A sign on CT that predicts a hazardous ureteral anomaly

INTRODUCTION: 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. PRESENTATION OF CASES: 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. DISCUSSION: 93% (50/54) of ureters deviated by less than 1 cm 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. CONCLUSION: 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.