Blind loop syndrome (BLS), also known as stagnant loop syndrome, is a state that occurs when the normal bacterial flora of the

small intestine The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the p ...

proliferates to numbers that cause significant derangement to the normal physiological processes of digestion and absorption. In some cases of blind loop syndrome, overgrowth of

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

ic non-

commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fro ...

bacteria has also been noted. It has long been understood that from birth, and throughout life, large amounts of bacteria reside symbiotically within animal gastrointestinal tracts such as the

human gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans ...

. The understanding of this

gut flora Gut microbiota, gut microbiome, or gut flora, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gut mi ...

has even led to novel treatments for bowel irregularity that utilize so called "

probiotics Probiotics are live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut microbiota. Probiotics are considered generally safe to consume, but may cause bacteria-host i ...

" or good bacteria that aid in normal digestion. The problem of BLS arises when the bacterial colonies residing in the upper gastrointestinal tract begin to grow out of control or are altered in their makeup thereby creating a burden on the normal physiological processes occurring in the small intestine. This results in problems, among others, of:

vitamin B12 deficiency Vitamin B12 deficiency, also known as cobalamin deficiency, is the medical condition in which the blood and tissue have a lower than normal level of vitamin B12. Symptoms can vary from none to severe. Mild deficiency may have few or absent symp ...

, fat malabsorption and

steatorrhea Steatorrhea (or steatorrhoea) is the presence of excess fat in feces. Stools may be bulky and difficult to flush, have a pale and oily appearance, and can be especially foul-smelling. An oily anal leakage or some level of fecal incontinence may oc ...

, fat-soluble vitamin deficiencies and intestinal wall injury.

Symptoms and signs

Most of the symptoms of BLS are non specific but nevertheless warrant the utmost attention. These include: * Loss of appetite *

Nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...

Flatulence Flatulence, in humans, is the expulsion of gas from the intestines via the anus, commonly referred to as farting. "Flatus" is the medical word for gas generated in the stomach or bowels. A proportion of intestinal gas may be swallowed environm ...

Diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...

* Fullness after a meal * Fatty stools (steatorrhea) * Unintentional weight loss * Generalised weakness As a result of the concomitant vitamin and mineral deficiencies that occur as a result of the malabsorption associated with BLS patients with advanced cases should be investigated for: *

Vitamin B12 deficiency Vitamin B12 deficiency, also known as cobalamin deficiency, is the medical condition in which the blood and tissue have a lower than normal level of vitamin B12. Symptoms can vary from none to severe. Mild deficiency may have few or absent symp ...

Folate deficiency Folate deficiency, also known as vitamin B9 deficiency, is a low level of folate and derivatives in the body. Signs of folate deficiency are often subtle. A low number of red blood cells (anemia) is a late finding in folate deficiency and folate ...

Iron deficiency Iron deficiency, or sideropenia, is the state in which a body lacks enough iron to supply its needs. Iron is present in all cells in the human body and has several vital functions, such as carrying oxygen to the tissues from the lungs as a key ...

Vitamin E deficiency Vitamin E deficiency in humans is a very rare condition, occurring as a consequence of abnormalities in dietary fat absorption or metabolism rather than from a diet low in vitamin E. Collectively the EARs, RDAs, AIs and ULs for vitamin E and other ...

Causes

Blind loop syndrome is a complication of surgical operations of the abdomen, as well as

inflammatory bowel disease Inflammatory bowel disease (IBD) is a group of inflammation, inflammatory conditions of the colon (anatomy), colon and small intestine, Crohn's disease and ulcerative colitis being the principal types. Crohn's disease affects the small intestine a ...

scleroderma Scleroderma is a group of autoimmune diseases that may result in changes to the skin, blood vessels, muscles, and internal organs. The disease can be either localized to the skin or involve other organs, as well. Symptoms may include areas of ...

. Another cause is jejunoileal diverticula.Sabiston textbook of surgery board review, 7th edition. Chapter 42 small intestine, question 14

Pathophysiology

The overgrowth of bacteria in the small intestine is prevented by various mechanical and chemical factors which include the constant peristaltic movement of contents along the length of the gastrointestinal tract and the antibacterial properties of gastric secretions, pancreatic secretions and

bile Bile (from Latin ''bilis''), or gall, is a dark-green-to-yellowish-brown fluid produced by the liver of most vertebrates that aids the digestion of lipids in the small intestine. In humans, bile is produced continuously by the liver (liver bile ...

. It follows that a disruption of any of these factors could lead to bacterial overgrowth and indeed BLS has been found to occur in persons with anatomical anomalies that result in stagnation. BLS has also been associated with

achlorhydria Achlorhydria and hypochlorhydria refer to states where the production of hydrochloric acid in gastric secretions of the stomach and other digestive organs is absent or low, respectively. It is associated with various other medical problems. Sig ...

, dysmotility,

fistulae A fistula (plural: fistulas or fistulae ; from Latin ''fistula'', "tube, pipe") in anatomy is an abnormal connection between two hollow spaces (technically, two epithelialized surfaces), such as blood vessels, intestines, or other hollow or ...

, and

strictures A stenosis (from Ancient Greek στενός, "narrow") is an abnormal narrowing in a blood vessel or other tubular organ or structure such as foramina and canals. It is also sometimes called a stricture (as in urethral stricture). ''Stricture' ...

. Chronic or high dose

opioid Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid us ...

therapy may contribute to BLS by reducing gastric motility. Due to the disruption of digestive processes by the overgrowth of intestinal bacteria; malabsorption of bile salts, fat and fat-soluble vitamins, protein and carbohydrates results in damage to the mucosal lining of the intestine by bacteria or via the production of toxic metabolites.

Diagnosis

A physical examination may reveal a mass or distention of the abdomen.Tests which may be useful for diagnosis include: * Abdominal x-ray * Abdominal CT scan * Contrast enema study

Treatment

The treatment of BLS follows two basic principles. When a patient presents with symptoms of BLS, the treating physician basically has two recognized options for management: * Test-and-treat * Treat empirically

Test-and-treat method

Although it would seem to be the better way to go in terms of management, there has been recent criticism on the need for such testing because of reliability issues. However, it must be stated that there are options such as the glucose breath test and jejunal aspiration the explanations of which are beyond the scope of this current article.

Treating empirically

The "treat empirically" route also has its difficulties, which have all come under wide debate and study. Recommendations are varied but seem to find some common ground around the notion that treatment should be individualized to the specific circumstances under which a patient has developed BLS since these circumstances affect the complex microbial make up of the affected bowel.

Tetracyclines Tetracyclines are a group of broad-spectrum antibiotic compounds that have a common basic structure and are either isolated directly from several species of ''Streptomyces'' bacteria or produced semi-synthetically from those isolated compounds. T ...

have been the mainstay of treatment for BLS, but recent studies have concluded

Rifaximin Rifaximin, is a non-absorbable, broad spectrum antibiotic mainly used to treat travelers' diarrhea. It is based on the rifamycin antibiotics family. Since its approval in Italy in 1987, it has been licensed in over more than 30 countries for th ...

to be very effective in the treatment of BLS. One study by Di Stefano et al., however, concluded

Metronidazole Metronidazole, sold under the brand name Flagyl among others, is an antibiotic and antiprotozoal medication. It is used either alone or with other antibiotics to treat pelvic inflammatory disease, endocarditis, and bacterial vaginosis. It is ef ...

to be more effective than

in the treatment of BLS.

Surgical management

Surgical management is reserved for fixing anatomical causes of bowel obstruction that interfere with normal function once they are amenable to such intervention. These conditions include: * Strictures * Fistulae * Diverticula

References

External links

{{Gastroenterology Gastrointestinal tract disorders Syndromes