Pyrexia of Unknown Origin (PUO)

A major diagnostic problem is the patient who has a pyrexia, either intermittent or continuous, that lasts for 2 weeks or more and in whom routine investigations have failed to reveal a cause. Pl.l O may merely be an unusual presentation of a common disease.  formation box 1.1 shows some of the common causes of pua. Age is an important pointer, since cancer and the connective tissue diseases are more common in the elderly. Immunocompromised individuals are at particular risk of infectious disease and often present with a particularly unusual spectrum of infections (see p. 100).

An aggressive approach to the diagnosis of pua is justified since there is a good chance that determination of a specific diagnosis will influence management and result in curative treatment. It is always worth repeating the history and examination since new signs may have evolved since the patient’s initial admission to hospital. All drug therapy should be reassessed and, if possible, stopped.

Infection (40%)
Pyogenic abscess, e.g. liver
Urinary infection
Biliary infection
Subacute infective endocarditis
EBV infection
CMV infection
Q fever
Cancer (30%)
Solid tumours, e.g.
Renal carcinoma
Hepatocellular carcinoma
Pancreatic carcinoma
Immunogenic (20%)
Connective tissue and autoimmune diseases, e.g.
Rheumatoid disease
Systemic lupus erythematosus
Polyarteritis nodosa
Polymyalgia/cranial arteritis
Factitious (1-5%)
Switching thermometers
Injection of pyrogenic material
Remain unknown (5-9%)


First-line investigations such as a full blood count, blood culture, urinalysis, routine blood chemistry and chest Xray should be repeated.

Other investigations

CT AND ULTRASOUND SCANNING are particularly valuable in revealing primary and secondary neoplastic diseases and also for showing occult abscesses. MRI is occasionally useful.

ASPIRATION OR NEEDLE BIOPSY under imaging control provides a histological diagnosis.

LAPAROSCOPY may be required to confirm a gynaecological cause, e.g. pelvic inflammatory disease, multiple peritoneal metastases or
tuberculous peritonitis.

NEEDLE BIOPSY OF THE LIVER (histology and culture) may be required to confirm granulomatous hepatitis, tuberculosis or metastatic cancer.

SCANNING WITH 59GALLIUM, which is taken up by polymorphs, or indium-Ill or technetium-labelled leucocytes, can localize an abscess.

Medical Assignments

Diuretic therapy

Diuretics increase salt and water excretion by the kidneys, thereby decreasing ventricular filling pressure (pre-load). This is

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