Correlation of renal biopsy and radionuclide renal scan differential function in patients with unilateral ureteropelvic junction obstruction

Pyeloplasty in children with low differential renal function: Functional recoverability

INTRODUCTION AND OBJECTIVE

Ureteropelvic junction obstruction (UPJO) is a common pathology in pediatric urology practice. Indications for intervention are well established while the ideal management of children with UPJO in poorly functioning kidneys is still debatable. We aimed in this study to evaluate the outcome of pyeloplasty in patients with UPJO and low DRF ≤20%.

STUDY DESIGN

We retrospectively evaluated 218 children with congenital UPJO from two tertiary hospitals between 2008 and 2018. We included only those with primary unilateral UPJO and DRF ≤20% on diuretic renography. Open dismembered pyeloplasty with stenting was carried out in all. Patients with bilateral UPJO, solitary kidney, DRF above 20%, association with other urinary anomalies and patients who underwent previous renal or ureteric surgeries and patients with missed follow-up were excluded. Clinical and radiological outcomes of this subgroup of patients were assessed.

RESULTS

A total of 21 patients (12 boys, 9 girls) with a median age at surgery of 2 years were included. Preoperative DRF ranged from 8 to 20% with a mean of 15% ± 3.5%. The median follow-up period was 2.5 years. Renal ultrasound showed improved HN in 16 patients (4 had a complete resolution) and stable in the remaining 5. Most of the improvement was noted in the first postoperative ultrasonography 16/21 (76%). Diuretic renography showed improved DRF by 10-15% in 8 patients (38%) while the remaining patients showed stable DRF with a non-obstructive curve with a mean improvement in DRF of 8 ± 5%. No postoperative complications were encountered and none of our patients required reintervention during follow-up.

DISCUSSION

The ideal management of children with UPJO and poorly functioning kidneys is still arguable. In our study we evaluated the outcome of pyeloplasty in patients with a low DRF ≤ 20% aiming to test the patients' variables that can affect the improvement of DRF and HN grade after surgical intervention, however, none of these preoperative variables seemed to be a significant predictor.

CONCLUSIONS

Children with unilateral UPJO and DRF ≤ 20% have a favorable outcome after pyeloplasty. Improvement of HN in the first postoperative renal ultrasound is a good indicator for success.

Risk Factors and Management Options for the Adult Failed Ureteropelvic Junction Obstruction Repair in the Era of Minimally Invasive and Robotic Approaches: A Comprehensive Literature Review

Guidelines for the management of pyeloplasty failure remain elusive given the rarity of this condition and the difficulty of integrating and analyzing reported outcomes given the varying definition of failures. In this article, we aim to review the existing literature on risk factors that may influence the surgical outcomes of reconstructive pyeloplasty for ureteropelvic junction obstruction. Furthermore, we discuss management options and review success outcomes of treatment options for patients with pyeloplasty failure.

Grading of Hydronephrosis: An Ongoing Challenge

The crucial point for prompt diagnostics, ideal therapeutic approach, and follow-up of hydronephrosis associated with UPJ anomalies in children is the severity of hydronephrosis. Such many hydronephrosis grading systems as AP diameter, SFU, radiology, UTD, and Onen have been developed to evaluate hydronephrosis severity in infants. Unfortunately, it is still an ongoing challenge and there is no consensus between different disciplines. AP diameter is a very dynamic parameter and is affected by many factors (hydration, bladder filling, position, respiration). More importantly, its measurement is very variable and misleading due to different renal pelvic configurations. The radiology grading system has the same grades 1, 2, and 3 as the SFU grading system with addition of the AP diameter for the first 3 grades. This grading system divides parenchymal loss into two different grades. Grade 4 represents mild parenchymal loss while grade 5 suggests severe parenchymal loss. However, it is operator dependent, is not decisive, and does not differentiate grades 4 and 5 clearly. All grades of SFU are very variable between operators and clinicians. UTD classification aims to put all significant abnormal urinary findings together including the kidney, ureter, and bladder and thus determines the risk level for infants with any urinary disease. Different renal deterioration risks occur depending on the mechanism of hydronephrosis. Therefore, SFU and UTD classification may result in significant confusion and misleading in determining the severity of hydronephrosis. SFU-4 and UTD-P3 represent a considerable range of severity of hydronephrosis. Both represent minimal thinning of the medullary parenchyma and severe thinning of the cortical parenchyma (cyst-like hydronephrotic kidneys) at the same grade. The wide definition of SFU-4 and UTD-P3 fails to indicate accurately the severity of hydronephrosis and thus significantly misleads from a prompt treatment. They do not suggest who need surgical treatment and who can safely be followed non-operatively. The anatomy and physiology of the 4 suborgans of the kidney (renal pelvis, calices, medulla, and cortex) are completely different from each other. Therefore, each part of the kidney affect and behave differently as a response to UPJ-type hydronephrosis (UPJHN) depending on the severity of hydronephrosis. The upgraded Onen hydronephrosis grading system has been developed based on this basic evidence both for prenatal and post-natal periods. The Onen grading system determines specific detailed findings of significant renal damage, which clearly show and suggest who can safely be followed conservatively from who will need surgical intervention for UPJHN. Neither AP diameter nor radiology, SFU, or UTD classification is the gold standard in determining the severity of hydronephrosis. All these grading systems are based on subjective parameters and are affected by many factors. They do not determine the exact severity of UPJHN and thus cause permanent renal damage due to a delay in surgical decision in some infants while they may cause an unnecessary surgery in others. The Onen grading system has resolved all disadvantages of other grading systems and promises a safer follow-up and a prompt treatment for UPJHN. It is an accurate and easily reproducible grading that has high sensitivity and specificity.

Is it Always Necessary to Treat an Asymptomatic Hydronephrosis Due to Ureteropelvic Junction Obstruction?

The postnatal treatment of asymptomatic unilateral hydronephrosis due to ureteropelvic junction obstruction remains controversial, and the timing of and indications for surgical intervention are continuously debated. There is no consensus on the best follow-up during expectant management. The various modalities and parameters have been discussed along with their pros and cons and an attempt has been made to clear up the controversies.

Evaluation of Renal Histopathological Changes, as a Predictor of Recoverability of Renal Function Following Pyeloplasty for Ureteropelvic Junction Obstruction

Background:

Pyeloplasty is a widely accepted treatment for ureteropelvic junction obstruction (UPJO). However, the renal function recoverability after pyeloplasty is still a matter of debate. Different parameters have been used to predict renal functional recoverability after corrective surgery, with conflicting results.

Objectives:

In this study, renal biopsy was carried on a series of cases of UPJO, during pyeloplasty, to study the extent of histological alterations in renal parenchyma, as a result of obstruction, and its predictive value in renal function recoverability after pyeloplasty.

Patients and Methods:

We retrospectively analyzed the renal biopsy obtained during pyeloplasty in 53 adult patients. Histopathological changes were graded on a scale of 1 to 3, according to their severity, and compared with the differential renal function (DRF) revealed on the preoperative and postoperative follow up diethylene triamine pentaacetic acid (DTPA) renal scan. A Fischer’s t test was used to evaluate statistical differences between values.

Results:

This study showed a linear relationship between the severity of histological changes and renal function recovery, after pyeloplasty. Out of 24 obstructed renal units (ORU), with minimal histopathological changes (grade I), 21 ORU (87.5%), with > 35% DRF preoperatively, showed significant improvement in renal function after 12 months of pyeloplasty (P < 0.05). On the other hand, all kidneys (n = 29) with moderate to severe obstructive changes (grade II and III) had minimal improvement in DRF, after pyeloplasty, which was clinically insignificant (P > 0.05). Renal function deterioration after pyeloplasty was not observed in any of the cases.

Conclusions:

The severity of pathological changes in renal parenchyma, due to UPJO, is a good predictor of renal function recoverability, after pyeloplasty. The ORUs, with DRF > 35%, usually have normal (grade I) renal biopsy and might be expected to present better functional recoverability after pyeloplasty.

Is renal biopsy a better predictor of the outcome of pyeloplasty in adult ureteropelvic junction obstruction?

OBJECTIVE

To prospectively evaluate per operative renal biopsy as a predictor of outcome of pyeloplasty in cases of unilateral pelviureteric junction obstruction in adults.

MATERIALS AND METHODS

We conducted a prospective study on 24 patients with unilateral UPJ obstruction undergoing pyeloplasty between November 2005 and August 2006 and followed them until December 2010. Intraoperative renal wedge biopsy was obtained in these patients and this was correlated with preoperative DRF on diuretic renogram. Outcome of pyeloplasty was assessed at 1 and 3 years by diuretic renograms and the renal biopsy as a predictive tool was compared with preoperative DRF.

RESULTS

Histology suggestive of obstructive damage to kidneys, such as significant glomerulosclerosis, widened Bowman's capsule, interstitial fibrosis, and tubular atrophy on renal biopsy was the highly significant predictor of poor outcome of pyeloplasty with a P value=.001 compared with preoperative DRF.

CONCLUSION

Renal biopsy is better predictor of outcome of pyeloplasty compared with preoperative DRF in UPJ obstruction. In the presence of severe obstructive changes in renal biopsy, recoverability of renal function despite achievement of successful drainage is significantly decreased.

Congenital ureteropelvic junction obstruction: human disease and animal models

Ureteropelvic junction (UPJ) obstruction is the most frequently observed cause of obstructive nephropathy in children. Neonatal and foetal animal models have been developed that mimic closely what is observed in human disease. The purpose of this review is to discuss how obstructive nephropathy alters kidney histology and function and describe the molecular mechanisms involved in the progression of the lesions, including inflammation, proliferation/apoptosis, renin-angiotensin system activation and fibrosis, based on both human and animal data. Also we propose that during obstructive nephropathy, hydrodynamic modifications are early inducers of the tubular lesions, which are potentially at the origin of the pathology. Finally, an important observation in animal models is that relief of obstruction during kidney development has important effects on renal function later in adult life. A major short-coming is the absence of data on the impact of UPJ obstruction on long-term adult renal function to elucidate whether these animal data are also valid in humans.

Mechanisms of renal injury and progression of renal disease in congenital obstructive nephropathy

Congenital obstructive nephropathy accounts for the greatest fraction of chronic kidney disease in children. Genetic and nongenetic factors responsible for the lesions are largely unidentified, and attention has been focused on minimizing obstructive renal injury and optimizing long-term outcomes. The cellular and molecular events responsible for obstructive injury to the developing kidney have been elucidated from animal models. These have revealed nephron loss through cellular phenotypic transition and cell death, leading to the formation of atubular glomeruli and tubular atrophy. Altered renal expression of growth factors and cytokines, including angiotensin, transforming growth factor-beta, and adhesion molecules, modulate cell death by apoptosis or phenotypic transition of glomerular, tubular, and vascular cells. Mediators of cellular injury include hypoxia, ischemia, and reactive oxygen species, while fibroblasts undergo myofibroblast transformation with increased deposition of extracellular matrix. Progression of the lesions involves interstitial inflammation and interstitial fibrosis, both of which impair growth of the obstructed kidney and result in compensatory growth of the contralateral kidney. The long-term outcome depends on timing and severity of the obstruction and its relief, minimizing ongoing injury, and enhancing remodeling. Advances will depend on new biomarkers to evaluate the severity of obstruction, to determine therapy, and to follow the evolution of lesions.

Chronic partial ureteral obstruction and the developing kidney

Although congenital urinary tract obstruction is a common disorder, its pathophysiology remains poorly understood and clinical practice is controversial. Animal models have been used to elucidate the mechanisms responsible for obstructive nephropathy, and the models reveal that renal growth and function are impaired in proportion to the severity and duration of obstruction. Ureteral obstruction in the neonatal rat or mouse leads to activation of the renin-angiotensin system, renal infiltration by macrophages, and tubular apoptosis. Nephrons are lost by glomerular sclerosis and the formation of atubular glomeruli, and progressive injury leads to tubular atrophy and interstitial fibrosis. Recovery following release of obstruction depends on the timing, severity, and duration of obstruction. Growth factors and cytokines are produced by the hydronephrotic kidney, including MCP-1 and TGF-beta1, which are excreted in urine and can serve as biomarkers of renal injury. Because MRI can be used to monitor renal morphology, blood flow, and filtration rate, its use might supplant current imaging modalities (ultrasonography and diuretic renography), which have significant drawbacks. Combined use of MRI and new urinary biomarkers should improve our understanding of human congenital obstructive nephropathy and should lead to new approaches to evaluation and management of this challenging group of patients.

The true clinical significance of renography in nephro-urology

Isotopic renography is a non-invasive technique used routinely by the clinician to provide information about kidney structure and function. Whilst there is no doubt of its value in the accurate measurement of glomerular filtration rate and in the detection of parenchymal abnormalities, its role in the diagnosis of renovascular disease (especially in patients with renal insufficiency), the exclusion of obstruction and the evaluation of the patient with either acute renal failure or renal transplant dysfunction remains unproven. In part, this reflects a failure to standardise protocols and rigorously evaluate diagnostic techniques. Recent developments in ultrasound, computerised X-ray tomography and nuclear magnetic resonance now present the clinician with rival techniques and emphasise the need for the clinical development of isotopic renography.