What is the appropriate management and treatment for a patient presenting with left-sided abdominal pain?

Management of Left-Sided Abdominal Pain

For a patient presenting with left-sided abdominal pain, obtain a focused history and physical examination looking specifically for left lower quadrant tenderness, fever, and signs of peritonitis, then proceed with CT abdomen/pelvis with IV contrast if there is diagnostic uncertainty, as acute left-sided colonic diverticulitis is the most common serious pathology requiring specific management. 1

Initial Clinical Assessment

Key History Elements to Obtain

• Duration and onset of pain: Acute onset (hours to days) suggests diverticulitis, while chronic/recurrent pain points toward functional disorders 1, 2
• Location specificity: Left lower quadrant pain with localized tenderness is classic for diverticulitis, occurring in 50-83% of cases under age 65, but only 50% of elderly patients 1, 3
• Associated symptoms: Fever and inability to tolerate oral intake indicate complicated disease requiring hospitalization 1
• Red flag symptoms: Vomiting, inability to pass gas/stool, bloody stools, or hemodynamic instability mandate immediate imaging and surgical consultation 3, 2

Physical Examination Priorities

• Vital signs: Hypotension (systolic BP <90 mmHg) and tachycardia indicate septic shock requiring immediate resuscitation and broad-spectrum antibiotics 3
• Abdominal examination: Localized left lower quadrant tenderness without peritoneal signs suggests uncomplicated diverticulitis, while guarding and rebound indicate perforation 1, 3
• Age considerations: Elderly patients (>65 years) present atypically with only 17% having fever, making clinical diagnosis unreliable 3

Laboratory Testing

• Complete blood count with differential: Elevated WBC with left shift (>75%) supports infection 1
• C-reactive protein: CRP >170 mg/L predicts severe diverticulitis with 87.5% sensitivity, though 39% of complicated cases have CRP <175 mg/L 3
• Lactate level: Elevated lactate indicates tissue hypoperfusion in septic shock 3
• Blood cultures: Obtain before antibiotics in hemodynamically unstable patients 3

Diagnostic Imaging Strategy

When to Image

Use CT abdomen/pelvis with IV contrast when diagnostic uncertainty remains after history and physical examination, particularly in patients without prior diverticulitis history or with atypical presentations. 1

• CT has 94% sensitivity and 99% specificity for diagnosing acute diverticulitis 1
• Clinical diagnosis alone has positive predictive value of only 0.65, with misdiagnosis rates of 34-68% 1, 3
• Ultrasound can be considered when CT is unavailable, though it is less sensitive 1

CT Findings Guide Management

• Uncomplicated diverticulitis: Bowel wall thickening, pericolonic fat stranding, no abscess or free air 1
• Small abscess (<4 cm): Pericolonic fluid collection 1
• Large abscess (≥4 cm): Requires percutaneous drainage 1, 3
• Perforation: Free air, diffuse peritonitis requiring emergency surgery 1, 3

Treatment Algorithm Based on Severity

Uncomplicated Diverticulitis (No Abscess, No Perforation)

Manage most patients with uncomplicated diverticulitis in the outpatient setting without antibiotics if they can tolerate oral intake, have adequate social support, and lack significant comorbidities. 1

Outpatient Management Criteria 1

• Ability to tolerate oral intake
• Adequate family or social support
• No significant comorbidities or immunosuppression
• Hemodynamically stable

Antibiotic Decision

Antibiotics can be avoided in immunocompetent patients with CT-confirmed uncomplicated diverticulitis who lack signs of sepsis. 1

• Antibiotic treatment does not accelerate recovery or prevent complications in uncomplicated disease 1
• Consider antibiotics for ≤7 days in immunocompromised or elderly patients 1
• Low-certainty evidence shows no difference in recurrence, emergency surgery, or mortality between antibiotic and no-antibiotic approaches 1

Complicated Diverticulitis with Small Abscess (<4 cm)

Treat with antibiotics alone for 7 days without drainage. 1

Antibiotic Regimens for Community-Acquired Infection 1

• Ertapenem 1 g IV q24h, OR
• Eravacycline 1 mg/kg IV q12h

Duration 1

• 4 days in immunocompetent, non-critically ill patients if source control adequate
• Up to 7 days in immunocompromised or critically ill patients based on clinical response

Complicated Diverticulitis with Large Abscess (≥4 cm)

Perform percutaneous CT-guided drainage combined with antibiotic therapy for 4 days. 1, 3

• If drainage not feasible in stable immunocompetent patients, antibiotics alone may be considered 1
• If drainage not feasible in critically ill or immunocompromised patients, surgical intervention is indicated 1

Septic Shock or Diffuse Peritonitis

Initiate immediate resuscitation with IV crystalloids, broad-spectrum antibiotics, and emergency surgical consultation. 3

Resuscitation 3

• Aggressive fluid resuscitation to restore systolic BP >90 mmHg
• Obtain blood cultures before antibiotics

Antibiotic Regimens for Septic Shock 1, 3

• Meropenem 1 g IV q6h by extended infusion or continuous infusion, OR
• Doripenem 500 mg IV q8h by extended infusion or continuous infusion, OR
• Imipenem/cilastatin 500 mg IV q6h by extended infusion, OR
• Eravacycline 1 mg/kg IV q12h

Surgical Management 1

• Primary resection with anastomosis (with or without diverting stoma) in clinically stable patients without major comorbidities
• Hartmann's procedure in critically ill patients or those with multiple comorbidities
• Emergency surgery for fecal peritonitis or diffuse purulent peritonitis

Critical Pitfalls to Avoid

• Do not rely on clinical examination alone: Misdiagnosis rates are 34-68% without imaging, and elderly patients present atypically 1, 3
• Do not delay antibiotics in septic patients: Start antibiotics immediately before imaging in hemodynamically unstable patients 3
• Do not assume normal CRP excludes complicated disease: 39% of complicated diverticulitis cases have CRP <175 mg/L 3
• Do not discharge without imaging: Patients with unexplained left-sided abdominal pain and concerning features require definitive diagnosis 2

Follow-Up and Monitoring

• Repeat imaging if fever and leukocytosis persist beyond 48-72 hours despite appropriate treatment 3
• Colonoscopy should be considered in patients >40 years after resolution to exclude underlying malignancy or Crohn's disease 1
• Recurrence risk: 22% at 10 years after first episode, 55% after second episode 1

Alternative Diagnoses to Consider

If CT excludes diverticulitis and other structural pathology:

• Functional bowel disorders (irritable bowel syndrome) if pain relates to bowel movements or diet 2
• Gynecologic causes in premenopausal women—obtain pelvic ultrasound 2
• Abdominal wall pain if tenderness increases with muscle tensing (positive Carnett's sign) 4
• Urolithiasis if flank pain or hematuria present 5