IMAGING STUDIES OF FEVER OF UNKNOWN ORIGIN

Diagnostic imaging has in many ways revolutionized the evaluation of FUO. Abdominal and pelvic computed tomography (CT) may be of great utility in the course of the work-up of an undiagnosed fever. These aids in determining invasive diagnostic testing, which can be carried out via radiologically guided biopsies and aspirations or by surgery, when necessary. Direct communication of the patient’s history with the evaluating radiologist is helpful in ensuring proper understanding of potential abnormalities. One drawback to CT scanning is that it may be too sensitive and may identify abnormalities that are unrelated to the cause of fever and that lead the further diagnostic work-up astray.

Ultrasonography in the form of echocardiography has a well-established and useful role. Ultrasonography of the right upper quadrant can occasionally give better biliary tract detail than an abdominal CT scan. Ultrasonography of the lower extremities may be useful in establishing the diagnosis of occult deep venous thromboses as a cause of fever in a few patients.

Given its utility in diagnosing many different causes of fever, echocardiography is also useful in the evaluation of an FUO. An initial transthoracic echocardiogram may identify valvular vegetations or thrombi. When a transthoracic echocardiogram is unrevealing, a transesophageal echocardiogram (TEE) is recommended. TEE has superior ability to visualize cardiac valvular abnormalities as well as to detect the presence of a pericardial effusion.

Nuclear medicine modalities have several roles in localizing disease, and their role continues to evolve. These studies are most useful in further elucidating potential infectious or inflammatory foci. Different radiopharmaceuticals are used to localize sites of inflammation via different mechanisms, lndium-111-labeled autologous leukocytes have been considered the nuclear medicine gold standard for identifying inflammation and infection because of their specificity. There is high uptake in any predominantly neutrophilic infiltrates, and lesions can be apparent early in their evolution. The gallium-67 scan is sometimes considered a better initial test because it has greater sensitivity in imaging acute, chronic, granulomatous inflammation and malignancy as well. Gallium binds to transferrin in blood and extravasates at sites of inflammation and infection.

More recently, it has been shown that positron emission tomography may have even greater utility in localizing different causes of an FUO. The positron emitting tracer, F-deoxyglucose, is taken up in metabolically active cells. Increased F-deoxyglucose uptake has been reported in many neoplastic and infectious diseases as well as vasculitides and granulomatous diseases. Positron emission tomography scanning may become an effective modality in the evaluation of FUO as its benefits and limitations continue to be defined.

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IMAGING STUDIES OF FEVER OF UNKNOWN ORIGINDiagnostic imaging has in many ways revolutionized the evaluation of FUO. Abdominal and pelvic computed tomography (CT) may be of great utility in the course of the work-up of an undiagnosed fever. These aids in determining invasive diagnostic testing, which can be carried out via radiologically guided biopsies and aspirations or by surgery, when necessary. Direct communication of the patient’s history with the evaluating radiologist is helpful in ensuring proper understanding of potential abnormalities. One drawback to CT scanning is that it may be too sensitive and may identify abnormalities that are unrelated to the cause of fever and that lead the further diagnostic work-up astray.Ultrasonography in the form of echocardiography has a well-established and useful role. Ultrasonography of the right upper quadrant can occasionally give better biliary tract detail than an abdominal CT scan. Ultrasonography of the lower extremities may be useful in establishing the diagnosis of occult deep venous thromboses as a cause of fever in a few patients.Given its utility in diagnosing many different causes of fever, echocardiography is also useful in the evaluation of an FUO. An initial transthoracic echocardiogram may identify valvular vegetations or thrombi. When a transthoracic echocardiogram is unrevealing, a transesophageal echocardiogram (TEE) is recommended. TEE has superior ability to visualize cardiac valvular abnormalities as well as to detect the presence of a pericardial effusion.Nuclear medicine modalities have several roles in localizing disease, and their role continues to evolve. These studies are most useful in further elucidating potential infectious or inflammatory foci. Different radiopharmaceuticals are used to localize sites of inflammation via different mechanisms, lndium-111-labeled autologous leukocytes have been considered the nuclear medicine gold standard for identifying inflammation and infection because of their specificity. There is high uptake in any predominantly neutrophilic infiltrates, and lesions can be apparent early in their evolution. The gallium-67 scan is sometimes considered a better initial test because it has greater sensitivity in imaging acute, chronic, granulomatous inflammation and malignancy as well. Gallium binds to transferrin in blood and extravasates at sites of inflammation and infection.More recently, it has been shown that positron emission tomography may have even greater utility in localizing different causes of an FUO. The positron emitting tracer, F-deoxyglucose, is taken up in metabolically active cells. Increased F-deoxyglucose uptake has been reported in many neoplastic and infectious diseases as well as vasculitides and granulomatous diseases. Positron emission tomography scanning may become an effective modality in the evaluation of FUO as its benefits and limitations continue to be defined.*153/348/5*

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