GI 4 Flashcards
What is a polyp?
A protrusion above the epithelium which is a type of tumour which can be benign or malignant
What are the three types of colorectal tumours?
1) Polyps
2) Adenomas
3) Adenocarcinomas
What are the differential diagnoses for a colonic polyp?
- Adenoma (most polyps)
- Serrated polyp
- Polypoid carcinoma
- Other
What is a colonic adenoma?
A benign tumour which is not invasive and does not metastasise. It must be removed as it is premalignant (precursor for colorectal carcinoma)
What is Dukes staging?
Predicts prognosis for carcinoma:
1) Dukes A: confined by muscular propria
2) Dukes B: through the muscular propria
3) Dukes C: metastatic to lymph nodes
Describe the distribution of colorectal carcinomas.
- 75% are left-sided (rectum, sigmoid, descending)
- 25% are right-sided (caecum, ascending)
What is the pattern of spread for colorectal carcinoma?
- Local invasion: mesorectum, peritoneum, other organs
- Lymphatic spread: mesenteric nodes
- Haematogenous: liver and distant sites
What are two inherited colorectal cancer syndromes?
1) Hereditary non-polyposis coli (HNPCC)
2) Familial adenomatous polyposis (FAP)
What is hereditary non-polyposis coli (HNPCC)?
- Late onset, autosomal dominant
- Defect in DNA mismatch repair
- Right sided tumours
- < 100 polyps
- Mucinous tumours
- Crohn’s like inflammatory response
- Associated with gastric and endometrial carcinoma
What is familial adenomatous polyposis (FAP)?
- Early onset, autosomal dominant
- Defect in tumour suppression, mutation in FAP gene
- Throughout the colon
- > 100 polyps
- No specific inflammatory response
- Associated with desmoid tumours and thyroid carcinoma
What are diverticular diseases of the large intestine?
When sacs/bulges form in the all of the large intestine, which are related to a low fibre diet and high intraluminal pressure. Often asymptomatic unless complications occur.
What are some complications of diverticular disease in the large intestine?
- Inflammation
- Rupture
- Abscess
- Fistula
- Massive bleeding
What are some of the causes of large bowel ischaemia?
- CVD/CHD (atrial fibrillation)
- Embolus
- Shock
- Vasculitis
- Atherosclerosis of mesenteric vessels
What is the histopathology of ischameic colitis?
- Withering of crypts
- Pink smudgy lamina propria
- Fewer chronic inflammatory cells
What are the complications of ischaemia of the large intestine?
- Massive bleeding
- Rupture
- Stricture
What is antibiotic-induced “pseudomembranous” colitis?
In patients on broad-spectrum antibiotics, C diff is selected out and toxins A and B attacks the endothelium -> massive diarrhoea and bleeding.
What is collagenous colitis?
Thickened basement membrane associated with intra-epithelial inflammatory cells.
What is the histopathology of lymphocytic colitis?
- No chronic architectural changes in crypts
- Intraepithelial lymphocytes are raised
- No thickening of the basal membrane
What is radiation colitis?
- Chronic active or inactive colitis with Telangectasia
- Bizarre stromal cells and vessels
- May be other complications of immunosuppression if also on chemotherapy
What is acute infective colitis?
Infection, may be the onset of intestinal bowel disease
What is colonic angiodysplasia?
- Submucosal lakes of blood
- Obscure cause of rectal bleeding
- Usually right side of the colon
- Diagnosed with angiography or colonoscopy
What is signed volvulus?
- When the bowel twists on mesentery and may become gangrenous
- Diagnosed by plain X-ray abdominal or rectal contrast
- Treated with flatulus tube or surgical resection
What is enterobacteriaceae?
A large family of Gram-negative bacteria which can cause a wide range of illnesses e.g. UTI and gastroenteritis; not all are truly pathogenic (some opportunistic).
Describe the microbiology of enterobacteriaceae.
- 53 genera (26 cause infection)
- Gram negative
- Non-spore forming
- Grow on a variety of solid media
- Ferment sugars
- Facultative anaerobes mostly
- Increasing resistance
What is MALDI-TOF mass spectrometry?
- Low cost machine which analyses protein composition of bacterial cell wall using a database
- Discriminates between highly genetically similar organisms with identical 16s rRNA
- Difficult to discriminate some species such as Salmonella vs E. coli
What is the normal flora of the GI tract?
- Mouth: strep viridans, Neisseria sp, anaerobes, candida sp, staphylococci
- Stomach/duodenum: usually sterile, few candida and staphylococci
- Jejunum: few coliforms and anaerobes
- Colon: large number of coliforms, anaerobes and Enterococcus faecalis
- Bile ducts: sterile
What are the symptoms of C diff overgrowth?
- Diarrhoea, sometimes bloody
- Abdominal pain
- In severe cases -> pseudomembranous colitis and bowel perforation
Describe the laboratory diagnosis for C diff infection.
1) Screening test for presence of organism (GDH)
2) If positive text for presence of toxin (A&B)
If 1 - = -; if 1 + and 2 + = +; if 1 + and 2- = indeterminate, repeat, if indeterminate again -> clinical decision
What is rotavirus?
- Commenest cause D&V in <3, mild in adults severe in immunocompromised children
- Person-person spread (directly/indirectly)
- Mild-severe diarrhoea, no blood
- Self-limiting, lasts one week
- Dehydration and post-infection malabsorption
- Diagnosis by PCR test on faeces
- Treat by oral rehydration
- Oral vaccine at 2 & 3 months but not past 24 weeks
What is norovirus?
- D&V bug (2-4 days), affects all people all times
- 5 billion viruses per gram of faeces
- Faeceal-oral (droplet) or person-person
- Survival on fomites for days/weeks
- Short incubation <24 hrs
- Diagnosed by faeces specimen/vomit swab for PCR test
- Treatment with rehydration (esp kids and elderly)
- Asymptomatic shedding up to 48 hrs post symptoms
What are the standard infection control precautions for diarrhoea in hospital?
- Side rooms with own toilets/commodes
- Cohort nursing
- Close wards to new admission
- Regular cleaning and disinfection of the ward
What is sepsis?
Life-threatening organ dysfunction caused by a dysregulated host response to infection
What is septic shock?
A subset of sepsis with circulatory and cellular/metabolic dysfunction associated with a higher risk of mortality
What are the local signs of intra-abdominal infection?
Pain, tenderness, guarding and blood PR in some
What are the systemic signs of intra-abdominal infection?
Fever, chills/rigors, nausea/vomiting, constipation/diarrhoea, malaise, anorexia
What is SIRS?
Systemic inflammatory response syndrome (SIRS) is an exaggerated defense response of the body to a noxious stressor to localize and then eliminate the endogenous or exogenous source of the insult; if presumed or confirmed infectious process = sepsis
What are the four criteria for SIRS (>/=2 confirms SIRS)?
1) Body temperature >38 or <36
2) Heart rate >90bpm
3) RR >20 or PaCO2 <32mmHg
4) WCC > 12000 units/l or <4000 units/l
What are the signs of septic shock?
Sepsis plus signs of at least one acute organ dysfunction e.g. renal, respiratory, hepatic, haematological, CNS, unexplained metabolic acidosis or hypotension
What is the protocol for gentamicin prescription?
- Concerns regarding nephrotoxicity (limit use and monitor renal function daily)
- Correct dosing for overweight patients, max of 600mg
- Follow clear exclusion criteria
- Prescribe in once-only section and let the ward pharmacist know
What steps should be completed within 3 hours of a patient surviving sepsis?
1) Measure lactate level
2) Obtain blood culture prior to antibiotics
3) Administer broad spectrum antibiotics
4) Administer 30ml/kg crystalloid for hypotension or lactate levels >/= 4mmol/l
What steps should be completed within 6 hours of a patient surviving sepsis?
5) Apply vasopressors for hypotension that does not respond initial fluid resuscitation to maintain MAP >/= 65
6) If persistent arterial hypotension despite volume resuscitation or initial lactate >/4 mmol/l: measure CVP and SCVO2
7) Remeasure lactate if initial lactate was elevated
What are the risk factors for GI infections?
- Malnutrition (micronutrient) deficiency
- Closed/semi-closed communities
- Exposure to contaminated food/water/travel
- Winter congregating/summer floods
- Age <5, not breast feeding
- Older age
- Acid suppression/immunosuppression/microbiome/genetics
What bacterial factors are a risk for GI infections?
- Adherence/attachment to the GI mucosa
- Cellular invasion
- Production of exotoxins
- Changes in epithelial cell physiology
- Loss of brush border enzymes and/or cell death
- Increased intestinal motility, net fluid secretion, influx of inflammatory cells, and/or intestinal haemorrhage
What is dysentry?
- Inflammation of the intestine, particularly the colon, causing diarrhea associated with blood and mucus;
- e.g. shigella and campylobacter
- Generally associated with fever, abdominal pain, and rectal tenesmus (sense of incomplete defaecation).
What is gastroenteritis?
- An illness caused by eating food contaminated with micro-organisms, toxins, poisons etc
- Bacteria, viruses, parasites
- Usually have gastrointestinal symptoms (diarrhoea, abdominal pain, vomiting)
What GI infections have the shortest incubation periods (1-6 hours)?
1) Bacillus cereus - starchy foods, heat resistant spores, profuse vomiting, gram positive bacillus
2) Staphylococcus aureus - gram positive coccus, in room temperature food, acts on vomiting centre in brain, abdominal pain
What physical examinations should you conduct on a returned traveller?
- Fever
- Rash
- Hepatosplenomegaly/lymphadenopathy
- Insect bites
- Wounds
What might a fever in a returned traveller indicate?
- Respiratory tract infections (pneumonia/influenza)
- Traveller’s diarrhoea
- Malaria
- Enteric fever (typhoid/paratyphoid fever)
- Arboviruses - dengue/zika/chikungunya
What is acute traveller’s diarrhoea?
- 3 loose stools in 24 hours
- Associated with self reported fever in 30%
- Typically enterotoxigenic E. coli (maybe campylobacter, salmonella, shigella or amoebic diarrhoea)
- Cruise ships - norovirus and rotavirus
- 50% of cases no pathogen identified
What are the two types of acute traveller’s diarrhoea?
1) Bloody diarrhoea (dysentery) – Bacterial causes including E.coli 0157, plus Amoebic colitis
2) Profuse watery diarrhoea – Cholera – toxin mediated disease often associated with outbreaks – refugee camps
What are the investigations for acute traveller’s diarrhoea?
1) Stool culture
2) Stool wet prep on recently passed stool for amoebic trophozoites
What is enteric fever?
- Typhoid or paratyphoid fever
- Most common in those returning from Indian subcontinent and SE Asia
- Often in people visiting family or friends
- Incubation period 7-18 days (though occasionally up to 60 days)
What are the symptoms of enteric fever?
Fever, headache, constipation/diarrhoea, dry cough
What are the complications of enteric fever?
- GI bleeding
- GI perforation
- Encephalopathy
- Bone and joint infection
What causes pre-hepatic (haemolytic) jaundice and fever?
- Malaria
- HUS as a complication of diarrhoeal illness
- Sickle cell crisis triggered by infection
What causes hepatic jaundice and fever?
- Hepatitis A and E – acute (occasionally Hepatitis B)
- Leptospirosis – Weils diseases (Icteric, haemorrhagic and renal failure)
- Malaria
- Enteric fever
- Rickettsia (scrub typhus, Rocky Mountain spotted fever etc)
- Viral haemorrhagic fever
What causes post-hepatic jaundice and fever?
- Ascending cholangitis
- Helminths
What investigations should be completed for a traveller with fever/jaundice?
- Malaria blood film and rapid antigen
- Blood film for red cell fragmentation
- FBC/UE/LFT/coagulation
- Blood cultures
- USS abdomen
- Serological testing for viruses
What is amoebiasis?
- Entamoeba histolytica, a protozoa
- Faecal-oral spread, strong association with poor sanitation
- Asymptomatic carriage (chronic cyst shed in stool)
- Symptoms: abdominal dysentery
What are the symptoms of amoebiasis?
- Abdominal dysentery
- Abdominal pain
- Fever
- Bloody diarrhoea / colitis (can perforate)
- Toxic and unwell, abdominal tenderness, peritonism
What are the investigations for amoebiasis?
- Stool microscopy for trophozoites or cysts (distinguish between E. histolytica and E. dispar)
- AXR - ?toxic megacolon
- Endoscopy for biopsy (not if evidence of toxic dilatation)
What is an amoebic liver abscess?
- Entamoeba histolytica
- Incubation period 8-20 weeks
- More common in men
- Subacute presentation over 2-4 weeks; fever, sweats, abdominal pain
What are the symptoms of an amoebic liver abscess?
- Fever, sweats
- Upper abdominal pain
- Sometimes history of GI upset (dysentery)
- Hepatomegaly
- Point tenderness over right lower ribs
What are the investigations for an amoebic liver abscess?
- Abnormal LFTs
- CXR – raised right hemi-diaphragm
- USS/CT scan
- Serology
- Stool microscopy - often negative (E. histolytica looks similar to E.dispar)
What is giardiasis?
- Giardia intestinalis (lamblia), flagellated protozoa
- Invades duodenum and proximal jejunum
- Faecal-oral spread (contaminated water most commonly)
- Incubation usually around 7 days
What is the typical presentation for giardiasis?
- Watery, malodorous diarrhoea
- Bloating, flatulence
- Abdominal cramps
- Weight loss
What are the investigations for giardiasis?
- Stool microscopy for cysts (often difficult), in developed world PCR tests
- OGD for duodenal biopsy (rarely necessary)
What are helminth infections?
- Occur in gut/tissue
- Often associated with eosinophilia
- Often diagnosed by the adult worm passed or the eggs in stool
What are some common helminths?
- Cestodes (tapeworms)
- Nematodes (roundworms)
- Trematodes (flukes)
