Anterior retroperitoneal herniation of the lumbar disk causing hydronephrosis: Case report with a review of literatures

There are some reports about the extreme lateral disk herniation mimicking a retroperitoneal neoplasm or a nerve sheath tumor. To date, however, few cases of anterior herniation of the disk have been reported and it is more frequently confused with a retroperitoneal neoplasm than the extreme lateral disk herniation. Recently, we experienced an extremely rare case of anterior herniation of the lumbar disk causing hydronephrosis. A 76-year-old man was presented to our institution with a 6-month-history of left flank and back pain. On neurological examination, the straight leg raising test was negative. The patient did not present with any clinical findings that are suggestive of the radiculopathy due to herniated disk. A computed tomography showed a slightly contrast-enhanced mass in the left upper ureter, accompanied by a hydronephrosis; however, its margin was ill defined from the L3/L4 disk space. We, therefore, made a tentative diagnosis of the ureteral tumor and planned left nephroureterectomy. Intraoperatively, there was an ill-defined mass encasing the left upper ureter which was extending up to the left psoas major muscle and lumbar spine. With total extirpation of the mass, the patient had an approximately 15-mm-sized opening of the anterior longitudinal ligament, which was suggestive of ruptured intervertebral disk herniation. On final histology, the patient had a reactive inflammatory mass around the left ureter without evidence of carcinoma. We present a rare case of anterior disk herniation that was misdiagnosed as a retroperitoneal tumor causing hydronephrosis.