constipation

Question 1

what is constipation

Answer 1

reflects pelvic dysfunction or increased transit time

passage <=2 bowel motions/wk, often passed with difficulty, straining, or pain and sense of incomplete evacuation

Question 2

epidemiology of constipation

Answer 2

female more

Question 3

constipation and rectal bleeding =

Answer 3

cancer

Question 4

constipation, distension and active bowel sounds =

Answer 4

stricture/GI obstruction

Question 5

constipation and menorrhagia =

Answer 5

hypothyroidism

Question 7

History qns for pt with constipation

Answer 7

freq, nature and consistency of stools

blood or mucus in stools

is there diarrhoea alternatimg with constipation (eg IBS)

has there been a recent change in bowel habit

do they digitate the rectum or vagina to pass stool

askl about diet and drugs

Question 8

investigations for constipation

Answer 8

PR exam - even if referring

refer if signs of colorectal Ca (weight loss, pain, anaemia), abdo mass, PR blood, IDA

no tests in young, mildly affected pt - threshold reduces with age

Bloods: FBC, ESR, UE, Ca, TFT

colonoscopy - if suspected colorectal malignancy

transit studies, anorectal physiology, biopsy for Hischprung’s are occaisionally needed

Question 9

general causes of constipation

Answer 9

poor diet, lack of exercise

poor fluid intake/dehydration

IBS

old age

post-op pain

hospital env - reduced privacy, bed pan

chronic laxative abuse

idiopathic slow transit

idiopathic megarectum/colon

Question 10

anorectal disease causes of constipation

Answer 10

especially if painful

anal or colorectal cancer

fissures, strictures, herpes

rectal prolapse

proctalgia fugaz

mucosal ulceration/neoplasia

pelvic muscle dysfunction/levator ani syndrome

Question 11

intestinal obstruction causes of constipation

Answer 11

colorectal ca

strictures - Crohn’s

pelvic mass - fetus, fibroids

diverticulosis - rectal bleeding is a more common presentation

pseudo-obstruction

Question 12

metabolic/endocrine causes of constipation

Answer 12

hypercalcaemia

hypothyroidism

hypokalaemia

porphyria

lead poisening

Question 13

drugs that cause constipation

Answer 13

opiates - morphine/codeine

anticholinergics - tricyclics

iron

some antiacids eg with aluminium

diuretics - furosemide

CCB

Question 14

neuromuscular causes of constipation

Answer 14

from slow transit because decreased propulsive activity:

• spinal or pelvic nerve injury eg trauma/surgery
• aganglionosis (Chagas’ disease, Hirschsprung’s disease)
• systemic sclerosis
• diabetic neuropathy

Question 15

management of constipation

Answer 15

reassurance

drink more, diet (high fibre, bjut may cause bloating and not work), exercise

only use drugs if lifestyle fails

try med for short periods only

meds:

• bulking agents
• stimulant laxatives
• stool softeners
• osmotic laxatives

stimulant (eg Senna) +- bulking agent is cheaper and more effective than lactulose

Question 16

bulking agents

Answer 16

increase faecal mass = stimulate peristalsis

take with plenty of fluid

take a few days to work

CI - difficulty swallowing, GI obstruction, colonic atony, faecal impaction

bran powder with food - may hinder absorption of dietary trace elements if taken with every meal

Ispaghula husk eg 1 Fybogel sachet after meal, mix with water

Methylcellulose, eg Celevac® 3–6 tablets/12h with ≥300mL water.

Sterculia, eg Normacol® granules, 10mL sprinkled on food daily

Question 17

stimulant laxatives

Answer 17

increase intestinal motility so dont use in intestinal obstruction or acute colitis

avoid prolongued use - can cause colonic atony

abdo cramps important SE

pure stimulants: bisacodyl tablets (5–10mg at night) or suppositories (10mg in the mornings) or senna (2–4 tablets at night)

docusate sodium and dantron have stimulant and softening actions

glyceral suppositories act as a rectal stimulant

sodium picosulfate (5-10mg at night) is a potent stimulant

Question 18

stool softeners

Answer 18

useful when managing painful anal conditions eg fissure

archalis oil enemas lubricate and soften impacted faeces

liquid parafin should not be used for a prolongued period - SE: anal seepage, lipoid pneumonia, malabsorption of fat soluble vitamins

Question 19

osmotic laxatives

Answer 19

retain fluid in the bowel

lactulose,

• a semisynthetic disaccharide,
• produces osmotic diarrhoa of low fecal pH that discourages growth of ammonia producing organisms
• useful in hepatic encephalopathy (initial dose - 30-50mL/12h) SE - bloating

macrogol

magnesium salts (eg magnesiym hydroxide, magnesium sulfate) useful when rapid bowel evacuation needed

sodium salts (Microlette and Micralax enemas) avoided - cause Na and water retention

phosphate enemas useful for rapid bowel evacualtion before procedures

Question 20

what do you give if normal treatment doesnt help

Answer 20

prucalopride is an elective 5HT4 agonist with prokinetic properities

lubiprostone is a Cl channel activator that increases intestinal fluid secretion

linaclotide is a guanylate cyclase-c agonist that increases fluid secretion and decreases visceral pain

behaviour therapy, habit training +- sphincter biofeedback