In a pregnant patient with right upper quadrant pain, what is the differential diagnosis and initial workup?

Right Upper Quadrant Pain in Pregnancy: Differential Diagnosis and Workup

Initial Imaging Approach

Begin immediately with ultrasound of the abdomen as the mandatory first-line imaging study for all pregnant patients with right upper quadrant pain, followed by MRI without IV contrast if ultrasound is non-diagnostic, and reserve CT only for life-threatening situations where other modalities fail or are unavailable. 1

• Ultrasound is preferred as the initial study due to excellent specificity (99.2%), no ionizing radiation, rapid availability, ability to evaluate gallbladder/bile ducts, and capacity to identify alternative diagnoses, though sensitivity is limited (12.5% for appendicitis) particularly in later pregnancy 1, 2
• Ultrasound visualization of the appendix declines significantly with advancing gestation: approximately 75% in the first trimester versus only 37% by the third trimester 1
• If ultrasound is non-diagnostic or equivocal, proceed immediately to MRI abdomen and pelvis without IV contrast, which demonstrates pooled sensitivity of 96.8%, specificity of 99.2%, and negative predictive value of 99.7% 1
• MRI visualizes the appendix in 70-80% of cases compared to only 7% with ultrasound, and identifies alternative diagnoses in 10.1-43% of cases 1

Critical Red Flags Requiring Urgent Escalation

Do not delay imaging or surgical consultation when any of the following are present, as complications carry significant maternal and fetal morbidity and mortality: 1

• Fever, tachycardia, or signs of sepsis suggesting pyelonephritis, cholangitis, or complicated appendicitis 3, 1
• Hemodynamic instability requiring immediate intervention 1
• Significant leukocytosis with left shift indicating severe infection or inflammation 1
• Jaundice with fever and chills suggesting acute cholangitis 1
• Refractory pain despite conservative measures 3

Differential Diagnosis for RUQ Pain in Pregnancy

Pregnancy-Specific Conditions

• Acute cholangitis: Suspect when RUQ pain is accompanied by jaundice, fever, chills, elevated inflammatory markers, and biliary dilatation on imaging 1

Non-Pregnancy-Specific Conditions (Most Common)

• Appendicitis: The most common cause of abdominal pain requiring emergent surgery in pregnant patients; the appendix migrates superiorly with advancing gestation, potentially causing RUQ pain in later trimesters rather than classic right lower quadrant location 1, 4
• Acute cholecystitis/cholelithiasis: Most common biliary cause of RUQ pain, best evaluated initially with ultrasound 2, 5
• Urolithiasis with right-sided hydronephrosis: Can present with RUQ or right flank pain radiating anteriorly, often with fever and pyuria 1
• Pyelonephritis: Right-sided kidney infection presenting with flank pain that may radiate to RUQ 3, 1
• Acute pancreatitis: Should be considered with upper quadrant pain with or without nausea/vomiting; gallstones are the most common cause in pregnancy 6

Laboratory Evaluation

Obtain the following laboratory studies to support diagnosis and guide management: 1

• Complete blood count with differential to assess for leukocytosis and left shift
• Comprehensive metabolic panel including liver function tests (elevated transaminases suggest hepatobiliary pathology)
• Lipase (elevated in pancreatitis)
• Urinalysis with culture (pyuria indicates urinary tract infection or nephrolithiasis)

Role of CT Imaging

Reserve CT abdomen and pelvis for life-threatening situations where MRI is unavailable or both ultrasound and MRI remain equivocal. 1

• Maternal health takes absolute priority, and CT should not be withheld if the clinical situation is life-threatening and maternal survival is at risk 1
• Low-dose CT with oral contrast can be considered when MRI is not immediately available 7

Timing of Surgical Intervention

If appendicitis is confirmed, surgery should be performed within 24 hours to minimize risk of perforation. 1

• Pregnant women are more likely to present with complicated (perforated or gangrenous) appendicitis, and perforation carries higher risk of fetal loss 4
• Immediate surgical or urologic consultation is warranted for confirmed appendicitis, hemodynamic instability, or any surgical emergency identified on imaging 7, 1

Common Pitfalls to Avoid

• Do not assume typical pain location: Appendicitis pain may not correlate with appendiceal position in pregnancy due to superior migration with advancing gestation 1
• Do not stop at negative ultrasound: Given the limited sensitivity (12.5%) of ultrasound for appendicitis in pregnancy, proceed to MRI if clinical suspicion persists 1
• Do not delay intervention: Perforation and sepsis carry significant maternal and fetal morbidity; prompt diagnosis and treatment are essential 4, 1