Role of Dual Energy CT Scan in Evaluation of the Chemical Composition of Renal Stones

Abstract

ABSTRACT Introduction: For appropriate management of renal stone knowing its composition is important. Laboratory chemical analysis of the stones involves sophisticated techniques. Dual Energy Computed Tomography (DECT) has emerged as a viable option that can be helpful in determining the composition of urinary stones with precision. Aim: To determine the composition of renal stones with DECT. Materials and Methods: Patient aged 20-70 years, diagnosed for renal calculi and scheduled to undergo surgical extraction of stones were included in the study from November 2016 to May 2018. After the characterisation of the calculus via DECT, surgical extraction was done. The chemical composition of the stones was determined by laboratory analysis and was compared with the findings of DECT. The statistical analysis was done using Statistical Package for Social Sciences (SPSS) Version 21.0. P<0.05 was taken as significant. Results: A total of 100 patients with mean age of 41.15±10.08 years were analysed in the study. Majority of cases (55%) had stone size in 6-10 mm range and the mean stone size was 10.15±6.36 mm. Mean number of stones was 4.17±1.55 with maximum subjects having multiple stones (96%). According to chemical analysis, most common renal stone was hydroxyapatite (32%) followed by cystine (30%), uric acid (28%), mixed stones (7%) and oxalic acid (3%), respectively. DECT showed that maximum number of stones were hydroxyapatite (36%) followed by cystine (34%) and uric acid (30%), respectively. DECT did not identify any stone as oxalic acid or mixed type. The level of agreement between DECT and chemical analysis was excellent for uric acid (K=0.951); cystine (K=0.908) and hydroxyapatite stones (K=0.889). Conclusion: Barring the mixed stones and oxalic acid stones, DECT characterisation of the chemical composition of the renal stones (uric acid, cystine and hydroxyapatite) was excellent. The high precision of DECT can better help in determining the management plan for renal stones and reduce the unnecessary burden of surgical intervention.

Keywords

• cystine
• hydroxyapatite
• kidney stone
• uric acid
• urinary