Week 4 - Colon and Associated Disorders Flashcards Preview

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Flashcards in Week 4 - Colon and Associated Disorders Deck (44)
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1
Q

Other than pain, what other clinical features may be associated with appendicitis?

A
  • nausea
  • vomiting
  • anorexia
  • fever
  • bowel habit can vary from diarrhoea to a sensation of constipation
2
Q

Describe strategies that might help to minimise the risk for (or promote the early detection of) colorectal cancer.

A
  • screening (faecal occult blood test and endoscopy if 1st degree relative has had CRC from age 25)
3
Q

Outline the management of irritable bowel syndrome (include potential pharmacological interventions within your discussion)

A
  • reassurance that there is no serious underlying pathology
  • appropriate strategies to manage the constipation and diarrhoea
  • food elimination approaches may be helpful in some cases
  • pharmacological agents (e.g. serotonin-receptor modulators incl. antagonists and agonists, anti-spasmodics)
4
Q

Differentiate a haustral contraction from a mass movement

A

Haustral contractions occur every 30 minutes

  • they are short-lived contractions (mainly in ascending and transverse colon)
  • initiated by ENS when individual haustra fill with food residue

Mass movements occur 3-4 times daily
- they are powerful, prolonged contractile waves that force contents towards rectum

5
Q

Describe four functions of the large intestine

A

Digestion - enteric bacteria ferments indigestible carbohydrates and mucin
Absorption - water, electrolytes (NaCl) and vitamins
Propulsion - contractions to transport faecal matter, towards rectum
Defecation - removal of faecal matter from the body

6
Q

List common aetiologies for both types of diarrhoea.

A

Acute diarrhoea

  • infectious gastroenteritis/enteritis
  • dietary issues
  • adverse drug reactions

Chronic diarrhoea

  • chronic infective diarrhoea
  • intestinal disorders
  • adverse drug reactions
7
Q

Differentiate acute diarrhoea from chronic diarrhoea.

A

Acute diarrhoea

  • sudden of >3 loose stools/day
  • lasts less than 14 days

Chronic diarrhoea
- present for at least 4 weeks

8
Q

Differentiate the terms internal haemorrhoid and external haemorrhoid

A

Internal haemorrhoids - varicosity of the superior rectal vein (proximal to pectinate line)

External haemorrhoids - varicosity affecting the perianal venous plexus (distal to pectinate line)

9
Q

How might the defecation reflex be affected in a patient with cauda equina syndrome?

A

Cauda equina syndrome may involve significant lumbar disc herniation, resulting in compression of a lumbar spinal cord. This may affect signals reaching the sacral nerves below, resulting in an inability to complete the defecation reflex.

10
Q

Summarise the clinical features of irritable bowel syndrome

A
  • abdominal pain or discomfort (R or L iliac region, or hypogastrium)
  • variable bowel habit
  • abdominal distension, excessive flatus and borborygmi
  • nausea, cramping, tenesmus (recurrent inclination to evacuate the bowels)
11
Q

What clinical features might make you suspicious of colorectal cancer?

A
  • constitutional SSx (anorexia, malaise, fever)
  • malignant polyps can ulcerate: bloody or mucoid diarrhoea (distal bowel = frank blood; proximal bowel = occult blood; caecal tumours = asymptomatic until large)
  • lower abdominal pain
  • palpable mass
12
Q

Compare and contrast the following elements of ulcerative colitis and Crohn’s disease:
b) Aetiology

A

UC - undetermined; genetic, immunological and infectious factors are usually involved
CD - strong evidence for autoimmune involvement

13
Q

List two classes of medication that can be used in the management of inflammatory bowel disease. For each class of medication, provide an example and describe the mechanism of action.

A
  • anti-inflammatory agents (e.g. corticosteroids, 5-aminosalicyclic acid)
    5-ASA mechanism = prostaglandin synthesis inhibitor
  • biological agents (anti-TNFa antibodies)
    mechanism = targets and reduces levels of cytokine TNFa
  • immunosuppresants
  • anti-diarrhoeal agents
14
Q

How does the mucosa change at the recto-anal junction? What does this change in cell type reflect?

A

Rectal mucosa is composed of simple columnar epithelium (with a high concentration of goblet cells), whilst anal mucosa is composed of stratified squamous epithelium.

This transition reflects the greater abrasion that this region receives.

15
Q

Define the term constipation

A

Several definitions exist:

  • a bowel movement less frequent than three times a week
  • production of a stool which is hard, difficult to pass or painful
  • consistency is more significant than frequency for diagnosis

Rome III Criteria for Chronic Functional Constipation:

Requires 2 or more of the following features:

  • straining or manual manoeuvres over a 3-month period
  • lumpy/hard stools or if loose stools rare without laxatives
  • sensation of incomplete evacuation or anorectal blockage
  • <3 bowel movements each week
16
Q

Describe the typical pattern of abdominal pain associated with appendicitis. The nature of appendicitis pain usually changes as the disease progresses – why is this the case?

A
  • begins as a vague gastric or peri-umbilical region (T10)
  • increases over 3-4 hours
  • visceral pain is replaced by intense somatic pain in the RLQ
  • this change is mediated by a different neural pathway (thoracoabdominal nerves)
  • this indicates extension of inflammation to parietal peritoneum (somatic nerve supply)
  • the somatic pain is sharp, well-localised and sensitive to stretch
17
Q

What strategies can be used to manage functional constipation?

A
  • increase fibre and water intake
  • introduce gentle exercise
  • drug regime modification
  • address psychological issues (e.g. managing stress)
  • use of biofeedback or neuromuscular retraining
18
Q

Define the term irritable bowel syndrome. How is the disorder diagnosed?

A

It is a functional bowel disorder consisting of abdominal discomfort and constipation or diarrhoea (or an alternation between both). There is no structural abnormality.

IBS is a diagnosis of exclusion (must exclude other pathologies first)

  • stool cultures
  • faecal occult blood test
  • colonoscopy
19
Q

Compare and contrast the following elements of ulcerative colitis and Crohn’s disease:
f) Potential complications

A

UC - toxic megacolon

  • if ulceration is severe enough to affect muscularis
  • results in dilated, atonic section of bowel

CD - chronic fissures, fistula development
- coloenteric, colovesical, colovaginal

20
Q

Summarise the risk factors for colorectal cancer

A
  • dietary factors (low-fibre diets, high-fat diets, diets high in charred red meats)
  • smoking
  • inflammatory bowel disease
  • familiar component (first-degree relative) (familiar adenomatous polyposis
21
Q

Outline the different classes of laxatives. For each class, briefly explain the mechanism of action and provide an example of a medication from that class.

A
  • Bulking Agents (psyllium)
    = increase faecal bulk which stimulates peristalsis
  • Osmotic Laxatives (lactulose) = exerts osmotic effect (draws water to bowel) which increases intraluminal pressure
  • Stool Softeners (docusate) = promote the retention of water in faecal matter
  • Bowel Stimulants (senna) = direct stimulation of nerve endings in colonic mucosa
  • Opioid Antagonists (naloxone) = competitive antagonist at GIT opioid receptors
22
Q

Outline the management of haemorrhoids

A
  • rectal examination
  • sigmoidoscopy/colonoscopy to exclude other causes of bleeding
  • symptom relief (oral or topical preparations to reduce pain and/or inflammation, hydrocortisone combining corticosteroid with local anaesthetic)
  • surgery is required for third and fourth haemorrhoids
23
Q

It is important to recognise situations in which constipation might be due to a sinister cause. Describe features associated with constipation that would warrant special concern and referral.

A
  • onset in middle age or old age
  • per rectal bleeding, melena (dark, offensive-smelling stool), or mucus
  • weight loss, fever, rectal pain, anorexia, nausea, vomiting
  • family history of colorectal cancer
24
Q

Compare and contrast the following elements of ulcerative colitis and Crohn’s disease:
e) Clinical features

A
UC - initial attack is most severe; large volumes of water diarrhoea +/- blood, mucus, pus; may be constipation due to strictures from scar tissue or reflex bowel spasm; lower abdominal pain, tenderness or cramping; proctitis leads to tenesmus
severe epsiodes:
- >20 motions/day
- dehydration, tachycardia
- fever
- anaemia 

CD - depends on site affected, extent and duration of disease; early stages may mimic irritable bowel or even a peptic ulcer; diarrhoea, weight loss, abdominal pain
If colon affect = blood, pus, mucus
If small bowel affected = issues related to malabsorption

25
Q

List five (5) risk factors for constipation

A
  • dietary factors (low in fibre)
  • lifestyle factors (sedentary lifestyle)
  • medication side effects (analgesics, anti-depressants, iron supplements, diuretics)
  • psychological and neurological factors ( chronic stress, ignoring urge to defecate)
  • organic diseases and metabolic problems (diverticular disease, GIT malignancies, inflammatory bowel disease, hypothyroidism)
26
Q

Consider the elements of the defecation reflex – which components of the nervous system are involved in this reflex?

A
  • Requires contribution of spinal column and higher centres
    1. Mass movement of faeces into rectum stimulate visceral afferents (distension)
    2. Initiates a parasympathetic spinal reflex (S2-S4)
    3. Contraction of rectum and relaxation of internal anal sphincter
    4. Message also reaches brain: allows for conscious decision on the relaxer of the external anal sphincter
27
Q

Describe the clinical features of haemorrhoids

A
  • bright red bleeding is common
  • prolapse may be described
  • pain (quality depends on the location… may be dull vs sharp)
28
Q

How would you introduce the large intestine (structure/function/location) in the setting of a lab exam?

A

Structure: The large intestine is comprised of 7 different components, including the caecum, ascending, transverse and descending colon, sigmoid colon, rectum and anal canal. it also has unique structural features include omental appendices, haustra and they lack villi.

Location: The large intestine is located in all four quadrants of the abdomen. It begins as the caecum, attaching to the distal aspect of the ileum of the small intestine, at the ileocaecal junction.

Function: the large intestine plays an important role in absorption of water and electrolytes, propulsion and defecation of faeces. It also plays a minimal role in the digestion of mucin and short-chain fatty acids.

29
Q

Compare and contrast the following elements of ulcerative colitis and Crohn’s disease:
c) Region of the GIT affected

A

UC - rectum and sigmoid colon

CD - terminal ileum, ascending colon and transverse colon

30
Q

Describe three macroscopic features that are unique to the colon

A
  • omental appedices (small, fatty projections that hang from the suface of the colon)
  • teniae coli (longitudinal muscle layer of the muscularis is arranged as three separate, thickened bands)
  • haustra (pocket-like sacs created by the colonic walls)
31
Q

Compare and contrast the following elements of ulcerative colitis and Crohn’s disease:
d) Pathophysiology (including appearance of the characteristic lesion and progression of the disease)

A

UC - inflammation begins at the crypts of large intestine, causing the mucosa to become swollen and hyperaemic (readily bleeds); small erosions form and develop into ulcers (mucosa adopts a ragged appearance); healing with fibrosis leads to pseudopolyp formation (clumps of granulation tissue); oedema and thickening of the muscularis narrows the lumen

CD - inflammation begins in the submucosa and spreads to involve the entire thickness of the intestinal wall; inflammation can affect some regions of the GIT but not others (skin lesions); chronic inflammation leads to the development of granulomas (clusters of modified macrophages); these occur in the gut wall, mesentery and mesenteric lymph nodes; the intestinal wall adopts a cobblestone appearance due to lines of ulceration surrounding mucosal swelling

32
Q

What type of specialised tissue is contained in the appendix? Describe its function.

A

Lymphoid tissue
Immune function - produces and stores lymphocytes; reservoir for beneficial gut bacteria; helps to colonise the gut when needed

33
Q

It is important to recognise situations in which diarrhoea might be due to a sinister cause. Describe features associated with diarrhoea that would warrant special concern and referral.

A
  • severe/worsening diarrhoea in patients >70 years or immunocompromised
  • bloody/mucoid/purulent (containing discharge) diarrhoea
  • diarrhoea accompanied by severe abdominal pain or signs of infection
34
Q

External haemorrhoids are typically more painful than internal haemorrhoids. Referring to nerve supply of the anal canal, explain why.

A

Inferior to pectinate line, the body receives somatic motor and sensory input from pudendal nerve. This is sensitive to pain, touch and temperature.

Hence, external haemorrhoids are typically more painful than internal haemorrhoids. (superior to pectinate line, body is supplied by inferior hypogastric plexus which is sensitive to stretch, only)

35
Q

Outline the arterial supply of the large intestine

A

Caecum - ileocolic artery (SMA)
Appendix - appendicular artery (branch of ileocolic artery)
Ascending colon and hepatic flexure - ileocolic and right colic arteries (SMA)
Transverse colon - middle colic artery (SMA), right colic artery (SMA) and left colic artery (IMA)
Descending and Sigmoid colon - left colic artery (IMA), superior sigmoid arteries (IMA)
Rectum and Anal Canal - superior rectal artery (IMA), middle rectal artery, inferior rectal artery

36
Q

Differentiate the terms diverticulosis and diverticulitis

A
  • diverticulosis (presence of saccular outpouching in the wall of the colon)
  • diverticulitis (when pouches become inflamed in the process)
37
Q

What are extra-intestinal manifestations can occur in both UC and CD

A
  • ankylosing spondylitis
  • biliary tree disorders (e.g. gall stones)
  • renal disorders
  • eye disorders
  • skin disorders
38
Q

List the complications of haemorrhoids

A

Complications:

  • strangulation (irreducible haemorrhoids compressed by anal sphincter = patients with acute pain)
  • thrombosis (clot has developed inside varicose vein) = acute pain, tender swelling +/- infection, ulceration and gangrene
  • healing with fibrosis (can result in skin tags and an increased risk for anal fissures)
  • persistent blood loss (iron deficiency anaemia)
39
Q

Summarise the clinical features of diverticular disease

A
  • most cases are asymptomatic
  • pain and tenderness in left iliac fossa
  • change of bowel habit (constipation alternating with diarrhoea or increasing constipation)
  • acute diverticulitis (severe pain, guarding, rigidity)
  • abscess formation (palpable mass)
40
Q

Describe the basic cross-section of the colonic mucosa. How does it differ to that of the small intestine?

A

Thick mucosa = simple columnar epithelium
Deep crypts compared to rest of GIT
Crypts contain abundant goblet cells (to produce mucous)
NO CIRCULAR FOLDS, VILLI OR BRUSH BORDER (unlike small intestine)

41
Q

Discuss the pathophysiology of appendicitis

A
  1. obstruction of the lumen prevents proper drainage
  2. as mucosal secretions continue, intraluminal pressure increases thereby decreasing mucosal blood flow
  3. hypoxia-induced ulceration promotes bacterial invasion and inflammation
  4. gangrene develops from thrombosis of the luminal blood vessels, followed by perforation of the appendix
42
Q

Compare and contrast the following elements of ulcerative colitis and Crohn’s disease:
a) definition

A

UC - chronic inflammatory disease that causes ulceration of colonic mucosa (usually rectum and sigmoid colon)
CD - chronic inflammatory disorder that can affect any part of the GIT from the mouth to the anus

43
Q

Sum up the pathophysiology of diverticulosis in your own words - how does a diet low in fibre contribute to this disease?

What part of the large intestine is most commonly affected?

A

In the longitudinal muscle layer of the colonic wall, there are varying layers of thickness. In weaker areas, where arteries penetrate the circular muscles to nourish the mucosal layer, outpouching characteristically exists. Diverticular are most commonly found in parallel rows.

Sigmoid colon is most commonly affected

44
Q

Outline the mechanism of action of the anti-diarrhoeal agent, loperamide. In which type of diarrhoea is loperamide NOT recommended?

A

Mechanism: acts off GIT opioid receptors (reduces peristalsis)

NOT USED WHEN UNDERLYING CAUSE IS AN INFECTION