RENAL Nephrometry Score

Why Use

Standardizes reporting of renal tumor size, depth, and location. Informs surgical decision-making and effectively compares masses in practice and in the literature. Allows for accurate communication regarding complexity of masses (e.g. when consulting with specialists before images are sent). Validated to predict likelihood of surgical complications, perioperative clinical outcomes, high grade pathology, and case selection (partial versus radical nephrectomy)—see Management for details. The most consistently used and extensively validated score in the urologic literature.

When to Use

Patients with renal mass on cross-sectional imaging (CT or MRI).

Formula

Pearls / Pitfalls

The RENAL Nephrometry Score was developed as a standardized system to objectify reporting of critical anatomical features of a renal mass. Provides a quantifiable and reproducible method to classify renal masses according to anatomic complexity. Stratifies masses into low, medium, and high complexity, with increasing complexity correlating with more aggressive tumor biology, more challenging resectability via nephron sparing surgery, and clinical outcomes. Can be used in preoperative evaluation, planning, and standardized literature reporting. Does not engender specific management strategies. Does not preclude the need to view imaging directly in surgical planning and prior to operation. Tips on assessing individual variables: R: Assess coronal and sagittal views, not just axial. E: Not all masses are symmetrical. Use the most predominant feature in any axis. Measure from where normal parenchymal edge should be if no tumor were present (masses often distort normal renal parenchymal contour). Compare distance from normal parenchymal edge location to most endophytic and most exophytic portions of the tumor. N: Measure from deepest portion of the tumor (in any plane) to renal sinus or collecting system. A: Assess in axial view. Draw a line paralleling renal hilar structures bisecting the kidney (see Facts & Figures ). Assign A if primarily anterior to line, P if primarily posterior. Assign X if mass on tip of poles or otherwise cannot be assigned A or P designation. Apply as suffix (e.g. 10-A). L: Assess in axial view. Polar lines are defined as plane above or below which the medial lip of parenchyma intersects renal sinus fat, vessels, or collecting system (see Facts & Figures ). Renal axial midline is the point halfway between polar lines. H: Apply as suffix (e.g. 10-A-H).

Management

Management of small renal masses: Management strategies typically include: Surgical intervention. Partial nephrectomy (PN). Minimally invasive surgery (MIS) vs. open surgery. Radical nephrectomy (RN). MIS vs. open. Ablative intervention. Cryoablation. Radiofrequency ablation. Active surveillance (structured expectant management) Impact of RENAL score on surgical decision-making: PN vs. RN: Higher complexity score more likely to undergo RN. MIS vs. open: High complexity scores more likely to undergo open surgical approaches. Active surveillance vs. intervention: High complexity score more likely to undergo surgical intervention.

Critical Actions

Not to be used with ultrasound imaging—requires cross-sectional imaging (i.e., CT or MRI).

Advice

Consider competing risks of morbidity and mortality, oncologic prognosis, and patient preference to inform decision-making and to risk-stratify management strategies.

More Information

RENAL Nephrometry Score Complexity Complication Rate* 4–6 Low 6.4% 7–9 Intermediate 11.1% 10–12 High 21.9% *Major complications as defined by Clavien-Dindo classification 3–5 (requiring intervention, requiring ICU admission, or death), from Simhan 2011 . Figure 1. Scoring of L component. Polar lines (solid lines) and axial renal midline (broken line) are depicted on each sagittal view of kidney. Numbers 1 to 3 represent points attributed to each category of tumor. Figure 2. Scoring of E component. Broken line demonstrates how expected renal contour is estimated. Figure 3. A, scoring of L component, determined in relation to upper or lower polar line. B, polar lines defined as portion of kidney where concentric rim of renal parenchyma is interrupted by renal hilar vessels, pelvis or fat on axial imaging. Axial cut is shown between polar lines, and medial renal parenchyma is interrupted by sinus fat and renal vessels. Line drawn over right kidney divides kidney into anterior and posterior components. C, axial cut is shown below lower polar line and concentric rim of renal parenchyma in both kidneys surrounds sinus fat. Line drawn to divide kidney for anterior and posterior designations. Figures from Kutikov 2009 .