Unenhanced urinary CT: value of parenchymal attenuation measurements in differentiating acute vs. chronic renal obstruction

Objective

We aimed to search if the renal parenchymal attenuation measurements on unenhanced CT scans could be useful in differentiating acutely obstructed kidneys from chronic cases or unobstructed kidneys.

Material and methods

Unenhanced CT scans of 101 patients were retrospectively reviewed. Thirty-two patients with unilateral acute renal obstruction, 34 patients with unilateral chronic renal obstruction due to various reasons and 35 control subjects were included in the study. The parenchymal densities of both kidneys were measured, from the upper poles, middle portions, and lower poles of each kidney. The mean parenchymal densities of both kidneys were calculated in all three groups of subjects. Secondary signs of renal obstruction such as perinephric stranding, size of ureteral stone, degree of hydronephrosis were also noted for each kidney.

Results

The mean parenchymal attenuation value on the acutely obstructed side was lower than the unobstructed side, 24.21 ± 3.68 and 30.68 ± 4.75 respectively (p < 0.001). The mean parenchymal attenuation value on the acutely obstructed side (24.21 ± 3.68) was lower than both the chronically obstructed side (30.85 ± 4.53), and the control subjects (29.62 ± 3.03 on corresponding side). There was no statistically significant attenuation difference between right and left kidneys in the control group and chronic obstruction group.

Conclusion

Renal parenchymal attenuation measurements and attenuation differences of both kidney of same patient could be useful in differentiating acute unilateral obstruction from chronic cases.