Diagnostic utility of fluorodeoxyglucose positron emission tomography/computed tomography in pyrexia of unknown origin

Abstract

Purpose of the study: The present study was undertaken to evaluate the diagnostic utility of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) in patients presenting as pyrexia of unknown origin (PUO).

Materials and methods: Forty-seven patients (31 males and 16 females; mean age of 42.7 ± 19.96 years) presenting as PUO to the Department of Medicine at the All India Institute of Medical Sciences, New Delhi over a period of 2 years underwent F-18 FDG PET/CT. PET ⁄ CT was considered supportive when its results correlated with the final definitive diagnosis. Final diagnosis was made on the basis of combined evaluation of history, clinical findings, investigations, and response to treatment.

Results: Thirty-five PET/CT studies (74.5%) were positive. However, only 18 (38.3%) were supportive of the final diagnosis. In three patients (6.4%), PET/CT was considered diagnostic as none of the other investigations including contrast-enhanced computed tomography of chest and abdomen, and directed tissue sampling could lead to the final diagnosis. All these three patients were diagnosed as aortoarteritis.

Conclusion: Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography is an important emerging modality in the workup of PUO. It supported the final diagnosis in 38% of our patients and was diagnostic in 6.4% of patients. Thus, PET/CT should only be considered as second-line investigation for the diagnostic evaluation of PUO; especially in suspected noninfectious inflammatory disorders.

Keywords: Fever; fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography; pyrexia; pyrexia of unknown origin.

Figure 1

Screening of study participants and summary of positron emission tomography/computed tomography findings

Figure 2

52-year-old man presented with fever of 1-year duration and large joints arthritis. (a) Maximum intensity projection whole body fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) image with abnormal FDG uptake in bilateral axillae, mediastinum, pelvis and enlarged spleen. (b and c) Trans-axial computed tomography (CT) and PET/CT images of the pelvis reveal enlarged FDG avid bilateral iliac lymph nodes (maximum standardized uptake value [SUV_max] = 3.3). (d and e) Transaxial CT and PET/CT images at the level of spleen show splenomegaly with increased FDG uptake (SUV_max = 1.6). FNAC from axillary lymph node showed reactive changes. Based on PET and clinical findings, a diagnosis of Still's disease was made

Figure 3

43-year-old lady presented with fever of five months duration associated with anorexia and weight loss. (a) Maximum intensity projection fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) whole body image reveals irregular areas of uptake in abdomen and pelvis. Trans-axial computed tomography (CT) and PET/CT images at the level of abdomen (b and c) and pelvis (d and e) reveal enlarged retroperitoneal nodes and pelvic nodes with increased FDG uptake (maximum standardized uptake value = 21). Diagnosis of lymphoma/TB made on PET/CT. Mesenteric and mesocolic lymph nodes of reportedly normal size were biopsied by mini-laparotomy and confirmed the diagnosis of Hodgkin's disease

Figure 4

38-year-old lady presented with fever of four months duration associated with anorexia, weight loss and myalgia. Maximum intensity projection fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) whole body image reveals multiple areas of increased FDG uptake throughout the body. Coronal PET/computed tomography (CT) image (b) localizes the patchy uptake to multiple skeletal muscles (arrow) (maximum standardized uptake value [SUV_max] = 2.4). (d) Diffusely increased FDG uptake in the enlarged spleen (SUV_max = 3.5). Diagnosis of inflammatory pathology involving muscles was made on PET/CT. Although creatine phosphokinase levels were normal but electromyography showed myopathic pattern and muscle biopsy revealed dermatomyositis

Figure 5

69-year-old man presented with fever of 5 months duration. His erythrocyte sedimentation rate was >100 mm and contrast-enhanced computed tomography chest, and abdomen was reported as normal. Coronal (b) and transaxial (d) PET/computed tomography images of thorax reveal increased fluorodeoxyglucose (FDG) uptake in walls of ascending thoracic aorta (thin arrow) (maximum standardized uptake value = 4). Also noted was increased FDG uptake in right hilar node (bold arrow) which was considered to be reactive. A diagnosis of large vessel vasculitis (aortoarteritis) was made, and patient responded to corticosteroids