Gi Pathology, Lecture 5: Pathology Of The Large Intestine

Front 1

CONGENITAL ANOMALIES

Hirschsprung's disease

Back 1

Colonic dilation due to congenital absence of ganglion cell in the wall of the rectum (first described 1886)

- inability to pass feces

Front 2

CONGENITAL ANOMALIES

Hirschsprung's disease

1) Epidemiology:
2) Clinical Features:

Back 2

1) Epidemiology - 1 in 5000 births - 80% of the patients are male

2) Clinical Features
a. presentation neonatal period with severe constipation and failure to pass of meconium
b. complications are acute intestinal obstruction and enterocolitis
c. surgical repair (pull through procedure, first performed for this disease in the 1940s) usually with excellent outcome

Front 3

CONGENITAL ANOMALIES

Hirschsprung's disease

3) Pathogenesis

Back 3

Pathogenesis:
a. interruption of the normal caudal migration of neural crest cells
b. most cases sporadic; 10% familial (RET gene involved)

Front 4

CONGENITAL ANOMALIES

Hirschsprung's disease

4) Pathology

Back 4

4) Pathology

a. absent ganglion cells (parasympathetic) in both plexuses of the bowel, hypertrophied nerve fibers are present
b. aganglionic segment is contracted and the unaffected proximal segment is dilated (megacolon)
c. 90% cases involve the rectum and distal sigmoid colon

Front 5

Name causes of:

acquired colonic dilation (acquired megacolon)

Back 5

obstructing inflammatory or neoplastic strictures,
acquired neural or muscular dysfunction (e.g., diabetes, Parkinson’s, certain infections),
and various functional or psychogenic disorders

are all causes of what kind of disorder?

Front 6

DIVERTICULAR DISEASE

Diverticular disease (diverticulosis) refers to

1) Epidemiology:
2) Clinical features:
3) Pathogenesis

Back 6

acquired outpouchings of the mucosa and submucosa through defects in a weakened muscularis propria (outer muscle layer) of the colon.

1) Epidemiology
a. North America and Europe, 50% elderly population (M=F),
b. uncommon under age 40
c. disease is rare in Asia, Africa and South America

2) Clinical features
a. usually asymptomatic
b. ~10% cases complicated by inflammation (diverticulitis) that causes severe abdominal pain and fever.
c. diverticulitis can lead to perforation and fistula formation

3) Low dietary fiber may contribute. May lead to abnormal peristalsis, increased luminal pressure and outpouching through weak points in the colonic wall.

Front 7

DIVERTICULAR DISEASE

Diverticular disease (diverticulosis) refers to

4) Pathology

Back 7

4) Pathology

a. although any part of the colon can be involved, ____________ are most common in the sigmoid (left) colon
b. __________ lacks muscle layer except residual muscularis mucosae
c. no recognizable defects in the mucosa or bowel wall

Front 8

VASCULAR DISEASE

Ischemic Colitis

1) Clinical features

Back 8

1) Clinical features - can result secondary to arterial causes (stenosis or occlusion secondary to atherosclerosis, emboli, or thrombosis; hypotension from cardiac failure or shock; vasculitis) or venous causes (thrombosis from either a hereditary or acquired hypercoagulable states; mechanical factors such as torsion, hernias or adhesion bands). Acute ________ usually presents with abdominal pain and/or bloody diarrhea.

Front 9

VASCULAR DISEASE

Ischemic Colitis

2) Pathology

Back 9

As in the small bowel, the major pathologic finding is ischemic necrosis, which preferentially or initially involves the mucosa.

The most common cause of acute transmural infarction of the colon is acute mesenteric artery obstruction.

Bowel involvement is typically segmental, in the distribution of the involved vessels.

Ischemia secondary to hypotension often preferentially involves so-called "watershed areas" in regions at the junction between different arterial beds (e.g., splenic flexure, rectosigmoid area).

Chronic ischemia can result in fibrosis and stenosis of the involved segment.

Front 10

VASCULAR DISEASE
Angiodysplasia

1) Epidemiology
2) Clinical features
3) Pathology

Back 10

1) Epidemiology – mean age of diagnosis is 65 (common in elderly, rare in children)

2) Clinical features – associated with intermittent chronic bleeding and can present with anemia

3) Pathology
a) localized arteriovenous malformations involving mucosa and submucosal, see group of thin walled vessels typically less than 1 cm in diameter
b) predominantly occur in the cecum and ascending colon

Front 11

VASCULAR DISEASE
Hemorrhoids

1) Epidemiology
2) Pathology

Back 11

1) Epidemiology – associated with a Western diet, increasing age, pregnancy, and portal hypertension secondary to liver cirrhosis

2) Pathology

a. Dilated venous channels within the anorectal submucosa. Internal ________ occur above the anorectal junction, while external _________ occur below this junction
b. Usually developing secondary to increased pressure in the __________ vascuar plexus
c. __________can undergo thrombosis, leading to pain, and/or ulcerate leading to rectal bleeding

Front 12

VASCULAR DISEASE

Name 3 types:

Back 12

Ischemic Colitis
Angiodysplasia
Hemorrhoids

Front 13

INFECTIONS

Patients with infectious enterocolitis usually present with ________

Back 13

diarrhea - regardless of etiologic agent.

Front 14

INFECTIONS

Pseudomembranous colitis

Define:

Back 14

a relatively common and potentially fatal mucosal reaction to toxins produced by Clostridium difficile.

Most cases are associated with prior antibiotic therapy, which decreases normal bacterial flora, but can accompany ischemia, cancer, and other debilitating disorders.

Front 15

INFECTIONS

Pseudomembranous colitis

Presentation:

Gross Presentation:

Histology:

Back 15

The clinical presentation includes diarrhea, fever, and abdominal cramps.

Gossly (endoscopically) characterized by adherent plaques of exudate interspersed by inflamed mucosa.

Histologic findings are nonspecific but characterized by areas of epithelial necrosis with overlying "mushroom cap" acute inflammatory exudate.

Front 16

2 Hallmarks of ACTIVE ulcerative Colitis

(EXAM)

Back 16

Cryptitis

Crypt Abscesses

Front 17

INFLAMMATORY BOWEL DISEASE

Ulcerative Colitis


1) Epidemiology
2) Clinical features
3) Pathogenesis

Back 17

1) Epidemiology – Most cases between 20-30, second peak of incidence 70-80

2) Clinical features – Chronic diarrhea and bleeding usually of prolonged duration with many remissions and exacerbations. Anemia is a common feature.

3) Pathogenesis – Still an idiopathic disease, recent work supports an abnormal innate immune response to antigens derived from bacterial flora.

Front 18

INFLAMMATORY BOWEL DISEASE

Ulcerative Colitis

Extra colonic manifestations (EXAM)

Back 18

It is a systemic disorder, and can be associated with a variety of extracolonic manifestations involving:

the joints (migratory arthritis),

eyes (uveitis),

skin (e.g., erythema nodosum),

and/or biliary tract (primary sclerosing cholangitis)

Front 19

INFLAMMATORY BOWEL DISEASE

Ulcerative Colitis

4) Pathology
Gross:
Histology:

5) Complications

Back 19

4) Pathology-
Is a diffuse mucosal disease that involves the rectum but extends proximally while sparing the small intestine (proctitis to pancolitis).

Grossly (endoscopically) it shows mucosal inflammation with hyperemia and congestion and areas of mucosal necrosis and superficial or deep ulceration. With active disease,

the mucosa shows acute crypt injury with infiltration by neutrophils (cryptitis and crypt abscess formation) with chronic inflammation of the surrounding lamina propria.

Front 20

INFLAMMATORY BOWEL DISEASE

Crohn's Disease (differentiating features from UC)

Back 20

Segmental (skip lesions)

Transmural – variable mural thickening/fibrosis and serosal inflammation (serositis)

Epithelioid granulomas

Deep linear/fissuring ulcers; fistulae common

Strictures common

Front 21

INFLAMMATORY BOWEL DISEASE

Ulcerative Colitis

5) Complications

Back 21

5) Complications

When treated or inactive, the mucosa can show gland atrophy, fibrosis of the lamina propria, and abnormalities in gland structure (crypt architectural distortion).

The most serious complication of longstanding ______ of many years duration is dysplasia and subsequent development of invasive adenocarcinoma

Front 22

T/F

On mucosal biopsies, CD can closely resemble UC with cryptitis and crypt abscess formation.

Back 22

True

On mucosal biopsies, CD can closely resemble UC with cryptitis and crypt abscess formation.

Front 23

T/F

Like UC, CD is also associated with a significant increase in the risk of developing colon cancer.

Back 23

True

Like UC, CD is also associated with a significant increase in the risk of developing colon cancer.

Front 24

The most common benign non-mucosal tumor of the large bowel is the ___________

Back 24

leiomyoma

Front 25

T/F

Small, submucosal smooth muscle tumors of the rectum are almost always malignant

Back 25

False

Small, submucosal smooth muscle tumors of the rectum are almost always benign.

Front 26

T/F

Carcinoid tumors are fairly uncommon in the rectum, frequently produce vasoactive substances, are usually large at the time of diagnosis, and have a comparatively poor prognosis.

Back 26

False

Carcinoid tumors are fairly COMMON in the rectum, INFREQUENTLY produce vasoactive substances, are usually SMALL at the time of diagnosis, and have a comparatively GOOD prognosis.


(recognize difference between rectal carcinoid and proximal colon carcinoid presentation)

Front 27

T/F

Carcinoid tumors of the more proximal colon are quite uncommon, often present at high stage, and have a worse prognosis

Back 27

True

Front 28

Anorectal carcinoma

Back 28

usually arise near the dentate line

many types but most are squamous

adenocarcinoma is less common than distal spread of a more proximal colon cancer

melanomas can occur in anal skin

Front 29

Acute Appendicitis

Presentation

Back 29

Present with abdominal pain, vomiting, fever, leukocytosis (CLASSIC)

About half associated with obstruction (e.g., fecalith, parasites, lymphoid hyperplasia, tumor)

Complications include perforation and inflammation of the peritoneium (peritonitis)

Neutrophilic inflammation involving wall including muscularis propria

Front 30

What's the most common tumor in the appendix?

(EXAM)

Back 30

Carcinoid

Most common, usually incidental finding

Small tumors (< 2 cm) behave in a benign fashion

Can metastasize to lymph nodes, liver, ovary

Front 31

Mucinous
cystadenoma
of the appendix

(EXAM)

Back 31

These can burst and cause inflammatoin

Front 32

Tumors of the Appendix
Mucoceles are characterized by:

Back 32

a dilated mucus filled appendix.

they can be non-neoplastic and associated with obstruction.

others are associated with cystic mucinous tumors (cystadenomas or cystadenocarcinomas).

ural invasion with rupture can lead to diffuse peritoneal involvement (so-called pseudomyxoma peritonii)