Beyond Candida: A clinical insight into rare fungal pyelonephritis in urological practice

Abstract

Introduction

Non-Candida fungal infections of the urinary tract, such as Aspergillus and Mucor, though uncommon, pose significant diagnostic and therapeutic challenges. Their variable presentation, antifungal resistance, and frequent association with immunocompromised states or prior instrumentation necessitate a high index of suspicion. This study aims to describe the clinical profile, diagnostic approach, and management outcomes of non-Candida fungal pyelonephritis in urological practice.

Material and methods

A retrospective observational analysis was conducted on four patients diagnosed with non-Candida fungal pyelonephritis at a tertiary urology centre between April 2024 and April 2025. Patients with urine cultures positive for fungi other than Candida were included. Data on clinical features, comorbidities, imaging findings, microbiology, intraoperative observations, treatment modalities, and outcomes were reviewed. Diagnosis was confirmed through culture and/or histopathology, and management was coordinated with infectious disease specialists.

Results

Four patients (three males, one female; age 37–72 years) were identified – three with Aspergillus and one with Mucor infection. Diabetes mellitus was the predominant comorbidity (3/4), and two patients had a history of prior urological instrumentation. Presentations ranged from incidental findings to pyelonephritis with fever and flank pain. Individualized management included minimally invasive percutaneous nephrolithotomy, pyeloplasty, percutaneous nephrostomy insertion, or nephrectomy. All patients responded to therapy, with infection clearance and preserved or improved renal function on follow-up. No mortality was observed.

Conclusions

Non-Candida fungal pyelonephritis, though rare, requires early diagnosis and individualized surgical and antifungal management. Multidisciplinary collaboration ensures favourable outcomes and renal preservation.

INTRODUCTION

Non-Candida fungal infections (Aspergillus, Mucor, Cryptococcus, etc.), though uncommon, pose significant diagnostic and therapeutic challenges due to their atypical presentation, resistance patterns, and association with immunocompromised states or indwelling devices. Managing non-Candida fungal pyelonephritis can be challenging for urologists.

We aim to enhance awareness regarding the clinical presentation, diagnostic approaches, and treatment strategies for non-Candida fungal pyelonephritis. By highlighting key risk factors, imaging findings, and evidence-based therapeutic interventions, we seek to facilitate early diagnosis and effective management, ultimately improving patient outcomes.

MATERIAL AND METHODS

A retrospective analysis was conducted of four patients diagnosed with non-Candida fungal pyelonephritis at a tertiary urology centre between April 2024 and April 2025. All patients whose urine culture was suggestive of a fungus other than Candida. Clinical records were collected for comorbidities, presenting symptoms, imaging findings, microbiological profiles, intraoperative findings, surgical interventions, and outcomes. Diagnosis was confirmed based on microbiological culture and/or histopathological examination. All patients were managed in coordination with infectious disease specialists, and follow-up data were assessed for clinical resolution and renal preservation.

Case 1

The patient was accidentally diagnosed with a low-density kidney stone on computed tomography

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Mini-perc fungal elements: percutaneous nephrostomy (PCN) + culture

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Aspergillosis: Broth microdilution – treated with voriconazole

Case 2

Patient presented with pyelonephritis and pelvi-ureteric junction obstruction (PUJO)

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Renal pelvis culture: Aspergillus

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Treated with antifungal

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Pyeloplasty

Case 3

Patient presented with fever and renal calculi

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PCN

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Culture s/o Aspergillus

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Antifungal

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Percutaneous nephrolithotomy (PCNL)

Case 4

Patient referred from outside with unresolved pyelonephritis despite stenting

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PCN insertion

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Blood culture and sensitivity (CS) test, and renal urine CS s/o Rhizopus

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Amphotericin via PCN and intravenous

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Unresolving sepsis

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Nephrectomy under the cover of liposomal amphotericin B

Bioethical standards

Study was conducted in accordance with the Declaration of Helsinki. This study was approved by the Deenanath Mangeshkar Hospital Scientific and Ethics Comittee.

The participant provided written consent.

RESULTS

Four cases of non-Candida fungal pyelonephritis were retrospectively analyzed. The patients included three males and one female, aged between 37 and 72 years. Three patients had Aspergillus, and one had Mucor. Diabetes mellitus was the most common comorbidity (3/4 cases), with one patient also on chronic steroid therapy. Two patients had a history of prior urological instrumentation (PCNL and URSL).

Clinical presentation varied, including incidental diagnosis, pyelonephritis, and fever with flank. Management strategies were individualized: one patient underwent mini-perc, another pyeloplasty, one required PCN insertion, and one underwent nephrectomy (Table 1, Figures 1–4).

Table 1.

Presentation and management of all cases

Variable	Case1	Case 2	Case 3	Case 4
Age (years)	56	37	72	41
Sex	M	F	M	M
Comorbidities	DM, steroids	None	DM	DM
Previous instrumentation	–	h/o PCNL	h/o URSL	–
Presentation	Accidental (15 mm PUJ calculus 150 HU with HN) (Figures 1, 2)	Fever and flank pain, PUJO	Renal calculi (post-URSL fever)	Pyelonephritis
Management	Mini PERC	Pyeloplasty	PCN insertion	Nephrectomy
Follow up	Renal function Improved	Resolution of HDN	Stone free, culture -ve	Infection free
Mortality	–	–	–	–
Antifungal	Inj. voriconazole followed by tab. voriconazole 200 mg twice a day	Inj. voriconazole followed by tab. voriconazole 200 mg twice a day	Inj. voriconazole followed by tab. voriconazole 200 mg twice a day	Amphotericin B i.v. and via PCN
Duration (weeks)	6	6	6	4 i.v.
Monitoring	Serum electrolytes and voriconazole levels every 72 hours. Urine fungal culture with BMD after 6 weeks	Serum electrolytes and voriconazole levels every 72 hours. Urine fungal culture with BMD after 6 weeks	Serum electrolytes and voriconazole levels every 72 hours. Urine fungal culture with BMD after 6 weeks	RFT, LFT, Haemogram every 48 hours. Urien and blood fungal culture after 4 weeks

BMD – broth micro-dilution; DM – diabetes mellitus; HN – hydronephrosis; LFT – Liver Function Test; PCN – percutaneous nephrostomy; PCNL – percutaneous nephrolithotomy; PUJO – pelvi-ureteric junction obstruction; RFT – Renal Function Test; URSL – ureteroscopic lithotripsy

Figure 1.

Case 1: Fungal matter in the right renal pelvis was misinterpreted as a low-density calculus. It may also mimic renal tuberculosis or xanthogranulomatous pyelonephritis on imaging and clinical presentation. In this case, it was planned for mini-perc.

Figure 4.

Case 3: Patient presented with fever and a right renal stone, post-recent history of URSL. PCN was inserted as thick fungal exudates were not expected to drain through the DJ stent.

Figure 2.

Case 1: Intra-operative image – on inserting the scope during mini-perc, a fungal element was found instead of a stone.

Figure 3.

Case 2: Patient had a recent history of Left PCNL and presented to us with symptoms of pyelonephritis. On imaging, left PUJ obstruction was seen, and renal urine culture was suggestive of Aspergillus. The patient was treated adequately with anti-fungal followed by pyeloplasty.

Outcomes were favourable in all cases with no reported mortality. Follow-up showed improved renal function, resolution of hydronephrosis, infection clearance, and negative cultures. These cases underscore the variable presentation and need for tailored management.

DISCUSSION

Differential diagnoses: Invasive non-Candida fungal pyelonephritis can mimic renal tuberculosis and xanthogranulomatous pyelonephritis (XGPN) on imaging, both showing low-density calcific material and chronic inflammatory changes. Hence, these entities should be included in the differential diagnosis for very low-density renal calculi or renal pelvic masses [1].

Predominance of renal aspergillosis: Within genitourinary fungal infections, renal aspergillosis constitutes nearly 80–81% of cases [1].

Clinical presentation: The most frequent symptoms are flank pain (≈36%) and fever (≈33%), though patients may also present with obstructive uropathy, sepsis, or non-functioning kidney [1].

Risk factors: Diabetes mellitus remains the most prevalent risk factor, followed by HIV infection and other causes of immunosuppression [2, 3].

Microbiological findings: Routine per-urethral urine cultures are often negative; fungal growth is more frequently obtained from renal pelvic urine or tissue cultures, highlighting the importance of targeted sampling [1].

Pharmacologic considerations: As posaconazole is poorly excreted unchanged in urine, voriconazole or liposomal amphotericin B (recommended dose 5 mg/kg/day for patients with normal renal function) are preferred systemic antifungals [1]. Therapeutic drug monitoring and assessment of hepatic/renal function are advised during therapy. Monitor serum voriconazole levels every 72 hours to prevent its toxicity.

Mucormycosis: Renal Mucormycosis is a rapidly progressive, angio-invasive infection with reported mortality between 44% and 85% [4]. Over 50% of cases require nephrectomy or percutaneous drainage due to poor response to antifungal therapy alone [5, 6].

Mortality: 28%.

Decision-making: surgery vs medical therapy: Management should be individualized according to:

• Extent and location of disease – localized fungal balls or superficial lesions may respond to antifungals ±endoscopic removal.

• Renal function – non-functioning kidneys with necrosis or sepsis typically mandate nephrectomy.

• Clinical response – persistent fever or sepsis despite optimal antifungal therapy necessitates surgical intervention.

• Source control – percutaneous or endoscopic drainage improves outcome in obstructed or suppurative disease [1].

Summary: Early suspicion, directed renal pelvic sampling, prompt initiation of appropriate antifungal therapy, and timely source control through drainage or surgery are critical to improving survival in non-Candida fungal pyelonephritis [1].

CONCLUSIONS

Non-Candida fungal pyelonephritis is a rare but clinically significant entity that requires high suspicion, especially in immunocompromised or post-instrumentation patients. It presents variably and may mimic other urological conditions, necessitating individualized approaches. Early identification and appropriate surgical intervention, in conjunction with antifungal therapy, can lead to favorable outcomes and renal preservation. Multidisciplinary collaboration is key to managing this challenging infection effectively.

CONFLICT OF INTERESTS

The authors declare no conflict of interest.

ETHICS APPROVAL STATEMENT

The study was approved by the Deenanath Mangeshkar Hospital Scientific and Ethics Comittee.

Funding Statement

FUNDING This research received no external funding.