Flashcards in 29 - Diseases of the Colon and Rectum Deck (154)
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1
Colon & Rectum - Development
First trimester of gestation
Distal midgut (Cecum to splenic flexure) & hindgut (splenic flexure to rectum)
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Colon & rectum - Size
1m long
2L capacity
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Colon & Rectum - Regions
Cecum
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid Colon
Rectum
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Colon - 5 layers
Mucosa
Submucosa
Circular muscle
Longitudinal muscle
Serosa
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Colon - Haustra
Tonic contractions of rings of circular muscle (plicae semilunares coli)
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Colon - Circular muscle layer control
Thin layer of cells, interstitial cells of Cajal on submucosal surface of smooth muscle layer
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Colon & Rectum - Histo
Mucosa:
Columnar cells
Goblet cells
Enteroendocrine cells (mainly located in the crypts)
No Villi
Epithelial cells proliferate in lower parts of crypts, migrate toward surface
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Blood supply: Cecum, Ascending Colon, Transverse Colon
SMA
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Blood Supply: Transverse Colon, Descending Colon, Sigmoid Colon, Rectum
IMA
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Venous drainage
Analogous to arterial supply
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Colon - Neuronal supply
Intrinsic and extrinsic neurons
Extrinsic - Autonomic
Parasympathetic innervation supplied by vagal fibers (midgut derivatives) or the nerves of the pelvic plexus from sacral spinal cord (hindgut derivatives)
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Colon & Rectum purpose
Maintain fluid & electrolyte balance
Salvage products of intra-colonic fermentation
Store waste materials
Recover 1.5L fluid per day (mostly in proximal colon)
1 - 2 bowel movements/day
Can absorb sodium against high electrochemical gradient!
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Colon & Rectum - Pharmacology
Most drugs already absorbed by that point
EXCEPT Sulfasalazine (used to treat UC)
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Sulfasalazine
Composed of sulfapyridine (sulfonamide antibacterial) linked by a diazo bond with 5-Aminosalicylic acid (5-ASA, or mesalamine)
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5-ASA
The active therapeutic moiety of sulfasalazine.
The sulfapyridine just prevents 5-ASA from being absorbed earlier. The diazo bond is broken by bacterial action.
5-ASA decreases inflammation in the colon.
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Microbiome
10^10 organisms/mL
Represent a pool of metabolic enzymes
Anaerobes, can thrive in low-oxygen tension
Modify oxygen tension, pH, mucopolysaccharide composition & hydration capacity of stool solids.
Normal flora protects against pathogenic bacterial proliferation. Homeostasis between types of bacteria.
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Colon & Rectum - Vascular Diseases
Ischemic colitis
Diverticular bleeding
Hemorrhoidal bleeding
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Colon & Rectum - Neoplastic Diseases
Colon polyps
Colorectal cancer
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Colon & Rectum - Infectious Diseases
Appendecitis
Bacerial/Viral Colitis
Clostridium Difficile
Diverticulitis
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Colon & Rectum - Mechanical Diseases
Volvulus
Large bowel obstruction
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Colon & Rectum - Immunologic Diseases
IBD
Collageneous/Microscopic Colitis
Ileus
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Colon & Rectum - Motility Diseases
Ileus
IBD
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Ischemic Colitis - Presentation
Crampy, mild LLQ abdominal pain
Urge to defecate
Pass bright red (or maroon) blood mixed with stool
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Ischemic Colitis - Morphologic Changes
Vary with duration & severity of injury
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Ischemic Colitis - Watershed Areas
Splenic Flexure
Rectosigmoid
Due to limited collateral flow
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Ischemic Colitis - Mildest injuries
Reversible
Mucosal & submucosal hemorrhage & edema
with or without partial necrosis of the mucosa
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Ischemic Colitis - Unresorbed Hemorrhage
Overlying mucosa sloughs off, forming an ulcer.
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Ischemic Colitis - Prolonged Severe Ischemia
Muscularis propria is damaged, replaced with fibrous tissue.
Stricture.
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Ischemic Colitis - Most Severe
Trans-mural infarction
Gangrene
Perforation
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