I Thought I Saw a Retrocaval Ureter; Don't Bite the Fish-Hook Sign So Easily.

Background: During the management of patients with hydronephrosis, a possibility of retrocaval ureter (RCU) may emerge indicated by a fish-hook sign or its mimickers. Owing to infrequent incidence, the proper way to diagnose or exclude an RCU is challenging and has not been discussed previously. Methods: The aim of this study was to retrospectively evaluate the children who were suspected to have an RCU during management for urinary tract dilation. An RCU may be missed or misdiagnosed owing to rare incidence. Results: The children with urinary tract dilation in whom RCU was considered are enrolled in the study ( n  = 13). The demographics of the patients, findings suggesting RCU, evaluation process, management, and final diagnosis are retrospectively evaluated. The final diagnosis of the patients was RCU ( n  = 4), ureteropelvic junction obstruction (UPJO) ( n  = 7), and duplicated collecting system ( n  = 2). An RCU was confirmed or excluded by ultrasonography (US) while there was a stent in the ureter in 6 patients and by laparoscopic exploration in the other 7 patients. Four underwent correction for RCU, 7 for UPJO, 1 for reflux, and 1 ureterocele puncture. Conclusion: The fish-hook sign is a rare conflicting radiological finding that can be encountered in imaging studies. This uncommon finding needs confirmation or exclusion of a possible RCU as missed cases manifested after failed pyeloplasty or ureteroneocystostomy were reported. Radiological evaluation (by US or cross-sectional studies) while there is a stent in the ureter is the most satisfactory radiological technique to confirm or exclude an RCU. Alternatively, being aware of a possible RCU and performing a more extensive dissection may be necessary during surgery to confirm or exclude it. If available, laparoscopy may provide this goal in a minimally invasive manner with superior visualization.