Colorectal Flashcards
Types of colonic polyps
Non-neoplastic
- Hyperplastic
- Inflammatory/pseudopolyps
- Hamartoma/congenital/juvenile
Neoplastic
- Tubular (90%), tubulovillous (10%), villous (1%)
- Familial, sporadic
- Adenocarcinoma
3 features of a polyp that increase risk of malignancy
- Size: >2cm
- Type: villous
- Degree of dysplasia: severe
Familial Adenomatous Polyposis (FAP)
- Most common polyposis syndrome
- Autosomal dominant condition
- Characterised by 100’s-1000’s of adenomas in the colorectal mucosa by 20-30yrs old
- Lifetime risk of CRC = 100%
- Also at risk of other tumours - upper GIT, CNS
- Patho: defect in APC tumour suppressor gene
Hereditary Nonpolyposis Colorectal Cancer (HNPCC) aka Lynch syndrome
- Autosomal dominant disorder in which colon cancers arise in discrete adenomas in proximal colon
- Germline mutation in one of several genes involved in the mismatch repair system, most commonly hMSH2 or hMLH1
- Only 1 of 2 copies of the gene is defective -> individuals are at risk of inactivation of the remaining good gene copy -> CRC
- Amsterdam criteria
- Colonoscopy screening for high-risk CRC individuals every 1-2 years
- Starting at age 25 or 5 years before the earliest diagnosis in the family
Colorectal Cancer - risk factors
Non-modifiable:
- Age >50 (average 72), sex (m), previous polyps or previous CRC, first degree relatives with a hx of bowel cancer, hereditary syndromes - FAP, HNPCC, MYH, hx IBD
Modifiable:
- Smoking, obesity, high meat/fat diet, low fibre
Colorectal Cancer - symptoms
- PR bleeding
- Change in bowel habit - constipation alternating with increased frequency
- Tenesmus
- Anal symptoms - soreness, discomfort, lumps, pain
- Abdo pain - left sided colicky abdominal pain
- Fatigue, weight loss
- Iron deficiency symptoms - fatigue, dyspnoea, chest pain
Colorectal Cancer - Examination
General - pale, fatigued, cachectic
Vitals - tachy (anaemic)
- Hands - koilonychia, pallor of creases
- Face - conjunctival pallor, angular stomatitis, glossitis
- Neck - palpate Virchow node (left supraclavicular)
Abdomen - Inspection - scars, masses - Palpation - tenderness, masses, hepatomegaly - Auscultate - Percussion DRE
Other systems - CV, Resp
Colorectal Cancer - Investigations
Bloods
- FBC - Hb, WBC
- Iron studies
- LFT’s, UEC
- CEA
Imaging
- Colonoscopy + biopsy
- CT - chest, abdo, pelvis
- Rectal cancer - endoanal ultrasound, MRI
Colorectal Cancer - Screening
General Population
- Faecal occult blood testing (iFOBT) - every 2 years for adults aged 50-74yrs
- 2 stool samples
- If 1 is positive -> GP -> colonoscopy
Family Hx of CRC
- For those with a 1st degree relative diagnosed with CRC at 55yrs or older -> consider FOBT every 2 yrs from 45yrs old
- People with 1st degree relative diagnosed with CRC <55yrs of age -> FOBT should be performed every 2 yrs from 40-50, and colonoscopy every 5 yrs from 50-74, consider low dose aspirin (100mg daily)
High Risk Familial Syndromes
- FAP - start surveillance at 10-15yrs old - colonoscopy, once adenoma has been found, need colonoscopy every 12 months
Pilonidal Disease
- Pilonidal disease results from loose hairs in the gluteal cleft skin that causes a foreign body reaction -> midline pits and occasionally secondary infection
- This may result in abscess, cyst or sinus tract that grows under the skin of the gluteal cleft
- Most common between 15-24yrs
- 3x more common in men
- TNM
Stage 0: carcinoma in situ - tumour contained within the mucosa (Tis, N0, M0)
Stage 1: tumour invades submucosa or muscularis propria, no lymph node involvement, no mets (T1 or T2, N0, M0)
Stage 2: tumour invades muscularis propria into submucosa, tumour perforates the visceral peritoneum or directly invades other organs or structures (T3, N0, M0)
Stage 3: any degree of bowel wall perforation with regional lymph node mets (T, N1, N2, M0)
Stage 4: any invasion of the bowel wall +/- lymph node mets, but with evidence of distant metastasis (any T, any N, M1)
- Staging Duke’s Criteria
Stage A: lesions limited to the bowel wall
Stage B: extending through the wall
Stage C: extending to nodal or regional mets
Stage D: extending to distant mets
Colorectal Cancer - Surgical Options
Right Hemicolectomy/Extended Right Hemicolectomy
- Surgical approach for caecal or ascending tumours
- The ileocolic, right colic and right branch of middle colic vessels are divided and removed
- Extended - performed for transverse colon cancers
Left Hemicolectomy
- Surgical approach for descending colon cancer
- Left branch of middle colic vessels, IMV and left colic vessels are removed
Sigmoidcolectomy
- Surgical approach for sigmoid colon tumours
Low Anterior Resection (LAR)
- Surgical approach for high rectal tumours (>5cm from anus)
- Leaves rectal sphincter intact and functioning
Abdominoperineal Resection (APR)
- Surgical approach for low rectal tumours (<5cm from anus)
- Involves excision of distal colon, rectum and anal sphincters -> permanent colostomy
Hartmann’s Procedure
- Used in emergency bowel surgery (bowel obstruction or perforation)
- Involves a complete resection of the recto-sigmoid colon with the formation of an end-colostomy and the closure of the rectal stump
Haemorrhoids - definition/pathophys
- Haemorrhoid = abnormal swelling or enlargement of anal vascular cushions
- The anal vascular cushions are specialised vascular cushions that are located in the submucosal space in the anal canal
- They are a normal part of human anatomy
- Over time, as supportive CT weakens, the vascular cushions enlarge and become symptomatic -> haemorrhoids
Haemorrhoids - Types
Internal
- Located above the dentate line, covered by mucosa, do not have sensory innervations
External
- Located below the dentate line, covered by squamous epithelium and have sensory innervation
