Paraduodenal hernia usually presents as a small bowel obstruction in adults, caused by herniation of small intestine into a congenital peritoneal sac, most commonly near the ligament of Treitz.
Description
Paraduodenal hernia is the most common type of internal hernia, where a part of the small intestine herniates into a congenital mesenteric defect adjacent to the duodenum. It is classified into two types: left paraduodenal hernia, occurring near the ligament of Treitz, and right paraduodenal hernia, occurring near the ileocecal junction. Internal hernias have a high rate of volvulus.
Pathogenesis
The pathogenesis is related to the improper rotation and fusion of the mesentery during embryonic development, leading to the formation of mesenteric defects. These defects create potential spaces for the herniation of small bowel loops.
Subtypes
- Left Paraduodenal Hernia: More common (75%, arising near the ligament of Treitz. Caused by congenital failure of fusion of the descending colon mesentery to the parietal peritoneum in the left upper quadrant. Small bowel herniates posteroinferiorly through a retroperitoneal mesenteric defect named the fossa of Landzert, located to the behind and left of the 4th segment of duodenum, posterior to the inferior mesenteric vein, into the left portion of the transverse mesocolon and descending mesocolon. A cluster of small bowel is seen between the pancreas and stomach.
- Right Paraduodenal Hernia: Less common (25%), located near the ileocecal junction. Caused by congenital failure of fusion of the ascending colon mesentery to the parietal peritoneum in the right lower quadrant. Bowel and mesentery containing iliocolic, right colic and middle colic arteries herniate through a defect named the fossa of Waldeyer, located posterior to the superior mesenteric artery and vein.1
Epidemiology, Risk Factors & Associations
- Occurs in about 0.2-0.9% of the population.
- Equal prevalence in men and women.
- Often asymptomatic and found incidentally during imaging or surgery.
Clinical Features
- Intermittent, chronic, post-prandial abdominal pain.
- Pain relieved by massaging upper abdomen.
- Symptoms of small bowel obstruction such as nausea, vomiting, and abdominal distension.
Complications
- Small bowel obstruction.
- Strangulation of herniated bowel with risk of ischaemia.
- Risk of misdiagnosis leading to delayed treatment.
Pathological Features
Histopathology
- Macroscopic: Herniation of small bowel into a mesenteric sac.
- Microscopic: Normal bowel histology unless strangulation has occurred.
Serology
- Not specific for paraduodenal hernia.
Biochemistry
- Not relevant for diagnosis.
Radiological Features
General Features
- Encapsulated mass-like cluster of small bowel loops
- Left Paraduodenal
- Located in the left anterior pararenal space, between the pancreas and the stomach.
- The IMV and ascending branch of the left colic artery are within the anterior neck of the hernial orifice.
- Associated anterior mass effect on posterior stomach wall, duodenojejunal junction inferomedially and transverse colon inferiorly.
- Right Paraduodenal
- Located in the right upper quadrant or near the liver, inferior to the third portion of the duodenum.
- The iloioc colic, right colic and middle colic arteries, SMV, SMA and right colic vein may all be involved with the anterior neck of the hernial orifice.2
- Evidence of small-bowel obstruction with dilated loops and air-fluid levels
XR
- May show signs of small bowel obstruction or a mass effect.
CT
- Most effective for diagnosis.
- Shows clustered small bowel loops in a sac-like mass, sometimes with the ‘whirl sign’ indicating twisted mesentery.
- Can identify complications like obstruction or ischaemia.
- Assess vascular landmarks around the neck of the internal hernia:
- Left paraduodenal hernia: Cluster of small bowel loops in the left anterior pararenal space. The inferior mesenteric vein (IMV) and ascending branch of the left colic artery are within the anterior neck of the hernial orifice.
- Right paraduodenal hernia: Cluster of small bowel loops inferior to the third portion of the duodenum. The superior mesenteric vein (SMV), the superior mesenteric artery (SMA), and the right colic vein are within the anterior neck of the hernial orifice
MRI
- Not routinely used but can provide detailed anatomical information.
US
- Can sometimes identify herniated bowel loops, especially in paediatric patients.
Barium Studies
- May demonstrate displacement of bowel loops or a transition point in cases of obstruction.
Grading and Staging
No specific grading or staging system for paraduodenal hernia.
Diagnosis
Diagnosis is often made by CT imaging, particularly in patients presenting with symptoms of bowel obstruction. Clinical history and physical examination are important, but imaging is crucial for an accurate diagnosis.
Differential Diagnosis
- Other causes of small bowel obstruction, such as adhesions or hernias.
- Crohn’s Disease: Chronic abdominal pain, diarrhea, systemic symptoms.
- Peptic Ulcer Disease: Epigastric pain, especially related to meals.
Management
Surgical intervention is the definitive treatment for symptomatic paraduodenal hernias. This can involve reduction of the herniated bowel and closure of the mesenteric defect. In asymptomatic cases, particularly incidentally discovered hernias, a conservative approach may be taken, but close monitoring is essential to avoid complications.
References
- Sun, E.X., Shi, J. and Mandell, J.C. eds., 2021. Core Radiology: A Visual Approach to Diagnostic Imaging. Cambridge University Press. ↩︎
- Martin, L.C., Merkle, E.M. and Thompson, W.M., 2006. Review of internal hernias: radiographic and clinical findings. American Journal of Roentgenology, 186(3), pp.703-717. ↩︎