DETERMINATION OF URINARY STONES CHEMICAL COMPOSITION BY COMPUTED TOMOGRAPHY DENSITY

Abstract

Objectives: To assess the role of Computed Tomography (CT) in identify the chemical
composition of urinary stone according to Hounsfield Units (HU) value and to assess the
accuracy of CT in determination the chemical composition of urinary stone in comparison with
chemical stone analysis and urine examination.
Background: Renal stone is one of the most common causes of acute abdomen pain. There are
many types of renal stones depending on stone chemical components those including calcium
oxalate stone, calcium phosphate, struvite stone, uric acid stone and cystine stone. CT are more
valuable diagnostic imaging modalities in describing and evaluating the renal stone site, size and
density in HU.
Patients and methods: A total of 80 patients were examined, their age was ranged from 20 to 79
year. All patients were examined with Computerized Tomography of Kidney, Ureter and Bladder
(CT KUB) examinations to identify renal stone density. Laboratory tests of urine to identify type
of stone depended on PH level test and crystals appearance in microscopic urine examination.
Results: According to the stone densities those determined by CT, the renal stones were divided
into three groups, the first group; low density such uric acid stone their densities range 200-450
HU, the second group: medium density such cystine stone, struvite stone and mixed (calcium
oxalate and uric acid) stone their densities range 450-600 HU and the third group: high density
such calcium stone (oxalate or phosphate) their densities range 600-1700 HU.
According to PH of urine analysis, the renal stones were divided into two groups, PH of uric acid
stones and cystine stone was less than 6, PH of calcium oxalate stones, struvite stones and
calcium phosphate stones was more than 6.
Conclusion: All urinary calculi examined were clearly visible on CT regardless of chemical
type. We found the chemical composition of urinary calculi can be accurately predicted by CT
using the HU parameters. HU parameter in computerized tomography can distinguish uric acid
stones from calcium oxalate stones with high accuracy.