From the Guidelines
To diagnose a previous kidney stone in a patient who presents after resolution of symptoms, but had suspicious symptoms suggestive of nephrolithiasis, noncontrast CT (NCCT) is the imaging study of choice, as it can reliably characterize the location and size of an offending ureteral calculus and diagnose alternative etiologies of abdominal pain 1. When evaluating a patient with a history of symptoms suggestive of nephrolithiasis, it is essential to consider the high recurrence rate of kidney stone disease, which can be up to 50% within 5 years. The diagnostic approach should prioritize tests that can detect residual stones, obstruction, or other complications. Key considerations in the diagnostic approach include:
- Noncontrast CT (NCCT) as the initial imaging study, due to its high sensitivity and ability to characterize stones and alternative etiologies of abdominal pain 1.
- Ultrasound as an alternative, especially in patients who should avoid radiation, although it is less sensitive than NCCT.
- Urinalysis to check for microscopic hematuria, which may persist after stone passage.
- Serum electrolytes, calcium, uric acid, and 24-hour urine collection to identify risk factors for recurrence and guide prevention strategies. The choice of diagnostic test should be guided by the patient's presentation, medical history, and risk factors for kidney stone disease. In patients with known kidney stone disease and recurrent symptoms, NCCT remains the test of choice for evaluation 1. By prioritizing NCCT and other diagnostic tests, clinicians can accurately diagnose and manage kidney stone disease, reducing the risk of recurrence and improving patient outcomes.
From the Research
Diagnosing Previous Kidney Stone (Nephrolithiasis)
To diagnose a previous kidney stone in a patient who presents after resolution of symptoms, several methods can be employed:
- 24-Hour Urinary Chemistries: Analyzing 24-hour urine collections can help identify urinary factors associated with kidney stone formation, such as urine volume, pH, and concentrations of calcium, citrate, oxalate, potassium, magnesium, uric acid, phosphorus, and sodium 2.
- Imaging Studies: Ultrasonography (US) can be used to detect renal calculi, but its sensitivity and specificity may be limited, especially for small stones 3. Non-contrast computed tomography (CT) can provide more accurate information on stone size and location.
- CT Attenuation Value: Measuring the CT attenuation value of renal papilla can predict the severity and recurrence of kidney stone disease, with higher values indicating a higher risk of recurrence 4.
- Complete Blood Count (CBC) Parameters: Certain CBC parameters, such as red blood cell distribution width (RDW), mean platelet volume (MPV), platelet distribution width (PDW), white blood cell count, granulocyte percentage, and lymphocyte percentage, may be associated with urinary stone disease 5.
- Medical History and Physical Examination: A thorough medical history and physical examination can help identify underlying genetic or systemic diseases that may contribute to kidney stone formation, as well as assess the patient's overall health and risk factors for recurrence 6.
Laboratory Tests and Imaging Studies
The following laboratory tests and imaging studies can be used to diagnose and evaluate kidney stone disease:
- Urinalysis: To detect microscopic hematuria, which is associated with urinary stone disease 5.
- 24-Hour Urine Collection: To analyze urinary chemistries and identify factors associated with kidney stone formation 2.
- Ultrasonography (US): To detect renal calculi, but with limited sensitivity and specificity 3.
- Non-Contrast Computed Tomography (CT): To provide accurate information on stone size and location, and to measure CT attenuation value of renal papilla 4.
- Complete Blood Count (CBC): To evaluate CBC parameters associated with urinary stone disease 5.