Intra-abdominal Infections

Question 1

What are intra-abdominal Infections

Answer 1

Presence of microorganisms in normally sterile sites within the abdominal cavity

Question 2

Name two normally sterile sites in the abdominal cavity

Answer 2

Peritoneum
Hepatobiliary tract
Stomach

NOT GASTROENTERITIS

Question 3

Except for some anaerobes and candida species, the proximal intestine is relatively free from microorganisms. Why?

Answer 3

Bile inhibits growth

Question 4

What organism reside in the large bowel?

Answer 4

95-99% anaerobes
Some aerobic bacteria - - enterobacteriaceae (coliforms)
- Gram negativecocci (enterococci)

Question 5

What are the sources of a intraabdominal infection?

Answer 5

GI contents (lumen)
Blood
External e.g. surgery

Question 6

What are the mechanisms pf intra abdominal infection?

Answer 6

Transaction of microorganism from GI tract lumen to peritoneal cavity e.g. inter peritoneal infection

Translocation of MO along a lumen e.g. hepatobiliary infection

Translocation of MO from extra-intestinal source e.g. haematogenous spread, penetrating trauma

Question 7

What are the mechanisms by which infections translocate across a wall?

Answer 7

Perforation e.g. appendicitis, ulcer, diverticulum, cancer

Loss of integrity e.g. ischaemia, strangulation

Surgery e.g. seeding at operation, anastomotic leak

Question 8

What are the mechanisms by which infection translocate across a lumen?

Answer 8

Blockage e.g. cholecystitis, hepatic abcess

Iatrogenic e.g. instrumentation (ERCP)

Question 9

How does a perforated appendix cause peritonitis?

Answer 9

Obstruction of lumen of appendix (e.g. faecal matter/enlarged lymph)

Stagnation of luminal contents - bacterial growth

Increased luminal pressure - perforation into peritoneum

• peritonitis

Question 10

What are the complications of diverticulum?

Answer 10

Diverticulitis
Perforation
Pericolic abcess

Question 11

How is iscahemia cause in the GI?

Answer 11

strangulation
Arterial occlusion
Post operative e.g. aneurysm repair

Question 12

What is cholecystitis?

Answer 12

Inflammation of gallbladder wall

Question 13

What is cholecystitis associated with? What is this mainly caused by?

Answer 13

Obstructed cystic duct

Gallstones mainly, but can be malignancy, surgery, or parasitic worms

Question 14

What is the presentation of cholecystitis?

Answer 14

Fever, upper right quadrant pain, jaundice

Question 15

What is empyema of gallbladder and how does it present?

Answer 15

Frank pus in gallbladder

Same as cholecystitis but sepsis (severe pain, high fever, chills/rigor)

Requires removal

Question 16

What is cholangitis?

Answer 16

Infection/inflammation of biliary tree (hepatic duct and common bile duct)

Question 17

How is cholangitis caused? How does it present?

Answer 17

Obstruction of common bile duct

Fever, right upper quadrant pain, jaundice

Question 18

What is a pyogenic liver abcess? What are the main routes by which it is caused?

Answer 18

Pus forming in liver

• Biliary obstruction
• Spread from other intra-abdominal obstruction
• haematogenous - from mesentery or systemic

Question 19

What is an intra-peritoneal abcess?

Answer 19

Localised area of peritonitis with pus

Question 20

What are the predisposing factors ofintraperitoneal abcess?

Answer 20

Perforation e.g. ulcer, appendix, diverticulum
Cholecystitis
Mesenteric bowel infarction 
Pancreatitis/pancreatic necrosis 
Postoperative anastomotic leak

Question 21

What are the clinical presentations of an intraperitoneal abcess?

Answer 21

Nonspecific e.g. sweating, high swinging pyrexia, anorexia

Can show ipsilateral lung collapse with pleural effusion

Question 22

What are the main causative bacterial organisms?

Answer 22

Aerobic gram - Enterbacteriacae (cloriforms) e.g E coli, Pseudonomas

Anaerobic gram -
Bacteriorides

Aerobic gram +
Enterococcus, Strep milleri

Anaerobic Gram +
Clostridium

Question 23

Why are liver abcesses usually ‘sterile’?

Answer 23

Polymicrobial - hard to grow anaerobes

Question 24

What are liver accesses usually caused by?

Answer 24

Not GI flora

From haematogenous spread or trauma

Question 25

What diagnostic imaging should you perform?

Answer 25

Chest X-ray - consolidation, pleural effusion adjacent to infected area

Ab ultrasound

Ab CT Scan

Question 26

What is the antimicrobial therapy for these?

Answer 26

REMOVE abcess (drainage, resection)

Start smart
e.g. metronidazole and cefuroxime

Then focus
Narrowest spectrum based on culture results