Flashcards in Intra-abdominal infections Deck (33):
What is an intra-abdominal infection?
Presence of micro-organisms in normally-sterile sites within the abdominal cavity
- Peritoneal cavity
- Hepatobiliary tree
Is the stomach considered to be sterile?
Why is the proximal small intestine relatively free of bacteria?
Bacterial growth inhibited by bile
Sometimes candida present
What are the sources of intra-abdominal infections?
- Gastrointestinal contents
What are the mechanisms of intra-abdominal infection?
- 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
How might translocation across a wall occur?
- Perforated appendix, perforated ulcer, perforated diverticulum, malignancy
- Loss of integrity
- Ischaemia, strangulation
- Seeding at operation, anastomotic leak
How might translocation along a lumen occur?
- Cholecystitis, cholangitis, hepatic abscess
- Instrumentation (e.g. ERCP)
How might obstruction of the lumen of the vermiform appendix occur?
Lymphoid hyperplasia, faecal obstruction?
What might be the consequence of obstruction of lumen of the vermiform appendix?
- 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
- May localise to form “appendix mass”
- Inflamed appendix with adherent covering of omentum and small bowel
What is an infrequent complication of bowel cancer?
- 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
What are the possible complications of diverticulosis?
- Pericolic abscess
How might ischaemia cause intra-peritoneal infection?
- Gut wall loses structural integrity
- Allows translocation of luminal contents
What are the causes of intra-abdominal infection post-surgery?
- Seeding at operation
- Incidence reduced with bowel preparation/prophylactic antibiotics
- Anastomotic leak
- Acute infection
- Abdominal pain and tenderness
- Intraperitoneal abscess
- Walled-off abscess
- More indolent condition
What is cholecystitis?
Inflammation of the gallbladder wall
- Chemical inflammation
- Bacterial infection may be cause or result of cholecystitis - Cultures positive in c. 50-75% of cases
What is cholecystitis associated with?
Obstruction of the cystic duct:
- Gallstones (90%)
- Other causes
- Malignancy, surgery, parasitic worms
- Very occasionally no obstruction
What is the presentation of cholecystitis?
Fever, right upper quadrant pain, mild jaundice (CBD remains patent)
What is emphysematous cholecystitis?
Intramural gas in gallbladder wall
What is empyema of the gallbladder?
- Complication of cholecystitis
- Frank pus in gallbladder
- Presentation is as for cholecystitis but septic presentation
- Severe pain
- High fever
- Chills and rigors
What is cholangitis?
Inflammation/infection of biliary tree (hepatic and common bile ducts)
What are the causes of cholangitis?
- Mainly obstruction of common bile duct
- Can follow instrumentation (e.g. endoscopic retrograde cholangio-pancreatography, ERCP)
What is the presentation of cholangitis?
- Fever (rigors), jaundice and right upper quadrant pain
- Presentation may be non-specific
What are the possible sources of infection in pyogenic liver abcesses.
- Biliary obstruction
- Direct spread from other intra-abdominal infections
- From mesenteric infection
via hepatic portal vein
- From systemic intravascular infection
via hepatic artery
- Penetrating trauma
What is an intraperitoneal abscess?
Localised area of peritonitis with build-up of pus
- Subphrenic, subhepatic, paracolic, pelvic etc.
What are the predisposing factors for intraperitoneal abcesses?
- Peptic ulcer
- Perforated appendix
- Perforated diverticulum
- Mesenteric ischemia/bowel infarction
- Pancreatitis/pancreatic necrosis
- Penetrating trauma
- Postoperative anastomotic leak
What is the presentation of an intraperitoneal abscess?
- Sweating, anorexia, wasting
- High swinging pyrexia
What are the localising features of an intraperitoneal 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.”
- Urinary frequency
What aerobic Gram-negative bacilli do you find causing GI problems?
- Enterobacteriaceae (coliforms)
- Predominantly E. coli
- Also Enterobacter, Citrobacter, Klebsiella, Proteus, Serratia, spp. etc.
- Pseudomonas spp.
What anaerobic Gram-negative bacilli do you find causing GI problems?
Bacteroides spp., Prevotella spp.
What aerobic Gram-positive cocci do you find causing GI problems?
- Enterococcus spp.
- Occasionally milleri-group streptococci (S. anginosus/constellatus group)
What anaerobic Gram-positive cocci do you find causing GI problems?
What kind of bacterial colonise liver abscesses?
- 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
What imaging would you perform in a suspected intra-abdominal infection?
- 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