Introduction:

Chronic kidney disease (CKD) is a known sequela of renal surgery. The 2017 American Urologic Association (AUA) guidelines mention referral to nephrology for patients at significant risk for development or progression of CKD. Currently, data are limited describing the extent to which at-risk patients are being referred to nephrology pre-operatively and post-operatively. Our objective was to assess rates of nephrology referral amongst patients who had CKD pre-operatively or went on to develop CKD post-operatively, to identify predictors of referral, and to assess the association of nephrology referral with survival.

Methods:

We obtained data from patients included in the SEER-Medicare database for patients ≥65 years of age who received surgery for renal parenchymal cancers and either had a diagnosis of CKD prior to surgery or developed CKD post-operatively between 1999 and 2014 (N=16,007). Referral data were derived from inpatient and outpatient nephrology claims. Patients were classified as follows: 1) having an established nephrologist if they had at least one nephrologist claim from six months or greater prior to their surgery; 2) having a pre-operative referral if they had a nephrology claim within six months prior to their surgery; 3) having an early post-operative referral if the first nephrology claim occurred within 3 months post-operatively; and 4) having a late post-operative referral for any first-time nephrology claims beyond 3 months after surgery. We 1) identified if and when patients were referred to nephrology by CKD disease status and surgery type, 2) used logistic regression to identify patient factors associated with nephrology referral pre- and post-operatively and 3) used a Cox proportional hazard regression model to assess associations between referral and survival. Logistic regression and survival analyses were conducted for patients who had surgery between 2004 and 2014 (N=11,510).

Results:

Of 16,007 patients treated between 1999 and 2004, all of whom had CKD prior to surgery or developed CKD post-operatively, 10.3% had an established nephrologist and 7.2% had a pre-operative referral. See Figure 1 for referrals by CKD status and surgery type. Logistic regression demonstrated CHF (OR:1.2, 95% CI: 1.05-1.46, p=0.011), living in an urban area (OR: 1.4, 95% CI: 1.08-1.84, p=0.008), having a diagnosis of CKD prior to surgery (OR: 3.2, 95% CI: 2.71-3.70, P<0.001), and undergoing partial nephrectomy (OR: 1.63, 95% CI: 1.39-1.92, p<0.001) were associated with a pre-operative nephrology referral. Post-operative referrals by three months were associated with stage 3 disease (OR: 1.35, 95% CI: 1.17-1.55, p<0.001), stage 4 disease (OR: 2.28, 95% CI 1.89-2.78, p<0.001), and moderate to severe liver disease (OR:1.99, 95% CI:1.17-3.34, p<0.001). In an unadjusted model, there was an increased risk of death in patients who had a pre-operative nephrology referral (HR=1.28, p <0.001). However, after adjusting for age, sex, and clinical risk factors, there was no statistically significant survival difference (HR= 1.09, p=0.126). In both an unadjusted (HR= 2.1, p<0.001) and adjusted model (HR= 2.02, p<0.001), there was an increased risk of death in patients with a post-operative nephrology referral by three months. Both the rate of partial nephrectomies (13.5% to 19.3%, p<0.001) and pre-operative nephrology (6.6 to 9.8%, p<0.001) referrals increased over the first and second halves of the study period.

Conclusion:

Few renal cancer patients at risk for CKD progression or development present to the urologist with an established nephrologist. Of patients with preexisting CKD, 41.1% of them do not have an established nephrologist or a referral to see one pre-operatively. Of the patients who present for surgery without CKD and develop CKD post-operatively, 88.4% do not see a nephrologist before surgery, suggesting missed opportunities to refer people at high risk of developing CKD or progression of CKD. Pre-operative nephrology referral did not appear to improve overall survival; however, referred patients may represent a higher risk subset, and other patients who may benefit appear under-referred. Of note, these data predate the 2017 guidelines, which specify clinical signs that may warrant referral.

Funding: This abstract was made possible by the Johns Hopkins Institute for Clinical and Translational Research (ICTR) which is funded in part by Grant Number TL1 TR003100 from the National Center for Advancing Translational Sciences (NCATS) a component of the National Institutes of Health (NIH), and NIH Roadmap for Medical Research. Its contents are solely the responsibility of the authors and do not necessarily represent the official view of the Johns Hopkins ICTR, NCATS or NIH.