Colorectal Flashcards
How do most colorectal cancers arise and what is the most common type?
From polyps to form adenocarcinomas
What are the layers of the bowel wall, from lumen outwards?
Mucosa - contains connective tissue lamina propria and muscularis mucosa.
Submucosa - connective tissue, glands, vessels, lymph nodes, nerves
Muscularis propria
Subserosa
Serosa
What are risk factors for colorectal cancer?
Family history Hereditary syndromes Inflammatory bowel disease Ethnicity Radiotherapy Obesity Diabetes mellitus Smoking Western diet - low fibre, high fat, red/processed meat
Increased exercise is protective
What hereditary syndromes increase the risk of CRC?
Hereditary nonpolyposis colorectal cancer/Lynch syndrome - autosomal dominant mutation
FAP - familial adenomatous polyposis - autosomal dominant mutation of APC (tumour suppressor gene)
Development of polyps that could undergo malignant change
Require annual colonoscopy
MYH associated polyposis
Serrated polyposis
Juvenile polyposis
Peutz-Jeghers syndrome
What is the adenoma-carcinoma sequence?
Mutations accumulate
Normal epithelium develops adenomas which become progressively more dysplastic = carcinoma
APC mutation leads to hyper proliferative epithelium, then KRAS mutation of proto-oncogene - oncogene.
The mutation of p53 and SMAD4 leads to development of carcinoma
Where does CRC most commonly occur?
Rectum and sigmoid colon
Most commonly affect the left side of the colon
Where do CRCs commonly spread?
Liver most commonly
Rectal cancers commonly associated with lung mets due to haematogenous spread via inferior rectal vein and IVC
What are the clinical features of CRC?
Change in bowel habit Weight loss, malaise Tenesmus, PR bleeding Abdominal pain Pallor Abnormal PR exam, mass
How does the presentation of right sided to left sided colon cancer differ?
RS: weight loss, weakness, rarely obstruction, iron deficiency anaemia, late
LS: constipation, abdo pain, alternating bowels, rectal bleeding, bright red PR bleeding, large bowel obstruction
How does a rectal cancer present?
Obstruction, tenesmus, bleeding
Bright red PR bleeding
Palpable mass on DRE
How can mets present with liver involvement?
Hepatomegaly
Jaundice
Abdo pain
Lymphadenopathy
What appearance can left sided lesions present as?
Have a tendency to grow circumferentially, creating an apple core appearance
So leads to narrowing of the lumen - obstruction
What screening is available?
FIT test - Faecal Immunochemical test for presence of blood in the stool
56-74 home test kit every 2 years
Those with abnormal results will be invited for colonoscopy
One-off flexible sigmoidoscopy paused since COVID19 - aged 55
Who should be referred for two week wait?
Most can be sent straight to test for colonoscopy unless contraindication/complication
Aged 40 + with unexplained weight loss and abdo pain
Aged 50 + and unexplained rectal bleeding
Aged 60 + with iron deficiency anaemia, change in bowel habits
Test shows occult blood
Consider patients with rectal or abdominal mass
What are the investigations for suspected CRC?
Colonoscopy is the gold standard investigation
CT pneumocolon - but cannot take biopsy or remove polyps
CT abdomen pelvis with or without contrast
Bloods - FBC, iron, transferrin, TIBC, renal function, LFT, clotting
Tumour markers - CEA
MRI liver, rectum
Endoanal USS
PET/CT for staging
When should neoadjuvant therapy be offered?
Rectal cancer T1-T2, N1-N2, M0
Colonic cancer with cT4 consider use of chemo
What are some examples of adjuvant therapy?
FOLFOX - Folinic acid, Fluorouracil, Oxaliplatin
CAPOX - Capecitabine and Oxaliplatin
What is the Duke staging?
A - tumour confined to mucosa
B - growth into muscularis propria +- serosa
C - spread to lymph nodes
D - distant mets; liver, lung, bones
What signs would suggest advanced colorectal cancer?
Hepatomegaly
Jaundice
When is a right hemicolectomy performed? What is done during the procedure?
Any ascending colon tumours
Part or all of ascending colon and cecum removed. Colon anastomosed to small intestine (ileo-colic)
When is a left hemicolectomy performed? What is done during the procedure?
Any descending colon tumours
Part or all of descending colon removed. Transverse colon anastomosed to rectum (colo-colic)
When is a sigmoid colectomy performed? What is done during the procedure?
Tumours affecting the sigmoid colon
Part/all of sigmoid colon removed. Descending colon connected to rectum (colo-rectal)
When is an anterior resection performed? What is done during the procedure?
High anterior resection: sigmoid tumours
Anterior resection: rectal tumours
sigmoid colon and portion of rectum removed. Colorectal anastomosis formed
+TME (removal of mesorectal fat and lymph)
When is an abdo-perineal resection performed? What is done during the procedure?
Lower rectal tumours and any tumour involving the sphincter
removes the anus, rectum, and sigmoid colon. No anastomosis
Where does a HNPCC colon cancer normally affect?
What other cancers is HNPCC associated with?
Proximal colon
Endometrial
What are some complications of colorectal cancer surgical management?
Anastomotic leak, adhesions, hernia
Stoma complications:
- parastomal hernia, ischaemia/necrosis, obstruction, skin irritation, prolapse, retraction leading to a poor bag seal
What is Hartmanns’ procedure?
Resection of sigmoid colon, closure of the anorectal stump and formation of end colostomy
What are the advantages and disadvantages of parenteral nutrition?
little patient effort
sepsis
catheter obstruction
thrombosis
refeeding syndrome
What are the advantages and disadvantages of enteral nutrition?
low cost
maintains gut
few infection risks
aspiration risk
tube displacement
gastric distention
risk of malnutrition
What are the most common tumours that cause bony mets?
Prostate, breast, lung
Where are the most common sites for bony mets?
Spine, pelvis, ribs, skull, long bones
What are hamartomas?
Hamartomatous polyps
Non cancerous tumours made of overgrowth of normal cells
Usually asymptomatic
Not associated with malignant transformation or increased risk of colorectal cancer
What are some of the side effects of bowel resection?
Pain, bleeding Thrombosis Paralytic ileus Abdominal adhesions Anastomotic leak Infection Sexual problems - erectile dysfunction, retrograde ejaculation, dry orgasm Bladder problems - urinary incontinence, urgency, frequency
What are some of the side effects of chemo?
Bone marrow suppression Diarrhoea Skin changes - rash, photosensitivity Hair loss Sore mouth and throat - stomatitis, oral mucositis Nausea and vomiting Loss of appetite Pain at the injection site Peripheral neuropathy Liver damage Allergic reactions
What are some agents that can be used in targeted therapy?
Cetuximab
Panitumumab
Bevacizumab
What are treatment options to those with early rectal cancer?
Transanal excisions
Endoscopic submucosal dissection
Total mesorectal excision
Total mesorectal excision with anterior or AP resection in more advanced rectal cancers
What should be performed in a follow up?
Physical examination
Attention to Virchow’s node left supraclavicular node
CEA for elevation
Colonoscopy within 12 months of completing primary treatment, then every 3 years, then every 5 years
Those with rectal cancer undergo flexible sigmoidoscopy
CT chest and abdomen, CXR rectal cancers check for mets
What are some specific side effects in chemotherapy?
5FU/capcitebine - hand and foot skin breakdown
Oxaliplatin - peripheral neuropathy
HTN and GI bleeds - Bevacizumab
Skin rashes - cetuximab
What are the main signs and symptoms of large bowel obstruction?
Absolute constipation Vomiting (late stage) Abdominal distention Loud normal bowel sounds Non tender abdomen Empty rectum
How is large bowel obstruction managed?
Conservatively - drip and suck
fluid resuscitation and intestinal decompression or stenting endoscopy
How would a competent ileo-caecal valve affect large bowel obstruction?
Fluids and materials can pass in but not out meaning the large bowel distends rapidly and the caecum will rupture causing peritonitis
If incompetent, small bowel will also distend so perforation isnt as big a risk
How does small bowel obstruction present?
Colicky umbilical pain Vomiting - pain relief Abdominal distention Tinkling bowel sounds Palpable loops of bowel
How is small bowel obstruction managed?
Drip and suck - fluid resus and tube for decompression
Watch and wait as may need laparotomy
What is a complication of small bowel obstruction?
Strangulated obstruction when blood supply become impaired –> ischaemia and gangrene within 6hrs of onset
