Cortical transit time: understanding utility and pitfalls in children with pelviureteric junction obstruction.

INTRODUCTION

Delayed cortical transit time (CTT) has been recently studied and proposed as a parameter that can predict the need for surgery in children with pelviureteric junction obstruction (PUJO).

AIM

The aim of this study was to study the change in CTT, after surgery, in children with PUJO and to correlate CTT with intrapelvic pressure of the kidney.

MATERIAL AND METHODS

A prospective study was performed, and all children who underwent pyeloplasty from January 2016 to December 2017 were included. Pre-operative and postoperative renal ultrasonography and Technetium-99m mercaptoacetyltriglycerine Tc-MAG3 renal scintigraphy were performed. Cortical transit time was measured by a visual method by two different observers. The renal intrapelvic pressure of the kidney was also measured during surgery after giving a diuretic to replicate the diuresis induced during the renal scan. The correlation was studied between the pre-operative CTT and intrapelvic pressures and between the pre-operative CTT and the renal function of the affected kidney.

RESULTS

Thirty-one children were included in the study. The median age of children who underwent surgery was 50 months (2-168). In 71% of patients, the CTT was prolonged before surgery, whereas only 22.5% had delayed CTT after surgery. The mean CTT before surgery was 226.1 ± 74.8 s and decreased to 165.4 ± 55.9 s after surgery (p= <0.001). The mean intrapelvic pressure was 21 ± 7.5 cm HO. There was no correlation noted between the intrapelvic pressure and the CTT. A significant negative correlation was noted between the CTT and the different renal function of the kidney.

DISCUSSION

This is the first prospective study that studies the changes in CTT after surgery. Only retrospective studies had been conducted to date which concluded that CTT was delayed in most of the patients who had been operated. It has been proposed that the prolonged CTT is due to raised pressure in the kidney secondary to obstruction. This study did not find any correlation between the pressure and CTT. The significant negative correlation between CTT and renal function also emphasizes the need to take the renal function into consideration before interpreting and using the absolute value of CTT for guiding treatment.

CONCLUSION

Cortical transit time assessment by the visual method is a useful parameter in the management of children with PUJO. There is a significant improvement in CTT after surgery.