Fate of indeterminate lesions detected on noncontrast computed tomography scan for suspected urolithiasis: a retrospective cohort study with a minimum follow-up of 15 months.

Objective: To investigate the fate of indeterminate lesions incidentally found on noncontrast computed tomography (NCCT) for suspected urolithiasis.

Methods: A retrospective review of 404 consecutive cases of suspected urolithiasis was undertaken between May 2010 and April 2011. Data were collected for patient demographics, presence of calculus disease, and additional urologic or nonurologic pathologies and their clinical relevance. The indeterminate or suspicious lesions were followed up and the data were reviewed in September 2012.

Results: In total, 404 patients underwent NCCT for renal colic (mean age, 50 years [range, 13-91 years]; 165 females). Minimum follow-up period was 15 months. Fifty-eight patients (14%) had ureteric, 85 (21%) had renal, and 39 patients (10%) had combined ureteric and renal stones. Noncalculus pathologies were found in 107 patients (26%). Sixty patients (15%) had indeterminate lesions. Of these patients, 6 required operative intervention, 35 had a benign diagnosis after further imaging and multidisciplinary team meeting, and 13 remained under surveillance after 1 year. Indeterminate pulmonary lesions (8 of 16) were the commonest lesions to remain under surveillance.

Conclusion: NCCT is vital for the diagnosis of urolithiasis with a pick up rate of 45% and remains the standard of care. However, with incidental detection of potential malignant lesions, a significant minority will need close monitoring, intervention, or both. In our study, approximately one-third of these lesions either remained under surveillance or had intervention.