Analysis of the Efficacy of Elastography in Comparison with Dynamic Renal Nuclear Scintigraphy in the Evaluation of Unilateral Pelvi-Ureteric Junction Obstruction

INTRODUCTION

In hydronephrosis due to pelviureteric junction obstruction (PUJO), an obstruction to urine flow may lead to increased pelvic pressure, which may cause interstitial fibrosis and renal impairment. Recently, there have been reports on renal pelvic assessment using ultrasound elastography (USE). This study was conducted to see if USE can evaluate PUJO and if it can be correlated to the findings of the dynamic renal nuclear scan.

MATERIAL AND METHODS

In this observational study, only patients with unilateral PUJO underwent acoustic radiation force impulse (ARFI) elastography. A rectangular region of interest (ROI) measuring 5 × 10 mm was positioned on the cortex region of the upper, mid, and lower poles of the affected kidney. Three valid measurements were obtained, from which a mean value was calculated. A dynamic renal nuclear scan using Technetium-99m ethylene dicysteine (EC or TC99 m EC) was obtained and split renal function (SRF) was used for comparison.

RESULTS

In the group of 20 patients, the mean age was 3.37 years. The mean SRF of the affected kidney was 26.65 %, and the corresponding USE value was 0.45 kpa. The Spearman's rho correlation coefficient for SRF and USE was 1 and 0.672, respectively (p = 0.001). Elastography was not feasible if SRF was less than 20 %.

CONCLUSION

USE may be able to comment on the renal functional status of hydronephrosis. If USE is reported as non-feasible, it may suggest that renal function is grossly compromised. It may serve as an alternative diagnostic modality for renal functional evaluation.

LEVEL OF EVIDENCE

Level II, Prospective Cohort Study.

Predicting new-baseline glomerular filtration rate (NBGFR) after donor nephrectomy: validation of a split renal function (SRF)-based formula

BACKGROUND

Accurate prediction of post-donor nephrectomy (DN) glomerular filtration rate is potentially useful for evaluating and counselling living kidney donors. Currently, there are limited tools to evaluate post-operative new-baseline glomerular filtration rate (NBGFR) in kidney donors. We aim to validate a conceptually simple formula based on split renal function (SRF) previously developed for radical nephrectomy patients.

METHODS

Eighty-three consecutive patients who underwent DN from 2010 to 2016 were included. Pre-operative CT imaging and functional data including pre-DN baseline Global GFR (108.2 ± 13.2 mL/min/1.73m2) were included. Observed NBGFR was defined as the latest eGFR 3-12 months post-DN. SRF, defined as volume of the contralateral non-resected kidney normalised by total volume of kidneys, was determined from pre-operative cross-sectional imaging (49.2 ± 2.36%). The equation derived from Rathi et al. is as detailed: Predicted NBGFR = 1.24 × (Global GFR Pre-DN) x (SRF).

RESULTS

The relationship between predicted NBGFR (66.0 ± 8.29 mL/min/1.73m2) and observed NBGFR (74.9 ± 16.4 mL/min/1.73m2) was assessed by evaluating correlation coefficients, bias, precision, accuracy, and concordance. The new SRF-based formula for NBGFR prediction correlated strongly with observed post-operative NBGFR (Pearson's r = 0.729) demonstrating minimal bias (median difference = 7.190 mL/min/1.73m2) with good accuracy (96.4% within ± 30%, 62.7% within ± 15%) and precision (IQR of bias =  - 0.094 to 16.227).

CONCLUSION

The SRF-based formula was also able to accurately discriminate all but one patient to an NBGFR of > 45 mL/min/1.73m2. We utilised the newly developed SRF-based formula for predicting NBGFR in a living kidney donor population. Counselling of donor post-operative renal outcomes may then be optimised pre-operatively.

Computed Tomography Renal Volumetry Better Predicts Postoperative Donor Renal Function in Live Kidney Donor Transplantation than Renal Scintigraphy: A Comparative Study

INTRODUCTION AND OBJECTIVES

Both computed tomography (CT) and renal scintigraphy (RS) have been used to assess vascular anatomy, renal status, and split renal function (SRF). In this study, we used a recently developed software that facilitates renal volumetric evaluations to compare RS and automated CT volumetry for assessing residual renal function and, thus, estimating postoperative renal function after donor nephrectomy.

METHODS

Fifty-one cases of donor nephrectomy were analyzed. Residual renal function was estimated based on RS and CT volumetry. The correlation between the postoperative estimated glomerular filtration rate (eGFR) and expected SRF, measured using RS and three types of CT volumetry data (ellipsoid, thin-slice, and 5-mm slice data), was determined.

RESULTS

The correlation coefficient between actual eGFR and expected SRF was significantly associated at each time point and modality (p < 0.0001). At any time point, the difference in correlation coefficient between RS and 5-mm volumetry was significant (p value: 0.003-0.018), whereas the differences in correlation coefficients between RS and the triaxial volume calculation, and the triaxial volume calculation and 5-mm volumetry, were generally statistically insignificant.

CONCLUSIONS

Expected SRF was estimated more accurately by CT volumetric calculations (especially 5-mm slice-based volumetry) than RS.

CT volumetry performs better than nuclear renography in predicting estimated renal function one year after living donation

The evaluation of split renal function (SRF) is a critical issue in living kidney donations and can be evaluated using nuclear renography (NR) or computerized tomography (CT), with unclear comparative advantages. We conducted this retrospective study in 193 donors to examine the correlation of SRF assessed by NR and CT volumetry and compared their ability to predict remaining donor renal function at 1 year, through multiple approaches. A weak correlation between imaging techniques for evaluating the percentage of the remaining kidney volume was found in the global cohort, with an R² = 0.15. However, the Bland-Altman plot showed an acceptable agreement (95% of the difference between techniques falling within - 8.51 to 6.11%). The predicted and observed eGFR one year after donation were calculated using the CKD-EPI, and CG/BSA equations. CT volume showed a better correlation than NR for both formulas (adjusted R² of 0.42. and 0.61 vs 0.37 and 0.61 for CKD-EPI and CG/ BSA equations, respectively). In non-nested modeling tests, CT volumetry was significantly superior to NR for both equations. CT volumetry performed better than NR in predicting the estimated renal function of living donors at 1-year, independently from the eGFR equation.

Renal function damage in children with duplex kidneys

PURPOSE

To evaluate renal function damage in children with duplex kidneys.

METHODS

A total of 355 duplex kidneys, 110 urinary tract infection (UTI) kidneys without abnormalities, and 104 kidneys with primary unilateral vesicoureteral reflux (VUR) were reviewed. Clinical data including age at diagnosis, body weight, history of UTI, ureteroceles, ectopic ureteral opening, VUR grade, serum creatinine level, cystatin C level, renal scarring, split renal function in dimercaptosuccinic acid scans, and effective renal plasma flow (ERPF) were analyzed.

RESULTS

Duplex kidneys had a higher grade of VUR and renal scarring. Split renal function in unilateral duplex kidneys (45.58 ± 12.85%) was much lower than that in contralateral duplex kidneys (56.33 ± 11.90%) and controls (50.00 ± 11.38%) (P < 0.001 and P = 0.014, respectively). Both left and right split renal functions in bilateral duplex kidneys were similar to those ipsilateral to the controls (P = 0.906 and P = 0.932, respectively). However, the total ERPFs in the left, right, and bilateral duplex kidneys were significantly lower than that in the control group (P = 0.003, P = 0.001, and P = 0.003, respectively). The total ERPFs in the left and right unilateral duplex kidneys were similar. ERPF in unilateral duplex kidneys (106.70 ± 48.05 mL/min/m²) was significantly lower than that in contralateral duplex kidneys (150.18 ± 49.01 mL/min/m²) or those ipsilateral to controls (145.98 ± 41.16 mL/min/m²) (P < 0.001 and P < 0.001, respectively).

CONCLUSION

Duplex kidneys are usually accompanied by a higher grade of VUR, more severe renal scarring, and renal function impairment. Split renal function in duplex kidneys often declines significantly. Notably, the evaluation of split renal function in bilateral duplex kidneys should be performed cautiously.

Whole ureter replacement with Yang-Monti principle: successful treatment of challenging conditions

BACKGROUND

No clear consensus has been reached on the reconstruction of long-segment or total ureter discontinuation. Here we present our experience using the Yang-Monti technique in total ureter reconstruction.

METHODS

This study was a single-center retrospective study of patients who underwent Yang-Monti ileal whole ureter reconstruction (from the ureteropelvic junction[UPJ] to the ureterovesical junction). Data were collected on patients' baseline characteristics, stricture etiology, the time interval between insult and surgical repair, pre/postoperative serum creatinine, estimated glomerular filtration rate (eGFR), split renal function, complications during admission and follow-ups, and the indwelling durations of JJ tubes and nephrostomy tubes, if presented.

RESULTS

Seven patients underwent Yang-Monti ileal ureter reconstruction in 2010-2020 at our hospital. One of the patients underwent single-session bilateral ureter repair. Radiation therapy-related fibrosis and degloving injury were the most common etiologies for ureter injury. The median interval between ureter insult and operation was 8 months. The median follow-up was 36.7 months. The average operation time was 11.4 h, and the average blood loss was 273 ml. Postoperatively, no significant differences were found in serum creatinine, eGFR, or split renal function. As for postoperative complications, two patients experienced ileus and were treated conservatively. One patient had UPJ stenosis, which resolved after re-anastomosis surgery 11 months later. Metabolic acidosis or electrolyte imbalance was not reported.

CONCLUSION

We found that ileal replacement of total ureteral loss using the Yang-Monti principle is effective and durable. This is the largest cohort study conducted with more than 2 years of follow-up.

Comparison of surgical outcomes and split renal function between laparoscopic and robot-assisted partial nephrectomy: a propensity score-matched analysis

PURPOSE

The objective of this study was to compare perioperative outcomes and total and split renal function between laparoscopic partial nephrectomy (LPN) and robot-assisted partial nephrectomy (RAPN). Predictive risk factors of preservation of operated renal function were also assessed.

METHODS

We retrospectively analyzed 173 patients who underwent LPN (n = 84) or RAPN (n = 89) between 2010 and 2020. After propensity score matching (1:1), perioperative outcomes and total and split renal function were assessed. Logistic regression analysis was used to evaluate predictive risk factors of preservation of operated renal function. Trifecta criteria were defined as negative surgical margins, warm ischemia time (WIT) < 25 min, and no complications more than Clavien-Dindo grade II within 4 weeks after surgery. Split renal function was evaluated by mercaptoacetyltriglycine renal scan.

RESULTS

After propensity score matching, 42 patients were allocated to each group. RAPN was associated with significantly shorter WIT (RAPN vs LPN: 12 vs 22 min; p < 0.0001) and higher trifecta achievement rate (93.3 vs 64.2%; p < 0.0001). Other perioperative outcomes and total and split renal function were not significantly different between LPN and RAPN. The R.E.N.A.L. nephrometry score (RNS) was a predictive risk factor of preservation of operated renal function in the multivariable logistic regression analysis (odds ratio 1.68, 95% confidence interval 1.29-2.20, p < 0.0001).

CONCLUSIONS

RAPN improved WIT and trifecta achievement rate, but it did not improve the preservation of operated renal function, for which RNS was found to be a strong predictive risk factor.

Predicting GFR after radical nephrectomy: the importance of split renal function

PURPOSE

To evaluate a conceptually simple model to predict new-baseline-glomerular-filtration-rate (NBGFR) after radical nephrectomy (RN) based on split-renal-function (SRF) and renal-functional-compensation (RFC), and to compare its predictive accuracy against a validated non-SRF-based model. RN should only be considered when the tumor has increased oncologic potential and/or when there is concern about perioperative morbidity with PN due to increased tumor complexity. In these circumstances, accurate prediction of NBGFR after RN can be important, with a threshold NBGFR > 45 ml/min/1.73m² correlating with improved overall survival.

METHODS

236 RCC patients who underwent RN (2010-2012) with preoperative imaging (CT/MRI) and relevant functional data were included. NBGFR was defined as GFR 3-12 months post-RN. SRF was determined using semi-automated software that provides differential parenchymal-volume-analysis (PVA) from preoperative imaging. Our SRF-based model was: Predicted NBGFR = 1.24 (× Global GFR_Pre-RN) (× SRF_{Contralateral}), with 1.24 representing the mean RFC estimate from independent analyses. A non-SRF-based model was also assessed: Predicted NBGFR = 17 + preoperative GFR (× 0.65)-age (× 0.25) + 3 (if tumor > 7 cm)-2 (if diabetes). Alignment between predicted/observed NBGFR was assessed by comparing correlation coefficients and area-under-the-curve (AUC) analyses.

RESULTS

The correlation-coefficients (r) were 0.87/0.72 for SRF-based/non-SRF-based models, respectively (p = 0.005). For prediction of NBGFR > 45 ml/min/1.73m², the SRF-based/non-SRF-based models provided AUC of 0.94/0.87, respectively (p = 0.044).

CONCLUSION

Previous non-SRF-based models to predict NBGFR post-RN are complex and omit two important parameters: SRF and RFC. Our proposed model prioritizes these parameters and provides a conceptually simple, accurate, and clinically implementable approach to predict NBGFR post-RN. SRF can be easily obtained using PVA software that is affordable, readily available (FUJIFILM-Medical-Systems), and more accurate than nuclear-renal-scans. The SRF-based model demonstrates greater predictive-accuracy than a non-SRF-based model, including the clinically-important predictive-threshold of NBGFR > 45 ml/min/1.73m².

Contrast-enhanced MRI for simultaneous evaluation of renal morphology and split renal function in living kidney donor candidates

PURPOSE

The evaluation process of potential living kidney donors focusses on renal anatomy and split renal function. This study aimed to evaluate a magnetic resonance imaging (MRI)-based approach for simultaneous evaluation of both and its impact on clinical decision making.

METHOD

Over a 3-year period, 65 potential living kidney donors were consecutively enrolled. The MRI protocol was extended by MR-nephrography to measure split renal function. Standard DTPA-scintigraphy was used for functional comparison.

RESULTS

Split renal function showed no systematic bias between the two methods (mean difference 0.3%, p = 0.08). Both methods would have yielded the same clinical decision for donor nephrectomy in 75% of the patients. In 25 % of the patients, one method indicated a relevant side difference while the other did not, and a different clinical decision could have been made based on split renal function alone.

CONCLUSIONS

MRI proved eligible for comprehensive living kidney donor evaluation and non-inferior to scintigraphy for determining split renal function. In clinical decision making, these two methods would have resulted in the same side for donor nephrectomy in a large proportion of potential donors. Whether MRN will be implemented in clinical practice depends on transplant centre infrastructure and policy.

Potential of Perfusion Magnetic Resonance Imaging to Predict Residual Renal Function after Radical Nephroureterectomy

INTRODUCTION

The diffusion-weighted imaging (DWI) technique with intravoxel incoherent motion model enables the estimation of capillary blood volume as a perfusion-related parameter- (PP-) value. Therefore, the PP-value of the kidney theoretically reflects renal capillary blood volume. We analyzed the usefulness of the PP-value in estimating postoperative renal function in upper-tract urothelial carcinoma (UTUC) patients.

METHODS

Forty-eight consecutive patients who underwent magnetic resonance imaging before radical nephroureterectomy from 2011 to 2018 were analyzed. A PP-map displaying PP-values on a pixel-by-pixel basis was created from DWI signals (b-values of 0, 500, and 1,000 s/mm2). Two readers independently analyzed the renal PP-value. DWI-based split renal function (SRF) of the intact kidney was calculated by splitting serum Cr-based preoperative estimated glomerular filtration rates (eGFRs). The predictive accuracy of the method was evaluated using renography as the reference standard.

RESULTS

Interobserver analysis revealed an excellent correlation value of 0.97. The SRF value showed a good linear correlation with the observed postoperative eGFR (r = 0.76, p < 0.001). The predictive accuracy of the DWI-based method was similar to that of the nuclear-based method.

CONCLUSION

This DWI-based evaluation of capillary blood volume provides a noninvasive tool for predicting the postoperative renal function, thereby facilitating the management of UTUC patients.

Determination of split renal function by PSMA imaging: comparison of 68Ga-PSMA-11 PET with 99mTc-MAG3 scintigraphy

MAG3 scintigraphy with determination of split renal function (SRF) is a standard procedure in patients with metastasized castration-resistant prostate carcinoma (mCRPC) undergoing PSMA radioligand therapy (PSMA-RLT). These patients also receive frequent PSMA PET/CT scans for staging and follow up. PSMA is not only overexpressed in prostate cancer epithelial cells, but also physiologically overexpressed in the proximal tubular cells of the kidney. This study investigates the utility of PSMA-targeted imaging for determination of relative renal function. mCRPC patients (n = 97) having received ⁶⁸Ga-PSMA-11 PET/CT and ^99mTc-MAG3 scintigraphy in close temporal relationship were included in this retrospective study. PSMA-PET-derived SRF was calculated according to the bilateral renal PSMA content (total kidney PSMA = SUVmean × volume), MAG3-based SRF (SRF_MAG3) using the common standard integral method of the renal secretion phase. The agreement of SRF_PSMA and SRF_MAG3 was statistically tested using Pearson correlation and Bland-Altman analysis. The correlation between both SRF assessment methods was highly significant (P < 0.001) with r=0.91. Bland-Altman analysis confirmed agreement of the measurements. High correlation and agreement were also observed in the subgroup analyses of patients with normal and reduced renal function (r=0.81, P < 0.001 and r=0.98, P < 0.001). Renal tubular PSMA expression allows assessment of split renal function by ⁶⁸Ga-PSMA-11 PET/CT imaging. Additional MAG3 scintigraphy for the purpose of quantifying relative renal function contribution may be spared in settings where PSMA PET is performed; this insight could save time and unnecessary examinations.

Feasibility of gamma camera-based GFR measurement using renal depth evaluated by lateral scan of 99mTc-DTPA renography

OBJECTIVE

Gamma camera-based measurement of glomerular filtration rate (GFR) with ^99mTc-diethylenetriaminepentaacetic acid (DTPA) is an established non-invasive measurement of split renal function; however, it is not as accurate as the plasma sample method. Therefore, study into improving the accuracy of such method is clinically relevant. The aim of this study was to elucidate the feasibility of gamma camera-based GFR measurement using renal depth evaluated by lateral scan of ^99mTc-DTPA renography and comparing the results with those of GFR using renal depth measured by CT, and three representative formulas.

METHODS

The study population comprised 38 patients (median, 69 years; male 28, female 10; median estimated GFR, 67.4 ml/min) with renourinary disorders. Scintigraphy was performed after intravenous injection of 370 MBq ^99mTc-DTPA by dynamic data acquisition for 20 min, followed by a bilateral static scan of the abdomen for 3 min. All patients underwent computed tomography (CT) within 2 months from renography. GFR was calculated by renography using renal depth determined in five ways; lateral scan of ^99mTc-DTPA, CT, and three formulas previously created with using weight, height and age. GFRs were compared with estimated GFR (eGFR). The depth of both kidneys measured as described above was compared and evaluated the laterality of the renal depth.

RESULTS

The median values of GFR calculated with renal depth determined by ^99mTc-DTPA renography, CT, and the three formulas were 87.3, 83.9, 67.8, 68.3, and 71.5 ml/min, respectively. All of them correlated significantly with eGFR (r = 0.734, r = 0.687, r = 0.728, r = 0.726, and r = 0.686, respectively), however, no significant difference was observed among five correlation coefficients. Bland-Altman plot revealed that eGFR had error and fixed bias when compared with GFRs calculated using renal depth determined by renography, CT, and Taylor's formula. The depth of both kidneys measured by ^99mTc-DTPA renography was equivalent to that measured by CT, however, those measured by the three formulas were significantly smaller than that measured by ^99mTc-DTPA renography. The depth of the right kidney was larger than that of the left kidney using all three formulas in all patients. However, CT detected only 66% of patients to have a deeper right kidney than left kidney.

CONCLUSION

Lateral scanning is a feasible procedure to measure renal depth for accurate and reasonable split GFR measurements using ^99mTc-DTPA renography.

Estimation of split renal function using different volumetric methods: inter- and intraindividual comparison between MRI and CT

PURPOSE

This study aims to determine whether contrast-enhanced (CE)-magnetic resonance imaging (MRI) is comparable to CE-computed tomography (CT) for estimation of split renal function (SRF). For this purpose, two different kidney volumetry methods, the renal cortex volumetry (RCV) and modified ellipsoid volume (MELV), are compared for both acquisition types (CT vs. MRI) with regard to accuracy and reliability, subsequently referred to as RCV_CT/RCV_MRI and MELV_CT/MELV_MRI.

METHODS

This retrospective study included 29 patients (18 men and 11 women; mean age 62.8 ± 12.4 years) who underwent CE-MRI and CE-CT of the abdomen within a period of 3 months. Two independent readers (R1/R2) performed RCV and MELV in all datasets with corresponding semiautomated software tools. RCV was performed with datasets in the arterial phase and MELV in the venous phase. Statistics were calculated using one-way ANOVA, two-tailed Student's t test, Pearson´s correlation, and Bland-Altman plots with p ≤ 0.05 being considered statistically significant.

RESULTS

In all datasets, SRF was almost identical for both volumetry methods with a mean difference of < 1%. Bland-Altman analysis comparing RCV in CT and MRI showed very good agreement for R1/R2. Interreader agreement was strong for RCV_CT and good for RCV_MRI (r = 0.89; r = 0.69). MELV_CT/MRI interreader agreement was only moderate (r = 0.54; r = 0.50) with a high range of values. Intrareader agreement was excellent for all measurements, except MELV_MRI which showed a high mean bias and range of values (RCV_CT: r = 0.93, RCV_MRI: r = 0.98, MELV_CT: r = 0.89, MELV_MRI: r = 0.54).

CONCLUSION

Renal volumetric estimates of SRF are almost as accurate and reliable with CE-MRI as with CE-CT using RCV method. In distinction, the calculation of SRF using MELV was inferior to RCV with respect to accuracy and reliability. Thus, RCV method is recommended to estimate SRF, primarily using CT datasets. However, RCV with MRI datasets for kidney volumetry allows for comparable accuracy and reliability while sparing patients and healthy donors of unnecessary radiation exposure.

Evaluation of Split Renal Function for Children with Kidney Diseases by Renal and Vascular Color Ultrasonography

Renal dynamic imaging and radionuclide renography use radioactivity to evaluate split renal function. We aimed to investigate the use of renal vascular color Doppler ultrasonography for evaluation of split renal function in children. Thirty-five children with unilateral kidney diseases were enrolled. For patients with unilateral renal tumor, peak systolic velocity (V_max = 113.04 ± 13.59 cm/s) and resistance index (RI = 0.73 ± 0.02) were higher on abnormal compared with normal sides (V_max = 86.03 ± 6.49 cm/s, RI = 0.62 ± 0.01), and blood perfusion was good, indicating compensatory enhancement in split renal function. For unilateral renal cyst, V_max (58.20 ± 7.38 cm/s) was lower on the abnormal compared with the normal (87.71 ± 14.83 cm/s) size, and perfusion was poor. For unilateral hydronephrosis and renal atrophy, the parameters were similar to those of renal cyst, suggesting a weakening of renal function. For unilateral renal agenesis, V_max (106.07 ± 13.07 cm/s) and RI (0.71 ± 0.05) were higher, and perfusion was good. Renal vascular color Doppler ultrasonography was superior in the evaluation of split renal function in children, without being invasive or radioactive.

Influence of CT-based depth correction of renal scintigraphy in evaluation of living kidney donors on side selection and postoperative renal function: is it necessary to know the relative renal function?

PURPOSE

To analyse the influence of CT-based depth correction in the assessment of split renal function in potential living kidney donors.

METHODS

In 116 consecutive living kidney donors preoperative split renal function was assessed using the CT-based depth correction. Influence on donor side selection and postoperative renal function of the living kidney donors were analyzed. Linear regression analysis was performed to identify predictors of postoperative renal function.

RESULTS

A left versus right kidney depth variation of more than 1 cm was found in 40/114 donors (35%). 11 patients (10%) had a difference of more than 5% in relative renal function after depth correction. Kidney depth variation and changes in relative renal function after depth correction would have had influence on side selection in 30 of 114 living kidney donors. CT depth correction did not improve the predictability of postoperative renal function of the living kidney donor. In general, it was not possible to predict the postoperative renal function from preoperative total and relative renal function. In multivariate linear regression analysis, age and BMI were identified as most important predictors for postoperative renal function of the living kidney donors.

CONCLUSIONS

Our results clearly indicate that concerning the postoperative renal function of living kidney donors, the relative renal function of the donated kidney seems to be less important than other factors. A multimodal assessment with consideration of all available results including kidney size, location of the kidney and split renal function remains necessary.

Determination of single-kidney glomerular filtration rate (GFR) with CT urography versus renal dynamic imaging Gates method

OBJECTIVES

To present a single-kidney CT-GFR measurement and compare it with the renal dynamic imaging Gates-GFR.

MATERIALS AND METHODS

Thirty-six patients with hydronephrosis referred for CT urography and 99mTc-DTPA renal dynamic imaging were prospectively included. Informed consent was obtained from all patients. The CT urography protocol included non-contrast, nephrographic, and excretory phase imaging. The total CT-GFR was calculated by dividing the CT number increments of the total urinary system between the nephrographic and excretory phase by the products of iodine concentration in the aorta and the elapsed time, then multiplied by (1- Haematocrit). The total CT-GFR was then split into single-kidney CT-GFR by a left and right kidney proportionality factor. The results were compared with single-kidney Gates-GFR by using paired t-test, correlation analysis, and Bland-Altman plots.

RESULTS

Paired difference between single-kidney CT-GFR (45.02 ± 13.91) and single-kidney Gates-GFR (51.21 ± 14.76) was 6.19 ± 5.63 ml/min, p<0.001, demonstrating 12.1% systematic underestimation with ±11.03 ml/min (±21.5%) measurement deviation. A good correlation was revealed between both measurements (r=0.87, p<0.001).

CONCLUSION

The proposed single-kidney CT-GFR correlates and agrees well with the reference standard despite a systematic underestimation, therefore it could be a one-stop-shop for evaluating urinary tract morphology and split renal function.

KEY POINTS

• A new CT method can assess split renal function • Only using images from CT urography and the value of haematocrit • A one-stop-shop CT technique without additional radiation dose.

Functional outcomes of early versus delayed pyeloplasty in prenatally diagnosed pelvi-ureteric junction obstruction

Although initial conservative management is popular in the management of antenatally detected pelvi ureteric junction (PUJ) obstruction [1-3], several authors [4,5] have questioned this approach and expressed concern about failure to recover the function lost during expectant management following surgery. In this single center prospective study, we have compared the functional outcomes following early versus delayed pyeloplasty in SFU grade 3-4 PUJ obstruction.

METHODS

Among those children, who presented between 2004 and 2013, with prenatal diagnoses of unilateral PUJ obstruction (n = 886), those with SFU grade 1 or 2 hydronephrosis on USG (n = 533) were excluded. In the remaining 353 children with SFU grade 3 and 4 hydronephrosis, 243 had obstructive pattern on radionuclide scan. After excluding those with severely impaired or supranormal split renal function (SRF), palpable mass, single kidney status, bilateral disease and associated other urological anomalies a total of 126 children were included in the study group. Parents who were unwilling for a frequent follow-up underwent early pyeloplasty, (Group I: n = 62) while the remaining underwent initial conservative management, with 3 monthly USG and nuclear scans (Group II; n = 64). In this group pyeloplasty was performed whenever there was deterioration in SRF >10%, or urine infection or pain during the follow-up. A standard open dismembered pyeloplasty was performed by the same surgeon in all patients. Radionuclide scan was performed at 1 year, at the same center using the same protocol, to assess final SRF and drainage. The functional outcomes were compared using student's t test and chi square test.

RESULTS

Group I comprised of 62 patients while Group II 64 patients. The mean age at pyeloplasty was 2.8 months in group I while 12.5 months in group II. There was no significant difference in the initial antero posterior diameter (APD) between the groups; 30.2 (±3.2) mm in group I and 29.6 (±3.7) mm in group II. At 1-year follow up after surgery, there was improvement in the APD, 16.8 (±4.2) mm in group I and 18.2 (±4.5) mm in group II, with no significant difference between them. In group I, the initial mean SRF was 34.1% (±6.4) and there was significant improvement (p = 0.01) in mean SRF to 37.2 (±7.1) at 1-year follow up after surgery. In group II, the mean SRF was 35.9 (5.7) initially and there was a deterioration to 32.6 (±5.5) before surgery (Figure). At 1-year follow up after surgery, there was a marginal improvement to 33.5 (5.6), however it was significantly lower compared to the initial SRF (p = 0.01). Compared to initial function, at 1-year follow up after pyeloplasty, SRF improved in significantly higher number of patients; 17/62 (27.4%) in group I while only 7/64 (10.9%) in group II (p = 0.03) (Table). There was significantly fewer patients with deterioration in final SRF at 8/62 (12.9%) in group I compared to 22/64 (34.4%) in group II (p = 0.03).

DISCUSSION

Although several publications [1-3] have reported functional recovery during initial conservative treatment of PUJ obstruction, in our study a large proportion of patients (80%) in Group II had loss of function during follow-up. This is probably because the study population included only SFU grade 3-4 with obstructive renogram. Several authors have expressed concern about irreversible loss of renal function during expectant management [4,5]. Findings of our study reveal that irrespective of initial SRF, early pyeloplasty in prenatally diagnosed SFU grade 3-4 PUJ obstruction leads to significant improvement of SRF, while delayed pyeloplasty leads to a marginal but, significant loss. This fact should be highlighted to parents so that informed decisions can be made regarding early versus delayed surgery.

Value of diagnosis imaging in the evaluation of the severity of histological lesions in duplex systems

OBJECTIVE

In order to determine the effectiveness of imagery in the assessment of the severity of histological lesions in duplex systems in children we compared histology results from heminephrectomies with diagnosis imaging findings [renal ultrasound (US), scintigraphy, unenhanced and contrast-enhanced magnetic resonance imagery (MRI)].

MATERIALS AND METHODS

Between 2007 and 2013, 34 children with duplex system underwent surgery. The results from US (n = 34), dimer captosuccinic acid scintigraphy (n = 23) and MRI (n = 16) were compared with histological data. Five histological lesions were found (chronic interstitial inflammation, interstitial fibrosis, tubular atrophy, glomerulosclerosis and dysplasia) and categorized as severe (>25%) or moderate (≤ 25%).

RESULTS

Severe histological lesions were found in 76.5% and moderate lesions in 23.5%. Radiological features were compared with histological results. In US, severe parenchymal thinning was associated with chronic interstitial inflammatory. The absence of parenchymal enhancement and/or severe cortical thinning in MR urography (MRU) was significantly associated with interstitial fibrosis. All poorly functioning poles were associated with severe histological lesions (p = 0.091), but not to a specific category of lesions.

CONCLUSIONS

MRI sensibility was excellent (90%) in the diagnosis of poorly functioning pole. Severe thinning on US and minimal pole function on MRU can be used to predict the severity of histological lesions.

Renal ultrasound volume in children with primary vesicoureteral reflux allows functional assessment

OBJECTIVE

Renal scintigraphy represents the current diagnostic standard to assess split kidney function. We tested the hypothesis that the relative renal volume assessed by ultrasound provides an equally reliable but less invasive tool for assessment of kidney function as compared to renal scintigraphy in patients with primary vesicoureteral reflux.

METHODS

Renal ultrasound and renal scintigraphy were performed in 85 patients (median age 4.5 years, range 0.25-7.7) and repeated in 74 patients after 2-13 months (mean 7) of the primary investigation. Renal size was measured by ultrasound, and relative renal volume was calculated for each kidney by using the formula of a prolate ellipsoid. Renal function was estimated for each side (split renal function) by scintigraphy with (99m)Tc MAG3.

RESULTS

The mean difference between relative renal volume measured by ultrasound and split renal function determined by renal scintigraphy was 2.8% (standard deviation ± 4.1%; 95% confidence interval 10.8/-5.2%). There was a statistically significant correlation between relative renal volume estimated by ultrasound and split renal function estimated by renal scintigraphy at first examination (r = 0.98; p < 0.001) and at follow-up (r = 0.91; p < 0.001).

CONCLUSION

We conclude that ultrasound measurement of relative renal volume is capable of assessing split renal function in children with primary vesicoureteral reflux and, thus, should be considered instead of the more invasive MAG3 scintigraphy.