Teaching Case

An 84-year-old male presented with complaints of subacute gross haematuria, nausea and generalised malaise. He had a background of uncontrolled diabetes mellitus type 2 secondary to corticotherapy, bullous pemphigus and benign prostatic hyperplasia with indwelling catheterization. The patient was haemodynamically stable and apyretic, and blood analysis revealed increased PCR (9,13 H) with no leukocytosis. Urinalysis showed pyuria, erythrocyturia and negative nitrites.

A CT scan was requested. The exam on the unenhanced phase revealed a round heterogeneous soft-tissue density with regions of gas and slight linear calcifications within the bladder lumen, next to a bladder catheter (Figure 1). The mass was not attached to the bladder wall, as shown by a rim of contrast on the excretory phase around the lesion (Figures 3a and 3b). The lesion did not reveal contrast enhancement (Figure 2). Signs of bladder outlet obstruction—diffuse bladder wall thickening, bladder diverticula and prostate enlargement—were present (Figure 2). Concomitant slight left hydronephrosis with no apparent obstructive cause and diffuse urothelial thickening were identified (Figure 2). Due to bladder mass suggestive of a fungus ball, the hypothesis of an ascending left urinary tract fungus infection was proposed. Consecutive urine cultures revealed candiduria. The patient was submitted to antifungal systemic therapy and a cystoscopic procedure to remove the fungus ball was proposed.

Opportunistic infections in the urinary tract are rare and preferentially seen in immunocompromised patients—submitted to organ transplants or affected by AIDS, poorly controlled diabetes mellitus, and haematologic malignancies—,  especially when there is upper urinary tract involvement. Prolonged antibiotic use, indwelling catheterisation, and conditions predisposing to urinary retention are other known risk factors. The presence of an indwelling bladder catheter is associated with biofilm formation, and this allows persistent colonisation by yeast, particularly, particularly Candida spp. [1–3].

Ascending infections are the most common and usually lead to the development of mycetoma or “fungus balls” within the urinary tract. These, on ultrasound, appear as mobile, round, heterogeneously hypoechoic masses with no evidence of vascularity using Doppler mode [4]. On non-enhanced CT images, fungus balls usually have a heterogeneous soft-tissue attenuation and can contain regions of gas or calcification. As there is no attachment to the urinary tract wall, a ring of urine peripheral to the mass, when seen, may elucidate the diagnosis [4]. The use of intravenous contrast with a complete urographic study may also contribute to the diagnosis as fungal balls may be homogeneous and isoattenuating to the urine, so only during the excretory phase they are revealed as filling defects [1]. At MR imaging, they are often isointense on T1-weighted images and hyperintense on T2-weighted images (compared with the appearance of renal parenchyma or bladder wall). As they are composed of a mixture of mycelia, mucoid debris, fragments from tissue necrosis, lithiasic debris and gas, with no vascular component, they do not enhance on any imaging modality, which may help in the differential diagnosis, namely with urinary tract neoplasias.

Treatment typically involves systemic antifungal therapy with urinary drainage if there is clinical and/or radiologic evidence of obstruction [5].

Written informed patient consent for publication has been obtained.