What is the diagnosis and management of left lower quadrant abdominal pain?

Left Lower Quadrant Pain: Diagnosis and Management

Initial Diagnostic Approach

Order CT abdomen and pelvis with IV contrast immediately for most patients presenting with left lower quadrant pain—this is the single most important diagnostic step with 98% accuracy and should not be delayed. 1, 2

Clinical Assessment Priorities

• Do not rely on clinical examination alone—misdiagnosis rates range from 34-68% when imaging is not obtained 2
• The classic triad of left lower quadrant pain, fever, and leukocytosis is present in only 25% of diverticulitis cases 2
• When all three criteria are present (left lower quadrant tenderness, CRP >50 mg/L, absence of vomiting), diagnostic accuracy reaches 97%, but this occurs in only 24% of patients 2

Laboratory Testing

• Obtain CRP level—CRP >170 mg/L predicts severe diverticulitis with 87.5% sensitivity and 91.1% specificity 2
• White blood cell count with differential—left shift >75% suggests bacterial infection 2

Imaging Strategy

First-Line Imaging: CT with IV Contrast

CT abdomen and pelvis with IV contrast is rated 8/9 (usually appropriate) by the American College of Radiology and should be the default imaging choice. 1, 2

Benefits of CT with IV Contrast:

• Detects complications (abscess, fistula, obstruction, perforation) 2
• Identifies alternative diagnoses in 49% of cases 2
• Reduces hospital admissions by >50% 2
• Sensitivity and specificity approach 100% for sigmoid diverticulitis 2
• Provides comprehensive evaluation of all abdominal organs in a single examination 2

Special Population Considerations

• Premenopausal women with suspected gynecologic pathology: Order pelvic/transvaginal ultrasound as initial imaging 1, 2
• Pregnant patients: Use ultrasonography or MRI instead of CT to avoid radiation exposure 2
• When IV contrast is contraindicated: CT without IV contrast is acceptable (rated 6/9) but less accurate for detecting abscesses 2

Differential Diagnosis

Most Common Causes

Acute diverticulitis of the sigmoid or descending colon is the most common cause in adults, but the differential is broad 1:

• Colitis and inflammatory bowel disease 1
• Epiploic appendagitis 1
• Bowel obstruction 1
• Hernia 1
• Ovarian and fallopian tube pathology 1
• Pyelonephritis and urolithiasis 1
• Rare but critical: Left-sided appendicitis in patients with situs inversus totalis 3, 4

Management Based on CT Findings

Uncomplicated Diverticulitis (No Abscess, Perforation, or Fistula)

For immunocompetent patients: Conservative management WITHOUT antibiotics is the recommended approach. 2, 5

• Clear liquid diet with advancement as tolerated 2
• Pain control with oral analgesics 2
• Outpatient management is appropriate if patient can tolerate oral intake 2

For immunocompromised or elderly patients only: Antibiotics for maximum 7 days 2, 5

• Ertapenem 1 g q24h OR Eravacycline 1 mg/kg q12h 2

Complicated Diverticulitis with Small Abscess (<4 cm)

Antibiotics alone for 7 days without drainage 2, 5

• Ertapenem 1 g q24h OR Eravacycline 1 mg/kg q12h 2

Complicated Diverticulitis with Large Abscess (≥4 cm)

Percutaneous drainage PLUS antibiotics for 4 days 2, 5

• Stop antibiotics at 4 days if source control is adequate in immunocompetent, non-critically ill patients 2
• Continue up to 7 days in immunocompromised or critically ill patients 2

Septic Shock

Escalate immediately to broad-spectrum carbapenem therapy: 2

• Meropenem 1 g q6h by extended infusion OR
• Doripenem 500 mg q8h by extended infusion OR
• Imipenem/cilastatin 500 mg q6h by extended infusion 2

Perforation with Diffuse Peritonitis

Emergency surgical consultation required immediately 2

• Clinically stable patients without major comorbidities: Primary resection and anastomosis with or without diverting stoma 2
• Critically ill patients or those with multiple major comorbidities: Hartmann's procedure 2

Red Flags Requiring Emergency Evaluation

Send immediately to the emergency department if any of the following are present: 2

• Fever with inability to pass gas or stool 2
• Severe abdominal tenderness with guarding or rebound 2
• Vomiting 2
• Bloody stools 2
• Signs of shock (hypotension, tachycardia, altered mental status) 2
• Progressively worsening pain over several days 2
• Signs of peritonitis (diffuse tenderness, absent bowel sounds) 2

Critical Pitfalls to Avoid

Cancer Mimicking Diverticulitis

CT findings suggesting cancer rather than diverticulitis include: 2

• Pericolonic lymphadenopathy >1 cm with or without pericolonic edema 2
• Luminal colon mass 2

Colonoscopy Timing

Routine colonoscopy after CT-confirmed uncomplicated diverticulitis is NOT warranted except for: 1, 2

• Age-appropriate colon cancer screening not yet performed 1
• Abnormal pericolic lymph nodes on CT 1
• Luminal colon mass on CT 1
• Uncertain diagnosis (inflammatory bowel disease or ischemic colitis) 1
• Presence of abscess, perforation, or fistula 2

Antibiotic Duration

Do not continue antibiotics beyond 7 days in uncomplicated cases—this increases resistance without improving outcomes 2

• If signs of infection persist beyond 7 days, obtain repeat imaging to assess for inadequate source control 2

Follow-Up and Recurrent Pain

When Structural Pathology Has Been Excluded

Functional bowel disorders become the most likely diagnosis when CT and colonoscopy are normal 5

• Pain related to bowel movements or dietary triggers suggests irritable bowel syndrome 5
• Cyclical pain in women requires pelvic ultrasound for gynecologic etiology 5

Indications for Repeat Imaging or Referral

Repeat colonoscopy is warranted if: 5

• Weight loss, anemia, or change in bowel habits develop 5
• New pericolonic lymphadenopathy >1 cm on repeat imaging 5

Consider gastroenterology referral for functional bowel disorder management or persistent symptoms despite conservative measures 5

Consider gynecology referral if pelvic ultrasound reveals pathology in women with recurrent pain 5