CASE 16597 Published on 10.02.2020

The obturator hernia – the forgotten entity

Section

Abdominal imaging

Case Type

Clinical Cases

Authors

Luisa Nieto Morales, Efrén Santana Medina, Adán Bello Báez, Julián Portero Navarro

Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.

Corresponding author: yelgha@gobiernodecanarias.org

Patient

86 years, female

Categories
Area of Interest Abdomen ; Imaging Technique Conventional radiography, CT
Clinical History

We present the case of an 86-year-old female patient who presented with nausea, vomiting and left medial thigh pain. The patient had no history of surgery, abdominal trauma or intra-abdominal infection.

On examination, her abdomen was soft, mildly distended, with tenderness on palpation of the right iliac fossa and inability to pass gas, but clinically she exhibited no masses. She didn´t have high temperature or clinical sign of peritoneal irritation, except hyperactive bowel sounds.

No palpable hernia was located.

Imaging Findings

An abdominal X-ray obtained in a standing position revealed acute dilatation of stomach, dilated loops of small intestines and gas fluid levels (Fig. 1) with little gas passing to the large bowel.

Her computed tomography (CT) (Fig. 2 a-b) showed a small intestine loop completely herniated through the left obturator foramen (white arrow in a- b) and dilatation in the proximal small bowel (black arrows in a).

The patient was diagnosed with obturator hernia and after initial treatment with intravenous fluid and nasogastric suction, underwent surgery. During surgery, a small intestine segment extending through the left obturator foramen was detected. After reduction, the defect was closed with a surgical mesh. 

Postoperative period was uneventful. The patient had no recurrence of symptoms on subsequent follow-up.

Discussion

The obturator foramen is the large, obliquely-oriented, ovoid aperture located at the anterior aspect of both sides of the pelvis, bounded by parts of the ischium and pubis. It is covered by thin fibrous membrane, the obturator membrane, which is covered on the internal and external surfaces by the muscles obturator internus and obturator externus respectively. At its superior margin, the membrane is devoid forming the obturator canal which allows the obturator nerve, artery and vein to exit the pelvis and enter the medial compartment of the thigh [1].
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. 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, appendix, omentum, Meckel diverticulum, ovary/fallopian tube and even uterus [2].
The incidence of obturator hernia is between 0.05% and 1,4% of all abdominal hernias [3].
Obturator hernia affects women much more often than men due to their wider pelvis, more triangular obturator canal opening, and greater transverse diameter, and usually occurs in multiparous and elderly emaciated women. The other risk factors include chronic obstructive pulmonary disease, chronic constipation and ascites, and therefore the morbidity and mortality rates are high. The pain in the medial thigh of the affected side is due to compression of obturator nerve (Howship-Rombergsign (only present in approximately half of cases) [2,4]).
It occurs more frequently in right abdominal side; the presence of the sigmoid colon covering the left obturator canal is responsible for a lower incidence on that side [2].
The clinical diagnosis of an obturator hernia is often difficult because signs and symptoms resulting from obturator hernias are often vague and non-specific.
Yet early diagnosis is necessary because its delay contributes to bowel necrosis and to a worse prognosis in these patients.
Plain radiographs often show non-specific findings of small bowel obstruction and are seldom helpful in diagnosing obturator hernia. Noticing gas shadow in the obturator foramen area may be helpful. Barium enema or small bowel series can be helpful if a bowel loop is in the obturator canal, but barium study is more time consuming in diagnosing case of acute abdomen and retained barium in bowel loop may increase the risk of subsequent operation. Ultrasonography is useful and reliable in diagnosis of obturator hernia, but it is often limited by the relative inaccessibility of this deep region and operator-dependent. The common CT scan finding is low-density mass between obturator externus and pectineus muscle. The low-density mass may contain air density in some cases and apparently different from the opposite side. Associated bowel loop dilatation in the abdomen is common. CT scan can accurately diagnose not only obturator hernia but also other conditions of bowel obstruction [5].
Computed tomography must be used for diagnosis because of its high sensitivity and specificity rate [6,7].
Acute intestinal obstruction due to obturator hernia must be included in the differential diagnosis of any patient with no history of abdominal surgery, trauma or intraabdominal infection.

TEACHING POINTS
- Obturator hernia must be considered in the differential diagnosis of thin, elderly patients, especially female patients, admitted with symptoms of acute intestinal obstruction and no history of abdominal surgery, trauma or intraabdominal infection.
- CT scan is valuable to establish preoperative diagnosis, and has high sensitivity and specificity [6,7].
- Early surgical intervention is often hindered by clinical (symptoms are non-specific), and radiological diagnostic difficulty.
- It has a high rate of morbidity and mortality due to delayed diagnosis and treatment, and comorbidity of these patients.
Written informed patient consent for publication has been obtained.

Differential Diagnosis List
Acute intestinal obstruction secondary to an obturator hernia
Intestinal tumour
Inflammatory bowel disease
Inguinal hernia
Final Diagnosis
Acute intestinal obstruction secondary to an obturator hernia
Case information
URL: https://www.eurorad.org/case/16597
ISSN: 1563-4086