Blind Loop Syndrome

Synonyms: Stasis syndrome, Stagnant loop syndrome

In blind loop syndrome a portion of the small intestine becomes bypassed and thus cut off from the normal flow of food. The digestion of food becomes slow or stops leading to the growth of bacteria and malabsorption.

Pathophysiology

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.

Medical problems resulting from blind loop syndrome

• Fat malabsorption e.g. steatorrhoea, blindness (from vitamin A deficiency), osteoporosis (from vitamin D deficiency)¹
• Inflammation of the small intestine wall leads to malabsorption of protein and carbohydrates
• Vitamin B12 deficiency resulting in a macrocytic anaemia
• Iron deficiency
• Osteoporosis from calcium and vitamin D deficiency

Causes

• Surgery e.g. Billroth II, Roux-en-Y procedure, gastric bypass for obesity²
• Inflammatory bowel disease e.g. Crohn's disease
• Scleroderma
• Intestinal duplication
• Diverticulosis of the small intestine
• Diabetes mellitus
• Radiation enteritis

Presentation

• Loss of appetite and early satiety
• Diarrhoea and steatorrhoea
• Weight loss
• Nausea
• Abdominal examination may reveal cachexia, abdominal distension and evidence of vitamin and mineral deficiencies.

Investigations

• Bloods may reveal
  • Macrocytic anaemia (due to Vit B12 deficiency)
  • Hypocalcaemia
  • Iron deficiency
  • Raised INR (due to vitamin K deficiency)
• Abdominal imaging including
  • Abdominal x ray
  • Abdominal CT scan
  • Barium studies
• Hydrogen breath test to detect bacterial overgrowth
• Specialised investigations looking at small intestine function
  • Xylose breath test
  • Faecal fat test
  • Bile acid breath test
• Small intestine aspirate with fluid culture - invasive and difficult

Specialised investigations and small intestine aspirates are rarely performed.

Management

• The underlying cause should be corrected if possible e.g. 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. Commonest antibiotics used are the tetracyclines e.g. oxytetracycline but it is estimated that upto 70% will fail to respond to this. There have been some promising results with rifamixin which is a non-absorbable antibiotic but this is not more superior to metronidazole - which should be used as an alternative if there is lack of success with the tetracyclines.³Development of resistance is a problem and antibiotics may need to be changed frequently.Probiotics help in animal studies but their role in humans with bacterial overgrowth is yet to be established.⁴
  • Nutritional supplements - This can involve any of the following
    • Vit B12 injections
    • Oral vitamin supplements
    • Oral iron supplements
    • Oral calcium and vit D supplements
    • Medium chain triglycerides (are more readily digested)⁵

Complications

Untreated the following can occur

• Intestinal infarction
• Complete intestinal obstruction
• Perforation

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Document References

1. Kumar, P; Clarke, M. Clinical Medicine, 6th Ed, (2005), WB Saunders: London.
   
2. Bacterial overgrowth syndrome; E-medicine; Oct 2006.
   
3. 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. [abstract]
   
4. Quigley EM, Quera R; Small intestinal bacterial overgrowth: roles of antibiotics, prebiotics, and probiotics. Gastroenterology. 2006 Feb;130(2 Suppl 1):S78-90. [abstract]
   
5. Blind loop syndrome; CNN.com health/library; Jan 2006.