Lecture 28: Peritonitis and Intra-Abdominal Infection

Question 1

What are the patient presentation for Periotinitis

Answer 1

Patient Presentation

• Fever (>38^oC; <36^oC)
• Increased heart rate (>90/min)
• Increased respiratory rate (>20/min)
• Nausea and vomiting
• Diffuse abdominal pain (may become more localized)
• Rebound tenderness
• Abdominal wall rigidity
• Increased blood leukocytes
• CT/US shows fluid accumulation, inflammation

Question 2

Define Peritonitis and the different types of peritonitis

Answer 2

Peritonitis is inflammation of peritoneum/serosal membrane lining abdominal cavity. It may be generalised/diffuse infection, or localised/abscess infection.

• Primary (Spontaneous) is diffuse bacterial infection without loss of GI tract integrity. Rare, associated with patients with liver disease.
• Secondary ** is acute infection resulting from loss of GI tract integrity or from infected viscera. Most common. Related to visceral pathology or post-surgical infection.
• Tertiary is recurrent infection of peritoneal cavity following adequate initial therapy. Often due to defective immunity.

Question 3

What are the causative agents of peritonitis?

Answer 3

Microbial Causative Agents

Polymicrobial infection: *

• More than one species involved. Synergistic infection.
• Reflective of the source. Hospital acquired infections may be one species

Bacterial include:

• Enterobacteriaceae such as Escherichia coli, Klebsiella, Enterobacter
• Anaerobes
  
  • GNB include Bacteroides fragilis, Prevotella
  • GPC include Peptostreptococcus
  • GPB include Clostridium
• Enterococci

Question 4

What are the sources of Causative agents that may cause peritonitis?

Answer 4

Infection sources are from GI tract:

• Stomach/duodenum (10³–10⁵ bacteria/ml) include aerobes and facultative anaerobes
• Jejunum/ileum (10⁴–10⁷ bacteria/ml) include transition from aerobes and facultative anaerobes to more anaerobes
• Colon (10¹¹–10¹³ bacteria/ml) include anaerobes and facultative anaerobes

Question 5

What are the routes of transmission of the microbes?

Answer 5

Route is usually from GI tract to peritoneum via a perforation:

• Appendicitis (ruptured appendix)
• Diverticulitis (rupture of inflamed diverticulum)
• Stomach/Duodenal ulcer
• Infection/abscess of other visceral organ
• Pelvic inflammatory disease
• Tubo-ovarian infection
• Necrotising enterocolitis (neonates)
• Surgery/Trauma

Question 6

What are the risk factors for periotonitis?

Answer 6

• Primary peritonitis due to
  
  • liver disease, portal vein hypertension and ascites.
• Secondary peritonitis due to
  
  • appendicitis, diverticulitis, ulcers etc.;
  • surgery, CAPD (CAPD (often just called ‘the bags’) is one type of peritoneal dialysis).
• Tertiary peritonitis due to
  
  • immune deficiencies; previous primary or secondary peritonitis

Question 7

What happens in the peritoneum?

Answer 7

1) Entrance and Non-Clearance

Bacteria gain entry. Bacteria not cleared.

• Normally there will be phagocytosis (macrophage)
• Normally bacteria quickly contained in a fibrin clot
• Clearance not effective in presence of nutrients (e.g. Haemoglobin) and necrotic tissue.

2) Proliferation and Inflammation

As a result, bacteria proliferate. Patient develops inflammation:

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

3) Abscess Formation

Finally, there is abscess formation:

• Fibrin deposited traps bacteria
  
  • (Bacteroides fragilis capsule promotes fibrin deposition to “hide” bacteria beneath)
• May p_revent phagocytosis_ and other antimicrobial access.
• Microbial growth continues
• Protease etc. damage to tissue
  
  • May lead to bacterial dissemination

Question 8

What are the patient presentations of peritonitis?

Answer 8

Patient Presentation

• Fever (>38^oC; <36^oC)
• Increased heart rate (>90/min)
• Increased respiratory rate (>20/min).
• Nausea and vomiting
• Diffuse abdominal pain that may become localised
• Rebound tenderness
• Abdominal wall rigidity
• Increased blood leukocytes

Question 9

What are the investigations you might udnertake with peritonitis?

Answer 9

Investigations

• CT/US shows fluid accumulation, inflammation
• Laparoscopy are diagnostic, and may allow treatment

Question 10

How do you diagnose microbiological cause of the peritonitis?

Answer 10

Diagnostic Microbiology

• Aspirate pus have foul smelling
• Gram’s stain of the pus from the abscess
  
  • Gram-negative rods,
  • Possibly Gram-positive cocci,
  • Probably more than one type
• Anaerobic and aerobic cultures
  
  • Culture from pus
  • Anaerobic transport swabs

Question 11

Describe how you wouild diagnose the presence of Bacteroids Fragilis.

What is it sensitive to?

Answer 11

Diagnostic Tests: Anaerobes And Bacteroides

Because of their fastidiousness, Bacteroides are difficult to isolate and often are overlooked. Bacteroides are Gram-negative rods

Often present in mixed infections (Escherichia coli cultured on MacConkey agar)

• Isolation requires appropriate methods of collection,
• Gas-liquid chromatography can be used to detect the volatile fatty acids produced by anaerobic bacteria
• Polymerase chain reaction (PCR)

Left figure shows growth of Bacteroides fragilis on bacteroides bile-esculin agar. Most aerobic and anaerobic bacteria are inhibited by bile and gentamicin in this medium, whereas B. fragilis group of organisms is stimulated by bile, resistant to gentamicin, and able to hydrolyze esculin, producing a black precipitate.

It is sensitive to Metrodinazole

Question 12

How do you treat periotonitis?

Answer 12

Treatment: Of Symptoms

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

Treatment: Of Source

• Establish the cause and control the origin of sepsis
• Removal/drainage of pus guided by US/CT
• Removal of dead tissue
• Corrective surgery to repair leak

Treatment: Of Microbial Cause

Broad spectrum empiric antimicrobial therapy

Triple therapy includes:

• Enterobacteriaceae (E. coli) treated with aminoglycoside, fluoroquinolone, 4^th generation cephalosporin
• Anaerobes (B. fragilis) treated with clindamycin, metronidazole
• Enterococcus treated with ampicillin

Single therapy is less toxic for patients with liver/kidney disease concerns

Question 13

What is the treatment time for peritonitis?

Answer 13

Treatment Time

Recommendations vary 1-2 to 4-6+ weeks to until resolved (free of fever, abdominal pain, normal WBC count, restoration of GI tract function). Should be 1 week, practice may be/recommend longer.

Note dangers of C. difficile infection with longer broad-spectrum treatment regimes. (may cause another infection)

Question 14

Describe Metronidazole

Answer 14

Metronidazole is bactericidal, amoebicidal (e.g. giardia) and trichomoncidal.

The exact mode of action has not been fully elucidated.

Metronidazole is bactericidal in vitro against:

• Anaerobic gram-negative bacilli including:
  
  • Bacteroides fragilis and other Bacteroides species;
  • Fusobacterium;
• Anaerobic gram-positive cocci including:
  
  • Clostridium species
  • Eubacterium,
  • Anaerobic Streptococci.
• A wide range of pathogenic protozoa including:
  
  • Trichomonas vaginalis and other trichomonads,
  • Entamoeba histolytica,
  • Giardia lamblia (acute gastroenteritis)

Metronidazole is ineffective against both aerobic and facultative anaerobic bacteria.

Question 15

How do you prevent Peritonitis?

Answer 15

Prompt diagnosis and treatment of predisposing conditions before it becomes peritonitis