What is the appropriate workup and management for a patient presenting with left lower quadrant abdominal pain?

Left Lower Quadrant Abdominal Pain: Workup and Management

Initial Imaging Strategy

CT abdomen and pelvis with IV contrast is the preferred initial imaging test for most patients presenting with left lower quadrant pain, providing comprehensive diagnostic accuracy for the broad differential diagnosis including diverticulitis, perforation, abscess, malignancy, and vascular pathology. 1, 2

Patient-Specific Imaging Modifications

• Premenopausal women: Begin with pelvic/transvaginal ultrasound if gynecologic pathology (ovarian torsion, ectopic pregnancy, tubo-ovarian abscess) is clinically suspected, as these conditions present with similar symptoms to gastrointestinal causes 1, 2
• Elderly patients (≥75 years): CT with IV contrast remains the gold standard, though unenhanced CT provides reasonable accuracy (64-68%) if contrast is contraindicated 1, 3
• Suspected urolithiasis: Unenhanced CT is preferred, with sensitivity and specificity near 100% for urinary tract calculi 1

Critical Clinical Features to Assess

High-Risk Indicators Requiring Urgent CT

• Fever with leukocytosis: The classic triad of left lower quadrant pain, fever, and leukocytosis strongly suggests diverticulitis, but imaging is essential to assess severity and complications 1
• Peritoneal signs: Rebound tenderness, guarding, or rigidity indicate potential perforation or abscess requiring immediate surgical evaluation 1
• Elderly presentation: Only 50% of elderly patients have pain localized to lower quadrants and only 17% have fever, making clinical diagnosis unreliable 3

When Imaging May Be Deferred

Imaging may not be necessary in patients with known diverticulitis presenting with mild recurrent symptoms consistent with prior episodes, though this should be approached cautiously 1

Why CT with IV Contrast is Superior

• Detects critical complications: Identifies small volumes of extraluminal air indicating perforation (which has significant surgical implications and mortality risk), abscess formation, fistula, and bowel wall thickening 1, 3
• Evaluates disease severity: IV contrast improves characterization of bowel wall pathology, pericolic abnormalities, vascular pathology, and intraabdominal fluid collections 1
• Identifies alternative diagnoses: CT alters diagnosis in nearly half of cases, detecting unexpected findings like malrotation with atypical appendicitis, perforated carcinoma, epiploic appendicitis, or renal pathology 4, 5, 6
• Prognostic value: Mortality in diverticulitis increases dramatically with age (1.6% in <65 years, 9.7% in 65-79 years, 17.8% in >80 years), making accurate initial diagnosis critical 3

Imaging Modalities to Avoid

• Plain radiography: Not useful as initial imaging because CT is far more sensitive and specific for all relevant pathology including extraluminal air, bowel obstruction, and urolithiasis 1
• MRI: Less sensitive for extraluminal air and urinary calculi, more time-consuming, and more subject to motion artifacts in symptomatic patients 1, 2
• Fluoroscopic contrast enema: Less sensitive than CT for diverticulitis and provides no value for evaluating gynecologic or urologic conditions 1
• Transabdominal ultrasound: Limited utility in the United States for nongynecologic left lower quadrant pain; highly operator-dependent and may miss critical findings that CT detects 1, 7

Common Pitfalls and How to Avoid Them

Atypical Presentations

• Left-sided appendicitis: Rare but occurs with situs inversus totalis or redundant/loosely attached cecum; CT is essential for diagnosis 4, 6
• Long appendix projecting into left lower quadrant: Can cause left lower quadrant pain with right-sided appendicitis; failure to image may result in perforation and abscess 4
• Elderly patients: Clinical examination alone has misdiagnosis rates of 34-68%, and normal inflammatory markers do not exclude serious pathology (39% of complicated diverticulitis cases have C-reactive protein <175 mg/L) 3

Contrast Administration Considerations

• Oral or colonic contrast: May be helpful for bowel luminal visualization but is not mandatory 1
• Renal function: Check creatinine before contrast administration; avoid gadolinium-based contrast in patients with GFR <30 mL/min/1.73 m² 1

Differential Diagnosis by CT Findings

Diverticulitis (Most Common in Elderly)

• CT findings: Pericolonic fat stranding, colonic wall thickening, diverticula at epicenter of inflammation 1, 7
• Complications: Abscess (rim-enhancing fluid collection), fistula, perforation (extraluminal air), peritonitis 1
• Management: Mild cases treated medically; severe cases with complications require surgical consultation 1

Alternative Diagnoses

• Renal colic/pyelonephritis: Unenhanced CT for stones; contrast-enhanced for infection 7, 5
• Gynecologic disorders: Ovarian torsion, ectopic pregnancy, tubo-ovarian abscess (ultrasound preferred in premenopausal women) 1, 2
• Epiploic appendicitis: Self-limited inflammatory condition 7
• Perforated carcinoma: CT identifies mass with perforation 7
• Inflammatory bowel disease: CT shows bowel wall thickening and inflammation 7

Management Algorithm Based on CT Results

• Uncomplicated diverticulitis: Outpatient antibiotics and bowel rest for mild cases; admission for severe cases 1
• Complicated diverticulitis (abscess, perforation, fistula): Surgical consultation; percutaneous drainage for accessible abscesses 1
• Large-volume extraluminal air: Emergent surgical evaluation for likely perforation 1
• Alternative diagnosis identified: Disease-specific management (appendectomy for appendicitis, urology consultation for stones, gynecology for ovarian pathology) 4, 5, 6