Distal Gi Tract Pathology Flashcards
What is diarrhoea
Definition- 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)
Describe the pathophysiology of diarrhoea
Pathophysiology •Unwanted substance in gut stimulates secretion and motility to get rid of it- diarrhoea •Primarily down to epithelial function (secretion) rather than increased gut motility (although this does occur) (Problem with absorptionn or secretion primarily. Sped up motility = less contact time for stuff to be absorbed)`
• The end product is too much water in stool
•Colon is overwhelmed and cannot absorb the quantity of water it receives from ileum
•There is normally 99% absorption of water from gut
• Leaving only 100 mls in stool/day
How is fluid normally move down the GI tract
Fluid movement down GI tract- normal conditions
• Remember that water is not actively moved across gut
•Follows osmotic forces generated by the movement of electrolytes/nutrients
• Paracellular/transcellular
In diarrhoea Two broad categories- Osmotic & secretory
What is secretory diarrhoea
Secretory- Electrolyte transport is messed up Too much secretion of ions (net secretion of chloride or bicarbonate)
• Cause of diarrhoea will affect the messenger systems that control ion transport
• Infectious toxins (we will look at examples in infection lecture)
Too little absorption of sodium • Reduced surface area for absorption • Mucosal disease/ bowel resection - Coeliac or inflammatory bowel disease (Crohn’s) • Reduced contact time (intestinal rush) • Diabetes/?IBS
What is osmotic diarrhoea
Osmotic- the gut lumen contains too much osmotic material (malabsorption)
• Ingesting material that is poorly absorbed (antacids- magnesium sulphate)
• Inability to absorb nutrients (eg lactose in lactase deficiency)
• Will settle if you stop consuming offending substance
Define constipation
Definition- suggestive if hard stools, difficulty passing stools or inability to pass stools
• Straining during ≥25% of defecations
• Lumpy or hard stools in ≥25% of defecations
• Feeling of incomplete evacuation in ≥25% of defecations
• Feeling of obstruction or blockage to defecation in ≥25% of defecations
• Having fewer than three unassisted bowel movements a week
What are teh risk actors for constipation
Risk factors
• Female vs male (3:1)
• Certain medications
• Low level of physical activity (Eg if you’ve had a stroke and have problems with mobility)
• Increasing age (but also common in children under 4 years old)
Describe teh apthophysiology of constipation
• Normal transit constipation (often related to other psychological stressors)
• Slow colonic transport
- Large colon (megacolon)
- Fewer peristaltic movements and shorter ones
- Fewer intestinal pacemaker cells present (interstitial cells of Cajal)
- Systemic disorders (hypothyroidism, diabetes)
• Nervous system disease (Parkinson’s, MS)
- Defaecation problems
- Cannot coordinate the muscles of defaecation/disorders of the pelvic floor or anorectum
What are the treatments for constipation
Treatments
• Psychological support
•Increased fluid intake
•Increased activity
•Increased dietary fibre (only useful for mild constipation)
•Fibre medication (may not 100% help)
•Laxatives- (Please note similarity with causes of diarrhoea)
- Osmotic (magnesium sulphate, disaccharides
- Stimulatory (chloride channel activators)
- Stool softeners
Give a brief overview of the appendix
- The appendix is a diverticulum off the caecum
- Has a complete longitudinal layer of muscle (colon has incomplete bands called teniae coli)
- Separate blood supply to caecum coming up through a mesentery (mesoappendix) from the ileocolic branch of SMA
- Location of the appendix is important because it changes the presentation of acute appendicitis
- Retro-caecal
- Pelvic
- Sub-caecal
- Para-ileal (pre or post)
What is the classic presentation of apendiciti
Classic appendicitis: Slight dilation - visceral afferent s - t10 dermatome - vague periumbilical pain. As it grows it can touch the parietal peritoneum, so get pain in right iliac fossa
But appendix can be in a different position and may not touch the parietal peritoneum
What are the broad categories of appendicitis
Broad categories
• Acute (mucosal oedema)
• Gangrenous (transmural inflammation and necrosis)
• Perforated
What are the causes of appendicitis
Causes •Classic explanation
• blockage of appendiceal lumen creates a higher pressure in the appendix (faecolith, lymphoid hyperplasia, foreign body)
• This causes venous pressure to rise (causing oedema in walls of appendix)
• This makes it harder for arterial blood to supply appendix
• Ischaemia in walls of appendix
• Bacterial invasion follows
Lymphoid nodules for eh in virus - lymphoid hyperplasia - can obstruct the lumen of the appendix. A fecalith can also block the appendix. Blocks can set off a chain reaction - bacterial proliferation. - infection - perforation
- Alternative explanation
- A Viral or bacterial infection causes mucosal changes that allow bacterial invasion of appendiceal walls
What are the symptom TOMS of appendicitis
Classic presentation (<60% of cases) • Poorly localised peri-umbilical pain • Anorexia • Nausea/vomiting • Low grade fever • After 12-24 hours pain is felt more intensely in right iliac fossa
- If appendix is retro-caecal or pelvic in its position you may not get right iliac fossa pain
- Parietal peritoneum in right iliac fossa does not come in contact with inflamed appendix • Supra-pubic pain, right sided rectal or vaginal pain
- Children make it difficult to diagnose
- History is difficult • Symptoms are much more non-specific
- Pregnancy
- Anatomy is altered
What are teh signs of appendicitis
• Patients appear slightly ill
•Slight fever/tachycardia •Generally lie quite still as peritoneum is inflamed
•Localised right quadrant tenderness
•Rebound tenderness in right iliac fossa appears to be relatively specific
Push in, then rebound is painful
