Increased nephron volume is not a cause of supranormal renographic differential renal function in patients with ureteropelvic junction obstruction

Ureteropelvic junction obstruction with polyps in children: clinical manifestations and supranormal preoperative differential renal function

OBJECTIVE

To describe and analyze the clinical manifestation and pre-DRF of UPJO children with polyps and explore the possible influencing factors of supranormal pre-DRF.

PATIENTS AND METHODS

All patients undergoing primary Anderson-Hynes pyeloplasty for UPJO due to polyp were retrospectively reviewed. Patients' characteristics, parameters of ultrasound and dynamic renograms (DR) were recorded in elaborate. Pre-DRF in groups of different age, weight, gender, pain, grade of hydronephrosis, anterio-posterior pelvic diameter (APD), length of kidney and postoperative ultrasonic parameters were compared.

RESULTS

A total of 18 UPJO children with polyps were included. Five (27.78%) patients had SFU III grade of hydronephrosis. Seven (38.89%) patients were supranormal pre-DRF. All patients had pre-DRF > 40%. Drainage curve was delayed excretion in 12 (66.67%) patients and T1/2 < 20 min was in 4 (22.22%) patients. Among the 16 patients who underwent preoperative IVP examination, 15 (93.75%) patients had concentration of intrarenal pelvis contrast agent within 10 min. No significant difference in post-APD reduction rate and post-minPT increased was found between supranormal pre-DRF and non-supranormal pre-DRF groups. The supranormal pre-DRF was more likely to occur in young and low-weight children.

CONCLUSION

The preoperative renal function of UPJO patients with polyps was well preserved, and 38.89% of them had supranormal pre-DRF. Patients with supranormal pre-DRF can be managed with the same strategies as those with normal renal function.

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

Introduction

Some patients with ureteropelvic junction obstruction (UPJO) have supranormal differential renal function (snDRF). We aimed to study the outcomes of pyeloplasty in adult patients with UPJO and either snDRF or normal differential renal function (nDRF) and to identify preoperative factors responsible for the snDRF phenomenon.

Materials and Methods

We retrospectively retrieved data for all patients who underwent pyeloplasty and had snDRF (differential renal function [DRF] ≥55%) and nDRF (DRF between 45 and 55%) preoperatively. Preoperative radiological data using computed tomography or magnetic resonance imaging were correlated with the presence of snDRF phenomenon. In addition, scintigraphic findings pre- and post-operatively were also assessed to evaluate the functional outcomes.

Results

Of a total of 856 patients, 31 had snDRF (group 1) and 42 had nDRF (group 2). After a mean of 37 months' follow-up in Group 1, 22 patients developed DRF reduction with non-obstructive pattern. Mean DRF % decreased from 59 ± 2.8 to 48 ± 13 (P < 0.0001). However, in Group 2, five patients had DRF decrease. Four patients developed snDRF phenomenon postoperatively. Increased renal pelvis volume ≥50 mm³ and increased anteroposterior pelvic diameter (APD) ≥37 mm were found to predict snDRF phenomenon. The same findings, in addition to preoperative snDRF, correlated with postoperative DRF decrease.

Conclusion

SnDRF function could be expected in patients with increased renal pelvis volume and APD. The absolute value or changes in DRF are not reliable to judge treatment failure.

Comparative Outcome Analysis of Children Who Underwent Pyeloplasty for Ureteropelvic Junction Obstruction Associated With or Without Supranormal Differential Renal Function

OBJECTIVE

To compare pyeloplasty outcomes in children with and without "supra-normal" differential renal function (SNDRF) defined as >55% differential renal function (DRF) in children with ureteropelvic junction obstruction.

METHODS

Our prospectively collected pyeloplasty database (2008-2015) was reviewed (n = 151). A total of 140/151 (93%) patients had preoperative renograms and 26/140 (19%) were found to have SNDRF (DRF ≥ 55%). Of 151 patients, 51 (34%) had pre- and postoperative renograms allowing determination of change ≥5% in function. After excluding 2 patients with solitary kidneys, a total of 49 patients defined the study group.

RESULTS

Of 49 patients, 12 had SNDRF and 37 did not. Baseline characteristics were similar including mean age at surgery (47.3 months vs 45.4 months) and time to surgery (8.7 months vs 9.8 months). Mean preoperative anteroposterior diameter was significantly different between groups (23.2 mm vs 31.0 mm; P = .04), but postoperative was similar (9.0 mm vs 12.1 mm; P = .14). Mean preoperative DRF was 60.2% in the SNDRF group vs 44.3% in the non-SNDRF. Mean postoperative DRF was 52.4% and 45.3%, respectively (P = .04). There were 9/12 (75%) SNDRF patients who experienced ≥5% loss in function compared to 2/37 (5%) in the non-SNDRF group (P < .01).

CONCLUSION

Three-quarters of SNDRF patients demonstrated a decline of ≥5%DRF postoperatively when compared to non-SNDRF. This finding may not reflect true elevated renal function, but rather hyperfiltration in the setting of obstruction, which-if unrecognized as such-could result in postponing an otherwise beneficial surgical intervention.

The prognostic value of relative renal function greater than 51% in the pelvi-ureteric junction-obstructed kidney on 99mtechnetium mercaptoacetyltriglycine study

OBJECTIVE

Obstructed kidneys with relative function (RRF) estimates >50% are occasionally noted in (99m)technetium mercaptoacetyltriglycine renal studies. It is thought that increased RRF might confer some benefit and/or permit delayed intervention. We compared the RRF and absolute renal function, as defined by effective renal plasma flow (ERPF), of obstructed kidneys in the ranges >51%, 40%-50% and <40% RRF before and after pyeloplasty.

METHODS

Twenty children, median age 13.5 months (range 3 weeks-126 months), satisfied criteria for the diagnosis of PUJ obstruction and estimated function >51% (group 1). Their pre- and post-intervention data were compared with 21 children, median age 2 months (range 1 week-126 months), with PUJ obstruction and 40%-50% RRF (group 2); and 21, median age 6 months (range two days-110 months), with RRF below 40% (group 3). Kidneys showing signs of continuing obstruction after surgery were excluded.

RESULTS

Final ERPF was negatively related to age: younger children, and those with a higher preoperative ERPF, recovered better than older children and those with a lower ERPF (p<0.05). Pre- and postoperative mean ERPF in group 1 was 76 (range 21-203) and 102 (6-240) ml/min/1.73 msq respectively. In group 2, these values were 75.2 (30-187) and 130.9 (44-306) ml/min/1.73 msq, and they were 42.6 (5-179) and 80.2 (17-205) ml/min/1.73 msq in group 3. When adjustment was made for preoperative ERPF, there was no evidence that RRF grouping was related to ERPF outcome. The postoperative ERPF of seven of 20 kidneys from group 1 (>51%) was lower than the ERPF before surgery compared to 2/21 in group 2 and 4/21 in group 3, but these differences were not statistically significant (p=0.25).

CONCLUSIONS

Most kidneys in each functional range improved when obstruction was relieved. An RRF >51% in the obstructed kidney was not always prognostically beneficial, and may be a warning of impending decompensation in a minority.

The change in renal function in the supranormal hydronephrotic kidney after pyeloplasty

OBJECTIVE

To investigate changes in the differential renal function (DRF) before and after pyeloplasty in renal units with unilateral pelvi-ureteric junction obstruction (PUJO) with supranormal function, and to evaluate the clinical significance.

PATIENTS AND METHODS

We reviewed the medical and radiographic records of 29 children (26 boys and three girls) with unilateral PUJO with a DRF (estimated by (99m)Tc-mercaptoacetyltriglycine renal scintigraphy) of >/= 50% in the affected renal unit, who had pyeloplasty and were followed for >1 year after surgery. Patients were divided into two groups according to the degree of change in their DRF to compare the clinical variables, anteroposterior pelvic diameter and parenchymal thickness measured by renal ultrasonography. The mean (range) follow-up after pyeloplasty was 35 (12-89) months.

RESULTS

After pyeloplasty, although the mean DRF reduced from 53.8% to 51.4%, in seven (24%) patients the DRF decreased significantly (>5%) while most (76%) showed a change of </= 5% of the preoperative function, or further improvement. In the seven patients with a DRF of >/= 55% before surgery, the DRF afterward was >55% in four and 50-55% in one. Between those with and with no significant reduction in DRF, only the preoperative renal parenchymal thickness differed significantly (2.78 vs 5.00 mm, P = 0.006).

CONCLUSION

Supranormal DRF exists and represents the true split function of the affected renal unit in patients with adequate renal parenchyma; these units maintained the supranormal function after pyeloplasty. Parenchymal thickness might be useful to differentiate between the true and false estimates and predict surgical outcome before surgery.