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Oct 8, 2015 - There were no false positives and no hypermetabolism of cyst walls in nine ADPKD control patients. 18-FDG PET–CT had a sensitivity of 77%, ...

ORIGINAL ARTICLE

INFECTIOUS DISEASES

Diagnostic performance of [18F]fluorodeoxyglucose positron emission tomography–computed tomography in cyst infection in patients with autosomal dominant polycystic kidney disease M. Bobot1, C. Ghez2, B. Gondouin1, M. Sallée1, P. E. Fournier3, S. Burtey1, T. Legris1, B. Dussol1, Y. Berland1, P. Souteyrand2, L. Tessonnier2, S. Cammilleri4 and N. Jourde-Chiche1 1) Aix-Marseille University, Department of Nephrology, 2) Aix-Marseille University, Department of Radiology, AP-HM Hopital Conception, 3) Aix-Marseille University, Department of Infectious Diseases, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes and 4) Aix-Marseille University, Department of Nuclear Medicine, AP-HM Hopital Timone, Marseille, France

Abstract Cyst infection is a common complication of autosomal dominant polycystic kidney disease (ADPKD). Diagnosis is challenging with standard imaging techniques. We aimed to evaluate the diagnostic performance of [18F]fluorodeoxyglucose positron emission tomography–computed tomography (18-FDG PET–CT) for the diagnosis of cyst infections among ADPKD patients, in comparison with computed tomography (CT) and magnetic resonance imaging (MRI). All APKD patients who underwent 18-FDG PET–CT for suspected cyst infection between 2006 and 2013 in a French teaching hospital were included. Diagnosis of cyst infection was retained a posteriori on an index of clinical suspicion. 18-FDG PET–CT findings were was considered to be positive in cases of cyst wall hypermetabolism. CT or MRI findings were were considered to be positive in cases of cyst wall thickening (and enhancement if contrast medium was injected) and infiltration of the adjacent fat. A control group of ADPKD patients with 18-FDG PET–CT performed for other reasons was included. Thirty-two 18-FDG PET–CT scans were performed in 24 ADPKD patients with suspected cyst infection. A diagnosis of cyst infection was retained in 18 of 32 cases: 14 with positive 18-FDG PET–CT findings, and four false negatives. There were no false positives and no hypermetabolism of cyst walls in nine ADPKD control patients. 18-FDG PET–CT had a sensitivity of 77%, a specificity of 100%, and a negative predictive value of 77%. 18-FDG PET–CT allowed a differential diagnosis in three patients. In contrast, CT had a sensitivity of 7% and a negative predictive value of 35% (p 38.5°C for >3 days, abdominal pain, an increased C-reactive protein (CRP) level (>50 mg/L), and the absence of recent intracystic bleeding on CT imaging (defined as spontaneous density of the cystic contents of >50 HU), in the absence of a differential diagnosis and after a favourable outcome with treatment. Imaging techniques 18-FDG PET–CT was performed in fasting patients, with the injection of 4 MBq/kg 18-FDG. PET acquisition was performed 60 min later in 3-min steps from the base of the skull to the midthigh. CT acquisition was performed prior to PET acquisition, from the head to the mid-thigh, without injection of iodinated contrast medium. Each 18-FDG PET–CT scan was re-read by the same experienced nuclear medicine physician, and was considered to be positive in the case of focal hypermetabolism of cyst wall(s), above normal fixation of residual normal parenchyma, and distinct from physiological urinary excretion. Maximum standardized uptake values were measured on cyst walls. CT was performed without iodinated contrast injection and with injection in the absence of severe CKD or if the patient was receiving chronic dialysis. MRI was performed with T1 phase and antiphase, T2, T2 STIR, and diffusion sequences. Gadolinium was injected in the absence of severe CKD. CT and MRI scans were re-read by the same experienced radiologist, blinded to the results of 18-FDG PET–CT. CT and MRI findings were considered to be positive in cases of cyst wall(s) thickening [15] with contrast enhancement in cases of injection [8,16], and infiltration of the adjacent fat. Statistical analysis Continuous variables were expressed as median ± standard deviation, and compared by use of the Mann–Whitney U-test. Categorical data were expressed as numbers (percentages), and compared by use of the chi-square test or Fisher’s exact test. All tests were two-sided. A p-value of

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