64. Constipation Flashcards
Causes of constipation.
a) Children
b) Teenagers/young adults
c) Older people
d) Inpatients
a) Functional (behavioural - 95%), dietary, congenital (Hirschsprung, CF)
b) Functional (IBS), diet (inadequate fluids/fibre), drugs (e.g. opiates), endocrine/ metabolic (e.g. hypothyroid), obstruction (adhesions, IBD, diverticula) or psuedo-obstruction (ileus), painful defecation (haemorrhoids, anal fissures)
c) Immobility, frailty, diet, drugs, colorectal Ca, neurological (cord compression)
d) Immobility, frailty, drugs, lack of toileting privacy, postoperative pain/ileus
Drugs that can cause constipation
- Opiates
- Anticholinergics (e.g. hyoscine, TCAs)
- Loperamide, mebeverine
- Ondansetron*
- Verapamil
- Iron
- Statins
*So useful for chemotherapy-induced nausea + diarrheoa; whereas metoclopramide (which also has some affinity for 5-HT3) is a prokinetic that can cause diarrhoea
Endocrine/metabolic causes of constipation
- Hypothyroidism
- Hypercalcaemia
- Hypokalaemia
- Porphyria.
- Lead poisoning
Management of constipation: conservative measures
- Stop/reduce offending medications if appropriate
- Treat any treatable causes (e.g. hypercalcaemia)
- Ensure good fluid intake
- Ensure good dietary fibre intake
- Ensure good bladder emptying
- Mobilise patient
Laxative types.
- with examples
https://bnf.nice.org.uk/treatment-summary/constipation.html
- Softeners (e.g. sodium docusate)
- Stimulants (e.g. senna, bisacodyl)
- Bulk-formers (e.g. methycellulose, bran powder)
- Osmotic (e.g. lactulose, macrogol/PEG)
Red flag symptoms in constipation
a) Infants
b) Children
c) Adults
a) Failure to pass meconium, symptoms from birth, ribbon stools, anal stenosis, leg weakness/locomotor delay, faltering growth
b) Faltering growth, weakness, delay, abdominal distension
c) - Neurology (weakness, bilateral sciatica, UMN/LMN signs, loss of anal tone or sensation)
- Acute GI: vomiting, peritonism, distension
- Chronic GI: PR bleed, weight loss, mass, mucus discharge, tenesmus
Definition of constipation.
a) 3 types
b) Other possible features (especially in children)
a) - Infrequent stools (<3 times weekly), or
- Difficult stool passage (with straining or discomfort), or
- Incomplete defecation (+/- abdominal/rectal mass)
b) - Overflow incontinence
- With-holding behaviours
- Stools blocking the toilet
Investigating constipation.
- Bedside: PR exam; ?bladder scan
- Blood tests: FBC, CRP/ESR, UEs, Ca2+, TFTs.
- Imaging: erect CXR, CT, sigmoidoscopy/colonscopy and biopsy of abnormal and normal mucosa, Barium enema
- Special investigations (eg, transit studies, anorectal physiology) which are occasionally indicated.
Drug management of constipation in adults.
a) 1st line, plus advice and contraindications?
b) If stools remain hard - add/switch to…?
c) If stools are soft but difficult to pass or there is tenesmus - add/switch to …?
d) When should drugs be gradually stopped?
e) If there is impaction - measures
a) Bulk-former (eg ispaghula): advise good fluids intake. - Contraindications: intestinal obstruction or opioid-induced constipation (use stimulant like senna instead)
b) Osmotic laxative (e.g. macrogol/PEG or lactulose)
c) Stimulant (e.g. senna)
d) Once the person is producing soft, formed stool without straining at least three times per week
e) Oral laxatives first line as above. If no effect:
- Suppositories - bisacodyl (stimulant) for soft stools; glycerol for hard stools
- Enemas - docusate (softener and stimulant)
- Manual evacuation if necessary
Management of constipation in children.
a) Initial measures
b) Drugs
a) - Confirm constipation (e.g. infrequent stool, hard rabbit dropping stools, large stool blocking toilet, overflow incontinence, retentive behaviours/posturing)
- Behavioural (toilet training - diaries, reward system), fluids and fibre
b) 1st line: osmotic laxative - macrogol (PEG)
- 2nd line: stimulant/softener (sodium picosulfate, bisacodyl, docusate, senna)
Chronic laxative use may cause what bowel condition?
Melanosis coli- lipofuscin deposits causing black pigmentation of the colon
- asymptomatic
