The clinical value of 99mTc-MAG3 renal scintigraphy in the follow-up of patients after pyeloplasty for unilateral pelvic-ureteric junction obstruction
Abstract
The Aim: To evaluate the clinical benefit of 99mTc-MAG3 study in the follow-up of children who underwent unilateral pyeloplasty and the need of 99mTc-MAG3 routine post-operative performance. Methods: A retrospective analysis of medical records of all patients aged 0 to 18 years who underwent unilateral pyeloplasty for pelvic-ureteric junction (PUJ) obstruction between January 2011 and January 2015 was performed.
Included into the study were all patients investigated by both, 99mTc-MAG3 and ultrasound scan (USS), before and after pyeloplasty. Excluded were all patients with bilateral hydronephrosis, conjoint vesico-ureteric reflux, solitary kidney, horseshoe kidney and all lost to follow-up.
We compared the anterio-posterior (AP) diameter of the renal pelvis on the last follow-up before and the last follow-up after the operation, as well as the differential renal function (DFR) on 99mTc-MAG3 scan. Any change in DRF exceeding 5 % was considered significant.
Results: In the above mentioned period we performed 80 pyeloplasties. 48 patients were included into the analysis, aged 1.5 months to 17 years (3.6 years on average). In 42 patients we performed standard open Anderson-Hynes pyeloplasty and in 6 laparoscopic procedure (age range 3 to 15 years, 9 years on average).
DRF on 99mTc-MAG3 study before the operation was under 40 % in 10 patients, ranging from 35 to 13 %, the remaining 38 patients had DRF above 40 %. 99mTc-MAG3 study performed 4 to 45 months post-operatively showed improvement of DRF in 11 patients (23 %), deterioration in 5 patients (10 %) and function with no significant change in 32 patients (66 %). In all 5 patients with DRF deterioration there was better flow with no obstruction after pyeloplasty despite a drop of supranormal function back to normal in 2 cases and further worsening in 3. 2 to 58 months post-operatively (24 months on average) there was a reduction in AP diameter 1 to 44mm (16mm on average) in all patients but one with no change.
Three patients developped stricture in anastomosis with the need of reoperation in 2 cases and temporary JJ stent insertion in one case. Conclusion: Performimg 99mTc-MAG3 renal scans routinely after pyeloplasty for unilateral PUJ obstruction and well-functioning contralateral kidney does not bring any clinical benefit.
USS is sufficient for the follow-up of these patients and 99mTc-MAG3 scan could be added only in patients with DRF under 40 % preoperatively. When interpreting DRF on 99mTc-MAG3 scans clinicians should bear on mind a possible supranormal function of a dilated kidney.