• Clinical science

Internal hernia

Abstract

An internal hernia is the protrusion of visceral contents through a congenital or acquired opening within the peritoneal cavity. Contained within the abdominal cavity, internal hernias have an incidence of < 1% and are significantly less common than external hernias. Patients with a history of Roux-en-Y gastric bypass or liver transplant are especially at risk of internal hernia formation. The clinical presentation of symptomatic internal hernias is often acute and nonspecific, presenting as a mechanical small bowel obstruction. CT scan is the imaging modality of choice in most cases, but surgical intervention is often required for definitive diagnosis and treatment. Incarceration or strangulation of internal hernias carries a high mortality rate and therefore rapid diagnosis and urgent surgical repair is imperative.

Epidemiology

  • Internal hernias have an overall incidence of < 1%
  • In patients who have undergone transmesenteric, transmesocolic, and retroanastomotic surgical procedures (notably Roux-en-Y gastric bypass or liver transplantation) internal hernias are a significantly more common cause of small bowel obstruction.
  • Sex: >

References:[1]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

Internal hernias are a protrusion of visceral contents through an opening within the peritoneal cavity :

  • Normal anatomic structure (e.g., Foramen of Winslow)
  • Congenital or acquired defect (e.g., postsurgical especially following Roux-en-Y gastric bypass or liver transplant)

References:[2]

Classification

Internal hernias may be classified as congenital vs. acquired, or by location as shown here:

Clinical features

Features of acute bowel obstruction :

  • Abdominal pain (chronic or colicky)
  • Nausea and vomiting; especially postprandial
  • Bloating

Severity of symptoms relate to the duration and reducibility of the hernia. If an internal hernia incarcerates and strangulates, the patient's clinical presentation will be similar to that of a strangulated external hernia!

References:[3][1]

Diagnostics

  • Abdominal x-ray: nonspecific signs of bowel obstruction (e.g., distended loops of bowel, absent air in distal colon, air fluid levels proximal to obstruction)
  • CT scan (best initial and gold standard imaging modality)
  • Laparoscopy or laparotomy (confirmatory and therapeutic)

The diagnosis of an internal hernia is confirmed by laparoscopy in the majority of cases!
References:[3]

Differential diagnoses

The differential diagnoses listed here are not exhaustive.

Treatment

  • Surgery (either open or laparoscopic)
    • Indications
      • Evidence of complicated bowel obstruction
      • Suspected internal hernia with persistent symptoms
    • Procedure: reduction of the hernia with closure of the hernial pathway
  • Internal hernias are difficult to rule out preoperatively and missed incarcerated internal hernias have a high mortality rate. Consequently, when an internal hernia is suspected, nonoperative intervention is rarely considered.

If an internal hernia leads to incarceration, the mortality rate is ∼80%!
References:[2]

  • 1. Martin LC, Merkle EM, Thompson WM. Review of internal hernias: radiographic and clinical findings. AJR Am J Roentgenol. 2006; 186(3): pp. 703–717. doi: 10.2214/AJR.05.0644.
  • 2. Yeo CJ, Matthews JB, McFadden DW, Pemberton JH, Peters JH . Shackelford's Surgery of the Alimentary Tract. Elsevier Saunders; 2012.
  • 3. Radswiki, et al. Internal hernia. https://radiopaedia.org/articles/internal-hernia. Updated February 14, 2017. Accessed February 14, 2017.
last updated 03/18/2018
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