Constipation

Question 1

What is constipation?

Answer 1

Constipation reflects pelvic dysfunction or increased transit time.
Passage of ≤2 bowel motions/week, often passed with difficulty, straining or pain, and a sense of incomplete evacuation.
Female:male ~ 2:1.
Worried about major pathology, e.g. constipation + rectal bleeding = cancer; constipation + distension + active bowel sounds = stricture/GI obstruction; constipation + menorrhagia = hypothyroidism.

Question 2

What specific questions should you ask about constipation?

Answer 2

Ask about frequency, nature, and consistency of stools.
Is there any blood or mucus in/on the stools?
Is there diarrhoea alternating with constipation, e.g. IBS.
Has there been any recent change in bowel habit?
Is she digitating the rectum or vagina to pass stool?
Ask about diet and drugs.
PR exam is essential.

Question 3

What tests should you order for patients presenting with constipation?

Answer 3

None in young, mildly affected patients.
Threshold for investigation diminishes with age.
Triggers include: weight loss, abdominal mass, PR blood, iron deficiency anaemia.
Bloods: FBC, ESR, U&E, Ca2+, TFT.
Colonoscopy: if suspected colorectal malignancy.
Transit studies, anorectal physiology, biopsy for Hirschprung’s are occasionally needed.

Question 4

What is the treatment for constipation?

Answer 4

Often reassurance, drinking more, and diet/exercise advice is all that is needed.
Treat causes.
A high fibre diet is often advised, but may cause bloating without helping constipation.
Only use drugs if these measures fail, and try to use them for short periods only.
Often, a stimulant such as senna ± a bulking agent is more effective and cheaper than agents such as lactulose.
Bulking agents- increase faecal mass, stimulating peristalsis.
Stimulant laxatives- increase intestinal motility.
Stool softeners- enemas lubricate and soften impacted faeces.
Osmotic laxatives- retain fluid in the bowel.

Question 5

Causes of constipation: general

Answer 5

Poor diet ± lack of exercise.
Poor fluid intake/dehydration.
IBS.
Old age.
Post-operative pain.
Hospital environment (embarrassed).

Question 6

Causes of constipation: anorectal disease

Answer 6

-- Especially if painful --
Anal or colorectal cancer.
Fisures, structures, herpes.
Rectal prolapse.
Proctalgia fugax.
Mucosal ulceration/neoplasia.
Pelvic muscle dysfunction/levator ani syndrome.

Question 7

Causes of constipation: intestinal obstruction

Answer 7

Colorectal carcinoma.
Strictures (e.g. Crohn's disease).
Pelvic mass (e.g. foetus, fibroids).
Diverticulosis (rectal bleeding is a commoner presentation).
Pseudo-obstruction.

Question 8

Causes of constipation: metabolic/endocrine

Answer 8

Hypercalcaemia.
Hypothyroidism (rarely presents with constipation).
Hypokalaemia.
Porphyria.
Lead poisoning.

Question 9

Causes of constipation: drugs

Answer 9

Opiates, e.g. morphine, codeine.
Anticholinergics, e.g. tricyclics.
Iron.
Some antacids, e.g. with aluminium.
Diuretics, e.g. furosemide.
Calcium channel blockers.

Question 10

Causes of constipation: neuromuscular

Answer 10

– Slow transit from decreased propulsive activity –
Spinal or pelvic nerve injury, e.g. trauma, surgery.
Aganglionosis (Chagas’ disease, Hirschprung’s disease).
Systemic sclerosis.
Diabetic neuropathy.

Question 11

Causes of constipation: other causes

Answer 11

Chronic laxative abuse (rare- diarrhoea is commoner).
Idiopathic slow transit.
Idiopathic megarectum/colon.