From the Guidelines
A 0.5cm kidney stone should be re-scanned, typically within 1-3 months after initial diagnosis or treatment, to monitor its progression and determine the need for intervention. This recommendation is based on the high sensitivity and specificity of noncontrast CT scans for detecting urolithiasis, as reported in a recent study published in the Journal of the American College of Radiology 1. The study highlights the importance of accurate stone size assessment, which can be achieved through noncontrast CT scans, and notes that stone location and size are associated with spontaneous stone passage rates.
For stones of this size, many will pass spontaneously with conservative management, including:
- Increased fluid intake (2-3 liters of water daily)
- Pain control with medications like ibuprofen (600-800mg every 6-8 hours as needed) or acetaminophen (650-1000mg every 6 hours as needed)
- Possibly alpha-blockers such as tamsulosin (0.4mg daily) to relax the ureter and facilitate stone passage. The re-scan helps determine if additional interventions are necessary, such as ureteroscopy, shock wave lithotripsy, or percutaneous nephrolithotomy if the stone hasn't passed or has grown. Although ultrasound is often preferred for follow-up imaging due to its lack of radiation, CT scans provide more detailed information about stone composition and exact location, as noted in the study 1. Re-scanning is crucial because untreated kidney stones can lead to urinary obstruction, infection, or kidney damage if left unmonitored.
Key considerations for re-scanning include:
- The sensitivity of stone detection decreases with smaller stone size, and low-dose CT may be used to reduce radiation exposure while maintaining diagnostic accuracy 1
- Stone location and size can be accurately depicted at noncontrast CT and are associated with spontaneous stone passage rates
- CT techniques, such as coronal reformations and bone window viewing, can improve the accuracy of stone measurements 1.
From the Research
Kidney Stone Re-Scan Considerations
- The decision to re-scan a 0.5cm kidney stone depends on various factors, including the stone's location, size, and the patient's overall health.
- According to a study published in 2011 2, medical expulsion therapy (MET) can be effective in improving spontaneous stone passage rates for renal stones.
- However, the study focused on stones of 0.5-1.5 cm in size, and it is unclear if the results can be applied to smaller stones like the 0.5cm stone in question.
Treatment Options
- Extracorporeal shock wave lithotripsy (ESWL) is a common treatment option for kidney stones, but its effectiveness varies depending on the stone's size and location.
- A study published in 1998 3 compared ESWL and percutaneous nephrolithotomy (PCN) for treating single stones of the lower pole of the kidney, and found that PCN achieved better results for medium-size stones, but with higher morbidity.
- Another study published in 2012 4 compared ESWL and ureteroscopy for treating ureteric calculi, and found that ureteroscopy achieved a greater stone-free state, but with a higher complication rate and longer hospital stay.
Re-Scan Recommendations
- There is limited evidence to suggest that a 0.5cm kidney stone requires immediate re-scanning.
- A study published in 2015 5 compared flexible ureteroscopy and ESWL for treating kidney stones, and found that the success rate was higher for flexible ureteroscopy, but the difference was not significant.
- However, the study had a small sample size, and more research is needed to determine the best course of treatment for small kidney stones.
- A study published in 2008 6 found that adjunctive tamsulosin therapy combined with ESWL was safe and effective in enhancing stone clearance for renal stones 10-24 millimeters in diameter, but the evidence for smaller stones is limited.