Lecture 25: Peritonitis and intra-abdominal infection

Question 1

Patients presentation with peritonitis?

Answer 1

Inflammation of the peritoneum - can be primary (rare and linked to liver disease), Secondary (most common), tertiary (following inadequate treatment of first case of peritonitus)

• Fever (>38˚C <36˚C)
• Increased HR and RR
• Nausea and vomiting
• Diffuse abdominal pait that might be more localised with rebound tenderness and abdominal wall rigidity
• Increased blood leukocytes
• CT/US shows fluid accumulation and inflammation

Question 2

Microbial causative agents?

Answer 2

Often polymcrobial infection that act synergistically and reflect the source of the infection (hopsital aquired infections may be one species)

Bacterial - enterobacteriaceae, anaerobes (found furhter down the GI tract, enterococci

Question 3

Routes of transmission? Risk Factors?

Answer 3

From GI tract to peritoneum via a perforation

• Appendicitis
• Divertculitis
• (ulcer, abcess, Surgery)

Risk factors:

1. Primary = liver disease, potral vein hypertension and ascites
2. Secondary = Appendicitis, diverticulitis, ulcers, surgery, CAPD
3. Tertiary = Immune deficiencies, previous 1˚ or 2˚ peritonitis

Question 4

What happens in the peritoneum?

Answer 4

Bacterial proliferation results in:

Inflammation

• fluid exudate in peritoneal cavity
• Dilution of antibacterial factors (eg. opsonins)
• May lead to hypovolemia

Abcess formation

• Fibrin deposited traps bacteria
• May prevent phagocytosis and other antimicrobial access
• Protease etc damage tissue leading to wider infection

Question 5

Diagnostic microbiology?

Answer 5

Aspirate pus - foul smelling

Gram stain of the pus - gram negative rods and positive cocci

Anaerobic and aerobic cultures

Question 6

Treatment of peritonitis?

Answer 6

Of symptoms:

• Fluids, pain relief
• Removal/drainage of pus guided by US/CT

Of source:

• Establish the cause and control the origin of sepsis
• Removal/drainage of pus
• Removal of dead tissue
• Corrective surgry to repair leak

Of the microbial cause

• Emperic antimicribial therapy
• Broad spectrum treatment (thriple therapy unless patient has liver/kidney disease concerns)
• vary 1-2 to 4-6+ weeks but should definitely be more than 1 week
• C. difficile infection with longer broad spectrum treatment regimes (elaborated on later in course)

Question 7

Metronidazole is a? Functions via? Effective against?

Answer 7

Bacteriacidal, amoebicidal and trichromoncidal

The exact mechanism is not known but its cytotoxic and antimicribial effects are though to be caused by disruption of DNA and inhibition of nucleic acid synthesis through low-redox-potential electron transfer proteins to unidentified polar products which lack the nitro group.

• Anaerobic gram neg. bacilli - bacteroids + fusobacterium
• Anaerobic gram pos. cocci - Clostridium species, eubacterium
• Wide range of pathogenic portozoa

BUT INNEFFECTIVE against all aerobic and facultatively anaerobic bacteria