What is the appropriate evaluation and management for a patient with lower left quadrant pain, potentially indicating diverticulitis or inflammatory bowel disease?

Evaluation and Management of Lower Left Quadrant Pain

Immediate Imaging Strategy

CT abdomen and pelvis with IV contrast is the preferred initial imaging modality for evaluating lower left quadrant pain, with 98% diagnostic accuracy and should be ordered immediately in most patients. 1, 2

Why CT with IV Contrast is Superior

• CT provides comprehensive evaluation including detection of complications (abscess, perforation, fistula), identification of alternative diagnoses, risk-stratification for operative versus nonoperative management, and reduction of hospital admissions by >50% 1, 2
• The American College of Radiology rates CT abdomen and pelvis with IV contrast as 8/9 (usually appropriate) and should be the default imaging choice 2
• IV contrast improves characterization of bowel wall abnormalities and complications, though unenhanced CT is acceptable when IV contrast is contraindicated 1
• Radiation dose-reduced CT (50-90% less than standard dose) maintains similar sensitivity and specificity for acute diverticulitis 1

Alternative Imaging Considerations

• Plain radiography is not useful as initial imaging because CT is more accurate, though it may play a role in triage of severely ill patients 1
• Ultrasound with graded compression can reduce unnecessary CT examinations but is operator-dependent and limited in obese patients 2
• For premenopausal women with suspected gynecologic pathology, pelvic/transvaginal ultrasound is the preferred initial imaging 1, 2

Clinical Assessment: What to Look For

Classic Presentation (Present in Only 25% of Cases)

• Left lower quadrant pain, fever, and leukocytosis is the classic triad for diverticulitis, but its absence does not exclude the diagnosis 1, 2
• Clinical diagnosis alone is unreliable with misdiagnosis rates between 34-68% 1, 2

High-Accuracy Clinical Criteria (When All Present)

When left lower quadrant tenderness, CRP >50 mg/L, and absence of vomiting are ALL present, diagnostic accuracy reaches 97%—but this occurs in only 24% of patients 2

Red Flag Symptoms Requiring Emergency Evaluation

• Fever with inability to pass gas or stool suggests complicated diverticulitis or obstruction 2
• Severe abdominal tenderness with guarding or rebound indicates possible perforation or peritonitis 2
• Vomiting with bloody stools or signs of shock 2
• Progressively worsening pain over several days 2

Laboratory Markers to Obtain

• C-reactive protein >170 mg/L predicts severe diverticulitis with 87.5% sensitivity and 91.1% specificity 2
• White blood cell count with differential where left shift >75% suggests bacterial infection 2
• Lactate level to assess for sepsis 3

Management Algorithm Based on CT Findings

Uncomplicated Diverticulitis (No Abscess, Perforation, or Fistula)

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

• Antibiotics for maximum 7 days are recommended ONLY in immunocompromised or elderly patients 2
• Most uncomplicated diverticulitis can be managed outpatient with clear liquid diet advancement and oral analgesics 2

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

Antibiotic therapy alone for 7 days without drainage is recommended 2

• Ertapenem 1 g q24h or Eravacycline 1 mg/kg q12h are standard regimens 2

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

Percutaneous CT-guided drainage PLUS antibiotics for 4 days is recommended 2

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

Perforation with Diffuse Peritonitis

Emergency surgical consultation is required immediately 2

• Free air on CT or fecal peritonitis mandates emergent surgery 2
• Broad-spectrum carbapenem therapy (Meropenem 1 g q6h, Doripenem 500 mg q8h, or Imipenem/cilastatin 500 mg q6h by extended infusion) if septic shock is present 2

Critical Pitfalls to Avoid

Imaging Interpretation Errors

CT findings suggesting cancer rather than diverticulitis include pericolonic lymphadenopathy >1 cm with or without pericolonic edema 2

• Look for intestinal wall thickening with pericolonic fat stranding as the hallmark CT finding for diverticulitis 2
• Extraluminal gas or intra-abdominal fluid indicates perforation 2

Colonoscopy Timing

Routine colonoscopy after CT-confirmed uncomplicated diverticulitis is NOT warranted except for age-appropriate screening not yet performed 2

• Colonoscopy IS indicated if abnormal pericolic lymph nodes on CT, luminal colon mass, uncertain diagnosis, or presence of abscess, perforation, or fistula 2

Antibiotic Duration

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

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

Rare but Important Alternative Diagnosis

Left-sided appendicitis with situs inversus or midgut malrotation can present with left lower quadrant pain and is easily missed 4, 5, 6

• CT immediately reveals situs inversus and prevents delayed diagnosis 5, 6
• Early clinical suspicion and adequate observation are indicated when clinical features are uncertain 4

Special Population Considerations

Elderly Patients

Elderly patients present atypically, with only 50% having pain in the lower quadrants and only 17% having fever 3

• In-hospital mortality increases significantly with age: 1.6% in patients <65 years, 9.7% in patients 65-79 years, and 17.8% in patients >80 years 3
• Do not assume low CRP excludes complicated diverticulitis, as 39% of patients with complicated episodes have CRP below 175 mg/L 3

Women of Reproductive Age

Consider gynecologic causes and obtain pregnancy testing before ordering CT 2

• In pregnant patients, ultrasonography and MRI are preferred over CT to avoid radiation exposure 2