Constipation

Question 1

How do you define constipation

Answer 1

• defined as the passage of less than or equal to 2 bowel motions a week often passed with difficulty, straining or pain and a sense of incomplete evacuation

Question 2

What could it mean if you have constipation and rectal bleeding

Answer 2

• cancer

Question 3

What could it mean if you have constipation, distension and active bowel sounds

Answer 3

• stricture

- GI obstruction

Question 4

what could it mean if you have constipation and menorrhagia

Answer 4

• hypothyroidism

Question 5

Name the major causes of constipation

Answer 5

• general
• anorectal disease
• intestinal obstruction
• metabolic/endocrine
• drugs
• neuromuscular (slow transit from decreased propulsive activity)

Question 6

What are the general causes of constipation

Answer 6

• poor diet +- lack of exercise
• poor fluid intake/dehydration
• IBS
• old age
• post-operative pain
• hospital environment (lack of privacy, having to use a bed pan)

Question 7

What are the intestinal obstruction causes of constipation

Answer 7

• colorectal carcinoma
• strictures - e.g. Crohn’s
• pelvic mass - e.g. foetus, fibroids
• diverticulosis (PR bleeding more common presentation)
• pseudo-obstruction

Question 8

What are the drug causes of constipation

Answer 8

• opiates - morphine, codeine
• anticholinergics e.g. TCAs
• iron
• some antacids - with aluminium
• diuretics - e.g. furosemide
• CCBs

Question 9

What are the anorectal disease causes of constipation

Answer 9

• anal or colorectal cancers
• fissures, strictures, herpes
• rectal prolapse
• proctalgia fugax
• mucosal ulceration/neoplasia
• pelvic muscle dysfunction/levator ani syndrome

Question 10

What are the endocrine causes of constipation

Answer 10

• hypercalcaemia
• hypothyroidism
• hypokalaemia
• porphyria
• lead poisoning

Question 11

What are the neuromuscular causes of constipation

Answer 11

• spinal or pelvic nerve injury - e.g. trauma, surgery
• aganglionosis - chugs disease, hirschprung’s disease
• systemic sclerosis
• diabetic neuropathy

Question 12

What are the other causes of constipation

Answer 12

• chronic laxative abuse
• idiopathic slow transit
• idiopathic megarectum/colon

Question 13

What should you ask for history in constipation

Answer 13

• Nature, frequency and consistency of stools
• Blood or mucus in stools
• Diarrhoea alternating with constipation (eg IBS)
• Recent change in bowel habit
• Digitating rectum (or vagina in rectocele) to pass stools
• Ask about diet and drugs
  → DRE essential even when referring (refer if signs of colorectal ca, eg weight loss, pain or anaemia)

Question 14

When do you investigation constipation

Answer 14

• non in young, mild affected patients
• threshold for investigation diminishes with age - triggers include: weight loss, abdominal pain, PR blood, iron deficiency, anaemia

Question 15

What investigations do you use in constipation

Answer 15

• Blood - FBC, ESR, CRP, U&Es, Calcium, TFT
• Colonoscopy - if suspected colorectal malignancy
• other occasionally needed - transit studies, anorectal physiology, biopsy for Hirschprung’s disease

Question 16

what are the management for constipation

Answer 16

• reassurance, drinking more, diet and exercise advice is all that is needed
• treat causes
• high fibre diet - can lead to bloating and might not help constipation
• only use drugs if these measures fail and use them for short periods only
• often a stimulant such as a Senna, and +- a bulking agent is more effective and cheaper than agents such as lactulose

Question 17

How does bulking agents work

Answer 17

• this is when you increase in faecal mass so stimulating peristalsis
• this must be taken with plenty of fluids and may take days to act

Question 18

What are the contraindications of bulking agents

Answer 18

• difficulty in swallowing
• GI obstruction
• colonic atony
• faecal impaction

Question 19

Name some bulking agents

Answer 19

• Bran powder 3.5 2-3 times/d with food – may hinder absorption of dietary trace elements if taken with every meal
• Ispaghula husk eg 1g Fybogel® sachet after a meal – mixed in water and swallowed promptly
• Methylcellulose eg Celevac® 3-6 tablets/12h with ≥300ml water
• Sterculia eg Normacol® granules 10ml sprinkled on food daily

Question 20

How do stimulant laxatives work

Answer 20

increased intestinal mobility so do not use in intestinal obstruction or acute colitis

Question 21

Why should you avoid the use of stimulant laxatives

Answer 21

• avoid prolonged use as it may cause colonic atony

Question 22

What are the side effects of stimulant laxatives

Answer 22

• abdominal cramps

Question 23

Name some examples of stimulant laxatives

Answer 23

• Bisacodyl tablets (5-10mg at night) or suppositories (10mg in morning)
• Senna (2-4 tablets at night)
• Docusate sodium and Dantron – have stimulant and softening action
• Glycerol suppositories – act as rectal stimulant
• Sodium picosulfate (5-10mg at night) – potent stimulant

Question 24

when are stool softeners useful

Answer 24

• when managing painful anal conditions such as fissure

Question 25

Name some stool softeners

Answer 25

- Arachis oil enemas – lubricate and soften impacted faeces | - Liquid paraffin – should not be used for prolonged period

Question 26

What are the side effects of stool softeners

Answer 26

- anal seepage - lipid pneumonia - malabsorption of fat soluble vitamins

Question 27

What do osmotic laxatives do

Answer 27

retina fluid in the bowel

Question 28

How does lactulose work

Answer 28

Synthetic disaccharide, produces osmotic diarrhoea of low faecal pH that discourages growth of ammonia-producing organisms

Question 29

what is lactulose useful in

Answer 29

- useful in hepatic encephalopathy

Question 30

What are the side effects of lactulose

Answer 30

bloating

Question 31

name the types of osmotic laxatives

Answer 31

- Lactulose 30-50mL/12h (initial dose) - Macrogel e.g. Movicol - magnesium salts e.g. magnesium hydroxide, magnesium sulfate - sodium salts e.g. microlette and microlax enemas - phosphate eneams