Distal GI tract Pathology Flashcards
Define diarrhoea. What is the pathophysiology?
A symptom that occurs in many conditions where you have:
Loose or watery stools
>3 times a day
Acute (<2 weeks)
Unwanted substances in gut stimulate secretion and motility to remove them, primarily down to epithelial function of secretion, colon is overwhelmed and can’t absorb the quantity of water it receives from ileum (normally 99% absorption)
What are the two broad categories of diarrhoea? explain how each come about.
Osmotic - osmotically active, poorly absorbed solutes in bowel lumen draws water in e.g. some laxatives, lactose intolerance, antacids (MgSO4) ,(stops when person fasts)
Secretory - body secretes electrolytes into gut lumen and water follows e.g. salmonella, E.coli, laxatives. Net secretion of chloride or bicarbonate into lumen and too little absorption Na+ mucosal disease/ bowel resection SA reduced e.g. coeliac/ IBD and reduced contact time e.g. diabetes
Define constipation. Risk factors
Suggestive of hard stools, difficulty passing stools or inability to pass stools
- straining during _> 25% defections
- lumpy/ hard stools _>25%
- feeling incomplete evacuation _>25%
- feeling obstruction/ blockage _>25%
- having <3 unassisted bowel movements a week
Female (3:1)
Certain medications e.g. codeine
Low physical activity level
Older or <4yrs
Pathophysiology of constipation
Normal transit constipation (often related psychological stressors e.g. IBS, anxiety)
Slow colonic transport e.g. megacolon, fewer peristaltic movements and shorter ones, fewer intestinal pacemaker cells (intestinal cells of cajal), systemic disorder (hypothyroidism, diabetes), Ns disease (Parkinson’s, Ms)
Defaecation problems (can’t coordinate muscles/ disorders pelvic floor or anorectum)
Describe the 3 movements of the colon
- Peristalsis (contraction behind and dilation in front, during digestion)
- Mass movement - food stored in TC/ AC -> gastrocolic reflux -> rectum distends (intense prolonged peristalsis, strips area clear of contents)
- Segmentation - shuttle contractions, during fasting, moves material forwards and back facilitating absorptive processes
Treatments of constipation
✅psychological support
Increased fluid intake
Increased activity
Increased dietary fibre
Fibre medication
Laxatives (osmotic MgSO4, disaccharides) (stimulatory, Chloride channel activators) (stool softeners)
Appendix blood supply, and location. How does this impact where you feel pain with appendicitis, when might this change?
The appendix is a diverticulum of the caecum . Complete longitudinal layer of muscle
Separate blood supply to caecum through a Mesentery (mesoappendix) from ileocolic branch of SMA
Retro-caecal, pelvic, sub-caecal, para-ileal
If long appendix, rectal/ pelvic pain.
Foregut so peri-umbilical pain -> touches parietal peritoneum so localised right-iliac fossa (midgut) - mcburney’s point (1/3 way from ASIS to umbilicus)
Categories of appendicitis
Acute (mucosal oedema), gangrenous (transmural inflammation and necrosis), perforated
Causes of appendicitis
Classic explanation: blockage of appendiceal lumen creates a higher pressure in the appendix (faecolith, lymphoid hyperplasia (few weeks after viral infection, lymphoid ring), foreign body) -> venous pressure rises (oedema appendix walls) -> harder arterial blood supply -> ischaemia walls -> bacterial invasion
Alternative explanation: viral/ bacterial infection -> mucosal changes that allow bacterial invasion of appendiceal walls
Symptoms of appendicitis
Classic presentation (<60%): Poorly localised peri-umbilical pain, anorexia, nausea/ vomiting (stretch receptors gut), low grade fever, after 12-24hrs pain more intense right iliac fossa
If appendix retro- caecal or pelvic may not get pain right iliac fossa - parietal peritoneum doesn’t come in contact then Amy get supra-pubic pain, right sided rectal/ vaginal
Children more non-specific
Pregnancy- pushes anatomy up
Signs of appendicitis
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 relatively specific (McBurney’s point 2/3 of way from umbilicus to ASIS)
Diagnosis and treatment appendicitis
Blood test - raised WBC
History/ physical examination especially if rebound tenderness RIF
Pregnancy test/ urine dipstick rule out UTI
If non-classical presentation Ct scan distended doesn’t fill contrast
✅open appendicectomy, laparoscopic appendicectomy
What is diverticulosis?
Asymptomatic, occurs in colon (85% sigmoid c), outpouchings of mucosa and submucosa herniate through the muscularis layers along where nutrient vessels (vasa recta) penetrate the bowel wall. Thought to be caused by increased intra-luminal pressure (low fibre diet/ constipation)
What is diverticula disease?
Patient experiences pain but there is no inflammation/ infection
What is acute diverticulitis? What is the pathophysiology? What’s the inference between uncomplicated and complicated?
When the diverticula (outpouchings of mucosa and submucosa) become inflamed or perforate (+/- bleeding and abscess formation)
Occurs up to 25% of ppl with diverticulosis
Pathophysiology: entrance to diverticula is blocked by faeces, inflammation eventually allows bacterial invasion of the wall of the diverticula, can lead to perforation (similar to appendicitis)
Uncomplicated diverticulitis -inflammation and small abscesses confined to colonic wall
Complicated- larger abscesses, fistula, perforation (-> peritonitis)
