Hook Phenomenon Intermittent distal ureteral obstruction following reimplantation

Background/Objectives:Toevaluatethechildwithintermittentureteralobstructionfollowing antireflux surgery and to introduce a new imaging technique for diagnosis of the socalled “hook”phenomenon,themostseriouscomplicationofantirefluxsurgery. PatientsandMethods:Twenty-fivechildrenwitha historyofantirefluxsurgerywhowere referredforeitherpersistenturinarytractinfection(UTI)orprogressivehydronephrosiswere included in the study. All the children with signs and symptoms of voiding dysfunction or persistentrefluxwereexcluded. A newimagingtechniquewasdevisedtoevaluatethesepatientsforthepresenceof“hook phenomenon”, inwhicha renalultrasoundwasperformedbothona full bladderand after voiding. If dilatation of the urinary tract was detected on full bladder, and this dilatation decreased dramatically followingmicturition, then a catheterwas passed into the bladder andwasfilledwithnormalsaline(basedontheestimatedbladdercapacityinordertoavoid over-distension).An intravenousurogramandsalinecystogramwereperformed simultaneously. After20minutes,2 abdominalradiographswereobtainedonfullandemptiedbladder, both. Results:Onthe intravenousurogram,somechildrenshowedtypical “J-hook-shaped”ureters. In all the cases marked hydronephrosis was noted, with no contrast material seen entering the bladder on the 20minute radiogram. Upon evacuation of the bladder, both ureters promptly drained into the bladder and the”J-hooking” of the ureters and hydronephrosis resolved. Conclusion: "J- hook phenomenon” is one of themost common causes of hydronephrosis andhydroureter followingureteral re-implantation is intermittentureteralobstruction from creationofthenewureteralhiatusataninappropriatesite.Thiscomplicationisfrequently misdiagnosed as irreversible uretero-vesical junction obstruction from ischemia or fibrosis. Oncethediagnosisof“J-hook”phenomenonisconfirmed,earlyureteralreimplantationwith creationofa newhiatusisthetreatmentofchoice.