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E-Poster Submission Deadline
Please prepare and upload your E-Poster no later than March 14, 2026 11.59PM CET. After this date, you will no longer be able to prepare and upload your E-poster and it will not be displayed and accessible on the congress website.
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Abstract titles should be brief and reflect the content of the abstract.
Medullary sponge kidney (MSK) predisposes to recurrent urinary tract infections (UTIs) due to structural abnormalities. Management becomes challenging when immunosuppression, antimicrobial resistance, and drug allergies limit therapeutic options.
A woman in her 60s with rheumatoid arthritis, controlled on sulfasalazine 1,000 mg/day and subcutaneous tocilizumab 162 mg every 2 weeks, was diagnosed with MSK in her 40s after pyelonephritis and diffuse medullary calcifications on non-contrast CT. She had recurrent UTIs, with multiple relapses annually since year X–6. Urine cultures repeatedly yielded multidrug-resistant Escherichia coli resistant to ampicillin, levofloxacin, and trimethoprim–sulfamethoxazole. Due to frequent relapses (May 7–June 5 and June 18–July 5, year X), tocilizumab was withheld after May 1. On July 16 she presented with worsening polyarthralgia and pyuria (≥50 WBC/HPF) and CRP 0.36 mg/dL. She was admitted on July 18.
Tocilizumab 162 mg was reinitiated on admission. Considering her medical history, the treatment plan for her UTI comprised the administration of oral cephalexin at a dose of 1.5 grams, combined with intravenous gentamicin at a dosage of 60 mg. Cephalexin was one of the few cephalosporin antibiotics she had tolerated, and gentamicin was an aminoglycoside that had not been previously used in this patient. By July 22, the CRP level fell to less than 0.05 mg/dL, the bacteriuria cleared, and the urinary WBC improved to 20–29/HPF. However, eGFR declined from 54.3 to 29.4 mL/min/1.73 m². We considered aminoglycoside-related nephrotoxicity as a contributing factor. Cephalexin was tapered to 1 g on July 24 and 0.75 g on July 25. Gentamicin was reduced to 60 mg every other day from July 23 and discontinued on July 29. On August 6, the recurrence prompted the oral administration of fosfomycin calcium at a dosage of 9 grams daily (the combination was ceased due to diarrhea). Thereafter, CRP remained below 0.05 mg/dL, bacteriuria was absent, urinary WBC improved to 1–5/HPF, and eGFR recovered to 39.5 mL/min/1.73 m². Joint symptoms remained under control following the single tocilizumab dose.
In cases of MSK complicated by immunosuppression, recurrent UTIs may require tailored, stepwise regimens and careful antimicrobial stewardship when resistance and allergies constrain options. A strategic selection and sequencing of agents, including cephalexin (dosage adjusted for body weight), gentamicin, and fosfomycin calcium 9 g/day, was instrumental in achieving infection control while minimizing the risk of nephrotoxicity.
