Journal club- Split renal function in patients with renal masses - utility of parenchymal volume analysis Vs nuclear renal scans

Journal club- Split renal function in patients with renal masses - utility of parenchymal volume analysis Vs nuclear renal scans

1. Journal Club Dr Santosh K Senior Resident All India Institute of Medical Sciences , Bhubaneshwar

2. Background Surgical treatment – Gold standard for operable renal masses Radical Nephrectomy – used to be the gold standard for all renal operable renal tumours RN has fallen out of favor for small renal tumors Nephrectomy predisposes to CKD

3. 662 patients with a solitary tumor, a normal opposite kidney, and a “normal” serum creatinine level-considered for elective PN   26% of patients had preexisting CKD (GFR <60 mL/min/1.73 m  2  ) CKD was much more common after RN than PN: 65% versus 20%, respectively (  P  < 0.001) Potential negative implications of CKD- Need for PN in small renal tumours

4. AUA guideline statements PN is preferred for small renal masses (stage T1a, <4.0 cm) whenever feasible PN - whenever preservation of renal function is potentially important preexisting CKD proteinuria abnormal contralateral kidney multifocal or familial RCC

5. Split renal function- why is it important Gives relative function of each kidney separately Crucial for decision making( for bigger masses)- Partial vs Radical Helps in prognostication about post operative renal function Compensatory hypertrophy of about 20-25%

6. SRF- traditionally obtained by nuclear renal scan (NRS) Exposure to radioactive isotopes Increases the cost Suboptimal interpretation reproducibility Renal transplant donors –SRF estimated from Parenchymal volume analysis (standard of care) Analysis of SRF by PVA - more accurate Barbas AS, Li Y, Zair M et al. CT volumetry is superior to nuclear renography for prediction of residual kidney function in living donors. Clin Transplant. 2016; 30: 1028-35.

7. Donors are young and healthy- renal function is likely to correlate more directly with parenchymal volume Kidney cancer patients are substantially different than the kidney transplant donor population

8. OBJECTIVE To evaluate the utility of PVA for estimation of SRF in kidney cancer population To evaluate relationships between function saved and mass saved by PN

9. Patients and Methods Reviewed 2441 patients undergoing Radical/Partial nephrectomy from 2010-2018

10. Parenchymal Volume Analysis Preoperative and postoperative ipsilateral parenchymal(RN) - free-hand scripting Contralateral parenchymal volumes were measured semi-automatically by 3-D volume calculating software (Aquarius iNtuition version 4.4.6, TeraRecon Inc., San Francisco CA) The collecting system, vessels, cysts, sinus fat and tumor were excluded from all parenchymal volume measurements

11. In 92 cases - measurement by both techniques for direct comparison For PN patients, Ipsilateral split renal function (SRF) Global GFR by MDRD formula x (parenchymal volume analysis (PVA)) % contribution of ipsilateral kidney to total volume For RN patients volume contribution by contralateral kidney was used

12. Statistics Equivalent or superior model compared to nuclear renal scan (NRS) Continuous and categorical variables were presented as medians (interquartile range; IQR) and numbers (%) Continuous were compared using Mann-Whitney U test Relationships between variables - Pearson correlation concordance between different methods of estimation -Bland-Altman plot Correlation coefficients (r) Strong 0.5-0.8 Modest 0.2-0.5 Analysis software- IBM-SPSS Statistics®, version 25 (IBM-Corp., Armonk, NY) Medcalc , version 18.0 ( Medcalc Software, Ostend, Belgium)

13. Results Baseline characteristics

14. Parenchymal Volume Analysis and GFR estimation

15. Split Renal Function and Functional Outcomes

16. Relationship between Function and Mass Saved after Surgery-PN

17. Relationship between Function and Mass Saved after Surgery-RN

18. Comparison of renal parenchymal volume estimates: software analysis versus free hand scripting

19. Strengths of study patients are representative for PN and RN for most tertiary care centers Large cohort comprehensive analysis of functional outcomes

20. Limitations Retrospective analysis of those patients who required these studies- Many were excluded- selection bias? heterogeneous with a mix of warm/cold ischemia open or minimally invasive approaches

21. Conclusion Split renal function estimation from PVA correlates strongly with that estimated by NRS Additional NRS may be omitted

22. Take home message Split renal function influences clinical management and helps in prognostication NRS though are regularly used , Information from newer studies may change the practice soon

23. 69-year-old man who recently presented with a 5.6 cm left renal mass R.E.N.A.L. score of 10 normal contralateral kidney on imaging PN appeared to be feasible Preoperative eGFR was 70 ml/min/1.73m2 SRF - 58% in the contralateral kidney, preoperative eGFR -of 41 ml/min/1.73m2 Compensatory hypertrophy of 20-25%, the final global GFR would be 49-51 ml/min/1.73m2 (RN)