II. Causes
-
Roux-en-Y gastric bypass
- Intraabdominal Hernia near Gastric Bypass site with secondary ischemia and infarction of bowel
III. Epidemiology
- Occurs in up to 3% of retrocolic bypass procedures
IV. Pathophysiology
- Small Bowel trapped in Internal Hernia results in closed loop obstruction
V. Risk Factors
- Greatest post-surgical weight loss (exaggerates defects)
- Laparoscopic surgery (less adhesions)
VI. Types
- Peterson Defect (approximately 66% of cases)
- Occurs in the space between the mesentery and the overlying roux limb as it approaches the pouch
-
Small Bowel anastomosis defect (approximately 33% of cases)
- Occurs in the space between the mesentary and the overlying Jejunostomy
- Higher risk of Small Bowel ischemia or infarction
VII. Signs: Presentation
- Most common in first 6-18 months post-operatively
- Presents with colicky Epigastric Pain that worsens with eating
VIII. Evaluation
- Requires urgent surgical Consultation
IX. Imaging: Abdominal CT with oral and IV contrast
- Positive findings are subtle
- Swirling mesenteric vessels (whirl sign)
- Pathognomonic for Internal Hernia
- Represent bowel loops around the Internal Hernia site
- Mesenteric vessels may also be stretched or displaced
- Small Bowel appearance
- Clustering of dilated small intestinal loops
- Small Bowel loop posterior to superior Mesenteric Artery
- Mushroom shaped Hernia
- Other findings
- Mesenteric edema
- Mesenteric Lymphadenopathy
- Swirling mesenteric vessels (whirl sign)
- CT is only helpful if positive (often normal initially)
- Emergent surgery is indicated for a positive CT
- Negative result should not be considered reassuring
- Does not replace urgent Consultation with bariatric surgeon if Internal Hernia is suspected
X. Complications
- Critical Illness or death
- Short bowel syndrome (resection of necrotic Small Bowel)
XI. References
- Weinstock in Herbert (2012) EM:RAP 12(3): 3
- Lockhart (2007) AJR Am J Roentgenol 188(3):745-50 +PMID: 17312063 [PubMed]