Application of RENAL Nephrometry Score to Distinguish Malignant and Nonmalignant Pediatric Renal Masses
Arthi Hannallah, MD, Zoë Baker, PhD, MPH, Mika Warren, MD, Andy Chang MD, MD.
Children's Hospital Los Angeles, Los Angeles, CA, USA.
BACKGROUND: Nephron sparing surgery (NSS), when feasible, is considered the standard of care for unilateral renal masses in adults, but not necessarily in pediatric patients. We applied the validated RENAL nephrometry score to a pediatric cohort to determine whether the RENAL criteria can aid both in determining renal masses that can undergo NSS and in characterizing malignant and non-malignant final pathology for presumed renal masses.
METHODS: This was a retrospective review of pediatric patients with suspected renal malignancies from 2003-2021. Images were evaluated by RENAL nephrometry scoring criteria. The RENAL nephrometry score is a standardized system to report anatomic characteristics of a mass. The score provides a value and percent risk of complications should NSS be pursued. The images were reviewed to determine feasibility for NSS by clinician judgement, with 15% of the cohort reviewed by two providers for interrater reliability. T-tests and Fisher’s Exact tests were used to determine whether RENAL scores varied between malignant or non-malignant masses, and between patients deemed feasible or not feasible to undergo NSS.
RESULTS: Among the 158 patients with presumed renal malignancies, 148 (93.7%) patients with 149 renal units met inclusion criteria. Approximately half of the patients were Hispanic, and two-thirds had a public health insurance plan (Table 1). Ten (6.7%) masses were non-malignant, while 139 (93.3%) were malignant (Figure 1). Mean mass diameter at largest dimension for malignant lesions was 10.7cm (±3.8), which was significantly larger than mean mass diameter for non-malignant lesions (5.5cm ±2.9, p<0.001, Table 2). The mean RENAL score for malignant lesions was 10.3 (±1.2), while the mean RENAL score for non-malignant lesions was 9.0 (±1.5), which was significantly different (p=0.001). Nine masses were determined to be amenable for NSS, including five malignant lesions (3.4%) and four non-malignant lesions (40.0%; p<0.001). Among lesions amenable for NSS, the odds of a non-malignant finding were 19.2 times greater than the odds of a malignant finding (95% CI: 4.1-90.3; p<0.001). The mean RENAL score for masses amenable for NSS was 7.3 (±1.7), which was statistically significantly lower than the RENAL score for masses that could not undergo NSS (10.4 ±1.0, p<0.001).
CONCLUSIONS: The proportion of pathology specimens from surgical intervention performed for presumed renal malignancy with a final non-malignant pathology in this cohort was almost 7%, and ability to undergo NSS was associated with significantly increased odds of a non-malignant finding. The RENAL scoring may be used as an adjunct to evaluation of pediatric renal masses, as low scoring masses are more likely to be non-malignant tumors and NSS can be considered. 
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