Renal fungal ball: an unusual sonographic finding.

Fungal infections of the urinary tract tend to occur in the drainage structures instead of the renal parenchyma. In patients with systemic candidiasis, the kidney is vulnerable to the formation of cortical abscesses or obstructive intrarenal masses ("fungal balls"), usually at the ureteropelvic junction. We describe the case of a boy who presented with dysuria, fever, and chills. Sonographic examination showed mild enlargement of both kidneys and moderate dilatation of the pelvicaliceal system bilaterally. A well-defined, echogenic, oval, mobile mass measuring 2.5 x 2.0 cm, without posterior acoustic shadowing, was visualized in the pelvis of the left kidney. The upper and middle ureters were dilated bilaterally. A urine culture revealed hyphae of Candida albicans. The child received systemic antifungal therapy with fluconazole for 3 weeks. Follow-up sonography showed complete resolution of the mass (a fungal ball) with residual hydronephrosis.