Constipation, Hirschprung, Megacolon Flashcards
Definition of constipation:
Infrequent BM <3/wk for 12 mo AND at least 25% of time: straining feeling of incomplete evacuation hard stool
In normal colon, motor function depends on contraction of
circular layer of smooth muscle
3 patterns of contractions:
short duration
long duration
giant migrating complexes
How are short duration colonic contractions characterized?
stationary motor contr, present over short areas of colon + persisting for <15s
What is the physiologic function of short duration colonic contractions?
mixing of fecal material and extraction of water
How are long duration colonic contractions characterized?
stationary or propagating (short distances) contractions, which may travel in orad or aboral direction
What is the physiologic function of long duration colonic contractions?
Assists in mixing and local propulsion of feces
long duration colonic contractions cause migration towards:
rectum in distal colon
How are giant migrating complexes of the colon characterized?
aboral propagating over extended distances
What is the physiologic purpose of giant migrating complexes of the colon?
causes mass movement of feces
Giant migrating complexes of the colon normally occur ____ (how freq?), and may be precipitated by:
1-2 times per day
colonic distention
How does food affect colonic motility?
causes increased segmental activity
Gastro-colic reflux may be mediated by:
CCK
Motility in response to food intake is proportional to:
caloric content of meal
CCK causes:
increased frequency & amplitude of segmental contractions
PgF stimulates:
longitudinal muscle contraction
PgE inh:
circular muscle contraction
Serotonin mediates:
intestinal peristalsis
secretion in GI tract
modulation of pain perception
Serotonin is released by:
__% of serotonin is located in GIT
enterochromaffin cells
80
What do 5HT3-R antagonists treat?
IBS pain
functional dyspepsia
2 types of constipation?
functional
IBS-C
Constipation is more common in pts with:
little daily physical activity
low income
poor education
Constipation: Epidemiology
F>M
~65 y/o
Major causes of chronic constipation?
neuropathic disorders IBS-C drugs pregnancy hyper/hypo-Ca hypothyroidism idiopathic
Drugs associated with constipation?
analgesics anticholinergics Fe-supplements Cation-containing (Al) CCB neurally-active
What lifestyle characteristics cause constipation in elderly?
dehydration
low calorie diet
low fiber diet
immobility
Constipation: Pediatric Etiology
95% functional
5% organic (which includes lead intoxication)
Functional constipation:
Epidemiology?
Symptoms?
infants + pre-school age
2wks pebble-like, hard stools
Functional fecal retention:
Epidemiology?
Etiology?
common cause of chronic constipation infancy to 16 years old
fear and toilet refusal
What should you rule out when diagnosing constipation?
thyroid disorders or electrolytes problem
What tests would you perform to dx constipation?
Colonoscopy or Barium Enema
Colon transit of markers
Anorectum Manometry
Which patients with constipation should you get lab data for?
rectal bleeding wt loss of ≥10 pounds family hx of colon CA or IBD anemia (+) fecal occult blood
What labs should you perform for constipation?
CBC glu creatinine Ca TSH
Plain films of the abdomen help in the diagnosis of:
Megacolon
Impaction
Colon Transit Study:
Methods?
Normal results?
methods: take Sitzmarks capsule, check Xray on day 5
normal: >80% ring markers passed by day 5
Severe Idiopathic Chronic Constipation more commonly affects (M, F)
F
Severe Idiopathic Chronic Constipation:
Symptoms?
infrequent defecation, excessive straining when defecating, or both
Sitz marker study:
Colonic inertia results?
delayed passage of marker through proximal colon
no increase in motor activity after meals or with laxatives
Sitz marker study:
Outlet delay?
markers move normally through the colon but stagnate in rectum
(more common in pelvic floor dyssenergia)
How is the pelvic floor involved in normal defecation?
puborectalis, ext/int sphincter relax
increased intraabdominal pressure
inhibition of colonic segmenting activity
What causes dyssynergic defecation?
failure to relax or inappropriate contraction of the puborectalis and external anal sphincter muscles
abnormalities that can produce severe idiopathic chronic constipation:
Slow transit constipation
Dyssynergic defecation
Irritable bowel syndrome
What is Hirschsprung Disease?
Congenital disorder characterized by:
- -obstipation from birth
- -colonic dilatation proximal to a spastic, non-relaxing and nonpropulsive segment of distal bowel
Hirschsprung Disease/Congenital Aganglionic Megacolon
Epidemiology?
Males > female : 4:1
10% of cases in Down’s Syndrome
Most cases: sporadic, a few familial
Hirschsprung Disease/Congenital Aganglionic Megacolon
Pathogenesis?
Absence of ganglion cells in submucosa and musc wall of large bowel
Hirschsprung Disease/Congenital Aganglionic Megacolon is caused by what genetic defects?
Heterogeneous defects in genes regulating:
- migration + survival of neuroblasts
- neurogenesis
- receptor TK activity
What causes mortality in Hirschsprung Disease?
Superimposed enterocolitis with fluid and electrolyte disturbances
perforation with peritonitis
What parts of the bowel are involved in Hirschsprung Disease/Congenital Aganglionic Megacolon?
rectum
sigmoid (usually)
entire colon = rarely
What is the consequence of the abnormalities present in Hirschsprung Disease/Congenital Aganglionic Megacolon?
functional obstruction
progressive dilation and hypertrophy proximal to aganglionosis
later: massive distension outruns hypertrophy, wall becomes thinned + ruptures
Hirschsprung Disease/Congenital Aganglionic Megacolon:
Clinical presentation?
- -failure to pass meconium
- -obstructive constipation with occasional passage of stool
- -bouts of diarrhea + abdominal distention
Gold standard for Hirschsprung Disease/Congenital Aganglionic Megacolon diagnosis?
rectal biopsy showing absence of ganglionic cells
Treatment of Hirschsprung Disease/Congenital Aganglionic Megacolon?
Surgical resection of the aganglionic segment of bowel
Sphincter function is generally preserved
Acquired Megacolon (“Toxic Megacolon”): Infectious causes?
Clostridium difficile pseudomembranous colitis
Chagas Disease: trypanosomes invade bowel wall and destroy enteric plexus
Acquired Megacolon (“Toxic Megacolon”): Non-Infectious causes?
Inflammatory bowel disease
Obstruction (tumor or inflammatory stricture)
Functional disorder associated with pyschiatric disease and medication
Can Acquired Megacolon be fatal?
YES!
Anorectal Malformations:
Epidemiology?
Treatment?
1:3000 live births
surgery
Anorectal Malformations:
Pathogenesis (3 possible)?
Failure of urorectal septum formation in cloaca (week 7)
failure of anal membrane opening (week 8)
malformations in urinary tract and/or trisomy 21
