Objective: To investigate the relationship between numerical values obtained using computed tomography (CT) in stone-related urinary obstruction and the duration of obstruction. Study Design: Cross-sectional study. Place and Duration of Study: Department of Urology, Alanya Alaaddin Keykubat University, Turkey, from January 2018 to September 2019. Methodology: Eighty-three patients were investigated. Commencement of obstruction was de ned as time of onset of pain. Cases with less than seven days elapsed between onset of obstruction; and CT were classi ed as acute obstruction; and those with durations of seven days or more as chronic obstruction. Bilateral renal parenchymal and renal fatty tissue densities were measured in three planes. Results: Acute obstruction was present in 53 patients and chronic obstruction in 30. Median renal parenchymal densities in the obstructive and non-obstructive kidneys were 33 and 37 Houns eld unit (HU), respectively; and median perirenal densities were 99 and 108 HU, the di erences being statistically signi cant (p 0.05). Conclusions: A low perirenal density on CT indicated prolonged duration of urinary obstruction.