Constipation Flashcards
What are 3 anatomic locations of the rectal area and what are their innervations?
Internal anal sphincter - L1-L2 symptoms, S2-4 PS
External anal sphincter - S2-4 (pudendal)
Puborectalis- S2-4 (pudendal, perineal)
Define constipation according to the Rome IV criteria?
Symptoms for 6+ mos and 2+ of following for >25% defecations during last 3 months:
1. Straining
2. Lumpy or hard stools
3. Sensation of incomplete evacuation
4. Sensation of anorectal obstruction/blockade
5. Manual maneuvers to facilitate defecation
6. <3 BM per week
7. Loose stools not present, insufficient criteria for IBS
What are 5 non GI causes of stool impaction?
- Medication side effects
- Neurogenic (spinal cord injury, Parkinson’s)
- Metabolic (hypothyroid, DM)
- Psychiatric
- Pelvic floor dysfunction
What is the ddx for causes of constipation?
Primary
- Normal transit
- Slow transit
- Dyssynergic defecation
Secondary
- Medications
- Neurologic disease
- Psychiatric disease
- Neoplastic
- Metabolic
- Diet (fibre, fluids)
- Immobility
- Mechanical obstruction
Outline an approach to diagnosis and management of constipation
- Hx
- Physical including DRE
- Investigations
Blood - Ca, TSH
Imaging - AXR
Scope not recommended unless red flag sx (blood, weight loss, anemia, fam hx, refractory) - Non pharm interventions (diet, exercise, behaviours, biofeedback)
- Pharm
- Re evaluate
List medications that can contribute to constipation
Supplements (Ca, iron)
Opioids - hydromorphone
NSAID - ibuprofen, naproxen
Antipsychotics - risperidone
TCA - amitriptyline
SSRI - paroxetine
Diuretics - furosemide
Non DHP CCB - diltiazem, verapamil
List disease processes that are associated with constipation (9)
- Diabetes
- Depression
- Dementia
- Parkinson’s
- MS
- Stroke
- Spinal cord injury
- HyperCa
- HypoTSH
What is an evidence based non pharmacologic therapy for constipation? Others maybe without evidence?
Biofeedback
Others:
1. Inc fluid intake
2. Inc exercise and mobility
3. Timed toileting (30 mins post)
4. Inc daily fiber 20-25 g/d
5. Stop aggravating meds
What are 6 steps in management of constipation per CMAJ 2013 article?
- Determine predominant symptoms (frequency, straining, incomplete)
- Identify possible secondary causes (meds, disease)
- Consider fecal impaction (AXR, DRE, manual disimpaction)
- Optimize behavioural factors (seated, knees above hips, toilet after AM meal, inc fluid, exercise)
- Trial dietary modifications for 2-4 weeks (fibre 20-30 g/d, not if immobile or bed bound)
- Trial previously preferred laxative 2-4 wks
- Trail laxative from RCTs 2-4 wks (PEG, lactulose)
- Trial of another laxative or combo 2-4 wks (magnesium hydroxide, docusate, bisacodyl, Senna, enema)
- Consider referral to geri or GI
What are bulk forming agents used to treat constipation?
Psyllium seed
Methylcellulose
Wheat dextrin
What are examples of osmotic laxatives?
PEG
Lactulose
Magnesium hydroxide
Sorbitol
What is this finding?
Fecal loading
What are steps in managing fecal impaction?
Complete obstruction
1. Manual disimpaction
2. Distal washout - docusate, sorbitol, mineral oil enema
Incomplete obstruction
1. Proximal softening - PEG
2. Distal washout
Management of constipation in Parkinson’s patient?
PEG
Probiotic/prebiotic fibre
Lubiprostone
Other: lactulose, psyllium, prucalopride, enema
What is the MOA of psyllium? AE? Onset?
Soluble fiber
Absorbs water in intestine to form viscous liquid
Promotes peristalsis and reduce transit time
AE: bloating, flatulence
Only if mobile
12-72 hours
What is the MOA of PEG? AE? Onset?
Non-absorbable, non-metabolized osmotic agent
Causes secretion of water into intestine
Improves transit and stool consistency
AE: bloating, pain, diarrhea
Onset: 1-4 days
What is the MOA of Senna?
Stimulant laxative
Stimulates peristalsis which increases motility, inc secretions
AE: cramps, hypoK, pseudomelanosis coli
Efficacy unknown
Onset: 6-12 hrs
What is the MOA of prucalopride?
5-HT4 receptor agonist
Selective, high affinity
Stimulates peristaltic reflex, intestinal secretions and motility
AE: pain, diarrhea, N/V, headache
Efficacy unknown
Onset: 3-12 hours
What is the MOA of linaclotide?
Non-absorbed selective GC-C receptor agonist
Promotes chloride rich intestinal secretions and laxation
AE: cramps, cost, diarrhea
Onset: 12-24 hours
What are the categories of laxatives?
- Bulking agents: psyllium, methylcellulose, polycarbophil
- Osmotic agents: PEG, lactulose, Mg hydroxide, sodium phosphate
- Stool softeners: docusate
- Stimulants: Senna, bisacodyl
- Prokinetics: prucalopride
- Secretagogue: linaclotide
- Enema/suppository: phosphate, tap water, glycerin supp
What is the MOA of docusate? AE?
Anionic surfactant decreases stool surface tension = inc water penetration
AE: cramps, diarrhea
Efficacy unknown
Onset: 24-72 hours
What is the MOA of enema/suppository? AE?
Distend rectum to initiate defecation reflex
Soften stool
Phosphate based can cause hyperphosphatemia and lytes
What are red flags about constipation making you concerned for cancer?
Acute onset
Unresponsive to tx
Positive FOBT
Hematochezia
Anemia
Weight loss 5 kg+ in 6 months
Fam hx colon ca
What are indications for AXR in constipation?
Empty rectum but suspect impaction
Persistent incontinence despite clearing impaction
Distention or pain
Persistent constipation with inc laxative use
