Imaging and Diagnostic Approach for Acute Right Upper and Lower Quadrant Abdominal Pain

Initial Imaging Strategy

• Ultrasound is the first‑line test for right‑upper‑quadrant (RUQ) pain, providing approximately 96 % accuracy for detecting gallstones and allowing diagnosis of acute cholecystitis. (American College of Radiology) 2
• A positive sonographic Murphy sign together with gallstones and gallbladder wall thickening (>3 mm) helps differentiate acute from chronic cholecystitis, although specificity is reduced after analgesic administration. (American College of Radiology) 2
• Contrast‑enhanced CT of the abdomen is the preferred modality for right‑lower‑quadrant (RLQ) pain, offering high diagnostic accuracy for appendicitis and simultaneously identifying diverticulitis, ureteral stones, colitis, and bowel obstruction. (American College of Radiology) 3
• When RUQ and RLQ pain coexist, contrast‑enhanced CT is required to rule out life‑threatening conditions such as perforated viscus, mesenteric ischemia, and complicated biliary disease with peritonitis. (American College of Radiology) 4

Imaging Decision Pathway

• If ultrasound demonstrates acute cholecystitis (gallstones, wall thickening > 3 mm, pericholecystic fluid, and a positive Murphy sign), the patient should be referred promptly for surgical consultation. (American College of Radiology) 2
• When ultrasound is negative or equivocal but clinical suspicion for biliary obstruction remains high, MRI with MRCP should be performed; it shows 85–100 % sensitivity for stones located in the gallbladder neck, cystic duct, or common bile duct that may be missed on ultrasound. (American College of Radiology) 4
• Contrast‑enhanced CT is essential not only for evaluating appendicitis but also for detecting complications of biliary disease such as gallbladder perforation, gangrene, intramural gas, and adjacent hepatic hyperemia—findings that are not visible on non‑contrast studies. (American College of Radiology) 3
• IV contrast is critical because gallbladder wall enhancement patterns and early hepatic hyperemia are early markers of acute cholecystitis and cannot be assessed without contrast. (American College of Radiology) 4

Biliary Pathology

• Acute cholecystitis is the most common cause of RUQ pain and can become life‑threatening if it progresses to perforation or gangrene. (American College of Radiology) 2
• Chronic cholecystitis is often imaging‑negative; hepatobiliary scintigraphy (cholescintigraphy) may be required when symptoms are intermittent and ultrasound is nondiagnostic. (American College of Radiology) 4
• CT detects gallstones with only about 75 % sensitivity because stone visibility depends on density relative to bile; a negative CT does not exclude cholelithiasis. (American College of Radiology) 4

Appendicitis and Right‑Lower‑Quadrant Pathology

• Appendicitis is the leading surgical cause of RLQ pain; reliance on clinical assessment alone yields a negative appendectomy rate of up to 25 %, underscoring the need for imaging. (American College of Radiology) 3
• Alternative diagnoses for RLQ pain that should be considered on CT include right‑sided diverticulitis, ureteral calculi, colitis, small‑bowel obstruction, and, in women, gynecologic pathology. (American College of Radiology) 3

Diagnostic Pitfalls and Safety Recommendations

• Clinical examination and laboratory tests alone lack sufficient accuracy to confirm or exclude acute cholecystitis or appendicitis; imaging is mandatory. (American College of Radiology) 2
• IV contrast must not be omitted on CT unless contraindicated, because non‑contrast scans miss critical findings such as gallbladder wall enhancement, hepatic hyperemia, and vascular complications. (American College of Radiology) 4
• A negative ultrasound does not rule out biliary stones in the gallbladder neck, cystic duct, or common bile duct; MRI/MRCP should be employed in these scenarios. (American College of Radiology) 4
• When both quadrants are involved, imaging should not be delayed; prompt CT can identify surgical emergencies that require immediate intervention. (American College of Radiology) 3

Laboratory Indicators (Supporting, Not Definitive)

• Elevated white‑blood‑cell count and fever are suggestive of acute cholecystitis or appendicitis, but their absence does not exclude these conditions. (American College of Radiology) 2

All facts are derived from peer‑reviewed guidelines and studies published by the American College of Radiology; strength of evidence is described as high where diagnostic accuracy percentages are provided.