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GI Topics > Diseases of the Bowel and Colon > Flashcards

Diseases of the Bowel and Colon Flashcards

1
Q

Mostly Crypts, but no villi; numerous goblet cells

  • (vs. small bowel: mostly villi)
A

Normal Colon Histology

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2
Q
  • Cecum
  • Ascending colon
  • Hepatic Flexure
  • Transverse colon
  • Splenic flexure
  • Descending colon
  • Sigmoid colon
  • Rectum
  • 3 layers of muscle in the muscularis externa
  • Vasa recta: blood vessels that traverse wall; potential areas of weakness in the wall
A

Colon Anatomy

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3
Q

Reabsorb fluids and electrolytes

A

Major task of colon

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4
Q
  • Celiac artery supplies the esophagus, stomach, liver, spleen, superior portion of duodenum and pancreas
  • Superior mesenteric artery supplies small bowel to the transverse colon
  • Inferior mesenteric artery supplies splenic flexure to upper rectum
A

GI tract arterial supply

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5
Q

Persistence of herniation of abdominal viscera (and occasionally liver) into base of umbilical cord → externalized abdominal contents enveloped in sac into which the umbilical cord inserts

A

Omphalocele

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6
Q
  1. Ileocecal artery (distal terminal ileum, cecum, appendix)
  2. Right colic artery (ascending colon; absent 2-18%)
  3. Middle colic (transverse colon)
A

Branches of Superior Mesenteric Artery

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7
Q
  • left colic artery
  • sigmoid branches
  • superior rectal artery
A

Branches of Inferior Mesenteric Artery

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8
Q
  • Arises from the inferior mesenteric artery
  • Supplies distal transverse colon, splenic flexure and descending colon
  • May form collaterals with the left branch of the middle colic artery (marginal artery)
A

Left Colic Artery

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9
Q
  1. Formed by anastamosis of ileocolic, right colic and middle colic arteries
  2. Completed by left colic artery
  3. Travels along mesenteric border of colon
  4. Serves as connection btw SMA and IMA circulation
  5. Small vasa recta arise from this vessel and directly supply colon wall
A

Marginal Artery

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10
Q
  1. connects proximal SMA and the proximal IMA
  2. Vital source of blood supply when occlusion of SMA or IMA
  3. Dilates in response to mesenteric occlusion
A

Arc of Riolan

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11
Q
  • vulnerability of splenic flexure region to ischemic injury in hypotension
  • splenic flexure has variable collateral circulation
  • located at confluence of blood supplies of midgut and hindgut
  • 50% of ppl no clearly identifiable arteries in “watershed” area: ppl rely upon vasa recta for blood supply in this area
A

“Watershed” Area

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12
Q
  • Branches of inferior mesenteric artery

- Branches of internal iliac artery

A

Arterial Supply of the Rectum

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13
Q
  • Right and proximal transverse colon drain into Superior Mesenteric Vein
  • Distal transverse, descending, and sigmoid colon and most of rectum drain into Inferior Mesenteric Vein
  • Anal canal venous drainage occurs via middle and inferior rectal veins into the IMV
A

Venous drainage of the colon

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14
Q

Acetylcholine

A

ENS Excitatory Motor Neuron Neurotransmitter

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15
Q
  • nitric oxide
  • ATP
  • vasoactive intestinal polypeptide
A

ENS Inhibitory Motor Neuron Neurotransmitter

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16
Q
  • Sensation of urge to defecate, even if the bowel is empty; occurs with inflammation of the rectum
A

Tenesmus

17
Q
  • Syndrome characterized by relapsing abdominal pain/discomfort (12 weeks of symptoms within 12 months)
  • Associated with change in stool frequency and/or consistency
  • Symptoms improve with defecation; dietary fibers may improve symptoms
  • Related to disturbed intestinal motility
  • NO IDENTIFIABLE PATHOLOGIC CHANGES
  • Middle-aged female predominance
A

Irritable Bowel Syndrome

18
Q
  • A false diverticulum, Involving herniation of only the mucosa and submucosa outward from the lumen (true diverticula involve the entire wall)
  • typically occur near vasa recta (areas of weakness)
  • Left-sided divertiula more common in West, right-sided predominance in East
  • is frequently asymptomatic
A

Colonic Diverticula/Diverticulosis

19
Q
  • Inflamed/infected diverticulum
  • Most common complication of diverticulosis - Likely to occur when inspissated stool in a diverticulum interferes with emptying, i.e., obstructing fecal material
  • Symptoms/signs: LLQ pain, fever, altered bowel habits, high WBC
  • More significant complications including abscess, free perforation, fistulization and peritonitis can occur
A

Diverticulitis

20
Q
  • Typically large volume painless bleeding (Hematochezia) in an older patient due to segmental weakening of the vasa recta as it courses over the diverticulum
A

Diverticular Hemorrhage

21
Q

Ischemic damage to the colon, usually athte splenic flexure (watershed area of the superior mesenteric artery)

  • Primarily a disease of the elderly (90% of cases in patients>60 years)
  • Atherosclerosis of SMA is the most common cause (most distal point of blood flow)
  • Presents with postprandial pain (after eating) and weight loss

Clinical features:

  • Sudden onset abdominal pain, usually LLQ
  • Urge to defecate
  • Passage of maroon stool
  • Pain and tenderness are usually mild to moderate

Dx:

  • Plain films may demonstrate “thumb-printing” (correlated to submucosal hemorrhage)
  • CT may reveal mural thickening
A

Ischemic Colitis

22
Q
  • Types: Viral (Rotavirus), Bacterial (E. coli, salmonella), Parasitic (giardia, ameba), Traveler’s diarrhea, Hospital acquired (Pseudomembranous colitis)
  • Dx: Stool testing

Risk factors:

  • recent antibiotic use (C. difficult invades after wiping out gut flora)
  • Underlying colonic disease (IBD)
  • Chronic enteral feeding
A

Infectious Colitis

23
Q

C. difficile infection after recent antibiotic use wipes out gut flora
- usually hospital-acquired colitis

A

Pseudomembranous colitis

24
Q
  • due to hyperplasia of glands
  • classically show a serrated appearance on microscopy
  • Benign, with no malignant potential
A

Hyperplastic polyps

25
Q
  • due to neoplastic proliferation of glands
  • benign, but premalignant
  • may progress to adenocarcinoma via the adenoma-carcinoma sequence
A

Adenomatous polyps

26
Q
  • APC (tumor suppressor gene) mutations increase risk for formation of polyp
  • K-ras mutation leads to formation of polyp (adenoma)
  • P53 mutation and increased expression of COX allows for progression to carcinoma
  • Aspirin impedes progression from adenoma to carcinoma
A

Adenoma-carcinoma sequence

27
Q
  • size
  • sessile growth (elevated, but flattened appearng)
  • Villous histology (vs. tubular)
A

Risk factors for progression from adenoma to carcinoma

28
Q

Clinical presentation:

  • Anemia: b/c of folate/B12 deficiency
  • Hematochezia
  • Abdominal pain
  • Mass
  • Change in bowel habits (diarrhea, constipation
  • Change in stool caliber

May arise from:

  • adenoma-carcinoma sequence
  • Microsatellite instability
A

Colorectal Carcinoma

29
Q
  • Microsatellites are repeating sequences of noncoding DNA; instability indicates defective DNA copy mechanisms
  • increases risk for colorectal, ovarian and endometrial carcinoma
  • colorectal carcinoma arises de novo via this mechanism
A

Microsatellite Instability

30
Q
  • usually grows as a napkin-ring lesion
  • usually via adenoma-carcinoma sequence
  • presents with LLQ pain & blood streaked stool
A

Left-sided colorectal carcinoma

31
Q
  • usually grows as a raised lesion
  • usually via microstatellite instability pathway
  • presents with iron-deficiency anemia due to occult bleeding, and vague pain
A

Right-sided colorectal carcinoma

GI Topics (17 decks)

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