A definite diagnosis can be made by aspirating the cyst and demonstrating bacteria on smear and culture.
A probable diagnosis can be made based on :
(1) a positive 18F-FDG PET/CT scan
(2) compatible clinical and/or imaging and/or laboratory findings
Clinical findings may include various combinations of:
(1) fever (> 38.5°C)
(2) systemic signs (malaise, weight loss, anorexia)
(2) abdominal or flank pain
(3) refractoriness to antibiotic therapy
Imaging findings:
(1) gas within the cyst, especially if new
(2) high intensity on diffusion-weighted imaging (cyst density > 4 times muscle density)
(3) cyst wall thickening
Laboratory findings:
(1) moderate to marked elevation of serum C-reactive protein (CRP)
(2) leukocytosis
(3) positive blood culture
(4) positive urine culture
