Gas-containing renal stones: a red flag for renal infection

Background Gas in the renal excretory system is described as a consequence of recent procedures but it can be a sign of severe conditions such as fistulas or infections; however, gas-containing renal stones are only rarely encountered. Purpose To describe the association of gas-containing renal stones and urinary tract infection. Material and Methods We performed a retrospective evaluation of the clinical and imaging findings in a series of six patients with gas-containing renal stones and compared our findings with those of patients with gas-containing renal stones reported in the literature. Urine and stone cultures were used as a diagnostic standard for urinary tract infection. Results Including the present series, there is a total of 21 patients with gas-containing renal stones in the literature. Based on clinical presentation, urinary tract infection could be suspected in 10 (57%) patients, while urine and/or stone cultures showed infection in 18 of 19 (95%) patients, with only one case with no bacterial growth in both (5%); in the remaining patient the information was not available. Conclusion Gas-containing renal stones are a rarely reported entity usually diagnosed with computed tomography. They are a radiological sign often associated with urinary tract infection that can also be encountered in patients with non-specific renal symptoms.