What is the best initial diagnostic imaging for a patient with intermittent right upper quadrant (RUQ) pain, nausea, jaundice, and elevated bilirubin and liver function tests (LFTs)?

Best Initial Diagnostic Imaging for RUQ Pain with Jaundice and Elevated LFTs

Ultrasound of the abdomen is the best initial diagnostic imaging test for this patient, followed by MRCP if ultrasound is negative or equivocal. 1

Algorithmic Approach

Step 1: Start with Ultrasound

• The American College of Radiology explicitly recommends ultrasound as the initial evaluation for jaundice with suspected biliary obstruction, with specificities ranging between 71% to 97% for confirming or excluding mechanical obstruction 1
• Ultrasound detects biliary dilatation with high accuracy, which is the critical first step in determining whether obstruction is present and guides all subsequent management decisions 1
• Ultrasound identifies gallstones with 96% accuracy, assesses gallbladder wall thickening and pericholecystic fluid, evaluates intrahepatic and extrahepatic bile ducts, and can detect alternative diagnoses such as cirrhosis (sensitivity 65-95%, positive predictive value 98%) 1
• Ultrasound is fast, portable, lacks radiation exposure, and costs significantly less than CT or MRI, making it ideal for initial evaluation 1
• Ultrasound should be used as the first-line imaging modality for RUQ pain as it allows differentiation of medical and surgical causes and in many circumstances is sufficient to guide patient management 2

Step 2: Proceed to MRCP Based on Ultrasound Findings

• If ultrasound demonstrates biliary dilatation or is equivocal, proceed directly to MRCP for comprehensive evaluation of the biliary tree 1
• MRCP has sensitivity of 85-100% and specificity of 90% for detecting choledocholithiasis and biliary obstruction 1
• MRCP visualizes the common bile duct and cystic duct far better than ultrasound, which is critical when evaluating for bile duct stones or obstruction causing elevated LFTs 1
• MRCP can identify the level and cause of biliary obstruction with accuracy of 91-100%, including stones, strictures, masses, and lymph nodes 1
• The American College of Radiology recommends MRCP as the preferred imaging modality over HIDA scan for detecting choledocholithiasis and biliary obstruction 1

Why Not CT Abdomen?

• CT is less sensitive than ultrasound for initial biliary evaluation and exposes patients to radiation without clear advantage as a first-line test 1
• CT has sensitivity between only 39% to 75% for detection of gallstones compared with ultrasound 1
• Many gallstones are not radiopaque (up to 80% are noncalcified), severely limiting CT's utility for detecting the most common cause of biliary obstruction 1
• CT should be reserved for critically ill patients with peritoneal signs or suspected complications beyond simple biliary obstruction (such as emphysematous cholecystitis, gallbladder perforation, or abscess formation), not for initial diagnostic evaluation 1

Clinical Context for This Patient

• The presentation of intermittent RUQ pain with nausea, jaundice, and elevated bilirubin/LFTs strongly suggests biliary obstruction, most likely from choledocholithiasis 1
• Elevated LFTs indicate biliary obstruction or cholestasis, which requires anatomic visualization of the bile ducts—something ultrasound can initiate and MRCP can definitively characterize 1
• A normal CBD caliber on ultrasound has a 95-96% negative predictive value for choledocholithiasis, which can help risk-stratify the patient 1
• Ultrasound has limitations for visualizing the distal common bile duct due to overlying bowel gas, with sensitivities for CBD stone detection ranging from only 22.5% to 75%, which is why MRCP is needed when ultrasound is equivocal 1

Important Caveats

• Do not skip ultrasound and go directly to MRCP or CT—ultrasound provides essential initial information at lower cost and without radiation, and may be sufficient to guide management 1, 2
• The sonographic Murphy sign has relatively low specificity for acute cholecystitis and is unreliable if the patient has received pain medication prior to imaging 1
• Over one-third of patients initially thought to have acute cholecystitis actually have RUQ pain attributable to other causes, which ultrasound can help identify 3
• MRCP sequences themselves (heavily T2-weighted imaging) provide diagnostic information for detecting bile duct stones with no need for IV contrast, though contrast can be added to evaluate for complications like acute cholangitis 1