THE NONOPERATIVE MANAGEMENT OF UNILATERAL NEONATAL HYDRONEPHROSIS - NATURAL-HISTORY OF POORLY FUNCTIONING KIDNEYS

During the last 5 years we have followed nonoperatively all neonates w ith unilateral hydronephrosis and suspected ureteropelvic junction obs truction, regardless of the degree of hydronephrosis, shape of the diu retic renogram washout curve or initial degree of functional impairmen t. Of 104 patients 7 (7%) ultimately required pyeloplasty for obstruct ion, which was defined as a greater than 10% reduction in differential glomerular filtration rate and/or progression of hydronephrosis. Pyel oplasty returned renal function to pre-deterioration levels in all kid neys. In 16 patients with profound hydronephrosis and initial differen tial renal function less than or equal to 40% all traditional diagnost ic tests for assessing obstruction, including diuretic renography wash out pattern, were inaccurate in diagnosing obstruction and predicting which kidney would deteriorate. In 15 of 16 poorly functioning hydrone phrotic kidneys rapid improvement in absolute and per cent differentia l renal function was observed, and the level of initial differential r enal function served as a useful guide for timing of further diagnosti c studies. Unilateral neonatal hydronephrosis appears to be a relative ly benign condition and the risk of developing renal obstruction appea rs relatively slight. Because of diagnostic inaccuracy, the low risk o f developing obstructive injury and the fact that many newborn kidneys with hydronephrosis rapidly improve function and dilation, it appears safe to follow neonatal unilateral hydronephrosis closely and nonoper atively.