Constipation and Megacolon Flashcards
Definition of constipation
Less than 2 BM/week for 12 months
or
less than 3 per week for 12 mths with straining/hard stool over 25% of the time
Normal motility in the colon depends on what
Smooth muscle contraction (circular layers)
Less longitudinal contraction in the colon
Short duration colonic contractions cause
mixing
less than 15 seconds
Long duration
mixing and local propulsion
What type of colonic movement causes mass movement of feces?
Giant migrating complex
Food instigates a gastrocolic reflex to make room for more food. This is mediated by
CCK
Gastrocolic reflex is proportional to qhat?
Caloric content of meal
CCK and colonic contractions
CCK stimulates frequency and amplitude of contractions
Pg F stimulates
Longitudinal muscle contraction
PgE does what
inhibits circular muscle contraction
Serotonin does what?
mediates intestinal peristalsis
What is the most important neurotransmitter in the brain gut interaction>
Serotonin
Serotonin released by what types of cells
Enterochromaffin cells
80% of total body serotonin is present where?
GI tract
Constipation more common in pts that are 65 or older and esp in women
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When investigating the causes of Constipation realize that primary causes are generally rare (except IBS). Secondary causes shuld usually be investigated first…
Think about:
- Drugs
Think about neurogenic vs. non-neurogenic causes
KNOW Etiology stuff
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95% of pediatric c0onstipation is
functional…they don’t want to use the bathroom at school or something
Complains of constipation but transit study is normal. This IBS
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Severe idiopathic chronic constipation is most common in who?
Women
Sitz marker study investigates
normal colonic transit
Puborectalis muscle does what during defecation
relaxes
Normal defecation is associated with relaxation of teh puborectalis and external anal sphincter muscles, together with increased abdominal pressure and inhibition of colonic segmenting activity
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Dyssynergic defecation
Ineffective defecation is associated with a failure to relax, or inappropriate contraction of, the puborectalis and external anal sphincter muscles
Hirchsprung Disease
Congenital disorder characterized by constipation from birth and colonic dilatation proximal to a spastic, non-relaxing and non-propulsive segment of distal bowel.
Epidemiology of Hirchsprung
More common in males (4:1)
10% of cases in Down Syndrome
Pathogenesis of Hirchsprung
Absence of ganglion cells in large bowel, functinal obstruction and proximal dilatation
Rectum is always involved, rectum and sigmoid in most cases, very rare for the entire colon to be involved
Clinical presentation of Hirchsprung disease
- failure to pass meconium
- obstructive constipation, occasional passage of stool
- bouts of diarrhea, abdominal distension
Gold standard for diagnosis of Hirchsprung
Rectal biopsy
May also do abdominal radiographs, contrast enema,anorectal manometry, etc
Differential for megacolon
- Rule out obstruction
- C. Dif Colitis
- IBD due to ulcerative colitis or Crohn’s disease
- Adynamic colon….very common, must rule out the others first though
