A sign on CT that predicts a hazardous ureteral anomaly

An aberrant course of the distal ureter can pose a risk of ureteral injury during surgery for inguinal hernia repair and other groin operations. In a recent case series of inguinoscrotal hernation of the ureter, we found that each affected ureter was markedly anterior to the psoas muscle at its mid-point on abdominal CT. We hypothesized that this abnormality in the abdominal course of the ureter would predict the potentially hazardous aberrant course of the distal ureter.

We reviewed all evaluable CT urograms performed at St. Louis University Hospital from June 2012 to July 2013 and measured the ureteral course at several anatomically fixed points.

93% (50/54) of ureters deviated by less than 1cm from the psoas muscle in their mid-course (at the level of the L4 vertebra). Reasons for anterior deviation of the ureter in this study included morbid obesity with prominent retroperitoneal fat, congenital renal abnormality, and post-traumatic renal/retroperitoneal hematoma. We determined that the optimal level on abdominal CT to detect the displaced ureter was the mid-body of the L4 vertebra.

Anterior deviation of the ureter in its mid-course appears to predict inguinoscrotal herniation of the ureter. This finding is a sensitive predictor and should raise concern for this anomaly in the appropriate clinical setting. It is not entirely specific as morbid obesity and congenital anomalies may result in a similar imaging appearance. We believe that this association has not been reported previously. Awareness of this anomaly can have significant operative implications.