Lecture 15- Distal GI tract pathology Flashcards
Definition of diarrhoea–
diarrhoea is a symptom and occurs in many conditions
- Loose or watery stools
- More than 3 times a day
- Acute diarrhoea (less than 2 weeks)
pathophysiology of diarrhea
- Unwanted substance in gut stimulates secretion and motility to get rid of it
- Primarily down to epithelial function (secretion) rather than increased gut motility
- End product has too much water in stool
- Colon is overwhelmed and cannot absorbed the quantity of water it recovers from ileum
- Normally 99% absorption of water from gut
- Leaving only 100mls in stool
Fluid movement down GI tract- normal conditions
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- Water is not actively moved across gut (transcellular and paracellular)
- Follows osmotic forces generated by movement of electrolytes/nutrients (sodium)
two broad categories of diarrhea
osmotic
secretory
Osmotic cause of D
- Molecules in the gut of high osmotic pressure
- E.g. malabsorption
- Stool volume moderately increased
- If you stop eating diarrhoea stops
Secretory cause of D
- Toxin/bacteria
- Water actively secreted into lumen of the gut
- Stool volume large
- Doesn’t respond to fasting
outline MOA of secretory diarrhea
- Electrolyte transport is messed up
- Too much secretion of ions (net secretion of bicarbonate or chloride)
- Toxins/ virus can increase cAMP within cytosol of enterocyte increases activity of CFTR–> pumps out chloride ions –>sodium follows and then water
main causes of osmotic diarrhea
Osmotic causes
- Gut lumen contains too much osmotic material caused by malabsorption
- ingesting material that is poorly absorbed e.g. antacids
- Inability to absorb nutrients e.g. lactose in lactase deficiency
- Will stop if you stop consuming offending substance.
- Other causes of osmotic diarrhea:
- Too little absorption of sodium
- Reduced surface area for absorption
- Mucosal disease/ bowel resection (coeliac or crohns)
- Reduced contact time (intestinal rush)
- Diabetes
definition of constipation
Definition- suggestive of hard stools, difficulty passing stools or inability to pass stools
- Straining during >25% of defecations
- Lumpy or hard stools in 25% defecations
- Feeling of incomplete evacuation in >25% of defecations
- Having fewer than three unassisted bowel movement a week
Risk factors of constipation
- Female: male 3:1
- Opioid’s/ antidiarrheal medications
- Low level of physical activity
- Increasing age (but also common in children under 4 years)
types of constipation
- normal transit constipation
- slow colon transport
defaecation problems
- Normal transit constipation
Related to other psychological stressors
- Slow colon transport
- Causes
- Large colon (megacolon)
- Fewer peristalitic movements (pacemaker cells of Cajal)
- Systemic disorders (hypothyroidism, diabetes)
- Nervous system disease (parkinsons, MS)
defaecation problems
- Cannot coordinate muscle of defaecating/ disorders of the pelvic floor or anorectum
constipation treatments
- Psychological support
- Increased fluid intake
- Increased activity
- Increased dietary fibre (only useful for mild constipation)
- Fibre medication
- Laxative
laxative scan be
osmotic and stimulatory
osmotic laxative
ingesting molecule with osmotic effect - magnesium sulphate, disaccharides–> draw water into intestinal lumen
- Stimulatory laxative
(chloride channel activators)
the appendix is an diverticulum off the cecum
- Has a complete longitudinal layer of muscle (colon has incomplete bands called teniae coli)
appendicitis
Inflammation of the appendix
blood supply of appendix
- Separate blood supply to the caecum coming up through a mesentery (mesoappendix) from ileocolic branch of SMA
- Location of appendix is important why
- changes presentation of acute appendicitis
- Retrocaecal
- Pelvic
- Sub- caecal
- Para-ileal (pre or post)
categories of appendicitis
Broad categories
- Acute (mucosal oedema)
- Gangrenous (transmural inflammation and necrosis)
- Perforated –> peritonitis
classic explanation of appendicitis
- Blockage of appendiceal lumen creates pressure in the appendix –> faecal matter (faecalith), lymphoid hyperplasia due to a previous virus, foreign body
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Causes venous pressure to rise (causing oedema in walls of appendix)
- Make it harder for arterial blood supply
- Ischaemia in walls of appendix
- Bacterial invasion follows
- Alternative explanations of appendix
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A viral or bacterial infection causes mucosal changes that allow bacterial invasion of appendiceal wall
classic symptoms of appendicitis
- Classic
- Poorly localised peri-umbilical pain
- Pain referred to T9, T10
- Following enlargement –> touches wall of abdo –>parietal peritoneum (RIF)
- Anorexia
- Nausea/vomiting
- Low grade fever
- 12-24h pain is felt more intensely in right iliac fossa
- Poorly localised peri-umbilical pain
- If appendix is retro-caecal or pelvic in its position you may
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- not get right iliac fossa pain
- Parietal peritoneum in right iliac fossa does not come in contact with inflamed appendix
- Supra-pubic pain, right sides rectal or vagina pain
- Parietal peritoneum in right iliac fossa does not come in contact with inflamed appendix
who are hard to diagnose appendicitis in
- Children make It difficult to diagnose
- History is difficult
- Symptoms less specific
- Preganancy
- Anatomy altered
signs of appendicits
- Slight fever/ tachycaria
- Generally lie quite still as peritoneum is inflamed peritonitis
- Localised right quadrant tenderness
- Rebound tenderness in right iliac fossa appears to be relatively specific
Rebound tenderness in right iliac fossa known as……
McBurnerys Point
more painful when moving hand away than pressing down
Appendicitis- diagnosis/ treatment
- Blood test
- raised WBC
- History or physical exam- if classic this might be enough
- Especially if rebound tenderness
- Pregnancy test/ urine dip
- Rule out ectopic or UTI
- In non-classical presentation (In the US)
- CT scan will show distended appendix that doesn’t fill with contrast
treatment of appendicitis
- Open appendicectomy
- Laparoscopic appendicectomy
diverticulosis
- Outpouchings in sigmoid colon
- Outpouching in mucosa and submucosa herniate through the Musclaris layers
- Occurs along where nutrient vessels (vasa recta) penetrate wall
symptoms of diverticulosis
asymptomatic
- pain can be due to duverticula- not inflammation
Acute diverticulitis
- When diverticula become inflamed or perforated (+/- bleeding and abscess formation)
- Occurs in 25% of people with diverticulosis
pathophysiology of acute diverticulitis
- Pathophysiology similar to appendicitis
- Entrance to diverticula blocked by faces
- Inflammation eventually allows bacterial invasion of the wall of the diverticula
- Can lead to perforation
- Uncomplicated diverticulitis
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Inflammation and small abscess confined to colonic wall
- Complicated diverticulitis
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Larger abscess, fistula and perforation
Symptoms of acute diverticulitis
- Abdominal pain at site of inflame
- Fever
- Bloating
- Constipation
diagnosis of acute diverticulitis
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Blood tests
- Blood tests
- USSS
- CT scan – extra mural problems
- Colonoscopy if large haematochezia dont want to perforate
- Elective colonoscopy- after things have settled- to determine cause of symptoms if unclear
- Treatment of diverticulitis
- Antibiotics, fluid rescuscitation and analgesia
- Uncomplicated diverticulitis= analgia and oral antibiotics
- Surgery if perforation or large abscesses need to be drain
- Partial colectomy required if other treatment fail
