Obturator Hernia

Etiology

Formation of an obturator hernia is facilitated by anatomic factors that permit invagination of abdominal contents through the obturator foramen. Increasing age, female sex, multiparity, rapid weight loss, and malnutrition with emaciation weaken the pelvic floor and reduce the soft tissue that normally overlies the foramen.[7] Conditions that increase intra-abdominal pressure, such as chronic obstructive pulmonary disease, ascites, constipation, and chronic cough, further elevate the risk. The nature and severity of complications depend on the structures contained within the hernia sac and whether strangulation is present. Bowel involvement is most common, although the ovary, fallopian tube, ureter, and soft tissues may also protrude through the foramen.[8]

Epidemiology

Obturator hernias occur most frequently in women of advanced age and low body mass due to anatomic predisposition, including wide obturator foramina and weaker pelvic floor musculature.[9][10] The condition is sometimes referred to in the literature as the “little old lady’s hernia.” Obturator hernias account for approximately 0.05% to 2% of all hernias, with bilateral involvement reported in about 25% of cases. Right-sided obturator hernias are more common than left-sided ones, likely because the sigmoid colon overlies and shields the left obturator foramen.[11][12][13]

History and Physical

Patients with symptomatic obturator hernias most often present directly to the emergency department. Reported manifestations are typically nonspecific and may include nausea, vomiting, abdominal pain, pelvic pain, thigh pain, constipation, or hip pain radiating into the ipsilateral lower extremity, mimicking radiculopathy. Some patients describe prior episodes of similar symptoms that resolved without intervention.[14]

Affected individuals often appear uncomfortable on examination. Abdominal or pelvic tenderness and abdominal distension may be present, and signs of peritoneal irritation can occur in cases of bowel necrosis or perforation. The hernia sac is generally not palpable because of the deep location of the obturator foramen (see Image. Obturator Hernia Contents).[15][16]

Two physical examination signs are described, but neither is sufficiently sensitive nor specific to confirm or exclude the diagnosis. The Howship-Romberg sign is characterized by pain on adduction, extension, and medial rotation of the thigh caused by compression of the cutaneous branch of the obturator nerve by the hernia sac. The sensitivity of this finding is approximately 50%. The Hannington-Kiff sign is marked by loss of the thigh adductor reflex with preservation of the patellar reflex due to obturator nerve compression. This sign is elicited by placing a finger on the adductors 5 cm above the knee and percussing the finger with a tendon hammer. Muscle contraction indicates an intact reflex. The Hannington-Kiff sign is more specific than the Howship-Romberg sign but is technically more difficult and operator-dependent.[17][18]

Evaluation

Patients with a suspected obturator hernia should undergo a CT scan of the abdomen and pelvis with or without intravenous contrast.[19] CT can delineate the size and contents of the hernia sac and identify complications, such as bowel obstruction, necrosis, or perforation. Reported diagnostic accuracy is as high as 90%.[20] However, in some patients later diagnosed with obturator hernia during surgery, CT imaging either failed to identify the pathology or did not adequately characterize its features.[21] Surgical consultation for possible exploration is warranted when clinical suspicion persists despite the lack of evidence of abnormality on CT.

Pertinent laboratory evaluation includes complete blood count, comprehensive metabolic panel, blood typing and screening, and serum lactate measurement. Leukocytosis may occur in the setting of bowel obstruction, perforation, peritonitis, or as a stress response. Electrolyte abnormalities may result from vomiting, diarrhea, or volume depletion. Patients with ureteral herniation and obstruction may exhibit elevated blood urea nitrogen and creatinine. Blood typing and screening are useful for preoperative preparation. Elevated lactate may indicate bowel ischemia or necrosis.

Treatment / Management

Surgical Intervention

Surgery is required for the treatment of an obturator hernia. Surgical consultation should be sought emergently upon identification of the condition on imaging. In cases where the hernia contains only the ureter, repair may be delayed until renal function improves.

No universal consensus has been established regarding the optimal surgical approach. However, the methods most commonly employed to treat obturator hernias are midline laparotomy or laparoscopy, with minimally invasive robotic techniques becoming increasingly available.[22][23] Retropubic, inguinal, and femoral approaches have also been described.[24] Laparoscopic repair is preferred when feasible because it is associated with lower intraoperative blood loss, less postoperative pain, reduced risk of infection and ileus, and shorter hospitalization compared with laparotomy. Conversion to laparotomy may be undertaken intraoperatively if required.(B2)

The most frequently described laparoscopic techniques are transabdominal preperitoneal (TAPP) and total extraperitoneal (TEP) procedures. Most case reports describe reduction via the transabdominal preperitoneal approach, which permits direct visualization of the hernia contents and assessment of bowel viability.[25][26] If bowel resection is necessary, the surgeon may continue with this laparoscopic approach or switch to open surgery, depending on intraoperative findings. The total extraperitoneal technique is reserved for cases without suspected strangulation or necrosis and allows simultaneous repair of the inguinal and obturator spaces without entering the peritoneal cavity.(B3)

Several methods exist for closure of the obturator foramen to prevent recurrence. Defects smaller than 1 cm may be repaired directly with sutures, although suture repair may carry a higher risk of recurrence than mesh repair.

Mesh repair is reasonable if the bowel is viable or the defect is too large for primary closure. Large hernia defects may also be repaired with other tissues, such as a peritoneal or periosteal patch, omentum, or musculoaponeurotic flap, depending on surgeon preference.

Exploration of the opposite obturator foramen may be warranted if CT does not adequately exclude contralateral involvement, as some patients have bilateral obturator hernias. Concomitant inguinal or femoral hernias may also be present. Prophylactic repair of these incidental hernias is sometimes performed when detected intraoperatively to prevent future complications.[27]

Manual Reduction

Obturator hernias are generally not palpable and cannot be reduced manually, although rare successful reductions have been reported. Manual reduction is technically challenging, does not allow assessment of bowel viability, and carries a substantial risk of failure or recurrence. Cases of ultrasound-guided manual reduction followed by surgical repair have also been described.[28]

Differential Diagnosis

The differential diagnosis for abdominal pain, nausea, vomiting, or constipation is extensive. However, compared to younger individuals, older adults may not demonstrate typical symptoms or examination findings due to altered inflammatory and pain responses, putting this patient group at greater risk for obturator hernias. Important considerations include gastrointestinal disorders such as small or large bowel obstruction, ileus, intestinal perforation, gastritis, gastroenteritis, infectious or inflammatory colitis, volvulus, appendicitis, abdominal wall or inguinal hernia, diaphragmatic hernia, pancreatitis, biliary colic or cholecystitis, and hepatitis.

Cardiac causes, such as acute coronary syndrome, may obscure the manifestations of a surgical abdomen. Genitourinary conditions to consider include ovarian or testicular torsion and urinary tract infection or pyelonephritis. Vascular disorders, such as mesenteric ischemia, abdominal aortic aneurysm, and aortic dissection, should be differentiated from an obturator hernia. Metabolic disturbances that must be ruled out include diabetic ketoacidosis and hyperosmolar hyperglycemic nonketotic syndrome. Nonspecific causes of abdominal symptoms include medication adverse effects or withdrawal.

Prognosis

Historically, an obturator hernia diagnosis carried a substantial risk of morbidity and mortality. Improved outcomes in recent decades are likely attributable to increased clinical awareness, broader access to advanced CT imaging, and advances in surgical techniques.

Patients who undergo bowel resection may develop complications frequently associated with this procedure, such as ostomy dysfunction, anastomotic leaks, and intra-abdominal infection. Mesh placement for hernia repair carries potential risks of future mesh infection and migration. As with other major abdominal surgeries and hospitalizations, patients who undergo operative treatment for obturator hernia are also at risk for severe pain, infection, venous thromboembolism, skin breakdown, and deconditioning.

Reported mortality rates vary widely, from 12% to 70%. The persistently high figures are attributed to delays in diagnosis and treatment due to the nonspecific presentation of the condition, as well as the advanced age, frailty, and comorbidities common in the predisposed population.[29][30][31][32][33]

Complications

Protrusion of abdominal or pelvic contents through the obturator foramen may lead to obstruction or incarceration of viscera and occlusion of blood vessels. Bowel entrapment may cause obstruction, strangulation, necrosis, or perforation with subsequent peritonitis and sepsis. Ureteral herniation can lead to hydronephrosis and renal dysfunction. Obturator nerve compression may produce pain, paresthesia, or weakness in this neural structure's sensory and motor distribution.

Obturator hernias carry a small risk of recurrence, whether repaired with sutures or mesh. Patients with symptoms suggestive of this condition should be evaluated for recurrence even after prior repair. Herniation on the contralateral side may also occur.

The incidence of complications following obturator hernia repair is approximately 11%. The sequelae resemble those seen in other major abdominal surgeries, including wound infection, wound dehiscence, pneumonia, pulmonary embolism, sepsis, and anastomotic leak. Mesh placement may result in infection or migration. Intraoperative and postoperative risks depend on the surgical approach, the extent of tissue necrosis, the presence of intestinal perforation, and preexisting comorbidities.