Precise Renal Function Testing Helps Post-Nephrectomy Management

By Sevag Demirjian, MD

Large-scale epidemiologic studies have shown that chronic kidney disease is an important risk factor for adverse clinical outcomes. The latter includes not only progression to end-stage renal disease but a significant increase in cardiovascular events and all-cause mortality.

Chronic kidney disease initiation and progression have traditionally been confined to those with chronic medical conditions such as diabetes mellitus and hypertension. However, there is a significant and rising incidence of kidney disease that develops among those who sustain loss in functioning nephron mass due to acute kidney injury. This is self-evident in an aging population with multiple comorbidities who undergo major cardiovascular surgeries, and among those who undergo nephrectomy of renal cell cancer, often driven by the increasing number of detected incidental renal masses.

Patients presenting with renal cancer are not analogous to kidney transplant donors who are proven to have a clean bill of health after going through extensive evaluation that ensures their long-term outcome. Subsequently, it isn’t surprising that accurate measurement of renal function plays a critical role in counseling and informing patients and physicians alike regarding long-term renal outcomes following nephrectomy procedures.

Evaluating Renal Function

The gold standard for accurate assessment of renal function is the direct measurement of compounds that are filtered and not secreted or absorbed in the kidneys, such as inulin or iothalamate. However, these tests are available only in select academic medical centers and require significant cost, time and expertise to perform.

We evaluated the performance of existing estimation equations such as Cockcroft-Gault, Modification of Diet in Renal Disease, and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) versus measured glomerular filtration rate using iothalamate. CKD-EPI marginally outperformed the other equations and fared significantly better than serum creatinine alone in patients with renal cancer undergoing nephrectomy; however, it lacked precision when compared with direct measurement with iothalamate.

The widespread use of creatinine-based estimation equations of renal function has increased awareness among physicians and the public about kidney disease prevalence and its clinical implications. The relationship between chronic kidney disease and adverse clinical outcomes is robust, but outcome prediction can be improved by incorporating proteinuria, which has proven its prognostic value in numerous well-performed studies.

We have all seen patients who, although they have a similar baseline renal function, progress to advanced renal disease at different rates. For example, in a cohort of 920,985 adults receiving community-based care in Canada, the risks of mortality, myocardial infarction and progression to kidney failure associated with a given level of eGFR independently increased in patients with higher levels of proteinuria.

At Cleveland Clinic, we have established a longitudinal multidisciplinary clinic for patients with kidney cancer. We use combined surgical and medical approaches in striving to cure cancer while preserving long-term renal function and overall survival by optimizing perioperative and follow-up care.

Dr. Demirjian is a staff member of the Department of Nephrology and Hypertension in Cleveland Clinic’s Glickman Urological & Kidney Institute.