What is the next step in workup for an 80-year-old male (M) with a past medical history (PMHx) of Parkinson's disease and thyroid cancer presenting with bloating and constipation at the outpatient Gastrointestinal (GI) clinic?

Diagnostic Workup for Bloating and Constipation in an Elderly Patient with Parkinson's Disease

The next step in workup for this 80-year-old male with Parkinson's disease and thyroid cancer presenting with bloating and constipation should be a digital rectal examination followed by a complete blood count and stool hemoccult test. 1

Initial Assessment

When evaluating bloating and constipation in an elderly patient with Parkinson's disease, it's important to recognize that:

• Constipation occurs in over 50% of Parkinson's disease patients and may worsen as the disease progresses 2
• Difficult defecation (obstructed defecation, dyssynergia) is the primary pathophysiology underlying constipation in Parkinson's disease 2
• Bloating is highly prevalent in patients with constipation and can significantly impact quality of life 1, 3

Key Physical Examination Components

The physical examination should include:

• Abdominal examination: Assess for distension, masses, tenderness, and bowel sounds 1
• Perineal inspection: Look for skin tags, fissures, prolapse, or ulceration 1
• Digital rectal examination (DRE): Essential to assess for:
  • Sphincter tone (may be lax in Parkinson's disease)
  • Presence of impacted stool
  • Rectal masses or obstruction
  • Evidence of pelvic floor dyssynergia 1

Diagnostic Testing Algorithm

1. First-line laboratory tests:

   • Complete blood count (CBC)
   • Stool hemoccult test 1

2. Based on clinical suspicion:

   • Thyroid function tests (especially with history of thyroid cancer)
   • Serum calcium levels (to rule out hypercalcemia)
   • Comprehensive metabolic panel 1

3. Consider colonoscopy if:

   • Patient is over 50 years old (this patient is 80)
   • Presence of alarm symptoms (weight loss, blood in stool)
   • Recent change in bowel habits 1

4. Specialized testing if initial management fails:

   • Anorectal manometry to evaluate for pelvic floor dyssynergia (particularly important in Parkinson's patients) 1
   • Defecography if structural abnormalities are suspected 1
   • Whole gut transit study if slow transit constipation is suspected 1

Management Considerations

After completing the diagnostic workup, treatment should be guided by findings:

1. For constipation:

   • Increase dietary fiber and fluid intake
   • Consider osmotic laxatives like polyethylene glycol (PEG) 3350 4
   • For more severe symptoms, consider secretagogues like lubiprostone which have shown improvement in constipation-related bloating 5

2. For bloating:

   • Low-FODMAP diet may be beneficial 6
   • Simethicone for gas-related bloating 6
   • Central neuromodulators (tricyclic antidepressants) if visceral hypersensitivity is suspected 1, 6

3. For Parkinson's-related constipation:

   • Evaluate timing of levodopa in relation to meals as gastroparesis may affect medication absorption and contribute to constipation 7
   • Consider prokinetic agents if gastroparesis is suspected 7

Important Considerations and Pitfalls

• Avoid missing defecatory disorders: Pelvic floor dyssynergia is common in Parkinson's disease and requires specific management with biofeedback therapy 1, 2

• Medication review is essential: Many medications can worsen constipation, including those used for Parkinson's disease 2

• Watch for complications: Severe constipation in Parkinson's patients can lead to megacolon, fecal impaction, or bowel obstruction 2

• Consider impact on levodopa absorption: Gastroparesis and constipation can affect the absorption of Parkinson's medications, potentially worsening motor symptoms 7

This systematic approach will help identify the underlying cause of bloating and constipation in this elderly patient with Parkinson's disease, allowing for targeted treatment to improve symptoms and quality of life.