pathology of the gastrointestinal tract part 1 small and large intestines

Pathology of the Gastrointestinal Tract Part 1

Small and Large Intestines

Grace Guzman, [email protected]

The Department of PathologyUniversity of Illinois at Chicago

Atresia and stenosis

Congenital intestinal obstruction

-Complete: Atresia -Incomplete: Stenosis Duodenal: most common -Jejunum and ileum:

equal -Rectum: rare Developmental failure intrauterine vascular

accidents, or intussuception

Imperforate anus

Persistence of omphalomesenteric duct (vitelline duct)

Disease of 2’s-2% of population (mostly

asymptomatic)-M:F 2:1-2” in length-2 ft of ileocecal valve-2 types of ectopic tissue

in 1/2 of cases (gastric and pancreatic)

-2 major complications (pain with inflammation; hemorrhage with ulcer)

Meckel Diverticulum

Congenital Aganglionic Megacolon

“Hirschsprung Disease”

Absence of ganglia -submucosal (Meissner) -myenteric (Auerbach)

Alternating obstruction and diarrhea

Aganglionic segment causes functional obstruction with distention proximal to aganglionic segment

M:F 4:1 Down syndrome (10%)and (5%) serious neurologic abnormalities

1 in 5000 to 8000

Presents in neonatal period (failure to pass meconium; abdominal distention)

Risk of perforation, sepsis, enterocolitis, fluid disturbances

Acquired (Chagas disease)

Intestinal neuronal plexus develop from neural crest cellsmigrate to the bowel during development

SporadicFamilial

Gentic defects:Endothelin 3GCDGFReceptor tyrosine kinase

Enterocolitis

Infectious Necrotizing Pseudomembranous

Infectious-Viral (Rotavirus, Norwalk)-Bacterial E. coli; Shigella; V. Cholerae; C. difficile-Parasites and protozoa (nematodes; flatworms; protozoa -Giardia lambdia; E. histolytica)

Necrotizing enterocolitis

Acute, necrotizing inflammation of small and/or large intestines

Most common acquired GI emergency in premature or low birth weight neonate

Mild GI symptoms or fulminant illness

Multifactorial - immaturity of the gut’s immune system

Release of cytokines and endotoxins damages mucosa and blood supply

Terminal ileum or ascending colon

Edema to necrosis to gangrenous bowel

Pseudomembranous colitis (antibiotic associated)

Yellow green false membrane (mixture of mucous and neutrophils)

Toxin produced by Clostridium difficile (acquired nasocomially in 20% of pxs in long term hospitalization)

Antibiotics allow overgrowth of C. difficile

Sudden onset of fever and diarrhea in a patient who is seriously ill or post operative who is receiving antibiotics

diarrhea, dehydration, shock death

Exotoxin A and Bbinds to enteric receptorsinactivates RhO cytoplasmic proteinscausing injury to actin filaments andcell retraction

Dx: C. difficile cytotoxin in stoolResponse to tx is usually prompt Relapse occurs in up to 25% of px

Malabsorption

Defect in the assimilation of food (digestion and absorption)

Intraluminal stagea. Secretory Phase (Chronic pancreatitis/insufficiency)b. Biliary Phase (Biliary obstruction due to calculus of

or tumor)

Intestinal Stage (terminal digestion)

a. Surface Phase (Celiac disease; bowel resection)b. Cellular Phase (Disaccharidase deficiency)

Removal Stage (transepithelial transport)

a. Delivery Phase (Whipple diease)

Celiac sprue

Gluten, gliadin protein in wheat, oat, barley, and rye

hypersensitivity (immunologic) reaction to gluten

90-95% - HLA DQ heterodimer in Ch 6

Whites - rare in native Africans, Japanese, Chinese

Gluten - malabsorption -gluten free - improvement

Long term risk of malignancy -lymphoma (2X normal)

Distinct from Tropical sprue

Celiac disease: loss of villiincreased crypts, inflammation,intraepithelial lymphocytes,loss of brush border, goblet cells

Whipple disease

Rare Gram positive rod

shaped actinomycete: Tropheryma whippleli

Engulfed by macrophages (PAS positive diastase resistant)

Electron microscopy M:F 10:1

Inflammation

1. Miscellaneous-graft vs. host-drug induced-radiation enterocolitis-neutropenic colitis-diversion colitis

2. Acute appendicitis-etiology: bacteria-fecalith impairing

circulation, causing ischemia, necrosis and bacterial contamination

-acute abdomen -RLQ pain-McBurney’s point

-fever and leukocytosis

Inflammation

3. Collagenous and lymphocytic colitis

Etiology: unknown possibly auto-immune chronic watery diarrhea

in middle aged and older women

spectrum of disease ranging from increased intraepithelial lymphocytes to the presence of collagen band under the surface epithelium

Idiopathic Inflammatory Bowel disease

Inflammatory bowel disease (IBD) - single term to collectively refer to either Crohn disease or ulcerative colitis

Etiology unknown

a. Genetic predisposition:HLA Class II locus on Ch 6

b. Abnormal host immunoreactivity

Crohn disease: Regional enteritis

1. Chronic inflammation involving all layers (transmural) of the SI

may occur at any point along the GI tract

primarily involving SI and LI

2. Mucosa shows linear ulceration and fistula

3. Segmental involvement/sparing

Serosal creeping fat

Crohn disease: Regional enteritis Inflammation spread

through the bowel wall to adjacent mesenteric fat

-characteristic non-caseating granulomas

tends to occur in young adults

increased incidence of cancer of SI and colon

diarrhea, crampy abdominal pain, fever

complications: fistula, obstruction, occult blood loss, Fe++ def anemia

malabsorption, malnutrition, weight loss

Ulcerative colitis1. Inflammation primarily

involving the mucosa of the colon

2. Diffuse, continuous inflammation that begins in the rectum and progresses proximally

3. Pseudopolyp formation4. Bloody diarrhea, from

ruptured vessels in inflamed mucosa

Toxic megacolon - rare complication - prominent dilatation and septic shock

Ulcerative colitis

Early phase: neutrophils accumulate within the depths of the crypts of Leiberkuhn forming crypt abscesses

Later phase: mucosa ulcerates and pseudo-polyps form

Late phase: after many years, mucosa becomes dysplastic, increasing risk of colon carcinoma

Between Crohn and UC, this finding is more commonly seen in:

Transmural inflammation pseudopolyp granuloma diffuse skip lesions toxic megacolon creeping fat Primary Sclerosing Cholangitis

fissures and fistulas Cancer at any point in GI tract Rectum

Crohn UC Crohn UC Crohn UC Crohn both but more in UC Crohn both but more in UC Crohn UC

Vascular diseases:a. Ischemic bowel diseaseb. Angiodysplasiac. Hemorrhoids

Ischemic bowel disease -blood clot in mesenteric

artery causing ischemia, transmural infarction, necrosis of bowel, peritonitis

a.embolus: superior mesenteric artery

-source: embolus of heart (mural thrombus, valvular vegetation)

b. thrombus (arterial; venous: ATIII def, cirrhosis, OC)

c. hypoperfusion (non-occlusive): shock, CHF

50-75% death rateolder px with cardiac, vasc diseaseD/Dx: IBD

Vascular diseases:a. Ischemic bowel diseaseb. Angiodysplasiac. Hemorrhoids

Angiodysplasia -ectasia of veins -prone to rupture -GI bleeding -Osler-Weber-Rendu

syndrome (hereditary hemorrhagic telangiectasia)

Hemorrhoids -dilated veins of

hemorrhoidal plexus -Internal -External -(BRBPR or streaks on

stool), thrombosis, pain

Prevalence:<1%20% of significant LGI bleed

5% of populationelevated venous pressureconstipationstraining venous stasis of pregnancycollateral channels in portal HTNrare under 30 except in pregnant women

Non-neoplastic bowel diseasesa. Diverticular diseaseb. Herniasc. Adhesionsd. Intussusceptione. Volvulus

Diverticular disease: Diverticulosis and

Diverticulitis Acquired herniation Most common in left

colon; particularly sigmoid colon

Acute or chronic inflammation may occur

Perforation, peritonitis, fistula

Acquiredrare under 30western pop over 60prevalence: 50%

Non-neoplastic bowel diseasesa. Diverticular diseaseb. Herniasc. Adhesionsd. Intussuceptione. Volvulus

Hernias-Serosal lined out-

pouching of peritoneum-Loop of intestines

becomes trapped (incarcerated) within the hernia sac

-Bowel compressed, twisted at the mouth of hernia, compromising blood supply - infarction (strangulation)


Adhesions -string-like or band-like portions of scar tissue that

form during healing after surgery or peritonitis -may result in obstruction (kinking, compression)

Non-neoplastic bowel diseasesa. Diverticular diseaseb. Herniasc. Adhesionsd. Intussusceptione. Volvulus

Intussusception -caused by an in-folding or telescoping of one

segment of bowel into the adjacent distal segment Infants and children: spontaneous and reversible Adults: tumor is usually a lead point


Volvulus -obstruction due to

rotation or twisting of a loop of bowel around its mesenteric base of attachment

Sigmoid - most common site (cecum next)

pathology of the gastrointestinal tract part 1 small and large intestines

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