GI Tract Pathology - Small Intestine

Where is the main site for nutrient absorption and fine stages of digestion

Small intestine

Pathologies of the small intestine are generally related to

malabsorption and inability to digest certain nutrients

What is Celiac Disease

aka gluten enteropathy

-a T cell mediated injury to the small intestine mucosa

-it is an allergy to GLIADIN, which is the most toxic component of gluten

What is the most toxic component of gluten

gliadin

Describe the sequence of events in Celiac disease starting with what Gliadin induces

1. Gliadin induces IL 15 expression by epi cells

2. IL 15 activated proliferation of CD8+ T cells in intestinal epi

3. Gliadin peptides leak into lamina propria and are deamidated by tissue transglutaminase and interact with HLA-DQ2 or HLA-DQ8 on APCs

4. APCs stimulate CD4+ T cells to produce cytokines

5. B cell respond with antibody production

The following presentation suggests what disease

-abdominal distension

-diarrhea

-steatorrhea

-bloating

-iron deficiency anemia

-in children, failure to thrive

Celiac Disease

Why does Celiac Disease present with iron deficiency anemia

Celiac disease affects the duodenum, where iron is absorbed

What HLAs is celiac disease associated with?

HLA-DQ2 and HLA-DQ8 (know this)

What ethnicity is Celiac disease associated with

North European descent

It is rare in persons of African or Asian descent

The following histological findings suggest what disease

-flattening of Villi (villous atrophy)

-crypt hyperplasia

-increased intraepithelial lymphocytes

Celiac Disease

Describe the histological findings of Celiac disease

-villous atrophy (flattening of Villi)

-crypt hyperplasia

-increased intraepithelial lymphocytes

In Celiac disease, damage is mostly found in what part of the small intestine

duodenum - Villus atrophy (flattening of Villi)

What are common lab findings in Celiac Disease

anti-tTG (know this)

anti-gliadin IgA (if pt. is IgA deficient, check IgG)

Celiac Disease increases risk of what cancers

Enteropathy-associated T cell lymphona (EATL)

Small intestine carcinoma

What skin manifestations can occur in Celiac Disease? Explain why this occurs.

Dermatitis Herpetiformis (in 10% of pts.)

-IgA accumulates in the dermal papillae and binds to reticular fibers

-Causes herpes-like lesions

What are the similarities in Celiac disease and Tropical Sprue

Both have villus flattening

Both have diarrhea/steatorrhea

What is difference in origin between Celiac disease and Tropical Sprue

Celiac = T cell mediated injury to the small intestine due to allergy to gliadin

Tropical = bacterial origin

What part of the GI tract does tropical sprue affect

Distal small intestine

-jejunum and ileum

What type of anemia can occur in tropical sprue and why?

Megaloblastic anemia

-damages jejunum and ILEUM

-damage to ileum = lack of B12 and folate

-results in megaloblastic anemia

What treatment does tropical sprue respond to

antibiotics

Recent travel to tropical climates would be a clue for what disease

Tropical Sprue

Which describes Celiac disease and which describes Tropical Sprue

-distal small intestine, ileum. decrease in B12 + megaloblastic anemia

-duodenum is affected, decrease in iron absorb = microcytic anemia

Celiac = duodenum + decreased iron + microcytic anemia

Tropical Sprue = ileum + decreased B12 + megaloblastic anemia

What causes Whipple Disease

caused by accumulation of bacterium-loaded macrophages in the villi of the small intestine

causative agent is a gram positive bacterium Tropheryma Whipplei

Tropheryma Whipplei causes what disease

Whipple disease

What causes fat malabsorption and steatorrhea in whipple disease

-Accumulation of FOAMY MACROPHAGES

-causes compression of lacteals and inability to transport chylomicrons

-this results in fat malabsorption and steatorrhea

What does PAS (periodic acid-Schiff) stain for?

stains carbohydrates

The PAS (periodic acid-Schiff) stain can be used to identify the causative agent of what disease

Whipple disease - Tropheryma Whipplei

What disease can cause the following

-steatorrhea

-fat malabsorption

-cardiac symptoms

-joint pain (know this one)

-neurological symptoms

Whipple Disease

-this is a systemic infection

Whipple Disease typically affects what sex and what age group

Typically affects middle-older age men (10:1 M:F ratio)

The following describes what disease

-accumulation of foamy macrophages resulting in compression of lacteals and inability to transport chylomicrons

-steatorrhea

-Enlarged macrophages are positive for the PAS (periodic acid-Schiff) stain

-can cause joint pain

Whipple disease

What causes lactose intolerance

deficiency of lactase

Where is lactase located in the small intestine

located on the apical portion (brush border) of enterocytes

Lactase breaks down lactose into what

glucose and galactose

The following describes what

-diarrhea

-abdominal distension after drinking milk

-NO DAMAGE to villi

Lactose intolerance = deficiency of lactase

What cancers affect the small intestine? What is the most common type

Lymphomas (most common)

GI stomal cell tumor

Carcinoid (neuroendocrine tumor)

Carcinoma

What is Enteropathy-associated T-cell (EATC) lymphoma? It is only found in patients with what disease?

EATC lymphoma = proliferation of T cells from intraepithelial population

only found in pts with Celiac Disease

What is the most common lymphoma throughout the GI tract? What causes this?

Marginal Zone Lymphoma = most common

caused by proliferation of B cells

What is a volvulus

Twisting of the intestine along its mesentery resulting in bowel infarction

A volvulus can lead to

obstruction and infarction

Volvulus of what part of the GI tract is most common in children. What is the main cause of this?

Children = small intestine

Cause = Meckel's diverticulum

Volvulus of what part of the GI tract is most common in elderly patients?

Sigmoid volvulus

The following describes what

-produces coffee bean sign on x-ray

Sigmoid Volvulus - more common in elderly

What is the difference in where a volvulus occurs in the GI tract in children and the elderly

Children = small intestine (due to Meckel's)

Elderly = sigmoid colon

What is intussusception

telescoping of the intestine

Target sign on ultrasound or CT is suggestive of what

intussusception

What is the most common cause of intussusception in children

Meckel's diverticulum or lymphoid hyperplasia

What is the most common cause of intussusception in adults

polyp or tumor

What is the most common cause of intestinal obstruction in infants and young children? What does their stool look like as a result?

Intussusception = most common cause

"currant jelly" stool caused by bowel infarction

What can cause small bowel infarction? How does this present?

athersclerosis and thrombosis of SMA

presents with abdominal pain and if untreated leads to bowel necrosis