Pathology of the Large Intestine Flashcards
What is diverticular disease?
Abnormal out-pouchings of a cavity, through its contents, at a weak point in the wall; holes/orifices can be seen
Often, it is asymptomatic but there can be colicky, lower abdominal pain; it does not predispose to malignancy
Cause of diverticular disease?
Related to a low fibre diet and increased intra-luminal pressure:
When faeces are less solid, they are hard to excrete, so the large bowel increases the force of contractions; this forces the mucosa through potential weak points in the wall
Treatment of diverticular disease?
Surgery if it is complicated
Compications of diverticular disease?
Inflammation (diverticulitis) - faecolith trapped in diverticulum causes ulceration and subsequent complications
Rupture - increased pressure at the neck can cause rupture
Bacterial infection can occur, leading to a pericolic abscess or disseminated peritonitis and sepsis
Fistula - (passageway between two epithelial surfaces) abscesses can rub against other structures to form a connection, e.g: to the bladder and vagina
Massive bleeding - rub against vessels
Describe ischaemia of the large bowel
Tends to occur in the elderly and these people tend to have other CVS disease, e.g: AF, embolus, atherosclerosis of mesenteric vessels, vasculitis, etc
Tend to be left-sided
On colonoscopy, it is segmental
Histopathology of ischaemic colitis?
Inflammation of the colon that occurs due to inadequate blood supply; histopathological features include:
Withering of crypts
Pink, smudgy lamina propria
Fewer chronic inflammatory cells
Complications of ischaemic colitis?
Massive haemorrhage
Rupture
Stricture formation
Appearance of ischaemic colitis?
Patchy, yellow membranous exudate on mucosal surface
Histopathology of ischaemic colitis?
Explosive fibrinopurulent exudate on the surface
Explosive lesions on mucosa
What is antibiotic-induced colitis?
AKA pseudomembranous colitis or C. difficile colitis
Overgrowth of C.difficile occurs due to suppression of normal bowel fora with broad-spectrum antibiotics; superficial loss of epithelial cells, which become embedded in an exudate of mucin, polymorphs and abundant fibrin, forming a pseudomembrane
Watery diarrhoea results but the endoscopy may be normal; a biopsy is needed
What is collagenous colitis?
IBD (unknown cause) that causes watery diarrhoea with a normal endoscopy; a biopsy is needed
Thickened basement membrane and the disease is patchy; it is assoc. with and increase in intra-epithelial inflammatory cells but there are no chronic architectural changes
Causes of collagenous colitis?
Sometimes, drugs are the cause
There should be watery diarrhoea and normal endoscopy in the Hx as well
What is lymphocytic colitis?
There are no chronic architectural changes in the crypts but the intraepithelial lymphocytes are increased; there is no thickening of the basement membrane
Watery diarrhoea with a normal endoscopy; raise the possibility of coeliac disease in the report
What is miscroscopic colitis?
Includes:
Collagenous colitis
Lymphocytic colitis
There is normal endoscopy and watery diarrhoea
In summary, what are the causes of microscopic colitis?
Collagenous colitis
Lymphocytic colitis
