What is the appropriate evaluation and management for a patient with referred pain to the left lower quadrant, potentially indicating diverticulitis, ovarian cysts, or kidney stones?

Evaluation and Management of Left Lower Quadrant Pain

Initial Imaging Strategy

CT abdomen and pelvis with IV contrast is the preferred first-line imaging modality for evaluating left lower quadrant pain, with 98% diagnostic accuracy and the ability to detect complications, guide treatment decisions, and reduce hospital admissions by more than 50%. 1, 2

The American College of Radiology rates CT with IV contrast as 8/9 (usually appropriate) for this indication. 1, 2 This imaging modality provides:

• Superior detection of diverticulitis complications (abscess, perforation, fistula, obstruction) 1
• Identification of alternative diagnoses that present with similar symptoms 1, 2
• Risk stratification for operative versus nonoperative management 1
• Guidance for inpatient versus outpatient triage 1

Critical Exception: Premenopausal Women

For premenopausal women with suspected gynecologic pathology, obtain pelvic/transvaginal ultrasound as the initial imaging study. 1, 2 Gynecologic and nongynecologic pathology may present with identical clinical pictures in this population, making ultrasound the appropriate first step. 1

When Imaging May Not Be Required

Imaging may be deferred in highly selected patients with: 1, 2

• Typical symptoms of diverticulitis
• Prior documented history of diverticulitis with similar presentation
• No evidence of complications on clinical examination
• Mild, stable symptoms without fever or peritoneal signs

However, clinical diagnosis alone has misdiagnosis rates of 34-68%, so there is a strong trend toward imaging confirmation even in suspected recurrent cases. 1, 2

Red Flag Symptoms Requiring Emergency Evaluation

Immediate emergency department evaluation is mandatory for: 2

• Fever combined with left lower quadrant pain (suggests complicated diverticulitis)
• Inability to pass gas or stool (90% sensitive for large bowel obstruction)
• Severe abdominal tenderness with guarding or rebound (indicates peritonitis)
• Vomiting with progressive pain
• Bloody stools
• Signs of shock (tachycardia, hypotension, altered mental status)
• Progressively worsening pain over several days

Management Based on CT Findings

Uncomplicated Diverticulitis (No Abscess, Perforation, or Fistula)

Conservative management WITHOUT antibiotics is recommended for immunocompetent patients with uncomplicated diverticulitis. 2

For immunocompromised or elderly patients only: 2

• Antibiotics for maximum 7 days
• Ertapenem 1 g q24h OR Eravacycline 1 mg/kg q12h

Complicated Diverticulitis with Small Abscess (<3-4 cm)

Antibiotic therapy alone for 7 days without drainage. 2 Percutaneous drainage is not indicated for small abscesses. 2

Complicated Diverticulitis with Large Abscess (≥3-4 cm)

Percutaneous drainage combined with antibiotic therapy for 4 days. 2 This approach is appropriate for immunocompetent, non-critically ill patients. 2

Stop antibiotics at 4 days if source control is adequate and clinical improvement is evident. 2

Perforation with Peritonitis or Septic Shock

Emergency surgical consultation is required immediately. 2 Management includes:

• Broad-spectrum carbapenem therapy (Meropenem 1 g q6h by extended infusion, Doripenem 500 mg q8h by extended infusion, or Imipenem/cilastatin 500 mg q6h by extended infusion) 2
• Primary resection and anastomosis with or without diverting stoma for stable patients 2
• Hartmann's procedure for critically ill patients or those with multiple comorbidities 2

Alternative Diagnoses to Consider

Ovarian Pathology

In premenopausal women, transvaginal ultrasound will identify ovarian cysts, torsion, or tubo-ovarian abscess. 1, 2

Kidney Stones

CT without contrast can identify urolithiasis, though CT with IV contrast provides more comprehensive evaluation. 1, 3

Atypical Appendicitis

Appendicitis can rarely present with left lower quadrant pain due to intestinal malrotation or an unusually long appendix projecting into the left lower quadrant. 4, 5, 6 CT will identify this anatomic variant and prevent diagnostic delay. 4, 5

Colon Cancer

CT findings suggesting malignancy rather than diverticulitis include: 1, 2

• Pericolonic lymphadenopathy >1 cm in short axis
• Luminal mass
• Absence of pericolonic fat stranding extending to the mesenteric root

Critical Pitfall: Colonoscopy Timing

Routine colonoscopy after CT-confirmed uncomplicated diverticulitis is NOT warranted, except for age-appropriate colon cancer screening. 1, 2

Colonoscopy IS indicated when: 2

• Abscess, perforation, or fistula identified on CT
• Pericolonic lymphadenopathy >1 cm
• Luminal mass visualized
• Uncertain diagnosis despite imaging

The risk of colon cancer after CT-confirmed diverticulitis approximates that of asymptomatic patients, not symptomatic patients. 1

Role of Alternative Imaging Modalities

Ultrasound with Graded Compression

Can reduce unnecessary CT examinations but is operator-dependent and limited in obese patients. 1, 7 Less commonly used in the United States for nongynecologic left lower quadrant pain. 1

MRI

MRI has 100% sensitivity and specificity for differentiating cancer from diverticulitis in select studies, but lacks large-scale validation for general evaluation of left lower quadrant pain. 1 Consider MRI in pregnant patients to avoid radiation exposure. 2

Plain Radiography

Not useful as initial imaging because CT is far more accurate. 1 Radiography may identify large volume free air or bowel obstruction, but CT is more sensitive and specific for these findings. 1