During a normal, healthy digestive process, food passes through the stomach and into the small intestine. It then enters the large intestine or the colon, where the organ absorbs water and eliminates undigested food. However, if a person has blind loop syndrome, food bypasses the small intestine, which forms a loop, preventing normal digestion. As a result, waste products remain in the digestive tract longer, leading to increased levels of bacteria.

Symptoms of Blind Loop Syndrome

Most people with blind loop syndrome, also called stasis syndrome or stagnant loop syndrome, experience a combination of symptoms including fever and joint pain. These symptoms often last from two to four weeks and recur every four to six weeks. Skin rashes, leg edema, and muscle aches are also common, as is loss of appetite. When the individual does eat, he or she may experience an uncomfortable feeling of fullness afterward. Many people also complain of bloating, nausea, persistent diarrhea, and abdominal pain. Stool may have a pale and oily appearance. Due in part to some of these symptoms, one of the primary signs of blind loop syndrome is rapid, unintentional weight loss. If the symptoms are not addressed, people may exhibit signs of malnutrition as well.

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The Effects of Blind Loop Syndrome

The small intestine is around 20 feet long, and a blind loop makes this organ shorter than average. The severity of the effects increases depending on the amount of intestine included in the blind loop. The greater the length of the blind loop, the greater the chance of serious bacterial overgrowth, toxin production, and intestinal stagnation. These increased levels of bacteria also prevent the body’s absorption of nutrients such as vitamin B12. Instead, the body passes them out of the system as waste products.

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Why Vitamin B12 Deficiency Matters

High levels of bacteria in the blood use up the body’s supply of vitamin B12. The lack of sufficient levels is a serious side effect of blind loop syndrome. It prevents the body from producing red blood cells, which leads to anemia, which can be serious. These red blood cells carry oxygen and nutrients to the body. Nerve function relies on ample levels of vitamin B12 for the brain and spinal cord to function properly. Eventually, inadequate levels will affect a person’s ability to think. A vitamin B12 deficiency may also affect the extremities, which in turn affect sensation and muscle strength. Those with a vitamin B12 deficiency may feel fatigued or experience a tingling or numbness in the hands and feet in the early stages.

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Bacteria That Cause Blind Loop Syndrome

The three primary types of bacteria identified as playing a causative role in the development of blind loop syndrome are

  • Escherichia coli, bacteria that exist in the environment and in foods and the intestines of both humans and animals. Although some strains are harmless, others can cause diarrhea and various illnesses.
  • Bacteroides fragilis, a group of anaerobic bacteria that thrive in the human gut, especially the colon. Overgrowth can contribute to blind loop syndrome.
  • Streptococcus species, bacteria that normally live in humans but usually cause no symptoms. People with diabetes, cancer, or liver disease are at a higher risk of infection and blind loop syndrome from overgrowth of the bacteria.

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Other Complications of Blind Loop Syndrome

Because the body cannot absorb nutrients as it should, some people with blind loop syndrome develop regular kidney stones. This is due to their bodys' inability to properly absorb calcium. Without sufficient quantities of this mineral, people are at greater risk of developing osteoporosis. They may also experience deficiencies of folate, iron, and vitamin E. The bacteria present in the small intestine as a result of the blind loop syndrome break down the bile salts needed to digest fats. This prevents the body from completely absorbing vitamins A, D, E, and K which prevents the absorption of fats and causes diarrhea. As the bacteria break down stagnant food, they release toxins that also damage the intestinal lining.

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Risk Factors and Causes of Blind Loop Syndrome

A structural defect in the small intestine may cause blind loop syndrome. In many cases, the condition develops due to a complication following abdominal surgeries such as the bowel-shortening surgery some people undergo to treat obesity. Often, the syndrome occurs between one and six years following a bowel bypass surgery. Other procedures, such as radiation treatments for stomach cancer or ulcers, also raise the risk. Patients treated for wounds to the small intestine and people with diabetes may also develop blind loop syndrome. Additionally, individuals with digestive problems due to diverticulitis, peptic ulcer disease, celiac disease, Crohn’s disease, or colitis have a higher risk.

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To obtain a blind loop syndrome diagnosis, most physicians aim to verify their patient's symptoms. A variety of tests can determine the presence of an infection, as well as the nutritional status of the patient. This includes blood and intestine aspirate cultures. Blood tests can determine whether or not the individual is experiencing iron deficiency and if the organs are functioning at normal levels. Some technicians may perform abdominal X-rays or CT scans. Other tests include barium X-rays to verify the presence of a blind loop or diverticulitis. Quantitative fecal tests reveal how well the small intestine is absorbing fat and how slowly the food is moving.

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Breath Tests

Breath tests are effective, noninvasive methods of diagnostic testing that can note the presence of small intestinal bacterial overgrowth (SIBO), which causes blind loop syndrome. There are three types: the hydrogen breath test, the D-xylose breath test, and the bile acid breath test. Hydrogen breath tests measure hydrogen (H2) and methane (CH4) levels in expired breath. Doctors have their patient drink a sugar solution. Then, the individual breathes into a special breath analyzer. Fast-rising hydrogen levels indicate poor carbohydrate digestion and intestinal bacterial overgrowth. D-xylose breath tests are more accurate than hydrogen tests and measure the amount of carbon dioxide in the person’s breath. High levels indicate bacterial overgrowth. Bile acid tests use a bile salt and a radioactive tracer to check for bile salt dysfunction. Bacterial overgrowth interferes with the bile acids created in the liver that aid the small intestine in fat digestion.

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Treatment for Blind Loop Syndrome

In some cases, doctors treat blind loop syndrome by treating the cause. If surgery caused the blind loop, an additional surgical repair usually remedies the issue. In other cases, doctors rely on antibiotic therapy. They will treat nutritional deficiencies, but sometimes long term damage cannot be reversed. Physicians may prescribe supplements, including vitamin B12 injections. Because bacterial overgrowth damages the lining of the intestine, individuals may be unable to tolerate the sugar, lactose, present in milk. In these instances, the doctor will usually prescribe a lactose-free diet.

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The severity of the blind loop syndrome affects the long term prognosis, as does the cause and any associated complications. However, the majority of those who receive antibiotic treatments make a complete recovery. Surgical procedures offer a good prognosis, if they suit the cause. Most people have a normal life expectancy following treatment for blind loop syndrome, although some studies suggest that men may have a slightly lower expectancy due to a higher chance of developing stomach carcinoma as a result.

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