Pathophysiology of Colon

Question 1

Signs/sx of Ulcerative Colitis vs. Crohn’s Disease

Answer 1

• Both UC & Crohn’s:
  
  • Diarrhea
  • Weight loss
  • fatigue
• UC:
  
  • lower abd pain
  • hematochezia (blood in stool)
  • mucous in stool
  • tenesmus (feeling of incomplete defecation)
• Crohn’s
  
  • mid or lower abd pain
  • nausea/vomiting
  • fistula sx

Question 2

Macroscopic features: Crohn’s vs. UC

Answer 2

• Bowel region
  
  • Crohn’s: Entire GI tract
  • UC: Colon
• Fistulae or abscess
  
  • Crohn’s: Yes
  • UC: No
• Strictures
  
  • Crohn’s: Common
  • UC: No
• Distribution
  
  • Crohn’s: “Skip lesions”
  • UC: Diffuse

Question 3

Pathologic/microscopic features: Crohn’s vs. UC

Answer 3

• Inflammation
  
  • Crohn’s: Transmural
  • UC: Mucosa +/- SM
• Ulcers
  
  • Crohn’s: Deep, linear
  • UC: Superficial, confluent
• Fibrosis
  
  • Crohn’s: Marked
  • UC: Mild to none
• Granulomas
  
  • Crohn’s: Yes - ~ 20%
  • UC: No

Question 4

Other/associated features: Crohn’s vs. UC

Answer 4

• Obstruction
  
  • Crohn’s: Yes
  • UC: No
• Malabsorption
  
  • Crohn’s: Yes
  • UC: No
• Malignant potential
  
  • Crohn’s: With colonic involvement
  • UC: Yes
• Recurrence after colectomy
  
  • Crohn’s: Common
  • UC: No
• Toxic megacolon
  
  • Crohn’s: No
  • UC: Yes

Question 5

Major types of colitis

Answer 5

• microscopic colitis
• ischemic colitis
• infectious colitis
• drug-induced colitis
• radiation colitis

Question 6

Characteristics of microscopic colitis

Answer 6

• subtypes:
  
  • lymphocytic
    
    • lymph infiltration of mucosa/SM
  • collagenous
    
    • thickened collagenous band
• mild association w/celiac disease
• good prognosis

Question 7

Characteristics of ischemic colitis

Answer 7

• elderly pt.s, often w/out vascular or GI disease
• triggers:
  
  • vasospasm
  • dehydration, hypotension, cardiopulmonary insult
• commonly @ “watershed” vascular areas
  
  • splenic flexure
  • rectosigmoid

Question 8

Clinical presentation of ischemic colitis

Answer 8

• = Abrupt-onset, crampy, lower abdominal pain
• Urgent need to defecate
• Mild diarrhea and/or hematochezia
  
  • Severe diarrhea or bleeding suggests another diagnosis
• Endoscopic findings:
  
  • edema
  • ulceration
  • +/- bleeding confined to a vascular region

Question 9

Characteristics of infectious colitis

Answer 9

• Inflammatory diarrhea +/- hematochezia
  
  • Mucosal invasion
  • Toxin-related injury
• Hx:
  
  • short duration
  • travel
  • ill contacts/exposures
  • antibiotic use

Question 10

Exposures ==> infectious colitis

Answer 10

• Undercooked beef
  
  • E. Coli
• Contaminated poultry, eggs, milk, lettuce
  
  • Salmonella/Shigella, Campylobacter, Yersinia
• Antibiotic use, hospitalization
  
  • C. Difficile
• Anal intercourse
  
  • Venereal proctitis

Question 11

Characteristics of diverticulosis (general)

Answer 11

• outpouchings of colon wall
  
  • composed of mucosa and submucosal layer through muscularis propria
  • contain by serosa
• diverticula form and grow
• common in western countries
  
  • low-fiber diet = risk factor
• benign condition in most (80%) of pts
• complications (20-25%)
  
  • infection
  • perforation
  • abscess formation
  • hemorrhage

Question 12

Causes of acute diverticulutis

Answer 12

• large stool or food particle lodges @ diverticulum ==> impacted @ diverticulum
• if impaction is not relieved ==> bacteria multiply, expand, form gas ==> rupture of diverticulum

Question 13

Types & sx of acute diverticulutis

Answer 13

• uncomplicated
  
  • abscess contained @ colon wall
• complicated
  
  • free perforation
  • large abscess
  • bowel obstruction
• sigmoid diverticula = most common
• sx:
  
  • LLQ pain
  • fever
  • nausea/vomiting

Question 14

Characteristics of complications of diverticular disease

Answer 14

• large abscess formation
• perforation ==> peritonitis
• diverticular hemorrhage
  
  • mucosa of diverticulum erodes into penetrating vasa recta ==> intraluminal bleeding

Question 15

General characteristics of lower GI bleeding

Answer 15

• Bleeding distal to ligament of Treitz
• Colonic bleeding >>> small bowel bleeding
• Usually presents as hematochezia = blood in stool
  
  • Less commonly, melena

Question 16

Common etiologies of LGIB

Answer 16

• •Diverticulosis
• •Arteriovenous malformations
• •Colitis
• •Neoplasm
• •Radiation colitis
• •Post-polypectomy or biopsy
• •Miscellaneous
  
  • •Internal hemorrhoids
  • •Solitary rectal ulcer
  • •Anal fissure
  • •Dieulafoy’s lesions

Question 17

LGIB: DDx of Abdominal pain or diarrhea

Answer 17

• ischemic colitis
• IBD

Question 18

LGIB: DDx of weight loss, new constipation, anemia

Answer 18

• neoplasm

Question 19

• LGIB: DDx of
  
  • sudden onset heavy bleed + sudden cessation
  • eldery pt

Answer 19

• diverticulosis

Question 20

• LGIB: DDx of
  
  • acute dysentery
  • travel
  • ill contacts
  • antibiotic use

Answer 20

• infectious diarrhea

Question 21

LGIB: DDx of microcytic anemia

Answer 21

• neoplasm
• AVM (arteriovenous malformation)

Question 22

LGIB: DDx of NSAID use

Answer 22

• drug-induced colitis

Question 23

LGIB: DDx of hx of pelvic radiation

Answer 23

• XRT proctitis

Question 24

Causes & presentation/dx of colon obstruction

Answer 24

• Sx:
  
  • N/V
  • abd. distension
  • constipation or obstipation
• Dx:
  
  • Xray = tentative dx
  • CT confirms
• Causes
  
  • Malignancy
  • Benign – adhesions, strictures, volvulus
  • Foreign body – inserted or ingested

Question 25

Dx of lower GI bleed

Answer 25

• usually via colonoscopy