Obturator hernia
Obturator hernias (alternative plural: herniae) are characterized by bowel herniating between the obturator and the pectineus muscles. They are a rare type of abdominal hernia and can be a challenge to diagnose clinically.
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Epidemiology
Typically obturator hernias occur in older women 2,3 or patients with chronically raised intra-abdominal pressure (e.g. ascites, COPD, chronic cough) 3. They can occur in pregnancy, due to relaxation of the pelvic peritoneum and a wider and more horizontal obturator canal 3. It has been suggested that there is a female predominance with this type of hernia, and they occur in less than 0.04% of all hernias 6.
Clinical presentation
In general, obturator hernias are asymptomatic unless they 1:
- compress the obturator nerve: Howship-Romberg sign (only present in approximately half of cases) 3
- contain bowel which incarcerates/obstructs/strangulates
Pathology
The obturator foramen is occluded by the obturator membrane, which is pierced anterosuperiorly by the obturator artery, vein and nerve. This neurovascular bundle then travels along a 2-3 cm oblique tunnel, the obturator canal. It is through this deficiency that an obturator hernia occurs. Presumably, due to the sigmoid colon on the left, these hernias are more common on the right 3.
The layers that the hernial neck passes through include:
- obturator internus muscle fibers
- obturator membrane
- obturator externus muscle fibers
The hernia will then lie superficial to obturator externus and deep and inferior to pectineus muscle.
The hernia may contain any of the following:
- no more than peritoneum filled with fluid, as seen in patients with ascites
- small bowel (most common)
- colon 3
- appendix
- omentum
- Meckel diverticulum
- ovary/fallopian tube
- and even uterus 3
Radiographic features
The diagnosis is readily made on CT/MRI with either fluid or bowel able to be traced along the aforementioned course to lie in the medial upper thigh.
Signs of complication, including:
- bowel obstruction
- strangulation resulting in perforation
Treatment and prognosis
Treatment involves surgery and repair of the hernial orifice.
History and etymology
Howship-Romberg sign is named for the German neurologist, Moritz Heinrich Romberg (1795-1873) 5, and British surgeon John Howship (1781-1841) 4.
Differential diagnosis
If a hernia contains bowel or can be clearly traced through the obturator foramen, then there are very few alternative diagnoses.
If seen with ultrasound, it may be mistaken for a bursa or acetabular labral cyst.
Related Radiopaedia articles
Hernias
-
hernias
-
anterior abdominal wall herniation
- epigastric hernia
- incisional hernia
- port site hernia
- interparietal hernia
- parastomal hernia
- paraumbilical hernia
- Spigelian hernia
- umbilical hernia
- miscellaneous
- Maydl hernia
- Richter hernia: contains only one wall of a bowel loop
-
lumbar hernias
- superior lumbar hernia
- inferior lumbar hernia
-
groin herniation
-
inguinal hernia
- direct inguinal hernia
- indirect inguinal hernia: five times commoner than direct
- pantaloon hernia (combined direct and indirect inguinal herniae)
- femoral hernia
- obturator hernia
-
inguinal hernia
- diaphragmatic herniation
-
internal herniation: an uncommon cause of bowel obstruction
- paraduodenal hernia: left and right
- lesser sac (foramen of Winslow) hernia
- pericaecal hernia
-
sigmoid mesocolon hernias
- intersigmoid hernia
- transmesosigmoid hernia
- intramesosigmoid hernia
-
small bowel mesentery internal hernia
- transmesenteric hernia
- intramesenteric hernia
- transomental hernia
- supravesical hernia
- pelvic internal hernia
- falciform ligament hernia
- internal hernia due to gastric bypass surgery
- Littre hernia: hernia containing a Meckel diverticulum
- pelvic hernia
-
anterior abdominal wall herniation