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Original Investigation
December 5, 2018

Association of Prevalence of Benign Pathologic Findings After Partial Nephrectomy With Preoperative Imaging Patterns in the United States From 2007 to 2014

Author Affiliations
  • 1Department of Urology, Stanford University Medical Center, Stanford, California
  • 2Department of Urology, Soonchunhyang University Hospital, Soonchuhyang University Medical College, Seoul, Korea
  • 3Department of Urology and Dermatology, Stanford University Medical Center, Stanford, California
  • 4San Diego School of Medicine, University of California, San Diego
JAMA Surg. Published online December 5, 2018. doi:10.1001/jamasurg.2018.4602
Key Points

Question  How high is the prevalence of benign pathologic findings after partial nephrectomy, and which radiologic modalities are associated with benign findings after partial nephrectomy?

Findings  In this cohort study that included 18 060 patients between 2007 and 2014, overall prevalence of benign pathologic findings after partial nephrectomy was 30.9%, and it was affected by several factors including female sex, old age, and performance of computed tomographic imaging only as preoperative imaging modality.

Meaning  The prevalence of benign pathologic findings after partial nephrectomy is high, and to avoid unnecessary surgeries for renal mass, clinicians have to focus more on possible risk factors, especially radiologic modalities.


Importance  Although the intent of nephron-sparing surgery is to eradicate malignant tumors found on preoperative imaging, benign masses often cannot be differentiated from malignant tumors. However, in the past there have been discrepancies in the reported percentages of benign masses removed by partial nephrectomy (PNx).

Objective  To investigate the annual trend of prevalence of benign pathologic findings after PNx and to investigate what potential factors are associated with this prevalence.

Design, Setting, and Participants  A total of 18 060 patients who underwent PNx between 2007 and 2014 were selected from Truven Health MarketScan Research Databases. We selected those patients who underwent PNx as an inpatient from 2007 and set the surgery date as the index date. Overall, a total of 21 445 patients with International Classification of Diseases, Ninth Revision, Clinical Modification code of 55.4 were identified from 2007 to 2015.

Main Outcomes and Measures  The annual trend of benign pathologic findings was described as an actual number and as a proportion. Univariate and multiple analyses were performed to investigate factors predictive of a benign final pathologic diagnosis, including type of preoperative imaging modality or performance of a renal mass biopsy.

Results  Among the 18 060 patients, mean (SD) age was 57 (12) years, and there were 10637 (58.9%) men and 7423 (41.1%) women. The overall prevalence of benign pathologic findings was 30.9% and the annual trends demonstrated a prevalence of over 30% for nearly every year of the study period. On univariate analysis, the performance of magnetic resonance imaging (MRI) and renal mass biopsy was associated with benign pathologic findings (P = .02 and P < .001, respectively). On multivariable analysis, female sex (odds ratio [OR], 0.62; 95% CI, 0.58-0.66; P < .001), older age (>65 years) (OR, 0.99; 95% CI, 0.99-0.99; P < .001), and computed tomography (CT) only preoperative imaging (OR, 1.16; 95% CI, 1.05-1.28; P = .004) were associated with benign pathologic findings after PNx.

Conclusions and Relevance  We found that the overall prevalence of benign pathologic findings after PNx was higher than the literature suggests, with consistent year-over-year rates exceeding 30%. Female sex, older age (>65 years), and CT only preoperative imaging were predictive of a benign tumor. Further elucidation concerning covariates associated with a benign diagnosis should be the focus of future investigations to identify a cohort of patients who could potentially avoid unnecessary surgical intervention.

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