Pathology of Lower GI Tract Flashcards
1
Q
Celiac disease (“Gluten-Sensitive Enteropathy”) pathogenesis
A
- Gluten (wheat, barley, rye) digested by luminal and brush-border enzymes ==> α-gliadin peptide complexes with tissue transglutaminase (tTG)
- cross-linked molecules ==> autoantibody formation
- → inflammation ( ↑ T-lymphocytes) → villous atrophy → tissue damage → loss of mucosal and brush-border surface area → malabsorption, diarrhea
2
Q
Common associations/genetics of Celiac Disease
A
- Genetic associations: Class II HLA-DQ2 or HLA-DQ8 allele
- Association with other autoimmune diseases:
- Type 1 DM
- thyroiditis
- Sjögren syndrom
3
Q
Diagnostic histologic features of Celiac disease
A
- villous blunting
- increased intraepithelial lymphocytes
- lymphoplasmacytosis of the lamina propria
4
Q
Pathogenesis of Whipple Disease
A
- Caused by gram-positive bacilli Tropheryma whippelii
- Bacilli absorbed by lamina propria macrophages
- Organism-laden macrophages accumulate within the small intestinal lamina propria and mesenteric lymph nodes → lymphatic obstruction
- Impaired lymphatic transport causes malabsorptive diarrhea
5
Q
Clinical presenation/dx of Whipple disease
A
- Sx:
- Triad of diarrhea, weight loss, malabsorption
- Other common symptoms: arthritis, lymphadenopathy, neurologic disease
- Typically presents in middle-aged or elderly white males
- Dx
- tissue biopsy demonstrates presence of T. whippelii
6
Q
Infectious vs. Non-infectious causes of colitis
A
- Infectious causes of colitis
- Bacterial enterocolitis
- Pseudomembranous colitis
- Viral gastroenteritis
- Parasitic enterocolitis
- Non-infectious causes of colitis
- Ischemic colitis
- Microscopic colitis
7
Q
Major causes of bacterial infectious enterocolitis
A
- Campylovacter spp.
- Shigellosis
- Salmonellosis
- Escherichia coli
8
Q
Characteristics of Campylobacter spp. infection
A
- major cause of diarrhea worldwide
- gram-neg.
- ===> watery diarrhea +/- blood
- found in contaminated poultry, water, unpasteurized dairy
9
Q
Characteristics of Shigella infection
A
- major cause of infectious diarrhea
- virulent, invasive gram-negative bacilli
- ==> severe watery or bloody diarrhea
- transmitted by water contaminated w/feces
10
Q
Characteristics of Salmonella infection
A
- prevalent where sanitation is poor
- **important cause of food poisoning/traveller’s diarrhea
- gram-negative bacilli
- transmitted trhough food, water
11
Q
Characteristics of E. Coli infections
A
- Enterotoxigenic E. Coli
- non-invasive ==> non-bloody diarrhea
- Enteroinvasive E. coli
- invasive (similar to Shigella)
- ==> non-bloody diarrhe, dysentery-like illness
- contaminated cheese, water, person-to-person
- Enterohemorrhagic E. coli
- contaminated hamburgers
- ==> bloody diarrhea, severe cramps
- Enteroadherent E. coli
- non-invasive ==> non-bloody diarrhea
12
Q
Characteristics of pseudomembranous colitis
A
- clinical
- usually C. diff
- commonly following course of antibiotics
- e.g. 3rd gen cephalosporings
- hospitalized pts
- fever, leukocytosis, abd. pain, cramps, watery diarrhea
- histo findings
- Pseudomembranes
- Adherent layer of inflammatory cells and mucinous debris at sites of colonic mucosal injury
- Surface epithelium denuded, mucopurulent exudates
- Pseudomembranes
13
Q
Viral causes of infectious enterocolitis
A
- cytomegalovirus
- herpresvirus
- enteric viruses
- rotavirus
- adenovirus
- norovirus
14
Q
Dx?
A
Pseudomembranous colitis
15
Q
Parasitic causes of infectious enterocolitis
A
- prevalent pathogens in tropic and subtropical countries
- entamoeba histolytica
- giardia lamblia
- cryptosporidium parvum
- helminthic infections
- ascaris lumbricoides (roundworm)
- strongylides stercoralis (nematode)
- schistosomiasis (trematode)
16
Q
Clinical features and presentation of ischemic colitis
A
- Older individuals with co-existing cardiac or vascular disease
- Young patients: long-distance runners, women on oral contraceptives
- Mechanical Obstruction: hernias, volvulus
- Presentation:
- Acute transmural infarction: severe abdominal pain, tenderness, nausea and vomiting, bloody diarrhea and blood in stool
- Peristaltic sounds disappear, rigid abdomen, shock, sepsis
19
Q
Dx?
A
- mucosal necrosis in context of ischemic colitis
22
Q
Histologic characteristics of collagenous colitis
A
- thickened supepithelial collagen band +
- lymphocytic inflammation
23
Q
Dx?
A
- microscopic collagenous colitis
24
Q
Dx?
A
- microscopic lymphocytic colitis
- feature = increased intraepithelial lymphocytes
25
Q
Histologic features of lymphocytic colitis
A
- increased intraepithelial lymphocytes
31
Q
Microscopic findings: Crohn’s vs. Ulcerative Colitis
A
- Inflammation
- Crohn’s: Transmural
- UC: Limited to the mucosa
- Pseudopolyps
- Crohn’s: Moderate
- UC: Marked
- Ulcers
- Crohn’s: Deep, knife-like
- UC: Superficial, broad-based
- Lymphoid reaction
- Crohn’s: Marked
- UC: Moderate
- Fibrosis
- Crohn’s: Marked
- UC: Mild to none
- Serositis
- Crohn’s: Marked
- UC: Mild to none
- Granulomas
- Crohn’s: Yes (35%)
- UC: No
- Fistulae/sinus tracts
- Crohn’s: Yes
- UC: No
32
Q
Dx?
A
Crohn’s disease
33
Q
Dx?
A
Ulcerative colitis
34
Q
Dx?
A
- feature = inflammatory “pseudo” polyp
- dx = ulcerative colitis
35
Q
Dx?
A
- feature = fissuring ulcers
- dx = crohn’s disease
36
Q
Dx?
A
- feature = granuloma
- dx = crohn’s disease
37
Q
Pathogenesis of diverticular disease
A
- Results from decreased dietary fiber → decreased stool bulk → elevated intraluminal pressure → mucosal herniation through focal defects in the bowel wall
- Defects or gaps in the bowel wall are created where nerves, arterial vasa recta and their connnective tissue sheaths penetrate the inner circular muscle coat
- These gaps are reinforced by the external longitudinal layer of the muscualris propria, which in the colon is gathered into 3 bands, the taeniae coli
40
Q
Microscopic/histologic findings in appendicitis
A
- Mucosal ulceration
- Transmural acute and chronic inflammation
- Extension of inflammation into the mesoappendix
41
Q
Dx?
A
