Surgery - Change in bowel habit, rectal bleeding and related symptoms

Question 1

Change in bowel habit, rectal bleeding and related symptoms

Differential diagnosis of change in bowel habit

Answer 1

Carcinoma of colon, rectum or anus

Diverticular disease

Irritable bowel syndrome

Crohn’s disease of small or large bowel

Ulcerative colitis

Drug effects, e.g. codeine phosphate, iron, laxative abuse

Reduction in fibre content of diet

Parasitic infestations, e.g. giardiasis

Following acute bacterial or parasitic colitis

Changes in resident bacterial flora, e.g. antibiotic-associated diarrhoea

Malabsorption syndromes

Thyrotoxicosis

Question 2

Change in bowel habit, rectal bleeding and related symptoms

Differential diagnosis of change in bowel habit

Constipation

Answer 2

Severe constipation arises for four main reasons:

• Incomplete bowel obstruction, e.g. faecal impaction, an obstructing carcinoma or stricture in the bowel wall, or occasionally an extrinsic lesion such as ovarian cancer
• Loss of peristalsis, e.g. acutely due to drugs such as narcotics, antidepressants or iron, chronic diverticular disease, chronic laxative abuse
• Inadequate fibre intake or poor fluid intake, which decrease faecal volume and prolong intestinal transit time
• In bed-bound patients, multiple factors including immobility, diet, inadequate fluid intake, drug effects

Question 3

Change in bowel habit, rectal bleeding and related symptoms

Differential diagnosis of change in bowel habit

Diahorrea

Answer 3

• Chronic diarrhoea is caused by irritation or inflammation of small/large bowel.
• The inflammatory bowel diseases (ulcerative colitis and Crohn’s disease) are important diagnoses.
• Chronic parasitic infestations of large bowel with amoebae or of small bowel with Giardia lamblia are easily overlooked.
• In areas where these diseases are not endemic, patients may give a history of foreign travel.
• Chronic diarrhoea may follow an acute attack of Salmonella or other coliform infection.
• Less commonly, a blind loop of small bowel remaining after bypass surgery becomes colonised with gut flora, causing changes in intraluminal metabolism (blind loop syndrome).
• The most common diagnosis in diarrhoea after intestinal infection is irritable bowel syndrome.

Question 4

Change in bowel habit, rectal bleeding and related symptoms

Changes in the nature of the stool

Answer 4

• Stools normally brown due to the presence of urobilin, a breakdown product of bile. In biliary obstruction, bilirubin fails to reach the gut and stools become pale. In jaundice, often described as ‘putty’ or ‘clay-coloured’.
• Stools can be pale when contain excess fat ie in malabsorption syndromes. In coeliac disease (gluten enteropathy) the stool is often loose and offensive.
• In fat malabsorption, the lipid rich stools tend to float and are difficult to flush away (steatorrhoea).
• Undigested food in the stool indicates malabsorption or a ‘short-circuit’ in the bowel due to previous bowel resection or a fistula between bowel loops.
• Note that this can be normal when the diet is extremely high in fibre.