Editorial Comment for Chu et al .

Although the true risk of medical-related radiation exposure is not understood, it has been estimated that 29,000 future cancer cases in the United States can be attributed to CT scans performed in 2007. ¹ Patients with urolithiasis are at risk of increased radiation exposure compared with the general population secondary to diagnostic and treatment measures. One study found that a patient with incidence of stone formation could undergo as many as six (mean 1.7) CT scans in a year after diagnosis. ² In response to such concerns, physicians have been driven to develop new measures to diagnose and treat urolithiasis.

Historically, the kidney, ureter, and bladder radiograph (KUB) with tomograms and intravenous urogram (IVG) was widely available and utilized. This imaging modality was low cost and highly reproducible, but was limited by the inability to identify radiolucent stones, need for bowel preparation, and with relatively high-effective radiation doses (3.93 mSv). ³ Techniques such as ultrasonography and MRI have been trialed as a diagnostic measure to eliminate radiation exposure, but both have serious limitations hindering their general application. Ultrasonography is operator dependent, can be difficult in obese or acutely obstructed patients, and has a low overall accuracy of 63% for ureteral and 66% for renal calculi. ⁴ Although MRI can provide excellent soft tissue details of the urinary tract, calcium is not observed and, therefore, stone disease can be difficult to diagnose. Furthermore, MRI is expensive, time intensive, not widely available in the acute setting, and cannot be performed in patients with claustrophobia, pacemakers, or implanted metal devices. With an absence of reliable radiation-free options, CT scans have since replaced KUB with tomograms and IVG as the preferred method of stone diagnosis. With current era scanning techniques, stone disease can be diagnosed with nearly 100% sensitivity and specificity. ⁵ In an effort to decrease radiation exposure, low-dose CT scans (∼3 millisieverts [mSv]) and ultralow-dose CT scans (0.83 mSv) have been introduced. ^6,7 Furthermore, to limit unnecessary radiation exposure to the stone patient, the American Urological Association has published imaging guidelines for the practicing urologist. ⁸

As a collaborative effort, the urologic community has done well in limiting radiation exposure through advancements in diagnostic imaging techniques for stone disease, and we are making progress in the treatment realm as well. Almost all treatment modalities for urolithiasis (shockwave lithotripsy [SWL], ureteroscopy, and percutaneous nephrolithotomy) require the use of radiation. Although ultrasonography can be utilized to localize stones during SWL, the same limitations associated with ultrasonography for stone diagnosis also apply for treatment, thus fluoroscopy is frequently utilized. A study assessing radiation exposure to patients with urolithiasis at time of SWL found that the mean radiation exposure for SWL treatment was 7 mSv for renal and ureteral stones and radiation exposure increased in larger patients. ⁹ Although fluoroscopy-free ureteroscopy has been proposed, fluoroscopy is often utilized as it is the safest measure to guide safety wire and access sheath placement. The estimated radiation exposure to a patient during a standard ureteroscopic procedure is slightly less than SWL at 6 mSv. ⁹ Finally, percutaneous nephrolithotomy poses one of the greatest concerns. It was common in early surgical series for fluoroscopy times to reach as high as 25 minutes for a single percutaneous nephrolithotomy procedure. However, with improved techniques, radiation exposure has drastically decreased. A current era percutaneous nephrolithotomy series demonstrated a mean fluoroscopy time of 386 seconds to 545 seconds and an effective radiation dose of 7.6 mSv to 8.1 mSv. ¹⁰ Although this one-time radiation dose may seem relatively low compared with the 50 mSv per year dose allowed for health workers by the radiation physics society, we should continue to strive to limit the radiation exposure to not only the patient but also to the surgeon and operating room personnel.

In this issue of the Journal of Endourology, Chu and colleagues present three ultrasound-guided techniques for percutaneous renal access and stone manipulation for use at time of percutaneous nephrolithotomy. ¹¹ The article demonstrates techniques to effectively access the kidney without the aid of fluoroscopy and even move small caliceal stones to a more desirable location within the kidney using an ultrasound needle. Ultrasound-guided percutaneous renal access has many advantages beyond that of no radiation exposure such as solid organ visualization to avoid inadvertent injury, eliminate the need for retrograde ureteral access, and provide an imaging source that can be run solely by the surgeon, limiting the number of operating room personnel. However, percutaneous renal access using ultrasound guidance has a learning curve that should be respected. Hands-on experience is required to master the technique, and currently few surgeons are trained to perform the procedure, resulting in limited availability. Furthermore, although access can be obtained to the kidney with ultrasound guidance, the tract is often dilated and the nephrostomy tube is placed with the use of fluoroscopy. Despite these limitations and as surgeons continue to push for radiation-free imaging options, I anticipate that ultrasonography will become more widely available for treatment measures. One day in the near future, we may even be able to completely treat almost all renal and ureteral stones without the use of any ionizing radiation.