Hook Phenomenon: Intermittent distal Uretaral Obstruction following reimplantation

Background/ To evaluate the child with intermittent ureteral obstruction following antireflux surgery and to introduce a new imaging technique for diagnosis of the socalled “hook” phenomenon, the most serious complication of antireflux surgery. Patients and Twenty-five children with a history of antireflux surgery who were referred for either persistent urinary tract infection (UTI) or progressive hydronephrosis were included in the study. All the children with signs and symptoms of voiding dysfunction or persistent reflux were excluded. A new imaging technique was devised to evaluate these patients for the presence of “hook phenomenon”, in which a renal ultrasound was performed both on a full bladder and after voiding. If dilatation of the urinary tract was detected on full bladder, and this dilatation decreased dramatically following micturition, then a catheter was passed into the bladder and was filled with normal saline (based on the estimated bladder capacity in order to avoid over-distension). An intravenous urogram and saline cystogram were performed simultaneously. After 20 minutes, 2 abdominal radiographs were obtained on full and emptied bladder, both. On the intravenous urogram, some children showed typical “J- hook-shaped” ureters. In all the cases marked hydronephrosis was noted, with no contrast material seen entering the bladder on the 20 minute radiogram. Upon evacuation of the bladder, both ureters promptly drained into the bladder and the”J-hooking” of the ureters and hydronephrosis resolved. "J- hook phenomenon” is one of the most common causes of hydronephrosis and hydroureter following ureteral re-implantation is intermittent ureteral obstruction from creation of the new ureteral hiatus at an inappropriate site. This complication is frequently misdiagnosed as irreversible uretero-vesical junction obstruction from ischemia or fibrosis. Once the diagnosis of “J- hook” phenomenon is confirmed, early ureteral reimplantation with creation of a new hiatus is the treatment of choice.