Small and Large Intestine

Question 1

Small Intestine

Answer 1

consists of three segments: the Duodenum, the Jejunum, and Ileum. It is the primary site of digestion and nutrient absorption. It’s surface area is greatly increased by its circular folds, villi and microvilli.

Question 2

Large Intestine

Answer 2

COLON. allows for the absorption of water and electrolytes.

Question 3

Haustra

Answer 3

folds of circular muscle creating sac like segments along the colon

Question 4

GALT

Answer 4

GI Associated Lymphoid Tissue.
Includes Kupfer cells (fixed macrophages in the liver.) From individual cells (intraepithelial lymphocytes) to large “clumps” of immune cells (Peyer’s patches in the ileum.) Plus all the lymph nodes outside the stomach, small & large intestine, etc. Reflects the fact that the gUT is the place we sense the world around us. THE STOMACH IS THE MOST COMMON “EXTRANODAL” SITE FOR LYMPHOMA.

Question 5

Diarrhea

Answer 5

a volume of greater than 150-200ml per 24 hours. Osmotic diarrhea occurs when carbohydrates (lactose, sorbitol) or minerals (such as magnesium citrate) create an osmolar gap. Water follows into the lumen to reduce this situation. Secretory diarrhea may be secondary to toxins from infectious bacteria (Yersinia, CAMPYLOBACTER JEJUNII, Shigella, Salmonella) or gut hormones.

Question 6

Constipation

Answer 6

a problem of the large intestine. the causes of decreased stool frequency or increased consistency are many including structural (tumor, adhesion), hormonal (hypothyroidism, diabetes), neurologic (Hirschsprung disease) and more. THE MOST COMMON CAUSE IN THE WESTERN WORLD IS POOR DIETARY FIBER INTAKE.

Question 7

Inflammatory Bowel Disease (IBD)

Answer 7

a chronic inflammation of the bowel and often has a pattern of familial occurrence. There may be many manifestations of IBD in systems outside of the GI tract.

Question 8

Causes of IBD

Answer 8

Genetic susceptibility
Immune dysregulation
Environmental triggers

Question 9

The hygiene Hypothesis

Answer 9

People in areas endemic for intestinal helminths and other intestinal pathogens are less likely to get IBD.

Question 10

Inflammatory bowel diseases

Answer 10

ulcerative colitis and ulcerative proctitis
Crohn’s disease
Genetic, inflammatory, environmental

Question 11

ulcerative colitis

Answer 11

chronic ulcerative colitis most commonly develops in young adults. peaking in incidence in the 3rd decade.

UC is a disease of the lining or MUCOSA of the colon. it may involve the entire organ (pancolitis) or be limited to the distal aspect (left sided colitis). a subset of patients have involvement of the rectum alone and never progress further (ulcerative proctitis).

Question 12

symptoms of ulcerative colitis

Answer 12

diarrhea
bleeding
urgency
pain with defecation (tenesmus)
c
the characteristic microscopic finding in UC is the CRYPT ABSCESS. over time, raised islands of normal mucosa form and are known as pseudopolyps.
severe, long standing (> 15 yrs) IC are at a significant risk for developing colon cancer.
Extracolonic manifestations, co-exist problems, ex. arthritis, skin lesions etc.
therapy: colectomy

Question 13

Crohn’s disease CD

Answer 13

most often arises in adolescents and young adults. it may be seen in family clusters. rising.
it may involve any part of the digestive tract from mouth to anus. it is most often seen in the terminal ileum and right side of the colon (45%). about 1 in 5 cases involves the colon alone.

Question 14

Presentations of CD

Answer 14

is a process that is TRANSMURAL, involving the full thickness of the bowel wall in contrast to ulcerative colitis.

ileal involvement
*strictures*
*fistulas*
*transmural involvement* 
granulomas
linear clefts

Clinical presentations: fever, abdominal pain, and diarrhea. early symptom is quite non specific.
the risk of colon can ver is increased with crohn’s disease

Question 15

Treatment of CD

Answer 15

no curable treatment
steroids. sulfasalazine and immunosuppressives such as azathioprine may be used. surgery is often helpful but mostly have recurrence.

Question 16

Colon

Answer 16

..

Question 17

Diverticulosis

Answer 17

mucosal outpouchings of the lining of the large bowel (technically pseudodiverticula).
caused in part by low dietary fiber and the higher pressures the colon makes to propel stool forward.
acquired herniation of mucosa/submucosa through the muscular of the colon.
striking greographic variation: common in the West, unusual in Africa, Asia.
More common in higher SES groups
Age: 10% of adult population in U.S.
1/3 to 1/2 by age 60.
stool balls in the side pockets of the colon……low grade infection of even small perforations with subsequent abscess formation. chronic infections can lead to scarring and strictures.

Question 18

Clinical aspects of diverticulosis

Answer 18

80% no symptom.
bleeding.
the other common cause of lower GI bleeding is from ANGIODYSPLASIA also known as vascular ectasia

Question 19

complication–infection–diverticulitis

Answer 19

fecalith -- inspissated stool in a pocket.
   cause low grade inflammation
   leads to micro-perforation
Typical symptoms
   left lower quadrant pain
Increased WBC
Generalized peritonitis
abscess

Question 20

Diverticulitis treatment

Answer 20

clear liquids
low fiber diet (during an episode)]
antibiotics: metronidazole/ciprofolxacin

Question 21

colon cancer

Answer 21

the second most common cause of cancer in men and (third most common cause in) women in the Western world.

Question 22

Presentation of colon cancer

Answer 22

early (curable) colon cancer has NO SYMPTOMS
It’s COMMON ==> screen it early

may cause very subtle, hidden (occult) bleeding and sreening for this with stool guiaic (hemoccult) cards should be performed yearly after age 50.
gross bleeding, obstruction, perforation, or a fistula.

Question 23

risk factors for colon cancer

Answer 23

age
diet and geography
family history
chronic colitis
adenoma
previous colorectal neoplastia

Question 24

adenoma – carcinoma sequence

Answer 24

normal mucosa –> adenoma –> severe dysplasia –> cancer

Question 25

polyp

Answer 25

a mass that protrudes into the lumen of the gut. most commonly in colon. not all polyps have the potential of becoming a malignancy. 
examples: hyperplastic, juvenile (hamartomatous), inflammatory, and lymphoid polyps. 
adenomatous polyps (adenomas) can progress to adenocarcinoma.

Question 26

Screening for colon cancer

Answer 26

colonoscopy: sensitive, specific, allows for therapeuties, expensive, requires sedation.
virtual colonography (CT colonography)
Stool genetic analysis (cologuard)

Question 27

family adenomatous polyposis FAP

Answer 27

the autosomal dominant gene, adenomatous polyposis coli (APC) is due to a specific genetic defect found on chromosome 5. The gene has been identified and blood samples can be screened for it. Thousands of polyps develop in the colon and colon cancer is inevitable by age 40. Polyps also develop in the stomach and small bowel.

Question 28

Hereditary non-polyposis colon cancer

Answer 28

refers to patients with relatively small numbers of polyps but clustering of colon, pancreas, ovary, and uterus cancers. It is a defect in the mis-match repair gene and it allows for mistakes to happen during replication of the DNA.