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Fever of Unknown Origin (FUO)

Daniel R. Matta, DFPHM, FAAFP, MD and Nicholas Smith, MD Reviewed 04/2024
 


BASICS

DESCRIPTION

  • Classic definition

    • Repeated fever >38.3° C

    • Fever duration at least 3 weeks

    • Diagnosis remains uncertain (1) after 1 week of study in the hospital.

  • Categories of fever of unknown origi...

DIAGNOSIS

The initial approach should include a comprehensive history and physical examination, as well as laboratory testing. The decision of what further testing should be gathered should be guided ...

TREATMENT

GENERAL MEASURES

  • Treatment depends on the specific etiology.

  • Consider discontinuation of recently started or potentially offending medications.

  • Empiric therapy is not recommended in patients wi...

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Patient Monitoring

If the etiology of the fever remains unknown, repeat the history, physical exam, and screening lab studies. 

DIET

No specific dietary recommendati...

REFERENCES

1
Haidar G, Singh N. Fever of unknown origin. N Engl J Med. 2022;386(5):463–477.
2
 David A, Quinlan JD. Fever of unknown origin in adults. Am Fam Physician. 2022;105(2):137–143.
3
Cunha BA, Lor...

ADDITIONAL READING

van Rijsewijk ND, IJpma FFA, Wouthuyzen-Bakker M, et al. Molecular imaging of fever of unknown origin: an update. Semin Nucl Med. 2023;53(1):4–17. doi: 10.1053/...

SEE ALSO

  • Algorithms: Fever in the First 3 Months of Life; Fever of Unknown Origin (FUO)

CODES

ICD10

R50.9 Fever, unspecified 

SNOMED

7520000 Pyrexia of unknown origin (finding) 

CLINICAL PEARLS

  • A sequential approach to FUO based on a careful history, physical examination, with targeted testing and imaging typically yields an appropriate diagnosis and avoids excessive nontarge...

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