The short bowel
syndrome occurs from massive small intestinal resection leaving less than
200 cm (6.5 feet) of small bowel. The leading cause of the short bowel
syndrome in adults is Crohn's disease, accounting for 58-77% of patients in
published series (1). Other causes include mesenteric infarction,
radiation enteritis, and volvulus. More cases are surviving because
of improved surgical techniques, post-operative care, and increasing experience
with nutritional management, including long-term parenteral nutrition. Between
10-20,000 patients in the United States are on home parenteral nutrition for
this syndrome.
The severity of disease depends on the location and extent
of the resection:
Patients with limited ileocolic resections (frequently Crohn's
patients) don't have severe problems. Diarrhea in a patient with
a preserved ileal length of >100cm is usually due to bile salt induced
colonic secretion. Such patients benefit from treatment with a bile-acid
binding resin such as cholestyramine. Diarrhea in patients with <100cm
of ileum remaining may have steatorrhea secondary to a reduced bile acid
pool. Hepatic synthesis of bile acids cannot keep up with intestinal
loses. Diarrhea is due to the malabsorbed fatty acids which stimulate
colonic secretion. These patients benefit from a low fat diet with supplements
of medium chain triglycerides which do not require bile salts for absorption.
Ox bile supplements have also been tried. The use of quantitative fecal
fat collections are crucial to accurately assess the mechanism for the diarrhea.
If the diarrhea is secretory (no osmotic gap and no steatorrhea) then cholestyramine
is used. If the diarrhea is osmotic (osmotic gap and steatorrhea present)
then low fat diet is warrented.
Most severly affected patients fall into either of two catagories
(Visual):
1 - ileum and some of the jejunum resected, usually leaving
a jejunocolic anastomosis. This is like the situation with
our patient, but we believe that the original ileocecal valve is intact.
She apparently has about 100cm of small bowel but the mucosa may be abnormal
because of radiation. Both bile salt diarrhea and bile salt deficiency
are possible. The patient could not comply with stool collections for
quantitative fecal fat. A trial of cholestyramine did not decrease diarrhea.
2 - colon, ileum and some of jejunum resected, leaving
a jejunostomy. Messing studied absorption and fecal caloric losses
in ten patients with the "very" short bowel syndrome.
The mean small intestinal length was 75 cm. Seven patients had remaining
colon. Five patients maintained a stable weight on only oral intake
but had caloric intake 2.5 times their basal energy expenditure.
The other five patients required parenteral nutrition. The coefficient
of carbohydrate absorption (79%) was significantly higher than the coefficient
of protein (61%) or fat absorption (52%). This is in part due to
the fact that malabsorbed carbohydrates are fermented by colonic bacteria
to short chain fatty acids which are easily absorbed and can provide energy.
This illustrates the importance of preserving as much viable intestine
(small bowel and colon) as possible during resection. In health, 90% of
nutrients are digested and absorbed in the first 100 cm of jejunum. This
length is crucial in determining the prognosis after resection. If this
length is exceeded and there is a jejunostomy, then the main problem is
fluid and electrolyte management. If this length is exceded and there
is a colon, then the main problem is fat malabsorption due to bile salt
deficiency. If less than 100 cm of jejunum is left, all substrates are
potentially malabsorbed and management must be carefully individualized.
Besides malabsorption of carbohydrate, protein, and fat, the
physiologic consequences of small bowel resection include gastric hypersecretion,
gastric emptying disorders, fluid and electrolyte losses, malabsorption of
vitamins,minerals and bile salts, oxylate hyperabsorption, and bacterial overgrowth.
In any given patient, the cause of diarrhea may be decreased absorptive surface
area, or a combination of bile salt malabsortion, bacterial overgrowth, inactivation
of pancreatic enzymes by gastric acid, lactase deficiency, or nutritional
deficiency itself. Frequently encountered nutritional deficiencies include
iron, calcium, magnesium, phosphorus, potassium, bicarbonate, zinc, vitamin
B12, folate, and the fat soluble viamins A, D, E, and K. Sorting out the problems
and planning management usually involves measuring these specific nutrients
and stool volume and fecal fat. In our patient most of these substances
were measured and there was evidence of deficiency of magnesium, phosphorus,
and folate. Magnesium (along with calcium) is absorbed in the proximal small
intestine under the influence of vitamin D. It should be adequate in this
patient. However, magnesium and calcium are malabsorbed with increasing steatorrhea,
so a low fat diet should help our patient maintain adequate absorption of
magnesium and calcium. Phosphorus deficiency can follow magnesium deficiency
because of muscle breakdown. The folate deficiency may reflect poor dietary
intake or radiation induced small bowel injury not apparent on endoscopy and
biopsy. It is apparent that the most severe problem is protein-calorie malnutrition.
Medical management of the patients falls into three stages:
1. Management in the immediate post-op period:
In the immediate post-op phase, most patients are kept NPO
and are supported with TPN. The major challenge is fluid and electrolyte management.
Careful monitoring of weight and volume status and management of stomal, fecal,
and urinary losses of water, sodium, and potassium is necessary to ensure
optimal electrolyte and water balance. Fluids should be infused to match
loses including an estimated insensible loss of 300 to 500 ml and to maintain
a daily urine output of at least 1 liter. H2 receptor blockers or PPI
are given intravenously to suppress gastric acid hypersecretion. Acid load
presented to the small intestine may contribute to reduced intestinal transit
time, decreased absorption, enzyme inactivation and fluid or electrolyte imbalance.
Cimetidine has been shown to significantly reduce the hydrogen ion output
and fluid output and to improve absorption in this setting. Other
agents that have been shown to slow intestinal transit and decrease diarrheal
volumes include proton pump inhibitors and octreotide. Patients are
maintained on TPN as enteral feeds are initiated.
2. Management in the late post-op phase:
Oral feeding is begun in the late postoperative phase, when
bowel motility has returned. Patients with extensive resections may have
reduced oral intake for up to 10 days to allow healing of enteric anastomoses.
This is balanced with the need to stimulate small bowel adaptation with oral
feeds. Patients with jejunal length > 150cm and those with colon in
continuity are fed after 3-5 days with a liquid polymeric diet, either sipped
or as a continuous nasogastric drip, to maximally utilize the available absorptive
surface area. Patients with a high jejunostomy are often started on an
oral isotonic glucose-saline solution sipped throughout the day or administered
24 hours a day through a nasogastric tube to stimulate jejunal electrolyte and
water absorption. These patients are warned against consuming water and
any drink with a low sodium content because they cause jejunal sodium and water
secretion and an increase in stomal losses. Sports drinks are not a ideal
fluid and electrolyte supplement because of their low (about 20 meq/L) sodium
concentration and osmolarity. This tends to pull electrolytes out of the bowel
mucosa, especially in a very leaky jejunum. Oral nutrient intake is a prerequisite
for induction of adaptive changes. Intestinal adaptation occurs following
small bowel resection and involves both structural and functional changes that
increase nutrient and fluid absorption. The adaptive changes depend on the presence
of food and biliary and pancreatic secretions in the intestinal lumen.
The adaptive changes may take 1 to 2 years to fully develop. As enteral
food intake is increased and caloric and nutrient needs are met then parenteral
nutrition may be reduced and then discontinued.
3. Management in the outpatient setting of patients with
short bowel:
Many patients with extensive resections (100-200 cm remaining)
will require home TPN for some time. The optimal enteral diet composition
for patients with short bowel syndrome has been debated, but a low-fat, high-carbohydrate
diet is of documented advantage in patients with a colon in continuity.
In eight such patients, the energy absorption increased from 49% on a high-fat,
low-carbohydrate diet to 69% on a low-fat, high-carbohydrate diet. A lactose
free diet is recommended. Low fat diets are not very palatable. Although the
case can be made for elemental diet, studies have shown no difference in caloric
absorption, stomal output, and electrolyte loses between an elemental, a polymeric,
and a normal diet in patients with a short bowel without a colon. Comparable
data are not available for short bowel with a colon. Patients are encourage
to eat small frequent meals similar to those recommendations given for patients
with post-gastrectomy dumping syndrome. Fat-soluble vitamins and B 12 usually
must be supplemented. Appropriate mineral and trace elements must be assessed
and replaced if deficient. Our patient was given a low fat, high carbohydrate
diet with loperamide to slow transit and increase absorption. She was instructed
to take small frequent feedings with no water during feeds. A trial of octreotide
and cholestyramine were performed sequentially with no apparent benefit. Medium
chain triglyceride (MCT oil) was given to maximally tolerated doses to provide
caloric supplementation. Small daily doses of potassium and magnesium gluconate
(not enough to exascerbate the diarrhea) were given along with Vitamin D 50,000
units twice weekly. Monthly B12 injections, daily Vitamin A (1000 retinol equivalents)
and Vitamin E (8 mic. gm) were given. The patient was instructed to take ad
lib oral rehydration solution for fluid and electrolyte supplementation. With
this regimen the patient began to gain weight at the rate of 1-2 pounds per
month with minimal diarrhea. Albumin increased to 1.9 in three months. If weight
gain is not satisfactory, enteral feeding will be administered continuously
at night through an N-G tube or a PEG tube.
4. Management of complications seen in patients with the
short bowel syndrome;
Gallstones: Interruption of the enterohepatic circulation
of bile acids by ileal resection results in a decrease of hepatic bile acid
secretion and an altered composition of hepatic bile in terms of the organic
components; bile acid, cholesterol, and phospholipids. Hepatic bile becomes
supersaturated with respect to cholesterol with subsequent formation of cholesterol
gallstone. A prevalence of 44% of asymptomatic gallstones was documented
in a study of 84 patients with severe short bowel syndrome. Symptomatic
gallstones are managed by surgical intervention.
Kidney stones: Most oxalate in food is usually precipitated
out as calcium oxalate in the intestinal lumen and lost in the stool.
Unabsorbed long-chain fatty acids compete for available calcium. Consequently,
a larger amount of free oxalate gets to the colon and is absorbed and ultimately
excreted in the kidney. These patients may develop hyperoxaluria and calcium
oxalate kidney stones. Patients without colon are not at increased risk.
Treatment of hyperoxaluria consists of restriction of oxalate containing products
(tea, chocolate, cola beverages, certain fruits, and vegetables). If hyperoxaluria
persists then calcium supplements should be given. The extra calcium precipitates
dietary oxalate. It may be given as calcium citrate. Citrate helps prevent
stone formation in the urine.
Bacterial overgrowth: Patients who have altered
intestinal anatomy and especially those with no ileocecal valves but with a
preserved colon are at high risk for the development of bacterial overgrowth.
Antibiotics should be given. In our patient there is a Bilroth II gastrojejunostomy
so a blind loop situation with bacterial overgrowth is also possible. A daily
quinolone antibiotic was prescribed.
Other important management issues in the treatment of patients
with short bowel syndrome:
Intestinal transplantation is still at an experimental stage
and is only being performed at a few centers in the United States. The
main indication has been severe short bowel syndrome complicated by progressive
liver disease. Overall mortality from transplantations 30%(12).
The major causes of death are infection, post-transplant lymphoma, and rejection.
Our patient was placed on a low oxylate diet and given
elemental calcium 500 mg tid (as calcium citrate).
