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, leads to a series of problems. Food can't pass through the loop, and digestive fluids stagnate. As a result, food ferments, encouraging bacterial growth and interfering with absorption of essential nutrients. Blind loop syndrome often leads 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.
Because blind loop syndrome affects digestion and absorption of nutrients, signs and symptoms of the disorder often include:
* Loss of appetite
* Abdominal pain
* Fatty stools (steatorrhea) — frothy, foul-smelling stools indicating poor fat absorption
* An uncomfortable feeling of fullness after eating
* Unintentional weight loss
When to see a doctor
Bloating, nausea and diarrhea are signs and symptoms of many intestinal problems, ranging from irritable bowel syndrome to stomach flu (gastroenteritis). For most people, they aren't an indication of blind loop syndrome. But see your doctor for a full evaluation — especially if you've had abdominal surgery — if you have:
* Persistent diarrhea
* Rapid, unintentional weight loss
* Abdominal pain lasting more than a few days
If you have severe abdominal pain, get immediate medical care.
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 measuring about 20 feet (6.1 meters). Connecting your stomach and large intestine, your small intestine is where food mixes with digestive juices from your stomach, 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 (colon), which has billions 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 intestine, 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. The greater the length of small bowel involved in the blind loop, the greater the degree of bacterial overgrowth.
What triggers blind loop syndrome
Blind loop syndrome can be caused by:
* Complications of abdominal surgery. Procedures that may inadvertently cause a blind loop include gastric bypass surgery for obesity, such as the Roux-en-Y procedure, and surgical gastrectomy to treat peptic ulcers and stomach cancer, such as the Billroth II.
* Structural abnormalities of the small intestine. Structural problems in and around your small intestine may lead to bacterial overgrowth. Examples of such defects — which may be inherited or may result from surgery, infection or injury — include bands of scar tissue (intestinal adhesions) on the outside of the bowel and small, bulging pouches of tissue that protrude through the intestinal wall (diverticulosis).
* Bacterial overgrowth associated with certain medical conditions. Health problems that can slow the rate at which food moves through the intestine — including Crohn's disease, scleroderma and diabetes — are associated with an increased risk of a blind loop.
Factors that increase your risk of bacterial overgrowth in the small intestine include:
* Gastric surgery for obesity or ulcers
* A structural defect in or an injury to your small intestine
* An abnormal passageway (fistula) between two segments of bowel
* Crohn's disease, intestinal lymphoma, scleroderma involving the small intestine
* Diverticulosis of the small intestine
A blind loop can cause an escalating series of problems, including:
* Poor absorption of fats. Because bacteria in your small intestine break down (deconjugate) the bile salts needed to emulsify and digest fats, the fat in food as well as the fat-soluble vitamins A, D, E and K aren't well absorbed. This leads to diarrhea and often to steatorrhea — fatty, foul-smelling stools — as well as to weight loss and vitamin deficiency disorders. A lack of vitamin A can cause night blindness, for example, and low levels of vitamin D affect your body's ability to absorb calcium, which can lead to weakened bones and contribute to many other disorders.
* Damage to the intestinal lining. Bacterial overgrowth harms the mucous lining (mucosa) of the small intestine both directly and indirectly. Toxic byproducts that are released when bacteria break down stagnant food damage the mucosa, as do bacterial enzymes. This damage means that most nutrients, including carbohydrates and proteins, are poorly absorbed, leading to serious nutritional deficiencies.
* Vitamin B-12 deficiency. Vitamin B-12, which is essential for the normal functioning of your nervous system and the production of blood cells and DNA, is absorbed in your small intestine. But proliferating bacteria actually use up the vitamin, reducing the amount that's available to your body. A severe deficiency can lead to weakness, fatigue, tingling and numbness in your hands and feet, and, in advanced cases, to mental confusion. Damage to your central nervous system resulting from a B-12 deficiency may be irreversible.
* Brittle bones (osteoporosis). Both calcium and vitamin D, which aids in calcium absorption, are metabolized in your small intestine. Damage to your intestine from abnormal bacterial growth over a long period of time causes poor calcium absorption and eventually may lead to bone diseases such as osteoporosis.
Preparing for your appointment
If you have signs and symptoms that are common to bile loop syndrome, make an appointment with your doctor. After an initial evaluation, you may be referred to a doctor who specializes in the diagnosis and treatment of digestive disorders (gastroenterologist).
Here's some information to help you get ready for your appointment, and what to expect from your doctor.
Information to gather in advance
* Write down your symptoms, including when they started and how they may have changed or worsened over time.
* Bring a list of all your medications, as well as any vitamins or supplements.
* Write down your key medical information, including other conditions with which you've been diagnosed. Be sure to let your doctor know about any abdominal surgery you've had.
* Write down key personal information, including any recent changes or stressors in your life. These factors can be connected to digestive signs and symptoms.
* Take a family member or friend along, if possible. Sometimes it can be difficult to absorb all the information provided during an appointment. Someone who accompanies you may remember something that you missed or forgot.
* Write down questions to ask your doctor. Creating your list of questions in advance can help you make the most of your time with your doctor.
For blind loop syndrome, some basic questions to ask your doctor include:
* What is the most likely cause of my condition?
* Are there any other possible causes for my condition?
* What diagnostic tests do I need?
* What treatment approach do you recommend trying first?
* If the first treatment doesn't work, what will you recommend trying next?
* Are there any side effects associated with the medications you're prescribing?
* Will I need to stay on medications long term?
* How often will you see me to monitor my progress?
* Do I need to make any dietary changes?
* Should I take any nutritional supplements?
* Are there any lifestyle changes I can make to help reduce or manage my symptoms?
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions at any time that you don't understand something.
What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over points you want to spend more time on. You may be asked:
* Have you ever had abdominal surgery?
* What are your symptoms?
* When did you first notice these symptoms?
* Do your symptoms come and go, or stay about the same?
* Is your pain crampy?
* Does your pain radiate to other parts of your abdomen or to your back?
* Have you lost weight without trying?
* Have you noticed a change in your stools?
* Have your signs and symptoms included vomiting?
* Have your signs and symptoms included a fever?
* Has anyone close to you had similar signs or symptoms recently?
* What is your typical daily diet?
* Have you ever been diagnosed with a food allergy or with lactose intolerance?
* Have you been diagnosed with any other medical conditions?
* What medications are you taking, including prescription and over-the-counter medications, vitamins, herbs and supplements?
* Do you have any family history of bowel disorders or colon cancer?
Tests and diagnosis
The first step in diagnosing blind loop syndrome is usually an imaging test, such as:
* Abdominal X-ray. Your doctor may take X-ray pictures of your digestive system to look for possible causes of your signs and symptoms.
* Abdominal computerized tomography (CT) scan. This X-ray technique produces more-detailed images of the body than conventional X-rays do.
You may also have additional tests to check for bacterial overgrowth in your small intestine, for poor fat absorption, or for other problems that may be causing or contributing to your symptoms:
* Barium X-ray of the small intestine. This test uses a contrast solution (barium) to coat the lining of your intestine so that it stands out clearly on X-rays. A barium X-ray may reveal a blind loop, diverticulosis, a narrowing (stricture) of the intestine or other anatomical problems as well as slow transit times that can cause bacterial overgrowth.
* Hydrogen breath test. Several breath tests are used to check for bacterial overgrowth. Because fermenting carbohydrates release hydrogen, this test measures the amount of hydrogen that you breathe out after you drink a mixture of glucose and water. A rapid rise in hydrogen indicates poor carbohydrate digestion and bacterial overgrowth in your small intestine. Although widely available, this test is less sensitive than other breath tests.
* D-xylose breath test. In this test, which is more accurate than a hydrogen breath test, you ingest a type of sugar called xylose into which a radioactive label (radiolabel) has been incorporated. If unusual numbers of bacteria are present in your small intestine, they metabolize the xylose, releasing radiolabeled carbon dioxide in the process. This carbon dioxide is measured. High levels suggest bacterial overgrowth.
* Bile acid breath test. In your small intestine, bile acids from your liver help emulsify and digest fats (lipids). But proliferating bacteria interfere with this process, leading to poor absorption of both fats and carbohydrates. This test uses a bile salt (glycocholate) bound to a small amount of radioactive material to check for bile salt dysfunction in your small intestine.
* Quantitative fecal fat test. This test may be used to determine how well fats are absorbed. Most often, you eat a high-fat diet for three days. The amount of fat in your stool is then measured. Large amounts of undigested fat indicate malabsorption (steatorrhea), one cause of which is bacterial overgrowth.
* Small intestine aspirate and fluid culture. This is the most sensitive test for bacterial overgrowth. To obtain the fluid sample, doctors pass a long flexible tube (endoscope) down your throat and through your upper digestive tract to your small intestine. A sample of intestinal fluid is withdrawn with the endoscope and then placed in a culture medium in a laboratory where it's observed for the growth of bacteria.
In some cases, when the likelihood of bacterial overgrowth is high, your doctor may begin treatment with antibiotics immediately without specific testing (empiric therapy).
Treatments and drugs
Whenever possible, doctors treat blind loop syndrome by dealing with the underlying problem — surgically repairing a postoperative blind loop, stricture or fistula, 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. Some people with a blind loop may go for long periods without needing antibiotics, while other may need regular antibiotic therapy.
Doctors may also 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.
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 may 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 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, and are more readily digested by some people with blind loop syndrome. Medium-chain triglycerides are sometimes prescribed as a dietary supplement for people with severe blind loop syndrome.