Response to: Hydronephrosis due to pelviureteric junction narrowing: Utility of urinary enzymes to predict the need for surgical management and follow up.

Sir,

We read with interest the article by Rathod et al.,[1] on the use of urinary enzymes in the evaluation and follow up of children with pelviureteric obstruction (PUJO). They reported a significant difference in urinary enzyme levels between children with nonobstructive hydronephrosis (HDN) versus those with obstructive HDN. We appreciate their efforts to document urinary enzyme levels in children with PUJO. However, we offer the following comments.

The clinical presentation of the patients in their series has not been mentioned. Is it possible that presentation with urinary infection or pain may affect urinary enzyme levels? Was there any difference in urinary enzyme levels between symptomatic and asymptomatic children in Group B? Similarly, it would be important to compare urinary enzyme levels between their patients with antenatal hydronephrosis (HDN) versus those who presented with symptoms like pain, palpable mass or urinary tract infection

There are three distinct groups of PUJO type HDN that we see in practice: nonobstructive HDN that does not require surgery (Group A in Rathod's article), obstructive HDN with compromised function that definitely requires surgery (Group B in the article) and a third group of asymptomatic obstructive HDN with preserved function. The management decision in the first two groups is fairly straightforward, and Rathod et al., have compared the urinary enzyme levels in these two groups. However, the third group is the most difficult to manage, since despite severe obstructive HDN, these kidneys have preserved function and most improve with expectant management[2-4] while pyeloplasty will be required in 20-25% of these kidneys.The problem is how to identify these kidneys that would deteriorate later and require surgery. Bajpai et al.,[5] investigated the role of captopril renography and showed that it had 100% sensitivity and 75% specificity in correctly identifying the patients who subsequently required surgery for PUJO. In this context, a noninvasive and simple test such as measurement of urinary enzyme levels would be ideal to identify the patients who would require surgery in future. However, Rathod's article has not investigated the urinary enzyme levels in the third group (obstructed kidneys with preserved function).

The authors utilized the measurement of urinary enzyme levels as a noninvasive test to identify children with PUJO who require surgery and also in the postoperative follow up. However, no mention has been made regarding the ultrasound (USG) findings in their patients. USG, which is widely available, reliable and quick, is the most common noninvasive test currently used to monitor and follow up PUJO. In fact, it is the first test, the findings of which serve as a roadmap for further investigations and management plan. Mami et al.,[6] reported that USG could reliably be used to follow children with even moderate to severe HDN expectantly, while more invasive tests like diuretic renography are required only in a small number of such children. They used renal pelvic anteroposterior diameter (APD) as a criteria to follow these children and reported that in most children, HDN with APD <20 mm is a self-limiting condition. Similarly, Longpre et al.,[7] evaluated and followed up 100 children with antenatally detected HDN using USG examinations. They reported that initial APD of <20 mm had a positive predictive value of 83% for spontaneous resolution of HDN. In terms of postoperative follow up, Cost et al.,[8] reported on the use of USG to follow up children after pyeloplasty. Their results strongly support the use of ultrasound as an adequate and accurate postoperative imaging modality to determine the success of pyeloplasty. Thus, any noninvasive modality used in the assessment and follow up of HDN in children should be compared with USG findings.

In conclusion, although the observations made in this study are of great interest, further information is required before making urinary biomarkers a standard in the assessment and follow up of children with HDN. We congratulate the authors and encourage them to try and answer these important questions on the use of biomarkers in children in their future reports.