What are the differential diagnoses for a patient presenting with acute right upper quadrant (RUQ) pain?

Differential Diagnoses for Acute Right Upper Quadrant Pain

Most Common Diagnoses

Acute cholecystitis is the most frequent diagnosable cause of acute RUQ pain, but represents only two-thirds of cases, meaning over one-third of patients have alternative diagnoses. 1, 2

Biliary and Gallbladder Pathology

• Acute cholecystitis: Gallbladder inflammation with gallstones, fever, leukocytosis, and positive Murphy's sign 1
• Biliary colic: Episodic severe pain from gallstones causing transient cystic duct obstruction, typically radiating to right shoulder or back 1
• Choledocholithiasis: Common bile duct stones causing obstruction with elevated liver enzymes and possible jaundice 1
• Acute cholangitis: Requires the triad of jaundice, fever/chills, and RUQ pain, plus laboratory evidence of biliary stasis and imaging showing biliary dilatation 1
• Acalculous cholecystitis: Gallbladder inflammation without stones, commonly seen in critically ill patients 1

Hepatic Causes

• Hepatic abscess: May present with fever, RUQ pain, and elevated inflammatory markers; ruptured abscess is life-threatening 1, 2
• Hepatitis: Viral, alcoholic, or drug-induced liver inflammation 2
• Hepatic tumor or mass: Primary or metastatic lesions; rupture requires urgent intervention 1, 2
• Portal vein thrombosis: Vascular obstruction causing hepatic congestion 2

Pancreatic Pathology

• Acute pancreatitis: Elevated amylase/lipase with epigastric pain that may radiate to RUQ 3, 2
• Pancreatic mass or pseudocyst: May cause biliary obstruction or direct mass effect 2

Renal and Adrenal Causes

• Nephrolithiasis: Right kidney stones causing referred RUQ pain 2
• Pyelonephritis: Right kidney infection with fever, flank pain, and pyuria 2
• Renal mass or abscess: May present with RUQ pain and systemic symptoms 2
• Adrenal hemorrhage or mass: Rare but can cause acute RUQ pain 2

Gastrointestinal Causes

• Peptic ulcer disease: Gastric or duodenal ulcers, particularly if perforated 2, 4
• Gastroenteritis: Inflammatory bowel conditions 5
• Colitis: Including inflammatory bowel disease 5
• Bowel obstruction: Small or large bowel obstruction causing referred pain 2
• Appendicitis: Retrocecal appendix may present with RUQ pain rather than typical RLQ pain 2

Gynecologic Causes (Women of Reproductive Age)

• Ectopic pregnancy: Life-threatening if ruptured; pregnancy test mandatory before imaging 1, 3
• Ovarian torsion: May cause referred RUQ pain 1
• Pelvic inflammatory disease: Can present with upper abdominal pain 5
• Ovarian cyst or mass: Including hemorrhagic or ruptured cysts 5

Vascular Emergencies

• Mesenteric ischemia: Life-threatening condition requiring urgent intervention 1
• Hepatic vein thrombosis (Budd-Chiari syndrome): Causes hepatic congestion and RUQ pain 2
• Abdominal aortic aneurysm: Particularly if expanding or ruptured 2

Thoracic Causes

• Pulmonary embolism: Critical diagnosis that can present with RUQ pain 1
• Right lower lobe pneumonia: Referred pain from diaphragmatic irritation 2, 4
• Pleural effusion or pleuritis: Right-sided thoracic pathology causing referred pain 2

Critical "Can't Miss" Diagnoses

These life-threatening conditions require immediate recognition and intervention:

• Ruptured ectopic pregnancy: Requires urgent surgical intervention 1
• Perforated gallbladder with peritonitis: Needs immediate surgical consultation 1
• Ruptured hepatic abscess or tumor: Requires emergent management 1
• Mesenteric ischemia: Time-sensitive vascular emergency 1
• Pulmonary embolism: May present atypically with RUQ pain 1

Diagnostic Approach

Initial Clinical Assessment

• Obtain pregnancy test in all women of reproductive age before any imaging 1, 3
• Document pain characteristics: onset, duration, quality, radiation to right shoulder/back suggests biliary origin 3
• Assess for Murphy's sign (highly suggestive of acute cholecystitis), fever, jaundice, and peritoneal signs 3, 4
• Order complete blood count, liver function tests (ALT, AST, alkaline phosphatase, bilirubin), and pancreatic enzymes 3

Imaging Algorithm

Ultrasound is the mandatory first-line imaging study for all patients with acute RUQ pain, rated 9/9 (usually appropriate) by the American College of Radiology. 5, 1, 3, 6, 7

• Ultrasound advantages: 96% accuracy for gallstones, no radiation, rapid, cost-effective, evaluates multiple organ systems, and identifies alternative diagnoses 5, 1, 3
• CT abdomen with IV contrast: Use when ultrasound is equivocal, complications suspected, or alternative diagnoses need evaluation; provides 95% sensitivity and 94% specificity for appendicitis and excellent detection of non-biliary pathology 5, 1, 3
• HIDA scan (cholescintigraphy): Consider when ultrasound equivocal but clinical suspicion for acute cholecystitis remains high; offers 96% sensitivity and 90% specificity 1, 6
• MRI with MRCP: Preferred in pregnant patients with equivocal ultrasound, or when detailed biliary tree evaluation needed; 85-100% sensitivity for choledocholithiasis 1, 3

Critical Pitfalls to Avoid

• Never skip ultrasound and proceed directly to CT unless the patient is hemodynamically unstable; ultrasound provides rapid diagnosis without radiation 1, 3
• Never order CT without IV contrast for suspected cholecystitis; critical findings like gallbladder wall enhancement and adjacent liver parenchymal hyperemia cannot be detected without contrast 1, 3
• CT has only 75% sensitivity for gallstones, so negative CT does not exclude cholelithiasis; ultrasound remains superior for stone detection 1, 3
• Ultrasound has only 88% sensitivity for acute cholecystitis; if clinical suspicion is high despite negative/equivocal ultrasound, proceed to HIDA scan or CT 1
• Do not assume gallbladder sludge alone equals cholecystitis; critically ill patients commonly have gallbladder abnormalities including sludge without true acute cholecystitis 1
• Acute cholecystitis requires ≥2 ultrasound findings (wall thickening, pericholecystic fluid, sonographic Murphy sign, distension, or stones/sludge) plus clinical features (fever, leukocytosis, persistent pain) to establish diagnosis 1