Lower GI tract pathology Flashcards
which congenital GI condition is associated with Down’s syndrome (2%) ?
Hirschsprung’s disease
how does Hirschsprung’s disease present? aetiology?
Constipation, abdominal distension, vomiting, ‘overflow’ diarrhoea
Mostly Male
Aetiology;
Absence of ganglion cells in myenteric plexus - means neurological function of bowel is lost means perristalsis malfunctions
Distal colon fails to dilate - AXR: narrow bowel
RET proto-oncogene Cr10 + others
how do we diagnose and manage Hirschsprung’s disease ?
clinical impression
biopsy of affected segment.
hypertrophied nerve fibers but no ganglia.
Treatment: resection of affected (constricted) segment. (frozen section)
list some mechanical disorders of the GI tract?
1. Obstruction: Adhesions Herniation Extrinsic mass Volvulus
- Diverticular disease
what is a volvulus and what does it lead to?
complete twisting of a loop of bowel at mesenteric base, around vascular pedicle - A volvulus occurs when bowel twists on its own mesentery
intestinal obstruction +/- infarction
what are common sites of volvulus by age?
small bowel (infants)
sigmoid colon (elderly)
how would voluvulus present?
With clinical features of bowel obstruction;
As the sigmoid colon is located distally in the GI tract, vomiting is usually a late sign, whilst the colicky pain, abdominal distension, and absolute constipation occur earlier on in the clinical course.
Particularly noteworthy in cases of volvulus, compared to other causes of bowel obstruction, is the rapidity of onset (over a few hours) and degree of abdominal distension
what is the pathogenesis of diverticular disease?
is the formation of numerous tiny pockets, or diverticula, in the lining of the bowel - food etc. can get. stuck inside -> inflammatio, perforation* etc
VERY COMMON
Low fibre diet
High intraluminal pressure
‘Weak points’ in wall of bowel
90% occur in left colon
- can lead to diverticulitis
how does diverticular disease present?
often asymptomatic
Pain - If out-pouches become inflamed Diverticulitis Gross perforation Fistula (bowel, bladder, vagina) Obstruction
how would you investigate diverticular disease?
Barium enema
list causes of acute colitis
Infection (bacterial, viral, protozoal etc.)
Drug/toxin (esp.antibiotic)
Chemotherapy
Radiation
what is Pseudomembranous colitis?
Antibiotic associated colitis
aka C. diff colitis
Acute colitis with pseudomembrane formation
Caused by protein exotoxins of C.difficile
what findings on ivx might suggest a Pseudomembranous colitis ?
C. difficile toxin stool assay
gross: wet cornflakes on bowel
histology; crypts look. like inflammed
how can Pseudomembranous colitis be treated?
Metronidazole or Vancomycin
what is the Most common vascular disorder of the intestinal tract ? sites?
Ischaemic Colitis/ Infarction
commonly. occures at watershed areas - where vessels meet; splenic flexure (SMA and IMA*) and the rectosigmoid (IMA and internal iliac artery)
- inferior mesenteric artery
what are causes of ischaemic colitis?
Arterial Occlusion: atheroma, thrombosis, embolism
Venous Occlusion: thrombus, hypercoagulable states
Small Vessel Disease: DM, cholesterol emboli, vasculitis
Low Flow States: CCF, haemorrhage, shock
Obstruction: hernia, intussusception, volvulus, adhesions
how is ischaemic colitis treated ?
how does it kill?
resect area of bowel
kills because - ischaemic bowel can lead to infection
what are the features of chrons disease that help differentiate. it from other IBD?
Whole of GI tract can be affected (mouth to anus) - likes terminal ileum
‘Skip lesions’
Transmural inflammation
Non-caseating granulomas
Sinus/fistula formation
‘cobblestone mucosa’
Linear ulcers
Fissures
Extra-intestinal manifestations!
what are the extra-intestinal manifestations of Chrons?
Arthritis Uveitis Stomatitis/cheilitis Skin lesions - Pyoderma gangrenosum - Erythema multiforme - Erythema nodosum
which is more common UC or Chrons?
UC
what are the features of Ulcerative colitis - UC that help differentiate. it from other IBD?
Involves rectum and colon in contiguous fashion.
May see mild ‘backwash ileitis’ (involvement of ileum - small bowel) and appendiceal involvement but small bowel and proximal GI tract not affected.
contiguos spread
Inflammation confined to mucosa
Bowel wall normal thickness
Shallow ulcers
associated with Primary Sclerosing Cholangitis
which inflammatory bowel disease is associated with the following;
Severe haemorrhage
Toxic megacolon
Adenocarcinoma (20-30 x risk)
Ulcerative colitis - UC
lead pipe colon on xray. is seen. in UC or Chrons?
UC
String sign on xray. is seen. in UC or Chrons?
chrons
how do the complications of chrons and UC differ?
UC
Severe haemorrhage
Toxic megacolon
Adenocarcinoma (20-30 x risk)
Chrons;
obstruction
fistula
abscess
bloody diarrhoea is seen. in UC or Chrons?
UC
UC has similar extraintestinal manifestations as Chrons execpt for?
UC can invovle eyes and muscles;
Myositis
Uveitis/iritis
are the following polyps cancerous ;
Tubular adenoma
Tubulovillous adenoma
Villous adenoma
no are neolplastic, associated with iincreased risk of cancer ;
Adenomas are precursors of carcinoma
what is the difference between a hyperplastic polyp and an adenoma?
adenoma = excess epithelial proliferation AND dysplasia
what. factors increase risk of polyp being cancerous?
Size of polyp (> 4 cm approx 45% have invasive malignancy)
Proportion of villous component
Degree of dysplastic change within polyp
how might an adenoma present?
Usually none
Bleeding/anaemia
what are the details of Familial Adenomatous polyposis (FAP/APC) ?
prognosis?
Autosomal dominant - average onset is 25 years old
Adenomatous polyps, mostly colorectal
Minimum 100 polyps, average ~1,000 polyps
chromosome 5q21, APC tumour suppressor gene
virtually 100% will develop cancer within 10 to 15 years; 5% periampullary Ca
how is Familial Adenomatous polyposis (FAP/APC) treated?
prophylactic resection of colon to prevent cancer
what is Gardner’s Syndrome?
same as FAP but higher risk of cancer
Distinctive extra-intestinal manifestations eg cysts and tumours
what causes Hereditary Non-polyposis Colorectal Cancer (HNPCC)?
Uncommon autosomal dominant disease
3-5% of all colorectal cancers
1 of 4 DNA mismatch repair genes involved (mutated)
Numerous DNA replication errors (RER)
what is the progression and prognosis of Hereditary Non-polyposis Colorectal Cancer (HNPCC)?
Onset of colorectal cancer at an early age - 35 year olds
High frequency of carcinomas proximal to splenic flexure
Poorly differentiated and mucinous carcinoma more frequent
Multiple synchronous cancers:
Presence of extracolonic cancers (endometrium, prostate, breast, stomach)
most Colorectal carcinoma are of which type?
98% are adenocarcinoma
what Grading and Staging is used in Colorectal carcinoma?
Grade = level of differentiation
Dukes’ staging: A = confined to wall of bowel B = through wall of bowel C = lymph node metastases D = distant metastases
TNM (tumour, nodes, metastases)
what age is expected for diffirent colon cancers
normal one (non familial) - age 65 approx
FAP - 25
HNPCC - 35 / 40
