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
What are the symptoms of perforation of the appendix?
severe, generalised pain
shock - gram -ve bacilli
appendix mass - inflammed appendix with covering od amentum and small bowel
What causes perforation of the diverticulum?
herniations of mucosa/submucosa through muscular layer in sigmoid and descending colon → infection/inflammation → perforation
Who most commonly has diverticuli?
older people
What are other systemic symptoms of bowel cancer?
weight loss
alteration in bowel habit
blood in stool
abdominal pain
What is ischemia and what causes ischemia?
interruption of intestinal blood supply e.g. strangulation, arterial occlusion, post op (aneurysm repair)
gut wall loses structural intergrity
What are the examples of post operative infections that cause intra-abdominal infections?
Seeding in operation - faeces escaping bowl into peritoneal cavity, antibiotics givenpre op just incase
anastomotic leak - lets bowel contents come out if surgery not done properly or join breaks down
acute infection - abdominal pain/tenderness, shock
intraperitoneal abscesses - walled off, indolent conditions i.e. symptoms some weeks after surgery
What is cholecystitis?
inflammation of the gallbladder wall
flow of bile allows ducts to remain sterile therefore no flow = infection
chemical inflammation
bacterial infection
What else is associated with cholecystitis?
gallstones
What are the typical presentations of cholecystitis?
fever
right upper quadrent pain
mild jaundice (common bile duct remains patent)
What is the typical presentation of empyema of the gallbladder?
severe pain high fever chills rigors septic + cholecystitis presentation
What is cholangitis?
inflammation/infection of biliary tree
What are the causes of cholangitis?
same as cholecystitis
mainly obstruction of common bile duct
can follow instrumentation
What is the typical presentation cholangitis?
fever rigors jaundice right upper quadrent pain may be non specific
What is pyogenic liver abscesses a complication of?
Cholangitis
What is pyogenic liver abscesses?
collection of pus on the liver
What are the causes of pyogenic liver abscesses?
bilary obstruction
direct spread from other intra-abdominal infections
haematogenous i.e. from mesenteric infection via the hepatic portal vein or systemic intravascular infection via hepatic artery (endocarditis)
penetrating trauma
idiopathic
What are intra-peritoneal abscesses?
localised are or peritonitis with build up of pus subphrenic - under the diaphram sub hepatic - under the liver paracolic pelvis
What is the typical presentation of intra peritoneal abscesses?
sweating
anarexia
wasting
high swinging pyrexia - temperature fluctuates up and down
What is the typical presentation of subphrenic intra peritoneal abscesses specifically?
pain in shoulder of affected side persistant hiccups (phrenic nerve?) intercostal tenderness hepatomegaly - liver displaced downwards, ipsilateral lung collapse with pleural effusion
What are the best antibiotics to start therapy with in intra-abdominal infections?
> 65 = Cefuroxime/metronidaxole
