Supranormal differential renal function in adults with ureteropelvic junction obstruction: Does it really exist?

Determining Split Renal Function in Children With Ureteropelvic Junction Stenosis: Technetium-99m Mercaptoacetyltriglycine (Tc-99m MAG-3) or Technetium-99m Dimercaptosuccinic Acid (Tc-99m DMSA)?

Background Ureteropelvic junction stenosis (UPJS) is the most common cause of clinically significant antenatal hydronephrosis. We compared separate renal function results obtained using technetium-99m-mercaptoacetyltriglycine (Tc-99m MAG-3) and technetium-99m-dimercaptosuccinic acid (Tc-99m DMSA) in pediatric patients with UPJS to evaluate the adequacy of Tc-99m MAG-3 scintigraphy and the necessity of additional Tc-99m DMSA scintigraphy during follow-up. Methodology Patients diagnosed with hydronephrosis in the Pediatric Nephrology Department of Pamukkale University Faculty of Medicine over a period of 10 years (2012-2022) were evaluated retrospectively. Patients who had been diagnosed with UPJS and underwent both Tc-99m MAG-3 and Tc-99m DMSA scintigraphy during follow-up were included in the study. Technetium-99m-labeled MAG-3 and DMSA scans were re-evaluated for all patients by the Department of Nuclear Medicine. Results The study included 52 children with unilateral UPJS (12 girls and 40 boys) with a mean age of 6.34 ± 4.81 years (range: 2.97-9.79 years). Thirty-six patients (69.2%) were diagnosed antenatally. Differential renal function in Tc-99m DMSA was 46.94 ± 10.64 and in Tc-99m MAG-3 was 43.08 ± 11.18; the functions were lower in Tc-99m MAG-3, but the values were within normal limits for both groups (p=0.0001, z=-3.893). When differential renal functions were compared between Tc-99m DMSA and Tc-99m MAG-3 results, a statistically significant positive and strong correlation was found in the kidney with ureteropelvic junction obstruction (UPJO) (p=0.0001, r=0.752). When classifying the Tc-99m MAG-3 and Tc-99m DMSA results in the kidney with UPJO (supranormal, normal, low function) for the determination of differential renal functions, there was a consistency of 76%, and it was correlated (p=0.0001, k=0.456). While two patients had supranormal function and 13 patients had low function in Tc-99m MAG-3, five patients had supranormal function, and eight patients had low function in Tc-99m DMSA. Conclusions Some studies in the literature have reported that Tc-99m MAG-3 causes supranormal function measurements in patients with UPJS; our results showed that Tc-99m DMSA resulted in a higher rate of supranormal values for affected kidneys. We believe that Tc-99m DMSA should not be performed in addition to Tc-99m MAG-3 scintigraphy in the follow-up of every patient with UPJS but can be utilized in select cases, such as patients with surgical indications and those suspected before surgery.

Critical analysis of pyeloplasty role in adults with late diagnosis of ureteropelvic junction obstruction-a comparative study

PURPOSE

Due to the data paucity about the functional outcomes post pyeloplasty for patients diagnosed with ureteropelvic junction obstruction (UPJO) with a preoperative age above the age of 45 years and according to the elderly definition (age ≥ 65 years), we conducted this study to clarify the different outcomes in adults presented with late hydronephrosis.

METHODS

We included patients who were managed by pyeloplasty with a preoperative age ≥ 45 years. We further subdivided those patients into; group (A) patient's age ≥ 65 years and group (B) patient's age ≥ 45 and < 65 years. Split renal function (SRF) difference was evaluated by the changes between the last follow-up and the baseline renogram, where 5% change was considered a significant change. Functional outcomes and factors predicting the functional recoverability post pyeloplasty were evaluated.

RESULTS

A total of 119 patients were included. The mean age was 62.3 ± 16.4 years. Group (A) and group (B) included 47 and 72 patients, respectively. After 24 months, GFR and SRF were increased at the last follow-up (P = 0.32 and 0.57, respectively). No significant functional changes were noted between both groups. Sixty two, 7 and 13 patients showed static, decreased and improved renal function. Lower preoperative SRF was the only predictor for poor functional recoverability in patients with age ≥ 45 years who were managed by pyeloplasty.

CONCLUSION

Elderly patients should not be excluded from the corrective surgery for UPJO. Lower preoperative SRF was the only predictor for renal function deterioration post pyeloplasty.