Renal parenchyma thickness: a rapid estimation of renal function on computed tomography.
OBJECTIVE
To define the relationship between renal parenchyma thickness (RPT) on computed tomography and renal function on nuclear renography in chronically obstructed renal units (ORUs) and to define a minimal thickness ratio associated with adequate function.


METHODS
Twenty-eight consecutive patients undergoing both nuclear renography and CT during a six-month period between 2004 and 2006 were included. All patients that had a diagnosis of unilateral obstruction were included for analysis. RPT was measured in the following manner: The parenchyma thickness at three discrete levels of each kidney was measured using calipers on a CT workstation. The mean of these three measurements was defined as RPT. The renal parenchyma thickness ratio of the ORUs and non-obstructed renal unit (NORUs) was calculated and this was compared to the observed function on Mag-3 lasix Renogram.


RESULTS
A total of 28 patients were evaluated. Mean parenchyma thickness was 1.82 cm and 2.25 cm in the ORUs and NORUs, respectively. The mean relative renal function of ORUs was 39%. Linear regression analysis comparing renogram function to RPT ratio revealed a correlation coefficient of 0.48 (p < 0.001). The linear regression equation was computed as Renal Function = 0.48 + 0.80 * RPT ratio. A thickness ratio of 0.68 correlated with 20% renal function.


CONCLUSIONS
RPT on computed tomography appears to be a powerful predictor of relative renal function in ORUs. Assessment of RPT is a useful and readily available clinical tool for surgical decision making (renal salvage therapy versus nephrectomy) in patients with ORUs.
Kaplon
Daniel M
DM
Department of Surgery, Division of Urology, Section of Minimally Invasive Urologic Surgery, The Warren Alpert School of Medicine of Brown University, Providence, Rhode Island, USA. kaplonda@gmail.com
Lasser
Michael S
MS
Sigman
Mark
M
Haleblian
George E
GE
Pareek
Gyan
G
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D005665:Furosemide; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008875:Middle Aged; D011866:Radioisotope Renography / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods; D014517:Ureteral Obstruction / Q000000981:diagnostic imaging* / Q000473:pathology; D055815:Young Adult
D005665:Furosemide