first developed by Kutikov and Uzzo in 2009,
is an acronym that encompasses 5 major anatomic considerations which determine surgical complexity associated with Nephron Sparing Surgery:
diameter in cm) is an obvious choice and illustrates the size of the tumor measured in cm at its widest diameter,
with categories dividing tumors smaller than 4cm,
between 4 and 7cm and over 7cm into 1,
2 or 3 points respectively (Fig.
Some studies show this to be the parameter with higher interobserver consistency and also more recent studies evaluating for the use of this score in thermal ablation of kidney tumors have also found it to be the strongest indicator of risk of relapse post-ablation.
“E”xophytic/Endophytic growth is the second parameter,
and is measured by imagining a virtual contour of the kidney as one would expect to find had no tumor been present.
Growth beyond that virtual contour is considered exophytic growth and tumor within that virtual contour is considered endophytic growth.
the more exophytic a tumor the more accessible it will be to surgical tumorectomy and therefore tumors demonstrating predominantly exophytic growth (>50%) are assigned 1 point,
predominantly but not entirely endophytic tumors (<50%) are assigned 2 points and completely endophytic tumors get 3 points (Fig.
“N”earness to the collector system is measured as the nearest distance in mm between discernable tumor mass and the renal sinus,
and should be assessed in excretory phase for easiest discrimination of the renal chalices.
Tumors spaced more than 7mm away from the renal sinus are attributed 1 point,
between 7 and 4mm are scored for 2 points and less than 4mm contribute with 3 points (Fig.
“A”nterior/Posterior location within the kidney as,
determined in the axial plane by a strict visceral oriented coronal midline,
is the only major “letter” with no numerical score,
instead being qualified by the letter “a” if predominantly ventral to that line,
“p” if predominantly dorsal to that line or the letter “x” if located straight on top of the midline (Fig.
“L”ocation in relation to the polar lines,
as determined (preferably) on a strict visceral oriented coronal plane from the upper and lower limits of the hilar pedicle,
accounts for 1 point if the mass is entirely above or below the polar line,
2 points if the mass crosses the polar line (less than 50% of the tumor) without transgression of the axial midline or 3 points if more than 50% across the polar line or if it crosses beyond the axial midline (Fig.
One final suffix,
the letter “h” (hilar abutment) should be attributed in cases of clear contact of the mass with the renal vein or artery,
though it does not carry with it a numerical score.
From evaluation of these simple parameters we then derive a score between a minimum of 4 points to a maximum of 12 points where tumors with a nephrometry score of 4 to 6 points are graded as low complexity lesions,
7 to 9 points as moderate complexity lesions and 10 to 12 points as high complexity lesions,
to be expressed in the following manner:
R + E + N + a/p/x + L (+-h) = Total a/p/x (+-h)
Or for a practical example: 1+3+3+a+3h = 10ah describing the case of a Renal Cell Carcinoma with less than 4cm,
predominantly endophytic spaced less than 4mm from the renal sinus located in the ventral half of the kidney predominantly contained between both polar lines and abutting either the renal vein or artery.
Thus it is easy to see just how much useful information is contained within a small score,
and how even a small tumor may present serious surgical complexity and probably preclude possibility of partial nephrectomy.
Early as it may be for studies of this nature,
recent literature has suggested correlation of the RENAL score with post-operative complication rate,
relapse and other relevant outcomes.
To illustrate application of this score,
we can observe a case from our institution in Fig.
7 and 8 portraying a rather nasty case of Renal Cell Carcinoma with a mass measuring 7,3cm of maximum diameter,
with predominantely (but not entirely) endophytic growth,
invading the renal sinus as exquisitely demonstrated on excretory phase scans,
predominantely anterior and clearly crossing over both inferior polar line and midline on coronal CT slice,
abutting renal venous and arterial vessels and amounting for a score of 3+2+3+a+3 h = 11 ah – this is a high complexity renal mass.
On the other end of the spectrum we have another case from our institution on Fig 9 and 10 of a small (~3,5cm),
partially exophytic (though under 50%) anterior renal mass with more than 7mm from the renal sinus,
entirely contained below the inferior polar line with no contact with renal artery or vein,
amounting to a score of 1+2+1+a+1 = 5a – this is a low complexity renal mass,
successfully submitted to partial nephrectomy.