bowel lumen
    • Gastric acid hypersecretion may occur in the first two weeks after a small bowel resection
  • Absorptive functions
    • Vitamin B12 and fat malabsorption occurs when more than 60–100 cm of terminal ileum have been resected
    • Increased hepatic synthesis of bile salts cannot compensate for the loss of ileal surface area
      • Unabsorbed bile salts may contribute to colonic secretion in patients with a remaining colon
    • Magnesium deficiency occurs due to because of chelation with unabsorbed fatty acids and increased renal excretion (secondary hyperaldosteronism)
    • Hypomagnesaemia reduces the secretion and function of parathormone

Management of undernutrition
  • 50% or more of the energy from the diet may be malabsorbed
  • Parenteral nutrition should be avoided unless absolutely necessary
    • May only be needed for a few weeks or months before oral supplements are adequate
    • In the long term, parenteral nutrition is needed if a patient absorbs less than one third of the oral energy intake
  • Unabsorbed long chain fatty acids in the colon (In jejunum-colon patients)
    • Reduce transit time and reduce water and sodium absorption so making diarrhoea worse
    • Toxic to bacteria and so reduce carbohydrate fermentation
    • Bind to calcium and magnesium, increasing stool losses
    • Increase oxalate absorption so predisposing to the formation of renal stones
  • A low fat diet may increase calcium, magnesium, and zinc absorption but makes essential fatty acid deficiency more likely
    • Medium chain triglycerides are an alternative source of energy and are absorbed from the small and large bowel
  • If a diet is high in monosaccharides D-lactic acidosis may occur 

Vitamin and mineral deficiencies
  • Most patients require long term B12 treatment
  • Selenium deficiency is common and patients may need larger amounts than normal subjects
  • Zinc deficiency is uncommon unless stool volumes are large
  • Vitamins A, D, E, and K, and essential fatty acids may need to be replaced

Management of a patient with a jejunostomy
  • Exclude/treat causes other than a short bowel
    • Infection (intra or extraluminal)
    • Partial obstruction
    • Abrupt stopping of drugs
  • Correct dehydration with intravenous saline while the patient takes nothing by mouth for 24–48 hours
    • This stops thirst and thus the desire to drink 
  • Reduce oral hypotonic fluids to 500 ml/day
    • This is the most important measure
  • Give glucose/saline solution to sip (sodium concentration at least 90 mmol/l)
    • Most stomal/fistula losses (except from the colon) have a sodium concentration of about 100 mmol/l 
  • Add sodium chloride to any liquid feeds to make the sodium concentration near to 100 mmol/l while keeping osmolality near 300 mosmol/kg 
  • Give drugs to reduce motility
    • Loperamide 2–8 mg (non-sedative and non-addictive) before food
    • Occasionally, addition of codeine phosphate further reduces stomal output
  • If there is net ‘‘secretory’’ output (generally more than 3 l/24 hours), drugs that reduce gastric acid secretion can reduce stomal output by 1–2 l/24 hours
    • H2 antagonists or proton pump inhibitors
    • Octreotide if unable to absorb oral drugs, octreotide
  • Other measures include:
    • Separating solids and liquids (that is, having no drink for half an hour before or after food)
    • Using salt capsules instead of glucose/saline solution 
    • A trial of fludrocortisone if the ileum remains 
  • Correct hypomagnesaemia 
    • Intravenous magnesium sulphate initially then oral magnesium oxide and/or 1-alpha cholecalciferol

Summary



Notes
  • Bowel length measurements are from the duodenojejunal flexure 
    • Can be made at surgery or with the use of an opisiometer tracing out the long axis of the bowel on a contrast study
  • Normal human small intestinal length varies from about 275 cm to 850 cm, and tends to be shorter in women
  • In general, nutritional/fluid supplements are likely to be needed if less than 200 cm of small bowel remains
  • Daily gastrointestinal secretions:
    • 0.5 litre of saliva
    • 2.0 litres of gastric juice
    • 1.5 litres of pancreaticobiliary secretions plus passive jejunal secretions
  • Drug absorption may be impaired

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