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Distal GI tract pathology Flashcards

1
Q

What is Diarrhoea?

A

Loose or watery stools more than 3 times a day

(Acute Diarrhoea = less than 2 weeks)

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2
Q

What are the 2 main classes of diarrhoea? Briefly explain each

A

Osmotic and Secretory

Osmotic: osmotic chyme increases osmotic pressure drawing water into lumen. Diarrhea stops when fasting

Secretory : no chyme needed, ion movement causes large amounts of water to enter lumen. Diarrhoea does not stop when fasting

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3
Q

Explain the underlying problem in secretory diarrhoea

A
  • Too much secretion of ions (Cl- or HCO3-) into the GI lumen
    • Commonly caused by infectious toxins
  • Too little reabsorption of Na+ due to:
    • reduced surface area for reabsorption
    • Mucosal disease/ bowl resection
    • Reduced contact time → reduced contact time
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4
Q

Explain the underlying cause of osmotic diarrhoea

A
  • Gut lumen contains too much osmotic material due to malabsorption
  • Ingested material poorly absorbed e.g. antacids are not absorbed
  • Inability to absorb nutrients e.g. lactose intolerance
  • Will settle if you stop consuming the offending substance
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5
Q

What is constipation?

A

Hard stools, difficult to pass

  • straining during >25% defecations
  • Lumpy or hard stools >25% defecations
  • Feeling incomplete evacuation >25% defecations
  • Fewer than three unassisted bowel movements a week
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6
Q

What are some risk factors for constipation?

A
  • Female vs male (3:1)
  • Certain medication e.g. codeine
  • Low level of physical activity
  • Increases with age
  • Common in children under 4
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7
Q

What things can cause constipation?

A
  • Normal transit constipation → related to psychological stressors
  • Slow colonic transport → greater transport time = more water rabsorbed
    • megacolon
    • fewer perilstaltic moveement
    • fewer intestinal pacemaker cells
    • systemic disorders; hypothyroid &diabetes
    • nervous system disorders; Parkinson’s, MS
  • Defecation problems → cannot coordinate muscles for defecation
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8
Q

How does faeces movement change during fasting and digestion?

A

In fasting: material moves back and forth (shuttle contractions) in colon to faciliation absorption

In digestion: mass movement progressive waves force material to the rectum

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9
Q

What treatment can you give for constipation?

A
  • Psychological support
  • Increased fluid intake
  • Increased activity
  • Increased dietary fibre
  • Fibre medication
  • Laxatives
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10
Q

Describe the anatomy of the appendix

A
  • A diverticulum off the caecum
  • Complete longitudinal layer of muscle
  • Has a separate blood suppl to the caecum from a branch of the ileocolic branch of SMA
  • Location can be retrocaecal, pelvic, subcaecal, paraileal which will change the presentation of appendicitis
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11
Q

What are the 3 broad categories of appenticitis?

A
  • Acute (mucosal oedema)
  • Gangrenous (transmural inflammation and necrosis)
  • Perforated
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12
Q

Explain the classic explanation of appendicitis

A
  • Blockage of the appendix lumen creates higher pressure in the appendix
    • can be blocked by faecolith, lymphoid hyperplasia, foreign body
  • Causes venous pressure to rise → oedema in walls of appendix → can reduce blood supply
  • Ischemia in walls of appendix
  • Bacterial invasion follows
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13
Q

Explain the alternative explanation for appendicitis

A

Viral or bacterial infection causing mucosal changes allowing bacterial invasion of appendiceal walls

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14
Q

What is the classic presentation of appendicitis?

A
  • poorly localised peri-umbilical pain
  • anorexia
  • nausea/ vomiting
  • pain localises to right iliac fossa after 12-24 hrs
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15
Q

In what circumstances would you not see the classical presentation of appendicitis?

A
  • If appendix is retro-caecal you might not get right, iliac fossa pain → pain may be elsewhere
  • Children give non specific symptoms
  • Pregnancy alters anatomy → pain higher up
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16
Q

What signs do you see in appendicitis?

A
  • Patients appear slightly ill
  • Slight fever/ tachycardia
  • Lie quite still as peritoneum is inflammed
  • Localised right quadrant tenderness
  • Rebound tenderness in right iliac fossa
    • Push in and let go → pain on letting go
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17
Q

How do you diagnose appendicitis?

A
  • Blood test- looking for raised WBC (non- specific)
  • History/ examination
  • Do pregnancy test in women
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18
Q

How do you treat apendicitis?

A

Surgery: either open or laproscopic appendicectomy

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19
Q

What is Diverticulosis?

A

An outpouching of mucosa and submucosa, herniating through the muscularis layers of the bowel

Occurs where nutrient vessels penetrate bowel creating an area of weakness

20
Q

Where do the majority of diverticulosis occur? Why here?

A

85% in the sigmoid colon

At this stage of the colon, stools have formed so needs higher pressure to move it along. This high pressure predisposes to diverticulosis

21
Q

What is acute diverticulitis?

A

When diverticula become inflammed/ perforate

Occurs in 25% of people with diverticulosis

22
Q

How does acute diverticulitis occur?

A
  • Entrance to diverticula blocked by faeces
  • Inflammation allows bacterial invasion of wall of diverticula
  • Can lead to perforation
23
Q

What is the difference between complicated and uncomplicated diverticulitis?

A

Uncomplicated: inflammation and small abscess confined to colonic wall

Complicated: Larger abscesses, fistula, perforation

24
Q

What is divertocular disease?

A

Where patient experiences pain in diverticula but there is no inflammation/ infection

25
What are the symptoms of acute diverticulitis?
* Abdominal pain at site of inflammation * Fever * Bloating * Constipation * Haematochezia (blood in stool)
26
What are the signs of acute diverticulitis?
* Localised abdominal tenderness * Distension * Reduced bowel sounds * Signs of peritonitis (if perforated)- won't want to move at all due to pain
27
How do you diagnose acute diverticulitis?
* Ultrasound * CT scan * Colonoscopy if large haematochezia (but careful not to perforate) * Elective colonoscopy after symptoms settle to determine cause
28
How do you treat acute diverticulitis?
* Antibiotics * Fluid resusciation * Analgesia * Surgery if perforated * Drained if its a large abscess
29
Describe the anatomy of the rectum
* 12-15 cm long * **Continuous band** of outer longitudinal muscle * Curved to the shape of the sacrum * Some parts covered in peritoneum
30
Describe the blood flow to the rectum
Several arteries join to form a plexus * superior rectal artery (continuation of IMA) * middle rectal artery - from internal iliac * inferior rectal - from pudendal artery
31
Describe the venous drainage of the rectum
Dual drainage 1. Portal drainage through **superior rectal vein** 2. Systemic drainage through **internal iliac vein**
32
Describe the anatomy of the anal canal
A narrowed portion of GI tract that continues on from the rectum * starts at the proximal border of the **anal sphincter complex** * Rectum points **anteriorally** * **Pubo-rectalis sling** then changes the direction of anatomy * Anal canal points **posteriorally**
33
What 5 factors are required for continence?
1. distendible rectum 2. firm, bulky faeces 3. normal anorectal angle 4. anal cushions 5. normal anal sphincters
34
Describe the anal sphincter complex
**Internal involuntary sphincter** * Thickening of smooth muscle * under autonomic control * 80% of resting pressure **External anal sphincter** * striated muscle * mixes with fibres from levator ani * superficial and subcutaneous sections * 20% of resting pressure
35
Describe the gastrocolic reflex of defecation
1. Mass movement into the bowel 2. Rectum **distends** triggering defecation reflex 3. Rectum and sigmoid colon **contract** 4. **internal** anal sphincter **relaxes** 5. **external** anal sphincter **contracts** → pressure builds in the rectum 6. Either **delay** → external sphincter **contracts**, reverse perilstalises into rectum 7. Or defectation → **relaxation** of external sphincter, puborectalis relaxed straightening angle of rectum, forward perilstalsis
36
How does the rectum differ below and above the dendate line?
**Above**: * Visceral pain receptors * **Columnar** epithelium **Below:** * somatic pain receptors * **Stratified Squamous** Epithelium
37
What are anal cushions?
A complex of 3 areas of tissue with venous plexus' Play a role in anal continence
38
What are haemorrhoids?
**Symptomatic Anal cushions** Either internal or external
39
What are internal haemorrhoids, how are the caused and what are the symptoms?
Internal haemorrhoids are caused by a **loss of connective tissue support** They are **above** the dendate line so relatively **painless** Can enlarge and prolapse through anal canal May see **bright red blood** / pruritis (itching)
40
How would you treat internal haemorrhoids?
* Increase **hydration** and **fibre** in the diet * Avoid straining * Rubber band ligation * Surgery
41
What are external haemorrhoids?
Swelling of anal cushions that may **thrombose** Below the dendate line so very **painful**
42
What is an anal fissure and how does it present?
A **linear tear** in the **anoderm** below the dendate line Presents with pain on defecation and haematochezia
43
What is the underlying cause of an anal fissure?
* **High** internal sphincter **tone** * **Reduced blood flow** to the anal mucosa * Passing of **hard stools**
44
How do you treat an anal fissure?
* Hydration, dietary fibre, analgesia * Warm baths * Medication to try and **relax** the **internal** anal sphincter
45
What are some common causes of haematochezia?
* Diverticulitis * Angiodysplasia (vascular malformation in bowel wall) * Colitis * Colorectal cancer * Anorectal disease - haemorrhoids, anal fissure * Upper GI bleed
46
What is melaena and how is it formed? Give some common causes
Melaena is **black, tarry, offensive smelling** stools. Formed due to Hb being altered by digestive enzymes and gut bacteria Common causes: * **Upper GI bleeding** * Pepic ulcer disease * Variceal bleeds * Upper GI Malignancy * Oesophageal/ Gastric cancer

GI System (15 decks)

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