Paraduodenal Hernia

Paraduodenal hernia is a congenital internal hernia in which small bowel enters a retroperitoneal pouch beside the fourth part of the duodenum. It follows incomplete or abnormal midgut rotation, so a loop of bowel becomes trapped beneath the mesocolon, in a sac lined by peritoneum. It accounts for about half of all congenital internal hernias, but has an autopsy prevalence of under 1%. It affects men about three times as often as women, and most patients present between 30 and 60 years.

Two forms exist

• Left paraduodenal hernia (about 75%): the sac opens into the fossa of Landzert, behind the descending mesocolon. The inferior mesenteric vein and the left colic artery run in the anterior margin of the neck.
• Right paraduodenal hernia (about 25%): the sac opens into the fossa of Waldeyer, behind the superior mesenteric artery, and extends to the right of the duodenum. The superior mesenteric vessels run in the anterior margin of the neck.

The natural history is chronic intermittent obstruction or acute incarceration. Strangulation develops in up to half of acute presentations and mortality in this setting reaches 20 to 50%, so early diagnosis matters. Complications: closed-loop obstruction, bowel ischemia and perforation.

• Years of vague postprandial epigastric or periumbilical pain, with nausea, bloating and early satiety
• Acute presentation with colicky pain, vomiting and distension from small bowel obstruction
• A palpable epigastric or left upper quadrant mass in some patients
• Findings of peritonitis and fever when ischemia is present
• Red flags: constant severe pain, tachycardia, rising lactate, leukocytosis and peritonism

1. CT of the abdomen with intravenous contrast is the first-line test. Findings in the left form are a cluster of small bowel loops enclosed in a sac in the left upper abdomen between the stomach and pancreas, displacement of the stomach anteriorly, the transverse colon inferiorly and the inferior mesenteric vein to the front of the sac, with dilated, crowded and stretched mesenteric vessels entering the sac. In the right form the cluster lies to the right of the duodenum with the superior mesenteric artery at its front.
2. Small bowel follow-through shows a fixed cluster of loops with proximal dilatation and delay.
3. CT angiography maps the course of the inferior mesenteric vein or the superior mesenteric vessels before operation.
4. Laboratory tests: full blood count, lactate, urea, electrolytes and C-reactive protein.

Differentials: adhesive small bowel obstruction, other internal hernias, intussusception, volvulus, pancreatic pseudocyst, gastric outlet obstruction.

Acute presentation

• Nil by mouth, nasogastric decompression, IV crystalloid 20 mL/kg initially, and urinary catheter.
• Cefazolin 2 g IV and metronidazole 500 mg IV before incision, repeated every 8 hours for 24 hours (up to 5 days if bowel is resected).
• Enoxaparin 40 mg SC once daily from the evening before or after surgery.
• Emergency laparoscopy or laparotomy.

Operative technique

• Reduce the contents and check bowel viability. Resect non-viable bowel with primary anastomosis.
• Do not divide the anterior margin of the sac neck, as it contains the inferior mesenteric vein (left) or the superior mesenteric artery and ileocolic vessels (right).
• Obliterate the defect by closing the neck with interrupted non-absorbable sutures placed away from the vessels, or widen the neck through its avascular wall and fix the mesentery of the small bowel to the posterior peritoneum so it cannot re-enter.
• Do not simply reduce and leave the sac, because recurrence is common.

Elective repair: recommended for symptomatic patients and for asymptomatic patients with a confirmed hernia, because of the strangulation risk. A laparoscopic approach is feasible in expert hands.

Postoperative care: early oral intake as tolerated, paracetamol 1 g orally every 6 hours and enoxaparin 40 mg SC daily for 7 days after major surgery.

Children: cefazolin 30 mg/kg IV (maximum 2 g), with age-appropriate fluids and analgesia (paracetamol 15 mg/kg every 6 hours).

Complications: recurrence (rare after proper closure), injury to the mesenteric vessels, short bowel after extensive resection, adhesions and wound infection. Follow-up at 2 and 6 weeks. Counsel on obstructive symptoms that warrant urgent review.