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Intraabdominal (Internal) Hernias [Sabiston]

Internal Hernias Caused by Developmental Defects

There are three general mechanisms whereby developmental abnormalities lead to internal hernias:

  1. Abnormal retroperitoneal fixation of the mesentery, causing anomalous positioning of the intestines (e.g., mesocolic or paraduodenal hernia).
  2. Abnormally large internal foramina or fossae (e.g., foramen of Winslow or supravesical hernia).
  3. Incomplete mesenteric surfaces with the presence of abnormal openings, through which the intestines herniate (e.g., mesenteric hernia).

The anatomic and radiographic features of acquired and congenital internal hernias have been reviewed in detail.

Mesocolic (Paraduodenal) Hernias

  • Mesocolic hernias are rare congenital hernias where the small intestine herniates behind the mesocolon, due to abnormal rotation of the midgut.
  • These hernias are categorized as:
    • Right Mesocolic Hernia: Results when the prearterial limb of the midgut loop fails to rotate around the superior mesenteric artery, causing the small intestine to remain on the right side.
    • Left Mesocolic Hernia: Occurs when the small intestine herniates between the inferior mesenteric vein and the posterior parietal attachments of the descending mesocolon. About 75% of mesocolic hernias are left-sided.

Radiographic and Clinical Features

  • Barium radiographs show displacement of the small intestine.
  • CT scans with intravenous contrast can show mesenteric vessel displacement and potential intestinal obstruction.

Treatment

  • Right Mesocolic Hernia:
    • Requires an incision of the lateral peritoneal reflections along the right colon.
    • The entire gut is repositioned as in nonrotation of the midgut.
    • The neck of the hernia is not opened to avoid injury to the superior mesenteric vessels.
  • Left Mesocolic Hernia:
    • Involves incision along the peritoneal attachments adjacent to the inferior mesenteric vein.
    • The herniated small intestine is reduced, and the vein is allowed to return to its normal position.
    • The neck of the hernia may be closed by suturing adjacent peritoneum to the retroperitoneum.

Mesenteric Hernias

  • These hernias occur when the intestine herniates through an abnormal orifice in the mesentery.
  • Most common location: Near the ileocolic junction; defects in the sigmoid mesocolon have also been reported.

Clinical Features and Treatment

  • Patients present with intestinal obstruction, either from compression at the hernia neck or torsion of the herniated segment.
  • Treatment: Reduction of the hernia and closure of the mesenteric defect.

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Here’s a breakdown of each figure:

  • (A) Right Mesocolic (Paraduodenal) Hernia:
    • The hernia orifice lies to the right of the midline.
    • The superior mesenteric artery and ileocolic artery are located at the anterior border of the hernia neck.
  • (B) Left Mesocolic (Paraduodenal) Hernia:
    • The hernia orifice is to the left of the midline.
    • The herniated intestine is behind the anterior wall of the descending mesocolon.
    • The inferior mesenteric vein is integral to the hernia sac.
  • (C) Surgical Management of Right Mesocolic Hernia:
    • Involves division of the lateral peritoneal attachments of the ascending colon.
    • This reflects the small and large intestine toward the left side of the abdomen, simulating nonrotation of the midgut.
    • The neck of the hernia is not opened to avoid injury to the superior mesenteric vessels.
  • (D) Surgical Management of Left Mesocolic Hernia:
    • The hernia sac is incised along an avascular plane immediately to the right of the inferior mesenteric vessels.
    • The small intestine is reduced from beneath the inferior mesenteric vein, and the neck of the hernia is closed by suturing the peritoneum to the retroperitoneum.