Blind Loop Syndrome

Blind loop syndrome occurs when food bypasses or stalls in a part of your intestines during digestion. This causes a buildup of bacteria (SIBO), making you feel sick. Antibiotics and surgery are the most common treatments.


What is blind loop syndrome?

Blind loop syndrome occurs when food doesn’t move normally through a section (“loop”) of your intestines during digestion. Stagnant food can lead to bacterial overgrowth in your gut. The overgrown bacteria can make you feel sick and lead to weight loss and nutritional problems. Blind loop syndrome is also called stasis syndrome and stagnant loop syndrome.

Blind loop syndrome is often the result of surgery on your stomach or intestines. Surgery can cause complications, such as scar tissue or slow motility through your intestines, which lead to food building up in one area. Sometimes, surgery intentionally bypasses a section of your intestines. This gives food in your intestines less time to be properly broken down and absorbed.


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How does blind loop syndrome affect digestion?

Digestion is your body’s process of breaking down food and absorbing nutrients for energy. Food moves from your stomach to your small intestine and from there into your large intestine, which includes your colon, rectum and anus. Food then leaves your body as waste (poop).

Your body absorbs most of the nutrients from food in your small intestine. But if you have blind loop syndrome, your digestive process doesn’t work as it should. Food bypasses part of your small intestine and may get stuck in your digestive tract. So, it doesn’t get fully broken down or absorbed. This gives bacteria more opportunity to feed on it and multiply.

What’s the difference between blind loop syndrome and small intestinal bacterial overgrowth (SIBO)?

Blind loop syndrome is one way that SIBO (small intestinal bacterial overgrowth) can occur. The overgrowth of bacteria in your small intestine is what causes the symptoms of blind loop syndrome. SIBO can also occur from chemical imbalances in your gut, but blind loop syndrome causes SIBO for structural reasons. Bacteria overgrow because a section of your intestine is stagnant.


Who gets blind loop syndrome?

Blind loop syndrome is most common in people who have had gastrointestinal surgeries or weight loss surgeries that shorten or reroute some of their digestive tract. It may be the result of:

Blind loop syndrome can also be a complication of gastrointestinal diseases that affect your motility. Motility is the movement of food through your digestive tract. Examples of these disorders include:

Other diseases that might affect motility and lead to blind loop syndrome include:

Finally, blind loop syndrome might occur after an intestinal injury or if you develop a gastrointestinal fistula (an abnormal opening between your stomach and intestines).

Can children get blind loop syndrome?

Children can get blind loop syndrome. They may develop the condition after gastrointestinal surgery, just like adults. But some children are born with abnormalities in their gastrointestinal tract that can lead to blind loop syndrome. Examples include:


Can blind loop syndrome be fatal?

Blind loop syndrome isn’t usually fatal. Most people’s symptoms improve with treatment. But in rare cases, serious health complications can develop from untreated blind loop syndrome. The disease can put you at risk of gastrointestinal perforation, a hole or tear in your small or large intestine. Bowel perforation is a potentially life-threatening condition.

How common is blind loop syndrome?

Blind loop syndrome is rare. Symptoms can be similar to those of other more common gastrointestinal disorders, so it often goes undiagnosed or misdiagnosed. In addition, symptoms of blind loop syndrome may not appear until years after gastrointestinal surgery.

Symptoms and Causes

What are the symptoms of blind loop syndrome?

The most common symptoms of blind loop syndrome include:

What causes blind loop syndrome?

The most common cause of blind loop syndrome is gastrointestinal surgery. Any procedure that shortens or reroutes part of your bowel (small and large intestine) can cause the condition.

A good example is partial gastrectomy. When a surgeon removes part of your stomach, they attach the remaining part to a section of your small intestine. This creates a new pathway for food to enter your small intestine. But to do this, they have to detach and close off the upper part of your small intestine from your stomach. This creates a “blind loop,” a kind of dead-end street that can disrupt digestion.

Bacterial overgrowth in your small intestine can affect lots of digestive functions, including:

  • Bile salts: Overgrown bacteria in your small intestine may consume the bile salts you need for digestion. Bile salts help your body digest fat. If the bile salts don’t work correctly, your body can’t absorb fat or fat-soluble vitamins. That’s why blind loop syndrome can cause unexplained weight loss and fatty stools.
  • Vitamin B12 absorption: The bacteria use up the vitamin B12 found in food, so your body doesn’t absorb enough. Vitamin B12 deficiency can cause megaloblastic anemia.

Diagnosis and Tests

How is blind loop syndrome diagnosed?

Your healthcare provider will do a physical exam. They may press on your stomach to check for tenderness, swelling or masses. Gastrointestinal exams for blind loop syndrome may include:

Management and Treatment

How is blind loop syndrome treated?

Treatments for blind loop syndrome include:

  • Antibiotics: Antibiotics are the most common treatment for blind loop syndrome. These medicines destroy the overgrowth of bacteria and clear up infections. Most people start absorbing nutrients again after a few weeks or months of antibiotics.
  • Dietary changes: Eating foods high in protein, calories and healthy fats can help you regain weight. Talk to your healthcare provider about maintaining a healthy weight for you.
  • Surgery: Antibiotics treat the effects of blind loop syndrome, but they don’t address the underlying problem. You may need surgery to fix the problem in your intestines permanently.
  • Vitamin supplements: Your healthcare provider may recommend vitamin B12 supplements if you have vitamin deficiency anemia or any nutritional shortages.

Does blind loop syndrome always require treatment?

Blind loop syndrome requires treatment. The bacterial overgrowth won’t go away on its own. In fact, the problem will probably get worse over time and may lead to more serious health complications. So, even if your symptoms are mild, it’s important to get the right care.

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How can I prevent blind loop syndrome?

There’s no way to prevent blind loop syndrome. But if you need gastrointestinal surgery, ask your healthcare provider how the procedure will be performed. Find out if there’s a risk of developing blind loop syndrome.

If I’ve had gastrointestinal surgery in the past, will I get blind loop syndrome?

If you’ve had gastrointestinal surgery in the past, it’s pretty unlikely that you’ll develop blind loop syndrome. But even long-ago surgery increases your risk. Keep an eye out for digestive problems and talk to your healthcare provider right away if you notice anything abnormal.

Outlook / Prognosis

What’s the outlook for someone with blind loop syndrome?

Medical treatment with antibiotics and surgery are usually very effective treatments for blind loop syndrome. The issue does return in some people.

What are the possible complications of blind loop syndrome?

Blind loop syndrome usually improves with treatment. But if it’s left untreated for a long time, possible complications may include:

Living With

When should I see my healthcare provider about blind loop syndrome?

See your healthcare provider right away if you experience any of the following symptoms, as they could be signs of an intestinal perforation:

What questions should I ask my healthcare provider about blind loop syndrome?

There are a few questions you may want to ask your doctor if you’re diagnosed with blind loop syndrome:

  • Can I ease the symptoms of blind loop syndrome without medication or surgery?
  • Can probiotics help ease the symptoms of blind loop syndrome?
  • Is there a special diet that can reduce the risk of blind loop syndrome coming back?
  • What are the chances that I’ll get blind loop syndrome again after treatment?
  • Will I need surgery for blind loop syndrome?

A note from Cleveland Clinic

If you’re having digestion issues or experiencing gastrointestinal symptoms, talk to your healthcare provider. Make sure to tell them if you’ve ever had any kind of abdominal surgery, even if it was years ago. Chances are that blind loop syndrome isn’t the culprit because it’s not a very common condition. But these symptoms are a sign that something isn’t right, and an accurate diagnosis is the first step toward effective treatment.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 02/23/2023.

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