Lower GI Flashcards
What do adhesive enterotoxigenic bacteria do?
Adhere to brush border, increase cAMP leading to CL- and Na+ secretion followed by water
Which drugs can cause diarrhoea?
Antibiotics- superinfection, alter lower GI flora
Clindamycin associated with pseudomembranous colitis
Orlistat- pancreatic lipase inhibitor
Causes fatty diarrhoea (steatorrhea)
Misoprostol- via cAMP
PPIs- Infection
Digoxin toxicity, acarbose, metformin and iron salts
What is oral rehydration therapy?
Solution of electrolytes to replace the electrolytes lost in diarrhoea e.g dioralyte
Must be isotonic
Glucose allows transport of Na via a symporter
Which antibiotic is often used for traveller’s diarrhoea?
Cirprofloxacin
What are anti-motility agents (opioids)?
Codeine and loperamide
Used for symptomatic relief
In infection can reduce clearance of infective organisms from the GI tract
Reduce tone and peristaltic movements of GI muscle by inhibiting presynaptically (via u-opioid receptors) the release of acetylcholine
What is presynaptic inhibition?
Reduces the release of Ach
Reduces motility and increases transit time
Promotes reabsorption of water
Where is loperamide largely retained?
In the gut
Does not penetrate BBB and has an efficient enterohepatic cycling
What does clonidine do?
Alpha2-adrenoceptor agonist
Cause presynaptic inhibition via a2 receptor leading to constipation
What is dicycloverine?
An antimuscarinic
What do tricyclic antidepressants do?
Constipating
Side effect through antagonism of muscarinic receptors
What drugs induce constipation?
Opioids
Tricyclic antidepressants
Antimuscarinic drugs
Diuretics- due to dehydration
What are osmotic laxatives?
Lactulose
Enters the colon unchanged and converted by bacteria to lactic and acetic acid- raise fluid volume osmotically
What are magnesium laxatives?
Osmotic effect
Mg2+ also release cholecystokinin which increases GI motility
What are bulking agents laxatives?
Ispaghula
Methylcellulose
What are stimulant laxatives?
Senna extracts, enter colon metabolised to anthracene derivatives which stimulates GI activity
Dantron- irritant
How is IBS treated?
Lactulose or loperamide
Antispasmodic agents
Amitriptyline
What are antispasmodic agents?
Antimuscarinics: inhibit parasympathetic activity
Mebeverine: direct relaxant of GI smooth muscle- probably acting as a phosphodiesterase inhibitor
What does amitriptyline (TCA) do?
Low doses widely used + effective
Provide some pain relief
Antimuscarinic effects
Alters the sensitivity of sensory nerves in low GIT
What is inflammatory bowel disease?
Encompasses both ulcerative colitis and Crohn’s disease
Causes are unclear and include genetics, microbial, environmental aetiologies
What are clinical features of inflammatory bowel disease?
Diarrhoea Faecal incontinence Rectal bleeding, bloody diarrhoea Passing of mucus Cramping pains Weight loss In Crohn's disease there may be mouth ulcers and anal skin tags
What complication can occur in Chrohn’s disease?
Malabsorption leading to deficiencies in folate and iron associated with iron-deficiency anaemia respectively
What complication can occur in ulcerative colitis?
Blood loss can lead to iron deficiency anaemia
What can inflammatory bowel disease be associated with?
Arthritis
Iritis
Uveitis
Increased risk of thromboembolism
What’s Crohn’s disease?
Can affect any part of the GI tract, but mostly the ileum and/or colon are involved
T-lymphocytes are activated and lead to transmural inflammation and the extensive involvement may lead to the formation of fistulae
What’s the treatment for Crohn’s disease?
5-aminosalicylates- mainstay for UC, less clear for Crohn;s
Sulphasalazine- metabolised in colon by gut flora to 5-ASA and sulphapyridine
Masalazine- pH changes yield 5-ASA
5-ASA- inhibits leukotriene and prostanoid formation, scavenge free radicals, decrease neutrophil chemotaxis
What else is used to treat Crohn’s disease?
Corticosteroids
Prednisolone (anti-inflammatory, immunosuppressive actions)
Budesonide (poorly absorbed few side effects)
Probiotics
Fish oils
Immunosuppressants
Which immunosuppressants are used to treat Crohn’s disease?
Azathiopine
Cyclosporine
Methotrexate
Infliximab (monoclonal antibody tumour necrosis factor (TNF-a) in severe disease)
What counselling do patients need who are taking mesalazine (5-ASA)?
Risk of blood dyscrasia Report: Sore throats Fevers Easy bruising or bleeding
What side effects are aminosalicylates associated with?
Rashes
Headaches
Diarrhoea
What lifestyle advice should you give to people with Crohn’s disease?
Stop smoking
Exacerbated by NSAIDs
Exacerbated by alcohol
If there is a narrowing which foods should be avoided that can form a bolus?
Nuts
Sweetcorn
Raw fruit
popcorn
What’s an elemental diet?
Basic food substances
Amino acids as opposed to proteins
Low fat
Allows correction of micronutrients
What are the side effects of aziothioprine?
Risk of pancreatitis
Requires FBC monitoring (6-8 weeks)
Risk of myelosuppression: bruising and bleeding, infections
What is methotrexate effective in?
Crohn’s disease not in ulcerative colitis
Role in refractory disease and for steroid sparing
What does methotrexate interact with?
Serious interaction with NSAIDs leading to toxicity
Once weekly dose (25 mg i.m or 12.5mg orally)
What needs to be monitored when taking methotrexate?
FBC, renal function, LFT
Report fever/cough (indicate infection due to neutropenia)
Report cough/dyspnoea (indicate pulmonary toxicity)
What happens if you give ciclosporin with steroids?
Increased risk of pneumocystis carinii and prophylactic co-trimoxazole must be used
What is infliximab?
Monoclonal antibody which neutralises the pro inflammatory cytokine TNF-a, which is implicated in Crohn;s disease, possibly via leucocyte recruitment
Risk factor for developing tuberculosis
Infusion reactions are common so carried out in hospital
