Eric Remer

Acute Kidney Injury after Partial Nephrectomy: Role of Parenchymal Mass Reduction and Ischemia and Impact on Subsequent Functional Recovery

BACKGROUND Acute increase of serum creatinine (SCr) after partial nephrectomy (PN) is primarily due to parenchymal mass reduction or ischemia; however, only ischemia can impact subsequent functional recovery. OBJECTIVE We evaluate etiologies of acute kidney injury (AKI) after PN and their prognostic significance. DESIGN, SETTING, AND PARTICIPANTS From 2007-2014, 83 solitary kidneys managed with PN had necessary studies for detailed analysis of function and parenchymal mass before/after surgery. AKI was classified by Risk/Injury/Failure/Loss/Endstage classification and defined by either standard criteria (comparison to preoperative SCr) or proposed criteria (comparison to projected postoperative SCr based on parenchymal mass reduction). Subsequent recovery was defined as percent function preserved/percent mass saved. INTERVENTION PN. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS Predictive factors for AKI were evaluated by logistic regression. Relationship between AKI grade and subsequent functional recovery was assessed by linear regression. RESULTS AND LIMITATIONS Median duration warm ischemia (n=39) was 20 min and hypothermia (n=44) was 29 min. Median parenchymal mass reduction was 11%. AKI occurred in 45 patients based on standard criteria and 38 based on proposed criteria, and reflected injury/failure (grade = 2/3) in 23 and 16 patients, respectively. On multivariable analysis, only ischemia time associated with AKI occurrence (p=0.016). Based on the proposed criteria, median recovery from ischemia was 99% in patients without AKI and 95%/90%/88% for patients with grades 1/2/3 AKI, respectively. The coefficient for association between AKI grade based on proposed criteria and subsequent functional recovery was -4.168 (p=0.018). Main limitation is limited patient cohort. CONCLUSIONS Parenchymal mass reduction and ischemia both contribute to acute changes in SCr after PN. Classification of AKI by proposed criteria significantly associates with subsequent functional recovery. However, more robust numbers will be needed to further assess the merits of the proposed criteria. While AKI is associated with suboptimal recovery, even patients with grade 2/3 AKI reached 88-90% of recovery expected. PATIENT SUMMARY Acute decline in function after partial nephrectomy associates with more prolonged ischemia time, and appears to impact subsequent functional recovery. However, most kidneys eventually recover strongly, even if their function is sluggish in the first few days after surgery.

Third Prize: Synchronized Real-Time Ultrasonography and Three-Dimensional Computed Tomography Scan Navigation During Percutaneous Renal Cryoablation in a Porcine Model

AIM To investigate the accuracy of percutaneous cryoablation for kidney tumors performed under combined real-time ultrasonography (US) and three-dimensional (3D) CT scan navigation in a porcine model. MATERIALS AND METHODS After percutaneously injecting 2 to 6 tumor mimic lesions in 11 pigs, a CT scan was performed and digital data were saved into a navigation system (Real-Time Virtual Sonography [RVS]) that allows 3D reconstruction and synchronization with real-time US images. The cryoprobe was guided percutaneously into the kidney tumor mimic, and ice ball formation was monitored continuously during cryoablation using the RVS system. Kidneys were harvested and sent for gross pathologic and histopathologic analysis at days 0, 15, and 30 postoperatively. RESULTS Thirty-five renal tumor mimics were created and treated by percutaneous cryotherapy; tumor mimic locations were as follows: 16 tumors (46%) in the lower pole, 14 (40%) in the central region, and 5 (14%) in the upper pole. Eleven tumor mimics (31%) were intraparenchymal, and 24 (69%) subcapsular. The synchronization between the CT scan 3D reconstructed images and real-time US was successful in all cases. The mean tumor size was 2 cm (range, 1.2-4 cm). Mean cryonecrosis size was 3.3, 3.7, and 2.8 cm at days 0, 15, and 30, respectively. Three (8.5%) positive margins were found on the macroscopic and microscopic analysis. CONCLUSIONS RVS imaging system synchronizing real-time US with preoperative CT scan is a feasible and safe technique for percutaneous probe ablation of kidney tumors.

CT-based Diagnosis of Low Vertebral Bone Mineral Density is Associated with Hypercalciuria and Hypocitraturia on Opportunistic Imaging

INTRODUCTION AND OBJECTIVES Studies have demonstrated associations between nephrolithiasis and systemic conditions, including low bone mineral density (BMD), which may correlate with hypercalciuria in kidney stone formers (KSFs). Traditionally, low BMD is diagnosed with dual-energy X-ray absorptiometry. As a noncontrast CT (NCCT) scan is typically part of a stone evaluation, our objective was to evaluate the association of NCCT-based vertebral BMD with 24-hour urine parameters in KSF. MATERIALS AND METHODS This is a retrospective analysis of 99 KSFs who had CT imaging and 24-hour urine studies. For each patient, BMD was estimated at the L1 vertebral body and CT attenuation measured in HU. A threshold of 160 HU was chosen to distinguish normal from low BMD. Univariate and multivariate logistic regression analysis was performed to compare patients with low and normal BMD. Multivariate linear regression was performed to assess for variables associated with 24-hour urine parameters. RESULTS Patients with low BMD had higher 24-hour urine calcium (219 vs 147 mg/day, p < 0.0001) and larger stone volume (259 vs 78.4 mm3, p = 0.009). Multivariate analysis demonstrated age >60 years (odds ratio [OR] 9.3, p < 0.0001) and hypercalciuria (OR 4.34, p = 0.004) correlated with low BMD. Linear regression demonstrated that lower BMD was associated with higher urinary calcium (β-coefficient -0.268, p = 0.009) and lower urinary citrate (β-coefficient 0.332, p = 0.01). CONCLUSIONS CT-based diagnosis of low mineral bone density is associated with derangement in 24-hour urine calcium and citrate in KSFs, as well as larger stone volumes.