constipation Flashcards
what is constipation
reflects pelvic dysfunction or increased transit time
passage <=2 bowel motions/wk, often passed with difficulty, straining, or pain and sense of incomplete evacuation
epidemiology of constipation
female more
constipation and rectal bleeding =
cancer
constipation, distension and active bowel sounds =
stricture/GI obstruction
constipation and menorrhagia =
hypothyroidism
History qns for pt with constipation
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
investigations for constipation
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
general causes of constipation
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
anorectal disease causes of constipation
especially if painful
anal or colorectal cancer
fissures, strictures, herpes
rectal prolapse
proctalgia fugaz
mucosal ulceration/neoplasia
pelvic muscle dysfunction/levator ani syndrome
intestinal obstruction causes of constipation
colorectal ca
strictures - Crohn’s
pelvic mass - fetus, fibroids
diverticulosis - rectal bleeding is a more common presentation
pseudo-obstruction
metabolic/endocrine causes of constipation
hypercalcaemia
hypothyroidism
hypokalaemia
porphyria
lead poisening
drugs that cause constipation
opiates - morphine/codeine
anticholinergics - tricyclics
iron
some antiacids eg with aluminium
diuretics - furosemide
CCB
neuromuscular causes of constipation
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
management of constipation
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
bulking agents
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
stimulant laxatives
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
stool softeners
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
osmotic laxatives
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
what do you give if normal treatment doesnt help
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
