Please enable JavaScript.

Coggle requires JavaScript to display documents.

GI TBL 4 - Colon - Coggle Diagram

- - - - Neutrophils with colonic mucosa
      - Cryptitis, crypt abscess, erosions/ulcerations
      - Sigmoid diverticulitis
        
        True diverticulum
        
        Outpouching of all layers of bowel wall
        
        False diverticulum
        
        Outpouching of mucosa and submucosa only
        
        Colonic diverticulosis
        
        Develop under elevated intraluminal pressure in sigmoid colon
        Outpouching through muscularis propria into pericolic fat
    - - Diffuse mucosal crypt architectural distortion due to severe damage to mucosa -> crypt damage and surrounding connective tissue
        Diffuse mucosal crypt architectural distortion, paneth cell, pyloric metaplasia
      - Inflammatory Bowel Disease
        
        Crohn's
        
        Ulcerative colitis
      - Diversion Colitis
        
        Nonspecific inflammatory disorder that occurs in segments of colon and rectum that are diverted from faecal stream by surgery
        Marked lymphoid follicular hyperplasia
      - Microscopic colitis
        
        Lymphocytic colitis - celiac
        
        Normal subepithelial collagen layer
        Increased IEL
        Increased lymphocytes/plasma cells in lamina propria
        
        Collagenous colitis
        
        Thickened subepithelial collagen band
        Increased IEL
        Increased lymphocytes/plasma cells in lamina propria
  - - - Non-neoplastic vs neoplastic
        Sessile vs pedunculated vs serrated
        Sporadic vs syndromic
        
        Sessile - polyps which occur without stalks
        Pedunculated - proliferation of cells adjacent to the polyp and traction on the luminal protrusion - combine to create a stalk as sessile polyps enlarge
        Serrated - epithelial lesions of the colon and rectum with “sawtooth” pattern on the polyp's surface and crypt epithelium
    - - Disorganised, tumourlike growths of an abnormal mixture of cells and tissues native to that area
      - Syndromic polyps - malignancy potential
        Sporadic polyps - generally relatively benign
      - Subtypes
        
        Juvenile polyposis (retention polyps)
        
        Polypoidal mucosal malformations with dilated mucin filled cysts and inflamed lamina propria
        Rectal polyp with rectal bleeding, melena, iron deficiency anaemia, prolapsing polyp
        Seen as pedunculated, smooth-surfaced, reddish lesions
        
        Peutz-jeghers syndrome
        
        Cancerous syndrome with mucocutaneous pigmentation and multiple hamartomatous polyps in GI tract - most common
        Large pedunculated polyps with lobulated contour
        Arborizing network of connective tissue, smooth muscle, lamina propria and glands lined by normal-appearing intestinal epithelium
    - - Decreased epithelial turnover and delayed shedding of surface epithelial cells - pileup of goblet cells
        Small and sessile lesions
    - - non-neoplastic lesions, made of surviving normal/regenerative colonic mucosa and inflammatory granulation tissue surrounded by ulcerations
    - - Sessile serrated adenoma
        
        Serrated lesions, usually with blob of mucus
        Hyperplastic, sessile serrated, traditional serrated adenoma
        
        Adenocarcinoma arising in an adenomatous polyp (adenoma-carcinoma)
        
        Usually result of tubular or tubulovilous adenoma or adenocarcinoma invading into submucosa - malignant polyps
    - - Familial adenomatous polyps
        
        Autosomal dominant disorder marked by appearance of numerous colorectal adenomas by the teenage years
      - Hereditary nonpolyposis colorectal cancer (HNPCC)
        
        Lynch syndrome - familial clustering of cancers at multiple sites
        Adenomas present, but not excessive
  - - - Conventional adenomas - may cause obstruction and enlargement mimicing changes of acute appendicitis
      - Mucinous cystadenoma
        
        Mucocele - dilated appendic filled with mucin, stemming from obstructed appendix containing inspissated mucin
        
        Pseudomyxoma peritonei (Jelly Belly) - syndrome when appendiceal mucinous tumour develops and ruptures - seeding peritoneum
  - - - Precursor lesions
        
        Condyloma acuminatum - anogenital warts caused by HPV
        Anal intraepithelial neoplasia (AIN)
        Extramammary Paget disease (adenocarcinoma)
  - - - Strutura - colonic, anorectall
        Endocrine - Diabetes, hypothyroidism
        Metabolic - hypoK+, Ca2+, uaremia
        Infiltrative - scleroderma, amyloidosis
        Neurological
        Psychological
        Drugs
    - - Hirschsprung's disease - absence of ganglion cells in plexi, short segment of rectum
        Anorectal malformation
        Spinal cord abnormalities - spina bifida
        Cystic fibrosis
  - - - Osmotic - excess of osmotically active particles in lumen causes increased, passive fluid movement into bowel lumen down osmotic gradient
      - Secretory - excess amounts of fluid secreted due to toxin production or genetic abnormalities in enterocytes
        Cholera
      - Inflammatory - inflammatory changes in bowel wall caused by infection or auto-immune conditions
      - Fatty (malabsorptive/maldigestive) - greasy, large volume, pale stools
    - - Salmonella (gram -ve rod flagellate)
        
        Typhoidal
        
        S.enterica ser. Typhi
        S.enterica ser. Paratyphi
        
        Diffuse abdominal pain, rose spots, splenomegaly, relative bradycardia
        
        Non-typhoidal
        
        S. enterica ser. Enteriditis
        S. enterica ser. Typhimurium
      - Campylobacter jejuni (gram -ve helical)
        
        Linked with Guillain Barre syndrome - immune-mediated demyelinating polyneuropathy of PNS
      - Vibrio cholerae (gram -ve, comma shaped rods)
      - E.coli (gram -ve rod)
        
        Toxins produced by bacteria, invasion of enterocytes
      - Clostridium difficle (gram + spore-forming rod
      - Rotavirus (dsRNA)
      - Norovirus (+ve sense ssRNA)
      - Treatment
        
        Fluid repletion
        Antimotility agents - loperamide
        Bismuth subsalicylate
        Probiotics
        
        Antibiotics
        
        C. Difficile - metronidazole, vancomycin
        
        Cholera - doxycycline, tetracycline, azithromycin, ciprofloxacin
- - - - Receptive relaxation - ileocecal sphincter opens, cecum and ascending colon relax, permits ileal chyme to be squirted into cecum and ascending colon
        Haustral shuttling - faeca mass kneaded, water absorption
        Peristaltic contractions - contents of one haustra expelled into next haustrum
        Mass contractions - propels faecal contents into rectum, stored until defectation occurs
      - Colonic reflexes
        
        Defectation reflex - Rectoanal inhibitory reflex (RAIR), Voluntary defecation, overall spinal reflex
        Gastrocolic reflex - mass contraction of colon brought about by stomach distension
        Peristaltic rushes - very intense peristaltic waves that may occur in intestinal obstruction
        Intestinal-intestinal reflex - complete cessation of intestinal motility
  - - - Overall Na+ and Cl- reabsorption, HCO3- secretion
    - - Overall Na+ absorption
    - - Absorption and secretion is tightly balanced
  - - - Beneficial
        
        Vitamin synthesis
        Short-chain fatty acid (SCFA)
        Alter immune reactions
        alter metabolism
        microbiome metabolites
      - Detrimental
        
        Microbiome consume nutrients (Vit C, B12, choline -> deficiency)
        Higher LDL and cholesterol
        Production of NH3 - normally absorbed into portal circulation, detoxified by liver
        
        Liver dysfunction - no detoxification, enters systemic circulation, hyperammonia, hepatic encephalopathy, treat with lactulose
      - Indifferent
        
        Synthesise smelly compounds - contribute to faecal odour
        Formation of hydrogen (from unabsorbed carbohydrates)
        Flatulence