H - Lower GI Flashcards
6 General consequences of lower GI conditions
Change in bowel habits
Bleeding
Perforation
Fistula formation
Obstruction
Systemic illness
4 congenital disorders of lower GI
Atresia
Stenosis
Duplication
Agenesis
What is atresia
No communication between 2 bits of bowel
What is hirschprungs
Absence of ganglion cells in submucosal and myenteric plexus
Patterns of hirschprungs
Starts in rectum and extends proximally
RFs for hirschprungs
Male
Downs
What mutation is present to cause hirschprungs
RET proto oncogene
Tx of hirschprungs
Resection of affected segment with frozen section to identify any ganglion cells and where they end
PC of hirschprungs
Failure to pass meconium in first 24hrs
General causes of bowel obstruction
Adhesions
Hernias
Extrinsic mass
Volvulus
Where do infants vs elderly get volvulus
Infants = SB
Elderly = sigmoid colon
Pathogenesis of diverticular disease
Low fibre diet
High intraluminal pressure
Weak points of bowel
Diverticular formed
What makes a diverticular a true one vs pseudo
True has ALL bowel wall layers in them
Where are 90% of diverticular found
L colon esp sigmoid
Complications of diverticular disease
Pain
Diverticulitis
Gross perforation
Fistula - bowel / bladder / vagina
Obstruction
Broad causes of acute colitis
Infection
Drugs / toxins
Chemo / radio
Infections that cause acute colitis
Fungal - Candida
Viral - CMV
Bacteria - salmonella
Protozoa - entamoeba histolytica
Who gets CMV colitis
Imm supp
Causes of chronic colitis
Crohns
UC
TB
When do you get pseudomembranous colitis
After ABx Tx
What is pseudomembranous colitis
Pseudomembrane formation with acute colitis
Cause of pseudomembranous colitis
Protein exotoxins of c.diff
Histology of pseudomembranous colitis
Mushroom cloud appearance
Ix for pseudomembranous colitis
C.diff stool assay
Where do you get ischaemic colitis
Watershed zones - splenic flexures (SMA/IMA) or rectosigmoid (IMA/int iliac)
Patterns of ischaemic colitis
Mucosal
Mural
Transmural
5 causes of ischaemic colitis with examples
Arterial - atheroma, thrombosis
Venous - thrombus, hypercoagulation
Small vessel disease - emboli, vasculitis
Low flow states - CCF, haemorrhage, shock
Obstruction - hernia, intussusception, volvulus, adhesions
Risk of transmural ischaemic colitis
Perforation
What is idiopathic chronic IBD
Diagnosis of exclusion that isn’t Crohns or UC
Potential RFs for idiopathic chronic IBD
Genetics - HLA
Infection - measles, mycobacteria
Abnormal host immunity
Microbiome
RFs for Crohns
Western
Young adult
White
Jewish
Smoking
Features / patterns of IBD
Mouth to anus
Skip lesions
Non caseating granulomas
Transmural inflammation - fistulae, fissures, sinuses
Cobblestoned appearance
Extra intestinal features of Crohns
Arthritis
Uveitis
Stomatitis
Cheilitis
Skin lesions - erythema multiforme / nodosum
Which is the more common IBD
UC
RFs of UC
White
20-25
Patterns / features of UC
Rectum to colon in continuous fashion
Mucosal inflammation not Transmural
Complications of UC
Severe haemorrhage
Toxic mega colon
Adenocarcinoma
Extra intestinal complications of UC
PSC
Erythema nodosum, pyoderma gangrenosum
Uveitis / iritis
Myositis
Arthritis
Which IBDs get crypt abscesses
BOTH
7 Types of tumour of large bowel
Non neoplastic polyps
Neoplastic epithelial lesions - adenoma, adenocarcinoma, neuroendocrine
Mesenchymal - lipoma, leiomyoma
Lymphoma
Types of non neoplastic polyps
Hyperplastic
Sessile serrated
Pseudopolyps - inflammation
Hamartomatous - juvenile, Peutz Jeghers
Peutz Jeghers has hamartomatous polyps and what other feature
Pigment around lips
Which type of polyp may be a risk factor for cancer
Sessile serrated lesions
Types of neoplastic polyps
Tubular adenoma
Tubulovillous adenoma
Villus adenoma
Tubular vs villous adenoma shape
Tubular = can be pedunculated (stalk), round, flat surface
Villous = finger like projections, non flat surface
What colour do neoplastic polyps look and why
Dark - high nuclear:cytoplasmic ratio
RFs for cancer in individual polyps
Size
Proportion of villous component
Degree of dysplasia
When do adenomas come vs carcinoma
Adenomas come 10 years before carcinomas
Do adenomas affect the risk of carcinoma
YES - risk proportional to number of adenomas
Sx of adenomas
Often non - can bleed / anaemia Sx
3 familial syndromes of colorectal cancer
Peutz Jagher
FAP - familial adenomatous polyposis
HNPCC - Hereditary non polyposis colon cancer
Age peak of FAP
25
Inheritance of FAP
AD
Mutation of FAP
Chr 5q21
APC TSG
What % of FAP get cancer in 10 years
100%
Dx cut off for FAP
> 100 polyps but usually ~1000
What other type of cancer is associated with FAP
5% get duodenal periampullary cancer
What is Gardeners syndrome
FAP + extra intestinal Sx eg osteomas / Desmoid tumours
What is Turcot syndrome
FAP + brain tumours
What is HNPCC aka
Lynch syndrome
Inheritance of HNPCC
AD
What % of colorectal cancers is HNPCC
3-5%
Cause of HNPCC
1 of 4 DNA mismatch repair genes involved - resulting in numerous DNA replication errors
Features of the cancer you get in HNPCC
in caecum (opposite to normal)
Poorly differentiated
Mucinous carcinoma
Multiple synchronous cancers
Other extracolonic cancers associated with HNPCC
ENDOMETRIUM
Prostate
Breast
Stomach
What % of bowel carcinomas are adenocarcinomas
98
Peak age of carcinoma of bowel
60-79
RFs for carcinoma of bowel
Familial
Diet - low fibre, high fat
Lack of exercise
Obesity
Adenomas
IBD
Sx of bowel carcinoma
Change in bowel habit
Anaemia
PR bleed
Weight loss
What guide is used for grade / stage
TNM not dukes
TNM T stage 1 of bowel carcinoma
Submucosa only
TNM T stage 4 of bowel carcinoma
Into peritoneum
