The Stagnant Loop Syndrome, also known as the Bacterial Overgrowth Syndrome, occurs when increased bacterial colonization occurs in the small intestine, either as a result of underlying disease, drug therapy or surgery. It may present with fat, carbohydrate and vitamin malabsorption. The fat malabsorption is caused by breakdown of the bile acids required for fat absorption by the luminal bacteria. Carbohydrates are fermented by the bacteria before they can be absorbed.


Criteria for the diagnosis of stagnant loop syndrome (Shearman page 463):

(1) demonstration of causative lesion or disease

(2) a positive breath test or microbiologic analysis of a small bowel aspirate

(3) reversal of malabsorption by broad-spectrum oral antibiotic.


Normally the proximal small intestine should contain small number of bacteria. The presence of > 10^5 aerobic bacteria per mL of aspirate, or > 10^3 anaerobic bacteria per mL in an aspirate from upper jejunum is consistent with the stagnant loop syndrome.


The causative lesion can often be seen on a barium follow-through examination. A fistula to the colon (duodenocolic, enterocolic) may require a barium enema to be seen.


A glucose breath test results in a rapid rise in breath hydrogen from bacterial fermentation. A 14-C D-xylose test will show release of 14-CO2 in the breath within 30 minutes of administration.


Conditions associated with stagnant loop syndrome (Shearman, Table 16.3, page 461):

(1) chronic afferent loop obstruction

(2) intestinal strictures

(3) surgical blind loops

(4) multiple jejunal diverticula

(5) gastric operations

(6) enteroanastomosis

(7) gastrocolic, duodenocolic or enterocolic fistula

(8) extensive bowel resection

(9) pernicious anemia

(10) scleroderma

(11) diabetic neuropathy

(12) biguanide drugs

(13) treatment with H2-reeceptor antagonists or proton pump inhibitors

(14) chronic biliary infections

(15) hypogammaglobulinemia

(16) leukemia

(17) cirrhosis

(18) chronic malnutrition

(19) irradiation

(20) intestinal pseudo-obstruction


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