Obturator hernia: Clinically elusive and radiologically effortless
Obturator hernias are rarely suspected because they are almost never seen and rarely palpated. Although their real incidence is un?known, these hernias are thought to constitute fewer than 1% of all hernias world?wide.1,2 Bjork and colleagues re?ported their incidence at about 0.073% of all hernias repaired at the Mayo Clinic.3
The formation of an obturator hernia is initiated by preperitoneal fat entering the obturator foramen, the largest and strongest foramen in the body. Little else is known about predisposing factors, but weight loss, cachexia, and advanced age contribute.1 Clinically, between 71% and 80% of obturator hernias present as small bowel obstruction. The most common indicator (found in 40%?50% of pa?tients) is the Howship-Romberg sign, which includes pain with or without paresthesias felt down the anteromedial thigh to the knee upon movement of the hip or thigh. Other symptoms include recurrent attacks of obstruction that resolve spontaneously, weight loss or emaciation, and, although rarely, a palpable mass.4
Treating an obturator hernia varies from reduction of the hernia while leaving the defect untouched to closing the defect using sutures, mesh, or a patch. Currently, it is accepted that closing the defect is essential, although the rate of recurrence without closure is unknown.5 Bowel resection for ischemia is likely during surgery, and it is recommended that the hernia be repaired immediately after primary anastomosis of the bowel.
The purpose of this case report is to exemplify the difficulty in making a preoperative diagnosis of obturator hernia unless there is a high index of suspicion for this rare entity. Once diagnosed, treatment is straightforward and the prognosis is generally good.
A frail, cachectic, emaciated, 84-year-old white woman presented to the emergency department reporting abdominal distension, nausea, emesis, and constipation of 4 days' duration. She was a nursing home resident, and her medical history was unremarkable and did not include any previous abdominal surgery. The patient was dehydrated and tachycardic. There was diffuse abdominal distension and tenderness on palpation with hyperactive bowel sounds on auscultation. Initial abdominal radiographs dem?on?strated dilated loops of small bowel, consistent with obstruction. She was admitted to the ward for medical management.
Computed tomography (CT) scans of her abdomen and pelvis were performed, which were interpreted as showing a partial small bowel obstruction without an obvious transition point (Figure). No hernia was identified. After 24 hours of unsatisfactory medical management, the surgery department was consulted. The CT scans were reviewed once more with the radiology department, and careful analysis identified a right obturator hernia (Figure). After further detailed questioning, the patient relayed symptoms consistent with a positive Howship-Romberg sign, although she attributed the pain to hip arthritis.
The patient was taken to the operating room for an exploratory laparotomy, which confirmed a right obturator hernia with strangulated small bowel. Re?duc?tion of the involved segment and re?section with primary anastomosis (side-to-side functional end-to-end anastomosis) were undertaken, followed by primary repair of the defect using a single polypropylene figure-of-eight suture, avoiding the entrapment of the obturator vessels and the obturator nerve. After the procedure, supportive total parenteral nutrition was started, and the patient was transferred to the intensive care unit, where she re?mained for 48 hours. As she slowly im?proved, an enteral diet was tolerated and parenteral nutrition was discontinued. After 12 days in the hospital and an un?eventful recovery, she was discharged to the nursing home.
As this case exemplifies, correctly diagnosing an obturator hernia preoperatively is exceptionally difficult. Most cases are seen in debilitated women, occurring after loss of the protective fat in the obturator canal. Many obturator hernias present as mechanical small bowel obstruction which fails to resolve, leading to exploratory laparotomy and subsequent discovery of the hernia. CT scanning or other radiologic studies may be helpful for establishing the diagnosis and planning surgical intervention.6,7 CT scans may demonstrate a low-density mass that lies between the obturator externus and pectineus muscles, contributing to a successful diagnosis in most cases.8 The combination of acute small bowel ob?struction and a Howship-Romberg sign in a thin, frail, elderly woman with no history of abdominal surgery is highly suggestive of an obturator hernia.
It is recommended that the defect be identified and closed, but which type of repair to use is solely the surgeons' preference. The hernia can be successfully repaired with a range of methods from single suture closure or synthetic mesh employed in a plug and patch fashion to more elaborate techniques that use the urinary bladder, uterine fundus, and round ligament or pectineus muscle.9-11 In our case, we thought it appropriate to close the defect with a single polypropylene suture due to the ease of this technique and the defect's small opening.
During the operation, it is critical to identify the three structures (artery, vein, and nerve) that go through the foramen and avoid them in the repair. When one encounters a loop of small bowel incarcerated in the hernia, which is the most common intraoperative finding, it is advised to employ gentle traction on the bowel segment and attempt to stretch the defect.12 If that is not possible, the obturator membrane can be safely incised in its lower margin, because in more than 50% of cases, the sac lies just superior to this border and below the vessels and nerve.1
The jejunum and ileum should be in?spected thoroughly to assess the need for resection and anastomosis, which is required in fewer than half of obturator hernia patients.1,13 In our patient, a segment of ileum was incarcerated in the defect and an area of ischemia was identified, which prompted the decision to resect and anastomose. The defect was then inspected and closure was performed as stated previously under direct visualization of the obturator vessels and nerve.
The clinical course for patients with an obturator hernia is usually favorable, even though many patients, like ours, require small bowel resection. The reported mortality rate for the procedure is between 8% and 13%, with a higher rate of mortality in Asians and Africans.1,12 Most of the mortalities occur secondary to cardiovascular events, peritonitis, and pulmonary embolism and are linked more to associated comorbidities and underlying preoperative status than to the procedure itself.1
An obturator hernia is one of the rarest of the abdominal wall hernias. It is difficult to diagnose preoperatively unless there is a high index of suspicion. Clin?icians should include obturator hernia in the differential diagnosis of any malnourished, elderly woman presenting with a Howship-Romberg sign and no history of abdominal surgery. CT scanning plays a key role in diagnosing this condition early. In our case, careful review of ab?dominal and pelvic CT scans and recognition of the patient's description of hip pain as a Howship-Romberg sign were instrumental in making the diagnosis preoperatively. Intra??operative assessment of the defect and repair are necessary. Small bowel resection should be performed when the segment of bowel in?volved is not viable.
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