Blind Loop Syndrome

1 What is Blind Loop Syndrome?

Blind loop syndrome (BLS), sometimes called stasis syndrome or stagnant loop syndrome can often occur as a complication of abdominal surgery, though it may result from structural problems and certain diseases.

BLS occurs when a portion of the small intestine conforms into a loop and digested food slows down or stops passing through this part of the intestine.

The blind loop hinders normal movement of food through the digestive tract.

Sluggish movement of food and waste products contributes to the breeding of bacteria, which results in bacterial overgrowth.

This leads to recurrent diarrhea resulting in weight loss and problems with nutrient absorption (malnutrition).

Antibiotic treatment is the most common treatment modality, although in some cases surgery may be needed to correct the problem.

2 Symptoms

The signs and symptoms of blind loop syndrome often include:

  • Loss of appetite
  • Abdominal pain
  • Nausea
  • Bloating: An uncomfortable feeling of fullness after eating
  • Diarrhea
  • Unexpected weight loss

Bloating, nausea, and diarrhea are common symptoms that may be seen in several intestinal diseases.

Consult your doctor for a complete evaluation, particularly if you have undergone abdominal surgery, and have the following symptoms:

  • Recurrent problem of diarrhea
  • Rapid, unexpected weight loss
  • Pain in the abdomen persisting for more than a few days

If the abdominal pain is very severe, seek immediate medical attention.

3 Causes

 Blind loop syndrome can be caused by:

  • Complications of abdominal surgery, including gastric bypass for obesity and subtotal gastrectomy (surgical removal of a part of the stomach) to treat peptic ulcers and  stomach cancer
  • Structural problems in or surrounding your small bowel, including scar tissue (intestinal adhesions) on the outer surface of the bowel and small, bulging pouches of tissue that protrude through the intestinal wall (diverticulosis)
  • Certain medical conditions, including Crohn's disease, inflammatory bowel disease, radiation enteritis, scleroderma, celiac disease, obesity and diabetes may slow down the movement (motility) of food and waste products through the small intestine

Growth of blind loop

The small intestine measures nearly 20 feet and is the longest section of your digestive tract.

It is in the small intestine that the food gets mixed with digestive juices and nutrients are reabsorbed into your bloodstream.

The small intestine has comparatively less amounts of normal bacteria flora unlike your large intestine (colon).

With blind loop syndrome, the stagnant food in the loop portion of the small intestine acts as an ideal breeding place for the bacteria.

These bacteria produce toxins and use up vitamin B12 as well as hinder the absorption of other nutrients.

The substances required to digest fats called bile salts do not function normally if a section of small intestine is affected by blind loop syndrome.

This prevents absorption of fat and fat-soluble vitamins leading to fatty stools.

The greater the length of small bowel forming in the blind loop, the greater is the chance of bacterial overgrowth.

4 Making a Diagnosis

Testing such as Abdominal X-ray and Abdominal CT scan are performed to make a diagnosis of blind loop syndrome.


List your symptoms, including when they started and how they have undergone changes over a period of time.

Carry your medical records along, specially if you have undergone abdominal surgery in the past, have any known bowel disease, or received radiation to the abdomen or pelvic region.

List all your current medications, vitamins and supplements.

Make a list of your key medical information, including any recent changes or stressful conditions in your life and other conditions.

Make sure you inform your doctor about any abdominal surgery in the past.

Creating a list of questions in advance helps you derive the most out of your time with your doctor.

Some basic questions you may ask your doctor include:

  • What might be the cause of my condition?
  • What treatment modality do you recommend?
  • Are there any side effects of the medications you are prescribing?
  • I have other conditions. How can I manage them?
  • Will I need to take long-term medications?
  • When will my follow-up appointment be scheduled to monitor my progress?
  • Will I need to take any nutritional supplements?
  • Are there any lifestyle changes that should be made to help reduce or manage my symptoms?

Your doctor may ask you a number of questions that include:

  • Have you undergone abdominal surgery in the past?
  • What are your symptoms and when were these first discovered?
  • Do these symptoms get relieved at any point or remain the same?
  • Does your pain feel like a cramp?
  • Is your pain radiating to other parts of your abdomen or to your back?
  • Have you had any unexpected weight loss?
  • Is there any change in your stool?  
  • Do your signs and symptoms include fever or vomiting?
  • What does your regular diet consist of?
  • Have you ever had food allergies or lactose intolerance?
  • What medications do you take, including prescription and over-the-counter medications, vitamins, herbal remedies and supplements?
  • Do you have any family history of bowel disorders or colon cancer?
  • Have you ever undergone radiation therapy to your abdomen or pelvis?


The initial step in the diagnosis of blind loop syndrome is an imaging test, such as:

  • Abdominal X-ray
  • Abdominal CT scan

Additional tests may be done to check for bacterial overgrowth in your small intestine, poor fat absorption, or other problems that may be causing or contributing to your symptoms:

  • Barium X-ray of the small intestine: This test uses a contrast solution such as barium that coats the lining of your intestine and stands out clearly on X-rays. A barium X-ray may show a blind loop, diverticulosis, a narrowing (stricture) of the intestine or other structural problems, as well as slow transit times that can cause bacterial overgrowth.
  • CT enterography: More sensitive than a barium X-ray or conventional CT. It detects inflammation or structural problems in the bowel and abnormalities in other organs such as the pancreas.
  • Hydrogen breath test: This test measures the amount of hydrogen that you exhale after drinking a mixture of glucose and water. A rapid increase in hydrogen is a sign of poor carbohydrate digestion and bacterial overgrowth in your small intestine. Although widely performed, it is less sensitive than other breath tests.
  • D-xylose breath test: This test is more accurate than a hydrogen breath test, and measures the amount of carbon dioxide in your breath. High levels of carbon dioxide suggest bacterial overgrowth.
  • Bile acid breath test: Bile acids produced in your liver help digest fats (lipids) in your small intestine. Bacterial overgrowth hinders this process. This test involves use of a bile salt along with a radioactive tracer to assess bile salt dysfunction.
  • Quantitative fecal fat test: This test can find out how well your small intestine can absorb fat. You are put on a high-fat diet for three days and the amount of fat in your stool is then measured. A large amount of undigested fat may result from bacterial overgrowth, but more commonly it occurs due to other conditions such as short bowel syndrome or chronic pancreatitis.
  • Small intestine aspirate and fluid culture: This is the most sensitive test available to check bacterial overgrowth. In order to collect a fluid sample, doctors insert a long, flexible tube called an endoscope down your throat and through your upper digestive tract into your small intestine. A sample of intestinal fluid is obtained which is then evaluated in a laboratory for the presence of bacteria. If your doctor finds that bacterial overgrowth is likely, he or she may initiate treatment with antibiotics before any specific testing.

5 Treatment

Doctors treat the blind loop syndrome by controlling the underlying problem, for instance, by surgical repair of a postoperative blind loop, stricture or a fistula.

With conditions where the blind loop cannot be reversed, the treatment is focused on correcting nutritional deficiencies and eliminating bacterial overgrowth.

  • Antibiotic treatment: In most cases, the bacterial overgrowth is treated with antibiotics. Doctors may recommend this treatment if your symptoms and medical history suggest this as the cause, even if the test results are inconclusive or sometimes without performing the test at all. Testing may then be performed when antibiotic treatment becomes ineffective. A short course of antibiotics usually reduces the number of abnormal bacteria, but bacteria may reappear when the antibiotics are stopped, so long -term treatment may be needed.  Doctors may advise different antibiotics to help prevent bacterial resistance. Antibiotics kill most of the intestinal flora, both normal and abnormal. As a result, antibiotics can cause problems including diarrhea. Switching between different drugs can manage this problem.
  • Nutritional support: Management of nutritional deficiencies is very important in the treatment of blind loop syndrome, specially in individuals with severe loss of weight. Malnutrition may be treated, but the damage it causes cannot be reversed at all times. These treatments can improve vitamin deficiencies, reduce intestinal distress and help with improve weight gain:
  • Nutritional supplements: Patients with blind loop syndrome may be given intramuscular injections of vitamin B12, as well as oral vitamins, calcium and iron supplements.
  • Lactose-free diet: The small intestinal damage may cause loss of the ability to digest milk sugar (lactose). In such cases, it is very important to avoid most lactose-containing products, or else use lactose preparations that help in digesting milk sugar.
  • Medium-chain triglycerides: Medium-chain triglycerides may be prescribed as a dietary supplement in patients with severe blind loop syndrome resulting in short bowel syndrome as they can easily digest medium-chain triglycerides found in coconut oil.

6 Risks and Complications

The factors that can increase your risk of developing blind loop syndrome include:

  • Gastric surgery performed to treat obesity or ulcers
  • A structural defect of the small intestine
  • An injury in the small intestine
  • An abnormal connection (fistula) between two segments of bowel
  • Crohn's disease, intestinal lymphoma or scleroderma involving the small intestine
  • History of radiation treatment received in the abdominal area
  • Diabetes
  • Diverticulosis of the small intestine

Blind loop syndrome can lead to serious problems such as:

  • Poor fat absorption: Bacteria formed in your small intestine break down the bile salts required in the digestion of fats. As a result, your body cannot completely absorb the fat-soluble vitamins A, D, E and K. This leads to conditions such as diarrhea, weight loss and vitamin deficiency disorders.
  • Damage to the intestinal lining: Toxins released by the bacteria when they act upon the stagnant food can damage the mucosal lining of the small intestine. This results in poor absorption of nutrients such as carbohydrates and proteins causing serious malnourishment.
  • Vitamin B12 deficiency: Bacteria in the small intestine use up the vitamin B12, which is necessary for the proper functioning of your nervous system, the production of blood cells and DNA. A severe vitamin B12 deficiency can cause weakness, fatigue, tingling, numbness in your hands and feet, and in advanced cases, mental confusion. Damage caused to your central nervous system from a vitamin B12 deficiency may be irreversible.
  • Brittle nature of bones (osteoporosis): The damage caused to your small intestine due to abnormal bacterial growth may result in poor calcium absorption, and eventually develop bone diseases such as osteoporosis.
  • Kidney stones: Poor calcium absorption may cause hypercalcemia which can eventually result in kidney stones.