What's the best approach for a patient with sharp left lower quadrant pain and a history of gastrointestinal or gynecological issues?

Sharp Left Lower Quadrant Pain: Diagnostic Approach

CT abdomen and pelvis with IV contrast is the preferred initial imaging test for most patients presenting with sharp left lower quadrant pain, as it provides 98% diagnostic accuracy, identifies complications, and detects alternative diagnoses. 1, 2

Initial Imaging Strategy

Standard Adult Patients

• Order CT abdomen and pelvis with IV contrast as first-line imaging for suspected diverticulitis or undifferentiated left lower quadrant pain 1, 2
• CT with IV contrast is superior to non-contrast CT for detecting abscesses, characterizing bowel wall abnormalities, and identifying inflammatory changes 1, 3
• Low-dose CT protocols can reduce radiation exposure by 75-90% while maintaining diagnostic accuracy 1

Premenopausal Women

• Begin with transvaginal/pelvic ultrasound if gynecologic pathology is suspected based on clinical presentation 2
• If ultrasound is negative or inconclusive, proceed to CT abdomen and pelvis with IV contrast to evaluate non-gynecologic causes 2
• Ultrasound alone may miss important gastrointestinal pathology that CT would detect 2

Alternative Imaging When CT Contraindicated

• MRI abdomen and pelvis with gadolinium is the preferred alternative if IV contrast is contraindicated, with 86-94% sensitivity and 88-92% specificity for diverticulitis 1, 3
• MRI has limitations including difficulty detecting extraluminal air, longer acquisition time, higher cost, and reduced sensitivity for urinary calculi 2

Role of Ultrasound in Diverticulitis

When to Consider Ultrasound First

• European guidelines support ultrasound as first-line imaging for suspected diverticulitis, with >90% sensitivity and positive predictive value 1
• Ultrasound diagnostic criteria include: colonic wall thickening >5 mm, inflamed diverticulum surrounded by hyperechoic fat, and noncompressible hyperechoic pericolic tissue 1

Limitations of Ultrasound

• Accuracy is lower than CT, especially in obese patients and distal sigmoid diverticulitis 1
• Requires significant operator expertise (minimum 500 examinations for competency) 1
• Lower specificity than CT and less likely to identify alternative diagnoses 1
• If ultrasound is negative or inconclusive, proceed to CT 1

CT Findings That Guide Management

Risk Stratification for Complications

• CT identifies features predicting need for surgery or treatment failure: longer segments of involved colon, retroperitoneal abscess, extraluminal air, abscess size, and size of inflamed diverticula 1
• Small-volume pericolic air (<5 cm from affected segment) can be managed medically 1
• Spilled feces generally requires surgical intervention 1

Abscess Management

• CT or CT-fluoroscopic guidance allows percutaneous drainage of abscesses, potentially avoiding surgery 1
• IV contrast improves detection and characterization of abscesses by distinguishing them from adjacent bowel 1

Red Flags Requiring Immediate Intervention

Obtain urgent imaging and surgical consultation if patient presents with: 3

• Fever combined with inability to pass gas or stool
• Severe abdominal tenderness with guarding or rebound peritonitis
• Vomiting with progressive worsening pain
• Bloody stools
• Signs of shock or toxic appearance

Common Pitfalls to Avoid

• Do not rely on plain radiography as it has extremely limited sensitivity for left lower quadrant pathology 1, 2
• Do not attribute pain to incidental diverticulosis seen on imaging; diverticulosis without inflammation does not cause acute pain 3
• Do not order non-contrast CT when contrast is available, as diagnostic accuracy drops significantly without IV contrast 3
• Consider atypical presentations such as left-sided appendicitis in patients with situs inversus or midgut malrotation 4
• Clinical examination alone has misdiagnosis rates of 34-68%, making imaging essential 3

Follow-Up After Negative CT

• Obtain laboratory studies including CBC with differential and C-reactive protein to assess for occult inflammation 3
• Arrange close follow-up within 24-48 hours to reassess for evolving symptoms 3
• Provide return precautions: fever development, worsening pain, inability to pass gas/stool, or new vomiting 3
• Do not order routine colonoscopy unless patient is due for age-appropriate screening or CT shows abnormal pericolic lymph nodes 3