Authors' reply.

Sir,

We appreciate the interest shown by Dr. Chandrasekharam and colleagues in our study. We take this opportunity to provide the details which are not in the original paper[1] and also to answer the raised queries. Most of the patients included in our study were of asymptomatic antenatally diagnosed hydronephrosis (HDN); however, we also had patients (n=11) who presented with history of urinary tract infection (UTI), loin lump and loin pain. As mentioned in the report, bacterial culture positive urine samples were excluded from the study as we do not know the effect of active UTI on the level of urinary enzymes. The baseline mean levels of urinary enzyme N-acetyl-β-glucosamidase (NAG) in symptomatic patients with Group B, asymptomatic patients in Group B and patients in Group A was 10.1 mU/mg of creatinine, 7.25 mU/mg of creatinine and 3.93 mU/mg of creatinine respectively (P<0.0001, Annova test). This correlates with the poor mean split renal function (SRF) in the symptomatic patients (22.3%), when compared with the mean SRF of 45.4 % (supranormal function excluded) in asymptomatic patients (P<0.0001). So SRF decreases and the level of NAG rises if we wait for the child to become symptomatic. There was no significant difference between the mean levels of AKP and GGT between the symptomatic and asymptomatic patients.

Dr. Chandrasekharam mentioned 3 groups of patients with HDN due to PUJO, our experience shows that there is also a fourth group of patients with non obstructive renogram curve and compromised renal function and actually it is in this group that the management remains controversial. As per department protocol, we take into consideration the collaborative findings of USG, IVP and renal scintigraphy to decide on the need of pyeloplasty in patients with HDN due to PUJO. We consider that obstructive curve on scintigraphy is a more significant indicator of surgical requirement than compromised split renal function because surgery can relieve the obstruction but may or may not improve the SRF. As this was our first experience in studying urinary enzymes, we did not include the patient category in which the management guidelines are controversial. But as our initial results are encouraging, we will plan to study the role of urinary enzymes in this group of patients as well. Coming to obstructed kidneys with normal function, we have data of 21 such patients and yes, the level of all the three enzymes was significantly high in these patients when compared with non obstructed kidneys (NAG – 6.71 units vs 3.93 units, P=0.0007; AKP – 0.0188 units vs 0.0101 units, P=0.03; GGT – 14.6 units vs 11.6 units, P=0.017) respectively.

We agree that ultrasonography (USG) is an important investigation modality in these patients, but it also should be remembered that USG is also operator dependant and is not standardized like renography in deciding the need of pyeloplasty. A study by Keays et al.,[2] showed that the intraobserver agreement in grading HDN as per society of fetal urology was in the range of 63 to 90%. Another study by Pereira et al.,[3] had shown that the overall percentage of agreement in grading hydronephrosis by two sonologists was only 64%. As the study of urinary enzymes was new in the context of HDN due to PUJO, we compared it with the established and objective investigation i.e., renography. We do have the USG findings like anterior posterior diameter of renal pelvis and cortical thickness for most of our patients and the results of which will be submitted in our future reports.