Fever

Fever of more than three weeks duration remaining undiagnosed after a week of hospitalization is defined as pyrexia of unknown origin (PUO).
PUO may be due to the infections, malignancy, inflammatory diseases, drugs or factitious. Infections are the leading causes of PUO tuberculosis often extrapulmonary, HIV infection, infective endocarditis, prolonged mononucleosis, intraabdominal abscess and fungal infections.
Malignancies associated with PUO are lymphomas, leukemia, renal cell carcinoma and hepatoma. Immunoinflammatory causes of PUO include SLE and adult Still’s diseases.
A proper detailed history and physical examination is critical in estabilishing a dignosis and for planing investigations. The pattern of fever is seldom diagnostic by itself. Drug history, occupational hisory and sexual practices are important areas that need to be investigated.
Routine haematologic and urinary investigations, serum chemistry and chest X-ray are important investigations in all patients. A markedly elevated ESR may indicate an infection or immunoinflammatory diseases, temporal athritis, Still’s diseases. US/CT may be obtained for evaluating hepatobiliary, renal, retroperitoneal and pelvic sources of PUO and for screening for occult primaries. An echocardiogram may be ordered if endocarditis is suspected. Biopsy of the bone marrow or liver may be useful if the non-invasive investigations do not yield a definitive diagnosis.
In the absence of a definite diagnosis, a therapeutic trial of antitubercular therapy may be instituted for six weeks.
Causes of prolonged fever
• Infections
o Polygenic infection: pyogenic abscess, cholangitis, pelvic abscess, diverticular abscess, thermbophlebitis.
o Vascular infection: Infective endocartitis, infected vascular access devices.
o Chronic granulomatious infection: Tuberculosis, atypical mycobacterial infections, fungal infection.
o Other prolonged bacterial and rickettisial illnesses: Brucellosis, chronic meningococcemia.
• Immunoinflammatory diseases: Systemic lumps erythematosus, juvenile rheumatoid arthritis(stills diseases), vasculitis including giant cell arthritis.
• Neoplasms: Primary (renal, pancreas, hepatic, lung, colon), secondary(hepatic secondaries), lymphoid neoplasms(lymphomas).
• Granulomatous conditions: Sarcoidosis.
• Metabolic and familial conditions: Familial Mediterranean fever, Fabry’s diseases.
• Drug induced fever
• Factitious fever
• Undiagnosed fever.