Gi Pathology, Lecture 4: Pathology Of The Small Intestine

Front 1

Small Intestine
Congenital Disorders

Name 5

Back 1

o Atresia or stenosis
o Duplications and enteric cysts
o Malrotations
o Herniations
o Meckel's diverticulum

Front 2

Small Intestine
Congenital Disorders

1) Atresia refers to _________

2) while stenosis refers to _________

3) Both are rare and present in the early post-natal period with ___________

Back 2

1) refers to the complete absence of the intestinal lumen

2) describes partial occlusion

3) obstruction and affect only a segment of bowel

Front 3

Small Intestine
Congenital Disorders

Meckel’s Diverticulum
(most common)

Back 3

- Results from persistence of the vitelline duct

- “Blind pouch” 5-6 cm in length

- Antimesenteric border of ileum (approx. 85 cm from cecum)

- Usually asymptomatic/incidental

- Can present with symptoms due to bacterial overgrowth, mechanical alterations (e.g. intussusception) or ectopic mucosa

- Ectopic gastric mucosa can elaborate gastric secretions and lead to peptic ulceration, which can be complicated by perforation or fistula formation.

Inflammation and hemorrhage can also be associated with obstruction.

Front 4

SMALL BOWEL OBSTRUCTION

T/F

In general, obstruction is less common in the small intestine than the large intestine

Back 4

False

In general, obstruction is MORE common in the small intestine than the large intestine, because of the smaller lumen and its more mobile mesenteric attachments.

Front 5

SMALL BOWEL OBSTRUCTION

Mechanical obstructions can result secondary to:

Back 5

o hernias
o intestinal adhesions
o intussusception or volvulus
o tumors or inflammatory strictures
o gallstones or foreign bodies
o congenital strictures or atresias

Front 6

Of the ones just listed, the major causes of small bowel obstruction are:

(name 4)

Back 6

hernias, intestinal adhesions, intussusception, and volvulus

Front 7

SMALL BOWEL OBSTRUCTION

Hernias lead to entrapment of bowel and obstruction or ischemic necrosis (strangulation).

Permanent entrapment of bowel is often referred to as an __________

Back 7

loops of small intestine (or omentum and other organs) can herniate through congenital or acquired defects in the abdominal wall leading to _______


incarcerated hernia.

Front 8

SMALL BOWEL OBSTRUCTION

Adhesions caused by

Back 8

Inflammation of the peritoneum that can lead to the formation of fibrous adhesions between bowel segments and/or the abdominal wall.

They can entrap bowel as described for hernias..

Front 9

SMALL BOWEL OBSTRUCTION

Intussusception refers to

Back 9

the telescoping of proximal bowel into the immediately distal segment.

It is unusual in adults unless accompanied by an intraluminal mass which is ‘grabbed’ by a contracting segment and gets pulled into it with it’s associated wall.

Front 10

SMALL BOWEL OBSTRUCTION

Volvulus refers to

Back 10

the twisting of a loop of bowel with resultant ischemia secondary to venous and sometimes arterial obstruction.

Front 11

Vascular Diseases

Acute Intestinal Ischemia

can be caused by 4 separate phenomena:

Back 11

Arterial occlusion

Venous thrombosis

Non-occlusive

Volvulus, Adhesions, or Herniation

Front 12

Vascular Diseases

Acute Intestinal Ischemia

Clinical presentation:
Pathology:
Complications:

Back 12

Clincal Presentation:
Abdominal pain, bloody diarrhea

Pathology:
- Segmental congestion, edema, hemorrhage
- Mucosal to transmural necrosis

Complications
- Adynamic ileus, perforation with peritonitis, “free air”, and septicemia

What is this?

Front 13

Malabsorption

Name the causes and examples of diseases (5 causes)

Back 13

- Abnormal Intraluminal Digestion (e.g., pancreatitis, cystic fibrosis)

- Primary abnormalities of the lining epithelium (enterocytes) Terminal digestion - defective hydrolysis of carbohydrates and peptides at the brush border (e.g, disaccharidase deficiency)
Abnormal transepithelial transport of fluids and nutrients (e.g., abetalipoproteinemia)

- Decreased absorptive surface area (e.g., Celiac disease, Crohn's disease, surgical resection)

- Lymphatic obstruction (e.g., lymphoma or tuberculosis)

- Infection (e.g., Whipple's disease)

Front 14

Malabsorption

Lactose Intolerance is an example of:

Back 14

example of defective mucosal cell absorption.

This is a deficiency of disaccharidase in the brush border of the enterocyte which leads to buildup of carbohydrates in the lumen with subsequent bacterial overgrowth, diarrhea, gas, and bloating.

Front 15

Malabsorption

Abetalipopoteinemia

Back 15

example of a genetic deficiency in a mucosal enzyme.

This is a rare autosomal recessive disorder characterized by a deficiency of apoprotein B, which is required for the assembly of chylomicrons.

As a result, the mucosal epithelial cell is unable to export lipids.

Presents in infancy with diarrhea and steatorrhea with failure to thrive.

It is also associated with abnormalities in myelinization and cell membrane formation.The cells contain lipid vacuoles, but the mucosa otherwise appears normal.

Histologically characterized by acanthocytes (spiny cells)

Front 16

Malabsorption

Celiac Disease

Back 16

example of a non-infectious disease associated with decreased absorptive surface area.

results from immunologic hypersensitivity (CD4 T-cell mediated) to cereal proteins (gliadin peptides).

The disease is responsive to a gluten-free diet and is often known as gluten-sensitive enteropathy.

There is a strong genetic component (HLA-DQ2)

Front 17

Clinically it can be associated with a cutaneous disease known as dermatitis herpetiformis and there is a modest increase in risk for lymphoma.

Back 17

Malabsorption

Celiac Disease

Front 18

Histology of Celiac Sprue:

Back 18

The small bowel shows a very typical but nonspecific response to immune-mediated injury with flattening or blunting of the villi, giving an appearance that more resembles large bowel mucosa.

The glandular and surface epithelium is infiltrated by activated T cells, and there is associated intense infiltration of the lamina propria by lymphocytes and plasma cells.

Front 19

MALABSORPTION

Whipple's Disease an example of:

(It is caused by a gram-positive bacterium, Tropheryma whippelii)

Back 19

example of an infectious disease.

- a systemic infectious disorder that typically involves the small intestine with malabsorption and has frequent involvement of joints, central nervous system, and other organs.

Its protein and chronic manifestations make it very hard to diagnose.

Humans are the only known host and patients with the infection usually have some mild form of underlying immunodeficiency.

Histologically characterized by infiltration of the lamina propria of the small intestine by foamy PAS-positive macrophages that contain the microorganisms.

The inflammatory reaction can interfere with nutrient export via lymphatics.

Front 20

Infectious Enterocolitis

Can be from 3 sources:

Back 20

1) Bacterial
Toxigenic bacteria - diarrhea
Invasive bacteria - dysentery


2) Viral
Viral gastroenteritis

3) Parasitic

Front 21

Most common parasitic infection in the US is?

Back 21

The most common in the US is Giardiasis (flagellated protozoan)

(Giardiasis) - attach to enterocytes in proximal small intestine and deconjugate bile salts

All are associated with ingestion of fecal contaminants.

Front 22

Infectious Enterocolitis

Toxigenic bacteria - diarrhea (primarily affects which part of the small intestine?)

Invasive bacteria - dysentery
(primarily affects which part of the small intestine?)

Back 22

Toxigenic bacteria (diarrhea) - associated with the release of enterotoxins that alter epithelial function in the proximal small intestine


Invasive bacteria (dysentery) - commonly involve the distal small intestine (and colon)

Front 23

CROHN'S DISEASE - A TYPE OF INFLAMMATORY BOWEL DISEASE

Define and characterize:

Back 23

an idiopathic systemic inflammatory disease that involves the intestines

Deranged mucosal immunity

Abnormal cytokines, receptors, T-cells

Probably elicited by microorganisms or microbial products in susceptible host

20% CARD-15 mutations – protein in epithelial cell/antigen interaction
Antibodies – anti-Saccharomyces cerivisiae, p-ANCA, anti-E.coli outer membrane protein

Paneth cells – ATG16/1

Front 24

CROHN'S DISEASE - A TYPE OF INFLAMMATORY BOWEL DISEASE

Clinical Presentation;

Back 24

Abdominal pain, bloody diarrhea, malabsorption (loss of surface area), fever, and sometimes a palpable abdominal mass.

Characterized by remissions and exacerbations of active disease over a several years.

Intestinal obstruction and fistulas are common complications.


Apthous ulcers, perianal fissures

Cutaneous, ocular and hepatic manifestations

Increased risk of bowel carcinoma

Front 25

Crohn’s DiseasePathology

Gross Presentation

Back 25

Classically involves the terminal ileum but can involve the colon and more proximal GI tract (40/30/30)

Segmental disease with “skip lesions”

Thickened wall with narrowed lumen

Longitudinal serpentine ulcers and cobblestoned mucosa

Serosal “fat wrapping” or “creeping fat”

Regional lymphadenopathy

Front 26

Crohn’s Disease

Histopathology:

Back 26

Transmural chronic inflammation or fibrosis

Mucosal ulceration

Non-specific mucosal injury (cryptitis, crypt abcesses)

Epithelioid granulomas (40-50%)

Architectural disarray

Front 27

Neoplasms Benign Tumors

Several types: (4)

Back 27

Adenomas
- Tubular or villous, most common in the duodenum
- Peutz-Jeghers syndrome

Hamartomatous polyps

Lipomas

Leiomyomas

Front 28

Malignant Neoplasms
Small Intestine

Adenocarcinomas

T/F
Adenocarcinomas are the most common small intestinal malignant neoplasm (approximately 50%). They are virtually identical in appearance to enteric colon cancers.

Back 28

True

Front 29

Malignant Neoplasms
Small Intestine

Adenocarcinomas


Risk factors include _________ and ________

Consistent with the distribution of adenomas, they are most common in the ________. These tumors can occur at the ampulla of Vater and present with ________________

Back 29

FAP and Crohn's

duodenum

obstructive jaundice.

Front 30

Neoplasms

Carcinoid tumors

Define and characterize presentation:

Classic Histological presentation:

Back 30

Endocrine differentiation
(resemble pancreatic islet cells --> neuroendocrine cells)

Approximately 20% of small bowel malignancies can arise in:
- Terminal ileum (~2/3)
- Meckel’s diverticulum
- Duodenum (gastrinomas)

25-30% multifocal

Small (most <2cm)

Classic Histological presentation: Salt and Pepper nuclei (classic for neuroendocrine tumors)

Front 31

Carcinoid tumors

The tumors can have __________ submucosal growth patterns and have a homogeneous _________ color

Back 31

polypoid or circumferential

yellow

Front 32

Carcinoids are often associated with a prominent desmoplastic response, which can lead to _________________.

T/F
Like appendiceal and rectal carcinoids, they do not frequently metastasize.

Back 32

kinking of the bowel with resultant obstruction

False:

Unlike appendiceal and rectal carcinoids, they frequently metastasize, and the risk of metastasis correlates with tumor size. Tumors with a diameter of > 2 cm are considered malignant regardless of their histological features.

Front 33

T/F

Gastrointestinal lymphomas do not involve bone marrow, spleen or liver at the time of diagnosis

Back 33

True