Defecation

Question 1

Bristol Stool Chart

Answer 1

Question 2

What is considered normal regarding frequency of defecation?

Answer 2

3 stools/week – x3 stools/day

Question 3

Explain the normal process of defecation.

Answer 3

Question 4

What are the phases of defecation?

Answer 4

Basal phases 1 and 2

Pre-expulsive phase

Expulsion phase

Termination phase

Question 5

What occurs in basal phase 1 of defecation?

Answer 5

Colonic function - the colon absorbs and contracts providing motility to move the stool from the colon to the rectum.

Question 6

What occurs in basal phase 2 of defecation?

Answer 6

Puborectalis, pelvic floor and anorectal canal are at rest maintaining the anorectal angle.

Internal anal sphincter is relaxed.

Question 7

What occurs in the pre-expulsive phase of defecation?

Answer 7

Defecatory urge, distension of the rectum and pelvic floor due to being filled with faeces.

Relax the pelvic floor muscles and external anal sphincter.

The pressure in the rectum is then greater than in the anorectal canal leading on to expulsion.

Question 8

What occurs in the expulsive phase of defecation?

Answer 8

Voluntary straining increasing intra-rectal pressure.

Pelvic floor tone is inhibited and anal canal relaxes leading to the passage of stool.

Question 9

What occurs in the termination phase of defecation?

Answer 9

Withdrawal of voluntary straining

Absence of rectal distension

IAS tone increased

Closing reflex

Question 10

What can cause incontinence?

Answer 10

Anal sphincter weakness.

Decreased rectal sensation.

Decreased rectal compliance.

Overflow – inhibition of IAS tone.

Idiopathic.

Question 11

What can cause anal sphincter weakness?

Answer 11

• Atraumatic – neurological, infiltrative.
• Traumatic – obstetric injury, iatrogenic, pudendal nerve trauma.
• Other diseases – adjacent structures, fistulae.

Question 12

Iatrogenic

Answer 12

Medically induced trauma e.g from surgery

Question 13

What investigations are carried out in cases of incontinence?

• why?

Answer 13

Anorectal manometer - measures tone and contractility of the anal sphincters.

MRI scans - Looking for abnormalities, growths, fistulae etc.

Flexible sigmoidoscopy.

Question 14

How is constipation clinically defined?

Answer 14

Two or more of:

• Straining during >25% defaecation
• Lumpy/hard stool
• Incomplete evacuation >25% defaecation
• Sensation of obstruction >25% defaecation
• Manual manoevres >25% defaecation
• <3 spontaneous stool/week

Question 15

What is the most common cause of constipation?

Answer 15

>90% have rectocoele and rectal mucosal prolapse

Question 16

What are the treatments available for constipation?

Answer 16

• Rectal irrigation
• Rectopexy
• Rectovaginal septum augmentation
• Medical/conservative

Question 17

What are the causes of constipation?

Dietary:

Motility:

Structural:

Drugs:

Neurological:

Disease:

Endocrine:

Answer 17

Dietary: Lack of dietary fibre / fluid intake.

Motility: Slow-transit, IBS, drugs.

Structural: Colonic carcinoma, Diverticular disease, Hirschprung’s disease.

Anorectal disease (Crohn’s, fissures, haemorrhoids).

Drugs: Opiates, Anticholinergics, Calcium antagonists.

Neurological: MS, Parkinsonisms, cerebrovascular accidents, spinal cord lesions.

Endocrine: Diabetes, hypothyroidism, pregnancy, hypercalcemia.

Depression

Question 18

Which paitents with constipation require prompt investigation?

Answer 18

Middle-aged or elderly patients with a short history or worrying symptoms (rectal bleeding, pain or weight loss) must be investigated promptly, by either barium enema or colonoscopy.

Question 19

Endoanal ultrasound

Answer 19

An Endoanal Ultrasound is a test that allows the doctor to evaluate in depth, using ultrasonography, the different constituents of the wall of the anal canal

Question 20

Defecating proctogram

Answer 20

Defecating proctogram is an examination of the lower bowel and rectum using x-rays. It shows how your rectum functions during the emptying of your bowels. The images obtained will help us understand what is causing your symptoms.