How does one define short gut?
Small bowel length in four series have shown a mean length of 500 cms with a range of 300-850 cms. There is therefore a three-fold range in length; one of the studies was in patients with Crohn’s disease who fell into the same range.
In general, severe nutritional sequelae are common if the residual length is 100 cms or less, and some problems occur if the length is 100-200 cms. A person with a naturally short length of gut may thus develop intestinal failure after resection of 150 cms whereas someone with a long small intestine would not be harmed by a similar procedure.
What are the potential problems?
a) Electrolytes – There are two
1) Sodium deficiency – Hyponatraemia can lead to extra-cellular fluid loss and liability to hypotension and pre-renal failure.
2) Magnesium deficiency - Hypomagnesemia is manifested by paraesthesia and tetany.
b) Nutrition – If energy absorption is atleast 60% it is usually possible to maintain nutrition by increasing oral intake. If energy absorption is less than 60%, particularly if it is around 30% or less, parenteral nutritional supplements are needed.
Specific deficits of particular nutrients include Vitamin B12 if the distal ileum is removed, and fat soluble vitamins if there is fat malabsorption.
c) Renal stones – Formation of renal stones may be due to persistent dehydration with low volumes of concentrated urine, aggravated by excess intestinal absorption and urinary excretion of oxalate if the colon is present.
d) Social problems of intestinal effluent. Offensive diarrhoea or large volumes of fluid entering a stoma bag are a social disability which can be reduced by treatment.
What are the different types of resection and their consequences?
Mid-small bowel resection – This type of resection is most commonly performed for vascular occlusion. The terminal ileum often remains and it is this part of the gut which has the greatest capacity for adaptation. Retention of the colon allows sodium absorption and probably promotes ileal adaptation. Such patients suffer least from extensive resection and are usually able to lead normal lives with minimal or no treatment once adaptive changes have occurred after a few months.
Distal ileum and proximal colon – This is a common type of resection, especially for Crohn’s disease. The patients may develop diarrhoea due to the entry of bile salts into the colon. Vitamin B12, 1000 mcg, is needed by injection every 2 months. The diarrhoea may be helped by cholestyramine but few patients tolerate this unpalatable powder for long periods. Treatment on a long-term basis with a drug such as loperamide may be helpful. Major nutritional sequelae are uncommon.
Distal jejunum and ileum – Such patients are left with 200 cms or less of jejunum anastomosed either to a small length of distal ileum or directly to colon. Water soluble nutrients are mostly absorbed by the upper jejunum but some complex polysaccharides and fat enter the colon. Little, if any, jejunal adaptation occurs.
If residual jejunum is less than 50 cms – Long term TPN is mandatory.
If residual jejunum is more than 50 cms – Oral supplements. Sodium losses are minimised by colonic absorption.
These patients are liable to development of urinary oxalate stones by two mechanisms –
a) Calcium is unavailable to bind to the oxalate as it is used to bind with fatty acids to form soaps.
b) Colon absorbs the excess oxalate.
Patients should be advised to take low fat, low oxalate diet and keep a high urine volume. A low fat diet also reduces the volume and offensive nature of the stools and decreases the loss of magnesium and calcium.
All the small and large intestine distal to the proximal jejunum – This is sometimes needed in Crohn’s disease and less commonly for other conditions such as desmoid formation in FAP. The patient has a high output jejunostomy.
Jejunal mucosa is more permeable than ileal or colonic mucosa. Water moves into the lumen, in response to a hyper-osmolar load to maintain isotonicity. Sodium movements depends on conc gradient. There is very little electrical gradient. Sodium absorption is also coupled to glucose (and some amino acids) absorption.
After a meal, in a normal subject, the food is diluted two or three-fold by digestive juices and it is only past 100 cms of jejunum that the volume starts to decrease progressively. Thus patients with high jejunostomy are liable to have a high output. Even when fasting, there is an obligatory stomal loss. Such a patient is thus in permanent negative fluid and sodium balance.
a) Electrolyte balance – Due to its physiological characteristics the jejunum absorbs sodium only if the luminal concentration exceeds 90 mmol/litre and there is a linear relationship between output with volume of effluent. If water or dilute sodium containing solutions are taken by mouth sodium equilibrates in the upper intestine to a concentration of 90 mmol/l so that more sodium leaves the body than is taken in – water and dilute solutions literally wash sodium out of the body in a patient with a high jejunostomy. Such patients are therefore advised to sip a sodium-glucose replacement solution at frequent intervals during the day. Convenient and reasonable palatable formulation are:
|
Sodium chloride 3.5 gms (60 mmol) |
Sodium chloride 7 gms (120 mmol) |
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Sodium citrate 2.9 gms (30 mmol) |
Glucose 8 gms (44 mmol) |
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Glucose 20 gms (110 mmol) |
Water to 1 litre |
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Water to 1 litre |
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The patient can make up the solution from its ingredients using simple measuring spoons.
As already described, certain patients whose jejunostomy output exceeds 2-3 litres daily cannot maintain sodium balance despite these measures and regular intravenous supplements are necessary.
Drug therapy can reduce the stoma output. Codeine phosphate and/or loperamide can reduce losses by about 20% but cannot change a patient in permanent negative sodium balance (a ‘secretor’) into an absorber. Similarly octreotide, or gastric anti-secretory drugs such as omeprazole or H2 blocker, can reduce output by ‘secretors’ but they do not avoid the need for intravenous supplements when necessary. Such drugs taken before meals are sometimes useful socially as a way of reducing an inconveniently large stomal output after eating.
Many patients with high jejunostomy develop magnesium deficiency. An oral supplement of magnesium oxide, given as capsules each containing 4 mmol of magnesium, 12-24 mmol in total daily, often maintains balance.
b) Nutrients – Nutrient absorption can be promoted by an increased oral intake. This can sometimes be achieved if absorption from the short length of residual intestine is maintained throughout the 24 hours by giving food by day and a nasogastric tube feed at night. There is no evidence that an elemental or hydrolysed diet is better absorbed than a whole protein diet. Fat restriction does not appear necessary in a patient with a high jejunostomy. The excess fat is the stoma bag is not offensive. A constant proportion of the fat is absorbed and thus if more fat is eaten, more of this energy-rich nutrient is absorbed. Some cannot maintain nutrition despite oral supplements and for them long-term TPN is needed.
c) Volume of effluent – The volume increases with oral intake. These patients naturally wish to eat to maintain social life. A balance has sometimes to be struck between food intake and the disability of a high stomal output. The patient takes small meals with friends and family and thus reduces stomal output to an acceptable level; the nutritional deficit has to be made up with parenteral supplements.
Further research is needed into intestinal growth factor which might promote increased absorption and into surgical measures for increasing the length of intestine, with or without transplantation.