Constipation

Question 1

Definition of constipation

Answer 1

absent or infrequent defaecation and retention of faeces within colon and rectum

or difficult evacuation of faeces

Question 2

What is obstipation

Answer 2

intractable constipation refractory to management with permanent loss of function

Question 3

What is dyschezia

Answer 3

difficult/painful defecation  usually associated with rectal, anal or perineal pathology

Question 4

What are the two types of megacolon

Answer 4

Hypertrophic: consequence of colonic obstruction, may be reversible
Dilated megacolon = end-stage colonic dilation resulting in permanent loss of function

Question 5

What nervous systems are involved in defecation and how

Answer 5

Rectosphincteric reflex using parasympathetic centres
+ conscious control via pudendal nerve to control the sphincters

Question 6

What is the gastrocolic reflex

Answer 6

Where gastric stretch and the entry of products of digestion into the small intestine triggers the urge to defecate

Question 7

Categories of obstructive causes of being unable to defecate

Answer 7

Luminal e.g FBs, indigestible material, impacted faeces

Intramural; neoplasia, stricture

Extralumina: displaced pelvic fractures, marked sublumbar lymphadenopathy

Question 8

Neuromuscular causes of being unable to defecate

Answer 8

Smooth muscle disorders e.g idiopathic megacolon
Spinal cord pathology e.g Manx tail deformity, tail pulls, cauda equina, lubosacral disease
Neuropathis e.g truama, neuplasia

Question 9

What drugs could change ability to defecate

Answer 9

Opioids due to slowing motility

Question 10

What things might make defecation painful

Answer 10

• Degenerative joint disease
• Lumbosacral stenosis
• Proctitis, colitis
• Rectal masse/FBs
• Anal sacculitis
• Perianal fistulae
• Bite wounds

Question 11

Why are cats more commonly presented with constipation

Answer 11

higher incidence of idiopathic megacolon, RTA (which could cause pelvic fracture and displacement), CKD

Question 12

Which dog breed is prone to perianal fistulae

Answer 12

GSD

Question 13

Why can we actually see some diarrhoea in constipation cases

Answer 13

Because the firm stuck faeces causing the colon to secrete mucus and water which passes around the blocked faeces

Question 14

What do we use rectal exam for in constipation investigation

Answer 14

To confirm constipation of faeces extending into rectum
Check for pain in anorectal area
Check for obstructive lesions in anorectal area

Question 15

What systemic diseases might be involved in constipation

Answer 15

Dehydration, hypokalaemia, hypercalcaemia

Hypothyroidism, nutritional hyperparathyroidism due to affecting muscle functoin

CKD in cats

Question 16

What might we look for on blood tests in constipation assessment

Answer 16

CKD, hypercalcaemia
T4/TSH for hypothyroidism

+ can look at dehydration as a consequence of constipation

Question 17

What ratio of colon to L5 vertebral body length is highly suggestive of megacolon

Answer 17

> 1.48

Question 18

What is the use of contrast radiography in constipation case

Answer 18

To delineate colon and identify mass lesions
May do -ve contrast with air or +ve with barium

Question 19

Symptomatic treatment for constipation

Answer 19

Rehydration: IVFT if hospitalised + hypokalaemia correction; water fountains etc if not in hostpiral

Diet
Laxatives
(also enemas, manual evacuation, pro-kinetics)

Question 20

Dietary modification with constipation

Answer 20

High quality easily digestible
Can add fibre

Soluble fibre good to provide SCFAs for colonic nutrition, binding water
e.g psyllium containing diets

Insoluble fibre promotes stretch and motility but can worsen impaction

Question 21

What type of laxative is most commonly used

Answer 21

Osmotic agents e.g lactulose
(start with low dose and titrate to effect)

Question 22

What is in a micralax enema

Answer 22

Sodium citrate to act as an osmotic laxative, glycerol lubricant and sodium lauryl sulfoacetate to increase penetration

Rectal suppository; works in 20-30 mins
Don’t repeat

Question 23

How much warm water to use for enema

Answer 23

5-10ml/kg
Want to dehydrate faeces

Question 24

Why do we avoid sodium phopshate enemas in cats/small dogs

Answer 24

risk of fatal hypernatraemia, hyperphosphataemia and hypocalcaemia

Question 25

What prokinetic might we use with constipation and when is it contraindicated

Answer 25

Cisapride (5-HT4 agonist) Do not use with obstruction cases

Question 26

How to do manual evacuation of faeces

Answer 26

GA + rehydrate with EVFT and enemas to soften faeces Gentle transbadominal manipulation to break up faecal mass and milk faeces into the rectum May take several procedures over a few days

Question 27

Surgical management of constipation

Answer 27

= subtotal colectomy; resection of dilated and amotile colon Recurrence in 30%

Question 28

What is idiopathic megacolon

Answer 28

Common cause of constipation in cats; some kind of generalised colonic smooth muscle dysfunction Progressive disease leading to recurrent contipation and obstipation Start with medical management but often becomes refractory and needs subtotal colectomy

Question 29

What must we differentiate idiopathic megacolon from

Answer 29

Obstructive causes e.g hypertrophic megacolon because this is initially reversible