Lower GI Histopath Flashcards by Siddarth Kumar

What is Hirschsprung’s disease?

Absence of ganglion cells in myenteric plexus (80% males)

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Presentation of Hirschsprung’s (1)

Signs & symptoms of obstructions in babies (mostly males)

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Hirschsprung’s association (1), Genetics (1), biopsy (1), treatment (1)

Associated with Down’s

Genetics - RET proto-oncogene Cr10

Biopsy - hypertrophied nerve fibres, no ganglia

Treatment - resection of affected segment

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5 congenital lower GI diseases

Atresia

Stenosis

Duplication

Imperforate anus

Hirschsprung’s disease

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Mechanical causes of obstruction: (6)

Constipation

Diverticular disease

Adhesions

Hernia

Volvulus - complete twisting of bowel loop at mesenteric base around vascular pedicle (in infants its mostly sigmoid, in elderly its caecal)

Intussuception

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Causes of acute colitis (3)

Infection

chemo/radiotherapy

Drugs

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Causes of chronic colitis (2)

IBD TB

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Ischaemic colitis causes (3)

Arterial/ venous occlusion

small vessel disease

low flow state

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Where is it most common for ischaemic colitis to occur?

Watershed areas (weak points at the borders supplied by the IMA & SMA)- splenic flexure, rectosigmoid

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C. Diff - cause (1), exotoxin results in (1), Investigation (1), treatment (1)

Abx - kill off commensals exotoxin causes pseudomembranous colitis

Ix - stool culture

Rx- metronidiazole or vancomycin (2nd line)

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Diverticular disease - what is it (1), where does it occur mostly (1), symptoms (1),

High intraluminal pressure results in outpouchings in weak points of bowel wall (low fibre diet)

PR bleed sometimes (mostly asymp)

Occurs 90% of time in left colon

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Complications of diverticular disease (3)

Diverticulitis - fever & peritonism

Perforation fistula obstruction

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Epidemiology of IBD - age of onset, race,

Both peak age in 20’s White ppl > non-white

Crohn’s symptoms worsened by smoking

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MZ twin concordance IBD

UC - 15%

Crohn’s - 50% aetiologies unknown

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Pathophysiology of Crohn’s (6)

Distribution, lesion characeristics, inflammation

Whole GIT affected - most common in terminal ileum & caecum

Patchy distribution - SKIP lesions COBBLESTONE appearance - areas of healthy mucosa lie above diseased mucosa

1st lesion = APTHOUS ULCER; deep ROSETHORN ulcers (which can join to form serpentine ulcers)

NON-CASEATING GRANULOMAS seen TRANSMURAL inflammation

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Pathophysiology of UC (6)

Extends proximally from rectum

Continuous involvment of mucosa

Small bowel not affected

Superficial inflammation (confined to mucosa) - superficial ulcers Islands of regenerating mucosa bulge into lumen > pseudopolyps

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Clinical features of Crohn’s (3)

intermittent diarrhoea

pain

fever

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Clinical features of UC (3)

Diarrhoea - more BLOODY & mucus

Crampy abdo pain relieved by defecation

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Non-GI manifestations of IBD - eyes (1) skin (4), joints (4), Liver (3)

Stomatitis - due to malabsroption & fe def

Eyes - uveitis

skin - eryethema nodosum, pyoderma gangrenosum, erythema multiforme, clubbing

Joints - _asymmetrical migrating polyarthropath_y of large joints, sacroiliitis, myositis, ankylosing spondylitis

Liver - PSC (UC > CD), pericholangitis, steatosis

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Complications of CD (4)

Strictures - require resection

Fistulae

abscess formation

perforation

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Complications of UC (4)

severe haemorrhage

toxic megacolon ( damage to muscularis propria with disruption of neuromuscular function > colonic dilatation)

adenocarcinoma (20-30 times increased risk)

Investigations CD (3)

markers of inflammation e.g. ESR, CRP

Barium contrast

Endoscopy

Investigations UC (3)

rectal biopsy

colonoscopy

stool culture

Management of CD: mild, severe, additional therapies

Mild - prednisolone

Severe - IV hydrocortisone, metronidazole

Additional - Azathioprine, methotrexate, infliximab

Management of UC: mild (2), moderate (3), severe (3)

prednisolone + mesalazine moderate - pred, 5-ASA, steroid enema Severe: admit, NBM IV fluids, rectal steroids 5 ASA for remission

What is carcinoid syndrome?

Tumours of enterochromaffin cells, secrete serotonin (5-HT). (mostly bowel, but can be lung/ovaries/testis)

Carcinoid syndrome features (3)

Bronchoconstriction Diarrhoea Flusing

Carcinoid crisis features (5)

lifethreatening vasodilation Hypotension Tachycardia Bronchoconstriction Hyperglycaemia

Ix of carcinoid syndrome (1)

24 hour urine 5-HIAA (main metabolite of serotonin)

Rx of carcinoid (1)

Octreotide (SS analogue)

Colonic adenoma (neoplastic polyp), what is it? symptoms if any?

Benign dysplastic lesions (precursor to adenocarcinoma) mostly asymp, regular surveillance i**f over 3.4 cm** 45% malignant change

Classification of colonic adenomas (3)

Tubular Tubulovillous Villous

What does a villous adenoma cause?

**Hypoproteniaemic hypokalemia** (leak large amounts of protein & K+)

Risk factors for malginancy in colonic adenomas (3)

**Large size** - most imp rf **increased villous** component **degree of dysplasia**

Describe the progression of colonic adenoma to carcinoma

Normal colon \> **at risk mucosa** after ***'**_first hit' mutation_* in 1st copy of APC gene *(FAP pts born with this mutation*) from at risk \> **adenoma** after *_2nd hit mutation to remaining APC_* gene Adenoma \> **carcinoma** following *_activaftion o KRAS_*, *_LOF mutations of p53_*

What is hamartomatous polyp?

A benign focal malformation that represents a neoplasm in the tissue of its origin Juvenile polyps

How is Peutz-Jegher's syndrome inherited?

**Autosomal dominant - mutation of LKB1 gene** (suspected TS gene)

Presentation of Peutz-Jegher's syndrome? (3)

multiple polyps, mucocutaneous hyperpigmentation, freckles around mouth, palms & soles

What are pts with Peutz-Jegher's at risk of? (2)

intussusception malignancy

Epidemiology of colorectal cancer - age group, ethinicity, type, most common site of cancer

2nd most common cause of cancer related deaths in UK Age 60-79 commoner in western population 98% are adenocarcinoma 45% occur in rectum

Aetiology of Colorectal cancer (6)

**Obesity** **Diet** - low fibre, high fat **Chrnoic IBD** **Genetic** - *_HNPCC, FAP_* **NSAIDs are protective** (NSAIDs inhibit COX-2 which is overexpressed in 90% of cancers)

Clinical features of right sided bowel cancer (2)

**fe-def anaemia** **weight loss**

Clinical features of left sided bowel cancer (3)

**PR bleeding** **Crampy LLQ pain** **change in bowel habit**

Ix (4) of bowel cancer

protcoscopy colonoscopy barium enema CT/MRI CEA - only for monitoring progress of therapy

Dukes staging of colorectal cancer

A - **confined to mucosa** (5 yr survival \> 95%) B1 - extending into **muscularis propria no LNs** B2 - **transmural invasion no LNs** C1 - extenting to **muscularis propria + LNs** C2 - **transmural + LN** D - distant mets (5 yr survival

Management of Rectal/ low sigmoid cancer

If \< 1-2 cm above anal sphinc (lower third of rectum) abdomino-perineal resection If \> 1-2 cm above anal sphincter \> anterior resection Sigmoid cancer \> sigmoid colectomy

Management of other colon cancers: desecending colon & distal transverse Ascending colon & proximal transverse transverse colon

Left hemicolectomy if descending/ distal transverse Right hemicolectomy if ascending/ proximal transverse Extended right hemicolectomy if transverse colon radiotherapy post op to decrease recurrence chemotherapy if palliative - 5-FU

FAP mutations (2)

70% AD mutation in APC gene 30% AR mutation in DNA mismatch repair genes

Presentation (1) & management of FAP (1)

Present between 10-15 yrs **\> 100 adenomatous polyps** required for diagnosis, (usually see 1000s) At birth **hypertrophy of retinal pigment** epithelium ALL will get carcinoma if untreated by 30! so do **prophylactic colectomy**

Gardners

Like FAP with extra interstinal features e.g. osteomas & dental caries

HNPCC/ lynch syndrome mutations (1),

**AD mutations in DNA mismatch repair genes** Carcinomas usually in *right colon*, few polups but fast progression to malignancy (present \<50 yrs) Assc with other cancers - endometrial ovarian, small bowel. stomach

What other cancers is HNPCC associated with (5)

endometrial, ovarian, small bowel, transitional cell, & gastric carcinoma