Intra-abdominal infections Flashcards
What is the definition of intra-abdominal infection?
Presence of micro-organisms in normally sterile sights within the abdominal cavity eg. the peritoneal cavity or hepatobiliary tree
Is gastro-enteritis an intra-abdominal infection?
No as the bowel lumen is a non sterile sight
Are normal flora found in the stomach?
No - the stomach is considered to be sterile
Why is the proximal small intestine relatively free of microorganisms, what few organisms are found?
Growth is inhibited by bile
A few aerobic bacteria and Candida spp
What is the flora of the small intestine?
Same as that of large intestine
The large intestine has mainly anaerobic bacteria, what 2 aerobic bacteria are also found?
1) Enterobacteriacae (enteric GNB, coliforms)
2) Gram-positive cocci (mainly enterococci)
What are the 3 main sources of intra-abdominal infection?
1) Gastrointestinal contents
2) Blood
3) External
What are the mechanisms of intra-abdominal infection, each is typical of what kind of infection?
1) Translocation of micro-organisms from GIT lumen to peritoneal cavity - intraperitoneal infections
2) Translocation of micro-organisms along a lumen - biliary tract/ hepatobiliary infections
3) Translocation of micro-organisms from an extra-intestinal source - penetrating trauma, haematogenous spread
What are the 3 possible reasons for translocation of organisms across a wall causing intra-abdominal infection?
1) Perforation - perforated appendix, perforated ulcer, perforated diverticulum, malignancy
2) Loss of wall integrity (not actually a perforation but still gets through) - ischaemia and strangulation
3) Surgery - seeding at operation, anastomotic leak
What are the 2 possible reasons for translocation along a lumen causing intra-abdominal infection?
1) Blockage - cholecystitis, cholangitis, hepatic abscess
2) Iatrogenic - instrumentation (eg. endoscopic retrograde cholangiopancreatography)
Perforated appendix is mainly a disease of what group of people?
Children and young adults
What is the main symptom of perforated appendix?
Severe, generalised pain
What condition can perforated appendix lead to?
Shock
How does a perforated appendix occur?
1) Lymphoid hyperplasia or faecal obstruction
2) Results in stagnation of luminal contents, bacterial growth and recruitment of inflammatory cells
3) Build up of intraluminal pressure may result in perforation
4) Escape of luminal contents into peritoneal cavity is peritonitis
Perforated appendix can localise to form what?
An appendix mass
Inflamed appendix with adherent covering of omentum and small bowel
What are diverticula?
Herniations of mucosa/submucosa through muscular layer in the sigmoid and descending colon
How common are asymptomatic diverticula?
50% in over 70 years
What are the 3 main complications of diverticula disease?
1) Diverticulitis
2) Perforation
3) Pericolic abscess
Is intraperitoneal or bloodstream infection a common complication of bowel cancer?
Intraperitoneal and/or bloodstream infection is an infrequent complication of bowel cancer
Bowel cancer is particularly associated with what 2 infections?
1) Clostridium septicum
2) Streptococcus gallolyticus (formerly S bovis) bloodstream infection
What is intra-abdominal infection in bowel cancer caused by?
Loss of bowel wall integrity due to abnormal malignant tissue
Why does ischaemia lead to translocation of bowel contents cause intra-abdominal infection?
1) Interruption of intestinal blood supply
eg. strangulation, arterial occlusion, post-operative (aneurysm repair)
2) Gut wall loses structural integrity
3) Allows translocation of luminal contents
What are the 2 symptoms of acute intra-abdominal infection?
1) Abdominal pain and tenderness
2) Shock
When does an intraperitoneal abscess commonly present?
A late complication - several months after pre-disposing factor
What are the 2 main reasons for post-operative intra-abdominal infection?
1) Seeding at operation
2) Anastomotic leak
How is the incidence of post operative infection through seeding at operation reduced?
Incidence reduced with bowel preparation/ prophylactic Abx
Hepatobiliary infections are caused by what mechanism?
Translocation across a lumen
What is cholecystitis?
Inflammation of the gall bladder wall
Is bacterial infection always the cause of cholecytitis?
No, can be chemical inflammation
Bacterial infection may be the cause or result of cholecystitis
What is cholecystitis associated with?
Obstruction of the cystic duct - gall stones or other causes such as malignancy, surgery, parasitic worms - very occasionally no obstruction
What is emphysematous cholecystitis?
More severe, get intramural gas in gallbladder wall
What are the 3 main parts of presentation of cholecystitis?
1) Fever
2) Right upper quadrant pain
3) Mild jaundice
What is empyema of the gall bladder?
Frank pus in the gallbladder which is a complication of cholecystitis
What are the 3 extra components to the presentation of empyema of the gall bladder in addition to those of cholecystitis?
1) Severe pain
2) High fever
3) Chills and rigors
What is cholangitis?
Inflammation/infection of the biliary tree
What is the cause of cholangitis?
Same as causes of cholecysitis - mainly obstruction of common bile duct, can follow instrumentation (eg. ERCP)
What are the 3 main components of presentation of cholangitis?
1) Fever (rigors)
2) Jaundice
3) Right upper quadrant pain
Presentation may be non specific
What are the 5 routes of infection causing pyogenic liver abscess?
1) Biliary obstruction
2) Direct spead from other intra-abdominal infections
3) Haematogenous - from mesenteric infection via hepatic portal vein, from systemic intravascular infection via hepatic artery
4) Penetrating trauma
5) Idiopathic
What is an intra-peritoneal abscess, how are they classified?
Localised area of peritonitis with build-up of pus, classified according to anatomical sites eg. subphrenic, subhepatic, paracolic, pelvic etc.
What are the 6 predisposing factors to intra-peritoneal abscess?
1) Perforation
2) Cholecystitis
3) Mesenteric ischaemia/bowel infarction
4) Pancreatitis/ pancreatic necrosis
5) Penetrating trauma
6) Postoperative anastomotic leak
How does an intra-peritoneal abscess present?
Non specific presentation - sweating, anorexia, wasting, high swinging pyrexia
What are the 5 clinical signs of a subphrenic abscess?
1) Pain in shoulder on affected side
2) Persistent hiccup
3) Intercostal tenderness
4) Apparent hepatomegaly (liver displaced downwards)
5) Ipsilateral lung collapse with pleural effusion
What are the 2 main clinical signs of a pelvic abscess?
1) Urinary frequency
2) Tenesmus - a continual or recurrent urge to empty the bowels
Amoebic abscesses are commonly caused by what bacteria?
Entamoeba histolytica
A hyatid cyst is caused by what pathogen?
Echinococcus granulosus
How is ileo-caecal TB commonly diagnosed?
By CT scan
In what 2 abdominal organs, other than the liver can abscesses commonly occur?
Pancreatic and splenic abscesses
What is spontaneous bacterial peritonitis?
Infected ascetic fluid but no obvious perforation or reason for the infection
What are the 2 most common aerobic GNB found in the gut flora which causes intra-abdominal infection?
1) Enterobacteriacae - predominantly E.coli
2) Pseudomonas spp
What are the 2 most common anaerobic GNB found in the gut flora which cause intra-abdominal infection?
1) Bacteroides spp
2) Prevotella spp
What are the 2 most common aerobic GPC found in the gut flora which cause intra-abdominal infection?
1) Enterococcus spp
2) Milleri-group streptococci
What is the main anaerobic GPB found in the gut flora which cause intra-abdominal infection?
clostridium spp
What bacteria are liver abscesses commonly caused by, does it always involved normal GI flora?
Usually polymicrobial - may be sterile (hard to grow anaerobes)
Infections secondary to haematogenous spread or trauma may not involve normal GI flora
Hepatobiliary tract infections usually involve flora from where?
Lower GI flora, despite duodenal origin
What 3 blood tests are common in intra-peritoneal infection and what do they normally show?
1) FBC: neutrophils/neutropenia
2) CRP: raised
3) LFTs: abnormal in hepatobiliary disease
What are 3 common imaging techniques in the diagnosis of intra-abdominal infection?
1) CXR - consolidation, pleural effusion adjacent to infected areas
2) Abdominal US - shows abd masses, free fluid, dilated bile ducts
3) Abdominal CT scan - higher definition that US
What are the 3 common samples to test and 3 common procedures in microbiological investigations in intra-abdominal infection?
1) Blood
2) Peritoneal fluid
3) US/CT guided drainage fluid
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1) Microscopy
2) Culture
3) Sensitivity testing
What is the treatment for an intraperitoneal abscesses? 3
1) CT/US guided
2) Surgical (multiocular abscesses)
3) Combined with antimicrobial therapy
