Interpretation of the renogram: problems and pitfalls in hydronephrosis in children

To discuss the main steps of renographic technique and underline some pitfalls related to the acquisition, processing and interpretation of diuretic renography, an important method for guiding the management of asymptomatic congenital hydronephrosis.

Despite guidelines and consensus protocols, renographic procedures differ among centres, causing difficulties in comparison and controversy in the interpretation of results. Thus we comprehensively assessed published papers on the subject of diuretic renography.

Differential renal function (DRF) is a robust measure provided there is adequate background subtraction. Pitfalls are related to the drawing of regions of interest, particularly in infants, to estimating the interval during which DRF is calculated, and to an adequate signal-to-noise ratio. There is no definition of a 'significant' reduction in DRF. The classical variables of the diuretic renogram may not allow an estimate of the best drainage. Poor pelvic emptying may be apparent because the bladder is full and because the effect of gravity on drainage is incomplete. Estimating the drainage as residual activity rather than any parameter on the slope might be more adequate, especially if the time of frusemide administration is changed. Renal function and pelvic volume can influence the quality of drainage. Drainage may be better estimated using new tools.

Provided the investigation is standardized and potential pitfalls accounted for, the diuretic renogram provides valuable and reproducible quantitative information on DRF and drainage.