From the Guidelines
The workup for kidney stones should begin with a thorough medical history and physical examination, followed by laboratory tests including urinalysis, complete blood count, and comprehensive metabolic panel, as well as imaging studies such as a non-contrast CT scan, which is the gold standard for detecting stones. This approach is supported by the American College of Physicians guideline on dietary and pharmacologic management to prevent recurrent nephrolithiasis in adults 1.
The initial evaluation should also include stone analysis when stones are passed or retrieved to determine composition, which guides prevention strategies. A 24-hour urine collection is often performed to identify metabolic abnormalities contributing to stone formation, measuring factors like calcium, oxalate, citrate, and urine volume 1.
Key points to consider in the workup include:
- Medical history to identify risk factors and previous stone episodes
- Physical examination to assess for signs of infection, obstruction, or other complications
- Laboratory tests to evaluate kidney function, electrolyte levels, and urinary parameters
- Imaging studies to detect stones and assess their size, location, and composition
- Stone analysis to guide prevention strategies
- 24-hour urine collection to identify metabolic abnormalities contributing to stone formation
Additional specialized tests may be ordered based on initial findings, such as parathyroid hormone levels if hypercalciuria is detected. This comprehensive approach helps identify the stone type, underlying causes, and guides both immediate treatment and long-term prevention strategies to reduce recurrence risk, which can be as high as 50% within 5-10 years without appropriate intervention 1.
From the Research
Workup for Kidney Stones
The workup for kidney stones typically involves imaging studies to detect and characterize the stones.
- CT scans are considered the gold standard for evaluating urinary stones, providing information on stone composition, size, burden, location, and collecting system anatomy 2.
- Non-contrast CT scans can detect up to 95% of renal, ureteric, and bladder stones, especially those with calcium composition 3.
- Low-dose and ultra-low-dose CT protocols exist to reduce radiation exposure, and studies have shown that these protocols can still effectively detect stone fragments, although small uric acid fragments may require higher energy settings 4.
- Ultrasound and conventional radiography are also recommended for follow-up of renal stones, as they do not expose patients to ionizing radiation 2.
Imaging Modalities
Different imaging modalities have their own strengths and limitations:
- CT scans are highly sensitive for detecting kidney stones and provide valuable information on stone size, composition, and location, but can be deceiving due to motion artifacts or other factors 5.
- Ultrasound is a non-invasive and non-ionizing modality that can be used for follow-up of renal stones, but may not detect all types of stones.
- Conventional radiography can be used to detect radiopaque stones, but may not detect radiolucent stones.
Clinical Considerations
When evaluating kidney stones, it is essential to consider the clinical context and correlate imaging findings with patient symptoms and medical history:
- Stone composition and size can influence treatment decisions, and imaging studies can provide valuable information on these factors 4.
- Patient factors, such as obesity, can affect imaging results and treatment outcomes 5.
- Follow-up imaging studies are crucial to monitor stone progression and treatment response, and to adjust treatment plans as needed 2.