The Disappearance of One Half of a Horseshoe Kidney

摘要

An infant girl was seen 3 weeks after birth to evaluate her kidneys because of an antenatal ultrasound diagnosis of right hydronephrosis. A postnatal Tc-99m MAG3study revealed a horseshoe kidney with the right component being smaller than the left. The girl was seen again at 4.5 years with urinary incontinence that involved a constant drip of urine that left her never completely dry. Cystoscopic examination revealed a deficient bladder neck. The left ureteric orifice was located intravesically but the right ureteric orifice ended ectopically at the urethral-vaginal septum. It was unclear whether the child's incontinence resulted from the incompetent bladder neck or from urine draining from the ectopic right ureter, which opened distal to the urethral sphincter. A Tc-99m DMSA study revealed that there was no residual function in the right component of the horseshoe kidney, with only a normal left kidney now seen. The sequence of studies indicated an unusual regression of a hemicomponent of a horseshoe kidney.