Purpose: The diuretic renal scan (MAG3) continues being the gold standard to test the improvement of the urinary drainage after pyeloplasty. Recent researches suggest that there are certain parameters of ultrasound (US) that may indicate an adequate urinary drainage during the follow-up. Our aim is to prove if the measurement of the anteroposterior diameter (APD) of renal pelvis by USS after the pyeloplasty may be a valid screening method to select those patients who also require a MAG3.
Methods: We retrospectively study the patients who underwent pyeloplasty between 2010 and 2019. The sample was divided in two groups depending of the increase or non-increase in the pelvic APD on postoperative US. The results of the MAG3 and the US of both groups were compared in relation to the presence or absence of obstruction and the need for repyeloplasty.
Results: We included a total of 124 pyeloplasty, with a median age of 6 months (IQR 4-36); 12 patients showed an increase in pelvic APD, of those 5 had an obstructive MAG3 and renal function >10%, requiring reoperation. Of the 112 patients in whom the pelvic APD did not increase, only one patient needed reoperation due to obstruction in the MAG3, showing the same pre and postoperative pelvic APD. The sensitivity (S) of the US was 83.33% and the specificity (E) was 94.07%.
Conclusion: A decrease of the renal pelvic APD between US before and after surgery appears to be enough to exclude those patients who will not to develop a recurrence of ureteropelvic junction obstruction (UPJO). In the rest of the patients, it would be necessary study the urinary drainage using MAG3, avoiding its inherent drawbacks in all patients undergoing pyeloplasty.
Keywords: anteroposterior diameter; pyeloplasty; renal scan; ureteropelvic junction obstruction.