What is the appropriate workup and treatment plan for a 75-year-old female with a history of diverticulosis presenting with acute lower abdominal pain and a negative urinalysis?

Diagnostic Approach and Management for Suspected Diverticulitis in a 75-Year-Old Female

CT scan with IV contrast of the abdomen and pelvis is the most appropriate initial diagnostic test for this 75-year-old female with acute lower abdominal pain and history of diverticulosis. 1

Initial Evaluation

The patient's presentation of acute lower abdominal pain with a history of diverticulosis strongly suggests acute diverticulitis. However, clinical diagnosis alone is unreliable, with misdiagnosis rates between 34-68% without imaging 2.

Key considerations in this case:

• 75-year-old female (elderly patient)
• History of diverticulosis on prior colonoscopy
• Acute lower abdominal pain
• Negative urinalysis (ruling out urinary tract pathology)

Diagnostic Workup

Imaging

1. CT Abdomen/Pelvis with IV contrast:

   • First-line imaging for suspected diverticulitis in elderly patients 1
   • Superior sensitivity (95%) and specificity (96-99%) compared to other modalities 1
   • Allows assessment of disease severity and complications 1
   • Helps distinguish complicated from uncomplicated diverticulitis 1
   • Can rule out alternative diagnoses such as colon cancer 1

2. Alternative imaging (if CT with contrast is contraindicated):

   • Ultrasound (sensitivity 90%, specificity 90-100%) 1
   • CT without IV contrast 1
   • MRI (limited availability in emergency settings) 1

Laboratory Tests

• Complete blood count (assess for leukocytosis)
• C-reactive protein (CRP) level
• Basic metabolic panel 3

Management Algorithm

Step 1: Risk Stratification Based on CT Findings

Classify as either:

• Uncomplicated diverticulitis: Colonic wall thickening, inflammation of pericolic fat
• Complicated diverticulitis: Presence of abscess, perforation, fistula, or obstruction

Step 2: Treatment Based on Classification

For Uncomplicated Diverticulitis:

• If patient is immunocompetent with mild symptoms:

  • Clear liquid diet during acute phase, advancing as symptoms improve 1
  • Antibiotics may be avoided if no comorbidities, no fever, and normal/mildly elevated inflammatory markers 1

• If patient has any of these risk factors:

  • Comorbidities (common in elderly patients)
  • Frailty
  • Refractory symptoms or vomiting
  • CRP >140 mg/L or WBC >15 × 10^9/L
  • Fluid collection or longer segment of inflammation on CT

  Then initiate antibiotic therapy:

  • Amoxicillin-clavulanate (Augmentin) 875/125 mg orally twice daily for 4-7 days 2
  • Consider hospitalization if unable to tolerate oral intake or if significant pain

For Complicated Diverticulitis:

• If abscess present:
  • Small abscess: Antibiotics alone 1
  • Large abscess (≥3 cm): Percutaneous drainage plus IV antibiotics 1, 3
• If perforation, peritonitis, or obstruction:
  • Hospital admission
  • IV antibiotics
  • Surgical consultation

Step 3: Follow-up

• Reassess in 48-72 hours if outpatient management
• Consider colonoscopy 6-8 weeks after symptom resolution 1, 2
  • Especially important in this case to rule out colon cancer, as diverticulitis can mimic malignancy 1

Important Considerations and Pitfalls

• Age-related concerns: Elderly patients may have atypical presentations of diverticulitis with less pronounced symptoms 1

  • Only 50% of patients >65 years have pain in lower quadrants
  • Only 17% have fever
  • 43% do not have leukocytosis

• Differential diagnosis: Important to consider other causes of lower abdominal pain:

  • Colon cancer (can mimic diverticulitis) 1
  • Inflammatory bowel disease
  • Ischemic colitis
  • Small bowel pathology (rare jejunal diverticulitis) 4, 5

• Warning signs requiring immediate medical attention:

  • Development of fever
  • Worsening abdominal pain
  • Inability to tolerate oral intake
  • Signs of peritonitis (rigid abdomen, rebound tenderness) 2

This approach prioritizes early diagnosis with appropriate imaging to guide treatment decisions, which directly impacts morbidity and mortality outcomes in this elderly patient with suspected diverticulitis.