Intra-abdominal infections

Question 1

What is an intra-abdominal infection?

Answer 1

Presence of micro-organisms in normally-sterile sites within the abdominal cavity

• Peritoneal cavity
• Hepatobiliary tree

Question 2

Is the stomach considered to be sterile?

Answer 2

Yes

Question 3

Why is the proximal small intestine relatively free of bacteria?

Answer 3

Bacterial growth inhibited by bile

Sometimes candida present

Question 4

What are the sources of intra-abdominal infections?

Answer 4

• Gastrointestinal contents
• Blood
• External

Question 5

What are the mechanisms of intra-abdominal infection?

Answer 5

• Translocation of micro-organisms from gastrointestinal tract lumen to peritoneal cavity
  
  • Intraperitoneal infections
• Translocation of micro-organisms along a lumen
  
  • Biliary tract/hepatobiliary infections
• Translocation of micro-organisms from an extra-intestinal source
  
  • Penetrating trauma
  • Haematogenous spread

Question 6

How might translocation across a wall occur?

Answer 6

• Perforation
  
  • Perforated appendix, perforated ulcer, perforated diverticulum, malignancy
• Loss of integrity
  
  • Ischaemia, strangulation
• Surgery
  
  • Seeding at operation, anastomotic leak

Question 7

How might translocation along a lumen occur?

Answer 7

• Blockage
  
  • Cholecystitis, cholangitis, hepatic abscess
• Iatrogenic
• Instrumentation (e.g. ERCP)

Question 8

How might obstruction of the lumen of the vermiform appendix occur?

Answer 8

Lymphoid hyperplasia, faecal obstruction?

Question 9

What might be the consequence of obstruction of lumen of the vermiform appendix?

Answer 9

• Results in stagnation of luminal contents, bacterial growth and recruitment of inflammatory cells
• Build up of intraluminal pressure may result in perforation
• Escape of luminal contents into peritoneal cavity is “peritonitis”
• Severe, generalised pain
• Shock
• May localise to form “appendix mass”
• Inflamed appendix with adherent covering of omentum and small bowel

Question 10

What is an infrequent complication of bowel cancer?

Answer 10

• Intraperitoneal and/or bloodstream infection is an infrequent complication
  
  • Especially associated with Clostridium septicum and Streptococcus gallolyticus (formerly S. bovis) bloodstream infection
• Presumably caused by loss of bowel wall integrity due to abnormal malignant tissue

Question 11

What are the possible complications of diverticulosis?

Answer 11

• Diverticulitis
• Perforation
• Pericolic abscess

Question 12

How might ischaemia cause intra-peritoneal infection?

Answer 12

• Gut wall loses structural integrity

- Allows translocation of luminal contents

Question 13

What are the causes of intra-abdominal infection post-surgery?

Answer 13

• Seeding at operation
  
  • Incidence reduced with bowel preparation/prophylactic antibiotics
• Anastomotic leak

Result:

• Acute infection
  
  • Abdominal pain and tenderness
  • Shock
• Intraperitoneal abscess
  
  • Walled-off abscess
  • More indolent condition

Question 14

What is cholecystitis?

Answer 14

Inflammation of the gallbladder wall

• Chemical inflammation
• Bacterial infection may be cause or result of cholecystitis - Cultures positive in c. 50-75% of cases

Question 15

What is cholecystitis associated with?

Answer 15

Obstruction of the cystic duct:

• Gallstones (90%)
• Other causes
• Malignancy, surgery, parasitic worms
• Very occasionally no obstruction

Question 16

What is the presentation of cholecystitis?

Answer 16

Fever, right upper quadrant pain, mild jaundice (CBD remains patent)

Question 17

What is emphysematous cholecystitis?

Answer 17

Intramural gas in gallbladder wall

Question 18

What is empyema of the gallbladder?

Answer 18

• Complication of cholecystitis
• Frank pus in gallbladder
• Presentation is as for cholecystitis but septic presentation
  
  • Severe pain
  • High fever
  • Chills and rigors

Question 19

What is cholangitis?

Answer 19

Inflammation/infection of biliary tree (hepatic and common bile ducts)

Question 20

What are the causes of cholangitis?

Answer 20

• Mainly obstruction of common bile duct

- Can follow instrumentation (e.g. endoscopic retrograde cholangio-pancreatography, ERCP)

Question 21

What is the presentation of cholangitis?

Answer 21

• Fever (rigors), jaundice and right upper quadrant pain

- Presentation may be non-specific

Question 22

What are the possible sources of infection in pyogenic liver abcesses.

Answer 22

• Biliary obstruction
• Direct spread from other intra-abdominal infections
• Haematogenous
  
  • From mesenteric infection
    via hepatic portal vein
  • From systemic intravascular infection
    via hepatic artery
• Penetrating trauma
• Idipoathic

Question 23

What is an intraperitoneal abscess?

Answer 23

Localised area of peritonitis with build-up of pus

- Subphrenic, subhepatic, paracolic, pelvic etc.

Question 24

What are the predisposing factors for intraperitoneal abcesses?

Answer 24

• Perforation
  
  • Peptic ulcer
  • Perforated appendix
  • Perforated diverticulum
• Cholecystitis
• Mesenteric ischemia/bowel infarction
• Pancreatitis/pancreatic necrosis
• Penetrating trauma
• Postoperative anastomotic leak

Question 25

What is the presentation of an intraperitoneal abscess?

Answer 25

• Sweating, anorexia, wasting

- High swinging pyrexia

Question 26

What are the localising features of an intraperitoneal abscess?

Answer 26

Subphrenic abscess

• Pain in shoulder on affected side, persistent hiccup, intercostal tenderness, apparent hepatomegaly (liver displaced downwards, ipsilateral lung collapse with pleural effusion
• “Pus somewhere… pus nowhere… pus under the diaphragm.”

Pelvic abscess

• Urinary frequency
• Tenesmus

Question 27

What aerobic Gram-negative bacilli do you find causing GI problems?

Answer 27

• Enterobacteriaceae (coliforms)
  
  • Predominantly E. coli
  • Also Enterobacter, Citrobacter, Klebsiella, Proteus, Serratia, spp. etc.
• Pseudomonas spp.

Question 28

What anaerobic Gram-negative bacilli do you find causing GI problems?

Answer 28

Bacteroides spp., Prevotella spp.

Question 29

What aerobic Gram-positive cocci do you find causing GI problems?

Answer 29

• Enterococcus spp.

- Occasionally milleri-group streptococci (S. anginosus/constellatus group)

Question 30

What anaerobic Gram-positive cocci do you find causing GI problems?

Answer 30

Clostridium spp.

Question 31

What kind of bacterial colonise liver abscesses?

Answer 31

• Usually polymicrobial
  
  • May be “sterile” (contain hard-to-grow anaerobes)
  • May be other associated abscesses (e.g. brain)
• Infections secondary to haematogenous spread or trauma may not involve normal GI flora
• Hepatobiliary tract infections usually involve lower GI flora, despite duodenal origin

Question 32

What imaging would you perform in a suspected intra-abdominal infection?

Answer 32

• Chest x-ray
  
  • Consolidation, pleural effusion adjacent to infected area (e.g. subphrenic abscess)
• Abdominal ultrasound
  
  • Abdominal masses
  • Free fluid
  • Dilated bile ducts
• Abdominal CT scan
  
  • Higher definition than ultrasound

Question 33

What blood tests would you perform?

Answer 33

• Full blood count: neutrophilia/neutropenia
• C-reactive protein: raised
• Liver function tests: abnormal in hepatobiliary disease