COLORECTAL Flashcards
Give 2 genetic mutation types that are known to predispose to CRC, including their inheritance pattern:
Both AD
HNPCC (Lynch syndrome) - MSH2 and MLH1 are MMR genes with mutations causing defects in DNA repair
APC is a tumour suppressor gene = FAP syndrome. 100% with get CRC
75% of CRC is sporadic, developing in people with no specific risk factors. However, some risk factors are recognised. Give some:
IBD
Low fibre, high processed meat diet
Increased age
Male
FHx
Smoking
Alcohol
Amsterdam criteria for diagnosing Lynch syndrome:
3 or more family members with colon cancer
Cases spanning at least 2 generations
At least one member dx before 50
Give a variant of FAP that has extra-colonic features:
Gardner syndrome - also osteosarcoma of the skull and mandible, retinal pigmentation,, thyroid carcinoma and epidermoid cysts
Which operation do most patients with FAP undergo in their twenties?
Total proctocolectomy and ileo-anal ouch anastomosis
What does the FIT test look for specifically?
Human haemoglobin in stool
How often is bowel cancer screening offered?
Every 2 years
FIT testing should be used to guide referral for suspected CRC in adults, with >10 indicating referral. Who should be considered for a FIT test and referral?
Abdominal mass
Change in bowel habit
>40 with weight loss + abdominal pain
<50 with rectal bleeding + [abdo pain OR weight loss]
>50 with rectal bleeding OR weight los s/ abdo pain
>60 with anaemia even without iron deficiency
Which tumour marker should NOT be used for diagnosis of CRC but can monitor disease progression ?
CEA
An elevated CEA at abseline may indicate a worse prognosis
Gold standard for diagnosis of CRC:
Colonoscopy with biopsy
?sigmoidoscopy if only rectal bleeding symptom?
3 further imaging techniques for staging a CRC, and when they might be indicated:
CT CAP for distal mets and local invasion
MRI rectum for rectal cancer only , depth and need for pre-op chemo
Endoanal US for early rectal cancers
CRC is mostly staged using TNM but Duke’s is still sometimes used. Describe it:
1 confined to mucosa and muscle
2 extends through muscle of bowel wall
3 lymph node involvement
4 metastatic
What is removed in a right hemicolectomy?
caecum, ascending and prox transverse
What is removed in a left hemicolectomy?
diatl transverse + desc
What is removed in a high anterior resection?
sigmoid
What is removed in a low anterior resection?
sigmoid + upper rectum
What is removed in an abdomino-perineal resection?
Rectum + anus, sutures over anus.
What is removed in a Hartmann’s procedure?
Rectosigmoid colon + colostomy formation
What does low anterior resection syndrome refer to?
Urgency and frequency of bowel movements, faecal incontinence, flatulence, due to removal of part of the rectum
Mechanical bowel obstruction pathophysiology/ features:
Gross dilation of bowel proximal to the blockage, increased peristalsis of the bowel, secretions of large volumes of fluid with lots of electrolytes, causing third spacing.
Urgent fluid resus is needed.
Abdo pain, vomiting, distension, constipation, cramp due to peristalsis.
DDx for patients presenting with a bowel obstruction:
Paralytic ileus
Pseudoobstruction (adynamic bowel due to disruption of autonomic nervous system)
Toxic megacolon
Constipation
Investigations inc labs and imaging for bowel obstruction:
FBC, UEs, Renal fucniton closely due ot dehydration rik, Gand Save,
VBG for lactate and metabolic derangment
CT Contrast AP, will also allow underlying cause but AXR would not
AXR
Small dilated >3cm, central valvulae conniventes
Large = >6 or >9 if caecum, haustra
AXR findings in small vs large bowel obstruction:
AXR
Small dilated >3cm, central valvulae conniventes
Large = >6 or >9 if caecum, haustra
A patient has been treated conservatively for a bowel obstruction with NG insertion, fluid therapy, catheterisation and analgesia. What further study can you do if it is not resolving / you’re not sure?
Contrast study / XR
If contrast goes past blockage = good sign
Gastrograffin dye?
When is surgical management for bowel obstruction indicated?
> 48 hours no improvement
Ischaemia or closed loop bowel obstruction
Cause requiring surgical correction e.g. strangulated hernia, obstructing tumour
Causes of small vs large bowel obstruction:
Small = adhesions and hernias
Large = malignancy, diverticular disease, volvulus
4 anal glands are located in the intersphincteric space; name these 4 glands, which have the potential to cause anorectal abscesses:
Perianal
Ischiorectal
Intersphincteric
Supralevator
Patients with an anorectal abscess without any known risk factors such as fistula-in-ano or other rectal pathology should have what test done?
HbA1c for DM
3 common causative organisms in ano-rectal abscess:
E.coli
Enterococcus
Bacterioides
What is the cancer risk % in FAP?
100%
Common presenting complaint in Peutz-Jeghers syndrome:
SBO due to intussusception - hamartomatous polyps in the GI tract
+ pigmented lesions on lips, face, palms, soles
Mechanism of orlistat, including NICE criteria:
Pancreatic lipase inhibitor
For obesity
> BMI28 + risk factors
> =30
Mechanism of liraglutide, including NICE criteria
GLP-1 analogue
Prediabetic hyperglcaemia 42-47
BMI >=35
Positions of normal haemorrhoidal cushions:
3 oclock
7 oclock
11 oclock
4 symptoms of haemorrhoids:
Painless rectal bleeding
Pruritis
?pain if thrombosed
Soiling
Incomplete emptying
dragging sensation
A haemorrhoid can be manually reduced. What grade is it?
III
A haemorrhoid prolapses on defecation but reduces spontaneously. What grade is it?
II
First line managements of haemorrhoids:
increase dietary fibre and fluid intake
topical local anaesthetics and steroids may help symptoms
What window of time do patients need to present in for referral to be considered for surgical excision of an acutely thrombosed external haemorrhoid?
72 hours
Which line indicates whether a haemorrhoid is internal or external?
dentate / pectinate
