What is the appropriate workup and initial management for a 57-year-old woman presenting with new left lower‑quadrant abdominal pain?

Workup and Management of Left Lower Quadrant Pain in a 57-Year-Old Woman

Order CT abdomen and pelvis with IV contrast immediately—this is the single most important diagnostic test with 98% accuracy and should be your default imaging choice for left lower quadrant pain in this age group. 1

Initial Clinical Assessment

Before imaging, perform a focused evaluation looking for:

• Left lower quadrant tenderness on palpation 1
• Fever (temperature >38°C) 1
• Presence or absence of vomiting 1
• Signs of peritonitis (guarding, rebound tenderness, rigidity) 1

Important clinical pearl: If all three criteria are present—left lower quadrant tenderness, CRP >50 mg/L, and absence of vomiting—the diagnosis of diverticulitis has 97% accuracy, though this triad occurs in only 24% of patients. 1 However, clinical diagnosis alone is unreliable with misdiagnosis rates of 34-68%, so imaging remains essential. 1

Laboratory Testing

Order the following labs immediately:

• Complete blood count with differential (left shift >75% suggests bacterial infection) 1
• C-reactive protein (CRP >170 mg/L predicts severe diverticulitis with 87.5% sensitivity and 91.1% specificity) 1
• Pregnancy test (mandatory in women of reproductive age before CT) 1

Imaging Strategy

CT abdomen and pelvis with IV contrast is rated 8/9 (usually appropriate) by the American College of Radiology and should be ordered for most patients. 1 This modality provides:

• Superior detection of complications (abscess, perforation, fistula) 1
• Identification of alternative diagnoses 1
• Guidance for treatment decisions 1
• Risk stratification that reduces hospital admissions by >50% 1

Special Population Consideration

For premenopausal women with suspected gynecologic pathology, order pelvic/transvaginal ultrasound as the initial imaging study instead. 1 Consider ovarian torsion, ectopic pregnancy, tubo-ovarian abscess, and ovarian cysts in the differential.

Alternative Imaging

• CT without IV contrast is acceptable when IV contrast is contraindicated (renal insufficiency, contrast allergy), though less accurate for detecting abscesses (rated 6/9). 1
• Ultrasound with graded compression can reduce unnecessary CT examinations but is operator-dependent and limited in obese patients. 2, 3

Differential Diagnosis

Acute sigmoid diverticulitis is the most common cause of left lower quadrant pain in adults over age 50. 2, 1 Other critical diagnoses to consider include:

• Perforated colon cancer (look for pericolonic lymphadenopathy >1 cm on CT—this strongly suggests malignancy over diverticulitis) 1, 4
• Colitis (infectious, ischemic, inflammatory bowel disease) 1
• Epiploic appendagitis 1, 3
• Bowel obstruction 1
• Gynecologic pathology (ovarian torsion, ectopic pregnancy, tubo-ovarian abscess) 1
• Renal colic or pyelonephritis 3
• Atypical appendicitis (rare but can present with LLQ pain if appendix is elongated or with situs inversus) 5

Red Flag Symptoms Requiring Emergency Department Evaluation

Send the patient to the emergency department immediately if any of the following are present:

• Fever with inability to pass gas or stool 1
• Severe abdominal tenderness with guarding or rebound 1
• Signs of shock (hypotension, tachycardia, altered mental status) 1
• Vomiting 1
• Bloody stools 1
• Progressively worsening pain over several days 1

These symptoms suggest complicated diverticulitis with perforation, abscess, or bowel obstruction requiring urgent intervention. 1

Treatment Algorithm Based on CT Findings

Uncomplicated Diverticulitis (bowel wall thickening with pericolonic fat stranding, no abscess/perforation)

For immunocompetent patients: Conservative management WITHOUT antibiotics is appropriate. 1 This includes:

• Clear liquid diet with advancement as tolerated 1
• Oral analgesics for pain control 1
• Outpatient management if able to tolerate oral intake 1

For immunocompromised or elderly patients: Prescribe antibiotics for maximum 7 days. 1 Recommended regimens include:

• Ertapenem 1 g IV/IM every 24 hours 1
• Eravacycline 1 mg/kg IV every 12 hours 1

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

Antibiotic therapy alone for 7 days without drainage. 1 Use the same antibiotic regimens as above.

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

Percutaneous CT-guided drainage PLUS antibiotics for 4 days. 1 Stop antibiotics at 4 days if source control is adequate and patient is clinically improving. 1

Perforation with Peritonitis or Septic Shock

Emergency surgical consultation is mandatory. 1 If septic shock is present, escalate to:

• Meropenem 1 g IV every 6 hours by extended infusion 1
• Doripenem 500 mg IV every 8 hours by extended infusion 1
• Imipenem/cilastatin 500 mg IV every 6 hours by extended infusion 1

Critical Pitfalls to Avoid

Do not miss colon cancer: Pericolonic lymphadenopathy >1 cm with or without pericolonic edema on CT suggests cancer rather than diverticulitis. 1, 4 These patients require colonoscopy after acute episode resolves.

Do not order routine colonoscopy after uncomplicated diverticulitis: Colonoscopy is only indicated if abscess, perforation, fistula is present, abnormal lymph nodes are seen on CT, or age-appropriate screening has not been performed. 1

Do not continue antibiotics beyond 7 days in uncomplicated cases: This increases antibiotic resistance without improving outcomes. 1

Do not rely on clinical examination alone: Rebound tenderness in the left lower quadrant has poor diagnostic accuracy for distinguishing between diverticulitis and other pathology. 1

Follow-Up and Monitoring

Repeat imaging if: 1

• Fever and leukocytosis persist beyond 48-72 hours despite appropriate treatment
• Clinical deterioration occurs
• Signs of infection persist beyond 7 days

Outpatient management requires: 1

• Ability to tolerate oral intake
• Normal or near-normal bowel movements
• No peritoneal signs on examination
• Reliable follow-up within 48-72 hours