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Colorectal Flashcards

1
Q

LBGIT is bleeding from a source distal to ___

A

Ligament of Treitz

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2
Q

What is haematochezia?

A

Gross, fresh blood seen on toilet paper after defecation or mixed with stools

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3
Q

All patients over __ with PR bleed should be scheduled for ___

A

50, colonoscopy

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4
Q

Differentials for different PR bleed occurrence patterns

A

On toilet paper, dripping into bowl: haemorrhoids

Coating stools: distal bleed

Mixed into stools: proximal bleed

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5
Q

Ddx for different bloody stool colours

A

Frank red: left colon bleed
Maroon/mixed into stool: right colon
Melena: UBGIT/right colon

Clots: LBGIT, unlikely to be UBGIT

*Blood takes 14 hours to be broken down in the intestine. >14 hours = melena.

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6
Q

Pain on defecation can indicate

A

rectal tumours, anal fissures, ischemic colitis

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7
Q

What is spurious diarrhea?

A

occurs when the feces become so hard that they cannot be expelled and fecal fluid will flow around the block.

There are a number of features that clinically characterize overflow diarrhea, also called spurious diarrhea:
1. Only fluids are expelled.
2. It most often has the colour of feces.
3. It is not accompanied by abdominal pain.
4. It is often difficult for the patient to reach the toilet before it is expelled.
5. If a gloved finger is put down into the fluid it will feel threadlike due to mucus in the stool.
6. The patient does not have fever.

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8
Q

What is tenesmus & what can it indicate?

A

Frequent & urgent feeling of need to defecate even when bowels are already empty

Rectal tumours, infective/inflammatory colitis, radiation proctitis

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9
Q

What does age of pt presenting with LBGIT clue us in on?

A

Young: usually benign (haemorrhoids, fissures, inflammatory bowel disease)

Older: diverticular disease, colon cancer, ischemic colitis

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10
Q

Types of colitis

A

Infective - viral, bacterial, parasite
Inflammatory - UC, Crohns
Ischaemic - watershed areas
Chemical - NSAID, anti-angina
Radiation - radiation proctitis

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11
Q

Endoscopy is only useful in ___ pts with LBGIT as they can tolerate ___

A

haemodynamically stable
bowel prep

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12
Q

If pt is haemodynamically unstable, can use __ to diagnose bleeding site

A

CT mesenteric angiogram - content extravasation in bowel lumen

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13
Q

Urine output may drop below ___ in haemodynamically unstable pts

A

0.5ml/kg/hr

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14
Q

If bleeding is detected on CT mesenteric angiogram, a ___ can be performed for therapeutic intervention

A

Selective mesenteric angiography + angioembolisation

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15
Q

Indications for exploratory laparotomy in LBGIT

A

Persistent/recurrent PR bleed despite non-operative attempts to localise bleed

Haemodynamically unstable pts requiring >6 to 10 units of PCT

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16
Q

Risk factors for ischaemic colitis

A

1) Occlusive vascular disease
- thrombosis/emboli

2) Non-occlusive
- Hypotension
- Medication: chemo, OC
- Cardiac: atrial fib, atherosclerosis
- hypercoagulability states
- obstructions, vasculitis

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17
Q

Blood supply of colon & rectum

A

SMA: ileocolic, right colic, middle colic (supplies up to 2/3rd of transverse colon)

IMA: left colic, sigmoid, rectal

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18
Q

Watershed areas of the colon

A

Right colon - vulnerable in low flow states (ileocolic is a terminal branch of SMA)

Splenic flexure - supply from both SMA & IMA

Rectosigmoid junction - vulnerable in IMA stenosis

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19
Q

Clinical progression of ischemic colitis

A

1) Hyperactive phase: severe pain with loose, bloody stools

2) Paralytic phase: pain is more continuous & diffuse, abdomen tender & distended, no bowel sounds

3) Shock phase: massive fluid, protein, electrolytes leak through gangrenous mucosa. Severe dehydration + shock + metabolic acidosis develops

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20
Q

Transmural ischemia presents with __

A

intestinal pneumatosis - air in the walls of the bowel
portal venous gas
lack of bowel wall enhancement

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21
Q

___ is gold standard for diagnosing ischemic colitis

A

Endoscopy
(colonoscopy/sigmoidoscopy)

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22
Q

Colon cancer pts diagnosed mostly at ___ years old. Younger must suspect ___

A

60-70

HNPCC, FAP, pre-existing IBD

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23
Q

Risk factors for colon CA

A

Modifiable:
1) Diet - red/processed meat, alcohol
2) Smoking
3) Obesity

Non-modifiable
1) Age
2) Ethnicity (chinese)
3) Family history
4) Hereditary CRC - FAP, peutz-jeghers
5) Familial cancer - HNPCC (Amsterdam criteria)
6) Personal history - IBD, large polyps, radiation

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24
Q

HNPCC (familial) & right sided CA (sporadic) associated with ____

FAP (familial) & left sided CA (sporadic) associated with ___

A

microsatellite instability

chromosomal instability

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25
85% of sporadic CRC caused by ___, 15% caused by ___
chromosomal instability (loss of APC, KRAS, p53) microsatellite instability (defect in DNA mismatch repair genes MSH2, MSH6, MLH1, PMS1, PMS2) **sporadic cancers that have microsatellite instability have better prognosis
26
In general, ___ CRC more common
left sided
27
Red flags symptoms for colon cancer
PR Bleeding Spurious diarrhea Diminished stool calibre - pencil thin stools Tenesmus Alternating constipation & diarrhea
28
RIght sided CRC more likely to present with ___
symptomatic anaemia - bleeding from right side is usually occult
29
___ CRC more likely to cause intestinal obstruction. Why?
Left sided Stools are more well formed + competent ileocaecal valve = closed loop obstruction
30
Rectal tumours tend to present with ___
tenesmus, diminished stool calibre, mucoid stools
31
Complications of colon tumours
1) Bleeding - anaemia 2) Obstruction - cardinal symptoms of IO (abdominal distension, pain, vomiting, obstipation) 3) Perforation - peritonitis, intra-abdominal sepsis 4) Fistula - fecaluria, pneumaturia, recurrent UTI, recto-vagina fistula 5) Invasion - pain, LUTS (bladder)
32
Most common metastasis site of CRC
Liver Then lung
33
Important to measure ___ levels preoperatively as it is ___
carcinoembryonic antigen (CEA) useful prognostic and surveillance tumour marker in CRC (level correlates with disease burden)
34
Investigation modality Diagnosis of CRC by ____ Staging by ___
Colonoscopy CT TAP - to determine depth of invasion and metastasis to other organs
35
Types of colectomy on location of primary tumour
Right hemi: caecum, AC, hepatic flexure tumour Extended right hemi: everything above + mid TC Left hemi: distal TC, splenic, DC, sigmoid Sigmoid colectomy: sigmoid colon Anterior resection: Partial or complete removal of rectum
36
What is Hartmann's procedure?
Surgical resection of colon, closure of rectal stump Temporary end colostomy opened Used in emergency settings when immediate anastomosis is not possible
37
Lung protective measures to prevent post-op complications (atelectasis, pneumonia)
Incentive spirometry Chest physiotherapy
38
Where does rectal cancer occur? How to define the border?
within 15cm of anal verge anal verge: junction between stratified squamous non-keratinising & stratified squamous keratinising epithelium in the anal canal
39
Blood supply to rectum
superior rectal artery (from IMA) middle & lower rectal artery (from internal iliac artery)
40
What divides the anal (rectal) canal? Epithelium, venous drainage, nerve supply, lymphatic drainge of each
Pectinate (dentate) line - divides upper 2/3rd from lower 1/3rd Upper 2/3: simple columnar epithelium, portal venous drainage, autonomic nerves (inf hypogastric plexus), drains to abdominal nodes Lower 1/3: stratified squamous epithelium, systemic venous drainage, somatic nerve (inferior rectal nerve), drains to superficial inguinal
41
Imaging: ____ is superior to ___ for rectal cancer staging
MRI > CT
42
What is an anterior resection?
Anterior approach to resect the recto-sigmoid colon with primary anastomosis between descending colon and rectum Low anterior resection occurs below peritoneal reflection, spares the anal sphincters
43
What is a diverting/defunctioning ileostomy used for?
Loop of ileum that is opened up into the surface of the abdomen, to divert faecal matter out. Used after distal colon/anterior resection to prevent anastomotic leaks while the surgical site is healing.
44
When is an abdominoperineal resection indicated?
Removal of sigmoid colon, rectum, anal sphincter complex When tumour involves sphincter complex with inadequate distal margins
45
What laxative is given for bowel prep prior to colonoscopy?
Polyethylene Glycol (PEG) - 3-4L over 2 doses
46
What kind of colon polyps have malignant potential/are malignant?
Sessile serrated polyps - pre-malignant Adenomas - Larger size, more villous features are more pre-malignant risk (2/3 of polyps are these) Adenocarcinomas - malignant, invades through muscularis mucosa and into submucosal layer of bowel wall
47
Most common type of non-neoplastic (benign) polyps found
Hyperplastic polyps - normal epithelial cells accumulating on mucosal surface
48
How often to do colonoscopy if polyps are found?
Low risk polyps - 5 years High risk polyps - 3 years
49
How often to do colonoscopy if first degree relative had colon cancer before 60yo OR 2 or more 1st deg relatives with colon cancer?
Starting from 40 OR 10 years prior to age of diagnosis (whever earlier) once every 5 years
50
How often colonoscopy if first degree relative had colon cancer after 60?
starting from 50 years old, once every 10 years
51
When is colonoscopy indicated every 1-2 years
family history of FAP (annually) family history of HNPCC personal history of IBD
52
What is Peutz-Jeghers Syndrome?
AD condition, multiple hamartomatous polyps (colon, small intestine, stomach), muco-cutaneous pigmentation around perioral & buccal mucosa High risk of CRC, breast, pancreatic, lung, uterine, gastric cancers
53
What is Juvenile Polyposis Syndrome?
AD condition - multiple harmatomatous polyps in colon & upper GI Increased risk of other GI malignancies: small bowel, pancreatic, stomach cancer
54
What is familial adenomatous polyposis?
AD condition - mutations in APC tumour suppressor gene Patients have >100 adenomatous polyps by age 35, 100% of pts develop CRC
55
What is Lynch syndrome?
AD condition - mutations in DNA mismatch repair genes Lynch syndrome I - familial Lynch syndrome II - Associated with HNPCC
56
What are end, loop, barrel stomas?
End - end of the intestine is transected, exteriorised and fashioned as a stoma Loop - loop of intestine is exteriorised and fashioned a stoma Barrel - intestine is severed, brought out as 2 ends to fashion a stoma (eg. ileo-colic stoma)
57
Colostomy commonly located at ___, ileostomy located at ___
left iliac fossa right iliac fossa
58
A bowel in a stoma that forms a raised spout above the skin is like to be a ___
ileostomy sometimes urostomy
59
A loop ileostomy/colostomy would present with ___ ___ lumens
two adjacent lumens
60
What is diverticular disease?
Psuedo-diverticular outpouching of colonic mucosa & submucosa at antimesenteric side Diverticulitis - when the diverticula becomes inflamed
61
What causes diverticular disease?
Increased intraluminal pressure Degenerative changes in colonic wall - weakening of collagen structure w age
62
Complications of diverticular disease
1) Acute diverticulitis - underlying macro/micro perforation of diverticulum secondary to inflammation & focal necrosis 2) Chronic diverticulitis 3) Complicated diverticulitis - LGIT haemorrhage - Fistula - Perforation - Bowel obstruction
63
Gold standard in diagnosing diverticulitis
CT AP

General Surgery (13 decks)

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