What is the appropriate workup for a patient presenting with left lower quadrant (LLQ) abdominal pain?

Workup for Left Lower Quadrant Abdominal Pain

CT abdomen and pelvis with IV contrast is the preferred initial imaging study for most patients presenting with left lower quadrant pain, achieving 98% diagnostic accuracy and identifying life-threatening complications that determine treatment. 1

Initial Clinical Evaluation

Begin by assessing for the classic triad of left lower quadrant pain, fever, and leukocytosis—though this appears in only 25% of diverticulitis cases, making clinical diagnosis alone unreliable with misdiagnosis rates of 34-68%. 1, 2

Key clinical features to document:

• Duration and character of pain (constant vs. intermittent, sharp vs. dull) 2
• Fever or chills 1
• Ability to pass gas and stool 2
• Presence of vomiting, bloody stools, or signs of peritonitis 2
• Relationship to bowel movements or menstrual cycle 3

Laboratory workup:

• Complete blood count with differential 1
• C-reactive protein (CRP >50 mg/L combined with left lower quadrant tenderness and absence of vomiting yields 97% accuracy, though this occurs in only 24% of patients) 2
• Pregnancy test in women of reproductive age before imaging 2

Imaging Strategy

Primary Recommendation: CT Abdomen and Pelvis with IV Contrast

This is rated 8/9 (usually appropriate) by the American College of Radiology and should be the first-line imaging for most patients. 1, 2

Why CT with IV contrast is superior:

• Detects bowel wall pathology, pericolic abnormalities, vascular pathology, and fluid collections 1
• Identifies complications requiring intervention: abscess, perforation, fistula, obstruction 1
• Establishes alternative diagnoses (cancer, inflammatory bowel disease, urologic pathology) 1
• Reduces hospital admissions by >50% through accurate risk stratification 2
• Sensitivity and specificity approaching 100% for sigmoid diverticulitis 2

CT without IV contrast is acceptable when IV contrast is contraindicated (renal insufficiency, severe contrast allergy), though it has reduced accuracy for detecting abscesses—rated 6/9 by the American College of Radiology. 1

Special Population Considerations

For premenopausal women with suspected gynecologic pathology:

• Start with pelvic/transvaginal ultrasound if clinical concern exists for ovarian torsion, ectopic pregnancy, or tubo-ovarian abscess 1, 2
• Proceed to CT if ultrasound is negative but symptoms persist 1

For suspected urolithiasis:

• Unenhanced CT has near 100% sensitivity and specificity for urinary tract calculi 1

Alternative Imaging Modalities

Transabdominal ultrasound can reduce unnecessary CT examinations by identifying uncomplicated diverticulitis in patients without surgical abdomen, but it is operator-dependent and less commonly used in the United States for nongynecologic left lower quadrant pain. 1

MRI abdomen and pelvis is not useful for initial evaluation—it is less sensitive for extraluminal air and urinary calculi, more time-consuming, and more subject to motion artifacts in symptomatic patients. 1

Plain radiography is not useful as initial imaging because CT is more accurate, though it may play a limited role in triaging severely ill patients with suspected free air or bowel obstruction. 1

Critical Imaging Findings and Their Implications

On CT, look for:

• Bowel wall thickening with pericolonic fat stranding (suggests diverticulitis) 2
• Extraluminal gas or intra-abdominal fluid (indicates perforation) 2
• Abscess size and location (determines drainage strategy: <3-4 cm = antibiotics alone; ≥4 cm = percutaneous drainage) 1, 2
• Pericolonic lymphadenopathy >1 cm (suggests cancer rather than diverticulitis) 2, 3

Red Flags Requiring Emergency Evaluation

Immediate emergency department evaluation is mandatory for:

• Fever with inability to pass gas or stool 2
• Severe abdominal tenderness with guarding or rebound 2
• Persistent vomiting 2
• Bloody stools 2
• Signs of shock (hypotension, tachycardia, altered mental status) 2
• Progressively worsening pain over several days 2

These findings suggest perforation with peritonitis, abscess requiring drainage, complete bowel obstruction, or sepsis—all requiring urgent intervention. 2

Common Pitfalls to Avoid

Do not assume diverticulitis based on clinical presentation alone—misdiagnosis rates are 34-68%, and alternative diagnoses (cancer, inflammatory bowel disease, gynecologic pathology) require different management. 1

Do not skip imaging in patients with prior diverticulitis—complications develop in 15% of cases, and 5% of presumed diverticulitis cases are actually unsuspected carcinoma. 4

Do not order routine colonoscopy after CT-confirmed diverticulitis unless abscess, perforation, or fistula is present, or age-appropriate screening is due. 2

In women of reproductive age, always obtain pregnancy testing before CT to avoid unnecessary radiation exposure and consider gynecologic causes. 2

Atypical appendicitis can present with left lower quadrant pain in cases of redundant cecum or situs inversus totalis—CT will establish the correct diagnosis. 5, 6, 7

When Imaging May Not Be Required

Patients with typical symptoms of diverticulitis, prior history of diverticulitis with similar symptoms, and no evidence of complications may be treated medically without imaging. 1 However, there is a trend toward greater use of imaging to confirm diagnosis, evaluate disease extent, and detect complications before deciding on treatment. 1