What is the appropriate management for a pregnant patient presenting with right lower quadrant (RLQ) pain and a positive pregnancy test?

Management of Pregnant Patients with Right Lower Quadrant Pain

Begin with ultrasound as the initial imaging modality, followed by MRI without IV contrast if ultrasound is non-diagnostic, reserving CT only for life-threatening situations where other modalities are unavailable or inconclusive. 1

Initial Diagnostic Approach

Clinical Assessment

• Evaluate for appendicitis as the primary concern, which is the most common indication for non-obstetric surgery during pregnancy, occurring in approximately 1 in 500-635 pregnancies, most frequently in the second trimester 2
• Assess for classic appendicitis presentation: abdominal pain migrating to the right lower quadrant, though recognize that anatomical changes during pregnancy may alter typical presentations 2
• Document gestational age carefully, as this significantly impacts both imaging strategy and diagnostic accuracy—patients requiring surgery typically have higher gestational age, elevated leukocyte counts, and neutrophil shift compared to those managed conservatively 3
• Consider the full differential diagnosis including ovarian torsion, urolithiasis, ectopic pregnancy complications, and other obstetric emergencies 4

Laboratory Findings

• Interpret leukocytosis cautiously, as physiologic pregnancy-related leukocytosis must be distinguished from pathologic causes 5
• Higher leukocyte counts and neutrophil shifts correlate with surgical pathology in pregnant patients with RLQ pain 3

Imaging Algorithm

First-Line: Ultrasound

• Ultrasound abdomen is the mandatory initial imaging study for all pregnant patients with RLQ pain 1
• Ultrasound sensitivity for appendicitis is inversely correlated with gestational age—it performs better in first trimester (used in 81.6% of cases) compared to second (58.1%) and third trimesters (57.9%) 3
• US demonstrates only 12.5% sensitivity but 99.2% specificity for appendicitis in pregnancy, with appendix visualization rates of only 7% 1
• Despite limited sensitivity, ultrasound successfully identifies obstetric causes of pain and can detect alternative diagnoses in 2.6% of cases 1

Second-Line: MRI Without IV Contrast

• If ultrasound is non-diagnostic or equivocal, proceed immediately to MRI abdomen and pelvis without IV contrast 1
• MRI demonstrates superior diagnostic performance with pooled sensitivity of 96.8%, specificity of 99.2%, accuracy of 99.0%, PPV of 92.4%, and NPV of 99.7% in a multi-institutional study of 709 pregnant women 1
• MRI visualizes the appendix in 70-80% of cases compared to only 7% with ultrasound 1
• MRI identifies alternative diagnoses in 10.1-43% of cases, providing critical diagnostic information beyond appendicitis 1
• The appendix remains non-visualized in approximately 29-31% of MRI studies, which is not necessarily abnormal 1

Multimodality Strategy Performance

• A sequential approach using ultrasound followed by MRI for non-diagnostic cases achieves sensitivity of 100%, specificity of 98.3%, PPV of 80%, and NPV of 100% 1
• This strategy reduced negative appendectomy rates from 55% to 29% (a 47% decrease) following MRI implementation 1

Third-Line: CT Consideration

• CT abdomen and pelvis should be reserved for situations where MRI is unavailable or results remain equivocal after both ultrasound and MRI 1
• Low-dose CT (LDCT) with oral contrast can be considered when MRI is not immediately available, demonstrating 83% conclusive diagnosis rate for appendicitis 1
• CT maintains high sensitivity and specificity throughout all trimesters of pregnancy, unlike ultrasound 3
• Do not withhold CT imaging if the clinical situation is life-threatening and maternal survival is at risk—maternal health takes absolute priority 6
• CT was used in only 8.7% of cases following equivocal ultrasound and MRI in one multimodality algorithm 1

Critical Management Principles

Timing and Urgency

• Do not delay imaging or surgical intervention in pregnant patients with suspected appendicitis, as perforation carries significant maternal and fetal morbidity and mortality 6, 4
• Delays in diagnosis and treatment lead to adverse outcomes for both mother and fetus 4
• Patients with higher gestational age, elevated leukocyte counts, and neutrophil shifts are more likely to require surgery and should be expedited 3

Surgical Decision-Making

• Appendectomy remains the definitive treatment when appendicitis is confirmed 2
• Laparotomy is the standard surgical approach, as the feasibility of laparoscopic surgery in pregnancy remains controversial 2
• Immediate surgical consultation is warranted for confirmed appendicitis, hemodynamic instability, or any surgical emergency identified on imaging 6

Common Pitfalls to Avoid

• Do not rely on ultrasound alone in second and third trimester pregnancies—sensitivity decreases significantly with advancing gestational age, and MRI should be obtained promptly for non-diagnostic studies 3
• Do not assume normal leukocyte counts exclude pathology—while elevated counts correlate with surgical disease, physiologic pregnancy-related leukocytosis complicates interpretation 5, 3
• Do not limit imaging to the pelvis only—7% of patients have pathology outside the pelvis requiring surgery, and focused pelvic-only imaging would reduce sensitivity from 99% to 88% 7
• Do not delay MRI waiting for ultrasound to be "more conclusive"—if initial ultrasound is non-diagnostic, proceed directly to MRI rather than repeating ultrasound 1