What is the best course of action for an 80-year-old patient with a history of Parkinson's disease and diverticulitis, presenting with left lower abdominal pain, reduced appetite, and weight loss, who has been taking a stool softener for a month?

Management of Chronic Left Lower Abdominal Pain in an Elderly Patient with Parkinson's Disease and History of Diverticulitis

This patient requires urgent CT abdomen and pelvis with IV contrast to rule out complicated diverticulitis or malignancy, as chronic symptoms lasting one month with reduced oral intake in an octogenarian with prior diverticulitis represents a high-risk presentation that cannot be managed based on clinical assessment alone. 1, 2

Why Imaging Cannot Be Delayed

• Clinical examination is unreliable in elderly patients with suspected diverticulitis, with misdiagnosis rates of 34-68% and only 50% of patients older than 65 years presenting with typical lower quadrant pain. 1, 2
• Only 17% of elderly patients with acute left colonic diverticulitis present with fever, and 43% lack leukocytosis, making clinical diagnosis dangerously inaccurate. 1
• The one-month duration of symptoms with progressive anorexia raises concern for malignancy masquerading as diverticulitis, particularly given CT findings that can distinguish cancer (pericolonic lymphadenopathy >1 cm) from diverticulitis. 3
• Mortality in patients above 80 years with acute left colonic diverticulitis is 17.8%, compared to 1.6% in those younger than 65 years, making aggressive diagnostic evaluation mandatory. 2

Immediate Diagnostic Workup

Laboratory Studies to Order Now

• Complete blood count with differential to assess for leukocytosis and left shift. 2
• C-reactive protein (CRP >170 mg/L predicts severe diverticulitis with 87.5% sensitivity). 2
• Lactate level to assess for occult sepsis or bowel ischemia. 2
• Blood cultures if fever is present or suspected. 2

Imaging Protocol

• CT abdomen and pelvis with IV contrast is rated 8/9 (usually appropriate) by the American College of Radiology and has 98-100% sensitivity and specificity for diagnosing diverticulitis and identifying complications. 2, 3
• Look specifically for bowel wall thickening with pericolonic fat stranding, extraluminal air indicating perforation, abscess formation, free fluid, and alternative diagnoses including malignancy. 2, 3
• If IV contrast is contraindicated due to renal disease, CT without contrast is acceptable though less accurate for detecting abscesses (rated 6/9). 3

Treatment Algorithm Based on CT Findings

If Uncomplicated Diverticulitis (No Abscess, Perforation, or Fistula)

• In elderly patients, antibiotic therapy for maximum 7 days is recommended, using Ertapenem 1 g every 24 hours or Eravacycline 1 mg/kg every 12 hours. 2, 3
• Advance diet from clear liquids as tolerated with pain control using oral analgesics. 3
• Do NOT continue antibiotics beyond 7 days, as this increases resistance without improving outcomes. 3

If Complicated Diverticulitis with Small Abscess (<4 cm)

• Antibiotic therapy alone for 7 days without drainage is recommended. 2, 3
• Use Ertapenem 1 g every 24 hours as the standard regimen. 3

If Complicated Diverticulitis with Large Abscess (≥4 cm)

• Percutaneous CT-guided drainage PLUS IV antibiotics for 4 days is the recommended approach if the patient is hemodynamically stable. 2, 3
• Stop antibiotics at 4 days if source control is adequate and clinical improvement is evident. 3

If Perforation with Peritonitis or Free Air

• Immediate emergency surgical consultation for laparotomy with colonic resection is mandatory. 2
• Start broad-spectrum carbapenem therapy immediately (Meropenem 1 g every 6 hours by extended infusion, Doripenem 500 mg every 8 hours, or Imipenem/cilastatin 500 mg every 6 hours). 3

Critical Red Flags in This Case

Parkinson's Disease Complicates the Clinical Picture

• Parkinson's disease causes constipation and reduced gut motility, which can mask or mimic diverticular disease symptoms. 1
• The chronic use of stool softeners without improvement over one month suggests inadequate treatment or an alternative/additional diagnosis requiring investigation. 1

Progressive Anorexia and Reduced Oral Intake

• Weight loss and reduced appetite lasting one month in an elderly patient with prior diverticulitis mandates exclusion of colon cancer, as CT findings of pericolonic lymphadenopathy >1 cm with or without pericolonic edema suggest malignancy rather than diverticulitis. 3
• Colonoscopy should be performed after acute inflammation resolves if abscess, perforation, fistula is present on CT, or if abnormal pericolic lymph nodes or luminal mass is identified. 3

Low CRP Does Not Exclude Serious Disease

• 39% of patients with complicated diverticulitis have CRP below 175 mg/L, so normal inflammatory markers do not rule out perforation or abscess. 1, 2

Disposition and Follow-Up

• Admission is required if any of the following are present: inability to tolerate oral intake, signs of peritonitis on examination, abscess on CT requiring drainage, or social factors preventing reliable outpatient follow-up in an elderly patient with Parkinson's disease. 4
• Outpatient management may be appropriate only if CT confirms uncomplicated diverticulitis, the patient can tolerate oral intake, has no signs of peritonitis, and has reliable support at home. 3, 4
• Repeat imaging is mandatory if fever and leukocytosis persist beyond 48-72 hours despite appropriate treatment, as this indicates inadequate source control. 2, 3

Common Pitfalls to Avoid

• Do not rely on the absence of fever or leukocytosis to exclude serious pathology in elderly patients, as atypical presentations are the norm. 1, 2
• Do not assume chronic symptoms represent "just constipation" in a patient with Parkinson's disease—the one-month duration with progressive anorexia demands exclusion of structural pathology. 3
• Do not delay CT imaging waiting for clinical deterioration—elderly patients decompensate rapidly and have significantly higher mortality once complications develop. 2
• Do not continue antibiotics beyond 7 days in uncomplicated cases, as prolonged therapy increases antibiotic resistance without clinical benefit. 3