Colon

Question 1

Causes of Constipation

Answer 1

• drugs: opioids
• mechanical
• metabolic: DM
• myopathy: amyloid, scleroderma
• neurogenic: PD, hirschsprung’s

Question 2

Sitz Marker

Answer 2

• radioopaque markers given on day 1
• abd x ray on day 5
• 5 sugges recto-sigmoid defacatory disorder
• > 5 scattered throughout colon= slow transit

Question 3

Hirschsprungs Disease

Answer 3

• congenital absence of myenteric neurons of the distal colon
• no reflex inhibition of the IAS following rectal distension (no recto-anal inhibitory reflex)

Question 4

Pelvic Floor Dysfunction

Answer 4

• inability to coordinate the abdominal, rectoanal and pelvic floor muscles during defication
• paradoxical contraction of the pelvic floor and external anal sphincters (dyssynergia)
• causes: bad toilet habits, painful defication, obstetric or back injury, brain gut dysfunction
• dx: abnormal anorectal manometry
• tx: biofeedback therapy

Question 5

Taenia Coli

Answer 5

-folds in large intestine

Question 6

Semilunar Folds

Answer 6

-inc. space in large intestine

Question 7

Haustra

Answer 7

-focused points of feces

Question 8

Two Types of Motility

Answer 8

• haustration- muscles of the colon wall are contracted intermittently to divide the colon into functional segments
• mass movement- strong peristaltic waves 1-3x/day
• no MMC

Question 9

Evacuation

Answer 9

• filling of rectum causes relaxation of internal anal sphincter via VIP and NO from intrinsic nerves
• external anal sphincter contracts (rectoanal inhibitory reflex)
• defecation occurs when external anal sphincter is voluntarily relaxed

Question 10

Two Types of Diarrhea

Answer 10

• osmotic diarrhea

- secretory diarrhea

Question 11

Osmotic Diarrhea

Answer 11

• lactase deficiency
• ileal resection
• celiac disease

Question 12

Secretory Diarrhea

Answer 12

• ex. cholera

- inc. cAMP levels in cells-> activates CF chloride channel on luminal surface

Question 13

Oral Rehydration Therapy

Answer 13

• antibiotics + KHCO3 to prevent hypokalemia and metabolic acidosis
• glucose with NaCl to facilitate the absorption of electrolytes and water

Question 14

Colorectal Cancer

Answer 14

• one of top 3 most common cancers in US
• mutations in APC (Wnt pathway) occur at high percentages (>80%) in both familial (FAP) and sporadic
• molecular pathways: RAS/MAP kinase, RAS/PI3 kinase, mismatch DNA repair, microsatellite instability

Question 15

Peutz-Jeghers Polyps

Answer 15

• hamartomatous
• can occur anywhere along GI tract
• pts are at inc. risk of pancreas and breast cancer
• polyps are usually pedunculated

Question 16

Necrotizing Enterocolitis

Answer 16

• presents with abdominal distension and bloody stools
• affects premature infants primarily
• bowel ischemia is predisposing factor
• can require surgical resection as therapy

Question 17

Microscopic Colitis

Answer 17

• inflammation of colon -> watery diarrhea or cramping
• type of IBD
• common in elderly females
• autoimmune
• histologic patterns: lymphocytic and collagenous colitis

Question 18

Hamartomatous Polyps

Answer 18

• most occur in childhood
• develop where normally present
• benign
• may portend risk of future GI carcinoma

Question 19

Serrated Polyps

Answer 19

• no premalignant: hyperplastic polyps

- premalignant: sessile serrated polyps/adenoma

Question 20

Hereditary Non-Polyposis Colorectal Cancer (Lynch Syndrome)

Answer 20

• develop colon cancer at earlier age than sporadic forms
• tend to be R sided
• inherit mutation of mismatch repair gene