Internal hernia

Background

  • An internal hernia is the protrusion of bowel through a peritoneal or mesenteric defect within the abdominal cavity, without involvement of the abdominal wall[1]
  • Historically, paraduodenal hernia was the most common type; however, with the rise of bariatric surgery, post-Roux-en-Y gastric bypass (RYGB) internal hernia has become the most commonly encountered form[2]
  • Reported incidence after RYGB: 2–9%, with higher rates after laparoscopic approaches (fewer adhesions → greater bowel mobility through mesenteric defects)[3]
  • This is a surgical emergency — delayed diagnosis leads to bowel ischemia, necrosis, perforation, and potentially short bowel syndrome or death[1]

Classification

Post-bariatric (most common in current practice)

  • Three potential hernia spaces are created during RYGB:[1]
    • Petersen space: Between the Roux (alimentary) limb mesentery and the transverse mesocolon — most common in antecolic approaches
    • Jejunojejunostomy (JJ) mesenteric defect: At the enteroenterostomy between the biliopancreatic and alimentary limbs
    • Transverse mesocolon defect: Only present in retrocolic Roux limb construction; most common in retrocolic approaches
  • Significant weight loss increases risk by creating laxity in the mesentery[1]
  • Average time from RYGB to internal hernia presentation: ~2–3 years, but can occur at any time[1]

Congenital (non-surgical)

  • Paraduodenal (most common congenital type; ~53% of all congenital internal hernias)
    • Left paraduodenal (fossa of Landzert) — more common
    • Right paraduodenal (fossa of Waldeyer)
  • Transmesenteric
  • Pericecal
  • Foramen of Winslow
  • Supravesical / pelvic
  • Transomental

Clinical features

  • Presentation ranges from intermittent, vague abdominal pain to acute surgical abdomen — highly variable and often leads to delayed diagnosis[1]
  • Symptoms may be episodic and self-resolving (spontaneous reduction of hernia) for weeks to months before an acute presentation

Classic presentation

  • Postprandial, crampy, periumbilical or left upper quadrant abdominal pain
  • Nausea, vomiting
  • Abdominal distension
  • Obstipation (if complete obstruction)
  • Pain may be worsened by eating and improved by position change or lying prone

Signs of complicated internal hernia (strangulation/ischemia)

  • Severe, constant abdominal pain out of proportion to exam (early ischemia)
  • Peritoneal signs (rebound, guarding, rigidity)
  • Hemodynamic instability (tachycardia, hypotension)
  • Fever, leukocytosis
  • Lactic acidosis

Biliopancreatic limb obstruction (specific to RYGB)

  • May present without classic nausea/vomiting or obstipation because the obstruction is in the excluded limb[3]
  • Instead: left upper quadrant fullness, hiccoughs, unexplained tachycardia
  • Left shoulder pain (from gastric remnant distension irritating the diaphragm)
  • This is particularly dangerous because the closed-loop obstruction of the biliopancreatic limb can progress to remnant gastric perforation (a catastrophic event that is difficult to diagnose)

Key ED pearl

  • A post-bariatric surgery patient with intermittent or acute abdominal pain should be presumed to have an internal hernia until proven otherwise
  • Multiple ED visits for abdominal pain in a post-RYGB patient without a clear diagnosis is a common pattern preceding internal hernia catastrophe[1]

Differential diagnosis

Evaluation

Workup

  • Determine the type of bariatric surgery performed — this is essential for interpretation of imaging and identification of potential hernia spaces[1]
  • Labs:
    • CBC (leukocytosis suggests ischemia/perforation)
    • BMP/CMP (electrolytes, renal function, bicarbonate)
    • Lactate — elevated lactate suggests bowel ischemia; however, a normal lactate does NOT exclude ischemia or strangulation[3]
    • Lipase (exclude pancreatitis)
    • LFTs
    • Coagulation studies
    • Type and screen (anticipate possible surgical intervention)
  • CT abdomen/pelvis with IV contrast — imaging modality of choice[4]
    • Oral contrast is not required and may delay imaging
    • Obtain with multiplanar reconstructions (coronal and sagittal views are critical)

Diagnosis

  • CT findings suggestive of internal hernia:[4]
    • Mesenteric swirl sign (whirlpool sign) — twisting/swirling of the mesenteric vessels and fat; most specific finding
    • Small bowel behind the mesenteric vessels (mushroom sign)
    • Clustered small bowel loops in the left upper quadrant or in an atypical location
    • Jejunojejunostomy (JJ) anastomosis displaced to the right of midline or above the transverse colon
    • Small bowel obstruction with transition point at a mesenteric defect
    • Engorgement or stretching of mesenteric vessels
    • Hurricane eye sign — rounded configuration of distal mesenteric fat and vessels
  • CT sensitivity is imperfect: Reported sensitivity ranges from 63–80%; specificity ~76%[4]
    • Retrospective review shows diagnostic abnormalities present in up to 97% of cases, but these are frequently missed prospectively by general radiologists
    • If clinical suspicion is high and CT is equivocal or negative, surgical exploration is still indicated[1]
  • Communicate directly with the radiologist — alert them to the bariatric surgical history and ask them to specifically evaluate for internal hernia; this significantly improves diagnostic accuracy[1]
  • Upright abdominal XR: May show dilated loops or air-fluid levels but is insufficient to diagnose or exclude internal hernia; CT is mandatory
  • Congenital internal hernias are typically diagnosed on CT in the setting of small bowel obstruction without prior surgical history

Management

ED management

  • NPO
  • IV fluid resuscitation — crystalloid bolus; correct dehydration and electrolyte abnormalities
  • IV antiemetics (ondansetron)
  • IV analgesia — do not withhold pain control; opioids as needed
  • Nasogastric tube: Consider for decompression if significant vomiting or distension
  • Broad-spectrum antibiotics: Initiate if concern for ischemia, perforation, or sepsis (e.g. piperacillin-tazobactam or cefepime + metronidazole)
  • Lactate monitoring: Serial measurements; rising lactate is ominous

Surgical management

  • Emergent surgical consultation for all suspected internal hernias — this is a time-sensitive surgical emergency[3]
  • Laparoscopic exploration is preferred when performed by an experienced bariatric surgeon; may require conversion to open in complicated cases[1]
  • Surgical goals:
    • Reduce herniated bowel
    • Assess bowel viability (resect necrotic segments)
    • Close mesenteric defects with non-absorbable suture to prevent recurrence
  • If bowel ischemia has progressed to necrosis → segmental resection; extensive resection may result in short bowel syndrome
  • Contact the patient's bariatric surgeon if possible — they know the specific anatomy and prior operative details
  • If a bariatric surgeon is not available at the presenting facility, consult general surgery and arrange transfer to a bariatric center if the patient can be stabilized[1]

Critical management pearl

  • Do NOT discharge a post-bariatric surgery patient with unexplained abdominal pain and a negative or equivocal CT without surgical consultation — internal hernias can spontaneously reduce and appear normal on imaging, only to recur and strangulate[1]

Disposition

  • Operative:
    • All patients with CT findings consistent with internal hernia
    • All patients with clinical concern for ischemia or strangulation regardless of CT findings
    • Biliopancreatic limb obstruction with gastric remnant distension
  • Admit with surgical consultation:
    • Equivocal CT findings in a symptomatic post-RYGB patient
    • Resolved symptoms but history concerning for intermittent internal hernia (may require elective/semi-urgent laparoscopic exploration)
  • Transfer:
    • If bariatric surgical expertise is not available at the presenting facility, stabilize and transfer to a facility with bariatric surgery capability
  • Discharge is rarely appropriate for post-RYGB patients with significant abdominal pain:
    • If pain fully resolves, CT is clearly negative, labs are normal, and the patient tolerates oral intake, discharge may be considered with very close follow-up (24–48 hours with bariatric surgeon)
    • Provide strict return precautions: worsening pain, vomiting, inability to eat, fever
    • Document the discussion of the risk of intermittent internal hernia and the possibility that imaging may be falsely negative

See also

External links

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 Pokala B, Giannopoulos S, Engwall-Gill A, Tien C, Gould JC, Kindel TL. Prevention and management of internal hernias after bariatric surgery: an expert review. Mini-invasive Surg. 2022;6:23.
  2. ↑ Takeyama N, Gokan T, Ohgiya Y, et al. CT of internal hernias. Radiographics. 2005;25(4):997-1015. PMID 16009820.
  3. ↑ 3.0 3.1 3.2 3.3 Chousleb E, Chousleb A. Management of post-bariatric surgery emergencies. J Gastrointest Surg. 2017;21(11):1946-1953. PMID 28900825.
  4. ↑ 4.0 4.1 4.2 Iannuccilli JD, Grand D, Murphy BL, Evangelista P, Jabbour N, Jamidar PA. Sensitivity and specificity of eight CT signs in the preoperative diagnosis of internal mesenteric hernia following Roux-en-Y gastric bypass surgery. Clin Radiol. 2009;64(4):373-380. PMID 19264181.
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