Blind Loop Syndrome

Content below is from a textbook reference chapter (Sabiston Ch50 - Diverticular Disease & Miscellaneous Problems), not primary literature. Also referenced from Duodenal Diverticula and Jejunal and Ileal Diverticula as a stasis-driven complication of those conditions.

Definition and cause

A rare condition manifested by diarrhea, steatorrhea, megaloblastic anemia, weight loss, and deficiencies of the fat-soluble vitamins as well as neurologic disorders. The underlying cause is bacterial overgrowth in stagnant areas of the small bowel produced by stricture, stenosis, fistulas, or diverticula (e.g., jejunoileal or Meckel diverticulum). Under normal circumstances, the upper GI tract contains fewer than 10^5 bacteria/mL, mostly gram-positive aerobes and facultative anaerobes. However, with stasis, the number of bacteria increases, with excessive proliferation of aerobic and anaerobic bacteria — Bacteroides, anaerobic lactobacilli, coliforms, and enterococci are likely present in varying numbers. The bacteria compete for dietary vitamin B12, producing a systemic deficiency of vitamin B12 and megaloblastic anemia.

Diagnosis

Confirmed by a series of laboratory investigations. Bacterial overgrowth can be diagnosed with cultures obtained through an intestinal tube, or by indirect tests such as the 14C-xylose or 14C-cholylglycine breath tests. Excessive bacterial use of 14C substrate leads to an increase in 14C-labeled CO2. After bacterial overgrowth and steatorrhea are confirmed, the Schilling test (57Co-labeled vitamin B12 absorption) may be performed — should reveal a pattern of urinary excretion of vitamin B12 resembling that of pernicious anemia (urinary loss of 0–6% of vitamin B12 compared with the normal 7–25%). In patients with blind loop syndrome, vitamin B12 excretion is not altered by the addition of intrinsic factor, but a course of a broad-spectrum antibiotic (e.g., tetracycline) should return vitamin B12 absorption to normal.

Treatment

Parenteral vitamin B12 therapy and broad-spectrum antibiotics. Tetracyclines have been the mainstay of treatment, but studies have shown that rifaximin and metronidazole demonstrate less resistance and are also effective. For most patients, a single course of therapy (7–10 days) is sufficient, and the patient may remain symptom-free for months. Prokinetic agents have been used without real success. Surgical correction of the condition causing stagnation and blind loop syndrome produces a permanent cure and is indicated for patients who require multiple rounds of antibiotics or are receiving continuous therapy.

Open items / gaps

• No primary literature yet in the wiki on blind loop syndrome — entirely textbook-reference-derived.