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RENAL Score in Partial Nephrectomy Planning

jst/medics
RENAL scorenephrectomyurology

What the RENAL Score is

The RENAL nephrometry score is a standardized classification system that describes the complexity of a renal mass. Introduced to provide a common language among surgeons, radiologists, and pathologists, it has become a key tool in partial nephrectomy planning.

The acronym R.E.N.A.L. corresponds to five anatomical parameters:

The five parameters

R - Radius

The maximum size of the tumor mass:

  • 1 point: ≤ 4 cm
  • 2 points: > 4 cm and < 7 cm
  • 3 points: ≥ 7 cm

E - Exophytic/Endophytic

The percentage of the mass protruding beyond the renal profile:

  • 1 point: ≥ 50% exophytic
  • 2 points: < 50% exophytic
  • 3 points: entirely endophytic

N - Nearness (to the collecting system)

Distance of the mass from the collecting system or renal sinus:

  • 1 point: ≥ 7 mm
  • 2 points: > 4 mm and < 7 mm
  • 3 points: ≤ 4 mm

A - Anterior/Posterior

Mass position relative to the kidney's coronal plane:

  • a: anterior
  • p: posterior
  • x: cannot be determined

L - Location (relative to polar lines)

Mass position relative to kidney polar lines:

  • 1 point: entirely above or below the polar line
  • 2 points: mass crosses the polar line
  • 3 points: > 50% of the mass crosses the polar line or lies entirely between the polar lines

The suffix h is added if the mass is in contact with the main hilar vessel.

How to interpret it

The total score (sum of R+E+N+L, excluding A) classifies surgical complexity:

| Score | Complexity | | ----- | ---------- | | 4-6 | Low | | 7-9 | Moderate | | 10-12 | High |

The role of 3D models in RENAL Score calculation

Traditional RENAL score evaluation is performed on two-dimensional CT images, with all associated limitations. The E (exophytic/endophytic) and N (nearness to collecting system) components are especially difficult to estimate on axial slices.

PonD3's 3D models make this assessment more intuitive and accurate:

  • The exophytic percentage is immediately visible by rotating the model
  • The distance from the collecting system can be measured directly in 3D space
  • The position relative to polar lines is clear in the model's coronal view
  • The relationship with hilar vessels is visible by toggling individual anatomical layers

A practical example

Take a case with RENAL score 7 (2-1-1-p-3-h):

  • R = 2: mass between 4 and 7 cm
  • E = 1: predominantly exophytic (> 50%)
  • N = 1: far from collecting system (≥ 7 mm)
  • A = p: posterior position
  • L = 3: mass crossing or lying between polar lines
  • h: contact with hilar vessel

On a conventional CT scan, confidently determining the "h" suffix requires careful multi-planar analysis. With a 3D model, it is enough to make renal arteries visible and rotate the model to verify contact.

Conclusions

The RENAL score remains a fundamental tool for communication among specialists and for surgical risk stratification. 3D models do not replace this system, but make it more accessible and reproducible, reducing inter-operator variability in renal mass assessment.