Approximately 10% of US adults have had kidney stones. Within a five-year period, 50% of them reoccur.

When urine becomes concentrated, crystals can form on the kidney lining developing into stones. If dislodged into the urinary tract, they may cause severe pain, blood in urine, unusual ammonia like odors, fever, chills, and vomiting, warranting prompt medical attention.

Types of Stones

Calcium oxalate/calcium phosphate (80% of stones), uric acid (9%), cystine (10%), and struvite (1%) comprise the four main types. Identifying stone type informs treatment and prevention decisions. Blood and urine tests can help with identification as they provide calcium, mineral, oxalate, and uric acid levels. They also provide kidney function markers and signs of infection. Further, CT scans and ultrasounds can locate stones and determine their size. However, definitive identification requires laboratory analysis after passing or removal.

Treatment

Treatment depends on stone size and type. Providers may prescribe medications for pain and increased urine flow to aid passage. For larger stones, procedures range from least to most invasive depending on stone size from smallest to largest: 1) extracorporeal shock wave therapy (ESWT) to break stones for passage, 2) ureteroscopy with laser lithotripsy to remove or fragment stones via a ureteroscope, 3) percutaneous nephrolithotomy (PCNL), in which a nephroscope removes stones through a small back incision, 4) laparoscopic nephrolithotomy, accessing the kidney and removing the stone through the abdomen, and 5) open surgery.

Prevention

Although medications can reduce the risk of stone formation or reformation, dietary intervention is the least invasive and perhaps most effective. Common to preventing all types of stones is staying hydrated with 10 to 12 cups of water daily through fluids, fruits, and vegetables.

Calcium Oxalate

Reducing urinary oxalate, a waste product, is critical in preventing calcium oxalate formation.

Dietary calcium can bind oxalate in the intestines, reducing oxalate’s absorption and ultimately urine concentration.

The gut microbiome, particularly, Oxalobacter formigenes, significantly breaks down oxalate, preventing its absorption. Limiting excessive intake of high-oxalate foods such as rhubarb, spinach, almonds, cashews, and chocolate can reduce urinary oxalate levels. But a low-oxalate diet can deplete this beneficial oxalate catabolizing microbe, inadvertently allowing more oxalate absorption. So, prior to recommending unwarranted and possibly counterproductive dietary oxalate restriction, a provider may order a urine oxalate concentration test for vulnerable individuals. Levels above 25 mg/day may justify dietary restriction.

Finally, dietary citrate, in citrus fruits, binds urinary calcium, forming calcium citrate instead of calcium oxalate.

Uric Acid

Avoiding excess animal proteins can reduce urinary purine levels, which are precursors to uric acid crystals. Increasing alkaline vegetables, such as Brussel sprouts, cucumber, and cauliflower can prevent them from forming.

Cystine and Struvite

A diet low in red meats and sodium can reduce cystine stone formation. And finally, preventing urinary tract infections (UTIs) can prevent the rarer, struvite stone formation. Heightened attention to genital hygiene can reduce UTI and consequently struvite stone risk.

Summary

While usually not life threatening, kidney stones are painful and warrant medical attention. Medical treatments include drugs to help manage pain and facilitate stone passage. Procedures also include minimally invasive shock waves and ureteroscope access through the urinary tract to break up or remove the stones. More invasive procedures include PCNL via a small back incision to access the kidneys. More invasive procedures include laparoscopic and even open surgery.

Staying hydrated, and depending on the type of stone, consuming citrus fruits, avoiding excess consumption of high-oxalate foods, animal protein, and sodium, and preventing UTIs reduce risk. A registered dietitian can help with dietary planning.

About the Author

Patrick Traynor, PHD, MPH, RD, CPT is a registered dietitian with an insurance-based practice, MNT Scientific, LLC in South Lake Tahoe, CA, Minden, NV, & Ashland, OR. In office or video appointments can be requested online at MNTScientific.com or by calling (530)429-7363. Inquiries can be directed to info@mntscientific.com.