New Baseline Renal Function after Nephrectomy

• 24 May 2021 10:43:44 AM
• |Onco Urology

Dear All,

From the time PN became the method of choice wherever or whenever possible for RCC, considerable studies have been generated on how to evaluate the postop outcomes of both PN and RN, preoperatively. Renal Insufficiency following PN/RN has been Challenging to predict but is important in Surgical planning and Counselling.

There are several Published Models comparing how to Predict Functional Outcomes after PN or RN.

I am providing a list of such studies available in the article of Diego Aguilar Palacios* et al (2021, J Urology, 205 (5 May): 1310) (PDF provided).

The primary objective of this study was to develop a simple and accurate predictive model for estimating the new baseline glomerular filtration rate (NB-GFR) after partial nephrectomy (PN) or radical nephrectomy (RN). Previous studies have shown that a threshold of NB-GFR after surgery of about 45 mL/min/1.73 m² has implications with respect to long-term survival. The AUA guidelines now recommend consideration for RN whenever increased oncologic potential is suspected based on tumour size, renal mass biopsy (if obtained), or imaging features. In this setting, RN is preferred if all of the following criteria are also met: 1) high tumour complexity; 2) no preexisting CKD/proteinuria; and 3) a normal contralateral kidney that will likely provide NB-GFR >45 mL/min/1.73 m² even if RN is performed. The study provides an equation to predict NB-GFR that is based on preoperative GFR, the procedure performed (PN or RN), age, tumour size, and the presence/absence of diabetes. The performance characteristics are strong, with a correlation index of 0.82, and the data are validated in an independent cohort. Furthermore, the area under the curve for prediction of an NB-GFR threshold of 45 mL/min/1.73 m² was also encouraging (0.90).

This Formula was New baseline GFR = 35 + Preop GFR (x 0.65) – 18 (if Radical Nephrectomy) – Age (x 0.25) + 3 (if Tumour Size >7cm) – 2 (if Diabetic).

The ROC Curve that evaluated the ability of the equation to discriminate Postop GFR 45mL/minute/1.73m2 were 0.90 for both Internal and external validation sets.

This new Predictive Model introduced which has been Internally and Externally validated could provide us a more accurate prediction for planning surgical options and Post op outcomes Preoperatively. Is it time for us to change to this new proposal?

With warm Regards,

Venu

Comments(2)

• 

  Dr G G Laxman Prabhu

  24 May 2021 09:02:17 PM

  It is an interesting read which has appeared in the May issue of J of Urology 2021

  
  

  Let me place two case scenarios before the readers:

  1.A large renal mass 10 CMS plus on one side and a contracted contralateral kidney, with normal creatinine

  2. A small renal mass with a contralateral kidney of normal dimensions with normal creatinine.

  The first one needs RN and PN will suffice in the second instance. The clinician will counsel the patient on the need for CKD treatment in the first instance and just a follow up in the second instance. This I am sure is the approach most clinicians adopt.

  The formula suggested in the article is not only of utility in preoperatively working out what would be the GFR post surgery which in turn is reassuring when normal and of progostication potential when abnormal but also of use while auditing impact of intervention in the long run. Surgical technique and surgically induced ATN will also impact the post operative GFR. This would depend on expertise of individual surgeon.

  A practical point as I sign off. Beware of atherosclerotic signs in the aorta and it's branches.  If found on CT scan of patients undergoing RN/PN, then significant deterioration in GFR can be anticipated.

  GG LAXMAN PRABHU

  
  

  
  

  
  

  
  

  
  

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  Dr. Roy Chally

  26 May 2021 04:50:17 PM

  Though better, the practical utility of this tool is limited. 

  1. There is going to be a reduction in glomerular mass  mass after surgery. A fall in GFR is inevitable. Is degree of fall with normal S.creatinine  clinically relevant. 

  2. In counselling we tell the patient whether he can expect a fall in S.Creatinine from normal after surgery. Is the table needed for this prediction. Other parameter should be adequate for this prediction. 

  3. Is the degree of fall in GFR over 60 ml/ minute clinically relevant. 

  4. In patients presenting with raised S. Creatinine, we can expect this to go up further after surgery. Treatment is not going to differ on GFR value

  5 In dealing with mass in solitary functioning kidney with normal and raised S. Creatinine values we always talk of the need for dialysis support. Expertise of the surgeon is crucial here. This table is not of much help. 

  6. All will have a fall in GFR after surgery. This table is not going to help us in predicting how many will need dialysis support in future. Knowing the likely GFR at the end of 1year alone is not clinically relevant.