Editorial comment

Abstract

Many aspects of the natural history and functional outcome of childhood ureteropelvic junction obstruction remain unclear despite the extensive literature devoted to the topic. However, the method used by the authors differs from that used in most previously published studies. 123I-hippuran renography has been used to obtain an absolute measure of individual kidney function, whereas the functional information provided by the more widely used 99mTc-MAG-3 scan consists of comparative uptake or “split” distribution of function between the two kidneys. Earlier work is cited to endorse the validity of the AI, the functional parameter used in this study, as a measure of renal function in early childhood. The study population has been limited to children with “nonobstructive pattern findings on diuretic renography at follow-up” in whom the authors have then retrospectively characterized different clinical and renographic variables at the time of presentation. This approach should permit a more precise analysis of the relationship between relief of obstruction and recovery of function. However, as the authors acknowledged, the significance of improved function in infancy is difficult to assess at a time in life when the glomerular filtration rate is naturally increasing because of functional maturation of the kidney. Kidneys with significantly reduced function often continue to exhibit an abnormal drainage curve and reduced diuretic response despite successful relief of obstruction. Thus, a study confined only to kidneys showing “nonobstructive pattern findings on diuretic renography” at follow-up is likely to select for better function at the outset—and a greater potential for functional recovery after pyeloplasty.