Do patients with polycystic kidney disease have a higher risk of urinary tract infections?

Relationship Between UTI and Polycystic Kidney Disease

Yes, patients with autosomal dominant polycystic kidney disease (ADPKD) have a significantly increased risk of urinary tract infections, with cohort studies reporting UTI incidence rates of 15-25% in children and 21-75% in adults, compared to the general population. 1, 2

Epidemiology and Risk Factors

• UTIs occur in approximately 60% of ADPKD patients over their lifetime, with substantially higher rates than age-matched controls 3
• Female sex is a major predisposing factor, consistent with UTI patterns in the general population but amplified in ADPKD 4, 3
• Recent urinary tract instrumentation significantly increases infection risk in this population 4
• The increased UTI incidence appears independent of kidney function, as asymptomatic bacteriuria rates in ADPKD patients with normal kidney function (2%) do not differ from healthy controls (4%), suggesting the cystic architecture itself—not renal impairment—drives symptomatic infection risk 5

Critical Clinical Distinction: Cyst Infection vs. UTI

The 2025 KDIGO guideline emphasizes that infected kidney cysts are a distinct clinical entity from typical UTIs and do not communicate with the urinary collecting system. 6

Cyst Infection Presentation

• Fever >38°C with acute flank or abdominal pain and localized tenderness 6
• Markedly elevated inflammatory markers: CRP ≥50 mg/L OR WBC >11 × 10⁹/L 6
• Blood cultures positive in approximately 60% of cases, while urine cultures are negative in 40% because the infection is isolated within the cyst 3, 6
• Absence of white blood cell casts in urinary sediment distinguishes cyst infection from pyelonephritis 3

Uncomplicated UTI Presentation

• Typical lower urinary tract symptoms: dysuria, frequency, urgency 6
• Pyuria and positive urine culture 6
• White blood cell casts present in urinary sediment if upper tract involvement 3

Diagnostic Algorithm

Before initiating antibiotics in any febrile ADPKD patient, obtain BOTH urine AND blood cultures simultaneously. 6

1. Measure CRP and complete blood count: Values above thresholds (CRP ≥50 mg/L or WBC >11 × 10⁹/L) strongly favor cyst infection over simple UTI 6

2. Perform renal imaging (ultrasound, CT, or MRI) to exclude cyst hemorrhage or nephrolithiasis, which can mimic infection clinically 6, 1

3. When CRP ≥50 mg/L or WBC >11 × 10⁹/L accompanies fever and focal pain, obtain 18F-FDG PET-CT for definitive cyst infection localization, though this modality can produce false-negative results 1, 6

4. Interpret culture results in clinical context: Negative urine culture with positive blood culture strongly suggests cyst infection rather than pyelonephritis 3, 6

Treatment Recommendations

For Uncomplicated UTI (KDIGO 2025)

• First-line agents: nitrofurantoin, trimethoprim-sulfamethoxazole, or fosfomycin 6, 7
• Treatment duration: ≤7 days for acute cystitis 6, 7
• Do NOT treat asymptomatic bacteriuria, as it does not reduce future symptomatic UTI risk and promotes antibiotic resistance 6, 7

For Confirmed Cyst Infection (KDIGO 2025)

• Require 4-6 weeks of lipid-soluble antibiotics (trimethoprim-sulfamethoxazole or fluoroquinolones) for adequate cyst penetration 6, 7
• Fluoroquinolones (ciprofloxacin or levofloxacin) are preferred for superior cyst penetration, but clinicians must discuss the heightened risks of tendinopathy and aortic aneurysm/dissection with patients before initiating prolonged courses, particularly concerning given ADPKD patients' underlying vascular abnormalities 6, 1
• Start empiric therapy with third-generation IV cephalosporin (e.g., cefotaxime) with or without fluoroquinolone, targeting gram-negative Enterobacteriaceae, as E. coli accounts for 74% of cyst infections 6

Antibiotic Selection Based on Kidney Function

• Nitrofurantoin is contraindicated when creatinine clearance <30 mL/min due to insufficient efficacy and high risk of peripheral neuritis 7, 8
• For creatinine clearance 30-50 mL/min, use ciprofloxacin 500 mg every 12 hours without dose reduction 7
• For creatinine clearance <30 mL/min, extend ciprofloxacin interval to every 24 hours or select an alternative agent 7

Common Pitfalls and Caveats

• Do NOT assume positive urine culture equals the source of fever in ADPKD: 40% of cyst infections present with negative urine cultures because the infection is isolated from the collecting system 3, 6

• Avoid treating asymptomatic bacteriuria, which is present at similar rates in ADPKD patients with normal kidney function (2%) as in healthy controls (4%) and does not predict symptomatic UTI 5, 6

• Standard short-course UTI therapy will fail for cyst infections: Conventional antibiotics may not penetrate cysts adequately despite in vitro sensitivity, necessitating prolonged lipid-soluble antibiotic courses 4, 6

• In children with ADPKD, reported UTI rates of 15-25% may be overestimated because imaging performed for UTI evaluation often leads to incidental ADPKD diagnosis, creating ascertainment bias 1

• The 2019 international consensus states that no studies suggest increased incidence of complicated or prolonged infections in children with ADPKD, so local standards for UTI diagnosis and treatment in otherwise healthy children should be applied 1

Underlying Mechanisms

• Emerging evidence suggests α-intercalated cells of collecting ducts function in innate immune defense against UTI by acidifying urine and secreting neutrophil gelatinase-associated lipocalin (NGAL) that chelates iron 9

• ADPKD patients with recurrent UTI may have reduced numbers or impaired function of α-intercalated cells, though this mechanism remains under investigation 9

• The cystic architecture itself appears to predispose to infection independent of kidney function decline, as demonstrated by the lack of increased asymptomatic bacteriuria in ADPKD patients with preserved GFR 5