Lecture 15- Distal GI tract pathology Flashcards
Diarrhoea
Loose or watery stool
Occurs 3 + times a day
Acute - for less than 2 weeks
Causes of diarrhoea
Excessive secretion of ions by e.g. cholera toxin
Inadequate absorption of sodium:
- reduced SA
- Bowel resection
- Mucosal disease - Coeliac’s or Crohn’s
- reduced contact time - diabetes and IBS
Malabsorption
- indigested material that is poorly absorbed
- antacids - magnesium sulphate
- Inability to absorb nutrients - lactose intolerance
Constipation
Difficulty or inability to pass stools
In more than 25% of defaecations:
- Straining
- Hard or lumpy stool
- Feeling of incomplete evacuation
- Feeling of blockage
- Fewer than 3 unassisted bowel movements per week
RF for constipation
Female Medication - codine Old age Low physical activity Drinking less water
Pathophysiology of constipation
Slow colonic transport
- megacolon
- Decreased peristalsis
- Fewer intestinal pacemaker cells present
- Hypothyroidism
- diabetes
- Parkinsons and MS
Movements in colon
Shuttling
Peristalsis
Gastrocolic movement -mass movement
Treatments of constipation
Psychological Increased fluid intake Increased activity Laxatives - magnesium sulphate , dissacharides, chloride channel activators and stool softners Increased fibre intake Fibre medication
Appendix
Diverticulum of caecum
Complete longitudinal layer of muscle
Seperate blood supply from caecum - ileocolic artery from mesentery
Appendicitis pain
Midgut structure - peri-umbilical pain
If touches parietal peritoneum - right iliac fossa pain
If long and runs in pelvis - pelvic and rectal pain
Categories of appendicitis
Acute - mucosal oedema
Gangrenous - transmural and necrosed
Perforated - peritonitis
Causes of appendicitis
- Blockage in lumen due to faecolith, lymphoid hyperplasia or foreign body
- Increase in pressure in appendix
- Increased venous pressure causing oedema
- Decreased arterial supply causes ischaemia and bacterial invasion due to stasis
Also caused by viral or bacterial infection - mucosal changes for bacterial invasion
Symptoms of appendicitis
Poorly localised peri-umbilical pain Nausea and vomiting Anorexia Low grade fever If persists more than 12 hours - RLQ (iliac fossa) pain
Sign of appencitis
Rebound tenderness:
Palpation - pain felt when let go as there is a sharp movement of the peritoneum
McBurney’s point - 2/3rds of the way from umbilicus to ASIS
Diagnosis of appendicitis
Blood test - WBC
History and examination for rebound tendernous
Pregnancy test
CT - distended appendix doesn’t fill with contrast
Treatment of appendicitis
Open or laproscopic appendicectomy
Diverticulum
Outpouching of mucosa and submucosa which herniates through the muscularis layer
Where nutrient vessels (vasa recta) penetrate the bowel wall as weakest
Asymptomatic
Occurs in colon - 85% sigmoid colon
Cause of diverticulosis
Increased intraluminal pressure due to low fibre diet
Acute diverticulitis
Diverticulum becomes inflamed or perforated +/- bleeding and abscess formation
25% of diverticulosis:
- Entrance of diverticulum is blocked by faecolith
- Inflammation causes bacterial invasion of the diverticula wall
- Can be perforated
Uncomplicated diverticulitis
Inflammation and abscesses confined to colonic wall
Complicated diverticulitis
Larger abscesses
Fistulas
Perforation
Sign and symptoms of acute diverticulitis
Abdominal pain normally LLQ Constipation - inflammation blocks lumen Fever Bloating Haematochezia - blood in stool
Signs:
Abdominal tenderness
Decreased bowel sounds - decreased bowel movements
Distention
Signs of peritonitis if perforated e.g. nausea and vomiting
Acute diverticulitis investigations
Bloods - raised WBCs
Pregnancy test
Colonoscopy - if haematocheizia but may cause perforation
USS
CT
Treatment of diverticulitis
Antibiotics
Fluid resuscitation - saline
Analgesia
Surgery if perforated
Large abscesses are drained
Structure of rectum
Outer continuous longitudinal muscle
Curved shape anterior to sacrum
Partly intraperitoneal and retroperitoneal
When distended, triggers urge to defecate as temporary store of faeces before defaecation
Blood supply
Superior rectal artery - IMA ( after pelvic brim)
Middle rectal artery - internal iliac
Inferior rectal artery - pudendal artery
Venous drainage:
- Portal drainage through superior rectal vein
- Systemic drainage - internal iliac vein
Anal canal
Narrow continuation of the rectum from the anal sphincter
The rectum points anteriorly but the puborectalis muscle acts like a sling causing the anal canal to point posteriorly
Factors affecting continence
Distensible rectum Anal canal angle via puborectalis Firm stool Anal cushions Normal anal sphincter
Internal involuntary sphincter
Thickening of circular smooth muscle
Under autonomic control
Contributes 80% to resting anal pressure
External anal sphincter
Striated muscle
The deep section mixes with levator ani muscles and joins with the puborectalis muscle to form a sling
Also has superficial and subcutaneous section
Innervated by the pudendal nerve
20% anal pressure at rest
Dentate line
Junction between the hindgut and proctodaeum
Above dentate line
Visceral receptors and columnar epithelium
- pain less felt
Below dentate line
Somatic pain receptors
Stratified squamous epithelium
- Pathology is painful
Haemorroid tissue
Anal cushions - normal swellings of veins and arteries
- Complex venous plexus
- role in anal continence
Haemorrhoids
Symptomatic anal cushions
- internal and external haemorrhoids
Internal haemorroids
Above dentate line - painless
Loss of connective tissue support
Enlarge and prolapse into the anal canal
Bleeding - pruritis (bright red)
Treatment of internal haemorrhoids
Hydration High fibre diet Avoid straining Surgery if severe Rubber band ligation
External haemorrhoids
Below dentate line - painful
Swelling of the anal cushions that may thrombose
Surgery required
Anal fissure
Linear tear in anoderm
Hematochezia
pain when defaecating
Caused by:
- Increased internal anal sphincter tone
- Decreased blood flow to anal mucosa
Treatment:
- Rehydration
- High fibre diet
- Medication to relax sphincter
- Warm baths
- Analgesia
Melaena
Black tarry stool
Offensive smell
Hb altered by digestive enzymes in the gut
Due to: Peptic ulcers Variceal bleeds Oesophageal or gastric cancer Upper GI malignancy
Meckel’s diverticulum
Congenital outpouching of the lower small intestines
Remnant of the umbilical cord
