What is short bowel syndrome?

Short Bowel Syndrome: Definition, Consequences, and Management

Short bowel syndrome (SBS) is a devastating clinical pathological syndrome resulting from the loss of intestinal length due to disease or surgical resection, generally defined as having a residual small intestinal length of 200 cm or less, which leads to malabsorption, malnutrition, dehydration, and electrolyte abnormalities. 1

Definition and Classification

SBS occurs when a patient has insufficient functional small intestine remaining after surgery or congenitally. The severity depends on:

• Residual bowel length: Generally defined as ≤200 cm of remaining small intestine 1, though some reports suggest ≤150 cm may be more appropriate
• Anatomical configuration: Based on presence or absence of colon, patients can be classified into three groups 1:
  1. End-jejunostomy (most severe)
  2. Jejunum anastomosed to partial colon
  3. Jejuno-ileo-colic anastomosis with intact ileocecal valve (most favorable)

The European Society for Clinical Nutrition and Metabolism further classifies intestinal failure severity based on nutritional support requirements 2:

• Severe: Requires parenteral nutrition
• Moderate: Requires enteral nutrition
• Mild: Requires oral supplements

Pathophysiology and Clinical Manifestations

The clinical consequences of SBS directly relate to the extent and location of intestinal loss:

• General consequences: Diarrhea, dehydration, electrolyte abnormalities, and weight loss 1
• Specific consequences: Depend on regions missing (e.g., vitamin B12 deficiency with terminal ileum resection) 1

Patients at greatest nutritional risk typically have:

• Duodenostomy or jejunoileal anastomosis with ≤35 cm of residual small intestine
• Jejunocolic or ileocolic anastomosis with ≤60 cm of residual small intestine
• End jejunostomy with ≤115 cm of residual small intestine 1

Clinical Presentation by Anatomical Type

1. Jejunostomy patients:

   • Immediate problems with dehydration after surgery
   • Large stomal water and sodium losses, especially after eating/drinking 1
   • Often require parenteral support

2. Jejunum-colon patients:

   • May initially appear well except for diarrhea/steatorrhea
   • Can develop severe undernutrition months after resection 1
   • May benefit from oral rehydration solutions

Management Principles

The primary goals of SBS management are:

1. Nutritional support: Providing adequate macro- and micronutrients to prevent malnutrition
2. Fluid and electrolyte balance: Preventing dehydration and correcting electrolyte abnormalities
3. Acid-base balance: Correcting and preventing disturbances 1

Medical Management

• Oral rehydration solutions (ORS): Glucose-polymer-based with 90-120 mEq/L sodium should be used in patients with jejunostomy to decrease dehydration and parenteral fluid requirements 1
• Medications:
  • Antisecretory drugs (H2 antagonists, proton pump inhibitors) for very short bowel (<100 cm)
  • Antidiarrheal medications (loperamide) to slow intestinal transit 1
  • Somatostatin analogues in select cases

Nutritional Support

Based on the severity of intestinal failure:

• Mild cases: Oral supplements and dietary adjustments
• Moderate cases: Enteral nutrition
• Severe cases: Parenteral nutrition 1

The American Gastroenterological Association recommends:

• Patients with <50 cm of small intestine may require long-term parenteral nutrition
• Patients with <100 cm of jejunum may require parenteral saline solution
• Patients with <75 cm may require both long-term parenteral nutrition and saline solution 2

Complications and Monitoring

Common complications include:

• Catheter-related sepsis
• Metabolic complications (hyperglycemia)
• Liver function abnormalities
• Venous thrombosis 2
• Magnesium deficiency (may occur despite normal serum levels) 1
• Small intestinal bacterial overgrowth, especially with ileocecal valve resection 1
• Metabolic bone disease 3

Referral for Transplantation

Patients with irreversible intestinal failure who are expected to die prematurely on parenteral nutrition should be referred for consideration of intestinal transplantation when appropriate 1.

Key Clinical Considerations

• Accurate measurement and reporting of residual bowel length is crucial for prognosis and management planning 1
• The colon becomes an important digestive organ in SBS patients 1
• Patients should avoid plain water consumption and use ORS when thirsty 1
• Regular monitoring for nutrient deficiencies is essential, including 24-hour urine magnesium 1
• Calcium supplementation (800-1200 mg daily) is recommended routinely 1

SBS management requires a specialized multidisciplinary approach with expertise in intestinal failure to optimize outcomes and quality of life.