Fungal Balls Mimicking Renal Calculi: A Zebra Among Horses

Abstract

Background: Fungal masses (fungal ball or bezoars) rarely present as renal calculus. More so, Trichosporon species are even more uncommon among the noncandidial fungal infections affecting urinary tract. We report two such interesting cases that are not yet reported in the current literature.

Case Reports: Our first case is a 48-year-old gentleman with diabetes presented with fever and flank pain. He was found to have bilateral obstructing radiolucent renal calculi with azotemia. Initially managed with bilateral Double-J stenting after one session of hemodialysis, and subsequently bilateral percutaneous nephrolithotomy (PCNL) was accomplished. Our second patient is a 37-year-old lady presented with bilateral flank pain with no comorbidity or sepsis. On evaluation, she was found to have bilateral radiolucent staghorn calculi and for which bilateral PCNL was performed. In view of high suspicion of fungal infection, extracted soft floppy materials were sent for fungal culture and were treated with antifungal agents after Trichosporon species was detected.

Conclusion: Although renal fungal infections are rare, a strong suspicion and timely definitive management of such entities in patients with radiolucent renal calculus can prevent devastating invasive disease.

Introduction

Renal fungus ball or bezoar is a mass composed of fungal cells and sloughed renal epithelial cells, capable of obstructing the urinary tract.¹ Bezoars are a rare sequelae of urinary tract infection that can lead to significant morbidity such as fungemia, obstructive uropathy, renal failure, and even bladder rupture.^1–5

Trichosporon spp. are yeast-like anamorphic organisms widely distributed in nature and found predominantly in tropical and temperate areas.⁶ Trichosporon infections are uncommon, affecting immunocompromised hosts, especially those with prolonged neutropenia.⁷ Many other noncandidial organisms such as Aspergillus, Cryptococcos, Mucoromycetes, and Histoplasma have also been isolated from urinary tract, but Trichosporon fungal masses presenting as renal stones are not yet reported in the current literature.

We are the first to report two such interesting cases, who underwent percutaneous nephrolithotomy (PCNL) under the impression of radiolucent renal calculi.

Case Reports

Case #1

A 48-year-old diabetic male presented with intermittent low-grade fever and bilateral flank pain for 20 days and anuria for 2 days. On admission, he was febrile and normotensive with unremarkable abdominal examination. Although multiple echogenic masses were seen in ultrasonography, plain kidney, ureter, and bladder radiography did not reveal any abnormal radio-opaque shadow. A noncontrast CT showed bilateral obstructive renal calculi (HU ranging from 156 to 210) (Fig. 1a). Laboratory parameters showed poor glycemic control (HbA1c 12.2), severe anemia (hemoglobin 5.6 g%), and azotemia (serum creatinine 7.7 mg/dL, blood urea 156 mg/dL, and potassium 6.1 mmol/L). His total leukocyte count was normal with sterile blood and urine. Urine analysis revealed no suspicious crystals with a pH of 6.

FIG. 1.

(a) Axial CT KUB showing bilateral renal stones. (b) Right pyelogram showing stones as filling defects. (c) Retrieved fungal balls. (d) Microscopy showing Trichosporon sp. with anthroconidia. CT, computed tomography; KUB = kidney, ureter, and bladder radiograph.

Initially, bilateral Double-J stenting was performed after one session of hemodialysis accompanied by blood transfusion. Bilateral PCNL was accomplished in two separate sittings 4 days apart, with complete retrieval of soft shaggy material seen as filling defects in pyelogram (Fig. 1b). In view of high suspicion of fungal balls (Fig. 1c), antifungal solution irrigation was immediately started through nephrostomy tube (fluconazole 300 mg/500 mL NaCl 0.9% once per day for 12 hours). After 10 days, fungal culture of these “stone specimens” revealed Trichosporon species (Fig. 1d). Intravesical voriconazole (200 mg/150 mL NaCl 0.9% once daily) was instilled for 5 days with acceptable indwelling time before being allowed for voiding. Later, Double-J stents were removed. Finally, the patient was discharged in a stable condition with serum creatinine of 1.5 mg%.

Case #2

A 37-year-old female, with no known comorbidities, presented with bilateral intermittent flank pain for 3 months with no history of fever, urinary complaints, or prolonged hospitalization. Physical examination was unremarkable with normal renal parameters. CT images showed bilateral staghorn renal calculi (HU ranging from 215 to 252) (Fig. 2a), which were not detected in plain radiography.

FIG. 2.

(a) CT KUB coronal section showing bilateral staghorn renal stones. (b) Intraoperative appearance of fungal ball. (c) Extracted fungal balls. (d) Fungal colonies in Sabouraud's dextrose agar.

Bilateral PCNL was performed (Fig. 2b) with complete clearance. The retrieved soft stone materials (Fig. 2c) grew Trichosporon species in fungal culture (Fig. 2d). The patient was discharged on oral fluconazole after 5 days of local antifungal solution irrigation (fluconazole 300 mg/500 mL NaCl 0.9% once per day for 12 hours). However, voriconazole could not be administered to this patient, and as per schedule, Double-J stents were removed.

On follow-up after 3 months, both the patients were free of fungal infection as evidenced by repeated urine fungal culture and CT images.

Discussion

Among the noncandidial urinary tract infections, Trichosporon infections are unusual.^6,8 Especially, these occur in patients with obstructed urinary systems, long-term indwelling catheters, prolonged treatment with antimicrobial agents, or in patients with immunosuppression.^9,10 Owing to lack of clear and specific indications for clinical diagnosis, these infections pose a serious clinical threat. Noncontrast CT is considered as the modality of choice for diagnosing renal stone disease. However, it lacks specific differentiating features for renal fungal balls mimicking as renal stones. Therefore, if treatment gets delayed because of clinical dilemma, it may lead to obstructive uropathy and devastating invasive Trichosporonosis.⁶

Interestingly, one of our patients was devoid of any known predisposing factors and both the cases underwent percutaneous intervention under the impression of renal stone disease with areas of high attenuation in CT images because of encrustations that were detected later by stone analysis. However, low HUs of renal stones may give clinical clue about nonchemical composition in radiolucent stones.

To the best of our knowledge, these are the first reported cases of Trichosporon infection presenting as bilateral radiolucent renal stones. Effective management can be achieved with early endoscopic intervention (complete clearance), along with postoperative antifungal therapy (local and systemic). Maintaining the nephrostomy tube in situ for a reasonable time appears to be helpful to ensure the system free of fungus by adequate local antifungal irrigation. Although we have used intravesical instillation of voriconazole in one of our cases with Double-J stents in situ, however, its local use in urinary tract is not reported.

But voriconazole has been used locally for fungal infections elsewhere in the body.^11,12

Conclusion

Although renal fungal infections are rare, such entities must be considered when radiolucent urinary stone diseases are encountered, and thereby timely definitive management should be performed, aimed with complete clearance to prevent devastating invasive fungal disease.

Abbreviations Used

CT

computed tomography

HU

Hounsfield units

PCNL

percutaneous nephrolithotomy

KUB

kidney, ureter, and bladder radiograph

Disclosure Statement

No competing financial interests exist.

Cite this article as: Das MK, Rangrajan Pakshi R, Kalra S, Elumalai A, Theckumparampil N (2019) Fungal balls mimicking renal calculi: A zebra among horses, Journal of Endourology Case Reports 5:4, 167–170, DOI: 10.1089/cren.2019.0012.