[High ureteral insertion as the cause of extreme hydronephrosis in a 5-year-old child with horseshoe kidney].

The incidence of horseshoe kidney is 1 per 400-800 live births. From 44-52% of the patients with horseshoe kidney have other coexisting abnormalities of the urinary tract, such as hydronephrosis, vesicoureteral reflux and a duplex collecting system. Our patient, a 5-year old boy, was admitted to a pediatric nephrology department because of abdominal pain and vomiting. He had ultrasonography of the abdomen performed for the first time at the age of 9-months and horseshoe kidney was shown. In a control ultrasonography, a mild dilatation of the pyelocalyceal system in the left kidney was described. On the day of admission, an abdominal ultrasound confirmed horseshoe kidney with large left hydronephrosis. Power Doppler ultrasonography showed two renal arteries to the left kidney and no arterial compression on the ureter. Dynamic scintigraphy (99mTc-EC) revealed left-sided hydronephrosis with high isotope intake up to 55% ERPF, a prolonged time of tissue perfusion and signs of subpelvic junction obstruction. Magnetic resonance urography presented an enlarged left kidney, with a diameter of up to 105 mm, a narrow renal cortex, a dilated renal pelvis up to 39 mm in diameter, dilated calyces up to 26-32 mm, and the high insertion of the ureter from the pelvis. The right kidney was normal. To facilitate drainage from the dilated collecting system of the left kidney, a double-J catheter was inserted. Pyeloplasty is planned as the next step of treatment. Conclusion: In a child with horseshoe kidney and a mild dilatation of the collecting system detected in infancy, long-term follow up is necessary, because of the increased risk of significant hydronephrosis in the future.