The Renal Tumor Contact Surface Area (CSA) is one feature of the renal tumor's relationship with the patient.
Patient selection: renal tumor
Assumption: tumor is spherical
Parameters:
(1) diameter of the renal tumor in cm
(2) diameter of the tumor at the level of the renal capsule in cm
(3) depth of the tumor invasion into the kidney in cm
There are several methods to calculate the surface area of the spherical segment shared with the kidney:
(1) calculate the spherical surface area, then determine the percentage of the tumor that is intra-parenchymal
(2) calculate the surface area of the spherical segment directly
surface area of sphere in square cm =
= 4 *PI() * ((radius of sphere)^2)
fraction of tumor within the kidney =
= (cross sectional area within kidney) / (total cross-sectional area)
area of segment by method 1 =
= (surface area of sphere) * (fraction of tumor within kidney)
area of segment by method 2 =
= PI() * (((radius at level of renal capsule)^2) + ((depth of tumor invasion)^2))
Interpretation:
• The CSA corelates with surgical complexity, especially for partial nephrectomy.
• The CSA is associated with prognosis, both operative and survival.
