Prediction of differential creatinine clearance in chronically obstructed kidneys by non-contrast helical computerized tomography

Abstract

Purpose: We investigate the use of non-contrast helical computerized tomography (NCHCT) in the measurement of differential renal parenchymal volume as a surrogate for differential creatinine clearance (CrCl) for unilateral chronically obstructed kidney.Materials and Methods: Patients with unilateral chronically obstructed kidneys with normal contralateral kidneys were enrolled. Ultrasonography (USG) of the kidneys was first done with the cortical thickness of the site with the most renal substance in the upper pole, mid-kidney, and lower pole of both kidneys were measured, and the mean cortical thickness of each kidney was calculated. NCHCT was subsequently performed for each patient. The CT images were individually reviewed with the area of renal parenchyma measured for each kidney. Then the volume of the slices was summated to give the renal parenchymal volume of both the obstructed and normal kidneys. Finally, a percutaneous nephrostomy (PCN) was inserted to the obstructed kidney, and CrCl of both the obstructed kidney (PCN urine) and the normal side (voided urine) were measured two 2 after the relief of obstruction.Results: From March 1999 to February 2001, thirty patients were enrolled into the study. Ninety percent of them had ureteral calculi. The differential CrCl of the obstructed kidney (%CrCl) was defined as the percentage of CrCl of the obstructed kidney as of the total CrCl, measured 2 weeks after relief of obstruction. The differential renal parenchymal volume of the obstructed kidney (%CTvol) was the percentage of renal parenchymal volume as of the total parenchymal volume. The differential USG cortical thickness of the obstructed kidney (%USGcort) was the percentage of mean cortical thickness as of the total mean cortical thickness. The Pearson's correlation coefficient (r) between %CTvol and %CrCl and that between %USGcort and %CrCl were 0.756 and 0.543 respectively. The regression line was %CrCl = (1.00) x %CTvol -14.27. The %CTvol overestimated the differential creatinine clearance by about 14%, but the correlation is good.Conclusion: The differential renal parenchymal volume measured by NCHCT provided a reasonable prediction of differential creatinine clearance in chronically obstructed kidneys.

Correlation between differential renal function estimation using CT-based functional renal parenchymal volume and 99m Tc - DTPA renal scan

“…in his study compared differential renal parenchymal volume with 24-hr creatinine clearance by percutaneous nephrostomy in obstructed units and found correlation between differential renal function with differential creatinine clearance. [3] Herts et al . in their study proposed that estimated GFR by CT-based parenchymal volume can replace GFR measurement by 125 I-iothalamate clearance imaging after studying 244 renal donors.…”

The Urological Association of Asia clinical guideline for urinary stone disease

“…However, in patients with ureteral stones causing hydronephrosis, there is a concern that the estimated differential function by conventional nuclear scan might not be accurate and requires conjugate views for accurate evaluation Alternatively, more invasive methods include the use of creatinine clearance from urine collected from percutaneous nephrostomy, compared with urine collected from contralateral percutaneous nephrostomy or self‐voided urine (LE:5, GR:C). Carrying out cortical thickness or parenchymal volumetric measurement by using US or NCCT could help provide a reasonable prediction of the differential creatinine clearance in obstructed kidneys …”

“…Carrying out cortical thickness or parenchymal volumetric measurement by using US or NCCT could help provide a reasonable prediction of the differential creatinine clearance in obstructed kidneys (LE:4, GR:C1). 111 Metabolic evaluation CQ 14. Is metabolic evaluation necessary for stone disease patients?…”

Renal parenchyma thickness: a rapid estimation of renal function on computed tomography

“…Computed tomography has become a firstline assessment tool for patients presenting with renal obstruction and has proven to be the most effective modality for diagnosing the etiology of obstruction (7). Not only is CT widely used, it also provides a clear depiction of the renal anatomy and may provide additional valuable and quantifiable clinical information regarding renal function.…”