Pathology of Acute and Chronic Diarrhea Flashcards
What is stool osmotic gap? What is its utility?
Stool osmotic gap is a calculation performed to distinguish among different causes of diarrhea
An osmotic gap of >125 suggests an osmotic diarrhea while a gap of
What are the ways in which diarrhea is classified?
Secretory
Osmotic
Malabsorption
Exudative
Explain/discuss secretory diarrhea? Does it resolve with fasting?
results when there is either a problem with secretion of water/electrolytes or a problem with absorption of water/electrolytes
Does NOT subside with fasting
There is no significant stool osmotic gap
Explain/discuss osmotic diarrhea? Does it resolve with fasting?
Results from the presence of indigestible/poorly absorbed solutes in the bowel lumen (so water will stay in that area and will not be reabsorbed)
Does subside with fasting
Significant stool osmotic gap
Explain/discuss malabsorption diarrhea? Does it resolve with fasting?
Failure of nutrient absorption (body does not absorb things properly so water does not follow - think fatty stool)
Does subside with fasting
think CD, celiac disease, etc.
Explain/discuss exudative diarrhea? Does it resolve with fasting?
Due to inflammatory disease: inflammatory products cause increased stool volume and frequency BUT it alters absorption of fluid and electrolytes
Does NOT subside with fasting
What is pseudomembranous colitis?
Pseudomembranes are an adherent layer of inflammatory cells and debris at sites of colonic mucosal injury
Most commonly caused by C. difficile (scenario = antibiotics that disrupt the normal colonic microbiota and lead to overgrowth of C. diff)
How exactly do toxins released by C. difficile cause pseudomembranous colitis?
Toxins cause ribosylation of small GTPases and lead to disruption of the epithelial cytoskeleton, tight junction barrier loss, cytokine release and apoptosis
What’s the histological buzzword for pseudomembranous colitis?
“volcanic eruption”
Superficially damaged crypts are distended by mucopurulent exudate that forms an eruption reminiscent of a volcano –> exudate coalesce to form pseudomembranes
Ischemic colitis: mucosal infarction and mural (mucosa + submucosa) infarction can follow after…
acute or chronic hypoperfusion
Ischemic colitis: transmural infarction typically follows after…
acute vascular obstruction
*acute compromise of a large vessel can cause infarction of several meters of intestine
What areas of the colon are most at risk for infarction?
Watershed zones (intestinal segments at the end of their respective arterial supplies)
Most common are = splenic flexure
What is the most common cause of intestinal ischemia?
arterial insufficiency of the large and small bowel
What are microscopic colitidies? Are there findings on endoscopy?
a cause of chronic diarrhea that is divided into two entities (lymphocytic and collagenous) that presents with chronic, non-bloody, watery diarrhea
NO findings on endoscopy
How can lymphocytic colitis and collagenous colitis be differentiated from IBD?
First of all, has to be done microscopically
- lymphocytic colitis and collagenous colitis lack features of chronicity seen in IBD
- lymphocytic colitis and collagenous colitis have A LOT more lymphocytes
