title: Contemporary Accuracy of Digital Abdominal X-Ray for Follow-Up of Pure Calcium Urolithiasis: Is There Still a Role?
abstract: Radiological imaging remains the cornerstone of follow-up of patients with urolithiasis. Plain abdominal X-ray (XRKUB) of these patients is largely becoming obsolete in favor of noncontrast computed tomography of the abdomen and pelvis (CTKUB), which offers superior sensitivity and specificity. Contentiousness exists, however, related to the radiation doses associated with CT. Calcium oxalate remains the most common stone composition across most populations. These calculi are radiopaque and thus follow-up with XRKUB may be appropriate in some settings, avoiding the higher radiation doses associated with standard protocol CT. With the emergence of low-dose CT, however, and the modest accuracy of XRKUB, the ongoing role for XRKUB in the management of urolithiasis is debatable. In this study, we assessed the proportion of pure calcium urolithiasis visible on XRKUB to assess the utility of XRKUB for follow-up of pure calcium urolithiasis. Hospital laboratory databases were analysed to identify patients who had undergone urological intervention and extraction of urolithiasis composed of pure calcium salts, who had undergone CTKUB and XRKUB during the same episode for diagnosis of the calculus. One hundred five calculi were included and the imaging for each patient analyzed. 79/105 calculi (75%) identified on CT were visible on XRKUB. The median calculus visible on XRKUB was 7.0 mm (interquartile range [IQR] 5.0-10.0 mm), the median calculus not seen was 4.25 mm (IQR 3.5-7.0 mm) as measured on CT (p < 0.01). XRKUB accuracy varied according to calculus position within the renal tract. Calculi were most often visible in the renal pelvis and proximal ureter (86%), 50% of mid-ureteral and 72% of distal ureteral calculi were visible (p = 0.01). Until low-dose CT protocols become widely adopted, XRKUB still has a limited role in the management of pure calcium urolithiasis in selected patients. Due to its modest accuracy in many settings, this role is limited mainly to larger proximal urolithiasis.
authors.affiliation: 1 Department of Urology, Austin Hospital , Heidelberg, Victoria, Australia .|2 Department of Surgery, University of Melbourne , Victoria, Australia .
authors.forename: Dermot
authors.initials: D
authors.lastname: O'Kane
authors.affiliation: 1 Department of Urology, Austin Hospital , Heidelberg, Victoria, Australia .
authors.forename: Nathan
authors.initials: N
authors.lastname: Papa
authors.affiliation: 1 Department of Urology, Austin Hospital , Heidelberg, Victoria, Australia .|2 Department of Surgery, University of Melbourne , Victoria, Australia .
authors.forename: Todd
authors.initials: T
authors.lastname: Manning
authors.affiliation: 3 School of Medicine, Griffith University , Southport, Queensland, Australia .
authors.forename: Jonathan
authors.initials: J
authors.lastname: Quinn
authors.affiliation: 3 School of Medicine, Griffith University , Southport, Queensland, Australia .
authors.forename: Alice
authors.initials: A
authors.lastname: Hawes
authors.affiliation: 4 Department of Urology, Gold Coast University Hospital , Southport, Queensland, Australia .
authors.forename: Neil
authors.initials: N
authors.lastname: Smith
authors.affiliation: 4 Department of Urology, Gold Coast University Hospital , Southport, Queensland, Australia .
authors.forename: Scott
authors.initials: S
authors.lastname: McClintock
authors.affiliation: 1 Department of Urology, Austin Hospital , Heidelberg, Victoria, Australia .|2 Department of Surgery, University of Melbourne , Victoria, Australia .
authors.forename: Nathan
authors.initials: N
authors.lastname: Lawrentschuk
authors.affiliation: 1 Department of Urology, Austin Hospital , Heidelberg, Victoria, Australia .|2 Department of Surgery, University of Melbourne , Victoria, Australia .
authors.forename: Damien M
authors.initials: DM
authors.lastname: Bolton
mesh_terms: D002129:Calcium Oxalate; D016208:Databases, Factual; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging*; D008297:Male; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement; D011860:Radiography, Abdominal; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods; D014513:Ureter / Q000000981:diagnostic imaging*; D001743:Urinary Bladder / Q000000981:diagnostic imaging*; D052878:Urolithiasis / Q000000981:diagnostic imaging*
chemical_list: D002129:Calcium Oxalate