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Surgery > Medbear Colorectal > Flashcards

Medbear Colorectal Flashcards

1
Q

Define massive LBGIT

A
  • Bleeding that requires >3 units of blood over 24 hours
  • In patients with hemodynamic instability
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2
Q

What are the important hereditary CRC syndromes to ask in colorectal CA?

A
  • FAP
  • Lynch Syndrome
  • Peutz-Jeghers Syndrome
  • Juvenile polyposis
    Others: Cowden syndrome, Cronkhite-Canada
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3
Q

How do we diagnose familial cancer syndromes (HNPCC)?

A

Diagnosed with AMSTERDAM CRITERIA (a.k.a 3-2-1 RULE)
- At least 3 relatives with histological confirmed colorectal CA
- At least 2 successive generation involved
- At least 1 of the cancer diagnosed before age of 50

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4
Q

Describe about the APC pathway (adenoma-carcinoma sequence) of colorectal CA.

A

It involves a stepwise accumulation of mutations in a series of oncogenes and tumor suppressor gene:
1. Loss of the APC suppressor gene on 5q21 (Absent in patient with FAP)
2. With the loss of APC, Beta-catenin accumulates and activates the transcriptions of gene (MYC and cyclin D1) which promotes cell proliferation
3. K-RAS (12p12) mutation follows the loss of APC -> activating mutation causing the RAS to keep delivering MITOTIC SIGNALS and PREVENT APOPTOSIS
4. Loss of tumor suppressor gene at 18q21 (SMAD2 and SMAD4) -> leads to UNRESTRAINED CELL GROWTH
5. Loss of p53 (17p13) occurs late in carcinogenesis -> prevents DNA repair/cell apoptosis

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5
Q

Describe the other defect or pathway in colorectal CA
Defects in DNA mismatch repair or microsatellite instability

A
  • Like the APC pathway, there is accumulation of mutations, BUT WITHOUT CLEAR IDENTIFIABLE MORPHOLOGIC CORRELATES (e.g no adenomas)
  • Due to mutations in one of the 5 DNA mismatch repair genes - deficiency in the ability to repair mismatched base pairs in the DNA that are accidentally introduced during replication, this gives rise to HNPCC
  • MLH1 -> most commonly involved in sporadic colorectal CA
  • Loss of DNA mismatch repair genes -> MICROSATELLITE INSTABILITY which affects BAX gene (promote apoptosis) and Type 2 TGF b-receptor (inhibits growth of colonic epithelial cells)
  • Accumulated mutation in these growth-regulating genes leads to colorectal CA

Tumors that arise from this pathway have a better prognosis

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6
Q

State the tumor complications in colorectal CA

A
  • Tumor bleeding -> symptomatic anemia
  • Tumor obstruction -> IO
  • Tumor perforation -> sepsis
  • Tumor fistula -> fecaluria, pneumaturia, recurrent UTI
  • Tumor invasion -> intractable pain (SACRAL N), LUTS (TRIGONE OF BLADDER)
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7
Q

State some metastatic symptoms for colorectal CA

A
  • Constitutional symptoms - LOW, LOA
  • Liver - RHC discomfort, jaundice
  • Lungs - SOB
  • Malignant ascites
  • Bone - bone pain, pathological fractures
  • Brain - altered mental status
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8
Q

State the mode of spread of coloreactal CA

A
  • Direct extension
  • Lymphatics (Progress from paracolic nodes -> para-aortic nodes)
  • Hematogenous (Liver via PORTAL VENOUS SYSTEM, 2nd most common site is the LUNGS)
  • Transcoelomic (CARICNOMATOSIS PERITONEI - via subperitoneal lymphatic)
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9
Q
  1. Define CEA
  2. State the function of CEA
  3. State the conditions when there is a false positive raised in CEA values
  4. What to do if there is a raised CEA level?
A
  1. An oncofetal protein lacking both sensitivity and specificity
  2. Useful prognostic and surveillance tumor marker. It is measured pre-operatively as a baseline level
  3. False positive raised CEA conditions:
    - Smoking
    - Adjuvant therapy with 5-FU
    - Inflammatory states
    - CA (e.g thyroid, breast)
  4. If there is raised CEA
    - Determine if patient is a smoker
    - OGD/colonoscopy
    - Consider CT TAP
    - Consider US thyroid
    - Mammogram for female patients
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10
Q

Describe how you would investigate a case of colorectal CA

A

Establish the diagnosis
- Colonoscopy (Diagnostic and therapeutic)
- Histology
Other investigative tools:
- CT colonography
- Double-contrast barium (APPLE CORE SIGN) and air enema

Staging investigation
- CT TAP

Supportive investigation
- FBC -> assess Hb level
- U/E/Cr -> Cr may be elevated (pre-renal failure) -> increase the risk of contrast nephropathy
- LFT -> Albumin level, any liver mets (elevated ALP)
- CEA (Take a baseline before surgery)
- Erect and supine AXR -> Look for IO, colon cut off sign
- Erect CXR -> TRO air under diaphragm

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11
Q

State the layers of GIT

A
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12
Q

How would you stage colorectal CA based on the TNM staging?

A
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13
Q

State the residual tumor classification (R0, R1, R2)

A
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14
Q

List the pre-operative management of colorectal CA

A
  • Multidisciplinary tumor board meeting
  • Pre-operative investigation + anesthesia referral
  • Mechanical bowel preparation
  • +/- Stoma site discussion with stoma care nursing specialist
  • Prophylactic IV antibiotics (IV ceftriaxone and metronidazole within 30-60 mins of incision)
  • Chest physiotherapy
  • DVT prophylaxis
    1. Subcut low molecular weight heparin (LMWH)
    2. Anti-embolism stocking
    3. Early ambulation
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15
Q

State the surgical principle of CRC

A

Complete mesocolic excision (CME)
- Dissection in the embryological defined mesocolic plane
- Central ligation of the vascular pedicle
- Resection of an adequate length of colon
- Bowel continuity restored with a well-vascularized, tension-free anastomosis

The selection of the appropriate surgical procedure depends on the location of the primary tumor

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16
Q

Describe on the management strategy of stage 4 colon CA (with liver metastases)

A
  • Sandwich therapy: Neoadjuvant chemotherapy, surgical resection followed by adjuvant chemotherapy
  • Inclusion of biological agents (such as BEVACIZUMAB or CETUXIMAB)

Surgical goals: adequate resection of all metastases with adequate liver reserve

17
Q

List the immediate complications of CRC intra-operatively

A
  • Intra-operative complication -> Bleeding, Injury to surrounding organs
  • Ureteric injuries (During (1) Take off of IMA (2) Pelvic brim (3) between the lateral ligament)
  • During APR, urethral injury can occur
18
Q

Define rectum + state its anatomy

A
  • Segment of large bowel within the true pelvis
  • Part of the large bowel at the 3rd sacral vertebrae represents the top of the rectum
  • Measures 12-15cm long
  • ANORECTAL JUNCTION is the reference point between anal canal and and the rectum
19
Q

State the anatomy of anal canal

A
  • Measures 2-4cm long and passes downwards and backwards
  • Surrounded by a complex arrangement of sphincter
  • DENTATE LINE divides the upper half and lower half of anal canal
20
Q

State the clinical presentation of rectum CA

A
  • PR bleed (hematochezia/melena)
  • Tenesmus
  • Diminished stool calibre - PENCIL-THIN STOOL
  • Mucoid stool (suggestive polypoid masses)
  • Change in the bowel habits
21
Q

What are the systemic complication of rectal CA based on the following headings:
- Constitutional symptoms
- Liver
- Lungs
- Bone
- Brain

A
  1. Constitutional symptoms - LOW, LOA
  2. Liver - RHC discomfort, jaundice
  3. Lungs - SOB (pleural effusion), decreased effort tolerance
  4. Bone - Bone pain, pathological fractures
  5. Brain - altered mental status
22
Q

How can we establish the diagnosis of rectal CA during investigation?

A

FLEXIBLE COLONOSCOPY
- Allow for direct visualization
- Allow for biopsy for histological diagnosis
- Allow for assessment of SYNCHRONOUS LESIONS
- Allow for therapeutic procedures (e.g POLYPECTOMY)

Other investigation tools:
1. Rigid sigmoidoscopy
2. CT colonography
3. Double-contrast enema

23
Q

Staging of rectal CA can be divided into local and systemic staging

State the investigations you would order to stage the CA

A

Local staging
- MRI rectum (Superior to EUS as can assess the circumferential resection margin)
- Endorectal US (Superior in delineating depth of tumor invasion and can assess local lymph node status)

Systemic staging
- CT TAP

Surgery (13 decks)

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