How do you assess constipation?

Assessment of Constipation: A Structured Clinical Approach

Definition

Constipation is diagnosed when a patient presents with at least two of the following symptoms for at least 12 weeks in the previous 12 months (Rome III Criteria): straining during bowel movements, lumpy or hard stool, sensation of incomplete evacuation, sensation of anorectal blockage or obstruction, manual evacuation procedures to remove stool, or fewer than 3 bowel movements per week. 1, 2

• Constipation is a symptom, not a disease, encompassing hard stools, incomplete evacuation, abdominal discomfort, bloating, distention, excessive straining, and need for manual evacuation—not merely infrequent bowel movements 3, 2
• Patients with daily bowel movements may still describe constipation, as reduced stool frequency correlates poorly with delayed colonic transit 3, 2

Classification

Primary Constipation Subtypes

• Normal Transit Constipation (NTC): Normal anorectal function and normal colonic transit (20-72 hours), often associated with irritable bowel syndrome features 2, 4
• Slow Transit Constipation (STC): Normal anorectal function but prolonged colonic transit due to reduced propulsive activity and increased uncoordinated distal colonic motor activity 2, 4
• Defecatory Disorders: Impaired rectal evacuation from inadequate propulsive forces and/or increased resistance, including high anal resting pressure, incomplete relaxation or paradoxical contraction of pelvic floor and external anal sphincters 2, 4
• Combination disorders: STC with defecatory disorders may coexist 2

Secondary Constipation

• Medications: Opioids (causing opioid-induced constipation per Rome IV criteria), anticholinergics, calcium channel blockers 2, 4
• Metabolic disturbances: Hypercalcemia, hypothyroidism, diabetes mellitus 3
• Neurologic disorders: Parkinsonism, spinal cord lesions 3
• Colonic diseases: Stricture, cancer, anal fissure, proctitis 3

Differential Diagnosis

• Irritable bowel syndrome with constipation (abdominal pain, bloating, malaise unrelated to defecation) 4
• Colorectal cancer or polyps (especially if alarm features present) 3
• Mechanical obstruction 3
• Opioid-induced constipation (distinct entity triggered or worsened by opioid analgesics) 1, 4
• Metabolic/endocrine disorders (hypothyroidism, hypercalcemia, diabetes) 3
• Neurologic conditions (spinal cord compression, Parkinson's disease) 3

History

Symptom Characterization

• Infrequency alone: Suggests NTC or STC 4
• Prolonged excessive straining with soft stools or inability to pass enema fluid: Strongly indicates defecatory disorders 4
• Need for perineal/vaginal pressure or digital evacuation: Even stronger indicator of defecatory disorders 4
• Abdominal pain, bloating, malaise unrelated to defecation: Suggests underlying irritable bowel syndrome 4

Red Flags (Alarm Features)

• Blood in stools 3
• Anemia 3, 4
• Unintentional weight loss 3, 4
• Sudden onset of constipation 3
• Age >50 years without prior colorectal cancer screening 3
• Symptoms suggesting spinal cord compression (requires full neurological examination including anal sphincter tone and rectal sensation) 3

Risk Factors and Contributing Elements

• Eating and drinking habits: Inadequate dietary fiber and fluid intake 3
• Medication use: Prescribed and over-the-counter medications 3
• Physical activity level: Relative to stage of illness 3
• Pre-existing conditions: Irritable bowel syndrome, diverticular disease 3
• Comorbid diseases: Heart failure, chronic pulmonary airway disease 3
• Environmental factors: Lack of privacy, assistance needed, bed-bound status 3

Physical Examination (Focused)

Digital Rectal Examination (DRE)

A careful digital rectal examination that includes assessment of pelvic floor motion during simulated evacuation should be performed before referral for anorectal manometry, though a normal examination does not exclude defecatory disorders. 3

• Assess resting tone of internal sphincter and augmentation during squeezing effort 3
• Evaluate puborectalis muscle contraction during squeeze 3
• Check for acute localized tenderness along puborectalis (levator ani syndrome) 3
• Instruct patient to "expel my finger" to assess expulsionary forces 3

Abdominal Examination

• Distension, abdominal masses, liver enlargement, tenderness 3
• Auscultation for increased/decreased bowel sounds 3

Perineal Inspection

• Skin tags, fissures, prolapse, anal warts, perianal ulceration, complete absence of stool, blood 3

DRE Findings

• Inner hemorrhoids, sphincter tone, tenderness, obstruction/stenosis, impacted feces, tumor masses 3

Investigations and Expected Findings

Initial Laboratory Tests

In the absence of other symptoms and signs, only a complete blood cell count is necessary. 3, 4

• Complete blood cell count: To detect anemia 3, 4
• Metabolic tests NOT routinely recommended: Glucose, calcium, thyroid-stimulating hormone should not be performed unless other clinical features warrant them 3, 4

Structural Evaluation

Colonoscopy should not be performed unless alarm features are present (blood in stools, anemia, weight loss) or age-appropriate colon cancer screening has not been performed. 3, 4

• Colonoscopy, computed tomographic colonography, or flexible sigmoidoscopy with barium enema to exclude lesions 3

Specialized Testing (For Refractory Cases)

Perform anorectal testing first (manometry and balloon expulsion test) to identify defecatory disorders. 4

• Anorectal manometry: Assesses anal sphincter pressures and rectal sensation 4
• Balloon expulsion test: Evaluates ability to expel rectal balloon 4
• Defecography: Visualizes anorectal structure and function during defecation 4

Evaluate colonic transit only if anorectal tests do not show defecatory disorder or if symptoms persist despite treatment of defecatory disorder. 3, 4

• Radiopaque marker test: Assesses colonic transit time 5
• Wireless motility capsule: Measures transit through entire GI tract 5
• Scintigraphy or colonic manometry: For detailed colonic motility assessment 5

Empiric Treatment

First-Line Interventions

• Discontinue constipating medications if feasible before further testing 3
• Increase dietary fiber and fluid intake to improve colonic transit 2
• Encourage regular physical activity 2

Pharmacological Therapy

Osmotic laxatives, particularly polyethylene glycol (PEG), should be offered as first-line pharmacological treatment. 2, 6

• Polyethylene glycol 3350: 17 grams daily dissolved in 4-8 oz of water, juice, soda, coffee, or tea; first bowel movement typically occurs in 2-4 days; use for 1-2 weeks 6
• Stimulant laxatives (bisacodyl or senna): Can be used to achieve one non-forced bowel movement every 1-2 days, generally reserved for PRN use 2, 7

Specialized Treatments

• Pelvic floor therapy/biofeedback: Should be offered to patients with evidence of defecatory disorders 2, 8
• Intestinal secretagogues and prokinetic agents: For patients not responding to laxatives 8, 9
• Peripherally acting μ-opiate antagonists: Specifically for opioid-induced constipation 8, 9

Indications to Refer

• Failure to respond to over-the-counter laxatives and fiber supplementation after 1-2 weeks 3, 6
• Suspected defecatory disorder based on history (prolonged straining with soft stools, need for digital evacuation) or abnormal DRE 3, 4
• Alarm features present: Blood in stools, anemia, unintentional weight loss, sudden onset 3
• Need for specialized testing: Anorectal manometry, balloon expulsion test, colonic transit studies 3, 4
• Consideration for surgical intervention: Medically refractory slow-transit constipation after extensive preoperative assessment 8, 10

Critical Pitfalls

• Assuming infrequent bowel movements define constipation: Patients with daily bowel movements may still have constipation; focus on the full symptom complex 3, 2
• Performing colonoscopy without alarm features: This is not indicated unless age-appropriate screening is due 3, 4
• Ordering routine metabolic panels: Thyroid, calcium, and glucose testing are not recommended unless clinically indicated 3, 4
• Skipping digital rectal examination: A normal DRE does not exclude defecatory disorders, but performing DRE with assessment of pelvic floor motion is essential before referral 3
• Evaluating colonic transit before anorectal function: Always assess for defecatory disorders first, as this changes management 3, 4
• Prolonged use of PEG without reassessment: PEG is intended for 1-2 weeks; prolonged use may result in electrolyte imbalance and laxative dependence 6
• Missing opioid-induced constipation: This is a distinct entity requiring specific management with peripherally acting μ-opiate antagonists 1, 4, 8
• Failing to assess for spinal cord compression: In suspected cases, perform full neurological examination including anal sphincter tone (lax with colonic hypotonia) and rectal sensation 3
• Not educating patients on lifestyle modifications: After successful treatment, discuss adequate dietary fiber, fluid intake, and regular exercise to maintain bowel regularity 3, 6