What are the diagnosis and treatment options for intermittent and moderate left lower quadrant abdominal pain?

Left Lower Quadrant Abdominal Pain: Diagnosis and Treatment

Initial Diagnostic Approach

CT abdomen and pelvis with IV contrast is the preferred imaging modality for most patients with intermittent moderate left lower quadrant pain, with a diagnostic accuracy of 98%. 1, 2

Clinical Assessment Limitations

• Clinical diagnosis alone is unreliable, with misdiagnosis rates between 34-68% 1, 2
• The classic triad of left lower quadrant pain, fever, and leukocytosis is present in only 25% of diverticulitis cases 1, 2
• When all three criteria (left lower quadrant tenderness, CRP >50 mg/L, absence of vomiting) are present, diagnostic accuracy reaches 97%, but this occurs in only 24% of patients 2

Imaging Strategy by Patient Population

For most patients: CT abdomen and pelvis with IV contrast is rated 8/9 (usually appropriate) by the American College of Radiology 1, 2, 3

For premenopausal women with suspected gynecologic pathology: Pelvic/transvaginal ultrasound is the preferred initial imaging 1, 2, 3

When IV contrast is contraindicated: CT without IV contrast is acceptable (rated 6/9), though less accurate for detecting abscesses 2, 3

Most Common Diagnoses

Diverticulitis (Most Common Cause)

Diverticulitis is the most common cause of left lower quadrant pain in adults. 1, 4

CT Findings Suggesting Diverticulitis:

• Intestinal wall thickening with pericolonic fat stranding 2
• Extraluminal gas or intra-abdominal fluid indicates perforation 2
• Abscess size determines drainage strategy 2

Critical Pitfall:

• Pericolonic lymphadenopathy >1 cm with or without pericolonic edema suggests cancer rather than diverticulitis 2, 5
• Routine colonoscopy after CT-confirmed diverticulitis is not warranted except for age-appropriate screening, unless abscess, perforation, or fistula is present 2

Alternative Diagnoses to Consider

• Colitis, fecal impaction, epiploic appendagitis 4
• Left-sided urolithiasis (unenhanced CT has near 100% sensitivity and specificity) 1
• Spontaneous retroperitoneal or rectus sheath hemorrhage 4
• Atypical appendicitis with redundant cecum (rare but important) 6, 7

Treatment Algorithm Based on CT Findings

Uncomplicated Diverticulitis (No Abscess, Perforation, or Fistula)

Conservative management without antibiotics is appropriate for immunocompetent patients. 2, 5

• Clear liquid diet advancement with pain control using oral analgesics 5
• Antibiotics for 7 days maximum ONLY in immunocompromised or elderly patients: 2, 5
  • Ertapenem 1 g q24h OR
  • Eravacycline 1 mg/kg q12h 2

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

• Antibiotic therapy alone for 7 days without drainage 2, 5
• Same antibiotic regimens as above 2

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

• Percutaneous drainage combined with antibiotics for 4 days 2, 5
• Stop antibiotics at 4 days in immunocompetent, non-critically ill patients if source control is adequate 5
• Continue up to 7 days in immunocompromised or critically ill patients 5

Septic Shock Present

• 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

Red Flags Requiring Emergency Evaluation

Immediate emergency department evaluation is mandatory for: 2

• Fever with inability to pass gas or stool
• Severe abdominal tenderness with guarding (suggests peritonitis)
• Vomiting
• Bloody stools
• Signs of shock (rapid breathing, rapid heartbeat, confusion)
• Progressively worsening pain over several days

Why These Matter:

• Perforation with peritonitis can lead to fecal contamination, diffuse peritonitis, and septic shock 2
• Complete bowel obstruction can lead to bowel necrosis and perforation if untreated 2
• Abscess or fistula formation requires drainage or surgery 2

Perforation or peritonitis requires emergent surgery. 2

Imaging Modalities: Comparative Analysis

CT with IV Contrast (Preferred)

• Detects complications (perforation, abscess, fistula, obstruction) 1, 2
• Identifies alternative diagnoses with similar presentations 2, 3
• Guides treatment planning by determining disease severity 2, 3
• Reduces hospital admissions by >50% through accurate risk-stratification 2

Ultrasound with Graded Compression

• Can reduce unnecessary CT examinations by identifying patients without surgical abdomen 1
• Operator-dependent and limited in obese patients 1
• Less common in the United States for nongynecologic left lower quadrant pain 1

MRI Abdomen and Pelvis

• Not useful for initial evaluation of acute abdominal pain 1
• Less sensitive for extraluminal air and urinary tract calculi 1, 3
• More time-consuming, requires screening for indwelling devices, more subject to motion artifacts 1
• May be considered if CT was equivocal, with sensitivity of 86-94% and specificity of 88-92% for inflammatory conditions 1, 5

Plain Radiography

• Not useful as initial imaging test because CT is more accurate 1, 3
• May play a role in triage of severely ill patients with surgical abdomen 1

Management of Recurrent/Persistent Pain

When structural pathology has been excluded by CT and colonoscopy, functional bowel disorders become the most likely diagnosis. 5

Considerations for Persistent Symptoms:

• Pain related to bowel movements or dietary triggers points toward irritable bowel syndrome 5
• Cyclical pain in women suggests gynecologic etiology requiring pelvic ultrasound 5
• Weight loss, anemia, or change in bowel habits warrant repeat colonoscopy despite prior normal study 5
• New pericolonic lymphadenopathy >1 cm on repeat imaging suggests malignancy 5

Referral Indications:

• Gastroenterology referral for functional bowel disorder management or persistent symptoms despite conservative measures 5
• Gynecology referral if pelvic ultrasound reveals pathology or high clinical suspicion remains 5

Critical Antibiotic Duration Pitfall

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, obtain repeat imaging to assess for inadequate source control 5