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Blind loop syndrome

Medical Professionals

Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find one of our health articles more useful.

Synonyms: stasis syndrome, stagnant loop syndrome, small intestinal bacterial overgrowth (SIBO) syndrome

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What is blind loop syndrome?1

In blind loop syndrome a portion of the small intestine becomes bypassed and thus cut off from the normal flow of food. This may lead to malabsorption and small intestinal bacterial overgrowth (SIBO) syndrome. It may also be associated with short bowel syndrome.


Obstruction to the normal passage of food through the affected segment leads to ineffective bile salt digestion of fats and fat-soluble vitamins. The stagnant food ferments, with associated bacterial overgrowth.2

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Small intestinal bacterial overgrowth3 4 5

  • SIBO should be suspected in the presence of irritable bowel syndrome (IBS)-like symptoms and/or malabsorption syndrome occurring in the presence of disorders predisposing to SIBO development.

  • Predisposing conditions include functional dyspepsia, achlorhydria (eg, gastric atrophy or chronic administration of proton pump inhibitors), chronic pancreatitis, cystic fibrosis, immunodeficiency, hypothyroidism, intestinal obstruction and/or stagnation (eg, adhesion, strictures, tumours), diverticular disease, coeliac disease and liver disease.

  • SIBO is often a recurrent disorder, depending on the nature of any predisposing condition.

  • The most common diagnostic tool is represented at present by a hydrogen breath test. However, the gold standard for diagnosis of SIBO is aspiration and direct culture of the jejunal aspirate.6 Urinary excretion tests may be useful.7

  • Management is with antibiotic treatment and management of any underlying cause. Many different antibiotics have been advocated but currently ofloxacin or metronidazole (first-line), or rifaximin are recommended.6

  • In addition to antibiotic treatment, prebiotics or probiotics have been studied:

    • Prebiotics alter gut bacteria indirectly by favouring growth of certain bacterial species.

    • Probiotics are postulated to enhance gut barrier function, decrease inflammatory response, stabilise gut flora and potentially modulate visceral hypersensitivity.

    • There is emerging evidence for the use of prebiotics and probiotics for treating SIBO.8 9

Medical problems resulting from blind loop syndrome1

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Causes of blind loop syndrome (aetiology)

Presentation of blind loop syndrome1

  • Loss of appetite, and early satiety.

  • Dyspepsia.

  • Diarrhoea and steatorrhoea.

  • Bloating, flatulence.

  • Weight loss.

  • Nausea.

Abdominal examination may reveal cachexia, abdominal distension and evidence of vitamin and mineral deficiencies.


SIBO can be diagnosed by:10

  • Culture of jejunum aspirate for bacterial counts.

  • 14C-D-xylose breath testing.

  • Non-invasive hydrogen breath testing using glucose or lactulose; or

  • 14C-glycocholic acid breath testing.

  • Urinary excretion tests using chemically synthesised bile acid conjugates.7

Bloods may reveal:

  • Macrocytic anaemia (due to vitamin B12 deficiency).

  • Hypocalcaemia.

  • Iron deficiency.

  • Raised INR (due to vitamin K deficiency).

Abdominal imaging including:

  • Abdominal X-ray.

  • Abdominal CT scan.

  • Barium studies.

Management of blind loop syndrome6

The treatment of SIBO syndrome usually includes the eradication of bacterial overgrowth with a repeated course of antimicrobials, correction of associated nutritional deficiencies and, when possible, correction of the underlying predisposing condition.10

  • The underlying cause should be corrected if possible - eg, surgical correction.

  • In many cases surgery is not an option and therapy has two aims:

    • Tackle bacterial overgrowth:

        • Antibiotics are used and may be required for long periods of time.

        • The most common antibiotic used are norfloxacin and meronidazole.

        • There are good results with rifaximin, which is a non-absorbable antibiotic; however, this is not superior to metronidazole.11

        • Development of resistance is a problem and antibiotics may need to be changed frequently. Rotating antibiotics for 10 consecutive days per month, for 3 months is more effective than a single course.12

        • Probiotics help in animal studies but their role in humans with bacterial overgrowth is yet to be established.13

    • Nutritional supplements - can involve any of the following:

      • May require nutritional support in hospital or primary care.

      • Vitamin B12 injections.

      • Oral iron supplements.

      • Oral calcium and vitamin D supplements; other vitamin supplements.

      • Medium-chain triglycerides (are more readily digested).

Complications of blind loop syndrome


This will depend on the cause, severity and associated complications.

Further reading and references

  1. Conforti AR, Luu S; Blind Loop Syndrome.
  2. Bures J, Cyrany J, Kohoutova D, et al; Small intestinal bacterial overgrowth syndrome. World J Gastroenterol. 2010 Jun 28;16(24):2978-90.
  3. Gabrielli M, D'Angelo G, Di Rienzo T, et al; Diagnosis of small intestinal bacterial overgrowth in the clinical practice. Eur Rev Med Pharmacol Sci. 2013;17 Suppl 2:30-5.
  4. Shah SC, Day LW, Somsouk M, et al; Meta-analysis: antibiotic therapy for small intestinal bacterial overgrowth. Aliment Pharmacol Ther. 2013 Oct;38(8):925-34. doi: 10.1111/apt.12479. Epub 2013 Sep 4.
  5. Grace E, Shaw C, Whelan K, et al; Review article: small intestinal bacterial overgrowth--prevalence, clinical features, current and developing diagnostic tests, and treatment. Aliment Pharmacol Ther. 2013 Oct;38(7):674-88. doi: 10.1111/apt.12456. Epub 2013 Aug 20.
  6. Rao SSC, Bhagatwala J; Small Intestinal Bacterial Overgrowth: Clinical Features and Therapeutic Management. Clin Transl Gastroenterol. 2019 Oct;10(10):e00078. doi: 10.14309/ctg.0000000000000078.
  7. Maeda Y, Murakami T; Diagnosis by Microbial Culture, Breath Tests and Urinary Excretion Tests, and Treatments of Small Intestinal Bacterial Overgrowth. Antibiotics (Basel). 2023 Jan 28;12(2):263. doi: 10.3390/antibiotics12020263.
  8. Hao Y, Xu Y, Ban Y, et al; Efficacy evaluation of probiotics combined with prebiotics in patients with clinical hypothyroidism complicated with small intestinal bacterial overgrowth during the second trimester of pregnancy. Front Cell Infect Microbiol. 2022 Oct 6;12:983027. doi: 10.3389/fcimb.2022.983027. eCollection 2022.
  9. Kiecka A, Szczepanik M; Proton pump inhibitor-induced gut dysbiosis and immunomodulation: current knowledge and potential restoration by probiotics. Pharmacol Rep. 2023 May 4:1-14. doi: 10.1007/s43440-023-00489-x.
  10. Rana SV, Bhardwaj SB; Small intestinal bacterial overgrowth. Scand J Gastroenterol. 2008;43(9):1030-7. doi: 10.1080/00365520801947074.
  11. Di Stefano M, Miceli E, Missanelli A, et al; Absorbable vs. non-absorbable antibiotics in the treatment of small intestine bacterial overgrowth in patients with blind-loop syndrome. Aliment Pharmacol Ther. 2005 Apr 15;21(8):985-92.
  12. Richard N, Desprez C, Wuestenberghs F, et al; The effectiveness of rotating versus single course antibiotics for small intestinal bacterial overgrowth. United European Gastroenterol J. 2021 Jul;9(6):645-654. doi: 10.1002/ueg2.12116. Epub 2021 Jul 9.
  13. Quigley EM, Quera R; Small intestinal bacterial overgrowth: roles of antibiotics, prebiotics, and probiotics. Gastroenterology. 2006 Feb;130(2 Suppl 1):S78-90.

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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