Intra-abdominal infections

Question 1

What is the definition of intra-abdominal infection?

Answer 1

Presence of micro-organisms in normally sterile sights within the abdominal cavity eg. the peritoneal cavity or hepatobiliary tree

Question 2

Is gastro-enteritis an intra-abdominal infection?

Answer 2

No as the bowel lumen is a non sterile sight

Question 3

Are normal flora found in the stomach?

Answer 3

No - the stomach is considered to be sterile

Question 4

Why is the proximal small intestine relatively free of microorganisms, what few organisms are found?

Answer 4

Growth is inhibited by bile

A few aerobic bacteria and Candida spp

Question 5

What is the flora of the small intestine?

Answer 5

Same as that of large intestine

Question 6

The large intestine has mainly anaerobic bacteria, what 2 aerobic bacteria are also found?

Answer 6

1) Enterobacteriacae (enteric GNB, coliforms)

2) Gram-positive cocci (mainly enterococci)

Question 7

What are the 3 main sources of intra-abdominal infection?

Answer 7

1) Gastrointestinal contents
2) Blood
3) External

Question 8

What are the mechanisms of intra-abdominal infection, each is typical of what kind of infection?

Answer 8

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

Question 9

What are the 3 possible reasons for translocation of organisms across a wall causing intra-abdominal infection?

Answer 9

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

Question 10

What are the 2 possible reasons for translocation along a lumen causing intra-abdominal infection?

Answer 10

1) Blockage - cholecystitis, cholangitis, hepatic abscess

2) Iatrogenic - instrumentation (eg. endoscopic retrograde cholangiopancreatography)

Question 11

Perforated appendix is mainly a disease of what group of people?

Answer 11

Children and young adults

Question 12

What is the main symptom of perforated appendix?

Answer 12

Severe, generalised pain

Question 13

What condition can perforated appendix lead to?

Answer 13

Shock

Question 14

How does a perforated appendix occur?

Answer 14

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

Question 15

Perforated appendix can localise to form what?

Answer 15

An appendix mass

Inflamed appendix with adherent covering of omentum and small bowel

Question 16

What are diverticula?

Answer 16

Herniations of mucosa/submucosa through muscular layer in the sigmoid and descending colon

Question 17

How common are asymptomatic diverticula?

Answer 17

50% in over 70 years

Question 18

What are the 3 main complications of diverticula disease?

Answer 18

1) Diverticulitis
2) Perforation
3) Pericolic abscess

Question 19

Is intraperitoneal or bloodstream infection a common complication of bowel cancer?

Answer 19

Intraperitoneal and/or bloodstream infection is an infrequent complication of bowel cancer

Question 20

Bowel cancer is particularly associated with what 2 infections?

Answer 20

1) Clostridium septicum

2) Streptococcus gallolyticus (formerly S bovis) bloodstream infection

Question 21

What is intra-abdominal infection in bowel cancer caused by?

Answer 21

Loss of bowel wall integrity due to abnormal malignant tissue

Question 22

Why does ischaemia lead to translocation of bowel contents cause intra-abdominal infection?

Answer 22

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

Question 23

What are the 2 symptoms of acute intra-abdominal infection?

Answer 23

1) Abdominal pain and tenderness

2) Shock

Question 24

When does an intraperitoneal abscess commonly present?

Answer 24

A late complication - several months after pre-disposing factor

Question 25

What are the 2 main reasons for post-operative intra-abdominal infection?

Answer 25

1) Seeding at operation | 2) Anastomotic leak

Question 26

How is the incidence of post operative infection through seeding at operation reduced?

Answer 26

Incidence reduced with bowel preparation/ prophylactic Abx

Question 27

Hepatobiliary infections are caused by what mechanism?

Answer 27

Translocation across a lumen

Question 28

What is cholecystitis?

Answer 28

Inflammation of the gall bladder wall

Question 29

Is bacterial infection always the cause of cholecytitis?

Answer 29

No, can be chemical inflammation | Bacterial infection may be the cause or result of cholecystitis

Question 30

What is cholecystitis associated with?

Answer 30

Obstruction of the cystic duct - gall stones or other causes such as malignancy, surgery, parasitic worms - very occasionally no obstruction

Question 31

What is emphysematous cholecystitis?

Answer 31

More severe, get intramural gas in gallbladder wall

Question 32

What are the 3 main parts of presentation of cholecystitis?

Answer 32

1) Fever 2) Right upper quadrant pain 3) Mild jaundice

Question 33

What is empyema of the gall bladder?

Answer 33

Frank pus in the gallbladder which is a complication of cholecystitis

Question 34

What are the 3 extra components to the presentation of empyema of the gall bladder in addition to those of cholecystitis?

Answer 34

1) Severe pain 2) High fever 3) Chills and rigors

Question 35

What is cholangitis?

Answer 35

Inflammation/infection of the biliary tree

Question 36

What is the cause of cholangitis?

Answer 36

Same as causes of cholecysitis - mainly obstruction of common bile duct, can follow instrumentation (eg. ERCP)

Question 37

What are the 3 main components of presentation of cholangitis?

Answer 37

1) Fever (rigors) 2) Jaundice 3) Right upper quadrant pain Presentation may be non specific

Question 38

What are the 5 routes of infection causing pyogenic liver abscess?

Answer 38

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

Question 39

What is an intra-peritoneal abscess, how are they classified?

Answer 39

Localised area of peritonitis with build-up of pus, classified according to anatomical sites eg. subphrenic, subhepatic, paracolic, pelvic etc.

Question 40

What are the 6 predisposing factors to intra-peritoneal abscess?

Answer 40

1) Perforation 2) Cholecystitis 3) Mesenteric ischaemia/bowel infarction 4) Pancreatitis/ pancreatic necrosis 5) Penetrating trauma 6) Postoperative anastomotic leak

Question 41

How does an intra-peritoneal abscess present?

Answer 41

Non specific presentation - sweating, anorexia, wasting, high swinging pyrexia

Question 42

What are the 5 clinical signs of a subphrenic abscess?

Answer 42

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

Question 43

What are the 2 main clinical signs of a pelvic abscess?

Answer 43

1) Urinary frequency | 2) Tenesmus - a continual or recurrent urge to empty the bowels

Question 44

Amoebic abscesses are commonly caused by what bacteria?

Answer 44

Entamoeba histolytica

Question 45

A hyatid cyst is caused by what pathogen?

Answer 45

Echinococcus granulosus

Question 46

How is ileo-caecal TB commonly diagnosed?

Answer 46

By CT scan

Question 47

In what 2 abdominal organs, other than the liver can abscesses commonly occur?

Answer 47

Pancreatic and splenic abscesses

Question 48

What is spontaneous bacterial peritonitis?

Answer 48

Infected ascetic fluid but no obvious perforation or reason for the infection

Question 49

What are the 2 most common aerobic GNB found in the gut flora which causes intra-abdominal infection?

Answer 49

1) Enterobacteriacae - predominantly E.coli | 2) Pseudomonas spp

Question 50

What are the 2 most common anaerobic GNB found in the gut flora which cause intra-abdominal infection?

Answer 50

1) Bacteroides spp | 2) Prevotella spp

Question 51

What are the 2 most common aerobic GPC found in the gut flora which cause intra-abdominal infection?

Answer 51

1) Enterococcus spp | 2) Milleri-group streptococci

Question 52

What is the main anaerobic GPB found in the gut flora which cause intra-abdominal infection?

Answer 52

clostridium spp

Question 53

What bacteria are liver abscesses commonly caused by, does it always involved normal GI flora?

Answer 53

Usually polymicrobial - may be sterile (hard to grow anaerobes) Infections secondary to haematogenous spread or trauma may not involve normal GI flora

Question 54

Hepatobiliary tract infections usually involve flora from where?

Answer 54

Lower GI flora, despite duodenal origin

Question 55

What 3 blood tests are common in intra-peritoneal infection and what do they normally show?

Answer 55

1) FBC: neutrophils/neutropenia 2) CRP: raised 3) LFTs: abnormal in hepatobiliary disease

Question 56

What are 3 common imaging techniques in the diagnosis of intra-abdominal infection?

Answer 56

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

Question 57

What are the 3 common samples to test and 3 common procedures in microbiological investigations in intra-abdominal infection?

Answer 57

1) Blood 2) Peritoneal fluid 3) US/CT guided drainage fluid - 1) Microscopy 2) Culture 3) Sensitivity testing

Question 58

What is the treatment for an intraperitoneal abscesses? 3

Answer 58

1) CT/US guided 2) Surgical (multiocular abscesses) 3) Combined with antimicrobial therapy