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Blind Loop Syndrome
Introduction
Blind loop syndrome occurs when part of the small intestine is bypassed and cut off from the normal flow of food and digestive juices.
The bypassed portion of intestine, known as a blind loop, initiates a cascade of problems. Because food can't pass through the loop, it ferments, encouraging bacterial growth. The bacteria then interfere with absorption of essential nutrients, often leading to diarrhea, weight loss and malnutrition.
Blind loop syndrome— sometimes called stasis syndrome or stagnant loop syndrome — often occurs as a complication of abdominal surgery. But blind loop syndrome can also result from structural defects and some diseases. Although blind loop syndrome occasionally requires surgery, most people respond well to antibiotics.
Signs and symptoms
Because blind loop syndrome affects digestion and absorption, signs and symptoms of the disorder often include:
- Loss of appetite.
- Abdominal pain.
- Nausea.
- Fatty stools (steatorrhea) — frothy, foul-smelling stools indicating poor fat absorption.
- Bloating.
- An uncomfortable feeling of fullness after eating.
- Diarrhea.
- Unintentional weight loss.
Although digestion begins in your mouth, the real work of breaking down and absorbing nutrients takes place in your small intestine, the longest section of your digestive tract. Connecting your stomach and large intestine, your small intestine is where food mixes with digestive juices from your pancreas, liver and gallbladder, and where small nutrient molecules — amino acids from proteins, monosaccharides from carbohydrates and most fats — are absorbed into your bloodstream.
Unlike your large intestine, which has millions of bacteria to help break down indigestible fiber, your small intestine normally contains relatively few microorganisms. Because your small intestine is rich in enzymes, it doesn't need the enzymatic action of bacteria; in fact, stomach acid and secretions from your liver and pancreas actually act as antibacterial agents. What's more, the strong muscular contractions (peristalsis) that propel food through your small intestine prevent bacteria from colonizing there.
But in blind loop syndrome, food can't move through the bypassed section of bowel, and the stagnant food becomes an ideal breeding ground for microorganisms — a condition called bacterial overgrowth syndrome. The bacteria may produce toxins as well as interfere with the absorption of nutrients.
What triggers blind loop syndrome
A blind loop can be an inadvertent consequence of gastric surgery, such as Billroth II or Roux-en-Y procedures for ulcers and gastric bypass surgery for obesity. Operations on the small intestine and structural abnormalities sometimes can cause blind loops as well. And a number of medical conditions can lead to bacterial overgrowth, including Crohn's disease and scleroderma and diabetes, which can slow the rate at which food moves through the intestine.
Treatment
Whenever possible, doctors treat blind loop syndrome by dealing with the underlying problem — surgically repairing a postoperative blind loop or stricture, for example. But, the blind loop can't always be reversed. In that case, treatment focuses on correcting nutritional deficiencies and eliminating bacterial overgrowth.
For most people, the best way to treat bacterial overgrowth is with antibiotic therapy, and doctors may start this treatment even when test results are inconclusive. A short course of antibiotics often significantly reduces the number of abnormal bacteria, but because bacteria can return when the antibiotic is discontinued, the therapy may need to be long term.
Doctors also may switch among different drugs to help prevent bacterial resistance. Ironically, because antibiotics wipe out most intestinal bacteria — both normal and abnormal — they can cause some of the very problems they're trying to cure, including diarrhea and an imbalance of bacteria in the digestive tract.
Nutritional support
Addressing nutritional deficiencies is a crucial part of treating blind loop syndrome, particularly in people with severe weight loss. But although malnutrition can be treated, the damage it causes can't always be reversed.
The following measures may improve vitamin deficiencies, reduce intestinal distress and help with weight gain:
- Nutritional supplements. People with blind loop syndrome need intramuscular injections of vitamin B-12 as well as oral vitamin and iron supplements.
- Lactose-free diet. Damage to the intestine may cause some people to lose the ability to digest milk sugar (lactose). In that case, it's important to avoid most lactose-containing products including milk and cheese, or use lactase preparations such as Lactaid that aid in digestion of milk sugar. Some people may tolerate yogurt because the bacteria used in the culturing process naturally breaks down lactose.
- Medium-chain triglycerides. Trigylcerides are a type of fat consisting of a molecule of glycerol to which three hydrocarbon chains are attached. The chains vary in length, and the way your body processes triglycerides depends on the length of the chains. Most dietary fats are long-chain triglycerides. Food sources include many vegetable oils and animal fats, all of which are emulsified and absorbed in the small intestine. On the other hand, medium-chain triglycerides, found in coconut oil, are absorbed without the aid of digestive enzymes. Because they're more readily digested by people with blind loop syndrome, medium-chain triglycerides are sometimes prescribed as a dietary supplement.
Information obtained from National Institute of Health