What is the cause of left flank pain radiating to the scapula for 4 days with a negative urinalysis?

Differential Diagnosis for Left Flank Pain Radiating to Scapula with Negative Urinalysis

In a 35-year-old male with left flank pain radiating to the scapula for 4 days and negative urinalysis, you should obtain non-contrast CT abdomen/pelvis as the diagnostic study of choice, as this presentation suggests possible urolithiasis (despite negative urinalysis), musculoskeletal pathology, or alternative intra-abdominal causes that require imaging for definitive diagnosis. 1

Key Diagnostic Considerations

Urolithiasis Remains Possible Despite Negative Urinalysis

• Hematuria is absent in 5.5-14.5% of patients with confirmed acute urinary lithiasis, making a negative urinalysis insufficient to exclude kidney stones 2, 3
• The combination of urinalysis plus urine dipstick testing reduces the false-negative rate to 5.5%, but this still means approximately 1 in 20 patients with stones will have completely negative urine studies 2
• Classic renal colic presents as colicky, wave-like severe pain that is independent of body position, which helps distinguish it from musculoskeletal causes 1

Radiation Pattern Suggests Alternative Diagnoses

• Pain radiating to the scapula is atypical for uncomplicated urolithiasis, which classically radiates to the groin or genitals 4
• The American College of Radiology notes that pain occurring after prolonged static positioning or that worsens with external pressure suggests musculoskeletal origin involving paraspinal muscles, facet joints, or referred pain from lumbar spine pathology 1
• Scapular radiation raises concern for referred pain from diaphragmatic irritation, splenic pathology, or pancreatic tail processes on the left side

Recommended Diagnostic Approach

First-Line Imaging

Non-contrast CT abdomen/pelvis is the gold standard imaging modality with the following advantages 4, 1, 5:

• 98-100% sensitivity and specificity for detecting urinary stones 4, 1
• Identifies alternative extraurinary diagnoses in approximately one-third of patients presenting with flank pain 1, 5
• Detects stones regardless of size, location, or chemical composition 5
• Time-efficient, performed within 5 minutes 5
• Does not require contrast administration 5

Alternative Imaging Considerations

• Ultrasound with color Doppler can be used if radiation concerns exist, though it has lower sensitivity (45%) compared to CT 4
• Ultrasound is 96% sensitive for detecting hydronephrosis and can assess ureteral jets, but absence of hydronephrosis makes larger ureteral stones (>5 mm) less likely 4, 1
• KUB radiography has poor sensitivity (29% overall, 72% for large proximal stones) and should not be relied upon as a primary diagnostic tool 1

Critical Red Flags Requiring Urgent Evaluation

Immediately assess for the following high-risk features 1:

• Fever, chills, or signs of systemic infection (suggests pyelonephritis or perinephric abscess)
• Inability to urinate or decreased urine output (suggests complete obstruction)
• Hemodynamic instability (consider ruptured abdominal aortic aneurysm in patients >60 years, though less likely at age 35) 4

Alternative Diagnoses to Consider

Musculoskeletal Causes

• Positional variation in pain intensity strongly suggests musculoskeletal etiology rather than visceral pathology 1
• Paraspinal muscle strain, facet joint arthropathy, or radiculopathy from lumbar spine pathology can refer pain to the flank and scapular region 1

Gastrointestinal Causes

• Left colonic diverticulitis, inflammatory bowel disease, or gastroenteritis can present with left flank pain 1
• Pancreatic tail pathology (pancreatitis, mass) may refer pain to the left scapula via diaphragmatic irritation

Vascular and Renal Parenchymal Causes

• Page kidney (subcapsular hematoma causing renal compression) can present with flank pain and hematuria, though hematuria may be absent 6
• Renal vein thrombosis, though rare, can present with flank pain and may have associated proteinuria on urinalysis 7

Common Pitfalls to Avoid

• Do not assume negative urinalysis excludes urolithiasis—up to 14.5% of stone patients lack hematuria 2
• Do not attribute all flank pain to renal pathology—the radiation pattern to the scapula and positional nature of symptoms are critical distinguishing features 1
• Do not delay imaging in favor of empiric treatment—one-third of patients with flank pain have extraurinary causes requiring different management 1, 5
• Do not rely on plain radiography (KUB) as a primary diagnostic tool given its poor sensitivity 1

Management Based on Imaging Results

• If stones <5 mm are identified, spontaneous passage is likely and conservative management with NSAIDs (diclofenac, ibuprofen) is appropriate 4, 1
• Stones >5 mm or causing complete obstruction may require endoscopic intervention 1
• If CT reveals no urinary pathology, only 14% require hospitalization and 4% undergo surgical intervention, compared to 41% hospitalization when non-appendiceal CT diagnosis is made 1