Projects

Among the antenatally detected fetal anomalies, 20–50% involve the genitourinary system and 50% of these manifest as hydronephrosis [1]. The incidence of antenatally detected hydronephrosis is 2–9 per 1,000 live births, the prevalence being 0.6–5.4% [2, 3]. Postnatal imaging shows resolution of hydronephrosis in 41–88% of these infants. Intervention is warranted only in a small percentage of children; of which pelvi-ureteric junction obstruction is the most common [4]. Hydronephrosis with antero-posterior pelvic diameter (APPD)>10  mm persisting postnatally necessitates evaluation using an isotope diuretic renogram to confirm obstruction [5]. Advancements in Doppler ultrasound have helped in better understanding of renal physiology and enable the detection of subtle renal blood flow changes associated with various pathophysiological conditions. These changes may be quantified by calculating the intrarenal vascular resistive index (RI) which is a reliable indicator of obstruction and is helpful to differentiate obstructive from non-obstructive hydronephrosis [6–8]. The perfusion index (PI) first interpreted by Hilson in 1976 in renal transplant units serves as a good indicator of vascular perfusion of the affected renal unit which improves after appropriate surgical intervention [9]. The resistive index (RI) of>0.7 and the resistive index ratio (RIR) of>1.1 signify obstruction and comply well with the results of isotope diuretic renogram [10, 11]. Thus far, there has been no correlative analysis between Doppler ultrasonography (RI, RIR) and diuretic renogram (PI), in obstructed and non-obstructed kidneys. This study aimed to analyse these values in unilateral hydronephrosis and look for any correlation. Methods This is a single-centre, prospective study conducted in the Department of Paediatric Surgery, over 36  months (2016–2019) based on a departmental protocol as depicted in Fig.  1. All infants with unilateral hydronephrosis and APPD>15  mm were included in the study and those with APPD<15 mm, bilateral hydronephrosis, unilateral/bilateral hydroureteronephrosis, solitary kidneys with hydronephrosis were excluded. Our departmental protocol is formulated based on the “Revised guidelines on management of antenatal hydronephrosis” by Indian society of Paediatric Nephrology (ISPN) with minor modifications. All infants with hydronephrosis underwent renal function test, urine culture and a renal ultrasound to assess the APPD. Infants with unilateral hydronephrosis and APPD > 15  mm were further subdivided into two groups based on their age at diagnosis, i.e. Group A (0–6  months) and Group B (6–12  months). These underwent a Doppler ultrasonography initially to document the resistive index, i.e. (peak systolic velocity−lowest diastolic velocity)/peak systolic velocity) in the intersegmental arteries of the affected kidney, and resistive index ratio, i.e. (RI of hydronephrotic kidney/ RI of normal kidney), performed by a single experienced radiologist. An isotope diuretic EC renogram was then performed to confirm the obstruction, and the perfusion index, i.e. (Hilson’s Index=area under arterial curve to peak/area under renal curve×100), was recorded apart from other parameters like intra renal transit, tracer hold up, t 1/2 for tracer clearance.