Short Bowel Syndrome in Adults

What is short bowel syndrome?

Short bowel syndrome (SBS) occurs when your body can't absorb enough fluids and nutrients because part of your small intestine is missing or isn't working correctly. How much bowel remains — and, importantly, which part of the bowel remains — determines how your body absorbs nutrients and whether you may eventually be able to reduce or stop parenteral nutrition (PN/TPN) over time.

What causes short bowel syndrome in adults?

In adults, SBS most often results from surgical removal of part of the small intestine due to:

• Complications from Crohn's disease
• Volvulus (a twisted bowel)
• Mesenteric ischemia or other vascular injury or disease
• Thrombosis (blood clots)
• Post-operative complications, particularly after weight-loss surgery
• Certain cancers, such as neuroendocrine tumors
• Trauma
• Radiation damage (radiation enteritis)
• Intussusception — one part of the intestine folds into another, like a collapsible telescope
• Functional causes, such as motility disorders including chronic intestinal pseudo-obstruction (CIPO)

How is short bowel syndrome diagnosed?

Your team may use several tests to confirm the diagnosis, rule out other GI conditions, and assess your nutritional status:

• Medical history — review of your surgical and medical background
• Physical exam — checking for signs of malnutrition, such as decreased muscle mass or vitamin and mineral deficiency signs
• Bloodwork — vitamin, mineral, and electrolyte levels, liver function, and blood counts
• Fecal fat test — checks for fat in the stool, a sign of malabsorption
• Abdominal X-ray — to view dilated bowel or possible obstruction
• Upper GI series (barium swallow) — uses X-ray and fluoroscopy (real-time moving X-ray) to look for narrowing or widening in the intestine
• Abdominal CT scan — assesses for obstruction and other bowel changes
• Endoscopy or colonoscopy — assesses inflammation and remaining bowel length

Complications of short bowel syndrome

Your AIRI team will monitor for these complications and adjust your care plan accordingly. They include malnutrition; electrolyte imbalances and dehydration; vitamin and mineral deficiencies; small intestinal bacterial overgrowth (SIBO); gastric acid hypersecretion; kidney stones; steatorrhea (fat in the stool); osteoporosis and metabolic bone disease; acidosis; and long-term TPN complications such as infection, blood clots, and liver damage. The sections below explain each in more detail.

Dehydration

High output and diarrhea are common in SBS and can lead to dehydration.

Electrolyte imbalances

Electrolytes are electrically charged minerals your body needs to function. The most important ones to monitor include:

• Sodium (Na+)
• Potassium (K+)
• Magnesium (Mg2+)
• Calcium (Ca2+)
• Chloride (Cl-)
• Phosphorus/phosphate (PO4-)

With excessive diarrhea, imbalances can develop quickly and become serious. A simple blood test checks your levels. Treatment may include oral rehydration solutions, IV fluids, IV supplements, or adjustments to your TPN formula if you're on parenteral nutrition.

Vitamin and mineral deficiencies

Which deficiencies you're at risk for depends on the length and location of the intestine that was removed. If your ileum is missing, absorption of fat-soluble vitamins A, D, E, and K is often insufficient.

Vitamin	Deficiency can cause
Vitamin A	Problems with night vision
Vitamin D	Issues with proper bone formation and growth
Vitamin E	Loss of voluntary muscle coordination (ataxia), tingling sensations (paresthesia), or visual disturbances
Vitamin K	Prolonged bleeding and easy bruising
Vitamin B12	Only absorbed in the terminal ileum — if this section is missing, lifelong supplementation is required

You may need supplementation of these and other vitamins and minerals, as determined by your team.

Small intestinal bacterial overgrowth (SIBO)

SIBO happens when bacteria that are normally kept in check grow out of control, leading to diarrhea, bloating, gas, and/or nausea. In a healthy bowel, bacteria are controlled by:

• Intestinal motility — movement through the intestine prevents bacterial buildup; many SBS patients have impaired motility, increasing SIBO risk
• Stomach acid — normally helps kill bacteria, but many SBS patients need anti-acid medications for gastric hypersecretion, which allows more bacterial growth
• The ileocecal valve — normally prevents bacteria from flowing backward from the colon into the small intestine

Signs and symptoms: nausea, gas and bloating, malabsorption, increased diarrhea or ostomy output.

Why it matters: SIBO can increase fluid losses and damage bile salts needed for fat and fat-soluble vitamin absorption. Treatment is usually a 7–14 day course of antibiotics, as determined by your team.

Gastric acid hypersecretion

When a large portion of the small bowel is lost, the signal to stop stomach acid production is also lost, resulting in excess acid. This needs treatment because stomach acid deactivates important pancreatic enzymes, increases stool output, and damages the lining of the esophagus and intestine.

Kidney stones

If you have SBS and still have your colon, you may be at risk for oxalate-calcium kidney stones. Oxalate is found in plant-based foods; normally it binds to calcium in the intestine and is passed in stool. When fat malabsorption occurs, fat binds with calcium instead, leaving oxalate free to be reabsorbed into the bloodstream — where it can reach the kidneys, bind with calcium, and form stones.

Prevention:

• Avoid foods high in oxalate: tea, chocolate, nuts, leafy green vegetables, berries, wheat germ and bran
• Stay well hydrated
• Increase dietary calcium if tolerated, or take calcium supplements if recommended

Steatorrhea (fat in the stool)

Normally, dietary fat combines with bile salts made by the liver and is reabsorbed in the terminal ileum. Many SBS patients are missing this section (especially if more than 100 cm / 3.3 ft of ileum was removed), so bile salts continue to be lost. The liver can't keep up with production, bile salt supply runs low, and fat passes through unabsorbed — producing greasy, foul-smelling, floating, grey-colored stool.

Treatment:

• Diet — sometimes a low-fat diet alone resolves the problem
• Bile acid sequestrants (binders) — if you have an intact colon, unabsorbed bile salts reaching the colon can irritate its lining and worsen diarrhea. Medications like cholestyramine reduce this by increasing bile acid removal from the body — though they can interfere with absorption of fat-soluble vitamins and essential fatty acids, so your team will monitor your nutritional status closely

Osteoporosis and metabolic bone disorders

Bone disease is common in SBS due to malnutrition, vitamin and mineral deficiencies, long-term TPN use, and certain medications (such as steroids used for underlying conditions). Metabolic bone disease can range from:

• Osteomalacia (caused by severe vitamin D deficiency)
• Osteopenia
• Osteoporosis

A DEXA (bone density) scan is usually recommended for adults with SBS. Treatment generally includes vitamin D and calcium supplementation, adequate sun exposure, and weight-bearing physical activity. Your team may prescribe an IV osteoporosis medication if absorption is a concern.

Acidosis

Acidosis results when too much lactic acid builds up in the bloodstream. In some SBS patients, carbohydrates aren't digested well; intestinal bacteria then break down the undigested carbohydrate, producing lactic acid that enters the bloodstream. In large amounts, this causes acidosis.

This guide was prepared by the Advanced Intestinal Rehabilitation Institute (AIRI) for patient education purposes. It is not a substitute for medical advice from your care team. If you have questions about your specific condition, diet, medications, or symptoms, please contact your AIRI care team directly.