W4 L1 - Lower GI therapeutics Flashcards
Diarrhoea – definition and diagnosis
- Change in bowel habit
- Substantially more frequent andlooserstools than usual
- World Health Organization 2017 - “the passage of three ormoreloose or liquid stools per day (or more frequent passagethan isnormal for the individual)”
- Consistency more significant than frequency
Diarrhoea can be further categorised as:
Acute - < 14 days
Persistent - > 14 days but less than 28 days
Chronic > 28 days
Not a disease but a sign of underlying problem
which types of stools will form due to diarrhoea in the Bristol Stool Chart
5,6,7
Pathophysiology of diarrhoea
- Increased osmotic load in gut lumen
- Increase in secretion
- Inflammation of intestinal lining
- Increased intestinal motility
- More than one mechanism can cause diarrhoea
Major mechanisms behind diarrhoea
- Increased osmotic load in gut lumen – This occurs when non-absorbed substances (e.g., lactose in lactose intolerance, certain laxatives) draw water into the intestines, leading to osmotic diarrhoea.
- Increase in secretion – Excessive secretion of electrolytes and water into the intestinal lumen (e.g., due to bacterial toxins like cholera or E. coli) causes secretory diarrhoea.
- Inflammation of intestinal lining – Conditions like infections, inflammatory bowel disease (IBD), or celiac disease can damage the intestinal mucosa, leading to exudative diarrhoea (with mucus, blood, or pus).
- Increased intestinal motility – Disorders like irritable bowel syndrome (IBS) or hyperthyroidism can speed up gut transit time, reducing water absorption and resulting in diarrhoea.
Acute diarrhoea - causes
- Adults – approx. 1 episode per year
- Children < 5 – 1-3 episodes per year
- Usually due to infection or ingestion of toxins
- Infection:
Bacteriale.g.Campylobacter, Escherischia coli, Salmonella
Virusese.g.rotavirus or norovirus - Other causes drugs, parasites, anxiety
- Notifiable diseases:
Dysentery
Food poisoning
Most cases – self-limiting and resolve within 72 hours
Travellers diarrhoea
- Diarrhoea experienced by travellers or holiday makers
- Consider destination, age, diet
- Early onset, usually within first few days of trip
- Symptoms as per acute diarrhoea but can also havebloodydiarrhoea (dysentery)
- Usually resolve within 7 days
- Causes include:
EnterotoxigenicEscherichia coli(ETEC),Campylobacter
Salmonella
EnterohaemorrhagicE coliandShigella,
Viruses, protozoa and helminths - Some infectionse.g.giardiasis and amoebic dysentery can causepersistent or recurrent diarrhoea or systemic complications
- Antibiotic prophylaxis rarely recommended
- Hygiene, food and drink advice
Chronic diarrhoea
- Recurrent or persistent diarrhoea
- Many potential causes including:
Irritable bowel syndrome (IBS)
Inflammatory bowel disease (IBD)
Malabsorption syndromese.g.coeliac disease
Metabolic diseasee.g.diabetes, hyperthyroidism
Laxative abuse
Symptoms – acute diarrhoea
- Loose or liquidstools
- Increased frequency – 3 or more times per day
- Abdominal cramping
Flatulence - Mild abdominal tenderness
- Usually rapid in onset
Diagnosis - Questioning of symptoms
Ask about:
- Stool frequency
- Naturee.g.blood, mucus
- Occurrence – isolated or recurrent
- Duration
- Onset – how quickly developed
- Timing
- Diet and food
- Recent travel
- Medication – lots of medicines can cause diarrhoea
Ask about signs of dehydration
Mild signs:
Tiredness, nausea, light-headed, loss/no appetite (anorexia)
Moderate signs:
Dry mouth, sunken eyes
Decreased urine output, feeling thirsty
Decreased skin turgor (pinch test)
Aim to identify who needs referral and how quickly
When to refer (adults)
- Symptoms:
> 72 hours (3 days) in healthy adults
> 48 hours (2 days) in elderly
> 24 hours (1 day) if diabetic - Associated severe vomiting and fever
- Recent travel to tropical/subtropical climate
- Blood or mucus in stools
- History of change in bowel habit (especially if > 40)
- Severe pain/rectal pain
Suspected adverse drug reaction (ADR)
- Alternating diarrhoea and constipation in elderly
– could befaecal impaction
- Weight loss
Recent hospital treatment or antibiotic treatment
- Evidence of dehydration (or unable to drink fluids)
- Steatorrhoea (fatty stools -looser, smellier and paler in colour, may float)
Treatment of acute diarrhoea
- Most cases - self-limiting and resolve within 2- 4 days
- Stay at home, rest and let it “run its course”
- Can give treatments for symptomatic relief
- Primary aim is to prevent dehydration and
re-establish normal fluid balance - First line treatment:
Oral Rehydration Therapy/Solution (ORT/ORS)
Oral Rehydration Therapy
- Generallycontain:
Sodium and potassium to replace essential ions
Citrate and/or bicarbonate to correct acidosis
Glucose or another carbohydratee.g.rice starch - Can be recommended for patients of any age
- Number of different preparations available
- Sachets that are dissolved in water – make up torecommended volume
- Usually dose is 200-400ml after very loose motion
- Diabetic – monitor blood glucose levels carefully
Treatment of acute diarrhoea
Can also give treatments that alter gut motility if staying at home and resting impractical or inconvenient
Options include:
- Loperamide
- Morphine (low dose in combination with other treatment)
- Diphenoxylate
- Adsorbents e.g. bismuth subsalicylate, kaolin
- Antibiotics (if appropriate)
Loperamide
- Synthetic opioid analogue - µ (mu) opioid receptoragonist
- Direct action on opiate receptors in the gut wall
- Reduces propulsive peristalsis - increasing intestinal transit time andenhancing resorption of water and electrolytes
- Increases the tone of the anal sphincter - helps reducefaecalincontinence and urgency
- Extensive first-pass metabolism therefore little reachessystemic circulation
contraindications of loperamide
- Contra-indications:
Active ulcerative colitis
Antibiotic associated colitis
Conditions where inhibition of peristalsis should beavoided e.g. acute flare of Crohn’s
Conditions where abdominal distension develops - Avoid:
Bloody/suspected inflammatory diarrhoea
Significant abdominal pain
Side-effects include abdominal cramps and dizziness
MHRA alert – serious cardiac adverse reactions (high doses - abuse/misuse)
Other treatments
- Morphine
Direct action intestinal smooth muscle
Morphine content per recommended dose of products availableOTC for diarrhoea ranges 0.5-1mg - ? effective - Diphenoxylate
Synthetic derivative of pethidine
Available as combination product – co-phenotrope - Adsorbents
Adsorb microbial toxins and micro-organisms
Kaolin (Kaolin and Morphine)
Bismuth subsalicylate (Pepto-Bismol liquid) - Antibiotics
Stool sample should betakenand causative organismidentified before antibiotic given
General management of diarrhoea
- Plenty of clear fluids
- Avoid drinks high in sugar
- Avoid milk and milky drinks
- Eat light, easily digested food
Note- Diarrhoea can reduce absorption of some medicines so itis important to check their medication history and adviseaccordingly
Constipation – definition and diagnosis
Defaecation that is unsatisfactory because of infrequent stools, difficult stool passage, or seemingly incomplete defaecation
- Passage of hard stoolsless frequently thannormal
- Typicallyless than threebowel movements inone week
- Affects people of all ages
- More common in:
Women, particularly if pregnant
Older people
stool types for constipation on the Bristol Stool Chart
1 and 2
Constipation - pathophysiology
- Large intestine
Removes water and salts from colon
Dries and expels faeces - In constipation – increased water resorption
leads to harder stools more difficult to pass
Reminder - The large intestine plays a crucial role in absorbing water and electrolytes from undigested food, forming stool, and facilitating its expulsion. Normally, peristaltic movements push stool toward the rectum while maintaining a balance between water absorption and stool consistency (refer back to learning at start of semester for further detail).
In constipation, the movement of stool through the colon slows down (delayed colonic transit), leading to increased water resorption from the faecal matter. As a result:
The stool becomes harder, drier, and more compact, making it difficult to pass.
Reduced motility or obstruction may contribute to further stool retention.
This can lead to straining, discomfort, bloating, and in severe cases, complications like faecal impaction or hemorrhoids.
Constipation causes
- Functional (idiopathic)
No anatomical or physiological cause known - Secondary
Induced byparticular conditionor medicine - Non-medical factors e.g. fibre, lifestyle, environment
Medical conditions (predisposing)
Medications
Non-medical factors which pre-dispose to constipationinclude
Inadequate fluid intake - Less water in the colon results in dry stools.
Inadequate dietary fibre - Low fibre intake reduces stool bulk.
Dieting
Changes in lifestyle
Suppressing the urge to defecate
Medical conditions predisposing:
Coeliac disease
Depression
Diabetes
GI obstruction
Irritable bowel syndrome
Parkinson’s disease
Hypercalcaemia
Hypokalaemia
Hypothyroidism
Constipation symptoms
- Abdominal discomfort and distension
- Abdominal cramping
- Bloating
- Nausea
- Difficulty passing stool
- Specks of blood due to straining (bright red
specks in toilet or on tissue)
Diagnosis - Questioning of symptoms
- Ask about:
Usual bowel habit (compare current to “normal”)
Stool frequency and appearance
Naturee.g. blood mixed in stool, black, tarry stool, mucus
Occurrence – isolated or recurrent
Pain on defecation
Duration
Onset
Diet and food
Recent travel
Medication – lots of medicines can cause constipation
Medical history
When to refer (adults)
Red flagsinclude:
Unexplained weight loss
Blood in stools
Rectal bleeding
Family history of colon cancer or IBD
Signs of obstruction
Nausea, vomiting or abdominal pain
Age > 40 and marked change in habit with no obvious cause
> 14 days duration
Tiredness
Alternating with diarrhoea (?IBS)
Pain on defecation which may cause person to suppress reflex
Treatment
Aims:
Restore normal frequency defecation
Achieve regular, comfortable defecation
Avoid laxative dependence
Relieve discomfort
Non-pharmacological:
Consider primary cause
Diet, increase fluid intake and lifestyle measures including exercise
Pharmacological:
Four main types of laxatives:
Bulk-forming
Stimulant
Osmotic
Faecal-softening
Bulk-forming laxatives
- Increase faecal mass through water binding to stimulateperistalsis
- Onset action – 1-3 days
- Maintain good fluid intake
- Can be used long-term in people prone to constipation
- Examples include:
Ispaghula husk
Methylcellulose (also acts as softener)
Stimulant laxatives
- Increase intestinal motility via muscle contractions
- Work within a 6-12 hours (take before bedtime, will work bymorning)
- Can cause abdominal cramps
- Avoid prolonged use – diarrhoea, fluid and electrolyteimbalance
- Examples include:
Senna
Bisacodyl
Osmotic laxatives
- Work within colonic lumen to retain and draw water intointestine by osmosis
- Maintain good fluid intake
Macrogel powders –1-3 days to work - Lactulose (semi-synthetic disaccharide) – 2-3 days to work
- Phosphate enema or suppository – 15-30 minutes to work
- Magnesium hydroxide – 3-6 hours to work
Faecal softening
- Stimulate peristalsis by increasing faecal mass: act to lowersurface tension and allow water and fats to penetrate faeces
- Docusate sodium acts as faecal softener and stimulant –works within 1-3 days
- Glycerol suppository – works within one hour
- Arachis oil enema – works within 30 minutes. Not to be usedif nut allergy
Irritable bowel syndrome (IBS)
- Chronic condition
Poorly understood
Functional bowel disorder (no abnormality) - At least 6 months:
abdominal pain
bloating
change in bowel habit -diarrhoea, constipation or combination of both
Diagnosis – exclusion of other causes
Function bowel disorder
No specific anatomical, biochemical ormicrobiological factors
Motility dysfunction
Diet
Genetics
Psychological factors
Hyperactivity of small intestine and colon in response to food and parasympathomimetic drugs
IBS Symptoms
- Symptoms for 6 months
- Characterised by:
Abdominal pain or discomfort
(relieved be defecation/passing wind)
Altered bowel habits – constipation or diarrhoea
Bloating - Constipation predominant, diarrhoea predominant or both
Diagnosis - Questioning of symptoms
Similaras per diarrhoea and constipation
In particular:
Age (usually in < 45 years age)
Periodicity - ? Episodic
Abdominal pain – presence, location and nature
Bowel function
When to refer (adults)
See also red flags for diarrhoea and constipation
Blood in stools
High temperature (fever)
Nausea and/or vomiting
Severe abdominal pain
Age > 40 and marked change in habit with no obvious cause
Steatorrhoea(fatty stools -looser, smellier and paler in colour,may float)
Treatment
- Treatment aimed at symptomatic relief
- Number of different medications can be used
- No “gold standard” as symptoms vary
- Treatments include:
Dietary changes and exercise
Antispasmodicse.g.mebeverine, hyoscine, peppermint oil
Anti-diarrhoeale.g.Loperamide
Laxativese.g.bulk-forming, stimulant, osmotic
Probiotics
Treatment
Antispasmodics
- Smooth muscle relaxant
- Mebeverine is commonest prescribed drug for IBS in the UK
- Modified release capsule – 200mg twice daily
- Tends to be well tolerated
- Peppermint oil capsules can also be used – taken three timesdaily
