Importance: Occult hernias are symptomatic but not palpable on physical examination. This is more commonly seen with inguinal hernias. Early diagnosis and treatment of occult hernias are essential in relieving symptoms and improving patients' quality of life.

Objective: To determine the effectiveness of imaging-ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI)--in the diagnosis of occult inguinal hernia.

Design, setting, and participants: A retrospective medical records review of surgical patients with groin and pelvic pain, 2008-2013, was conducted in a single-surgeon hernia specialty practice. Thirty-six patients met the following inclusion criteria: (1) examination findings suggestive of but not necessarily diagnostic for inguinal hernia; (2) imaging of the groin and/or pelvis with US, CT, and MRI; and (3) an operation to address the groin or pelvic pain. Fifty-nine groins were included.

Main outcomes and measures: Sensitivity, specificity, and predictive values of US, CT, and MRI for detection of occult inguinal hernia.

Results: The number, sensitivity, specificity, positive predictive value, and negative predictive value of each modality were, respectively: US (9, 0.33, 0, 1.00, and 0), CT (39, 0.54, 0.25, 0.86, and 0.06), and MRI (34, 0.91, 0.92, 0.95, and 0.85). Among multiply imaged groins in which CT examination missed a diagnosis of hernia, MRI correctly detected an occult hernia in 10 of 11 cases (91%).

Conclusions and relevance: Ultrasonography and CT cannot reliably exclude occult groin abnormalities. Patients with clinical suspicion of inguinal hernia should undergo MRI as the definitive radiologic examination.