Intra-abdominal infections Flashcards
Where would you find intra-abdominal infections?
- Peritoneal cavity
- Hepatobiliary tree
- Excludes gastroenteritis as bowel lumen non-sterile
What is the main type of bacteria in the large intestine?
- 95-99% anaerobic bacteria
- Aerobic= enterobacteriaceae, gram +ve cocci
What are sources of intra-abdominal infection?
- Blood
- GI contents
- External
What are the mechanisms of I-A infection? What are these types of infections called?
- Translocation of micro-organisms from GI tract lumen to peritoneal cavity (intraperitoneal infections)
- Translocation of micro-organisms along lumen (biliary tract/ hepatobiliary infections)
- Translocation of micro-organisms from extra-intestinal source (penetrating trauma, haematogenous spread)
How do translocations across a wall occur?
- Perforation= appendix, ulcer, diverticulum, malignancy
- Loss of integrity= ischaemia, strangulation
- Surgery= seeding, anastomotic leak
How do translocations along a lumen occur?
- Blockage= cholecystitis, hepatic abscess, cholangitis
- Iatrogenic= instrumentation
How does a perforated appendix occur? What can this lead to?
- Mainly children/ young adults
- Obstruction of vermiform appendix (lymphoid hyperplasia, faecal obstruction)
- Results in stagnation of luminal contents, bacterial growth & recruitment of inflamm cells
- Build up of intraluminal pressure= perforation
- Escape of luminal contents into peritoneal cavity=peritonitis
- Severe generalised pain, shock
- May localise to form appendix mass-inflamed appendix w/adherent covering of momentum & s.bowel
What is a perforated diverticulum and its complications?
- Herniations of mucosa/submucosa through muscular layer
- Sigmoid & descending colon
- Complications: diverticulitis, pericolic abscess, peritonitis
How can bowel cancer lead to intra-abdominal infections?
- Intraperitoneal and/or bloodstream infection
- C. septum, Strep gallolyticus= bloodstream infection
- Loss of bowel wall integrity due to abnormal malignant tissue
- Symptoms= weight loss, altered bowel habit, blood in stool
How can ischaemia lead to I-A infections?
- Interruption of intestinal blood supply
- Strangulation
- Arterial occlusion
- Post-operative (aneurysm repair)
- Gut wall loses structural integrity
- Allows translocation of luminal contents
How can post-operative infection be an I-A infection?
- Seeding- incidence reduced w/bowel preparation/ prophylactic antibiotics
- Anastamotic leak
- Acute infection= shock, ado pain & tenderness
- Intraperitoneal abscess= walled-off abscess
What is cholecystitis?
- Inflammed gallbladder wall= chemical inflammation, bacterial infection
- Associated w/obstruction of cystic duct= gallstones, malignancy, surgery, parasitic worm
- Fever, RUQ pain, mild jaundice
- Emphysematous cholecystitis= intramural gas in gallbladder wall
What is empyema of the gallbladder?
- Complication of cholecystitis
- Frank pus in gallbladder
- Severe pain, high fever, chills & rigors, sepsis
What is cholangitis?
- Inflammed/infected billiary tree (hepatic & common bile ducts)
- Same causes as cholecystitis
- Fever, rigors, jaundice, RUQ pain
What are the routes of infection for pyogenic liver abscesses?
- Biliary obstruction
- Direct spread from other intra-abdominal infections
- Haematogenous (mesenteric infection via hepatic portal vein, systemic intravascular infection via hepatic artery)
- Idiopathic
- Penetrating trauma
What is intra-peritoneal abscesses? What are predisposing factors?
- Localised area of peritonitis w/build up of pus
- Perforated appendix/diverticulum /peptic ulcer
- Cholecystitis
- Mesenteric ischaemia/bowel infarction
- Pancreatitis/necrosis
- penetrating trauma
- postop anastamotic leak
How does an intra-peritoneal abscess present & what are localising features (e.g subphrenic&pelvic abscess)?
- Sweating, anorexia, wasting, high swinging pyrexia
- Subphrenic: pain in shoulder on affected side, persistent hiccups, intercostal tenderness, hepatomegaly (liver displaced downwards)
- Pelvic: urinary frequency, tenesmus
What are other intra-abdominal conditions?
- Spontaneous bacterial peritonitis (infected ascitic fluid)
- Pancreatic & splenic abscesses
- Amoebic abscesses (entamoeba histolytica)
- Hydatid cyst (echinococcus granulises)
- Ileo-caecal TB (mycobacterium TB)
Describe the microbiology of liver abscesses
- Polymicrobial
- Infections secondary to haematogenous spread/trauma not involving GI flora
- Hepatobiliary tract infections usually involve lower GI flora
What will be seen in a blood test diagnosing a intra-abdominal infections?
- Neutrophilia/neutropenia
- C-reactive protein raised
- Liver function test: abnormal in hepatobiliary disease
What is antimicrobial therapy?
- Treat underlying condition (resection, anastomosis, abscess drainage)
- Empirical antibiotics
- Then narrowest spectrum of antibiotics
- After 48hr pyrexial with normal white cell count switch to oral
