Colorectal Flashcards
What is TME
Employs a precise sharp dissection between the visceral and parietal layers of the endopelvic fascia to ensure en-bloc removal of the perirectal areolar tissue including the lateral and circumferential margins of the mesorectal envelope, lymphatics and vascular/ perineural tumour deposits with the primary rectal cancer.
TME also preserves the autonomic nerves and reduces the risk of presacral bleeding
Parks anal fistula types
type 1: Intersphincteric 45%
- Penetrates internal sphincter and exits between internal and external sphincters
Type 2: Transsphincteric 30%
- Penetrates internal and external sphincter and exits in ischioanal fossa outside sphincters
Type 3: Suprasphincteric/ supralevator 20%
- Penetrates internal sphincter, travels superiorly to supralevator space and then exits through levator to ischioanal fossa outside the sphincters
Type 4: Extrasphincteric 5%
- High fistula that penetrates rectal wall above levator (extrinsic to the sphincters) and exits in the ischioanal space
Superficial sphincter - doesnt involve muscle - just superficial skin.
Goodsall’s rule
Fistula in ano
- Fistulae anterior to 3 and 9 o clock will drain radially to external openings (procided they are within 3cm of anal verge)
- Fistulae posterior to 3 and 9 o clock will drain to an opening in the midline at 6 o clock
Pathophysiology of haemorrhoids
Pathological and symptomatic dysfunction of the anorectal mucosal haemorrhoidal cushions
- Decreased venous return to the middle rectal and superior rectal veins caused by straining, pregnancy, obesity and the erect position leads to congestion of the sinusoids
- Relaxation and disruption of the longitudinal conjoint coat and Treitz’s muscle fibres and PArkes ligaments allow the haemorrhoidal cushion to slide on the internal sphincter and prolapse
- Repeated sliding of the haemorrhoid leads to mucosal congestion, further damage and prolapse which perpetuates the cycle
Genetic colorectal conditions
Lynch syndrome - 4% of CRC. MMR mutation of MLH1, MSH2, MSH6 or PMS2. LAMPS, other cancers CESOPUBS.
HNPCC
FAP - APC mutation, B catenin and WNT pathway, crypt cell proliferation. accelarated adenoma-carcinoma. 100% risk of CRC. Other cancers: thyroid, duodenal, biliary tree, stomach, SB, adrenal cortec, desmoids, skin, CNS, bone, dental
Peutz Jeghers
MYH associated polyposis (MAP)
Juvenile polyposis syndrome
Spigelman criteria
Severity classification system describing the frequency of endoscopic surveillance required for FAP patients with duodenal polyps.
Based on 4 factors (number of polyps, size of polyps, histological subtype and degree of dysplasia).
Pathogenesis of crohns disease
Interaction between environmental factors and genetics factors leading to immune dysregulation and chronic inflammation
- Unknown cause of immune response to initial mucosal damage but gut microflora disturbance thought to play a role.
- Increased vascular permeability leading to mucosal damage, activation of Th cells and macrophages.
- Release of cytokines and TNFa, IL2 and IL6
- Activation of immune system and chronic inflammatory process occurs
Crohn’s disease macroscopic and microscopic features plus extra-intestinal manifestations
Macro:
- intra-luminal: fibrinous exudate, apthous ulcers, cobblestoning, skip lesions, strictures, deep fissures
- extraluminal: Abscesses, fistulae, fat wrapping, stiffness of bowel wall and mesentary
Microscopic:
Transmural inflammation. Lymphoid aggregates in wall. Granulomatous inflammation.
Extra-intestinal manifestations: Arthropathies, eye disease, erythema nodosum, pyoderma gangrenosum, PSC, amyloidosis.
Anal cancer management
Chemoradiotherapy (Nigro protocol)
- 5FU + mitomycin C
- Radiotherapy to tumour + LN basins. Boost to groin if positive nodes
Re-evaluate 12 weeks, and for APR if tumour still present on biopsy or recurrent
Staging of anal cancer
T1:<2cm
T2:2-5cm
T3: >5cm
T4: Invading nearby structures
N0: No nodes
N1a: inguinal, mesorectal or inte iliac nodes
N1b: External iliac nodes
N1c: External iliac + N1a nodes
Alvarado score
Scoring system used to determine likelihood of acute appendicitis (out of 10, 1-4 unlikely, 5-6 moderately likely, 7-10, highly likely).
8 criteria (3 sx, 3 signs, 2 labs)
- migratory RIF pain
- anorexia
- N&V
- RLQ tenderness (2 pts)
- Rebound tenderness
- Fever
- WBC > 10 (2 pts)
- Left shift
Severity criteria for UC
Truelove and Witts
- > 6 blood stools per day
- Raised CRP > 30
- Hb < 100
- Temp > 37.8
- HR > 100
Mayo (out of 12)
- Stool frequency
- Presence of blood in stools
- Endoscopic severity
- Physicians global assessment
Oxford/ Travis criteria (85% chance of needing acute colectomy if after 3 days of IV steroids there are:)
- > 8 stools per day
- 3-8 stools and CRP > 45
Definition of toxic megacolon
Acute dilatation of the colon > 6cm + 3 of systemic compromise (Fever, tachycardia, anaemia, neutrophilia) + one of (dehydration, hypotension, electrolyte disturbance, altered GCS)
