What is the primary sign on physical exam for a patient with a kidney stone?

Costovertebral Angle Tenderness is the Primary Physical Exam Sign for Kidney Stones

The primary sign on physical examination for a patient with a kidney stone is costovertebral angle tenderness (CVAT), which should be specifically assessed in all patients with suspected kidney stone disease.1

Key Physical Examination Findings

• Costovertebral angle tenderness (CVAT): This is elicited by percussing the costovertebral angle (where the last rib meets the vertebral column) and is the most reliable physical exam finding in patients with kidney stones
• Abdominal examination: May reveal tenderness along the course of the ureter, particularly in the flank area or lower quadrants
• Vital signs: Patients may present with tachycardia due to pain; fever suggests possible infection complicating the stone

Diagnostic Algorithm

1. Initial assessment: Evaluate for CVAT in any patient with flank pain or symptoms suggestive of kidney stones

2. Secondary signs: Look for associated findings:

   • Restlessness or inability to find a comfortable position
   • Nausea and vomiting
   • Microscopic or gross hematuria (though not always present)
   • Radiation of pain to groin or genitalia

3. Red flags requiring immediate attention:

   • Fever (suggests infection with obstruction)
   • Single kidney with obstruction
   • Bilateral obstruction
   • Severe pain unresponsive to analgesics

Imaging Confirmation

After identifying CVAT on physical exam, appropriate imaging should be obtained:

• Ultrasound: First-line imaging modality with 45% sensitivity but 94% specificity for ureteral stones and 88% specificity for renal stones 1
• Non-contrast CT: Gold standard with sensitivity up to 97% when CVAT is present but clinical suspicion remains high 1

Important Clinical Considerations

• CVAT may be absent in early presentations (within first 2 hours) before secondary signs of obstruction develop 1
• The absence of hydronephrosis on ultrasound makes the presence of a larger ureteral stone (>5 mm) less likely 1
• Physical exam findings should be correlated with urinalysis, which typically shows hematuria, though this may be absent in up to 10-15% of confirmed cases 2

Common Pitfalls

• Misdiagnosis: CVAT can be confused with musculoskeletal pain; ensure proper technique when percussing the costovertebral angle
• Overlooking infection: Always check for fever and signs of urinary tract infection, as infected obstructing stones represent a urologic emergency
• Atypical presentations: Some patients may present with isolated abdominal or inguinal pain without classic CVAT 3
• Incomplete evaluation: Even when CVAT is present, a thorough evaluation including imaging and laboratory studies is necessary to confirm the diagnosis and assess for complications

Remember that while CVAT is the primary physical exam finding, the diagnostic accuracy increases when combined with appropriate history, laboratory studies, and imaging.