What are the differential diagnoses for a patient with intermittent sharp right flank pain, radiating up under the right abdomen and ribs, with a pain score of 8/10, lasting for 4 days?

Differential Diagnoses for Right Flank Pain Radiating to Right Upper Quadrant

The most likely diagnoses for intermittent sharp right flank pain radiating up under the right ribs include urolithiasis (kidney stones), acute cholecystitis, and musculoskeletal causes, with urolithiasis being the leading consideration given the classic colicky nature and radiation pattern. 1

Primary Differential Diagnoses

Urolithiasis (Kidney Stones)

• Classic renal colic presents as colicky, wave-like severe pain that is independent of body position, radiating into the groin or genitals with abrupt onset. 1, 2
• The intermittent nature and 8/10 severity strongly suggest stone disease, particularly when pain radiates upward toward the ribs. 1
• Stones <5 mm typically pass spontaneously, while larger stones or those causing complete obstruction may require endoscopic intervention. 1, 3
• Important caveat: Over 20% of patients with confirmed urinary stones may have negative urinalysis, so absence of hematuria does not exclude stone disease. 1, 2

Acute Cholecystitis

• Right upper quadrant pain with radiation to the right flank is a primary presentation of acute cholecystitis. 4
• Associated symptoms typically include Murphy's sign, fever, nausea, and abdominal tenderness. 4
• Pericholecystic fluid, distended gallbladder, and edematous gallbladder wall are characteristic imaging findings. 4

Musculoskeletal Causes

• Pain occurring after prolonged static positioning is more likely to have a musculoskeletal origin, particularly involving the paraspinal muscles, facet joints, or referred pain from lumbar spine pathology. 1
• Slipping rib syndrome (8th-10th ribs) causes intermittent, debilitating lower rib and abdominal pain from hypermobility of anterior false ribs. 5, 6
• Pain that varies with respiration, body position, or is accompanied by local tenderness suggests musculoskeletal origin. 4

Gastrointestinal Causes

• Right colonic diverticulitis, gastroenteritis and colitis, and inflammatory bowel disease can present as right-sided flank pain. 1
• Acute pancreatitis may present with right-sided pain radiating to the back. 4

Gynecologic Causes (if applicable)

• Benign adnexal masses and pelvic congestion syndrome can cause flank pain in women. 1
• Ectopic pregnancy should be considered in women with delayed menses presenting with flank pain. 1

Recommended Diagnostic Approach

Initial Imaging

• Non-contrast CT of the abdomen and pelvis is the imaging study of choice for evaluating flank pain, with 98-100% sensitivity and specificity for detecting urinary stones and identifying alternative diagnoses in approximately one-third of patients. 1, 3
• CT is recommended for evaluating right lower quadrant or right upper quadrant pain when the diagnosis is unclear. 4
• Ultrasonography is the initial imaging test of choice specifically for right upper quadrant pain when cholecystitis is the primary concern. 4

Clinical Assessment Priorities

• Record vital signs to exclude shock or hemodynamic instability requiring urgent evaluation. 1
• Assess for fever >38°C, chills, or signs of systemic infection indicating possible pyelonephritis or perinephric abscess requiring immediate hospitalization. 2
• Perform urinalysis with assessment of white blood cells, red blood cells, and nitrites. 2
• Beta human chorionic gonadotropin testing should be considered before performing diagnostic imaging in all women of reproductive age presenting with acute abdominal pain. 4

Critical Red Flags Requiring Urgent Evaluation

• Fever, chills, or visible blood in urine require immediate evaluation for possible infection or obstruction. 1
• Inability to urinate or decreased urine output requires urgent evaluation. 1
• Sudden onset of ripping chest pain with radiation to the back is suspicious of acute aortic syndrome. 4
• Hemodynamic instability or signs of sepsis mandate immediate hospital admission regardless of imaging results. 1, 2

Common Pitfalls to Avoid

• Do not assume all flank pain is kidney-related; the positional nature of symptoms is a key distinguishing feature for musculoskeletal causes. 1
• Do not assume the absence of hematuria excludes stone disease, as the clinical picture may have evolved. 1, 2
• Do not delay imaging in young females—consider gynecologic causes that may require urgent intervention. 1
• A normal urinalysis does not exclude significant urologic pathology. 1
• Revisit the diagnosis if the patient fails to improve clinically, considering other obscure and urgent pathologies including skeletal tuberculosis in endemic populations. 7