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Management of short bowel


Discuss intestinal failure?

In the literature, intestinal failure (IF) and short bowel (SB) are used interchangeably. Short bowel syndrome (SBS) is defined as <200cm of small intestine (normal length 3-8 m) However functional short bowel syndrome may also occur in cases of severe malabsorption in which the bowel length is often intact. The degree of intestinal function is better described in terms of energy absorption/loss rather than length of residual intestine.

What is IF?

IF may be defined as the inability to sustain adequate nutritional, electrolyte, or hydrational status in the absence of specialised nutrition support. IF is termed as severe when parenteral (Nutrition and or water/electrolytes) supplements are needed.

What are the common causes of IF/SB?

Crohn’s disease, mesenteric ischaemia, irradiation, small bowel volvulus etc

What are the main types of SBS?
There are 3 main types of patients with a SB:

  • Jejunum-Colon: those who had a jejunoileal resection and a jejunocolic anastomosis
  • Jejunum-ileum: those who had a predominant jejunal resection and have more then 10cm of terminal ileum and the colon remaining. These patients are uncommon and rarely have problems of undernutrition and thus do not often need nutrition support.
  • Jejunostomy: those who had a jejunoileal resection, colectomy and formation of a stoma.

Can you predict long term fluid/nutritional support requirements based on the knowledge of residual small bowel length?
Yes

  • Colon intact- No nutritional support required if > 100 cms of small bowel (jejunum) left. Only enteral support may be needed with 51-100cms of small bowel. Parenteral nutrition needed when less than 50 cms of small bowel left
  • No colon- No nutritional support required if > 200 cms of small bowel (jejunum) left. Only enteral support may be needed with 101-200cms of small bowel. Parenteral support needed when less than 100 cms of small bowel left.

Discuss jejunum-colon patients?

Problems of undernutrition, diarrhoea (steatorrhoea which is malodorous and bulky) due to malabsorption, and vitamin/mineral deficiencies dominate the clinical picture. The colon has a large capacity to absorb sodium and water and thus these patients rarely need water or sodium supplements.

What are the principles of Management of jejunum-colon patients?

1. Undernutrition- 50% or more of the energy from the diet may be malabsorbed. Thus patients need to consume more energy either by eating more high energy food, having oral sip feeds or high energy enteral feeds given at night through a NG/PEG tube. However, increased energy intake leads to increased diarrhoea. Parenteral nutrition will need to be considered if the patient continues to lose weight or increasing oral/enteral intake causes a socially unacceptable amount of diarrhoea

2. Diarrhoea-

I. Causes of worsening

  • Unabsorbed long chain fatty acids in the colon reduce transit time and reduce water and sodium absorption, thus making diarrhoea worse
  • Ileal bile salt malabsorption occurs when >100cm TI is resected. This leads to impaired lipid digestion. Further bile salts affect colonocytes and impair water and salt absorption, thus worsening diarrhoea. In colon bile salts are also dehydroxylated to deoxy bile salts, which induce colonic water secretion. NB- Normally, the demand for bile salts for fat digestion cannot be met by synthesis alone. The demand is only met by ileal resorption of bile salts and the entero-hepatic circulation

II. Treatment of diarrhoea

  • Loperamide 2-8mg given half an hour before food and occasionally codeine phosphate is also added (30-60mg 30 minutes before food)
  • Limiting food intake- clearly not a feasible option. However if diarrhoea is unacceptable, parenteral nutrition will be needed.
  • Low fat diet- it is hard to implement because fat is energy dense and makes food palatable. A low fat diet will involve eating large volume of food. MCT are an alternative source of energy and are absorbed from the small and large intestine. Some, but not all LCT can be replaced by MCT in the diet because the essential fatty acid linoleic acid is a constituent of LCT and is not found in MCT.
  • Cholestyramine may help with bile salt diarrhoea. However, it will increase fat malabsorption by further reducing the bile salt pool and hence should not be used in patients with > 100 cm of ileal resection. Cholestyramine helps if < 100cms of ileum resected. (i.e. ileal resection of more than 100cms causes steatorrhoea. <100cm resection can cause diarrhoea without necessarily leading to steatorrhea)
  • Bile salt replacement- Cholylsarcosine has been used with variable improvement in fat absorption. There is no evidence for its use.
  • PPI-Small bowel resection is associated with transient gastric acid hypersecretion and hypergastrinemia, generally lasting for upto 6 months following resection.
  • Thus PPI help reduce diarrhoea shortly after surgery, but may not be effective in the long term. PPI help reduce gastric acid secretion and thus prevent the bile acid deconjugation in the duodenum and decreased pancreatic lipase excretion (thus enhances fat digestion).

3. Vitamin and mineral deficiencies

  • Long term B12 treatment is required is most cases.
  • Water soluble vitamin deficiencies are unusual in SBS patients as these are absorbed in the proximal jejunum.
  • Vitamins A, D, E and K and essential fatty acids may need to be replaced
  • Selenium deficiency is common. Zinc deficiency is uncommon unless stool volumes are large. Measure zinc, copper and selenium at baseline and then further testing depending on the baseline results.

4. Confusion
Specific causes of confusion:

  • Very low (<0.2 mmol/l) magnesium levels may cause mild confusion
  • Thiamine deficiency can cause Wernicke/korsakoff psychosis
  • D (-) lactic acidosis- Colonic bacteria degrade surplus fermentable carbohydrate to form D (-) lactate. This is absorbed but not easily metabolised causing a metabolic acidosis with a large anion gap. Treatment- a. restrict mono and oligosaccharides and encouraging the more slowly digestible polysaccharides (starch) b. thiamine supplements c. Broad spectrum antibiotics. Rarely the pt may need to fast with TPN
  • Hyperammonaemia (also occurs in jejunostomy pts) – The small amount of intestine remaining cannot manufacture adequate citrulline to detoxify ammonia via the urea cycle. The increase in blood ammonia creates problem only if there is concomitant renal impairment, as the excess ammonia cannot be excreted. Hyperammonaemia can be corrected by giving arginine (an intermediary in the urea cycle)

5. Drug absorption
Many, but not all, medications are absorbed in the jejunum.

  • Omeprazole can be absorbed in the duodenum/upper jejunum and only if less than 50 cms of jejunum remains are problems likely to occur.
  • May drugs will be incompletely absorbed and thus may be needed in much higher amounts (like thyroxine, digoxin, warfarin) or intravenously
  • Loperamide circulates in the enterohepatic circulation and hence need larger doses.

6. Gall stones
Gallstones are common (45%). Multiple therapies have been proposed including prophylactic cholecystectomy with massive small bowel resections.

7. Renal stones
In the presence of fat malabsorption, calcium preferentially binds to free fatty acids. This allows free oxalate to pass into the colon in which it is readily absorbed; dietary oxalate is absorbed only to a minimal extent in the small intestine. Oxalate can form discrete stones or less commonly a diffuse nephrocalcinosis leading to CRF. To prevent this, the pts should take a lox oxalate diet (avoiding food like spinach, rhubarb, beetroot, nuts, chocolate, tea, wheat bran, strawberries). Other measures include reducing dietary fat or replacing with MCT and increasing dietary calcium.

Discuss the management of jejunostomy patients?

1. Salt and water depletion
Jejunostomy patients lose large volume of salt and water from the stoma. This is greater after eating and drinking. The effluent from the stoma contains about 100mmol/l of sodium but relatively little potassium (15 mmol/l).
Potassium balance is usually not a problem unless less than 50 cm of jejunum remains. A low serum K is usually due to Na depletion with secondary hyperaldosteronism and thus greater than normal urinary losses of K. Low K can also be due to low Mg, which causes dysfunction of many of the K transport systems and increases urinary K losses. This hypokalemia is resistant to K treatment but responds to Mg replacement.

2. Hypomagnesemia
Causes
reduced absorption because of chelation with unabsorbed fatty acids
increased urinary losses due to secondary hyperaldosteronism
Low Mg reduces PTH secretion and function, so directly increasing urinary Mg losses and indirectly by reducing 1, 25, OH Vitamin D production, which normally increases jejunal Mg absorption

Treatment:
Correct water and salt depletion and thus hyperaldosteronism
Oral MgO (4mmol/capsule) – 12-24 mmol/day. MgO is usually given at night when intestinal transit is assumed to be slowest and hence there is more time for absorption. Mg salts may however worsen diarrhoea/stoma output.
If oral Mg salts do not normalise Mg levels- oral 1 alpha OH Cholecalciferol in a gradually increasing dose (q 2-4 weeks) of 0.25-900mcg daily may improve Mg balance. regular monitoring of serum calcium is necessary to avoid hypercalcemia.
IV Mg occasionally.

3. Undernutrition
These patients need a high energy diet in which osmolality is kept low using large molecules (polysaccharides, protein and triglycerides) and to which NaCL is added to give the feed a total Na conc. of 90-120 mmol/l and an osmolality of approx 300 mosm/kg
There is no advantage in giving a diet of small molecules, like elemental diet, which causes the feed to be hyperosmolar, thus increasing stomal losses
Jejunostomy pts absorb a constant proportion of the nitrogen, energy, and fat from their diet. Increasing fat in the diet increased energy density and keeps the diet osmolality low. It does increase fat excretion but does not usually increase stomal output, nor make output more offensive.

4. Many other problems like B12 def, confusion, drug absorption and gall stones are similar to jejunum colon patients.

Discuss the management of a high output jejunostomy/ileostomy?

Management principles are the same for management of high output enterocutaneous fistula and a high output jejunostomy/ileostomy.

  • Exclude other causes of a high output like intraabdominal sepsis, partial/intermittent bowel obstruction, gastroenteritis, recurrent disease in the remaining bowel, suddenly stopping drugs (steroids/opioid) or using prokinetics.
  • Correct dehydration with IV saline while the patient stays NPO for 24-48 hrs. This stops thirst and the desire to drink and will also demonstrate that output is driven by their oral intake. Over 2-3 days IV saline is gradually withdrawn while food and restricted fluids are introduced.
  • Restrict hypotonic (water, tea, coffee, fruit juices, alcohol etc) and hypertonic (fruit juices, coca cola and most commercial sip feeds) fluids to less than 500 ml daily. To make up the rest of the fluid requirement, the patient is encouraged to drink a glucose-saline solution (WHO or St Marks).  The pt is encouraged to drink a litre or more throughout the day. It is a common mistake for pts to be encouraged to drink oral hypotonic solutions to quench their thirst but this causes large stomal losses
  • Jejunostomy effluent is constant at 90 mmol/ and as fluid and glucose absorption improves with increasing Na concentration, pts are advised to sip glucose saline solution with a Na conc. of at least 90 mmol/l or take NaCL capsules. Pts with stomal losses of less than 1200 ml daily can maintain Na balance by adding extra salt to the limit of palatability at the table and when cooking. When stoma losses are 1200-2000 ml or more, Na balance may be maintained by taking a glucose-saline solution or salt capsules. NaCL capsules (500mg each) are effective when taken in large amounts (14/24 hrs) but can cause nausea and vomiting.
  • Drug therapy- if above measures is not adequate the following drugs may be useful
    • Loperamide and codeine- reduce intestinal motility and thus decrease stoma output by 20-30%. Loperamide is more effective but the effects of the two together may be greater.
    • PPI reduce stoma output particularly if it is more than 2 litres
    • Octreotide (50 mcg SC BD) reduces stoma output possibly by slowing intestinal transit.
    • Mineralacorticoids (2mg fludrocortisone or 2 mg IV d-aldosterone) or high dose hydrocortisone may reduce stoma output in pts with a retained ileum.

Some patients will not maintain hydration with the above measures and IV/SC saline will be needed.

Ref

  1. Based on British Society of Gastroenterology guidelines for Management of Patients with a Short Bowel



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