What Is RENAL Nephrometry Score?
RENAL nephrometry score is a reproducible classification system used to assess the anatomical features of renal (kidney) tumors and standardize the assessment criteria. The assessment system is developed based on the five different reproducible characteristic features that highlight the anatomy of a solid kidney mass. The classification system was developed by the researchers Kutikov and Uzzo.
The RENAL (radius of the tumor mass, exophytic or endophytic growth properties, proximity of the tumor to the collecting duct or sinus in millimeters, anterior or posterior location in terms of polar lines) nephrometry scoring classification system was later introduced as a reproducible objective system to highlight the salient features of the renal (kidney) tumor anatomy.
What Is the Purpose of the RENAL Nephrometry Scoring System?
Based on cross-sectional image findings, the scoring system was typically developed to categorize kidney tumor masses into low, intermediate, and high complexity. Its purpose is to aid decision-making, counseling of the patient, surgical planning by the doctor, patient follow-up post-surgery, and academic reporting of renal tumors.
What Is the RENAL Nephrometry Classification?
The scoring is developed depending on the five basic salient features of the renal tumor mass. RENAL is an easy and simple-to-remember acronym for the five radiological features that are scored as follows:
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Radius (Maximum Diameter) In Centimeters (CM) In Any Axis:
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⩽4: 1 point.
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>4 but <7: 2 points.
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⩾7: 3 points.
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The “R” descriptor denotes the maximum diameter of the mass. For example, a radius of 4 centimeters was considered the maximum size in dimensions for partial nephrectomy until recently. Lesions that are less than or equal to four centimeters (≤ 4 cm) are assigned 1 point, those less than four but greater than seven centimeters (> 4 but < 7 cm) are assigned 2 points, and those that are greater than or equal to seven centimeters ( ≥ 7 cm) are assigned 3 points.
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Exophytic or Endophytic Tumor Location:
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⩾50% exophytic: 1 point.
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<50% exophytic: 2 points.
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100% endophytic: 3 points.
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The “E” descriptor signifies the exophytic or endophytic location of the tumor mass. Tumor lesions, predominantly endophytic, pose a greater surgical threat than exophytic ones. Lesions projecting more than 50 % outside the cortex of the kidneys are assigned 1 point, lesions less than 50 % are assigned 2 points, and tumor lesions that are completely endophytic are assigned 3 points.
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Near Proximity to the Renal Collecting Duct System or Renal Sinus:
It is measured in millimeters as the shortest distance from the lowest point of the tumor mass.
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⩾7: 1 point.
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>4 but <7: 2 points.
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⩽4: 3 points.
The “N” descriptor highlights the nearest proximity to the collecting duct system measured in millimeters (mm). It is best determined on excretory images. Tumors are subdivided into three categories:
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Tumors seven millimeters or greater from the collecting duct system or renal sinus are assigned 1 point.
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Tumors greater than four but lesser than 7 millimeters are assigned 2 points.
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Tumors four millimeters or less from the central duct collecting system are assigned 3 points.
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Anterior or Posterior Location:
It is assessed on axial imaging. The “A” descriptor denotes the anterior or posterior location of the tumor. No point value is assigned to it. For example, if the tumor typically lies on the kidney’s ventral surface, the anterior (a) descriptor is denoted. Tumors on the dorsal surface of the kidney are denoted as posterior (p). However, tumors that do not fall into these categories are designated “x.”
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Descriptors: “a” (anterior), “p” (posterior), or “x” (neither).
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Location Relative to the Renal Poles:
The “L” descriptor denotes the tumor location concerning the polar renal lines.
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A tumor entirely below the inferior pole or above the superior pole is assigned 1 point.
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If the tumor mass crosses the polar line, it is designated by 2 points.
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If more than 50 % of the tumor mass lies across the polar line or is entirely within the polar lines, it is denoted by 3 points.
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The h suffix is designated if the tumor mass touches the primary renal artery or renal vein.
What Is the RENAL Nephrometry Score Grading?
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A score of 4-6: low complexity renal tumor.
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A score of 7-9: moderate complexity renal tumor.
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A score of 10-12: high complexity renal tumor.
When Is the RENAL Nephrometry Score Used?
Patients having renal tumor mass can benefit from the RENAL Nephrometry score in determining the treatment. The score quantifies the typical features of renal tumor mass anatomy objectively and reproducibly. The scoring system standardizes the diagnosis of kidney tumor masses and effectively stratifies the type of treatment that should be given. Therefore, it has tried to objectify the subjective measures in the treatment part. Hence, it is especially useful in patients with renal tumors to aid doctors in determining the best treatment modality.
What Are the Benefits of the RENAL Nephrometry Score System?
The system was developed to objectively standardize the crucial nephrometry scoring anatomical features of the kidney tumor mass. It provides the following benefits:
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Provides a simple, reproducible method for classifying renal tumor masses according to the complexity of the anatomical features.
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Helps to stratify the renal tumor masses into low, medium, and high-complexity tumors. The higher the complexity of the tumor mass, the poorer the prognosis with invasive biological tumor behavior and challenging surgery and clinical outcomes.
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The grading system can be used to evaluate, plan, and standardize medical literature reporting preoperatively by the surgeon.
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Does not prevent the requirement of viewing the imaging before surgical operation.
Conclusion
To conclude, the RENAL nephrometry scoring system is an easy and simple methodology to stratify complex renal tumors based on their grading. The system helps the surgeon plan the treatment, decision-making, and patient counseling and provides a standardized platform for academic medical reporting. The RENAL nephrometry score correlates with long-term clinical outcomes and prognosis. However, the grading system does not include kidney abnormalities that may contribute to surgical morbidities, such as fusion or duplication. The radiologists that interpret the data will find the nephrometry scoring system simple. Also, the salient features of a renal tumor are reported for surgical planning.
