What is the recommended urgency for assessing an 18-week pregnant patient with a 2-week history of right upper quadrant (RUQ) pain?

Urgent Assessment Required Within 24 Hours

An 18-week pregnant patient with 2 weeks of right upper quadrant (RUQ) pain requires urgent evaluation within 24 hours, with immediate assessment if any red flag symptoms develop. While the 2-week duration suggests a subacute process rather than an acute surgical emergency, the persistence of symptoms in pregnancy warrants prompt diagnostic workup to exclude serious hepatobiliary, appendiceal, or other surgical pathology that could threaten maternal and fetal health. 1

Immediate Red Flags Requiring Emergency Assessment

If any of the following are present, the patient needs immediate (same-day) evaluation rather than urgent (24-hour) assessment:

• Fever, tachycardia, or signs of sepsis 1
• Hemodynamic instability 1
• Severe, persistent, or progressively worsening pain 2
• Vaginal bleeding 2
• Jaundice with fever and chills (suggests acute cholangitis) 3
• Significant leukocytosis with left shift 1

Rationale for Urgent (Not Emergent) Assessment

The 2-week duration of symptoms indicates this is not an acute surgical abdomen requiring immediate intervention, but several considerations mandate prompt evaluation:

• Appendicitis remains a critical consideration even with RUQ pain at 18 weeks, as the appendix migrates superiorly with advancing gestation and can present with atypical pain location 1, 4
• Acute cholecystitis and cholangitis are common causes of RUQ pain in pregnancy and require timely diagnosis to prevent complications 3
• Delayed diagnosis carries significant maternal and fetal morbidity, particularly for conditions like appendicitis where perforation risk increases with diagnostic delay 1, 4

Initial Diagnostic Approach

Laboratory Evaluation

Obtain the following tests at the initial visit:

• Complete blood count with differential to assess for leukocytosis and left shift 1
• Comprehensive metabolic panel and liver function tests to identify hepatobiliary pathology 1
• Lipase to evaluate for pancreatitis 1
• Urinalysis with culture to exclude urinary tract infection or nephrolithiasis 1
• Coagulation panel including fibrinogen (fibrinogen <200 mg/dL is a red flag requiring admission) 5

Imaging Algorithm

Step 1: Ultrasound abdomen is the mandatory initial imaging study for all pregnant patients with RUQ pain 3, 1, 4

• Ultrasound has excellent specificity (99.2%) but limited sensitivity (12.5%) for appendicitis in pregnancy 1, 4
• It effectively identifies gallstones, cholecystitis, and biliary dilatation 3
• Results are timely, portable, and avoid radiation exposure 3

Step 2: MRI abdomen/pelvis without IV contrast if ultrasound is non-diagnostic or equivocal 3, 1, 4

• MRI demonstrates superior diagnostic performance with sensitivity of 96.8%, specificity of 99.2%, and negative predictive value of 99.7% for appendicitis 1, 4
• MRI visualizes the appendix in 70-80% of cases compared to only 7% with ultrasound 1, 4
• MRI identifies alternative diagnoses in 10.1-43% of cases 1
• Do not delay MRI if ultrasound is equivocal—prompt imaging prevents diagnostic delay 1, 4

Step 3: CT abdomen/pelvis should be reserved only for life-threatening situations where MRI is unavailable or both ultrasound and MRI remain equivocal 1, 4

• Maternal health takes absolute priority, and CT should not be withheld if maternal survival is at risk 4, 5

Key Differential Diagnoses to Consider

Pregnancy-Specific Conditions

• Acute cholangitis: RUQ pain with jaundice, fever, chills, elevated inflammatory markers, and biliary dilatation 3, 1

Non-Pregnancy-Specific Conditions

• Appendicitis: Most common cause of abdominal pain requiring emergent surgery in pregnancy; can present with RUQ pain at 18 weeks due to superior appendiceal migration 1, 4
• Acute cholecystitis: Most common diagnosable cause of RUQ pain in emergency settings 3, 6
• Urolithiasis with right-sided hydronephrosis or pyelonephritis: RUQ or right flank pain with fever and pyuria 1

Common Pitfalls to Avoid

• Do not delay imaging or surgical consultation in pregnant patients with suspected surgical emergencies, as perforation (particularly appendiceal) carries significant maternal and fetal morbidity 1, 4, 5
• Do not assume RUQ pain excludes appendicitis at 18 weeks gestation—the appendix migrates superiorly and can cause atypical pain location 1, 4
• Do not withhold indicated radiographic studies including CT due to concerns about fetal radiation exposure when maternal health is at risk 5
• Do not rely solely on ultrasound if clinical suspicion remains high despite negative findings—proceed immediately to MRI 1, 4

Disposition Criteria

Admit for 24-hour observation if any of the following are present: 1

• Uterine tenderness or significant abdominal pain
• Vaginal bleeding
• Sustained contractions
• Atypical or abnormal fetal heart rate pattern (if fetal monitoring initiated)
• High-risk mechanism if trauma-related
• Serum fibrinogen <200 mg/dL