Pyrexia of Unknown Origin & Bloodborne Infections

Question 1

What is pyrexia?

Answer 1

Fever

Question 2

How is someone diagnosed with pyrexia of unknown origin (PUO)?

Answer 2

Investigations into a sick patient with fever
Fever > 38C
No localising signs
Initial investigations are negative for > 3 weeks

Question 3

What investigations are done for sick patients with fever?

Answer 3

Most patients will have resolution without diagnosis
For others - rapid identification of focus and cause e.g. pneumonia, cellulitis

Question 4

What percentage of PUOs are caused by infections?

Answer 4

16%

Question 5

What percentage of PUOs are caused by malignancies?

Answer 5

7%

Question 6

What percentage of PUOs are caused by inflammatory conditions?

Answer 6

22%

Question 7

What percentage of PUOs have miscellaneous causes?

Answer 7

4%

Question 8

What percentage of PUOs causes remain unknown?

Answer 8

50%

Question 9

What are principal infectious causes of PUO?

Answer 9

TB and other mycobacteria
Endocarditis
Osteomyleitis
Deep abscesses - spine, liver, pelvic, retroperitoneal
Brucellosis
Typhoid fever
Malaria

Question 10

What are principal inflammatory causes of PUO?

Answer 10

SLE
Rheumatoid arthritis
Giant cell arthritis and other vasculitis
Sarcoid

Question 11

What malignancies can cause PUO?

Answer 11

Lymphoma
Myeloma
Renal cell carcinoma
Lung cancer

Question 12

What are some miscellaneous causes of PUO?

Answer 12

Factitious fever
Drug fever - inc antibiotics
Genetic e.g. FMF (family Mediterranean fever)

Question 13

What are some factors that may change the likely causes of PUO?

Answer 13

Geography - especially recent travel/migration
Smoking
HIV
Other immunosuppression
Age
Family history
Drug history
Animal contact
Occupation

Question 14

What is bacteraemia?

Answer 14

Bacteria in bloodstream
Not a single disease but an endpoint of different disease processes

Question 15

How is bacteraemia detected?

Answer 15

Blood cultures

Question 16

What is true bacteraemia often associated with?

Answer 16

Illness - fever, hypotension, organ failure, skin features (sepsis, septicaemia, septic shock)

Question 17

What infections can bacteraemia cause?

Answer 17

Tissue based infection
Device related infection
Endovascular infection

Question 18

Give examples of tissue based infections

Answer 18

UTI
Pneumonia
Peritonitis
Meningitis
Osteomyelitis
Cellulitis
Spinal abscess
Brain abscess

Question 19

Give examples of device related infections

Answer 19

Central line
Peripheral cannula
Pacemaker
Vascular graft

Question 20

What is endovascular infection?

Answer 20

Endocarditis

Question 21

What does bacteraemia result in?

Answer 21

Septicaemia and septic shock - fever, hypotension, multi-organ failure

Question 22

Describe endocarditis

Answer 22

Before antibiotics, virtually all patients died
Has many cardiac and non-cardiac features
Central lesion is the cardiac vegetation

Question 23

What are vegetations?

Answer 23

Masses composed of fibrin, platelets and infecting organisms, held together by agglutinating antibodies produced by the bacteria
Usually on valves

Question 24

What do vegetations lead to?

Answer 24

Valve destruction, perforation
Valve ring abscess
Chordae tendinae rupture
Myocardial abscess with/without pericarditis

Question 25

How are infected vegetations caused?

Answer 25

Bacteraemia provide a means of bacteria sticking to the endocardium, causing infected vegetation

Question 26

What are the main causes of bacteraemia in endocarditis?

Answer 26

Poor denitation with or without dental procedures - oral Streptococci Intravenous drug abuse (IVDA) Intravascular lines - e.g. for dialysis, parenteral nutrition (Staphylococci)

Question 27

How do bacteria stick to the endocardium?

Answer 27

Endocardium is damaged vWF adhered Platelets adhere Platelets bind fibrin Bacteria adhere More platelets and fibrin laid down, forming a vegetation

Question 28

What leads to a damaged endocardium?

Answer 28

Rheumatic heart disease Congenital heart disease Degenerative/calcific valves Prosthetic valves These all cause turbulence, which leads to a damaged endocardium

Question 29

What are clinical consequences of vegetations?

Answer 29

Infected vegetation leads to cardiac murmurs, valve rupture, regurgitation and heart failure Also causes bacteraemia and features of sepsis -> septic emboli -> lung abscess, brain abscess/stroke, spinal abscess, skin emboli, retinal emboli

Question 30

What is strep endocarditis often associated with?

Answer 30

Poor oral hygiene

Question 31

How is endocarditis diagnosed?

Answer 31

Blood culture and echocardiography

Question 32

Describe basic principles of treatment of endocarditis

Answer 32

If the bug is protected within the vegetation then high dose IV antibiotics, combination, prolonged treatment (3-6 weeks) If valve damage then surgery If prosthetic valve then surgery There is often high operative risk