Fever of unknown origin resident survival guide

Fever of unknown origin Resident Survival Guide
Diagnostic Criteria
Causes
Complete Diagnostic Approach
Empiric Therapy
Dos
Don'ts

Main article: Fever of unknown origin

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords: febris continua e causa ignota; febris e causa ignota; febris E.C.I.; fever/pyrexia of obscured/undetermined/uncertain/unidentifiable/unknown focus/origin/source; fever/pyrexia without a focus/origin/source; FUO; PUO

Diagnostic Criteria

Fever of unknown origin 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

Causes

Common Causes

Common causes of fever of unknown origin are as follows:

• Infections

Localized

– Endocarditis

– Intra-abdominal infections

– Urinary tract infections

– Osteomyelitis

– Upper respiratory tract infections

– Infected peripheral vessels

Generalized

– Bacterial

– Mycobacterial

– Fungal

– Viral

– Parasitic

• Neoplasia

– Lymphoproliferative disorders

– Leukemia

– Myelodysplastic syndrome

– Solid tumors

• 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

– Hyperthyroidism

– Thyroiditis

– Adrenocortical insufficiency

• Hereditary disorders (e.g., familial Mediterranean fever)
• Factitious fever
• Miscellaneous

– Granulomatous disorders

– Hepatitis

– Vascular disorders (e.g., pulmonary embolism, hematoma)

– Drug fever

Age-Specific Considerations

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: CBC, complete blood count; CI, cardiac index; CK-MB, creatine kinase MB isoform; CVP, central venous pressure; D/C, discontinue; DC, differential count; ICU, intensive care unit; INR, international normalized ratio; LFT, liver function test; MAP, mean arterial pressure; PCWP, pulmonary capillary wedge pressure; PT, prothrombin time; PTT, partial prothrombin time; SaO2, arterial oxygen saturation; SBP, systolic blood pressure; ScvO2, central venous oxygen saturation; s/o, suggestive of; SvO2, mixed venous oxygen saturation; SMA-7, sequential multiple analysis-7.

Suspected FUO 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
Obtain A Comprehensive History Verify the presence of fever and its pattern Continuous fever (s/o brucellosis, lobar pneumonia, typhoid, typhus, urinary tract infection) Intermittent fever (s/o malaria, kala-azar, pyaemia, septicemia) Quotidian fever (s/o Plasmodium falciparum or Plasmodium knowlesi malaria) Tertian fever (s/o Plasmodium vivax or Plasmodium ovale malaria) Quartan fever (s/o Plasmodium malariae malaria) Remittent fever (s/o infective endocarditis) Hectic or spiking pattern (s/o bacteremia) Pel-Ebstein pattern (s/o Hodgkin's lymphoma) Wunderlich curve (s/o typhoid fever) Picket fence pattern (s/o mastoiditis complicated by lateral sinus thrombosis) Saddleback pattern (s/o dengue fever, human granulocytic ehrlichiosis) Hyperpyrexia (s/o intracranial hemorrhage, sepsis, Kawasaki syndrome, neuroleptic malignant syndrome, serotonin syndrome, thyroid storm) History of medications (D/C non-essential drugs) History of previous surgeries or procedures History of malignancy and related therapy History of previously treated infections History of sick or animal contacts History of psychiatric illness History of recent traveling History of comorbidities History of transfusions Social and family history
Physical Examination Relative bradycardia

Empiric Antibiotic Therapy

Dos

Don'ts

References