constipation Flashcards
constipation
defined as less than 3 stools/wk
stools are infrequent and have difficult passage
different meanings for different individuals: ask about what it means to the pt. universally means unsatisfying defecation
physiology of colonic motility
phasic contractions: slow phasic contractions of circular and longitudinal muscles that result in haustration. controlled by myenteric plexus.
propulsive contractions: responsible for mass movement (high amplitude propogated contractions HAPC). occur 5-6X/day, esp in morning and after meals. controlled by autonomic nervous system
defecation: physiology
rectal distention, sensory of perception of stool, reflex relaxation of internal anal sphincter, contraction of the diaphragm, abdomen, and rectal muscles, voluntary relaxation of the external anal sphincter, and anorectal angle increases.
constipation types
Primary constipations: normal transit, slow transit, and defecation disorders
secondary constipation
normal transit constipation is a functional constipation that often responds to fiber and/or osmotic laxatives
secondary constipation may be due to meds, mechanical obstruction, endocrine or metabolic disorders, neuro disorders, enteric neuropathies, myogenic disorders, and anorectal disorders
Functional constipation
basically seen with IBS-C.
slow transit constipation
most common in young women with infrequent bowel movements (less than 1/wk). lack of urge to defecate, bloating, abdominal discomfort. this is due to reduced frequency of HAPC. decreased numbers of interstitial cells of cajal and myenteric plexus neruons expressing substance P (excitatory neurotransmitter). Tx: aggressive laxative regimens; maybe subtotal colectomy
defecation disorders
excessive straining, infrequent BMs, +/- need for manual maneuvers to move bowels. may be secondary to acquired/learned behaviors. may be associated with painful defecation, obstetric injury, back injury, brain/gud dysfunction, sexual or physical abuse, or eating disorders. OR, may be secondary to structural abnormalities (rectal intussusception/prolapse, rectocele, excessive perineal descent).
dyssnergic defecation
discoordination of abdominal, rectoanal, and pelvic floor muscles.
What are some red flag symptoms for a pt with constipation?
rectal bleeding, changes in the caliber of stool, weight loss, anemia, severe abdominal pain, strong family hx of colon cancer
What is one class of medications that might increase constipation?
opiates, calcium channel blockers
How should you evaluate a pt w/ constipation?
only CBC is necessary as long as there are no alarm signs or other symptoms
When do we use physiologic testing for constipation?
patients with refractory symptoms who do not have an identifiable secondary cause of constipation and in whom a trial of high fiber diet and laxatives has not been effective. may use colon transit studies or test of defecatory function
sitz marker study
normal colonic transit time should be less than 72 hrs. abdominal x-ray 120 hrs after the ingestion of radiopaque markes in a gelatin capsule. retention of more than 20% of markers at 120 hrs is indicative of prolonged colonic transit
if all in the rectosigmoid area, suugests defecation disorder. if dispersed throughout the colon, suggests slow transit
balloon explusion test
when rectum is distended with a balloon, the internal anal sphincter relaxes. inability to evacuate the balloon within 2 min indicates a defecatory disorder.
Normal/slow transit tx
high fiber diet and increased fluid intake/exercise stool softeners (low evidence) laxatives: bulk and osmotic laxatives safest for long term use. stimulant laxatives only ok for short term use. Chloride secretagogues (lubiprostone and linaclotide- increases cGMP and activates CFTR), surgery
