Intra-abdominal infections Flashcards
What is an intra-abdominal infection?
presence of micro-organisms in normally sterile sites within the abdominal cavity, not in the GI Tract e.g.
peritoneal cavity
hepatobilary tree
Describe the normal flora in the stomach
Stomach = sterile
Describe the normal flora in the small intestine
proximal small intestine = free of microorganisms (unless abnormal bowel which has more microorganisms in the small bowel)
growth inhibited by bowel
few aerobic bacteria and candida
distal small intestinal flora reflects large intestine
Describe the normal flora of the large intestine
very densely filled with microorganisms
mainly anaerboic bacteria
some aerobic bacteria e.g. enterobacteriaceae, gram +ve cocci
what is the rule when prescribing antibiotics?
Start SMART then FOCUS
What are the sources of intra-abdominal infection?
GI contents - mainly
blood
external e.g. surgery - unusual
What are the 3 different mechanisms by which intra-abdominal infections occur?
1) intraperitoneal infections - translocation from GI tract lumen to peritoneal cavity
2) Billary tract/hepatobilary infections - translocation of organisms along the lumen
3) penetrating trauma/haematogenous spread - translocation from an extra-intestinal source
What are examples of causes of translocation across a wall?
perforation (most common cause)
loss of integrity
surgery
What are examples for perforation that allow translocation of organisms across a wall?
perforated appendix - younger people
perforated ulcer - in duodenum/stomach, can cause systemic candida infection
perforated diverticulum - older people
malignancy - e.g. bowel cancer
What are examples for loss of integrity that allow translocation of organisms across a wall?
ischemia - blood supply acutely blocked off
strangulation - e.g. hernia, blood supply suddenly interupted
What are examples for surgery that allow translocation of organisms across a wall?
seeding at operation - leakage of bowel content into perineum, can be avoided by single dose antibiotics before surgery
anastomotic leak - during/after an opertation
Give the 2 ways the translaction across a lumen can occur
Blockage
Iatrogenic
What are examples for blockage that allow translocation of organisms along a lumen?
cholecystitis
cholangitis
hepatic abscesses
What are examples for iatrogenic that allow translocation of organisms along a lumen?
instrumentation e.g. endoscopic retrograde cholangiopancreatography - removing stones from biliary tree pushes the organisms further up
What causes perforation of the appendix?
obstruction of lumen of veriform appendix
e.g. lymphnoid hyperplasia
faecal obstruction
→ stagnation of luminal contents, bacterial growth and inflammatory cells
→ build up of pressure = perforation