Diuretic renography in hydronephrosis: a retrospective single-center study

Ureteropelvic junction obstruction (UPJO) is one of the most common causes of hydronephrosis other than transient hydronephrosis. In children with unilateral hydronephrosis, mercaptoacetyltriglycine-3 diuretic renography (MAG₃) is used to calculate differential renal function and to assess drainage. The aim of our study is to examine whether anteroposterior pelvic diameter on renal ultrasound (US) scan can predict both differential renal function (DFR) and obstruction in pediatric patients, and whether an US adequately identifies those patients who need further investigation. We also aimed to design a study with a larger sample size than previous studies investigating the relationship between MAG₃ and US.

We retrospectively reviewed the MAG₃, US, dimercaptosuccinic acid scan (DMSA) findings, and medical records of pediatric patients with hydronephrosis and/or atrophy who were at follow-up between January 2013 and December 2016 in our center which is located in the south-east region of Turkey.

Two hundred and twenty-five pediatric patients (M/F = 156/69) with unilateral hydronephrosis but without VUR were enrolled in this study. The mean age of the children was 45.4 ± 48.3 months (range 2–173 months). Sixty-nine patients had obstructive pattern on ^99mTc-MAG₃. With respect to obstructive pattern, there was a significant difference between the hydronephrosis groups both with 15 and 20 mm border. An APD of greater than 20 mm had 15.8 times (95% CI 5.72–43.69) higher likelihood of having obstruction MAG3 findings. On the other hand, an APD of greater than 15 cm had 9.2 times (95% CI 3.01–28.57) higher likelihood of having obstruction MAG₃ findings. The incidence of urinary tract infections was lower than in the obstructive group than the other groups. The regression analysis showed that an APD of greater than 20 mm was a risk factor for low DRF (OR = 5.208, 95% CI 1.529–17.743, p = 0.008). However, the regression analysis showed that an APD of greater than 15 mm was not a risk factor low DRF.

The combination of ultrasound and MAG₃ provides the necessary anatomical and functional information to follow the degree of obstruction and to decide between surgical intervention and conservative follow-up. Our study supports a threshold of 20 mm rather than 15 mm for severe obstruction and a low DRF. An APD threshold greater than 15 mm did not have a predictive value in DRF estimation.