Empiric lipophilic antibiotics for ADPKD cyst infection

Question

A 60-year-old man with CKD G3b/A1 attributed to ADPKD presents to the emergency department with worsening abdominal pain. Pain is localized to the left flank and has worsened over the last 3 days, accompanied by occasional fever and chills. Kidney function has been stable, and CT scan of the abdomen 2 months ago showed numerous cortical cysts in the kidneys, liver, and pancreas, stable in size over the last 2 years. Many of the cysts had measured density consistent with hemorrhage, although the patient was asymptomatic at the time of the study. Medications include lisinopril and atorvastatin. BP is 116/76 mm Hg, heart rate is 98/min, and temperature is 39°C. Physical examination reveals a protuberant abdomen with mild tenderness to deep palpation of the left upper quadrant and left flank. Laboratory data are significant for WBC count 14,000/µL (reference range, 4000‒11,000) and C-reactive protein 10.1 mg/dL (reference range, ≤0.8). Hemoglobin is 14.5 g/dL and unchanged from baseline (reference range, 14–18). A urinalysis and urine culture are sent. Which of the following is the best next step in management?

Accepted Answer

C. Ciprofloxacin — This patient with ADPKD presenting with features of a cyst infection should receive antibiotic therapy likely to achieve good penetration into cysts.

The incidence of cyst infections in patients with ADPKD is low and estimated to be 0.01 episodes per patient per year; however, cyst infections may account for 11% of hospitalizations. Cyst infection is likely in patients presenting with fever, abdominal pain (especially in the area of a known cyst), and increased C-reactive protein (>7 mg/dL). Initial empiric treatment with antibiotics is recommended. Gram-negative rods, such as Escherichia coli, are the most frequently identified pathogens, but culture data are often lacking. Current recommendations are for a 14-day course of treatment with a fluoroquinolone or trimethoprim-sulfamethoxazole, if local antibiotic resistance data are acceptable. These antibiotics penetrate kidney cysts, although evidence supporting recommendations for their use is scarce. Although piperacillin-tazobactam is widely used for management of abdominal infections or sepsis of unknown source, β-lactam antibiotics have a higher clinical failure rate for the management of cyst infections in patients with ADPKD.

PET scan and cyst aspiration are highly sensitive for cyst infections but are generally not needed for diagnosis or treatment.

CT and ultrasound are less reliable to identify sources of infection. Although CT has been proposed as a step in the diagnostic algorithm for patients with ADPKD presenting with fever and abdominal pain because it may be able to identify cyst hemorrhage, such a study is unlikely to be useful in this patient with a recent baseline CT showing hemorrhagic cysts. Urine culture data are not always revealing, because cysts may not communicate with the collecting system, and culture results are not needed to initiate empiric treatment of cyst infections.

In cases of persistent or recurrent cyst infection, radiologic cyst aspirations or surgical cystectomy may be needed. Cyst aspiration may also be needed if infected cysts are >5 cm in diameter.

Empiric lipophilic antibiotics for ADPKD cyst infection

Explanation

Why each option

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