Pathology of Lower GI Tract Flashcards Preview

DEMS: Unit 1 > Pathology of Lower GI Tract > Flashcards

Flashcards in Pathology of Lower GI Tract Deck (41):
1

Celiac disease ("Gluten-Sensitive Enteropathy") pathogenesis

  • 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

Common associations/genetics of Celiac Disease

  • Genetic associations: Class II HLA-DQ2 or HLA-DQ8 allele
  • Association with other autoimmune diseases:
    • Type 1 DM
    • thyroiditis
    • Sjögren syndrom

3

Diagnostic histologic features of Celiac disease

  • villous blunting
  • increased intraepithelial lymphocytes
  • lymphoplasmacytosis of the lamina propria
     

4

Pathogenesis of Whipple Disease

•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

Clinical presenation/dx of Whipple disease

  • 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

Infectious vs. Non-infectious causes of colitis

 

  • Infectious causes of colitis
    • Bacterial enterocolitis
    • Pseudomembranous colitis
    • Viral gastroenteritis
    • Parasitic enterocolitis
  • Non-infectious causes of colitis
    • Ischemic colitis
    • Microscopic colitis
       

7

Major causes of bacterial infectious enterocolitis

  • Campylovacter spp.
  • Shigellosis
  • Salmonellosis
  • Escherichia coli

8

Characteristics of Campylobacter spp. infection

  • major cause of diarrhea worldwide
  • gram-neg. 
  • ===> watery diarrhea +/- blood
  • found in contaminated poultry, water, unpasteurized dairy

9

Characteristics of Shigella infection

  • major cause of infectious diarrhea
  • virulent, invasive gram-negative bacilli
  • ==> severe watery or bloody diarrhea
  • transmitted by water contaminated w/feces

10

Characteristics of Salmonella infection

  • prevalent where sanitation is poor
    • **important cause of food poisoning/traveller's diarrhea
  • gram-negative bacilli
  • transmitted trhough food, water

11

Characteristics of E. Coli infections

  • 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

Characteristics of pseudomembranous colitis

  • 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
       

13

Viral causes of infectious enterocolitis

  • cytomegalovirus
  • herpresvirus
  • enteric viruses
    • rotavirus
    • adenovirus
    • norovirus

14

Dx?

Pseudomembranous colitis

15

Parasitic causes of infectious enterocolitis

  • prevalent pathogens in tropic and subtropical countries
  • entamoeba histolytica
  • giardia lamblia
  • cryptosporidium parvum
  • helminthic infections
    • ascaris lumbricoides (roundworm)
    • strongylides stercoralis (nematode)
    • schistosomiasis (trematode)

16

Clinical features and presentation of ischemic colitis

  • 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
       

17

Pathogenesis & Histologic findings in ischemic colitis

  • Pathogenesis:
    • decreased blood flow due to:
      • low CO
      • occlusive dz of bowel vascular supply
  • Histologic findings
    • acute mucosal necrosis vs. full-thickness necrosis 

18

Common locations of ischemic colitis

  • @ splenic flexure = superior & inferior mesenteric artery watershed
  • @ sigmoid colon = inferior and hypogastric artery watershed

19

Dx?

  • mucosal necrosis in context of ischemic colitis

20

Dx?:

  • chronic, non-bloody watery diarrhea
  • no weight loss
  • normal endoscopic exam
  • mucosal inflammation on biopsy

  • microscopic colitis
    • collagenous colitis
    • lymphocytic colitis

21

Characteristics of microscopic colitis

  • •Clinical Features
    • •Presents primarily in middle-aged and older women
    • •NSAIDs implicated
  • •Diagnosis
    • •Endoscopy: Normal
    • •Tissue biopsy shows characteristic lymphocytic inflammation +/- a thickened subepithelial collagen layer
  • Major types=
    • collagenous colitis
    • lymphocytic
      • strong association with celiac disease, lymphocytic gastritis and other autoimmune diseases such as thyroiditis
  •  

22

Histologic characteristics of collagenous colitis

  • thickened supepithelial collagen band +
  • lymphocytic inflammation

23

Dx?

  • microscopic collagenous colitis

24

Dx?

  • microscopic lymphocytic colitis
  • feature = increased intraepithelial lymphocytes

25

Histologic features of lymphocytic colitis

  • increased intraepithelial lymphocytes

26

Clinical features of Crohn's disease

  • •Variable
    • •Intermittent attacks of relatively mild diarrhea, fever, abdominal pain
    • •Bloody diarrhea
    • •Relapsing and remitting disease
  • •Extraintestinal manifestations
    • •Uveitis, migratory polyarthritis, sacroiliitis, ankylosing spondylitis, erthyema nodosum
  • •Increased risk of colonic adenocarcinoma
     

27

Disease characteristics of Crohn's disease

•Skip lesions
•Ileal involvement (“regional enteritis”)
•Transmural chronic inflammation
•Inflammatory strictures
•Fissuring ulcers, sinus tracts, fistulae
 

28

Clinical features of ulcerative colitis

  • Bloody diarrhea with stringy, mucoid material, lower abdominal pain, cramps
    • Symptoms relieved by defecation
  • Extraintestinal manifestations
    • Primary sclerosing cholangitis
  • Increased risk of colonic adenocarcinoma

29

Disease characteristics of ulcerative colitis

•Rectal involvement with retrograde continuous diffuse disease
•No ileal involvement (except “backwash ileitis”)
•Disease worse distally
•Mucosal inflammation only – no transmural disease
•No fissures, sinuses, fistula tracts
 

30

Macroscopic findings: Crohn's vs. Ulcerative Colitis

  • Distribution of disease 
    • Crohn's: Skip lesions 
    • UC: Diffuse
  • Bowel involved 
    • Crohn's: Ileum +/- colon 
    • UC: Colon only
  • Strictures 
    • Crohn's: Yes 
    • UC: Rare
  • Wall appearance 
    • Crohn's: Thickened 
    • UC: Thinned

31

Microscopic findings: Crohn's vs. Ulcerative Colitis

  • 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

Dx?

Crohn's disease

33

Dx?

Ulcerative colitis

34

Dx?

  • feature = inflammatory "pseudo" polyp
  • dx = ulcerative colitis

35

Dx?

  • feature = fissuring ulcers
  • dx = crohn's disease

36

Dx?

  • feature = granuloma
  • dx = crohn's disease

37

Pathogenesis of diverticular disease

•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
 

38

Clinical features of diverticular disease

•Most common in sigmoid colon
•Prevalence approaches 60% in Western adult populations over age 60
•Asymptomatic or intermittent cramping, lower abdominal discomfort
•Diverticulosis = presence of diverticula
•Diverticulitis = inflammation of the diverticula, usually secondary to obstruction
 

39

Clinical features of appendicitis

•Most common in adolescents and young adults
•Lifetime risk for appendicitis is 7%
•M>F
•Classic finding is McBurney’s sign, tenderness located 2/3 of the distance from the umbilicus to the right anterior superior iliac spine
•Often presents as an acute abdomen
•Appendectomy is treatment of choice; often laparoscopic
 

40

Microscopic/histologic findings in appendicitis

•Mucosal ulceration
•Transmural acute and chronic inflammation
•Extension of inflammation into the mesoappendix
 

41

Dx?