What are the causes and treatment options for chronic constipation in individuals, particularly the elderly and those with underlying medical conditions such as hypothyroidism, diabetes, and neurological disorders?

Causes of Chronic Constipation

Primary Etiologic Categories

Chronic constipation in elderly patients and those with underlying medical conditions results from four main mechanisms: age-related physiologic changes, medication effects, metabolic/endocrine disorders, and neurological dysfunction. 1

Age-Related Physiologic Changes

• Degenerative changes in the enteric nervous system occur with aging, causing disrupted colonic motility, diminished rectal distension perception, and rectal sphincter dysfunction. 1
• Rectal hyposensitivity develops in elderly patients, requiring greater stool volumes to trigger the defecation reflex. 2
• The prevalence escalates dramatically with age: 24-50% in community-dwelling elderly and up to 74% laxative use in nursing home residents. 1

Medication-Induced Constipation

Obtain a complete medication list as the first diagnostic step, as medications are the most modifiable cause. 3, 1

• Opioid analgesics are the single most critical medication cause, producing constipation without tolerance development over time. 1
• Psychotropic medications (antidepressants, antipsychotics, benzodiazepines) commonly prescribed in institutionalized elderly patients cause chronic constipation. 1
• Anticholinergic medications, calcium channel blockers, and iron supplements contribute significantly. 2
• Withdrawal of inappropriate or unnecessary constipating medications is the most important initial intervention. 3, 1

Metabolic and Endocrine Disorders

Check corrected calcium levels and thyroid function when constipation is identified clinically. 3

• Hypothyroidism is the most common systemic disease causing constipation and must be excluded. 4
• Hypercalcemia, hypokalemia, and uremia all disrupt colonic motility and should be checked when clinically suspected. 3, 1
• Diabetes mellitus causes constipation through autonomic neuropathy affecting colonic transit and rectal sensation. 2

Neurological Disorders

• Neurological conditions cause constipation through disruption of the enteric nervous system, autonomic dysfunction, and impaired rectal sensation. 2
• Parkinson's disease, multiple sclerosis, spinal cord injury, and stroke all directly impair colonic motility and defecatory function. 2
• Abdominal massage can be particularly efficacious in reducing gastrointestinal symptoms in patients with concomitant neurogenic problems. 3

Functional and Lifestyle Factors

Physical Inactivity and Mobility Limitations

• Decreased mobility and physical activity resulting from chronic diseases contribute substantially to constipation prevalence in older adults. 5
• Even minimal activity increases (bed-to-chair transfers) can improve bowel function within patient limits. 3

Dietary Factors

• Inadequate fluid intake (below 1.5 liters daily) and low-fiber diet worsen stool consistency and transit. 1
• Decreased food intake from anorexia of aging and chewing difficulties negatively influences stool volume, consistency, and bowel movements. 3

Environmental and Social Factors

• Lack of toilet access, especially in patients with decreased mobility, is a critical but often overlooked cause. 3, 1
• Living situation (alone versus with family, nursing home placement) affects toileting habits and constipation risk. 3
• Privacy and comfort to allow normal defecation are essential factors. 3

Structural and Defecatory Disorders

Evacuation Disorders

• After excluding systemic diseases, the differential diagnosis narrows to three processes: evacuation disorder (spastic or flaccid varieties) and normal or slow transit constipation. 4
• Pelvic floor dyssynergia (anismus) and descending perineum syndrome represent spastic and flaccid evacuation disorders respectively. 4
• Digital rectal examination should be performed when constipation is identified to detect rectal impaction or structural abnormalities. 3

Structural Causes

• Abdominal/pelvic masses, radiation fibrosis, and colorectal pathology must be excluded. 1
• Plain abdominal X-ray may be useful to image the extent of fecal loading and exclude bowel obstruction. 3

Critical Diagnostic Approach

Assessment should include questions to determine possible causes for constipation, focusing on medication history, underlying medical conditions, mobility status, and living situation. 3

• Physical examination should include abdominal examination, perineal inspection, and digital rectal examination. 3
• Investigations are not routinely necessary unless severe symptoms, sudden changes in bowel movement patterns, blood in stool, or older adults relative to their health status warrant further evaluation. 3
• In elderly patients, there is usually more than one etiologic mechanism, requiring recognition of multiple contributing factors. 6

Common Pitfalls to Avoid

• Do not assume constipation is a physiological consequence of normal aging—it always has identifiable causes. 6, 7
• Avoid overlooking medication review as the first step, as this is the most modifiable factor. 3, 1
• Do not order extensive investigations routinely; target testing based on clinical suspicion. 3
• Recognize that hypothyroidism is the most common systemic disease and should be checked early. 4