Ultrasound in diagnosis of retroperitoneal femoral nerve injury: a case report.

We present a case of retroperitoneal femoral nerve injury after cut wounds at the lower abdomen. Electrodiagnostic tests revealed impaired function of nerve and muscles. A mass was observed at the retroperitoneal part of the femoral nerve by ultrasound, indicating that a traumatic neuroma composed of disordered fascicles was configurated after the injury. Postoperative pathology confirmed hypertrophic and hyperplastic nerve bundles of the mass. Great improvements were shown in the patient's symptoms and electrodiagnostic tests in the subsequent 3 months. This case presented a rare position of neuroma formation by ultrasound.