Novel prediction model of renal function after nephrectomy from automated renal volumetry with preoperative multidetector computed tomography (MDCT)

Impact of Accessory Renal Artery Embolization on Renal Deterioration Under Endovascular Aortic Repair

OBJECTIVE

The optimal management strategy for patients with accessory renal arteries undergoing endovascular aortic repair is unclear. This study aimed to investigate the impact of accessory renal artery (aRA) embolization on postoperative renal deterioration and to identify the predictors of postoperative renal deterioration in patients who underwent endovascular aortic repair (EVAR).

METHODS

A retrospective single-centre observational study was conducted at our hospital. Of 331 consecutive patients who underwent endovascular aortic repair between April 2011 and February 2021, 29 patients with an aRA were included in this study. Spearman's rank correlation coefficients of decrease in estimated glomerular filtration rate (eGFR), renal volume reduction rate, infarcted renal volume, and quantity of contrast use for postoperative renal deterioration were analyzed. The correlation coefficients of the correlations between infarcted renal volume, renal volume reduction rate, and decrease in eGFR and the rate of aRA diameter were also analyzed. Multivariable nominal logistic regression analyses were conducted to evaluate the odds of postoperative renal deterioration.

RESULTS

The renal volume reduction rate and infarcted renal volume had a significant positive correlation with the decrease in eGFR. Body surface area and preoperative renal volume were significantly but negatively correlated with the decrease in eGFR. The infarcted renal volume, renal volume reduction rate, and decrease in eGFR were significantly and positively correlated with the aRA diameter. The odds ratio for decreased eGFR rate in preoperative renal volume was .96 (95% CI 0.930‒.996, P = .009).

CONCLUSIONS

EVAR with aRA embolization impacts postoperative renal deterioration in patients with preoperative low renal volume, and the diameter of the embolized aRA might be a predictor of postoperative renal deterioration.

Role of preoperative MR volumetry in patients with renal cell carcinoma for prediction of postoperative renal function after radical nephrectomy and nephron sparing surgery

Purpose

Preoperative computed tomography or magnetic resonance (MR) imaging are commonly used for radiological evaluation of renal cell carcinoma (RCC) before radical nephrectomy or nephron sparing surgery(NSS). This study aimed to assess the role of MRI for predicting postoperative renal function by preoperative estimation of renal parenchymal volume and correlation with glomerular filtration rate (GFR).

Materials and Methods

A prospective observational study was conducted from February 2015 to October 2016 at a tertiary care hospital in northern India. MR imaging was done on 3 Tesla MR scanner (Signa Hdxt General Electrics, Milwaukee, USA). MR volumetry was used to estimate the renal parenchymal volume. GFR was measured in all patients using Tc99m Diethyl-triamine-penta-acetic acid using Russell’s algorithm. Such measurement was done preoperatively, and postoperatively 3 months after surgery.

Results

30 patients with suspected RCC underwent NSS (n=10) and radical nephrectomy (n=20). Median tumour volume was 175.7cc (range: 4.8 to 631.8cc). The median volume of the residual parenchyma on the affected side was 84.25±41.97cc while that on the unaffected side was 112.25±26.35cc. There was good correlation among the unaffected kidney volume and postoperative GFR for the radical nephrectomy group (r=0.83) as well as unaffected kidney volume, total residual kidney volume and residual volume of affected kidney with postoperative GFR for the NSS group (r=0.71, r=0.73, r=0.79 respectively; P <0.05).

Conclusion

Preoperative residual parenchymal volume on MR renal volumetry correlates well with postoperative GFR in patients with RCC undergoing radical nephrectomy or NSS.

Preserved Kidney Volume, Body Mass Index, and Age Are Significant Preoperative Factors for Predicting Estimated Glomerular Filtration Rate in Living Kidney Donors at 1 Year After Donation

BACKGROUND

Securing postdonation renal function in the lifetime of donors is a consequential subject for physicians, and precise prediction of postdonation renal function would be considerably beneficial when judging the feasibility of kidney donation. The aim of this study was to investigate the optimum model for predicting eGFR at 1 year after kidney donation.

METHODS

We enrolled 101 living-related kidney donors for the development cohort and 44 for the external validation cohort. All patients in each cohort underwent thin-sliced (1 mm) enhanced computed tomography (CT) scans. We excluded individuals with diabetes, glucose intolerance, or albuminuria from this study. We evaluated preoperative factors including age, sex, hypertension, body mass index (BMI), serum uric acid, baseline eGFR, and body surface area (BSA)-adjusted preserved kidney volume (PKV) by using 3-dimensional reconstruction of thin-sliced enhanced CT images. To detect independent predictors, we performed multivariable regression analysis.

RESULTS

The multivariable regression analysis revealed that age, BMI, predonation eGFR, and BSA-adjusted PKV were independent predictors of eGFR at 1 year after kidney donation (correlation coefficient: -0.15, -0.476, 0.521, 0.127, respectively). A strong correlation between predicted eGFR and observed eGFR was obtained in the development cohort (r = 0.839, P < .0001). The significance of this predictive model was also confirmed with the external validation cohort (r = 0.797, P < .0001).

CONCLUSIONS

Age, BMI, predonation eGFR, and BSA-adjusted PKV may be useful for precisely predicting eGFR at 1 year after living kidney donation and be helpful to determine the feasibility of kidney donation from marginal donors.

Renal Artery Diameter Is a Surrogate Marker for Kidney Volume in Living Kidney Donors

Donor kidney volume (KV) is an increasingly important parameter evaluated before living kidney donation; however, KV measurements on computed tomographic (CT) scanning requires a manually intensive process of manual or semiautomatic segmentation of kidneys with interobserver variation. Renal artery diameter (RAD) is an easier marker to measure, and this study aims to investigate the relationship between donor RAD and KV.

METHODS

A retrospective review of 77 patients who underwent living donor nephrectomy was conducted. Bilateral KVs were measured based on contrast-enhanced CT scan imaging, and renal artery maximum diameter was measured by direct visualization on the arterial phase of transverse CT sections.

RESULTS

On regression analysis, there was a significant association between the right and left RADs and their ipsilateral KVs with a regression coefficient of 7.9 (95% CI, 1.3-14.5; P = .02) and 9.8 (95% CI, 3.3-16.3; P = .004), respectively. Mean total RAD correlated with total KV with a regression coefficient of 9.3 (95% CI, 3.8-14.7; P = .001) and weakly correlated with estimated glomerular filtration rate with a Pearson coefficient of .10.

CONCLUSIONS

This study demonstrates that renal artery size is positively associated with KV and may be used as an easily measured surrogate marker for kidney size with its attended implications in living donor transplantation.

Accuracy of implementing principles of fusion imaging in the follow up and surveillance of complex aneurysm repair

Fusion imaging is standard for the endovascular treatment of complex aortic aneurysms, but its role in follow up has not been explored. A critical issue is renal function deterioration over time. Renal volume has been used as a marker of renal impairment; however, it is not reproducible and remains a complex and resource-intensive procedure. The aim of this study is to determine the accuracy of a fusion-based software to automatically calculate the renal volume changes during follow up. In this study, computerized tomography (CT) scans of 16 patients who underwent complex aortic endovascular repair were analysed. Preoperative, 1-month and 1-year follow-up CT scans have been analysed using a conventional approach of semi-automatic segmentation, and a second approach with automatic segmentation. For each kidney and at each time point the percentage of change in renal volume was calculated using both techniques. After review, volume assessment was feasible for all CT scans. For the left kidney, the intraclass correlation coefficient (ICC) was 0.794 and 0.877 at 1 month and 1 year, respectively. For the right side, the ICC was 0.817 at 1 month and 0.966 at 1 year. The automated technique reliably detected a decrease in renal volume for the eight patients with occluded renal arteries during follow up. This is the first report of a fusion-based algorithm to detect changes in renal volume during postoperative surveillance using an automated process. Using this technique, the standardized assessment of renal volume could be implemented with greater ease and reproducibility and serve as a warning of potential renal impairment.

Automated renal cortical volume measurement for assessment of renal function in patients undergoing radical nephrectomy

BACKGROUND

Renal volume change greatly affects renal function after nephrectomy. Although various measuring techniques were reported, no standard measuring method is available. In this study, we examined the computational automated volumetric method, and evaluated the volumetric change to assess the functional outcome in patients undergoing radical nephrectomy. We developed the predictive equation for postoperative renal function from volume alternation and validated the performance.

METHODS

Thirty-two patients undergoing radical nephrectomy participated in this study. Renal volume was calculated using three different methods [ellipsoid method, conventional manual voxel count method for renal parenchyma (manual RPV), and automated voxel count method for renal cortex (automated RCV)] through newly developed imaging software. Statistical analysis was performed to evaluate the correlation between renal functional alternation 7 days after the nephrectomy and renal volumetric change. A simple predictive equation for the postoperative renal function by renal volume loss was developed and externally validated through another 12 cases.

RESULTS

The automated RCV method had the strongest correlation between renal function alternation and RCV change (R = 0.82), than manual RPV (R = 0.69) and ellipsoid method (R = 0.50). Subsequently, a simple equation for postoperative renal function by renal volume alternation was developed: predicted postoperative estimated glomerular filtration rate (eGFR) from renal volume change = preoperative eGFR × (postoperative renal volume / preoperative renal volume). In the external validation cohort, automated RCV demonstrated the predictive performance of the constructed equations for renal function (R = 0.77).

CONCLUSIONS

The computational automated RCV measurements is a simple estimation of renal functional outcome for patients undergoing radical nephrectomy.

Compensatory Structural and Functional Adaptation After Nephrectomy in Obese Patients According to Waist Circumference

OBJECTIVE

To investigate whether the postnephrectomy renal adaptation mechanism, focused on functional hyperfiltration as well as structural hypertrophy, was affected by abdominal obesity.

MATERIALS AND METHODS

We retrospectively evaluated 358 patients who underwent simple or radical nephrectomy and nephroureterectomy between 2009 and 2013. Patients were classified according to waist circumference (WC), with values >102 cm in men and >88 cm in women considered high (obesity). Functional renal volume (FRV) was measured using computed tomography performed preoperatively and 6 months postoperatively to evaluate the degree of remnant kidney hypertrophy. The degree of hyperfiltration was calculated from the difference between the preoperative and postoperative glomerular filtration rate (GFR)/FRV.

RESULTS

The mean preoperative GFR, FRV, and GFR/FRV were 72.1 mL/min/1.73 m², 282.8 cm³, and 0.25 mL/min/1.73 m²/cm³, respectively. The percent GFR reduction was significantly greater in the high WC group (high, 25.9% vs normal, 16.0%, P = .036), although the degree of hypertrophic volume in the remnant kidney showed no difference. The change in GFR/FRV was statistically lower in the high WC group (high, 25.7% vs normal, 40.2%, P = .009). The factors associated with postoperative increased GFR/FRV were low preoperative GFR, proteinuria, high predictive preserved functional parenchymal volume ratio, absence of hypertension, increased levels of high-density lipoprotein cholesterol, and normal WC (all P < .05).

CONCLUSION

Patients with high WC might have a large reduction in postoperative renal function, owing to a lower degree of functional hyperfiltration.

Quantification of bleeding volume using computed tomography and clinical complications after percutaneous renal biopsy

Background: The aim of this study was to investigate specific bleeding volume after percutaneous renal biopsy (PRB) and the correlation between bleeding volume and clinical parameters.

Methods: A retrospective study of 252 consecutive patients (153 male patients and 99 female patients) who underwent PRB at the Department of Nephrology, Japanese Red Cross Ishinomaki Hospital, between July 2013 and January 2016 was conducted. PRB was performed under ultrasound guidance using an automated spring-loaded biopsy device and a 16-cm, 16-gauge needle. Patients underwent computed tomography (CT) the day after PRB. Bleeding volume after PRB was evaluated using reconstructed CT data.

Results: The median bleeding volume after PRB was 38 mL (25th–75th percentile, 18–85 mL), with ≥4 punctures identified as a risk factor for massive bleeding. The incidence rates of macrohematuria, transient hypotension and bladder obstruction were 14.3, 8.7 and 4.7%, respectively. Post-PRB blood transfusion and intervention were required in 4.7 and 0.8% of patients, respectively.

Conclusion: Although it is difficult to assess the risk for massive bleeding prior to PRB, we do provide evidence of a specific increased risk with ≥4 puncture attempts, and recommend careful follow-up of these patients.