8: Colon Cancer Flashcards
What is inflammatory bowel disease?
- Chronic condition resulting from inappropriate mucosal immune activation
- Chronic inflammatory conditions of the gut
Summarise how features differ between the types of IBD
- Crohn's ○ Any area of GI tract from mouth anus ○ Skip lesions ○ Inflammation is transmural ○ Smoking risk factor - Ulcerative colitis ○ Only involves colon ○ Starts in rectum ○ Continuous distribution ○ Inflammation limited to mucosa and submucosa ○ Smoking protective
What are the morphological features of Crohn disease?
- Gross ○ Skip lesion ○ Mucosal oedema ○ Serositis leading to adhesions and fibrosis ○ Deep fissures causing cobblestone appearance ○ Focal ulceration ○ Fistulas ○ Strictures - Micro ○ Transmural inflammation ○ Extensive lymphocyte infiltration ○ Non-caseating granulomas
What is the association of IBD with cigarette smoking?
- Protective factor for Ulcerative Colitis
○ Risk of developing UC is higher in non-smokers and former smokers- A risk factor in Crohn’s Disease
○ Smoking appears to lessen the response to medical therapy
○ Smoking also increases the severity of the disease
- A risk factor in Crohn’s Disease
Complications of Crohn’s disease
○ Fistulae: § Enterovesical § Enterocutaneous § Rectovaginal ○ Stricture formation § Bowel Obstruction ○ Perianal Abscess ○ GI malignancy: § 3% risk of colorectal cancer over 10yrs § Small bowel cancer is 30x more common.
Extraintestinal features of Crohn’s disease
○ Malabsorption – Causes growth delay in children.
○ Metabolic Bone Disease
○ Gallstones
○ Kidney Stones
What are the morphological features of ulcerative colitis?
- Macro ○ continuous superficial inflammation of colon ○ Hyperaemic tissue ○ Pseudopolyps ○ Superficial ulcers - Micro ○ Erosion of mucosa ○ Ulceration resembling flask shape ○ Exudate present on mucosal surface ○ Goblet cell hypoplasia ○ Crypt distortion which can lead to crypt abscesses
Complications of UC
○ Toxic Megacolon: § Perforation § Peritonitis § Septicaemia ○ Colorectal Carcinoma
Extraintestinal features of UC
○ Metabolic Bone Disease:
§ Osteoporosis
○ Poor Growth and Development
○ Primary Sclerosing Cholangitis
What puts IBD at higher risk for neoplasia
○ Repeated chronic inflammation
○ Ageing population
○ Immunosuppressive treatments
What are sigmoid diverticular
- Acquired pseudo-diverticular outpouchings of colonic mucosa and submucosa
- Not invested by all three layers of colonic wall
Pathogenesis of sigmoid diverticular
○ Unique structure of colonic muscularis propria
§ Where nerves, atrial vasa recta and connective tissue sheaths penetrate inner circular muscle coat foal discontinuities in muscle wall are created
§ In other sections of colon these gaps are reinforced by external longitudinal layer of muscularis propria
§ In colon gathered into three bands termed taeniae coli
○ Increased luminal pressure
§ Exaggerated peristaltic contractions
§ Spasmodic sequestration of bowel segments
§ Low fibre diets reduce stool bulk
Morphological features of sigmoid diverticular
- Gross
○ Small, flask like outpouchings
○ 0.5-1cm dimeter
○ Occur in regular distribution alongside taenia coli- Micro
○ Thin wall composed of flattened or atrophic mucosa, compressed submucosa and attenuated or absent muscularis propria - Obstruction of diverticular -> inflammatory changes -> diverticulitis
○ Segmental diverticular disease-associated colitis
○ Fibrotic thickening around colonic wall
○ Stricture formation
○ -> perforation
§ Pericolonic abscesses
§ Sinus tracts
§ Peritonitis
- Micro
What are the common causes of bacterial peritonitis
○ Primary § Translocation of bacteria across gut wall or mesenteric lymphatics § Haematogenous dissemination § Usually immunocompromised state ○ Secondary § Perforation § Trauma § Iatrogenic
Common organisms involved in bacterial peritonitis
○ E.coli ○ Streptococci ○ S.aureus ○ Enterococci ○ C.perfringes
What is spontaneous bacterial peritonitis and in which circumstances does it tend to arise?
- Acute bacterial infection of ascitic fluid
- Primary peritonitis
- Complication of any disease that produces ascites
○ Heart failure
○ Budd-Chiari syndrome
○ Children with nephrosis of SLE
Organisms involved in spontaneous bacterial peritonitis
- Gram negative ○ E.coli - 40% ○ K.pneumonia - 7% ○ Pseudomonas ○ Proteus - Gram positive ○ Streptococcus pneumonia - 15% ○ Other strep species ○ Staphylococcus species
Morphology of spontaneous bacterial peritonitis
- Gross
○ Dense collections of neutrophils and fibrinopurulent debris that coat the viscera and abdominal wall
○ Serous or slightly turbid fluid accumulates
○ Becomes suppurative as infection progresses
○ Subhepatic and subdiaphragmatic abscesses can form- Micro
○ Neutrophil infiltration
○ Superficial inflammation
- Micro
Vascular supply of the GI tract
- Foregut = coeliac trunk
○ Oesophagus to Ampulla of Vater- Midgut = superior mesenteric artery
○ Up to 2/3 of the way along transverse
colon - Hindgut = inferior mesenteric artery
○ Distal 1/3 transverse colon to rectum
- Midgut = superior mesenteric artery
Describe and illustrate the causes of bowel obstruction.
- Intraluminal ○ Gallstone ileus ○ Ingested foreign body ○ Faecal impaction - Mural ○ Tumours § Adenocarcinomas ○ Strictures ○ Intussusception ○ Meckel's diverticulum ○ Lymphoma - Extramural ○ Hernias § Protrusion of bowel through weakness/defect in abdominal wall ○ Adhesions § Fibrous ‘bridges’ between bowel segments, abdominal wall or operative sites ○ Peritoneal metastasis ○ Volvulus § Loop of bowel twists around its mesenteric point of attachment
