Value of supranormal function on ^99mTc‐mercaptoacetyltriglycine renal scan in paediatric patients with obstructive hydronephrosis

Abstract

Objectives To study related factors and clinical significance of supranormal function in paediatric patients with pelvi‐ureteric junction obstruction, and to predict which factors cause renal function overestimation. Patients and Methods Patients who underwent pyeloplasty from 2012 to 2017 were prospectively collected. Variables were compared between patients with and without supranormal function on 99mTc‐mercaptoacetyltriglycine renal scan (supranormal defined as differential renal function [DRF] ≥55%). Univariate, multivariate logistic and linear regressions analyses were performed. Results Of 100 patients, 18 were excluded because of comorbidities. Nine patients (11.5%) showed preoperative supranormal function. The preoperative anteroposterior pelvic diameter (APD; 24 mm vs 35 mm, P = 0.026) and the ratio between preoperative pelvic and kidney volumes (0.2 vs 0.6, P = 0.003) were higher in supranormal kidneys. For each unit increase in the preoperative ratio between pelvic and kidney volumes, the risk of supranormal function rose 3.23‐times (95% confidence interval [CI] 1.051–9.955). A preoperative APD ≥30 mm was a reliable predictor of supranormal function (area under the curve 0.804, 95% CI 0.707–0.902), with 88.9% sensitivity. Patients with either preoperative supranormal function or preoperative APD ≥30 mm had a greater reduction in renal function after pyeloplasty. Conclusion Supranormal function is related to large hydronephrosis where geometrical features are modified. A preoperative APD ≥30 mm is a reliable predictive factor of supranormal function. Preoperative renal function is overestimated either in supranormal patients or severe hydronephrotic kidneys. DRF should be interpreted with caution in kidneys with large hydronephrosis with or without supranormal function. Surgical indication should not entirely rely upon DRF.

Spectrum of Disorders Diagnosed on 99mTc-MAG3 Radioisotope Renography: A Report of 260 Saudi Arabian Patients

“…Nonetheless, it should be noted that the hydronephrotic kidney may present with a relatively higher function than the normal contralateral one, known as supernormal function phenomena; several theories have been proposed to explain such phenomena, including true compensatory hyperfunction or a technical artifact [21,22] .…”

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

“…The occurrence of a supranormal function in our present study is 3.6%, which is lower than the previous reports in pediatric age groups which ranged from 9% to 21%. [ 3 4 7 10 12 ] This lower incidence may be attributed to the late diagnosis of UPJO at adulthood which affect the renal function of the affected kidney at the first presentation. Concerning renal function outcome after pyeloplasty, it was documented that children with snDRF who underwent pyeloplasty were found to have an obvious decrease in hydronephrosis, and 70% of them had a decrease in postoperative DRF, reaching a normal level of function (40%–55%).…”

“…In a pediatric cohort, it has been shown that renal function could decrease in patients with snDRF and increased APD of the renal pelvis preoperatively when hydronephrosis improved after surgery. [ 12 ] They recommended close surveillance and early surgical treatment in those children if hydronephrosis or drainage time on renogram deteriorated. [ 12 ]…”

“…[ 12 ] They recommended close surveillance and early surgical treatment in those children if hydronephrosis or drainage time on renogram deteriorated. [ 12 ]…”

“…The nature, causes, and fate of snDRF have been studied in pediatric age groups. [ 3 4 12 ] However, this topic was rarely discussed in the adult population. Hence, we intended to evaluate functional outcomes and predictors for snDRF phenomenon occurrence in adult patients with UPJO.…”