From the Guidelines
The diagnostic workup for nephrolithiasis should include a comprehensive evaluation with a detailed medical history, laboratory tests such as urinalysis and serum chemistries, and imaging studies with a non-contrast CT scan as the gold standard, as it has a high sensitivity of 97% and specificity of 96% for detecting stones 1. The initial assessment should include a detailed medical history focusing on previous stone episodes, family history, diet, and medication use, as well as a screening evaluation consisting of serum chemistries and urinalysis to identify underlying medical conditions associated with stone disease 1. Key points to consider in the diagnostic workup include:
- A detailed history to elicit medical conditions, dietary habits, or medications that predispose to stone disease
- Laboratory tests such as urinalysis to check for blood, pH, and signs of infection, and serum chemistries to evaluate kidney function and electrolyte levels
- Imaging studies with a non-contrast CT scan as the gold standard for detecting stones
- Stone analysis when stones are passed or retrieved surgically to determine composition and guide prevention strategies
- Additional specialized tests such as parathyroid hormone levels if hypercalcemia is detected The use of low-dose non-contrast CT for stone assessment has been shown to have a pooled sensitivity of 97% and a pooled specificity of 95% 1, making it a suitable alternative to standard-dose CT. In certain cases, such as pregnant patients or children, ultrasound may be used to avoid radiation exposure. Overall, a comprehensive workup allows for targeted treatment and prevention strategies based on the specific underlying causes of stone formation, which is essential for reducing morbidity, mortality, and improving quality of life.
From the Research
Diagnostic Workup for Nephrolithiasis
The diagnostic workup for nephrolithiasis (kidney stones) involves a combination of medical history, physical examination, laboratory tests, and imaging studies.
- A thorough medical history is essential, including the number, composition, location, and outcome of previous stone events, as well as family history of stones, dietary habits, and medications 2.
- Laboratory tests include:
- Urinalysis to check for blood, protein, and other abnormalities in the urine 3, 2.
- Serum chemistry studies to evaluate electrolyte levels, kidney function, and other parameters 3, 2.
- Analysis of 24-hour urine collections to assess urine pH, volume, and levels of various substances such as calcium, oxalate, and citrate 3, 2.
- Imaging studies include:
- Plane X-ray films to document radiopaque stones 2.
- Ultrasonography to image nonopaque calculi and distinguish them from other masses such as tumors or blood clots 2.
- Computed tomography (CT) scans, which are excellent for imaging nonopaque renal calculi but have higher costs and radiation exposure 2, 4.
- Crystallographic analysis is an essential diagnostic procedure to determine the composition of the stone 2.
- The complexity of the diagnostic protocol depends on the severity of nephrolithiasis, with patients having a single stone episode undergoing a simple protocol and those with recurrent stone disease or increased risk undergoing an extensive detailed protocol 2.
Extensive Metabolic Evaluation
For patients with recurrent stone disease or increased risk, an extensive metabolic evaluation is necessary, which includes:
- Determination of serum levels of alkaline phosphatase, parathyroid hormone, thyroxin, and magnesium 2.
- A 24-hour collection of urine specimen analyzed for various substances such as urea, creatinine, uric acid, calcium, phosphate, sodium, magnesium, oxalate, and citrate 2.
- Specialized evaluation tests, such as urinary acidification tests, to detect distal renal tubular acidosis 2.
- Fasting and calcium load tests to evaluate renal calcium leak and intestinal calcium absorption 2.