What Is Blind Loop Syndrome?

Blind loop syndrome occurs when part of the small intestine becomes bypassed. The “blind loop” formed by the bypassed intestine means food can’t move normally through the digestive tract. The slowly moving food and waste products become a breeding ground for bacteria, which can lead to a condition called bacterial overgrowth. As a result, nutrients may not be fully absorbed. 

Blind loop syndrome often causes diarrhea and may cause weight loss and malnutrition.

Blind loop syndrome sometimes called stasis syndrome or stagnant loop syndrome often occurs as a complication of stomach (abdominal) surgery. But blind loop syndrome can also result from structural problems and some diseases. Sometimes surgery is needed to correct the problem, but antibiotics are the most common treatment.

The name of this condition refers to the “blind loop” formed by part of the intestine that is bypassed. This blockage does not allow digested food to flow normally through the intestinal tract. 

The substances needed to digest fats (called bile salts) do not work as they should when a section of the intestine is affected by blind loop syndrome. This prevents fat and fat-soluble vitamins from being absorbed into the body. It also leads to fatty stools. Vitamin B12 deficiency may occur because the extra bacteria that form in the blind loop use up this vitamin. 

Blind loop syndrome is a complication that occurs:

  • After many operations, including subtotal gastrectomy (surgical removal of part of the stomach) and operations for extreme obesity
  • As a complication of inflammatory bowel disease
  • Diseases such as diabetes or scleroderma may slow down movement in a segment of the intestine, leading to blind loop syndrome.


Signs and symptoms of blind loop syndrome often include:

  • Loss of appetite
  • Abdominal pain
  • Nausea
  • Bloating
  • An uncomfortable feeling of fullness after eating
  • Diarrhea
  • Unintentional weight loss 
  • Complete intestinal obstruction
  • Death of intestine (intestinal infarction)
  • Hole (perforation) in intestine
  • Malabsorption and malnutrition
Risk Factors

Factors that increase your risk of blind loop syndrome include:

  • Gastric surgery for obesity or ulcers
  • A structural defect in the small intestine
  • An injury to the small intestine
  • An abnormal passageway (fistula) between two segments of bowel
  • Crohn’s disease, intestinal lymphoma or scleroderma involving the small intestine
  • History of radiation therapy to the abdomen
  • Diabetes
  • Diverticulosis of the small intestine


Your doctor will first talk to you about the history of your problems as well as do a physical exam. He or she will want to know about any surgeries you have had before as well as any other medical conditions you have. Your doctor will likely want to check your stool for blood, which involves placing a gloved finger into the anus to remove a very small stool sample to test with an test kit in the office. Your doctor may want to take pictures of your abdomen including an abdominal x-ray or CT scan of the abdomen. Other tests your doctor or gastroenterologist might consider include a special x-ray taken after drink a barium solution that helps light up the small intestine called a barium x-ray. Your doctor may also want to do hydrogen, D-xylose, or bile acid breath tests which help measure the amount of bacteria living in the upper digestive system. All three of these tests involve blowing into a machine that checks levels of different products affected by bacteria living in the bowel. Your doctor may want you to collect a stool sample at home to check for high amounts of fat. Finally, your doctor may want to get a sample of the material in the small intestine by doing an endoscopy (placing a thin tube with a camera at the end down the esophagus, through the stomach, and into the small intestine).

Treatment options for blind loop syndrome include medications, nutritional supplementation and surgery. Antibiotic regimens are designed to eliminate the bacterial overgrowth that is causing symptoms. Antibiotic courses may be short or long but generally need to be repeated as the bacterial overgrowth recurs so long as the underlying problem (the blind loop) is present. Using different antibiotics from time to time helps prevent the creation of bacteria that are resistant to the antibiotic you are using. Because blind loop syndrome causes so many problems with nutrient absorption, certain measures can help with these problems including injections of vitamin B12 and iron.

For some people, modifications of diet may help diarrhea. Sometimes the damage to the wall of the intestine caused by bacterial overgrowth can cause lactose intolerance, so a diet free of lactose can help decrease diarrhea. Another diet option is one high in medium-chain triglycerides (found in foods like coconut oil), which are easily absorbed by the body without the assistance of digestive enzymes in contrast to the long chain triglycerides found in most foods we eat. The only curative option for treatment of blind loop syndrome is surgical repair. Without surgical repair, treatment is aimed at reducing symptoms from blind loop syndrome. You should discuss the best treatment options for you with your doctor, gastroenterologist and/or surgeon.