Constipation

Question 1

What is constipation?

Answer 1

Infrequent passage of stool, generally defined as ≤ 3 bowel movements per week

Question 2

What are the types of constipation?

Answer 2

(By course) acute or chronic
(By etiology) Primary constipation (functional constipation): constipation in the absence of an identifiable medical disorder
Secondary constipation: constipation due to a medical disorder or medication

Question 3

What are some causes of primary constipation?

Answer 3

Poor diet and insufficient exercise

Question 4

What are some causes of secondary constipation?

Answer 4

(Gastrointestinal) Colorectal carcinoma, IBS, Diverticulosis/Diverticulitis
(Neurological) Diabetic neuropathy, Hirschsprung disease, stroke, Parkinson’s
(Endocrine) Hyperthyroidism, diabetes mellitus, electrolyte imbalance (e.g. hypokalaemia, hypercalcemia)
(Connective tissue disease) Scleroderma
Systemic lupus erythematosus, amyloidosis
(Drug-induced) Opioid analgesics, iron supplement, calcium-channel blockers

Question 5

How is constipation diagnosed?

Answer 5

(Mainly Clinical diagnosis) using Rome IV criteria, unless red flag or secondary causes suspected
(Physical exam) DRE looking for haemorrhoids, rectal cancer, anal wink and sphincter tone
(Lab investigations) Hypokalaemia, hypercalcemia, diabetes mellitus
(Abdominal X-ray)
(Colonoscopy) Mechanical obstruction

Question 6

What are some red flag symptoms of constipation?

Answer 6

(Children) Absence of meconium within 48 hours 
Fever 
Family history of Hirschsprung disease
Severe abdominal distension 
(Adults) Family history of colorectal cancer or IBS
Weight loss
>50 yrs 
Blood in stool / Iron deficiency anemia

Question 7

What are the treatments for constipation?

Answer 7

(In adults) High fibre, exercise, hydration if it persists:
Osmotic laxatives, if persistent then stimulant laxatives
(Infants 2 wks to 6 months) Reassurance as constipation common, reassess in 2-4 weeks. Offer polyethylene glycol (osmotic laxitive) if persistent
(Infants >6 months) Polyethylene glycol + lifestyle changes

Question 8

What are examples of osmotic laxatives and how do they work?

Answer 8

Polyethylene glycol, glycerin, magnesium hydroxide, lactulose
Increase osmotic pressure in lumen → draws in water, causing distension → increases motility

Question 9

What are examples of stimulant laxatives and how do they work?

Answer 9

Senna, bisacodyl
Stimulation of nitric oxide-mediated epithelial cell secretion of electrolytes into the colonic lumen
Or Myenteric neuronal depolarization → colon contractions

Question 10

What are examples of emulsifying laxatives and how do they work?

Answer 10

Docusate
Emulsification (i.e., integration of water and fat) of stool → softening of stool → easier passage through the intestinal tract

Question 11

What are examples of bulk-forming laxatives and how do they work?

Answer 11

Methylcellulose, Psyllium husks, Polycarbophil
Bulk-forming laxatives are indigestible → increase water absorption in the intestinal lumen → stretching of the bowel wall → stimulation of peristalsis

Question 12

What are some of the complications of constipation?

Answer 12

Fecal incontinence 
Fecal impaction 
Anal fissures
Hemorrhoids
Megacolon