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FRACS Matthews > Colorectal > Flashcards

Colorectal Flashcards

1
Q

What are the macroscopic and microscopic features of Crohn’s disease?

A

Macroscopic
Laparotomy
- stiff and thick walled segments of bowel
- fat wrapping
- fibrinous exudate, hyperaemia, adhesions
- mesenteric inflammation/lymphadenopathy
- complications (strictures, fistulas, sinuses, abscesses).
Colonoscopy
- aphthous ulcers
- cobblestones
- serpinginous linear ulcers
- inflammatory pseudo polyps

Microscopic
- deep non caseating granulomas
- focal ulceration
- transmural inflammation
- intra lymphatic granulomas
- granulomatous vasculitis

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2
Q

What is ulcerative colitis?

A

Type of inflammatory bowel disease charaterised by continuous inflammation of the colonic mucosa extending proximally from the rectum.

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3
Q

What is the cause and risk factors associated with UC?

A

Cause
- Not known but thought to be an interplay between environmental and genetic factors. Genetically susceptible individuals have a dysregulated immune response incited by unknown luminal antigens leading to colonic mucosal inflammation.

Risk factors
- Genetics - 10-20% have a first degree relatvie. Likely an aggregate mutations. Extra intestinal manifestations associated with HLA-B27, HLA-B8 and HLA-DR2
- NSAIDs
- Infective proctocolitis
- Smoking is protective

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4
Q

What are the microscopic features associated with UC?

A
  • Mucosal thickening with infiltration by inflammatory cells
  • Degree if neutrophilic infiltration
  • Mucosal ulceration (regeneration of this leads to pseudopoplyps)
  • Crypt abscesses - branching of crypts following regeneration
  • Goblet cell depletion
  • Epithelial dysplasia (metaplasia)
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5
Q

What are the extra intestinal manifestations associated with UC?

A

Musculoskeletal:
Peripheral - gets better with colectomy
Axial - ankylosing spondylitis and sacroileitis - stays the same despite colectomy

Eyes
Uveitis and scleritis
Episcleritis

Skin
Erythema nodosum
Pyoderma gangrenosum

Hepatic
Primary sclerosing cholangitis (risk of cholangiocarcinoma) (patients with PSC and UC are at a 5x increased risk of colonic cancer)

DVT

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6
Q

What histological features found on colonoscopy for UC warrant colonic resection?

A

Flat multifocal low grade dysplasia and high grade dysplasia after confirmation by a second pathologist and discussion in MDT.

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7
Q

What are the risks associated with CRC in UC patients?

A

Disease duration:
2% by 10 years
8% by 20 years
18% by 30 years
Disease extent and duration
PSC
Family history of CRC
Presence of dysplasia

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8
Q

When does surveillance of CRC start in patients with UC?

A

8 years after diagnosis OR straight away if PSC/family hx

Annual colonoscopy:
- Active disease
- PSC
- Family hx of CRC in 1st degree < 50 yo
- Colonic stricture
- Previous dysplasia

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9
Q

What technique is used for colonoscopy for UC?

A
  1. Chromoendoscopy and dye spraying (methylene blue to enhance mucosal irregularities)
  2. Targeted biopsies from visibly abnormal tissue and random biopsies every 5-10cm
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10
Q

What are the principles of stoma formation?

A

1) Within rectus
2) Patient to visualise and access
3) 5cm from all folds, creases, incisions, belt line, umbilicus, bony prominence (measure sitting and standing position)
4) Consider occupation and physical limitations

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11
Q

What are the complications associated with stomas?

A

Early
- Dehydration, skin irritation/ulceration/breakdown, stoma ischaemia, poor position, bowel obstruction, mucocutaneous separation, fistula

Late
- Stoma retraction, prolapse, stenosis
- Parastomal hernia, fistula, bleeding, skin irritation/ulceration, bowel obstruction, dehydration

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12
Q

What is mucocutaneous separation and possible causes?

A

Separation of the bowel from the surrounding dermis. This can lead to leakage and skin irritation and if circumferential, stomal stenosis as heals by secondary intention.

Causes -> inadequate or improper approximation, excessive tension, infection or poor wound healing

Management:
Minor -> observation with area filled with alginate/skin barrier powder
Complete -> Revision

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13
Q

What are the management options for stoma prolapse?

A

1) Incarceration/strangulation -> urgent revision

2) Minimal prolapse/asymptomatic -> converservative management wiyth cool compresses, osmotic agent (sugar) and manual reduction/application of binder

3) Significant and symptomatic
Local repair -> ileostomy (division at mucocutaneous junction with delivery and excision of redundant bowel)
Laparotomy -> relocation or consider colectomy and end ileostomy
Reverse stoma

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14
Q

What are the risk factors for a parastomal hernia?

A

Patient
- Age
- Obesity
- Poor wound healing (malnutrition, immunosuppression, post operative wound infection, radiotherapy)
- Raised IAP (COPD, cough)
- Weak abdominal musculature

Surgical
- Emergnecy surgery
- Large trephine
- Loop stoma
- Stoma through laparotomy incision
- Stoma lateral to rectus muscle

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15
Q

What is the classification of parastomal hernia?

A

1) Subcutaneous - hernia protrudes alongside bowel into subcutaneous fat
2) Interstitial - hernia protrudes into intermuscular plane
3) Peristomal - hernia is prolapsed and loops of bowel and/or omentum enters hernia space between layers of prolapsed bowel
4) Intrastomal - protrudes into plane between emerging and everted part of bowel

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16
Q

What are the indications for surgery for a parastomial hernia?

A

Acute - incarceration/strangulation or obstruction or perforation
Elective - Symptomatic with pain, bulge, obstructive symptoms affecting QoL

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17
Q

What are the options for repair of a parastomal hernia?

A

Revision/mesh repair
Relocation - high rate of recurrence and complications

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18
Q

What are the indications for stents in laignant large bowel obstruction?

A

Disease
- Metastatic - definitive palliative mgmt (short life expectancy or not operative candidates) OR bridge to neoadjuvant chemotherapy /surgery (convert emergency surgery into an elective operation)

Patient
- not fit for surgical resection
- pts wishes

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19
Q

What are the complications associated with colonic stents?

A

Early
- Bleeding
- Perforation
- Malpositioning
- Failure
- Pain/tenesmus

Late
- Migration
- Perforation
- Recurrent obstruction

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20
Q

What is the proposed mechanism for pseudo obstruction?

A

Exact mechanism is unclear but thought to be an impairment of the ANS with SNS > PNS -> inhibitory effect on colonic motility

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21
Q

What are the causes of acute pseudo obstruction?

A

Trauma
Infection (pneumonia sepsis)
Neurological disease (Parkinsons, stroke, alzheimers, MS)
Cardiac disease (MI, heart failure)
Orthopaedic, pelvic, obstetric and spine surgery
Medications (narcotics, anticholinergics, TCAs, CCBs, epidural)
Metabolic imbalances (hypokalaemia, Ca, Mg, hypoT4)

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22
Q

What are the management options for pseudoobstruction?

A

1) Supportive care and removal of precipitants
- providing no signs of complications
- Treat underlying reversible disease (sepsis)
- Discontinue inciting medications
- Correct electrolytes
- Bowel rest and IVF
- NGT if vomiting (rectal tube/enema if distal)
- Serial PE and AXR to assess colonic dilation

2) Medical
- Neostigmine (caecum >10-12cm and failed 48h of supportive care). Acts as a acetylcholinesterase inhibitor, using 2mg IV dose with cardiovascular monitoring. Median time to respond is 4 min and decompression acheived in 80%.
- Erythromycin - stimulates smooth msucle contraction

3) Endoscopic
- Gas aspirated from colon and rectal tube left in situ
- Percutanous caecostomy if endoscopic treatment fails

4) Surgical
- rarely required - reserved for those that fail medical or endoscopic mgmt OR have signs of peritonism/perforation
- Resection, ileostomy, and mucous fistula for ischaemia/perforation
- Loop colostomy for no perforation

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23
Q

What are the causes of large bowel obstruction?

A

Mechanical
- Carcinoma 90%
- Volvulus 5%v
- Diverticular disease 3%
- Inflammatory bowel disease
- Anastomotic stricture
- Intussusception
- External compression

Adynamic
- Colonic pseudoobstruction
- Colonic dysmotility

Congenital
- Hirschprung’s disease
- Imperforate anus

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24
Q

What is volvulus and where does this occur?

A

This is when a portion of the colon twists around a fixed point in its mesentery causing strangulation of mesenteric vasculature and a closed intestinal loop.

Common sites
- sigmoid colon 75%
- caecum 20%
- transverse colon 5%

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25
Q

What are the risk factors for sigmoid volvulus?

A
  • Elderly
  • Institutionalised
  • Redundant sigmoid colon with narrow mesenteric attachment
  • Pregnancy
  • Pelvic malignancy
  • Parkinsons disease
  • Megacolon
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26
Q

What is the pathophysiology of sigmoid volvulus?

A
  • Axial rotation around inferior mesenteric vessels between fixed DC and rectum
  • Counter clockwise direction more common
  • Leads to closed loop obstruction (increased distension, impaired venous return, oedema, thrombosis, ischaemia) with compression/occlusion of mesenteric vessels.
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27
Q

What are the risk factors for caecal volvulus?

A

Main:
Failure of fusion of ascending colon mesentery to retroperitoneum with mobile ileo-caecum

Other:
Adhesions
Pregnancy
Malignancy
Colonic atony
Colonoscopy
Hirchspungs disease
Caecal distension

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28
Q

What are the types of caecal volvulus?

A

Type 1 - clockwise axial torsion along long axis with caecum remaining in RLQ

Type 2 - counterclockwise loop caecal volvulus from torsion of caecum and TI -> caecum in LUQ in an inverted orientation

Type 3 - Upward folding from inferior to superior caecum (CAECAL BASCULE)

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29
Q

What are the management principles of caecal volvulus?

A

Dont attempt endoscopic decompression as rarely succesful

Laparotomy - avoid detorsion if ischaemic as prevents reperfusion injury. Right hemicolectomy required if iscahemic.

Prevention of recurrence
- resection
- caecostomy tube (high rates of complications such as fistula, faecal peritonitis, wound infection

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30
Q

What is the genetic basis for Lynch syndrome?

A

AD germline mutation in one of the DNA mismatch repair genes including MLH1 and MSH2 (30-40% risk of CRC) and MSH6 (10-20%) and PMS2 (15-20%) .

MMR role is to correct errors in base pair matching during replication and to initiate apoptosis when damage beyond repair. With defective MMR, there is an accumulation of mutations in other genes.

Defective MMR -> microsatellite instability (microsatellites are tandem repeats of short sequences).

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31
Q

What are the clinical features of lynch syndrome?

A

Lymphocytic
Associated with endometrial ca (33%), ovary (9%), stomach (6%), urothelium and small bowel (<3%)
Mucinous & metachronous
Poorly differentiated and proximal
Signet cell and synchronous

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32
Q

What are the different modes of diagnosis for lynch syndrome?

A

1) Amsterdam criteria
- Aimed at identifying families at risk of Lynch and for consideration of genetic testing -> 50% of families fulfilling the criteria will have MMR mutation
- 3 relatives (one a 1st degree relative of the other2) affected by lynch associated cancer over **2 **generations with 1 < 50 years (FAP must be excluded)

2) Analysis of tumour tissue
- Microsatellite instability - panel of 5 microsatellite markers used to detect MSI (2 markers show instability, 1 marker is low, MS stable no markers)
- 15% of all CRC is MSI-H and only 5-10% due to HNPCC
- Bethesda criteria used to determine whether tumour tissue should be tested.

  • Immunohistochemistry - use of antibodies to measure expression of MMR proteins in tumour tissue (can be first line test with MSI reserved for patients with family hx suugestive but IHC normal).

3) Genetic testing
- Patient with tumour testing indicative of MMR mutation
- Youngest affected family member in family fulfilling Amsterdam criteria
- BRAF V600E testing required as in sporadic mutations, MLH1 can be silenced by somatic methylation, loss of expression of MLH1 and PMS2 on IHC (typically older females without fam hx)

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33
Q

What are the management options for a patient with lynch syndrome?

A

1) Surveillance
- Annual colonoscopy from 25yo or 5 years earlier than youngest diagnosis < 30 yo
- Fulfilling Amsterdam criteria with mutation status unknown - 1-2 yearly colonoscopy
- Referral to gynaecologist in woman consdiered for TAH + BSO after childbearing complete or by 40 yo.
- 2 yearly gastroscopies from 30 yo
- Urine cytology from 30 yo

2) Operative
- Colectomy not recommended but considered if >1 advanced adenoma
- Cancer -> oncological resection + surveillance o fremaining bowel (extended resection based on metachronous cancer v function)
- Colon cancer -> total colectomy with ileorectal anastamosis
- Rectal cancer -> total proctocolectomy + IPAA (reduces risk of metachronous cancer but more functional problems).

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34
Q

What is Turcot syndrome?

A

AR variant of Lynch syndrome
- 2 mutated alleles in the same MMR gene
- Associated with CNS tumours (glioblastoma multiforme or medulloblastoma)

35
Q

What is Muir-Torre Syndrome?

A

Lynch syndrome + sebaceous tumours, cutaneous keratoacanthomas, visceral carcinomas.

36
Q

What are the extraintestinal manifestations of FAP?

A

**Ectoderm **
- Epidermal cyst
- Tumours of CNS
- Congenital hypertrophy of the retinal pigment epithelium (CHRPE)

**Mesoderm **
- Desmoid tumours (excessive adhesions)
- Osteomas
- Dental abnormalities

Endoderm
- Adenomas, carcinomas of duodenum, stomach, SB, liver, biliary tree, thyroid and adrenal cortex
- Fundic gland polyps
- Hepatoblastoma

37
Q

What is the genetic basis behind FAP?

A

Germline mutation APC gene (AD transmission)
- APC spans 15 exons on chromosome 5q
- Mutations can occur throughout the gene but are particularly poor phenotype** codon 1309** AND attenuated disease with mutations at either end.
- Most produce an abnormal stop codon (shortened gene product)
- 30% have no family hx with de novo germline mutation or mosaicism
- **Loss of beta cateninn regulation **-> beta catenin accumulation -> activation of transcription factor Tcf-4 -> activation of Wnt (wingless type) -> cell division and overgrowth

38
Q

What is the implication of genetic testing of affected family members of patients with FAP?

A

At risk family members can be offered testing
- Non carriers have the same risk as general population
- Carriers require intensive screening
- Children are offered genetic testing early to mid teens

39
Q

What is the role of surveillance in patients with FAP?

A

Colonic
- Annual flexi sig or colonoscopy until polpys detected from age 10-15 or earlier if GI symptoms or from 18yo in AFAP
-> once polyp detected, requires annual colonoscopy until colectomy performed. Once colectomy performed, annual surveillance of residual rectum or ileal pouch

Duodenum
- upper GI endoscopy from 25 yo with frequency and management dependent on Spigelman criteria

40
Q

What are the management options in FAP?

A

**Operative **

Decision is based on once adenomas seen, age 15-25 yo

Type of surgery and timing, takes into account the severity of polyposis in rectum, risk of desmoid tumours and preservation of function (bowel and sexual)

1) Total colectomy + ileorectal anastamosis
2) Restorative proctocolectomy with pouch formation
3) Total proctocolectomy and end ileostomy (very low rectal cancer)

Risk of rectal cancer is higher in patients with numerous rectal polyps, mutations in codon 1309, over age of 25-30. Proctocolectomy preferable if risk of rectal cancer.

**Duodenal polyposis **
Spigelmann staging
- Number of polyps, polyp size, histological type, and degree of dysplasia
- Stage 0 - 5 yearly
- STage 1 - 3-5 yearly
- Stage 2 - 2-3 yearly
- Stage 3 - 6-12 monthly
- Stage 4 - consider duodenectomy (progression to cancer 35% over 10 years -> poor prognosis once invasive disease present)

41
Q

What is a desmoid tumour?

A

Fibromatous tumour resulting from clonal prolfieration of myofibroblasts

42
Q

Where do demoid tumours arise?

A

Most arise intra abdominally (SB mesnetery) or on the abdominal wall
Also can occur in extremeties or trunk

43
Q

What are the management options for desmoid tumours?

A

1) Medical
- Anectodal evidence for NSAIDS and anti-oestrogen

2) Surgical
- First line for body wall desmoids (recurrence rates are high)
- Avoided for intra abdominal desmoids due to high morbidity and mortality as well as recurrence

3) Cytotoxic chemotherapy

44
Q

What are the clinical features of MUTYH-associated polyposis (MAP)?

A

Similar phenotype to FAP but does not involve APC

1) Large number of colonic polyps
- 50% phenotype consistent with classical FAP
- 50% attenuated phenitype with < 100 polyps
- 100% life time risk of CRC age 60 (greater proportion of right sided tumours)

2) Gastric fundic gland polyps and duodenal adenomas (less common than FAP ~ 20-30%)

3) Extra-colonic manifestations uncommon (possible association with breast ca)

45
Q

Describe the genetic basis for MAP?

A

Autosomal recessive
Biallelic germline mutation in MUTYH gene
*Base excision repair gene *responsible for repair of oxidative damage to DNA
May act by increasing frequency of somatic APC mutations

46
Q

When is genetic testing considered in patients with MAP?

A

FAP phenotype but no detectable APC mutation

Indications:
1) Cumulative count of > 20 colorectal adenomas at any age
2) Siblings of MUTYH biallelic mutation carrier
3) > 10 adenomas and any of the following
- < 50 yo
- Synchronous colorectal ca
- Both adenomatous and serrated polyps (Adenomatous > serrated polyps)
- Family hx suggestive of recessive inheritance

47
Q

What is the definition of serrated polyposis syndrome?

A

1) >20 serrated polyps of any size distributed throughout colon

2) >5 serrated polyps proximal to sigmoid with > 2 being > 10mm

3) Any number of serrated polyps proximal to the sigmoid with first degree relative with serrated polyposis

48
Q

What are the management options for a patient suspected of having SPPS?

A

1) Surveillance
- Colonoscopy every 1-3 years with removal of all polyps > 5mm then colonoscopy every 1-3 years depending on the number, size and degree of dysplasia

2) Operation
- not recommended unless number and size of polyps make it impossible to remove all polyps > 5mm (colectomy and IRA)

3) Low dose aspirin

4) Family members
- 5 yearly colonoscopy from 40 yo or 10 years younger than youngest age of diagnosis

49
Q

What is peutz-jeghers syndrome?

A

Autosomal dominant condition characterised by multiple GI hamartomatous polyps and mucocutaneous pigmentation, from a mutation in STK11 in > 90%.
Polyps are characterised by smooth muscle in the submucosa with a branching tree appearance

50
Q

What are the associated conditions with peutz-jeghers syndrome?

A

CRC 40%
Gastric cancer 30%
Small bowel 10%
Pancreatic cancer 10-25%
Breast 55%
Ovaries 20%
Cervix 10%
Sertoli cell testibular ca 10%

51
Q

What is the management of peutz-jeghers syndrome?

A

1) Genetic testing

2) Surveillance (starts age 8)
- colonoscopy and gastroduodenoscopy age 8 yo and 3 yearly from 18yo if no polyps found age 8
- annual haemoglobin
- baseline video capsule endoscopy every 3 years

3) Polypectomy
- Gastric and colonic polyps removed at time of endoscopy
- SB polyps -> large, accompanied by anaemia, symptoms of intermittent SBO (can be removed with double balloon enteroscopy OR laparotomy with on table enteroscopy

4) Breast
- consider bilateral mastectomy OR annual MRI breast from 30 yo

5) Gynae
- Gynae for pelvic examination and cervical smear annual from 18yo

6) Testicular
- annual clinical examination from birth to teenage years looking for gynaecomastia and other signs of feminism, bilateral testicular enlargement

52
Q

What are the differentials for an appendiceal tumour?

A

Epithelial
- Mucinous (HAMN, LAMN, mucinous cystadenoca) (10-15%)
- Intestinal type adenocarcinoma (20%)
- Goblet cell carcinomas
- Signet ring cell tumours

Non epithelial
- Neuroendocrine (50%)
- Sacroma, leiomyoma, neuroma, lipoma
- Lymphoma

53
Q

When is staging indicated for appendiceal NET?

A
  1. Tumour > 2cm
  2. Evidence of intraabdominal / metastatic disease
  3. Symptoms of carcinoid syndrome
54
Q

What investigations would be requested in patients requiring staging in appendiceal NET?

A

Biochemistry
- 24h urine 5 HIAA (liver metastases or carcinoid syndrome)
- Serum chromogranin A (more sensitive, less specific)

Imaging
- Ct scan of liver
- DOTATE PET - mets outside of liver

55
Q

How is appendiceal NET managed?

A

1) Colonoscopy to exclude synchronous tumour (10-30%)
2) Tumours > 2cm right hemicolectomy (smaller tumours debated)
3) Right colectomy indicated for:
- Tumours > 2cm
- Tumours 1-2cm with mesoappendiceal invasion, LN mets, positive margins, high grade/LVI/mixed histology (goblet cell/adenca)

56
Q

What is the follow up for appendiceal NET following resection?

A

1) Appendicectomy (none)

2) Right hemicolectomy
- Clinical review and tumour markers at 3 months (5-HIAA and CgA)
- CT scan and tumour markers at 6 months
- Annual imaging and tumour markers thereafter

57
Q

What are the histopathological features of mucinous appendiceal neoplasm?

A

Simple mucocoeles - no dysplasia, increased intraluminal pressure -> mucin pools

Serrated polyps - serrated mucosa with or without dysplasia (KRAS mutated but lack BRAF mutation that characeterise colonic sessile serrated adenomas)

LAMN - dysplastic epithelium, producing mucin, with expansile growth with pushing border (loss of muscular wall and mural fibrosis). Confined to muscularis propira. (but mucin can dissect through wall)

HAMN - similar to LAMN but higher grade of dysplasia

58
Q

What is the difference in staging between LAMN and HAMN?

A

LAMN is confined to the appendiceal wall without invasion or loss of muscularis propria (Tis - LAMN). (T1/2 not used for LAMN, if acellular mucin or mucinous epithelium in subserosa or serosa T3/T4)

HAMN and invasive Ca
T1 - submucosa
T2 - muscularis propria
T3 - subserosa/meosappendix
T4a - visceral perironeum (acellular mucin or mucinous epithelium in serosa)
T4b - adheres to adjacent organs/structures

59
Q

What are the indications for a right colectomy for a mucinous appendiceal neoplasm?

A

1) Complicated mucocoele with involvement of terminal ileum or caecum
2) Base of appendix lesion and unable to get adequate margin

Note - right colectomy not performed solely for LN yield as mucnious neoplasm rarely involves LNs.

60
Q

What tumour markers would be requested for mucinous appendiceal neoplasm?

A

CEA, Ca19-9, Ca125

61
Q

What further management is required of a mucinous appendiceal neoplasm based on pathology?

A

Simple mucoceles or serrated polyps:
- No further management

LAMN/HAMN:
- Completely resected -> no further treatment
- T4a -> increased risk of PMP with increased recurrence (no increased benefit of right colectomy v appendicectomy alone) -> surveillance with imaging and tumour markers 6-12 months -> PMP detected -> CRS + HIPEC

Mucinous cystadenoca:
- unruptured, confined to the wall and completely resected -> consider completion R colectomy to allow LN staging (though rates of LN involvement is low)
- T4a -> CRS + HIPEC or surveillance with imaging and tumour markers every 6-12 months

62
Q

What is pseudomyxoma peritonei?

A

Clinical syndrome characterised by diffuse mucionus peritoneal involvement, often in association with a mucinous appendiceal lesion that has presumably ruptured.

WHO has divided this into the following categories

1) Acellular mucin - mucin within the peritoneal cavity without neoplastic epithelial cells
2) Low grade mucin (DPAM) - mucin pools with low cellularity, bland cytology and non stratefied cuboidal epithelium
3) High grade mucin (PMCA) - mucin pools with high cellularity, moderate/severe cytological atypia, numerous mitoses, and cribriform growth pattern. Destructive infiltrative invasion of surrounding organs often present.
4) High grade mucinous carcinoma peritonei with signet ring cells

63
Q

What is the pathophysiology of pseudomyxoma peritonei?

A

Originates as a mucinous cystadenoma of the appendix that occludes the lumen -> produce mucin -> increased pressure and then appendiceal rupture -> peritoneum seeded with mucous producing cells -> intestinal obstruction (fatal)

Common location to have PMP is the right paracolic gutter, right hemidiaphragm, greater and lesser omentum, and in pelvis (gravity) as rectovesical pouch or pouch of douglas.
Also adhere to braded surfaces following surgery.

64
Q

What are the CT features of PMP?

A

1) Mucous is similar density to water
2) Tumour deposition is peripherally located (bowel and mesentery spared, displaced centrally)
3) Omental caking
4) Scalloping of liver, sleep, mesentery
5) Calcifications are common

65
Q

What are the management options of PMP?

A

1) Repeated surgical debulking
- aim to remove gross disease to limit build up of mucous and its pressure effects
- not curative but does reduce symptoms and increase survival

2) Peritonectomy (aggresive cytoreduction)
Patient selection
- histopath - LAMN more likely to gain benefit than HAMN / invasive malignancy
- pre op CT - segmental SBO or tumour nodules >5cm on small bowel or adjacent to mesentery in jejunum or small bowel
- PCI score - quantitative indicator of prognosis based on size and destribution of peritoneal disease (likelihood of completing CRS and correlates with survival)

3) Heated intra peritoneal chemotherapy (HiPEC)
- Mitomycin C given intra op followed by 4-5 days of intraperitoneal 5-FU
- Has 7 x increase in drug conc in abdo cavity
- Chemo enters cells by simple diffusion
- 41 degrees heat -> increases tissue penetration and cytotoxicity

66
Q

What is the pathophysiology of diverticular disease?

A

Thought to be 2 main causal mechnisms:
1) Altered collagen structure in the colonic wall (decreased tensile strength)
2) Abnormal colonic motility with increased segmentation (seperate lumen into chambers)

Diverticulae result from increased intraluminal pressure that causes mucosa to protrude through natural weak points in the colonic wall where vasa recta penetrate muscularis propria.

Sigmoid colon is most commonly affected because the NARROW luminal diameter -> high intraluminal pressure -> La Place’s law (pressure required to distend wall is inversely proportional to radius).

Segmentation and low fibre diet intake -> reduced stool bulk requires higher pressure to pass

67
Q

What is the pathophysiology of diverticulitis?

A

Arises from perforation of a diverticulum with wall erosion from increased pressure or inspissated food particles -> inflammation and focal necrosis -> extravasation of faeces and bacteria -> extraluminal pericolic inflammation

67
Q

What are the associated complications of diverticulitis?

A

1) Abscess (conservative <2cm, trial ABs 2-5cm, >5cm drainage)
2) Generalised peritonisitis - pus or free perforation -> Hartmanns procedure (control contamination (irrigation and drainage), resect with sigmoid colectomy, and restoration (later date)
3) Fistula - bladder (pneumaturia/faecaluria, recurrent UTIs), vagina, small bowel, skin. Needs colonoscopy to confirm from diverticulitis. Trial of non operative management with ABx +/- IDC (50% will close)
4) Obstruction - acutely from a secondary phlegmon or abscess needing NG decompression or chronic secondary to stricture

67
Q

What is melanosis coli and its pathophysiology?

A

Colonic pigmentation associated with chronic laxative use, associated with Senna, Bisacodyl.

These laxatives pass into the colon unaborbed and are converted to their active form -> inhibit mucosa cell function -> apoptosis -> macrophages ingest these epithelial cells -> deposition of lipfuscin in lamina propria -> pigmentation

*lipofuscin is fine yellow-brown pigment granules composed of lipid-containing residues of lysosomal digestion.

Mgmt
- benign condition requiring stopping of laxatives if not required and no specific treatment needed

68
Q

What are the risk factors associated with CRC?

A

Non modifiable
- Age
- Male
- Positive family history
- Personal history (previous adenoma/CRC or long standing IBD)

Modifiable
- Obesity
- Smoking
- Diet high in fat and red/processed meat
- Low fibre diet

69
Q

How can CRC be classified?

A

1) Sporadic CRC (70%) - related to dietary and environmental factors
2) Familial CRC (25%) - family history of CRC but not an inherited syndrome
3) Inherited CRC (5%) - most common being FAP and HNPCC

70
Q

What are the 3 main molecular pathways leading to CRC?

A

1) Chromosomal instability pathway
- Both inherited and sporadic, earliest mutation is APC, with subsequent mutations KRAS, DCC, p53

2) Microsatellite instability pathway
- Both inherited and sporadic, with adenomatous polyps and serrated adenomas to invasive ca. Result of accummulation of errors in DNA as a result of mutation in MMR genes (spell checker).
- Sporadic from hypermethylation (rather than specific mutation) affecting MMR expression (MLH1) with transciptional silencing of gene expression
- Inherited with Lynch - Only KRAS, not BRAF mutations

3) CpG island methylator phenotype pathway
- From serrated polyps as a result of epigenetic alterations and DNA hypermethylation (silencing of MMR genes), CpG islands -> hypermethylation of MMR genes like MLH1 -> silenced
- High incidence of BRAF mutation V600E, do not carry mutations in KRAS

71
Q

What are the main prognostic factors for colon cancer?

A

**TNM **
- N - look at number of nodes examined (>12) and apical node involvement, if stage 2 and <12, consider adjuvant chemo, extranodal extensionas well as micromets (>0.2mm) = poor prognosis
- Extramural non nodal tumor deposits - strongly linked to extramural venous invasion

Extent
- size, CRM, TRS, and location (L>R)

**Histology **
- Signet ring cell (worse prognosis)
- Medullary type (better prognosis)
- Mucinous adenoca (poor responsiveness to neoadj, secrete mucin, right sided)
- Adenosquamous - poor prognosis
- Neuroendocrine diff (well diff = good prognosis, poorly diff = poor prognosis)

Differentiation / grade
- Well diff/low grade
- Moderately diff
- Poorly diff

LVI/PNI = poorprognosis

Immunohistochemostry
- MMR or MSI-H defects - loss of staining of IHC for MLH1, MSH2, PMS2, MSH6 - better prognosis but adj FU based chemo less beneficial (PD-1 inhibitors in advanced disease)
- KRAS mutations - worse prognosis as predicts lack of efficiacy of EGFR agents
- BRAF - used in MMR defective tumours with loss of MLH1 - predict resistance to -antiEGFR treatment

**CEA level **

72
Q

What is the typical distribution of colonic cancer?

A

Rectum - 40%
DC/sigmoid - 25%
Caecum AC - 20%
TC - 10%
Splenic flexure 5%

73
Q

What are the indications for adjuvant chemotherapy for colonic cancer?

A

All node positive patients and some high risk stage II (T3/4 N0)
- Poorly differentiated histology
- LVI/PNI invasion
- Bowel obstruction/perforation
- T4 tumour
- Fewer than 12 LNs examined
- MMR status, comorbidities, life expectancy, risks of rx

74
Q

What is intestinal failure and what are the main causes?

A

This is a spectrum of conditions that results in an in ability to maintain adequate nutritional, fluid, and electrolyte homestasis without supportive therapy.

The main causes include:
1) Loss of intestinal length
- SB resection (crohns disease), vascular catastrophe, volvulus, trauma

2) Loss of functional intestinal length
- fistuous disease, external or internal, in crohns or break down of anastamosis, CRC, UC, TB, Actinomycosis

3) Loss of intestinal absorptive ability
- IBD, scleroderma, amyloid, coeliac disease, radiation enteritis

4) Loss of intestinal function
- post operative ileus

75
Q

What is the length of small bowel remaining that is concerning for intestinal failure?

A

Less than 100cm in presence of ileostomy
Less than 50cm with large bowel still present

76
Q

What is the pathophysiology of intestinal failure?

A

There is the initiating event and then subsequent recovery with 3 stages.

1) Hypersecretory phase - of the 7L produced by the stomach, duodenum, small intestine, pancreas, liver, 6L is reabsorbed proximal to the IC valve, a further 800ml reabsorbed in the colon, and 200ml left in the faeces

2) Adaptation phase - histological changes to the intestinal mucosa that lead permit mucosal absorption. Takes 3-12 months. Ability to adapt is dependent on age (children better), the site (ileum better), underlying disease extent.

3) Stabilisation phase - can take up to 1-2 years with the extent and route varying. Goal is to acheive stability at home.

77
Q

What are the effects on electrolytes with a enterocutaneous fistula proximal to the ileum?

A

Hyponatraemia - most Na+ is absorbed in the ileum and the colon
Hypokalaemia - most K+ is absorbed in the small bowel, so less than 60cm can result in this.
Hypomagnesia - usually absorbed in the distal jejunum and iluem - loss of this can result in calcium deficiency through impariment of PTH release.

78
Q

Where is most of the carbohydrates, proteins and water soluble vitamins absorbed?

A

Upper 200cm of the jejunum

79
Q

What is the effect of loss of bowel on fat, bile salts and fat soluble vitamins?

A

Fat and Vit D E K A are absorbed along the length of the small bowel
Bile salts are absorbed in the ileum and thus a deficiency will result in reduced fat absorption as well as associated vitamins

Vit D with Ca2+ are given empirically.
Frequent monitoring of Vit E and A levels with an awareness of visual and neurological symptoms
If completely dependent on PN, then Vit K injection required

80
Q

What are the principles of management for intestinal failure or enterocutaneous fistula?

A

SNAPP

**Sepsis **
- Antibiotics and drainage of sepsis (ideally non operatively as further drainage results in a high risk of further bowel damage)

**Nutrition **
- Replacement of fluid, electrolytes, and nutrition is vital (carbs, fats, protein and vitamins)
- Involves serum electrolyte measurements and regular weight measurements
- Enteral feeding commenced as soon as possible with PN as support
- Males - 25-30 kcal/kg/day
- Females - 20-25 kcal/kg/day
- Reduction of output -> restrict fluid intake (500ml/day) with electrolyte solutionPPIs, codeine and loperamide.
- Diet - seperate solids from liquids, grazing small amounts
- Parental nutrition - can be at home but need the right conditions
- Refeeding device

Anatomy
- planning the anatomy helps with planning long term outcomes. This helps determine how much small bowel remains and give an indication of the likelihood of permanent PN. Also looks at the anatomy of the ECF. Use of contrast in fistula, enema, or oral may help with this.

Protection of skin
- small bowel output is caustic with excoriation of skin around stoma or fistula

**Planned surgery **
Delay surgery for 6-12 months to reduce mortality and fistula recurrence rates
However, sometimes surgery is fored such as excision of ischaemic bowel, laying open abscess cavities, construction of controlled proximal stoma (high output enterovaginal fistula)
Conditions of no dehydration/sepsis, good nutrition, and a well patient.

81
Q

What is the pathophysiology of LARS?

A

Combination of the following:

1) Colonic dysmotility
- denervation of remnant sigmoid / left colon during ligation of vascualr pedicle with increased colonic motility -> shorter colonic transit time
- Removal of rectum-> loss of negative feedback to oppose increased proximal colonic motilities -> further exacerbation of LARS symptoms

2) Neorectal reservoir dysfunction
- Denervation being hyposensitive to mechanical stimuli
- Reduced functional capacity with smaller volume of faeces inducing contraction and spasm

3) Anal sphincter dysfunction
- injury during ULAR can contribute to incontinence and urgency

FRACS Matthews (10 decks)

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