Don’t ignore elevated body temperature
Fever of Unknown Origin (FUO) refers to a condition in which the patient has an elevated body temperature, however, despite investigations by a physician no explanation can be found. If the cause is found by eliminating all possibilities, then only one explanation remains and it is considered as the correct one.
Criteria for diagnosis
• Fever higher than 38.3°C (101°F) on several occasions
• Persisting without diagnosis for at least three weeks
• At least one week’s investigation in hospital
A new definition, which includes the outpatient setting (which reflects current medical practice) is broader, stipulating:
• Three outpatient visits or
• Three days in the hospital without elucidation of a cause or
• One week of ‘intelligent and invasive’ ambulatory investigation.
Studies show there are five categories of conditions:
• Infection (e.g. abscesses, endocarditis, tuberculosis, and complicated urinary tract infections)
• Neoplasms/ malignancies / cancers (e.g. lymphomas, leukaemia, tumours)
• Connective tissue disease (e.g. temporal arteries and polymyalgia, rheumatica, still disease, systematic lupus erythematosus and rheumatoid arthritis)
• Miscellaneous disorders (e.g. alcoholic hepatitis, granulomatous conditions) and undiagnosed conditions
At present less frequent causes of FUO are indicated in three cases.
Nosocomial FUO refers to fever in patients who have been admitted to hospital for at least 24 hours. This is commonly related to hospital associated factors such as surgery, use of urinary catheter, intra-vascular devices (i.e. drip, pulmonary artery catheter), drugs (antibiotics induced colitis and drug fever), immobilisation (bed sores).
2. Immune deficient:
Immuno-deficiency can be seen in patients receiving chemotherapy or in hematologic malignancies. Fever is associated with Neutropenia (Neutrophil<500/ul) or impaired cell-mediated immunity. Infection is the most common cause.
3. Human Immuno-deficiency Virus (HIV) associated:
HIV-infected patients are a subgroup of the immunodeficient FUO and frequently have fever. The primary phase shows fever since it has a mononucleosis-like illness. In advanced stages of infection, fever mostly is the result of a superimposed infection.
Extra pulmonary tuberculosis is the most frequent cause of FUO. Drug induced fever, as sole symptom of an adverse reaction to medication, should always be considered. Lymphomas are the most common cause of FUO in adults. Thromboembolic disease (i.e. pulmonary embolism, deep venous thrombosis) occasionally shows fever. Although infrequent, its potentially lethal consequences warrant evaluation of this cause. Endocarditis (infection of heart valves), although uncommon, is another important thing to consider.
Unless the patient is acutely ill, no therapy should be started before the cause has been found. An exception is made for neutropenic patients where delay could lead to serious complications. After blood cultures are taken, this condition is aggressively treated with broad-spectrum antibiotics. Antibiotics are adjusted according to the results of the cultures taken. HIV-infected persons with fever and hypoxia (low oxygen concentration), will be started on medication.