Pathology of the Large Intestine Dr. Shaun Walsh Ninewells Hospital Dundee

Large bowel is affected in a vast array of diseases Large bowel pathology varies widely worldwide Large bowel pathology varies with age We have 50 minutes! Pathology of the Large Bowel

Common diseases only Western world diseases only Adult diseases mostly Focus on the visual aspects of these diseases Pathology of the Large Bowel Core content

Diverticular disease Ischaemia Antibiotic induced colitis Microscopic Colitis Radiation colitis Inflammatory bowel disease and colon cancer are separate lectures Pathology of the Large Bowel Common diseases

Endoscopic appearance Macroscopic (Gross) appearance Histopathologic appearances Discussion Diagnostic tests, treatments etc… will be covered elsewhere Pathology of the Large Bowel Lecture plan

Pathology of the Large Bowel Normal appearance

Pathology of the Large Bowel Patient Endoscopy 1 Arrows denote diverticular orifices

Pathology of the Large Bowel

On transverse slicing

Pathology of the Large Bowel Muscularis Serosa

Pathology of the Large Bowel

Diagnosis?

Common Often assymptomatic Related to low fibre diet and increased intralumenal pressure Symptoms only if complicated…surgery Diverticular disease of the Large Bowel

Complications - Inflammation -Rupture -Abscess -Fistula -Massive bleeding Diverticular disease of the Large Bowel

Pathology of the Large Bowel Patient Endoscopy 2

Withering of crypts and smudging of lamina propria

Diagnosis?

Elderly Left sided disease Aetiology - CVS disease- Atherosclerosis of mesenteric vessels - A.Fibrillation- Shock - Embolus- Vasculitis Ischaemia of the Large Bowel

Diagnosis: Ischaemic colitis Histopathological clues ‘withering of crypts’ ‘pink smudgy lamina propria’ ‘fewer chronic inflammatory cells’ Clinical context: Elderly people Left sided Segmental on endoscopy

Complications - Massive bleeding - Rupture - Stricture Pathology of the Large Bowel Ischaemic colitis

Pathology of the Large Bowel Patient Endoscopy 3

Pathology of the Large Bowel Patchy yellow membranous exudate on mucosal surface

Pathology of the Large Bowel Explosive fibrinopurulent exudate on surface

Explosive lesions on mucosa

Diagnosis?

Patients on broad spectrum antibiotics Clostridium Difficile selected out Toxin A and B attack endothelium and epithelium Massive diarrhoea and bleeding Treat with Flagyl/Vancomycin May need colectomy and may be fatal Antibiotic-induced “Pseudomembranous” colitis

Pathology of the Large Bowel Patient 4: Watery diarrhoea Normal Mucosa

Collagenous Colitis

Increase in thickness of subepithelial collagen

Collagenous Colitis Thickened basement membrane Normal is between 2-3 microns Disease is patchy Associated with intraepithelial inflammatory cells No chronic architectural changes Check clinical history for watery diarrhoea, normal endoscopy, drug history etc

Pathology of the Large Bowel Patient 5: Watery diarrhoea Normal Mucosa

Normal crypt architecture

Massive increase in intraepithelial lymphocytes

Lymphocytic Colitis No chronic architectural changes in crypts Intraepithelial lymphocytes are raised No thickening of BM Check for correct history, normal endoscopy Raise possibility of Coeliac disease in report

Microscopic colitis? A misnomer somewhat Normal endoscopy Useful for cases with mixed features of CC and LC Should use in appropriate clinical context Not Crohn’s or UC Be prepared to reclassify on subsequent biopsies

Pathology of Large Bowel Patient 6

Rectal biopsy: Pt with history of cervical carcinoma

Radiation Colitis Chronic active or inactive colitis Telangectasia Bizarre stromal cells, bizzarre vessels May be other complications of immunosuppression if also on chemotherapy Should only be reported with certainty in the clinical context

Pathology of Large Bowel Patient 7

Busy epithelium but no crypt irregularity

Florid diffuse acute cryptitis

Focal acute cryptitis in otherwise unremarkable colonic mucosa

Acute (infective) Colitis Infection Rarely Drugs, ischaemia, endoscopy prep. But not specific for infection as it may rarely herald the onset of IBD. Needs to be followed up closely.

Diverticular disease Ischaemia (Ischaemic colitis) Antibiotic induced colitis Microscopic colitis Radiation Colitis Infective Colitis (acute colitis) Ulcerative Colitis and Crohn’s disease Pathology of the Large Bowel Common diseases

Others CMV Mycophenylate Graft versus Host disease Etc…