What is Short Bowel Syndrome?
Short bowel syndrome (SBS) is a malabsorptive disorder that occurs when a patient has insufficient functional small intestine—typically less than 200 cm from the ligament of Treitz—resulting in the inability to absorb adequate macronutrients, micronutrients, water, and electrolytes to maintain health without intravenous supplementation 1, 2.
Core Definition and Pathophysiology
SBS develops either surgically (after extensive bowel resection) or congenitally, leaving patients with inadequate intestinal absorptive capacity 2. The syndrome is characterized by:
- Malabsorption of nutrients and fluids
- Diarrhea and fatty stools
- Malnutrition and dehydration
- Electrolyte disturbances requiring correction 1
The severity and clinical presentation depend critically on several anatomical factors rather than simply the length of remaining bowel 2, 3:
Critical Anatomical Determinants
Patients can be divided into two distinct subgroups based on whether the colon remains in continuity—this distinction fundamentally changes management 2:
Patients at Greatest Nutritional Risk:
- Duodenostomy or jejunoileal anastomosis with ≤35 cm residual small intestine
- Jejunocolic or ileocolic anastomosis with ≤60 cm residual small intestine
- End jejunostomy with ≤115 cm residual small intestine 2
Role of the Colon:
In patients with SBS who retain their colon in continuity, the colon transforms into an important digestive organ, providing additional absorptive capacity that significantly improves prognosis 2, 4.
Relationship to Intestinal Failure
SBS is the primary pathophysiological mechanism leading to chronic intestinal failure (CIF), defined as gut function reduced below the minimum necessary for absorption, requiring intravenous supplementation to maintain health 1.
When the reduction in absorptive function does NOT require IV supplementation, this is termed "intestinal insufficiency or deficiency" (II/ID) rather than intestinal failure 1.
Common Causes
In Adults:
- Mesenteric vascular accidents (most common) 5
- Inflammatory bowel disease 6, 3
- Radiation enteritis 5
- Trauma 6
In Children:
- Congenital and perinatal diseases (most common) 5
Intestinal Adaptation
A critical concept in SBS is intestinal adaptation—the process occurring over 1-2 years whereby the remaining intestine attempts to compensate through structural and functional changes 5, 7. This adaptation determines whether patients will achieve oral autonomy or remain dependent on parenteral nutrition 7.
More than 50% of adults with SBS can be weaned completely from parenteral nutrition within 5 years of diagnosis, but if weaning is not accomplished within the first 2 years following the last bowel resection, the probability of eliminating PN use drops to less than 6% 4.
Classification Systems
SBS can be categorized by 1:
- Anatomical: Specific anatomy and length of residual bowel
- Evolutional: Early, rehabilitative, and maintenance phases
- Pathophysiological: With or without colon in continuity
- Clinical: With II/ID versus CIF
- Severity: Type and volume of required IV supplementation
Common Complications
Patients with SBS are prone to 2, 5:
- Bacterial overgrowth (especially when ileocecal valve is resected, allowing colonic bacteria to populate the small intestine)
- Specific nutrient deficiencies (vitamins A, B12, D, E; minerals including magnesium, calcium, zinc)
- Dehydration and electrolyte imbalances
- Acid-base disturbances 2