The Role of Hounsfield Units in Predicting Urinary Stone Composition: A Systematic Review

Abstrak

Background:  Urinary stone disease is a prevalent urological condition with significant morbidity worldwide. Computed tomography (CT) attenuation values, or Hounsfield Units (HU), have been proposed as a tool for estimating stone composition. Objective: To evaluate the accuracy of HU in predicting urinary stone composition and its clinical utility in guiding treatment decisions.Methods: A systematic search was conducted in online databases, including PubMed, Scopus, and Embase, for articles published from 2020 to 2024. Data extracted included study design, sample size, and HU values. The methodological quality of the included studies was assessed using the QUADAS-2 tool, which evaluated the risk of bias. Heterogeneity across studies was assessed using the I² statistic for stone subtypes and for variation in scanner protocols and patient populations.Results: Uric acid stones consistently had the lowest HU values (258–679 HU), whereas calcium oxalate and hydroxyapatite had the highest. Cystine and struvite exhibited overlapping ranges, limiting diagnostic specificity. A combination of HU ≤500 and urine pH ≤5.5 predicted uric acid stones with 87% sensitivity and 83% specificity.Conclusion: HU values correlate significantly with urinary stone composition and serve as a practical predictive tool, though standardization of imaging protocols is needed to improve diagnostic consistency.