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Flashcards in Diseases of lower GI: Pathology Deck (38)

Small Bowel Celiac Disease

exposure to alpha-gliadin peptide results in autoantibody formation


Diagnosis of celiac (and path findings)

Serology: IgA Ab to tissue transglutaminase, anti-endomysial Ab

Endoscopy: "scalloped" mucosa of duodenum

Tissue biopsy: Villous blunting, increased intraepithelial lymphocytes, lymphoplasmacytosis of laminal propria


Extra-intestinal complaints with celiac disease

- Iron deficiency anemia
- Pubertal delay, short stature
- Aphthous stomatitis

Associated with dermatitis herpetiformis blistering skin disease!!!!!!!!!!!!!!!!

Increased incidence of lymphocytic gastritis, lymphocytic colitis

Celiac-disease associated malignancies include enteropathy-associated T-cell lymphoma (EAT Lymphoma), and small intestinal adenocarcinoma


Small Bowel 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

Clinical Features:
Triad of diarrhea, weight loss, malabsorption
Other common symptoms: arthritis, lymphadenopathy, neurologic disease
Typically presents in middle-aged or elderly white males

Tissue biopsy demonstrates the presence of the organisms


Whipple Disease: Microscopic Findings

Villi distended by swollen macrophages

Macrophages filled with Whipple bacilli (PAS stain)


Small bowel- infectious enterocolitis giardiasis

Giardia lamblia: parasitic enterocolitis

Protozoan parasite causing sporadic or epidemic diarrhea, waterborne and foodborne: In US, water is a major source of transmission (camping)

Cysts are resistant to chlorine --> filter necessary

7-14 day incubation period

Chronic diarrhea, malabsorption, flatulence, weight loss, may cause intermittent symptoms


Microscopic findings of giardia

"schools of fish" of protozoans


Large bowel infectious colitis

Infectious causes of colitis:
Bacterial enterocolitis
Pseudomembranous colitis
Viral gastroenteritis
Parasitic enterocolitis


Bacterial infectious colitis

Mostly related to ingestion of contaminated water, food, or foreign travel

These infections typically create an acute self-limited colitis
Patients typically present several weeks after onset of symptoms, therefore tissue biopsy rarely shows classic acute infectious findings

Campylobacter spp.
Enteric (typhoid) fever
Yersinia spp.
Escherichia coli
Mycobacterial infection



Gram negative

Major cause of diarrhea worldwide

Produces a watery diarrhea +/- blood

Found in contaminated meat (poultry), water and unpasteurized dairy

C. jejuni commonly associated with food-borne gastroenteritis

C. fetus more often seen in immunosuppressed patients



Gram-negative bacilli transmitted through food and water

Important cause of food poisoning and traveler’s diarrhea

Typhoid (enteric) Fever (S. typhimurium):

Abdominal pain, headache, fever; Abdominal rash and leukopenia; Diarrhea (not until 2nd week of infection) initially watery then bloody; Characteristic pathology most commonly seen in the ileum, colon, appendix and Peyer’s patches; Perforation and toxic megacolon possible

Non-Typhoid Salmonella species:

Mild self-limited gastroenteritis; Endoscopy: mucosal redness, ulceration and exudates


E. coli

Enterohemorrhagic E. coli (O157:H7 is the most common strain)

Non-invasive, toxin-producing, contaminated hamburgers

Bloody diarrhea, severe cramps, mild or no fever, sometimes renal failure (HUS)

On endoscopy: edema, erosions, ulcers, hemorrhage (right colon mostly)

Deadly outbreaks


Pseudomembranous Colitis

Most often caused by Clostridium difficile

Colitis often occurs after course of antibiotic therapy (“antibiotic-associated colitis”)

Most frequently implicated antibiotics are third-generation cephalosporins

Common in hospitalized patients (up to 30%)

Presents with fever, leukocytosis, abdominal pain, cramps, watery diarrhea

Toxins released cause disruption of epithelial cytoskeleton, tight junction barrier loss, cytokine release and apoptosis


Histological findings in pseudomembranous colitis

Pseudomembranes: Adherent layer of inflammatory cells and mucinous debris at sites of colonic mucosal injury (A “volcano-like” eruption of neutrophils and mucinous debris attached to the surface epithelium)

Surface epithelium denuded, mucopurulent exudates


Infectious enterocolitis- viral

Most cases of acute diarrhea are actually viral

Cytomegalovirus (mouth – anus)

Herpesvirus (esophagus and anorectum)

Enteric Viruses

Most common cause of severe childhood diarrhea and diarrheal mortality worldwide
Children btwn 6-24 months are most vulnerable
Vaccines now available


Parasitic infections of colon

Common in other countries

Protozoal infections:
Prevalent pathogens in tropic and subtropical countries
Diagnosis is primarily by examination of stool samples

Entamoeba histolytica:
10% of world’s population is infected with E. histolytica parasite
Associated with a severe dysentery-like, fulminant colitis
Can disseminate to other sites (liver)
Cecum most commonly affected; “flask-shaped” ulcers in mucosa


Histo findings with Entamoeba histolytica:

Flask-shaped ulcers with organisms in the mucous/fecal material


Helminthic Infections


Most common method of diagnosing is by examination of stool for ova and parasites

Worldwide distribution, many people multiply infected

Cause of serious disease in nations with deficient sanitation systems, poor socioeconomic status and hot, humid climates

Seen in immigrants, patients who travel to endemic areas

Nutritional problems can be severe or life-threatening, especially in children


Ascaris lumbricoides

(roundworm) a kind of helminth

One of most common parasites in humans

Most common in tropics

Ingested from soil contaminated with feces

Obstruction, perforation, growth retardation

Giant worms (up to 20cm) can be identified


Ischemic colitis (clinical features, presentation, and histologic findings)

Clinical Features:
Older individuals with co-existing cardiac or vascular disease
Young patients: long-distance runners, women on oral contraceptives
Mechanical Obstruction: hernias, volvulus

Clinical presentation:
Acute transmural infarction: severe abdominal pain, tenderness, nausea and vomiting, bloody diarrhea and blood in stool
Peristaltic sounds disappear, rigid abdomen, shock, sepsis

Histologic Findings
Varies from focal acute mucosal necrosis to full-thickness necrosis


Two most likely places for ischemic colitis

Watershed areas:

Splenic flecture

Rectosigmoid flecture


Microscopic colitis

Chronic non-bloody watery diarrhea without weight loss
*Endoscopically normal *

Mucosal inflammation on biopsy

Middle aged women

NSAIDs implicated

2 types: Lymphocytic (Increased intraepithelial lymphocytes)
and collagenous (Thickened subepithelial collagen layer)


Biopsy findings for microscopic colitis

Tissue biopsy shows characteristic lymphocytic inflammation +/- a thickened subepithelial collagen layer


Inflammatory bowel disease

IBD encompasses 2 distinct disorders
Crohn(‘s) disease (CD)
Ulcerative colitis (UC)

CD and UC have distinct gross (macroscopic), microscopic and clinical features

Similar epidemiology:
Most common among Caucasians
incidence of IBD 2-9x higher among Ashkenazi Jews
North America, Northern Europe, Australia
World-wide incidence rising


Pathogenesis of IBD

Colitis results from a combination of defects:
Host interactions with intestinal microbiota
Intestinal epithelial dysfunction
Aberrant mucosal immune responses


Crohn's disease (clinical features and disease characteristics)

Clinical Features:

Intermittent attacks of relatively mild diarrhea, fever, abdominal pain

Diarrhea tends to not be bloody (as opposed to ulcerative colitis)

Relapsing and remitting disease

Extraintestinal manifestations (Uveitis, migratory polyarthritis, sacroiliitis, ankylosing spondylitis, erythema nodosum) all these an happen with UC too

Increased risk of colonic adenocarcinoma

Disease characteristics:
Skip lesions

Ileal involvement (“regional enteritis”)

Transmural chronic inflammation

Inflammatory strictures

Fissuring ulcers, sinus tracts, fistulae


Ulcerative colitis (clinical features and disease characteristics)


Clinical Features:

Bloody diarrhea or loose stools with lower abdominal pain, cramps

Symptoms relieved by defecation

Extraintestinal manifestations (Primary sclerosing cholangitis)

Increased risk of colonic adenocarcinoma

Disease characteristics:

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


Thickness of walls in Crohn's and UC

Thickened in Crohn's
Thinned in UC


Microscopic findings in Crohn's disease (Inflammation, pseudopolyps, uclers, lymphoid rxn, fibrosis, serositis, fistulae/sinus tracts)

Transmural inflammation
Moderate pseudopolyps
Deep, knife-like ulcers
Marked lymphoid rxn
Marked fibrosis
Marked serositis
35% granulomas
Fistulae/sinus tracts


Microscopic findings in UC (Inflammation, pseudopolyps, uclers, lymphoid rxn, fibrosis, serositis, fistulae/sinus tracts)

Inflammation limited to mucosa
Marked pseudopolyps
Superficial, broad-based ulcers
Moderate lymphoid rxn
Mild to no fibrosis
Mild to no serositis
No granulomas
No fistulae/sinus tracts


Diverticular disease

Results from decreased dietary fiber → decreased stool bulk → elevated intraluminal pressure → mucosal herniation through focal defects in the bowel wall

Clinical Features:
Most common in sigmoid colon
Prevalence approaches 60% in Western adult populations over age 60
Asymptomatic or intermittent cramping, lower abdominal discomfort



presence of diverticula



inflammation of the diverticula, usually secondary to obstruction


Microscopic findings in diverticulosis

Diverticular outpouching lined by mucosa, submucosa, and variable amounts of muscularis propria


Microscopic findings in diverticulitis

diverticulum becomes infiltrated with acute, then chronic inflammatory cells, and as the inflammation extends, the mucosa ulcerates and pericolonic abscesses, or sometimes fistula form



Clinical Features:
Most common in adolescents and young adults
Lifetime risk for appendicitis is 7%
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

Luminal obstruction by stone-like mass of stool “fecalith”→ ischemic injury and stasis of luminal contents → inflammatory response


Microscopic findings in appendicitis

Mucosal ulceration

Transmural acute and chronic inflammation

Extension of inflammation into the mesoappendix


Crypt architectural distortion

Path findings in both UC and Crohn's