Show notes
Episode one of the Pelvic Floor and Anorectal Disorders chapter works through chronic constipation as a symptom-defined syndrome, the empiric laxative sequence that resolves most patients, and the prescription drugs for refractory disease mapped to four molecular targets. The organizing idea: match the drug to the mechanism, and keep opioid-induced constipation separate because the enteric receptor never develops tolerance. Definitions, alarm features, secondary causes, secretagogues, prucalopride, and the peripherally acting opioid antagonists throughout, all framed around the exam stem that names the mechanism.
Topics covered
Symptom-defined diagnosis of chronic constipation
Three mechanistic subtypes: normal-transit, slow-transit, defecatory
Alarm features and secondary causes
Empiric sequence: diet, fiber, osmotic, stimulant laxatives
Prescription secretagogues and their four targets
Prucalopride as the serotonin-4 prokinetic
Opioid-induced constipation and tolerance asymmetry
Peripherally acting opioid antagonists and the obstruction contraindication
Key decisions
Chronic constipation is diagnosed on symptoms over at least three months, not stool frequency alone; infrequent movements without straining, hard stools, or incomplete evacuation is bowel-frequency variation and gets reassurance, not a secretagogue.
Alarm features (new symptoms over age fifty, weight loss, bleeding or iron-deficiency anemia, family history of colorectal cancer or IBD) send the patient to colonoscopy now instead of empiric polyethylene glycol.
The empiric sequence is education and diet, soluble fiber titrated toward twenty-five to thirty grams a day with psyllium preferred, polyethylene glycol seventeen grams daily first-line, then bisacodyl or senna, run over four to eight weeks.
Lubiprostone is dosed at twenty-four micrograms twice daily for chronic constipation versus eight micrograms twice daily for IBS-C; linaclotide is one hundred forty-five micrograms daily versus two hundred ninety for IBS-C on an empty stomach.
Prucalopride is the two-milligram serotonin-4 prokinetic and the natural next step when secretagogues fail, because the deficit is slow propulsion; unlike the withdrawn earlier agents it was designed for selectivity and spares the cardiac targets.
Opioid-induced constipation needs standard stimulant-plus-osmotic laxatives first; when they fail, a peripherally acting antagonist (naloxegol, methylnaltrexone, naldemedine) is added, contraindicated in known or suspected mechanical GI obstruction.
Alvimopan is for postoperative ileus only under a short-term inpatient program, not chronic opioid constipation, and lubiprostone is an opioid-independent non-antagonist option when an antagonist isn't tolerated.
For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com.
Questions or feedback: [email protected].
(00:00) - Introduction and the organizing idea
(00:30) - Constipation is symptom-defined, not frequency
(01:59) - Three mechanistic subtypes
(03:08) - Alarm features and secondary causes
(05:35) - The empiric laxative sequence
(07:52) - Prescription secretagogues and their targets
(10:05) - Prucalopride the prokinetic
(11:44) - Opioid-induced constipation and tolerance
(13:10) - Peripherally acting antagonists and contraindications