SIU 2017: Master Class--How To: Optimizing Renal Function Following Surgery for Localized Kidney Cancer - Preoperative Renal Functional Assessment

Lisbon, Portugal (UroToday.com) In this Master Class, organized by Dr. Robert Uzzo, the overarching goal was to help maximize renal function preservation following nephron-sparing surgery for localized kidney cancer. To that effect, there were 4 total speakers focusing on preserving renal function along the management of a patient, from the pre-operative assessment to postoperative management. All panelists agreed that a new baseline is typically achieved 3-6 months postoperatively.

The first speaker was Dr. Volpe, who focused on pre-operative assessment and evaluation. He gave a very nice talk on important considerations from a pre-operative standpoint.

The important factors predicting kidney function preservation include:

  1. Tumor factors
  2. Patient factors
    Baseline renal function
    Patient characteristics
  3. Surgical factors

The Surgical factors are often “modifiable”, but the tumor and patient characteristics are not.

  • Baseline Kidney Function
  • Baseline renal function is the strongest predictor of postoperative renal function
  • Multiple studies have demonstrated its importance
  • Brian Lane paper, J Urol 2011 – Comparing WIT and CIT in NSS
    o Patient baseline renal function was strongest predictor of AKI and chronic renal function outcomes
  • Another paper by Brian Lane and colleagues very nicely demonstrated the difference between medical CKD and surgically induced CKD
    o Patients with baseline medical CKD had higher chanced of 50% postoperative drop in GFR and OS
    o Patients with surgically induced CKD had similar outcomes with patients with no CKD at baseline
For this reason, thorough pre-operative assessment of baseline renal function is very important! For many reasons, including operative planning, patient counseling and NSS intra-operative decision making. But, what is the best way to do so?

1. Creatinine

  • While primarily eliminated through glomerular filtration, about 10% is secreted actively
  • As such, it is NOT a reliable measure of baseline renal function
  • Highly variable with regards to age, sex, gender, body muscle mass, diet, medications

2. Glomerular filtration rate

  • Very reliable measure of baseline renal function – normal is between 90-125 mL/min/1.73 m2
  • Best index of measurement
  • * sCr exceeds upper normal of reference values only when GFR is already below 50!
  • GFR measurement is ideally measured with an agent that is completed filtered but is not secreted or reabsorbed – however, these tests are expensive.
  • Calculated measurement of GFR is a cheaper, relatively accurate way of measuring GFR
  • - Utilize sCr, age, gender and race to help calculate GFR
  • - Traditionally, had been the Cockcroft-Gault equation (1976), then MDRD (1999)
  • - Most recently, the CKD-EPI (2009) is thought to be the most accurate
  • However, for patients older than 70, the BIS1 and BIS2 equations may be most accurate – BIS2 preferred

3. Urinalysis

  • Pre-operative urinalysis has important value
  • Can help identify hematuria (urologic or nephrologic), infection, sediment, and proteinuria

4. Proteinuria and albuminuria

  • Normal values: Proteinuria < 150 mg/24 hrs, albumin <30 mg/24 hrs
  • There are many etiologies for proteinuria, but they warrant evaluation for baseline CKD
  • Albuminuria has become so important, that the recent 2012 consensus on CKD evaluation includes albuminuria as part of the classification, along with GFR
  • Have been associated with survival outcomes
Imaging

1. Contrast-enhanced CT or 3D CT scan

  • While they are important for staging and diagnosis, they should be utilized for other purposes as well
  • Important for identifying vascular anatomy, calcifications, atherosclerosis, urologic abnormalities
  • They can also be used to approximate baseline renal function in recent studies by calculating parenchymal volume
2. Renal scans

  • Mag3 vs. DTPA scans – DTPA preferred, but due to risk of renal injury in patients with CKD, often limited in terms of ability to administer
  • Particularly important in patients with renal asymmetry, but may be useful in predicting postoperative GFR loss
  • Can be valuable in patient counseling, and even in decision making – decision to pursue radical or partial nephrectomy
Again, this was a very nice overview of important preoperative evaluation measures.

Speaker: Alessandro Volpe, Italy

Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, Twitter: @tchandra_uromd at the 37th Congress of Société Internationale d’Urologie - October 19-22, 2017- Lisbon, Portugal
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