Approach to Left Lower Quadrant Pain
Initial Clinical Assessment
Begin with targeted evaluation focusing on the classic triad of left lower quadrant pain, fever, and leukocytosis, though this triad is present in only 25% of diverticulitis cases. 1
Key Clinical Features to Assess
- Direct tenderness localized to the left lower quadrant 1
- C-reactive protein (CRP) level >50 mg/L - a CRP cutoff of 170 mg/L discriminates severe from mild diverticulitis with 87.5% sensitivity and 91.1% specificity 1
- Absence of vomiting 1
- History of previous diverticulitis episodes 1
- Age and aggravation of pain with movement 1
Clinical diagnosis alone is unreliable, with misdiagnosis rates between 34-68%. 1 When all three criteria (left lower quadrant tenderness, CRP >50 mg/L, absence of vomiting) are present, the diagnosis of diverticulitis has 97% accuracy, but this occurs in only 24% of patients. 1
Imaging Strategy
Primary Imaging Recommendation
CT abdomen and pelvis with IV contrast is the preferred imaging modality for most patients with left lower quadrant pain, with a diagnostic accuracy of 98%. 1, 2, 3 The American College of Radiology rates this as 8/9 (usually appropriate). 1
Benefits of CT with IV Contrast:
- Superior detection of complications including perforation, abscess (≥3 cm requiring drainage), fistula, and obstruction 1, 3
- Identifies alternative diagnoses that mimic diverticulitis clinically 1
- Guides treatment decisions between medical management, interventional drainage, or surgery 1
- Reduces hospital admissions by >50% when performed early in the emergency department 1
- Risk-stratifies patients - colonic wall thickness <9 mm predicts only 19% recurrence risk 1
Special Population Considerations
For premenopausal women with suspected gynecologic pathology, pelvic/transvaginal ultrasound is the preferred initial imaging. 1, 2 This addresses the overlap between gynecologic and gastrointestinal causes of left lower quadrant pain in this population.
For pregnant patients, ultrasound and MRI are preferred over CT to avoid radiation exposure. 3
Alternative Imaging Modalities
- CT without IV contrast (rating 6/9) - acceptable when IV contrast is contraindicated, though less accurate for detecting abscesses 1
- Ultrasound with graded compression - can reduce unnecessary CT examinations but is operator-dependent and limited in obese patients 1
- MRI - has superior soft tissue resolution but is expensive, time-consuming, and less sensitive for extraluminal air 1, 2
- Plain radiography - limited value except for detecting free perforation (pneumoperitoneum) or obstruction 1
When Imaging May Be Deferred
Imaging may not be necessary in select patients with:
- Classic triad of symptoms (left lower quadrant pain, fever, leukocytosis) AND uncomplicated presentation 1
- Previous documented diverticulitis with similar mild recurrent symptoms 1
However, there is a strong trend toward imaging even in these cases to detect complications that would alter management and prevent misdiagnosis. 1
Critical Pitfalls to Avoid
Perforated Colon Cancer Mimicking Diverticulitis
CT findings suggesting cancer rather than diverticulitis include pericolonic lymphadenopathy >1 cm with or without pericolonic edema. 1 When inflammatory changes and mesenteric edema are present without lymphadenopathy, diverticulitis is more likely. 1
Routine colonoscopy after CT-confirmed diverticulitis is not warranted except for age-appropriate screening, unless abscess, perforation, or fistula is present (which increases cancer risk). 1
Atypical Appendicitis
Left lower quadrant pain can rarely represent right-sided appendicitis with a long inflamed appendix projecting leftward, or left-sided appendicitis with situs inversus. 4, 5 CT is critical for establishing this diagnosis when clinical features are uncertain. 4
Other Differential Diagnoses to Consider
- Renal colic and urolithiasis 6, 7
- Epiploic appendagitis 7
- Colitis (infectious, ischemic, inflammatory) 7
- Spontaneous retroperitoneal or rectus sheath hemorrhage 7
- Fecal impaction 7
Treatment Triage Based on Imaging
The WSES classification divides acute diverticulitis into uncomplicated and complicated categories based on CT findings: 1
Uncomplicated Diverticulitis
- Infection limited to colon wall without peritoneal extension 1
- Outpatient medical management with antibiotics 1
Complicated Diverticulitis
- Stage 1A/B: Pericolic air/fluid or abscess ≤4 cm - medical management ± antibiotics 1
- Stage 2A: Abscess >4 cm - percutaneous drainage indicated 1
- Stage 2B: Distant gas (>5 cm from inflamed segment) - consider surgery 1
- Stage 3: Diffuse fluid without distant free gas - surgery likely needed 1
- Stage 4: Diffuse fluid with distant free gas - emergent surgery for peritonitis 1