Abdominal Ultrasound is the Most Appropriate Initial Diagnostic Imaging
For a patient presenting with recurrent right upper quadrant pain, jaundice, and elevated liver function tests and bilirubin, abdominal ultrasound should be performed first as the initial imaging modality. 1
Rationale for Ultrasound as First-Line Imaging
The American College of Radiology explicitly recommends ultrasound as the initial evaluation for patients presenting with jaundice and suspected biliary obstruction, with specificities ranging between 71% to 97% for confirming or excluding mechanical obstruction. 1
Ultrasound can detect biliary dilatation (the critical first step in determining whether obstruction is present), identify gallstones with 96% accuracy, assess gallbladder wall thickening and pericholecystic fluid, and evaluate both intrahepatic and extrahepatic bile ducts. 1
Ultrasound is rated 9/9 (usually appropriate) by the American College of Radiology for right upper quadrant pain evaluation and serves as the primary imaging modality for assessment of acute RUQ pain with both high sensitivity and specificity for demonstrating gallstones, biliary dilatation, and features suggesting acute inflammatory disease. 1, 2
Practical advantages include shorter study time, portability, lack of radiation exposure, and lower cost compared to CT or MRI, making it ideal for initial evaluation. 1
Algorithmic Approach After Initial Ultrasound
If ultrasound demonstrates biliary dilatation or is equivocal, proceed immediately to MRCP to comprehensively evaluate the biliary tree for stones, strictures, or obstruction. 1
MRCP has 85-100% sensitivity and 90% specificity for detecting choledocholithiasis and is superior to CT for assessing suspected biliary sources of RUQ pain, providing comprehensive visualization of the entire hepatobiliary system. 1, 3
MRCP can identify the level and cause of biliary obstruction with accuracy of 91-100%, including stones, strictures, masses, and lymph nodes—critical for patients with elevated LFTs indicating biliary obstruction or cholestasis. 1
Why Not CT or MRCP First?
CT is less sensitive than ultrasound for initial biliary evaluation (only ~75% sensitivity for detecting gallstones) and exposes patients to radiation without clear advantage as a first-line test. 1, 3
The American College of Radiology Appropriateness Criteria explicitly recommend ultrasound first, followed by advanced imaging based on ultrasound findings, rather than proceeding directly to MRCP or CT. 1
CT with IV contrast should be reserved for critically ill patients, those with peritoneal signs, or when there is suspicion of complications beyond simple biliary obstruction. 1
Critical Clinical Caveats
Elevated LFTs and bilirubin in this patient indicate biliary obstruction or cholestasis, which requires anatomic visualization of the bile ducts—ultrasound provides this initial assessment and guides whether MRCP is needed. 1
Do not skip ultrasound and proceed directly to advanced imaging (MRI or CT) unless the patient is too unstable for ultrasound or there is a specific contraindication. 4
In critically ill patients, gallbladder abnormalities are common even in the absence of acute cholecystitis, which may limit ultrasound's diagnostic utility in this specific population. 1
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