Global Glomerular Filtration Rate Research Articles

Functional recovery after partial nephrectomy: next generation analysis.

To provide a more rigorous assessment of factors affecting functional recovery after partial nephrectomy (PN) using novel tools that allow for analysis of more patients and improved accuracy for assessment of parenchymal volume loss, thereby revealing the potential impact of secondary factors such as ischaemia. Of 1140 patients managed with PN (2012-2014), 670 (59%) had imaging and serum creatinine levels measured before and after PN necessary for inclusion. Recovery from ischaemia was defined as the ipsilateral glomerular filtration rate (GFR) saved normalised by parenchymal volume saved. Acute kidney injury was assessed through Spectrum Score, which quantifies the degree of acute ipsilateral renal dysfunction due to exposure to ischaemia that would otherwise be masked by the contralateral kidney. Multivariable regression was used to identify predictors of Spectrum Score and Recovery from Ischaemia. In all, 409/189/72 patients had warm/cold/zero ischaemia, respectively, with median (interquartile range [IQR]) ischaemia times for cold and warm ischaemia of 30 (25-42) and 22 (18-28) min, respectively. The median (IQR) global preoperative GFR and new baseline GFR (NBGFR) were 78 (63-92) and 69 (54-81) mL/min/1.73 m2 , respectively. The median (IQR) ipsilateral preoperative GFR and NBGFR were 40 (33-47) and 31 (24-38) mL/min/1.73 m2 , respectively. Functional recovery correlated strongly with parenchymal volume preserved (r = 0.83, P < 0.01). The median (IQR) decline in ipsilateral GFR associated with PN was 7.8 (4.5-12) mL/min/1.73 m2 with loss of parenchyma accounting for 81% of this loss. The median (IQR) recovery from ischaemia was similar across the cold/warm/zero ischaemia groups at 96% (90%-102%), 95% (89%-101%), and 97% (91%-102%), respectively. Independent predictors of Spectrum Score were ischaemia time, tumour complexity, and preoperative global GFR. Independent predictors of recovery from ischaemia were insulin-dependent diabetes mellitus, refractory hypertension, warm ischaemia, and Spectrum Score. The main determinant of functional recovery after PN is parenchymal volume preservation. A more robust and rigorous evaluation allowed us to identify secondary factors including comorbidities, increased tumour complexity, and ischaemia-related factors that are also independently associated with impaired recovery, although altogether these were much less impactful.

Parenchymal Mass Loss During Partial Nephrectomy: Role of Devascularized Parenchymal Mass and Excised Parenchymal Mass and Impact on Functional Preservation.

To evaluate the importance of devascularized parenchymal mass(DPM) and excised parenchymal mass(EPM) in functional preservation after standard partial nephrectomy(SPN). Forty-one patients who underwent pure tumor enucleation(TE) and 52 patients who underwent SPN with necessary data were included. As no EPM was lost in TE, the TE samples were used to estimate the degree of volume shrinkage that occurred when the measurements were performed in vivo with blood flow versus ex vivo without, and the shrinkage ratio was calculated as specimen volume divided by tumor volume in vivo. In SPN, the specimen volume comprised tumor volume plus EPM. The EPM was calculated as specimen volume divided by shrinkage ratio minus tumor volume in vivo. The DPM was defined as total ipsilateral parenchymal mass loss minus EPM. T tests, χ2 test, and Mann-Whitney U tests were employed to compare clinical characteristics. Multivariate analysis was used to identify variables that correlated with glomerular filtration rate(GFR) preservation. The mean sizes of devascularized and excised parenchymal masses were 13.6 cm3 and 5.2 cm3 (P=.01), which accounted for 7.8% and 3.4% of preoperative ipsilateral parenchymal mass (P=.03) in SPN, respectively. The shrinkage ratio was 0.71 and correlation coefficient was 0.965. After stepwise regression, DPM, and preoperative GFR were significantly associated with global GFR preservation. The DPM comprises most of parenchymal mass loss after SPN and plays a more important role than EPM on functional outcomes. Surgeons should pay more attention to reducing devascularization during partial nephrectomy.

PD56-01 IMPROVED PREDICTION OF RENAL FUNCTION AFTER RADICAL NEPHRECTOMY

You have accessJournal of UrologyCME1 May 2022PD56-01 IMPROVED PREDICTION OF RENAL FUNCTION AFTER RADICAL NEPHRECTOMY Nityam Rathi, Yosuke Yasuda, Diego Aguilar Palacios, Yunlin Ye, Jianbo Li, Christopher Weight, Mohammed Eltemamy, Robert Abouassaly, and Steven Campbell Nityam RathiNityam Rathi More articles by this author , Yosuke YasudaYosuke Yasuda More articles by this author , Diego Aguilar PalaciosDiego Aguilar Palacios More articles by this author , Yunlin YeYunlin Ye More articles by this author , Jianbo LiJianbo Li More articles by this author , Christopher WeightChristopher Weight More articles by this author , Mohammed EltemamyMohammed Eltemamy More articles by this author , Robert AbouassalyRobert Abouassaly More articles by this author , and Steven CampbellSteven Campbell More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002636.01AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Radical nephrectomy (RN) is an important consideration for the surgical management of localized renal cell carcinoma (RCC), particularly in cases of increased oncologic potential. However, reduced renal function after RN is a concern. Preoperative global glomerular filtration rate (GFR) and split renal function (SRF) in the contralateral kidney have been shown to be strong predictors of new baseline GFR (NBGFR) post-RN. Recently, software has been developed to perform parenchymal volume analysis (PVA) on preoperative imaging to determine SRF (FUJIFILM Medical Systems). We compare the abilities of two SRF-based models, using either nuclear renal scan (NRS) or PVA to determine SRF, to predict NBGFR after RN. These SRF-based models were also compared with subjective prediction of NBGFR by an experienced urologic oncologist, because some believe that an expert can predict such outcomes accurately and that predictive models may not be needed in this domain. METHODS: All 187 RCC patients who underwent RN (2006-16) with preoperative CT/MRI, NRS, and preop/postoperative GFR estimations were analyzed. NBGFR was defined as GFR 3-12 months after RN. For the two SRF-based approaches, SRF was derived from either NRS or semi-automated PVA software, and renal functional compensation was estimated at 25% based on previous studies. Thus, the formula (Global GFRPre-RN × SRFcontralateral) x 1.25 was used to predict NBGFR. For the “Subjective Approach”, a blinded, independent urologic oncologist provided predictions of NBGFR based on preoperative CT/MRI, baseline global GFR, tumor features, and patient age/comorbidities. Predictive accuracies were assessed by correlation coefficients (r). RESULTS: The r for the Subjective Assessment, NRS/SRF-based, and PVA/SRF-based approaches were 0.72, 0.72, and 0.85, respectively (Fig. 1). An SRF-based model using PVA to determine SRF performed better than NRS/SRF-based and Subjective approaches (both p < 0.05). CONCLUSIONS: Software-based PVA more accurately predicts NBGFR after RN than NRS and Subjective Assessment. The readily-available, inexpensive PVA software provides a precise and accurate estimation of SRF from routine preoperative CT/MRI. Clinically, this practical and innovative approach can contribute to the assessment of the merits and risks of RN versus partial nephrectomy in complex RCC cases. Source of Funding: None © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e953 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Nityam Rathi More articles by this author Yosuke Yasuda More articles by this author Diego Aguilar Palacios More articles by this author Yunlin Ye More articles by this author Jianbo Li More articles by this author Christopher Weight More articles by this author Mohammed Eltemamy More articles by this author Robert Abouassaly More articles by this author Steven Campbell More articles by this author Expand All Advertisement PDF DownloadLoading ...

Assessment of glomerular filtration rate measurement in dogs using dynamic contrast CT compared to serum iohexol clearance.

Dynamic contrast CT with Patlak plot analysis can be used to determine the glomerular filtration rate (GFR). However, several studies have shown different GFR values and they are most likely less than the values by the standard techniques. The purpose of this prospective, experimental, and method comparison study was to evaluate the GFR using a CT technique (CT-GFR) in 12 healthy dogs compared to serum iohexol clearance (SIC-GFR). All dogs were anesthetized and placed in the right lateral recumbency position and the caudal part was lifted inside the CT gantry. A single-slice dynamic CT of the aorta and both kidneys was scanned sequentially every 2 s for 2 min after a bolus injection (3mL/s) of iohexol (300 mg/kg). Time attenuation curves (TAC) were constructed and the GFR per volume of kidney was calculated using the Patlak plot analysis method based on 30-120 s time intervals, and results were compared to global GFR from SIC that was determined with eight blood samples for up to 240 min. The CT-GFR value (1.85 ± 0.48 mL/min/kg) was significantly less than the SIC-GFR value (3.40 ± 0.80 mL/min/kg; P<.05). The CT-GFR was correlated with SIC-GFR by the coefficient of correlation (r) at 0.61 (P = .046). In conclusion, the CT-GFR underestimated SIC-GFR and should be used carefully. We suggest that the GFR should be calculated using the equation derived from linear regression between CT-GFR and the standard GFR method. With its own particular parameters, each institute should have its own prediction equation.

Long-Term Oncologic Outcomes After Laparoscopic and Robotic Tumor Enucleation for Renal Cell Carcinoma.

ObjectivesTumor enucleation (TE) optimizes parenchymal preservation with promising short-term oncologic outcomes compared with standard partial nephrectomy (SPN). However, researches/literatures about long-term oncologic outcomes for TE after minimally invasive surgery are scarce. We aim to analyze long-term oncologic outcomes after laparoscopic and robotic tumor enucleation for renal cell carcinoma (RCC).Patients and MethodsWe retrospectively analyzed 146 patients who underwent TE with either laparoscopic or robotic approach for localized RCC in our center. Local recurrence, cancer specific survival (CSS), recurrence free survival (RFS), and overall survival (OS) were the main outcomes. Survival curves were generated using a Kaplan-Meier method. Perioperative outcomes and pathological outcomes were also analyzed.ResultsOverall, 98 male and 48 female patients were eligible for the study. The median tumor size was 3.4 cm with a median R.E.N.A.L. score of seven. Warm ischemia was used in 143 patients with a median ischemia time of 20 min and three patients had zero ischemia. Five patients (3.4%) had major complications (> Clavien IIIa) and only two were related to urinary system. The median global glomerular filtration rate (GFR) preserved after surgery was 93%. Pseudocapsule invasion was reported in 50 tumors (34%) and positive surgical margins were found in 3/146 (2.1%) tumors. At a median follow-up of 66 months, local recurrence happened in two patients (1.4%), and systemic recurrence happened in six patients (4.2%). The 5-year CSS, RFS, OS were 95.7, 89.6, and 91.9%, and the 10-year CSS, RFS, OS were 93.8, 89.6, and 90.0%, respectively.ConclusionThis study indicates that tumor enucleation with laparoscopic or robotic approach in experienced hands for the treatment of RCC appears oncologically safe with a median follow-up of more than 5 years. Prospective studies with more patients and longer follow-up will be required to further evaluate oncologic safety after TE.

Role of Computed Tomography in Estimation of Residual Renal Function at One Year after Donor Nephrectomy: Comparison with Nuclear Scintigraphy.

Computed tomography (CT) is routinely used for preoperative anatomical evaluation of renal donors, but recent studies show that it may be useful as a predictor of renal function too. This study aimed to compare CT volumetry-attenuation-based glomerular filtration rate (GFR) with Tc99m-diethylene-triamine-pentaacetic acid (DTPA) renal scintigraphy GFR and predict post-donor nephrectomy renal function. This is a prospective study involving 39 renal donors at a tertiary care hospital in northern India from 2014 to 2017. Renal volume and attenuation were determined by CT using a semiautomatic tool, and split renal function (SRF) was calculated for each side. CT-GFR was obtained using CT-SRF and global GFR from modification of diet in renal disease equation. At 12 months after nephrectomy, GFR was estimated from serum creatinine (eGFR). Predonation CT-GFR of preserved kidney was used to predict post-nephrectomy renal function which was compared with post-donation renal function calculated using serum creatinine as well as with DTPA-GFR. Pearson correlation coefficient and scatter diagram were used to assess and test the linear relationship between two continuous variables. The Statistical Package for the Social Sciences, version 23, was used for data analysis. There was a highly significant change in mean DTPA-GFR and mean CT-GFR compared to eGFR values (50.79-64.25, 26.50%, and 50.77-64.25, 26.55%, respectively). Similarly, there was a very good correlation between DTPA-GFR and eGFR (r = 0.968, P <0.001) as well as CT-GFR and eGFR (r = 0.968, P <0.001). CT volumetry-attenuation-based GFR accurately predicts post-donor nephrectomy renal function at 1 year similar to Tc99m-DTPA renal scintigraphy.

The role of three-dimensional reconstruction in laparoscopic partial nephrectomy for complex renal tumors

BackgroundTo evaluate the role of three-dimensional (3D) reconstruction technique in renal function protection and ipsilateral parenchymal mass preserved after laparoscopic partial nephrectomy (LPN) in patients with complex renal tumor (R.E.N.A.L.score ≥ 8).MethodsA retrospective study enrolling 49 patients who suffered from RCC and underwent LPN at our center, from October 1, 2017, to October 31, 2018. Twenty-one patients (group A) underwent LPN with the 3D reconstruction technique before surgery, and the other 28 patients (group B) not. Preoperative and postoperative ipsilateral parenchymal mass volume and ipsilateral glomerular filtration rate (GFR) were analyzed 3–5 days prior and 3 months after PN. In order to compare the two groups, Mann-Whitney U test and chi-square tests were performed. The main limitation of this technique is that the volume calculations are partly performed manually.ResultsAll patients’ median renal score was 10 with no difference between the two groups (P = 0.89), and the median tumor size of the two groups was 3.2 cm (group A) and 3.3 cm (group B) respectively (P = 0.14). In addition, the median warm ischemia time of the two groups was 21 min (group A) and 26 min (group B) (P = 0.003). In group A and group B, the rate of preserved global GFR was 88% and 86% (P = 0.06), preserved ipsilateral GFR was 80% and 77% (P = 0.01), and preserved ipsilateral parenchymal was 84% and 80% (P = 0.03) separately.Conclusion3D reconstruction technique was a beneficial method for more renal function and more preserved renal parenchymal mass volume after LPN.Trial registrationYantai Yuhuangding Hospital, YHD[2017]212. Registered 1 January 2017 (prospectively registered), http://www.ytyhdyy.com/nav/103.htm.

PD07-11 TUMOR CONTACT SURFACE AREA AS A PREDICTOR OF FUNCTIONAL OUTCOMES AFTER PARTIAL NEPHRECTOMY

You have accessJournal of UrologyKidney Cancer: Localized: Surgical Therapy I1 Apr 2018PD07-11 TUMOR CONTACT SURFACE AREA AS A PREDICTOR OF FUNCTIONAL OUTCOMES AFTER PARTIAL NEPHRECTOMY Chalairat Suk-Ouichai, Wen Dong, Jitao Wu, Hajime Tanaka, JJ H. Zhang, Elvis R. Caraballo, Erick Remer, Jianbo Li, Sudhir Isharwal, and Steven C. Campbell Chalairat Suk-OuichaiChalairat Suk-Ouichai More articles by this author , Wen DongWen Dong More articles by this author , Jitao WuJitao Wu More articles by this author , Hajime TanakaHajime Tanaka More articles by this author , JJ H. ZhangJJ H. Zhang More articles by this author , Elvis R. CaraballoElvis R. Caraballo More articles by this author , Erick RemerErick Remer More articles by this author , Jianbo LiJianbo Li More articles by this author , Sudhir IsharwalSudhir Isharwal More articles by this author , and Steven C. CampbellSteven C. Campbell More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.444AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES New baseline glomerular filtration rate (GFR) can be a major factor for cancer survivorship after renal cancer surgery. Parenchymal mass preservation is the predominant factor associated with functional outcomes after partial nephrectomy (PN). Contact surface area (CSA) between the tumor and parenchyma may impact parenchymal preservation and predict functional outcomes after PN. We evaluated CSA as a predictor of parenchymal mass and function preserved by PN. METHODS 419 patients managed with PN had necessary studies to evaluate preoperative and postoperative parenchymal mass and renal function within the operated kidney. Patients with multifocal renal masses were excluded. Parenchymal mass in the operated kidney and CSA were measured using contrast-enhanced CT within 2 months prior to and 3-12 months after PN. CSA was calculated using mathematical formula: 2πrd, where r=radius and d=intraparenchymal depth of tumor. Pearson correlation evaluated relationships between CSA and parenchymal mass or GFR preservation. Multivariable linear regression assessed predictors for GFR preservation. Conceptually, the formula for CSA should function best for exophytic tumors, while predictive value for endophytic tumors may not be as strong. RESULTS Median tumor size and R.E.N.A.L. were 3.5 cm and 8, respectively. Median global and ipsilateral GFR preserved were 89% and 79%, respectively. Median ipsilateral parenchymal mass preserved was 85% and significantly higher for exophytic masses (87% vs 83%, p=0.001). Median CSA was 22.8cm2 and significantly less for exophytic masses (19.8cm2 vs 24.6cm2, p=0.02). CSA associated modestly with both ipsilateral GFR and mass preserved (r=0.25 and 0.36, respectively, both p<0.001). On multivariable analysis, CSA associated with ipsilateral GFR preserved for exophytic masses (p=0.011), but not for endophytic ones (p=0.27). Limitations include retrospective design. CONCLUSIONS CSA, which can be estimated preoperatively, associates with parenchymal mass and function saved after PN, although its utility appears to be greatest for exophytic rather than endophytic tumors. Further study will be required to validate the utility of CSA in different clinical settings. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e160-e161 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Chalairat Suk-Ouichai More articles by this author Wen Dong More articles by this author Jitao Wu More articles by this author Hajime Tanaka More articles by this author JJ H. Zhang More articles by this author Elvis R. Caraballo More articles by this author Erick Remer More articles by this author Jianbo Li More articles by this author Sudhir Isharwal More articles by this author Steven C. Campbell More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Tumor Contact Surface Area As a Predictor of Functional Outcomes After Standard Partial Nephrectomy: Utility and Limitations

To evaluate contact surface area (CSA) between the tumor and parenchyma as a predictor of ipsilateral parenchyma and function preserved after partial nephrectomy (PN). Previous studies suggested that CSA is a strong predictor of functional outcomes but the limitations of CSA have not been adequately explored. Four hundred nineteen patients managed with standard PN for solitary tumor with necessary studies to evaluate and analyze ipsilateral preoperative or postoperative parenchymal mass and function. Parenchymal mass and CSA were measured using contrast-enhanced computed tomography <2 months prior and 3-12months after PN. CSA was calculated: 2πrd, where r = radius and d = intraparenchymal depth. Pearson-correlation evaluated relationships between CSA and ipsilateral parenchymal mass or function preserved. Multivariable regression assessed predictors of function preserved. Conceptually, the CSA paradigm should function better for exophytic tumors than endophytic ones. Median tumor size was 3.5 cm and R.E.N.A.L. was 8. Median global and ipsilateral glomerular filtration rate preserved were 89% and 79%, respectively. Median ipsilateral parenchymal mass preserved was 85% and significantly higher for exophytic masses (P = .001). Median CSA was 22.8 cm2 and significantly less for exophytic masses (P = .02). CSA associated with both ipsilateral function and mass preserved (both P < .05), but the correlations were only modest (r = 0.25 and 0.36, respectively). On multivariable analysis, CSA associated with function preserved for exophytic masses (P = .01), but not for endophytic ones (P = .27). CSA associates with functional outcomes after standard PN, although the strength of the correlations was modest, unlike previous studies, and CSA was not an independent predictor for endophytic tumors. Further study will be required to evaluate the utility of CSA in various clinical settings.

Functional Comparison of Renal Tumor Enucleation Versus Standard Partial Nephrectomy

BackgroundTumor enucleation (TE) optimizes parenchymal preservation and could yield better function than standard partial nephrectomy (SPN), although data on this are conflicting. ObjectiveTo compare functional outcomes for TE and SPN strategies. Design, setting, and participantsPatients managed with partial nephrectomy (PN) with necessary data for analysis of preservation of ipsilateral parenchymal mass (IPM) and global glomerular filtration rate (GFR) from two centers were included. All studies were required <2 mo before and 3–12 mo after surgery. Patients with a solitary kidney or multifocal tumors were excluded. InterventionPartial nephrectomy. Outcome measurements and statistical analysisVascularized IPM was estimated from contrast-enhanced CT scans preoperatively and postoperatively. Serum creatinine-based estimates of global GFR were also obtained in the same timeframes. Univariable and multivariable linear regression evaluated factors associated with new-baseline global GFR. Results/limitationsAnalysis included 71 TE and 373 SPN cases. The median preoperative global GFR was comparable for TE and SPN (75 vs 78ml/min/1.73m2; p=0.6). The median tumor size was 3.0cm for TE and 3.3cm for SPN (p=0.03). The median RENAL score was 7 in both cohorts. For TE, warm ischemia and zero ischemia were used in 51% and 49% of cases, respectively. For SPN, warm ischemia and cold ischemia were used in 72% and 28% of patients, respectively. Capsular closure was performed in 46% of TE and 100% of SPN cases (p<0.001). Positive margins were found in 8.5% of TE and 4.8% of SPN patients (p=0.2). The median vascularized IPM preserved was 95% (interquartile range [IQR] 91–100%) for TE and 84% (IQR 76–92%) for SPN (p<0.001). The median global GFR preserved was 101%(IQR 93–111%) and 89% (IQR 81–96%) for TE and SPN, respectively (p<0.001). On multivariable analysis, resection strategy, preoperative GFR, and vascularized IPM preserved were all significantly associated (p<0.001) with new-baseline global GFR. Limitations include the retrospective design and the lack of resection outcome data. ConclusionsOur analysis suggests that TE has potential for maximum IPM preservation compared to SPN and may provide optimized functional recovery. Further investigation will be required to evaluate the clinical significance of these findings. Patient summaryTumor enucleation for kidney cancer involves dissection along the tumor capsule and optimally preserves normal kidney tissue, which may lead to better functional recovery. The importance of this approach in various clinical settings will require further investigation.

Excised Parenchymal Mass During Partial Nephrectomy: Functional Implications

To evaluate whether excised parenchymal mass (EPM) during partial nephrectomy (PN) correlates with functional decline and can serve as a surrogate for functional outcomes. All 215 patients managed with PN for unifocal renal mass with necessary studies to determine EPM and percent glomerular filtration rate (GFR) and parenchymal mass preserved (both global and specific to the operated kidney) were analyzed. EPM was estimated from the pathologic specimen by subtracting the tumor mass from the specimen mass, with both calculated using the elliptical formula. Vascularized parenchymal mass preserved was measured from computed tomography scans obtained <2 months prior and 3-12 months after surgery. All functional analyses were required to be within the same time frames, and patients with a contralateral kidney were also required to have nuclear renal scans. The median tumor size was 3.5 cm and the median R.E.N.A.L. was 7. Warm and cold ischemia were utilized in 123 and 92 patients, respectively (median ischemia time = 23 minutes). The median global GFR preserved was 89%, the median total parenchymal mass preserved was 93%, and the median estimated EPM was 16 cm3. Whereas percent parenchymal mass preserved correlated strongly with global and ipsilateral GFR preserved (both P < .001), EPM failed to correlate with functional outcomes on both univariable and multivariable analyses. Our data suggest that parenchymal mass preserved with standard PN by experienced surgeons associates strongly with function preserved, whereas EPM fails to correlate with functional outcomes. Further study of the functional impact of EPM in other circumstances will be required, such as enucleation or PN performed by less-experienced surgeons.

Impact of stereotactic radiotherapy on kidney function in primary renal cell carcinoma: Establishing a dose–response relationship

Background and purposeTo evaluate renal dysfunction after stereotactic ablative body radiotherapy (SABR) for inoperable primary renal cell carcinoma (RCC) using nuclear medicine assessments. Materials and methodsIn a prospective clinical trial, patients received single fraction renal SABR (26Gy) for tumours <5cm, or fractionated SABR (3×14Gy) for tumours ⩾5cm. Global and regional glomerular filtration rate (GFR) was calculated through 51Cr-EDTA and 99mTc-DMSA SPECT/CT, respectively, at baseline and post-treatment (14, 90days and at 1-year). Regional loss in function was correlated to the absolute and biologically effective doses (BED) delivered. ResultsIn 21 patients the mean (range) tumour size was 48mm (21–75mm). The mean±SD GFR at baseline was 52±24ml/min. Net change in mean GFR was +0.6±11.3, +3.2±14.5 and −8.7±13.4 ml/min (p=0.03) at 2weeks, 3months and 1year, respectively. For every 10Gy of physical dose delivered, an exponential decline in affected kidney GFR was observed at 39% for 26Gy/1 fraction and 25% for 42Gy/3 fractions. When normalised to BED3Gy, the dose–response relationship for each treatment prescription was similar with a plateau beyond 100Gy. The R50% conformity index correlated with GFR loss (p=0.04). No patient required dialysis. ConclusionsSABR results in clinically acceptable and dose-dependent renal dysfunction at 1-year. Sparing functional kidney from high-dose regions (>50% isodoses) may help reduce risk of functional loss.

Effect of Body Mass Index on Outcomes of Peritoneal Dialysis Patients in India

We studied the effect of body mass index (BMI) at peritoneal dialysis (PD) initiation on patient and technique survival and on peritonitis during follow-up. We followed 328 incident patients on PD (176 with diabetes; 242 men; mean age: 52.6 ± 12.6 years; mean BMI: 21.9 ± 3.8 kg/m(2)) for 20.0 ± 14.3 months. Patients were categorized into four BMI groups: obese, ≥ 25 kg/m(2); overweight, 23 - 24.9 kg/m(2); normal, 18.5 - 22.9 kg/m(2) (reference category); and underweight, <18.5 kg/m(2). The outcomes of interest were compared between the groups. Of the 328 patients, 47 (14.3%) were underweight, 171 (52.1%) were normal weight, 53 (16.2%) were overweight, and 57 (17.4%) were obese at commencement of PD therapy. The crude hazard ratio (HR) for mortality (p = 0.004) and the HR adjusted for age, subjective global assessment, comorbidities, albumin, diabetes, and residual glomerular filtration rate (p = 0.02) were both significantly greater in the underweight group than in the normal-weight group. In comparison with the reference category, the HR for mortality was significantly greater for underweight PD patients with diabetes [2.7; 95% confidence interval (CI): 1.5 to 5.0; p = 0.002], but similar for all BMI categories of nondiabetic PD patients. Median patient survival was statistically inferior in underweight patients than in patients having a normal BMI. Median patient survival in underweight, normal, overweight, and obese patients was, respectively, 26 patient-months (95% CI: 20.9 to 31.0 patient-months), 50 patient-months (95% CI: 33.6 to 66.4 patient-months), 57.7 patient-months (95% CI: 33.2 to 82.2 patient-months), and 49 patient-months (95% CI: 18.4 to 79.6 patient-months; p = 0.015). Death-censored technique survival was statistically similar in all BMI categories. In comparison with the reference category, the odds ratio for peritonitis occurrence was 1.8 (95% CI: 0.9 to 3.4; p = 0.086) for underweight patients; 1.7 (95% CI: 0.9 to 3.2; p = 0.091) for overweight patients; and 3.4 (95% CI: 1.8 to 6.4; p < 0.001) for obese patients. In our PD patients, mean BMI was within the normal range. The HR for mortality was significantly greater for underweight diabetic PD patients than for patients in the reference category. Death-censored technique survival was similar in all BMI categories. Obese patients had a greater risk of peritonitis.

ESTIMATION OF GLOMERULAR FILTRATION RATE IN HEALTHY CATS USING SINGLE‐SLICE DYNAMICCTANDPATLAK PLOT ANALYSIS

Commonly used clinical indicators of renal disease are either insensitive to early dysfunction or have delayed results. Decreased glomerular filtration rate (GFR) indicates renal dysfunction before there is a loss of 50% of functional nephrons. Most tests evaluate global rather than individual kidney function. Dynamic computed tomography (CT) and Patlak plot analysis allows for individual GFR to be tested. Our objectives were to establish a procedure and provide reference values for determination of global GFR in 10 healthy cats using dynamic CT (CTGFR). This method of GFR determination was compared against serum iohexol clearance (SIC). A single CT slice centered on both kidneys and the aorta was acquired every fifth second during and after a bolus injection of iohexol (240 mgI/ml; 300 mgI/kg) for 115 s. Using data from this dynamic acquisition, Patlak plots were obtained, GFR was calculated, and results were compared to global GFR determined by iohexol clearance. The average global CTGFR estimate was 1.84 ml/min x kg (SD = 0.43; range = [1.22, 2.45]). The average global GFR measured using SIC was 2.45 ml/min x kg (SD = 0.58; range = [1.72, 3.69]). GFR measurements estimated by both dynamic CT and SIC were positively associated (estimated Spearman rank correlation coefficient = 0.72; P = 0.0234). The CTGFR method consistently underestimated GFR with a bias of -0.62 (SE = 0.1307) when compared to SIC (P = 0.0011). In healthy cats, CTGFR was capable of determining individual kidney function and appears clinically promising.

Evaluation of glomerular filtration rate by use of dynamic computed tomography and Patlak analysis in clinically normal cats

To obtain quantitative variables of the abdominal aorta and both kidneys on the basis of time-attenuation curves (TACs) and to measure glomerular filtration rate (GFR) for each kidney and the global GFR in clinically normal cats by use of dynamic computed tomography (CT) and Patlak analysis. 9 healthy cats. All the cats were anesthetized with propofol. Anesthesia was maintained by administration of isoflurane, and CT examination was performed in the anesthetized cats. The TACs and renal volume were measured by use of the baseline precontrast and single-slice dynamic scans. The CT-GFR of each kidney and the global CT-GFRs were calculated via Patlak plot analysis. CT-GFR results from 7 cats were valid. Peak aortic enhancement was detected between 9.0 and 14.0 seconds after iohexol injection, and the initial peak time of renal parenchymal enhancement was 15 to 24 seconds after iohexol injection. Mean ± SD global GFR was 2.06 ± 0.62 mL/min/kg. Mean ± SD CT-GFR of the right and left kidneys was 0.97 ± 0.32 mL/min/kg and 1.05 ± 0.31 mL/min/kg, respectively. The CT-GFR method can be rapidly and conveniently performed in clinically normal cats. This combined structural-functional approach provided physiologic and morphological information on the kidneys of cats.

DIURETIC RENAL SCINTIGRAPHY IN NORMAL CATS

The purpose of this study was to develop a protocol for diuretic renal scintigraphy (renography) in cats and describe normal findings. 99mTc-DTPA renal scintigraphy was performed twice in 10 healthy cats. Furosemide or saline were injected 4.5 min after radiopharmaceutical administration for the diuretic or control scan, respectively. A dynamic acquisition was performed for 8 min. The following parameters were evaluated: (1) global and individual glomerular filtration rate (GFR); (2) shape of the time-activity curve (TAC); (3) time of peak (TOP); (4) individual kidney excretion half-time (T1/2) of the radiopharmaceutical; (5) percentage of maximum activity measured at the end of the study. Global GFR in the control studies (2.79 +/- 0.83 ml/min/kg, mean +/- SD) did not differ significantly from the diuretic scans (2.34 +/- 0.51 ml/min/kg). The shape of most (16/ 20) TAC of diuretic renograms was similar to those of control renograms. The TOP of the diuretic renogram curves was 3.06 +/- 0.58 min, and did not differ from that of the control scans (3.01 +/- 0.61 min). T1/2 of the diuretic renograms was significantly shorter (5.15 +/- 0.83 min) than that of the control renograms (6.31 +/- 1.50 min). A significantly lower percentage of maximum activity was present at the end of the study in diuretic renograms (median: 47.25%; range: 33.60-59.60%) compared with control renograms (63.40%; 30.00-69.40%). Diuretic renal scintigraphy is a noninvasive and fast procedure to perform in cats. The applicability of this technique needs to be investigated in patients with significantly impaired renal function and obstructive uropathies.

A Single Sample Method for Evaluating51Chromium‐Ethylene Diaminic Tetraacetic Acid Clearance in Normal and Hyperthyroid Cats

Chronic kidney failure is frequently seen in middle-aged and elderly cats. 51Chromium-ethylene diaminic tetraacetic acid (51Cr-EDTA) clearance and single blood sample (SBS) method are used in several species to estimate the glomerular filtration rate (GFR). The hypothesis of this study was that 51Cr-EDTA clearance could be determined using an SBS method in normal and hyperthyroid cats. Forty-six cats were included in this study, with an average age of 9.5 years. Of these cats, 27 had hyperthyroidism; 19 were healthy. After IV injection of 51Cr-EDTA (average dose: 4.25 MBq), 7 blood samples were obtained between 5 and 240 minutes. Reference clearance was calculated in mL/min and mL/min/kg body weight, using a 2-compartment model. Optimal time for clearance measurement with SBS was then determined by systematically comparing each individual plasma concentration to the reference multisample clearance. The average reference plasma clearance of 51Cr-EDTA for all cats was 14.9 mL/min (3.7 mL/min/kg). The clearance in hyperthyroid cats averaged 16.4 mL/min (4.3 mL/min/kg) and in normal cats averaged 10.3 mL/min (2.4 mL/min/kg). The optimal time for the SBS was 48 minutes after injection of tracer 51Cr-EDTA (R2= 0.9414), giving the following converting equation: clearance = (0.0066 x DV48 minutes) - 0.9277 (in mL/min). In this study, the single sample 51Cr-EDTA clearance method was used to estimate the global GFR in cats. The method identified differences in clearance between normal and hyperthyroid cats. The optimal time for an SBS was 48 minutes.

DIURETIC RENAL SCINTIGRAPHY IN NORMAL DOGS

Diuretic renal scintigraphy is commonly used in human medicine to differentiate obstructive from nonobstructive pyelectasia. In order to determine normal parameters, 99mTc-DTPA renal scintigraphy was performed twice in 20 healthy adult Mongrel dogs. Each dog was injected with either 3.0 mg/kg furosemide or an equivalent volume of saline 4.5 min following injection of the radiopharmaceutical. The following parameters were evaluated: (1) global and individual glomerular filtration rate (GFR); (2) time of peak (TOP) of the time-activity curve (TAC); (3) shape of the TAC; (4) individual kidney excretion half-time (T1/2); (5) proportion of maximum activity measured at end of study (8 min); (6) time of onset; and (7) duration of the effect of the diuretic. Most TAC in the diuretic renography group showed a steep drop in the curve following administration of the diuretic compared with a gradual slope in the saline control group. There was a statistically significant difference in T1/2 between the control renograms (median 10.25 min, range 4.41-18.07 min) and the diuretic renograms (median 4.16 min, range 3.62-5.90 min). There was a statistically significant difference in percentage maximum activity between the control renograms (median 65.25%, range 48.27-93.68%) and the diuretic renograms (median 48.54%, range 35.64-58.76%). Median time of onset of the diuretic effect was 1.10 min (0.20-2.40 min), and median duration was 0.83 min (0.30-2.35 min).

DETERMINATION OF GLOMERULAR FILTRATION RATE IN DOGS USING CONTRAST‐ENHANCED COMPUTED TOMOGRAPHY

The purpose of this project was to establish a procedure and reference values for glomerular filtration rate (GFR) using contrast-enhanced computed tomography (CT) in eight healthy dogs. A single section of the kidney was scanned sequentially after bolus injection (3 ml/s) of iohexol (300 mg/kg). Time-attenuation curves were constructed and the GFR per volume of kidney was calculated using Patlak graphical analysis software. The GFR was then converted from contrast clearance per unit volume (ml/min/ml) to contrast clearance per body weight (ml/min/kg). Individual kidney and global GFR were calculated using both CT and nuclear scintigraphy. Global GFR for each dog was also determined by plasma iohexol clearance. Contrast-enhanced CT underestimated the global GFR compared with the other two methods. The average global GFR was 2.57 +/- 0.33 ml/ min/kg using functional CT and 4.06 +/- 0.37 ml/min/kg using plasma iohexol clearance. There was significant (P < 0.05) interobserver variability of CT GFR of the right kidney and total GFR. There was decreased interobserver variability for the left kidney. There was no difference in the intraobserver variability for CT-determined individual kidney and global GFR. There was no difference between the motion corrected and nonmotion corrected values for individual and global CT GFR. Nuclear scintigraphy produced a slightly higher coefficient of variation than contrast-enhanced CT, 2.9% and 1.0%, respectively. It is hypothesized that altered renal blood flow, hematocrit of the small vessels, and nephrotoxicity play a role in the underestimation of GFR by contrast-enhanced CT.

EVALUATION OF99MTC‐DIETHYLENETRIAMINEPENTAACETIC ACID RENAL SCINTIGRAM CURVES IN NORMAL DOGS AFTER INDUCTION OF DIURESIS

The normal 99mTc-diethylenetriaminepentaacetic acid (DTPA) renal scintigram curve has 3 distinct phases; an arterial phase followed by progressive uptake and subsequent excretion from the kidney. In dogs with X-linked hereditary nephritis, a distinct flattening of the renal scintigram curve has been observed prior to any decline in glomerular filtration rate (GFR). The cause of this shape change is not known, however, it coincided with decreased urine-specific gravity and thus might be related to polyuria. To further evaluate this possibility, we assessed whether diuresis without concurrent renal disease could flatten the 99mTc-DTPA renal scintigram curve. GFR scintigraphy was performed in six healthy dogs once as a baseline, and again after induction of diuresis by each of four different methods. Scintigram curves were evaluated subjectively as well as quantitatively by calculation of GFR estimates, mean renal transit times, time to peak activity and half-time clearance. Complete flattening of the renal scintigram curve did not occur with diuresis alone, and therefore, flattening of the scintigram curve may serve as an early indicator of renal dysfunction. However, during diuresis after intravenous saline administration, alterations in time to peak activity and mean renal transit time may create inaccuracies in GFR estimates based on the conventional regression formula that cause a false lowering of the resultant global GFR value.