What could be causing a gnawing dull ache in the right upper quadrant?

Right Upper Quadrant Gnawing Dull Ache: Differential Diagnosis and Workup

Most Likely Diagnosis

Acute cholecystitis is the most common cause of right upper quadrant pain and should be your primary diagnostic consideration, though more than one-third of patients with acute RUQ pain will have an alternative diagnosis. 1, 2

Differential Diagnosis

The gnawing dull ache pattern suggests several key possibilities:

• Biliary disease (most common): Acute cholecystitis, chronic cholecystitis, cholelithiasis, choledocholithiasis, biliary dyskinesia 1, 3
• Hepatic pathology: Hepatitis, hepatic abscess, hepatic mass, hepatic congestion 4, 5
• Pancreatic disease: Pancreatitis and its sequelae 4
• Gastrointestinal causes: Peptic ulcer disease, duodenal perforation, colonic pathology at hepatic flexure 6, 4
• Renal pathology: Pyelonephritis, renal obstruction, nephrolithiasis 4, 5
• Non-GI causes: Pneumonia (referred pain), pulmonary embolism, myocardial ischemia, musculoskeletal pain 5, 7

Recommended Diagnostic Algorithm

Step 1: Initial Imaging

Order right upper quadrant ultrasound immediately as your first-line imaging study (rated 9/9 "usually appropriate" by the American College of Radiology). 1, 3, 6

Ultrasound has 96% accuracy for detecting gallstones and 81% sensitivity with 83% specificity for acute cholecystitis. 1, 3, 6 It successfully identifies multiple causes of RUQ pain including renal infection, pancreatitis, and even remote problems like pneumonia. 4

Key ultrasound findings to assess:

• Gallstones or sludge 1
• Gallbladder wall thickening (>3mm) 3
• Pericholecystic fluid 3
• Sonographic Murphy sign (focal tenderness over gallbladder) 1
• Bile duct dilatation 3, 2
• Hepatic parenchymal abnormalities 6

Step 2: Laboratory Testing

Order a complete metabolic panel including liver function tests (AST, ALT, alkaline phosphatase, bilirubin) and complete blood count. 6

Elevated liver enzymes with RUQ pain suggest biliary obstruction or cholestasis, which changes your diagnostic pathway toward MRCP rather than HIDA scan. 8

Step 3: Second-Line Imaging Based on Clinical Context

If ultrasound is negative or equivocal with high clinical suspicion for acute cholecystitis:

• Order Tc-99m cholescintigraphy (HIDA scan), which has 97% sensitivity and 90% specificity for acute cholecystitis, superior to ultrasound 3, 8
• HIDA scan is the imaging examination of choice for suspected acalculous cholecystitis 8

If liver function tests are elevated suggesting biliary obstruction:

• Order MRCP (not HIDA scan), which has 85-100% sensitivity and 90% specificity for choledocholithiasis 8
• MRCP visualizes the common bile duct and cystic duct better than ultrasound and identifies the level and cause of biliary obstruction with 91-100% accuracy 8

If patient is critically ill, has peritoneal signs, or complications are suspected:

• Order CT abdomen/pelvis with IV contrast, which has >95% sensitivity for detecting colonic pathology and can identify alternative diagnoses 6
• CT with contrast is highly sensitive (74-96%) and specific (90-94%) for detecting biliary obstruction and determining its cause 3

Step 4: Advanced Imaging for Specific Scenarios

For suspected complications of cholecystitis (emphysematous cholecystitis, gangrenous cholecystitis, perforation, gallbladder empyema):

• CT with IV contrast is valuable for confirming the extent and nature of complications 3, 2

For pain specifically triggered by bowel movements:

• This suggests colonic or mechanical causes (hepatic flexure pathology, splenic flexure syndrome) rather than primary hepatobiliary disease 6
• If ultrasound is negative, proceed to CT abdomen/pelvis with IV contrast to evaluate colonic pathology 6

Critical Pitfalls to Avoid

• Do not skip ultrasound and proceed directly to CT unless the patient is hemodynamically unstable, as ultrasound is more appropriate for initial evaluation and avoids unnecessary radiation exposure 6
• Do not order HIDA scan as the primary test for elevated LFTs and RUQ pain unless acute cholecystitis is the primary clinical concern; elevated LFTs require anatomic visualization of bile ducts via MRCP 8
• Do not rely solely on sonographic Murphy sign, which has relatively low specificity for acute cholecystitis 1
• If CT is indicated, always use IV contrast unless there are specific contraindications, as noncontrast CT will miss critical diagnostic features like wall enhancement and liver hyperemia 3
• Single-phase post-contrast CT is sufficient for evaluating gallstones; adding a noncontrast phase provides little additional information 3