The Asymptomatic Kidney Stone: To Treat or Not to Treat

Many patients show up to urology clinic with kidney stones that are not causing problems at the moment.  It is well known that obstructing kidney stones can cause excruciating pain and discomfort, so the question often follows, "Should I have this stone treated before it causes problems?"  The following is a discussion of the facts surrounding Asymptomatic Kidney Stones.

It is estimated that 5% of women and 10% of men in the US have nephrolithiasis (or kidney stones).[1,2]  Most people do not know they have kidney stones until they obstruct one of the ureters, connecting the kidney to the bladder.  These symptoms may include flank pain, nausea and vomiting, hematuria (blood in the urine) or high fever.  Many patients have kidney stones and have no symptoms.  In fact, studies of patients without symptoms of nephrolithiasis who underwent imaging for other reasons demonstrate asymptomatic nephrolithiasis in 7.8-9.7% of patients, often with these patients having more than one stone and stones of a size that are likely to eventually obstruct and cause symptoms.[3,4]

Brian Matlaga, MD, MPH, Director of Stone Disease and Ambulatory

Brian Matlaga, MD, MPH

Urology at the Brady Urological Institute at Johns Hopkins recently told Practice Updates: Urology, "In general, our indications for surgery for stone patients are pain, obstruction, or infection. In most cases, patients with incidentally found stones will not meet any of these three criteria—which usually, then, results in the conservative, expectant approach."  A recent analysis by Goldsmith and Lipkin in Nature Reviews Urology reports that 50% of patients with asymptomatic stones will develop symptoms at five years.  Of these patients, half will pass spontaneously and half will require surgery.[5]  Dr. Matlaga summarizes, "I quote patients a 10% risk per year of their stone becoming symptomatic, and counsel them as to how a stone event might present and what they should do at that time." 

There are a number of characteristics that may influence the need to treat an asymptomatic stone including stone size, location and patient characteristics.  Stones >4mm have a 26% greater chance of being symptomatic than stones <4mm, and 15mm stones have a 100% chance of causing an issue.  Stones in the renal pelvis are more likely to migrate into the ureter and cause symptoms than stones in the lower pole calyx.[6]  Patient characteristics that may push a urologist to treat a stone include those patients in whom an obstructing kidney stone could have serious consequences.  These include patients with solitary kidney or baseline kidney disease, other medical comorbidities that could make a kidney infection or unplanned surgery more risky (including immunosuppresion or diabetes), patients who have surgically reconstructed urinary systems or some patients in unique professions with serious consequences of an obstructing stone (like airline pilots).  

In general, it is recommended to follow patients expectantly until an asymptomatic stones becomes symptomatic.  Patients with large stones (especially in the renal pelvis), a solitary kidney or those with a serious risk of adverse consequences due to an obstructing stone should consider earlier elective treatment of the stone.

1. Johnson, C. M., Wilson, D. M., O'Fallon, W. M., Malek, R. S. & Kurland, L. T. Renal stone epidemiology: a 25-year study in Rochester, Minnesota. Kidney Int. 16, 624–631 (1979).

2. Hiatt, R. A., Dales, L. G., Friedman, G. D. & Hunkeler, E. M. Frequency of urolithiasis in a prepaid medical care program. Am. J. Epidemiol. 115, 255–265 (1982).

3. Boyce, C. J., Pickhardt, P. J., Lawrence, E. M., Kim, D. H. & Bruce, R. J. Prevalence of urolithiasis in asymptomatic adults: objective determination using low dose noncontrast computerized tomography. J. Urol. 183, 1017–1021 (2010).

4. Lorenz, E. C. et al. Clinical characteristics of potential kidney donors with asymptomatic kidney stones. Nephrol. Dial. Transplant. 26, 2695–2700 (2011).

5. Goldsmith ZG, Lipkin ME.  When (and how) to surgically treat asymptomatic renal stones. Nat Rev Urol. 2012 Mar 27;9(6):315-20. doi: 10.1038/nrurol.2012.43.

6. Burgher, A., Beman, M., Holtzman, J. L. & Monga, M. Progression of nephrolithiasis: long-term outcomes with observation of asymptomatic calculi. J. Endourol. 18, 534–539 (2004).