Fever of unknown origin resident survival guide
|Fever of Unknown Origin|
Management of fever of unknown origin should generally be withheld until the etiology is ascertained so that treatment can be targeted toward a specific pathology.
Fever of unknown origin (FUO) may be considered providing all the following criteria are fulfilled:
- Fever higher than 38.3°C (100.9°F) on several occasions
- Persisting without diagnosis for at least 3 weeks
- At least 1 week's investigation in hospital
Minimum diagnostic evaluation to qualify as FUO includes:
- Comprehensive history
- Repeated physical examination
- Complete blood count, including differential and platelet count
- Routine blood chemistry, including lactate dehydrogenase, bilirubin, and liver enzymes
- Urinalysis, including microscopic exmination
- Chest radiograph
- Erythrocyte sedimentation rate
- Antinuclear antibodies
- Rheumatoid factor
- Three or more sets of blood cultures while not receiving antibiotics
- Cytomegalovirus IgM antibodies or virus detection in blood
- Heterophile antibody test in children and young adults
- Tuberculin skin test
- CT of abdomen or radionuclide scan
- HIV antibodies or virus detection assay
- Further evaluation of any abnormalities detected by above tests
Common causes of fever of unknown origin are as follows:
- – Endocarditis
- – Intra-abdominal infections
- – Urinary tract infections
- – Osteomyelitis
- – Upper respiratory tract infections
- – Infected peripheral vessels
- – Bacterial
- – Mycobacterial
- – Fungal
- – Viral
- – Parasitic
- Rheumatic disorders
- – Adult onset Still's disease
- – Giant cell arteritis
- – Polymyalgia rheumatica
- – Other forms of vasculitis (e.g., polyarteritis nodosa, Wegener's granulomatosis, Takayasu's arteritis)
- – Other rheumatologic disorders (e.g., systemic lupus erythematosus, rheumatoid arthritis, Sjogren's syndrome)
- Endocrine disorders
- Hereditary disorders (e.g., familial Mediterranean fever)
- Factitious fever
- – Granulomatous disorders
- – Hepatitis
- – Vascular disorders (e.g., pulmonary embolism, hematoma)
- – Drug fever
Respiratory tract infections cause FUO in infants more often than in children older than 12 months, whereas connective tissue diseases predominate as the cause of FUO in children and adults. For patients older than 65 years, non-infectious inflammatory disorders including polymyalgia rheumatica and temporal arteritis are identified as the major causes of FUO in developed countries. Intra-abdominal abscesses, complicated urinary tract infections, tuberculosis, and endocarditis are the most common infectious causes of FUO in the elderly.
Complete Diagnostic Approach
Abbreviations: ALP, alkaline phosphatase; ALT, alanine aminotransferase; AST, aspartate aminotransferase; CBC, complete blood count; CMV, cytomegalovirus; DC, differential count; HIV, human immunodeficiency virus; PET, positron emission tomography; s/o, suggestive of; SMA-7, sequential multiple analysis-7.
Suspected Fever of Unknown Origin
Chest CT Scan
Abdominal CT Scan
Positron Emission Tomography
Lymph Node Biopsy
Bone Marrow Biopsy
Discontinuation of Nonessential Medications
Trial of Empiric Antibiotics
- Management should be withheld until the etiology is ascertained so that treatment can be directed toward a specific pathology.
- Empiric corticosteroids may be appropriate in patients with suspected temporal arteritis to prevent vascular complications.
- Patients with febrile neutropenia should receive broad-spectrum antipseudomonal antibiotics immediately after specimens for cultures have been obtained.
- Arnow, P. M.; Flaherty, J. P. (1997-08-23). "Fever of unknown origin". Lancet. 350 (9077): 575–580. doi:10.1016/S0140-6736(97)07061-X. ISSN 0140-6736. PMID 9284789.
- Hirschmann, J. V. (1997-03). "Fever of unknown origin in adults". Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America. 24 (3): 291–300, quiz 301-302. ISSN 1058-4838. PMID 9114175. Check date values in:
- Chantada, G.; Casak, S.; Plata, J. D.; Pociecha, J.; Bologna, R. (1994-04). "Children with fever of unknown origin in Argentina: an analysis of 113 cases". The Pediatric Infectious Disease Journal. 13 (4): 260–263. ISSN 0891-3668. PMID 8036040. Check date values in:
- Zenone, Thierry (2006). "Fever of unknown origin in adults: evaluation of 144 cases in a non-university hospital". Scandinavian Journal of Infectious Diseases. 38 (8): 632–638. doi:10.1080/00365540600606564. ISSN 0036-5548. PMID 16857607.
- Iikuni, Y.; Okada, J.; Kondo, H.; Kashiwazaki, S. (1994-02). "Current fever of unknown origin 1982-1992". Internal Medicine (Tokyo, Japan). 33 (2): 67–73. ISSN 0918-2918. PMID 8019044. Check date values in:
- Isaac, Benedict (1991). Unexplained fever : a guide to the diagnosis and management of febrile states in medicine, surgery, pediatrics, and subspecialties. Boca Raton: CRC Press. ISBN 9780849345562.
- Cunha, B. A. (1996-03). "The clinical significance of fever patterns". Infectious Disease Clinics of North America. 10 (1): 33–44. ISSN 0891-5520. PMID 8698993. Check date values in: