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

Abstract

The role of diuretic renography has become central in cases of upper tract dilatation, and in the first paper in this section the difficulties in interpreting results in asymptomatic congenital hydronephrosis are examined. These difficulties and controversies exist despite the presence of guidelines and consensus protocols, probably because renography procedures differ among centres. The authors found that there is a need for renography to be standardized for the optimum value to be obtained from the procedure. There are three papers from Los Angeles which attempt to standardize the measurement of bladder compliance, from both the theoretical and clinical perspective, and which assess the detrusor pressure rise of a normal bladder when filled to capacity. OBJECTIVE 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. METHODS 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. RESULTS 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. CONCLUSION Provided the investigation is standardized and potential pitfalls accounted for, the diuretic renogram provides valuable and reproducible quantitative information on DRF and drainage.

Delayed decrease in differential renal function after successful pyeloplasty in children with unilateral antenatally detected hydronephrosis

“…This opinion is supported by other authors. 14,16 In contrast, some reports have suggested there might be a limitation of functional recovery of antenatally detected hydronephrosis. Fig.…”

“…However, there are currently no reliable methods and no strict criteria that define 'obstruction'. [13][14][15] Therefore evaluation of differential function of the affected kidney using renography seems to be the most objective and clinically useful value. At present change of DRF is the most important factor in management of asymptomatic hydronephrosis.…”

“…Eskild-Jensen et al 14 suggested that another possible reason for permanent loss of DRF after pyeloplasty is lack of compliance with the follow-up program. In their study, eight of 52 (15%) children with unilateral hydronephrosis had pyeloplasty because of decrease in DRF (Ն10%).…”

The Accuracy of Doppler Ultrasonography in the Followup of Pyeloplasty for Congenital Pelviureteric Junction Obstruction

“…9 On diuretic renogram, one or more of the following indices of obstruction were positive in all these patients: a half-time diuretic washout (T1/2) of > 20 mins, a differential renal function of < 40%. 2 These patients if eligible to undergo open pyeloplasty were considered for the study during the period between October 2013 and July 2016.…”

“…These imaging modalities need specific preparations and at times may be difficult to interpret. 1,2 This can lead to diagnostic dilemma and management difficulties. Chronic renal obstruction produces a state of increased vascular resistance detectable by Doppler ultrasound as an elevation in renal resistive index (RRI).…”