GI14 - Distal GI Tract Pathology Flashcards
2 features of diarrhoea
Definition
Pathophysiology
1.) Definition - loose or watery stools > x3 a day
- acute diarrhoea lasts < 2 weeks
2.) Pathophysiology - unwanted substance in gut stimulates water secretion and increased motility to try and remove it
- colon is overwhelmed so cannot absorb quantitiy of water it receives from the ileum –> diarrhoea
2 groups of causes of diarrhoea
Osmotic
Secretory (+ 1 other)
1.) Osmotic - gut lumen contains too much osmotic material due to malabsorption. causes:
- inability to absorb nutrients (e.g. lactose intolerance)
- ingesting poorly absorbed material (e.g. antacids)
- diarrhoea settles with not eating
2.) Secretory - too much secretion of osmotically active ions into the gut lumen (Cl-, HCO3-)
- infectious toxins affect messenger systems that control ion transport
- diarrhoea doesn’t settle with not eating
3.) Reduced Sodium Absorption - less Na+ absorbed from gut lumen so less water follows. causes:
- reduced SA, bowel resection (Coeliac’s Crohns’), reduced contact time (diabetes)
- falls under secretory
4 features of constipation
Definition
Risk Factors
Aetiology
Treatment
1.) Definition - difficulty passing stools
- straining, lumpy/hard stools, feeling of incomplete evacuation or obstruction
2.) Risk Factors - female, elderly (also common in < 4 yrs)
- medication, sedentary lifestyle, stroke patients
3.) Aetiology - slow colonic transport or defecation problems
4.) Treatment - increased fluid intake, dietary fibre (only for mild constipation), physical acitivty
- fibre medication, laxatives
4 features of the appendix
What is it?
Muscle Layer
BLood Supply
Locations
1.) What is it? - diverticulum off the posteromedial end of the caecum
2.) Structure - has a complete longitudinal layer of muscle (colon has incomplete bands, teniae coli)
3.) Blood Supply - appendicular artery which is a branch from the ileocolic which comes from the SMA
- artery and corresponsding vein contained within the mesoappendix (its own mesentery)
4.) Locations - most common location is retrocaecal
- pre-ileal, post-ileal, sub-ileal, pelvic, subcaecal, paracaecal, retrocaecal
4 features of appendicits
Broad Categories x3
Aetiology
Investigations x5
Treatment
1.) Broad Categories
- acute: mucosal oedema
- gangrenous: transmural inflammation and necrosis
- perforated: bowel contents enter peritoneal cavity
2.) Aetiology - blockage of appendiceal lumen
3.) Investigations
- blood test: raised WBCs (very non specific)
- history/physical examination
- pregnancy test: rule out ectopic pregnancy
- urine dip: rule out UTI
- CT Scan: shows distended appendix that doesn’t fill with contrast
4.) Treatment - surgery
- open appendicectomy
- laparoscopic appendicectomy
4 features of the pathophysiology of appendicitis
High Pressure
Oedema
Ischaemia
Alternative Explanation
1.) High Pressure in Appendix - due to a blockage of the appendiceal lumen, blockage could be caused by:
- faecolith, lymphoid hyperplasia, foreign bodies
2.) Oedema in Appendix Walls - due to the rise in venous pressure
3.) Ischaemia in Appendix Walls - oedema makes it harder for arterial blood to supply the appendix
- bacterial invasion follows the ischaemia
4.) Alternative Explanation - viral or bacterial infection causes mucosal changes that allow bacterial invasion of appendiceal walls
Signs and symptoms of appendicitis
Classic Pain Location
Alternate Pain Location
Pain Location in Pregnancy
Other Signs and Symptoms
Symptoms in Children
1.) Classic Pain Location
- visceral pain: poorly localised umbilical pain
- somatic pain: intense pain in right iliac fossa (12-24hr)
2.) Alternate Pain Location - if appendix is retrocaecal or pelvic, you may not get pain in the right iliac fossa
- don’t make contact with the parietal peritoneum
- may get supra-pubic, right sided rectal or vaginal pain
3.) Pain Location in Pregnancy - the anatomy is altered so pain could appear anywhere
4.) Other Signs and Symptoms - mild fever, tachycardia, nausea/vomiting, anorexia, rebound tenderness in McBurney’s point (RLQ)
5.) Symptoms in Children - symptoms are much more non-specific and history is difficult
Diverticulosis and acute diverticulitis
Diverticulosis
Acute Diverticulitis
Uncomplicated Diverticulitis
Complicated Diverticulitis
1.) Diverticulosis - outpouchings of mucosa and submucosa herniate through the muscularis layers
- caused by increased intra-luminal pressure (low fibre)
- occurs in the colon where nutrient vessels penetrate the bowel wall (85% in the sigmoid colon)
2.) Acute Diverticulitis - diverticula becomes inflamed or perforate +/- bleeding and abscess formation
- similar pathophysiology to appendicitis (blockage)
3.) Uncomplicated Diverticulitis - inflammation and small abscesses confined to colonic wall
4.) Complicated Diverticulitis - complications:
- perforation which can lead to larger abscesses
- fistulae (often between sigmoid and bladder/vagina)
- strictures
4 diagnostic features of acute diverticulits
Symptoms x5
Signs x4
Investigations x5
Treatment x4
1.) Symptoms - abdominal pain (usually LLQ), fever, bloating, constipation, haematochezia
2.) Signs - localised abdominal tenderness, distension, reduced bowel sounds, signs of peritonitis (perforation)
3.) Risk Factors - low fibre, age (>50s), developed countries (low fibre)
4.) Investigations - blood test, pregnancy test, ultrasound, CT, colonoscopy,
5.)Treatment - antibiotics, fluid resuscitation, painkillers
- surgery if perforation or large abscesses need to be drained
6 features of the rectum
Function
Peritoneum Relationship
Muscle Layer
Route
Arterial Supply x3
Venous Drainage
1.) Function - temporary storage of faeces
- stretching of rectum stimulates urge to defecate
2.) Peritoneum Relationship - some parts are covered in peritoneum whilst other parts are extra-peritoneal
3.) Muscle Layer - has continous band of outer longitudinal muscles unlike the teniae coli of the LI
4.) Route - passes through the pelvic floor
- 12-15 cm long
5.) Arterial Supply - several arteries, forming a plexus
- superior rectal artery (continuation of IMA)
- middle rectal artery (internal iliac)
- inferior rectal (pudendal artery)
6.) Venous Drainage - potential site for porto-systemic anastomosis –> anorectal varices
- portal drainage through the superior rectal vein
- systemic drainage through internal iliac vein
4 features of the anal canal
Anatomical Features
Function (4 factors required)
Anal Sphincter Complex
Dentate/Pectinate Line
1.) Anatomical Features - anal canal starts at the proximal border of the anal sphincter complex
- rectum points anteriorly whilst anal canal is posterior
- puborectalis sling changes direction of the anatomy
2.) Function - involved in continence, factors required:
- distensible rectum, firm bulky faeces, anal cushions, normal anal sphincter and anorectal angle
3.) Anal Sphincter Complex - involved in the defecation reflex
4.) Dentate Line - junction of hindgut and ectoderm
- above the dentate line is columnar epithelium and visceral pain receptors so pathologies are PAINLESS
- below the dentate line is stratified squamous and somatic pain receptors so pathologies are PAINFULL
2 divisions of the anal sphincter complex
Type of Muscle
Innervation
Sections
1.) Internal Anal Sphincter - circular smooth muscle
- under autonomic control so is involuntary
- makes up 80% of resting anal pressure
2.) External Anal Sphincter - striated muscle (voluntary)
- under somatic control (pudendal nerve)
- deep sections: found in upper anal canal and joins with puborectalis to form a sling
- also has superficial and subcutaneous sections
3(4) steps in the defecation reflex
Stimulus
Responses x3
Delay or Defecation
1.) Stimulus - mass movement causes distension in the rectum
2.) Responses - leads to increased pressure in rectum
- contraction in rectum and sigmoid colon
- relaxation of internal anal sphincter
- contraction of external anal sphincter
3a.) Delay - reverse peristalsis in rectum
- contraction of external anal sphincter
- contraction of puborectalis muscle
3b.) Defecation - increased abdominal pressure leads to fowards peristalsis in rectum and sigmoid colon
- relaxation of external anal sphincter
- relaxation of puborectalis muscle
5 features of anal cushions/haemorrhoids
Anal Cushions
Internal Haemorrhoids
Grades of Internal Haemorrhoids
Treatment of Internal Haemorrhoids
External Haemorrhoids
1.) Anal Cushions - complex venous plexus in the anus
- play a role in anal continence
- divided into 3+ areas of tissues called anal cushions
A - connections between the veins and some arteries
2.) Internal Haemorrhoids - abnormal swelling or enalargement of anal vascular cushions
- caused by loss of connective tissue support
- above the dentate line so relatively painless
- can enlarge and prolapse through the anal canal (due to constipation)
- bleed bright red, painless, pruritus, prolapse, discharge
3.) Grades of Internal Haemorrhoids - grades 1-4
- 1: prominent blood vessels with no prolapse
- 2: prolapse during defecation, but spontaneous reduction
- 3: prolapse, but requires manual reduction
- 4: prolapse w/ inability to be manually reduced
5.) External Haemorrhoids - swelling of the anal cushions which may then form blood clots
- when internal haemorrhoids are left untreated
- below the dentate line so very painful
- treatment is ice packs to reduce the swelling then you treat like internal
4 features of anal fissures
Definition
Aetiology x2
Sympotms x3
Treatment x5
1.) Definition - linear tear in the anoderm (stratified squamous epithelium lining the anus)
2.) Aetiology - high internal anal sphincter tone and reduced blood flow to anal mucosa
3.) Symptoms
- passing of hard stools
- extreme pain in defecation (below dentate line)
- haematochieza
4.) Treatment
- hydration, warm baths, dietary fibre, painkillers
- medication to relax the internal anal sphincter:
- rectal GTN ointment first line
- topical diltiazem if GTN not tolerated (headaches, hypotension)
