Can Potassium Citrate Help Small Kidney Stones?

The study “ Therapeutic Efficacy of Potassium Citrate for Treating Less Than 10-Millimeter Renal Stones” by Fateme Guitynavard et al. (2021) explores a non-surgical way to manage small kidney stones. It focuses on potassium citrate tablets as a treatment option for renal stones under 10 millimeters.

In this scientific paper, the authors tracked how stone size and “stone-free” rates changed over time in patients who took potassium citrate, while also monitoring safety and side effects. This summary paraphrases and explains the study so readers can understand the design, results, and potential implications without having to read the full scientific paper.

Kidney stones are common worldwide. The study notes that the lifetime risk of urolithiasis can reach 10–15% in developed countries and up to 20–25% in parts of the Middle East. The authors report that after a first episode, about half of patients may develop another stone within 5–10 years if no medical treatment is used. Because stones tend to recur and can cause pain, infection, or require procedures, the burden on health systems is substantial.

In recent decades, open surgery for renal stones has been largely replaced by less invasive methods such as extracorporeal shockwave lithotripsy (ESWL) and percutaneous techniques. These can be effective but may still cause complications like residual fragments, infection, or kidney injury. The authors point out that medical strategies are sometimes overlooked, even though they may help, especially when diet changes alone are not enough.

Potassium citrate (PC) is already well known as a preventive treatment. Earlier research has shown that PC can reduce the risk of stone recurrence by raising urinary citrate levels, increasing urine pH, and lowering the chance of crystal formation. Low urinary citrate (hypocitraturia) is a recognized risk factor for stones, and PC helps correct this. The scientific paper notes that PC is often considered the most tolerable and effective citrate preparation. However, far fewer studies have looked at potassium citrate as a therapeutic tool to actively shrink or dissolve existing stones, especially stones of various types, not just uric acid stones. This gap motivated the authors to test whether PC could be used as a non-surgical treatment for small renal stones.

The researchers conducted a prospective clinical study at the Urology Department of Sina Hospital in Tehran, Iran. Adults diagnosed with kidney stones smaller than 1 centimeter, or 10 millimeters, between June 2018 and December 2018 were considered for inclusion. All participants provided written informed consent, and the trial was registered in the Iranian Registry of Clinical Trials.

Patients were excluded if they had conditions that might make potassium citrate unsafe or less effective. Exclusion criteria included poorly controlled diabetes, chronic diarrhea, a history of hyperkalemia, certain medications such as digoxin or levodopa, reduced kidney function (glomerular filtration rate below 70 mL/min), pregnancy, multiple stones, previous kidney stones, solitary kidney, cystine stones, stones 10 mm or larger, or prior kidney transplantation.

In total, 56 patients (mean age about 43.7 years; about 52% female) with 86 small renal stones were enrolled. Some patients had one stone, and some had two. Stone size and location (upper, middle, or lower calyx) were determined by ultrasonography or computed tomography (CT) scans. Blood tests and urine culture ruled out infection and checked kidney function and blood glucose.

All patients received potassium citrate tablets (Alithoral 10, 10 mEq) three times a day for eight weeks. They also received lifestyle advice: reduce sodium and oxalate-rich foods, drink at least two liters of water daily, and keep calcium intake in a normal range. Serum electrolytes and urine pH were checked every four weeks. The dose of potassium citrate was adjusted to keep urine pH between 6.8 and 7.2. If urine pH rose above 7.2, the dose was reduced; if it dropped below 6.8, the dose was increased.

After eight weeks, patients were re-evaluated with an ultrasound by the same experienced radiologist. Stones that had fully disappeared were recorded as “completely dissolved.” Patients whose stones remained continued the same regimen for another eight weeks and were re-assessed at 16 weeks. The main outcome was a change in stone size and the number of stones that became stone-free.

At the first follow-up visit after eight weeks of potassium citrate therapy, 42 stones were reported as completely dissolved. By the second visit at 16 weeks, another 25 stones had dissolved. Overall, a large majority of stones under 10 millimeters became stone-free over the course of the study.

The average stone size also dropped significantly. The authors report that the mean largest diameter decreased from about 5.13 mm at baseline to 1.96 mm after eight weeks, and further to 0.79 mm after 16 weeks among the remaining stones. The p-value for these changes was less than 0.001, indicating strong statistical significance. The scientific paper concludes that “potassium citrate plays a crucial role in pulverizing and also in the reduction of the dimensions of the renal stone.”

Stones were located in the inferior, middle, or upper calyces of the kidney. Most were in the middle calyces. When the team analyzed size changes by location, they found that stones in the middle and lower calyces shrank significantly over time. In contrast, stones in the upper calyces did not show a statistically significant reduction in size. The authors did not find major changes in stone location during follow-up.

n the discussion, the authors compare their findings to previous work on the natural course of small, asymptomatic stones. They cite a study by Li and colleagues in which only 20% of stones with an average size of 5.7 mm passed spontaneously over a mean follow-up of 46 months. In contrast, this study reported that about 88% of renal stones with a mean size of 5.13 mm dissolved within 16 weeks of potassium citrate treatment, which the authors interpret as a strong therapeutic effect.

The scientific paper also places these results in the context of earlier preventive trials using alkali citrate, which reduced stone formation rates by roughly 47–100% in uncontrolled studies. Here, the focus is on active dissolution and size reduction of existing stones smaller than 10 millimeters.

Potassium citrate was generally well tolerated. Previous literature has reported mostly gastrointestinal side effects such as bloating, gas, or diarrhea, especially with liquid formulations. In this study, the tablet form of potassium citrate (Alithoral) was used, and only a few patients reported mild gastrointestinal complaints, which improved after dietary advice.

Because potassium citrate can change electrolytes and urine pH, the authors stress the need for monitoring blood tests and urine pH during treatment. They note that overly alkaline urine may increase the risk of calcium phosphate stones, so keeping urine pH in the target range is important.

This scientific paper suggests that potassium citrate may offer more than just the prevention of recurrence. In patients with renal stones smaller than 10 millimeters, potassium citrate tablets, combined with diet and fluid advice, were associated with substantial reductions in stone size and a high stone-free rate over 16 weeks. The authors suggest that this approach may reduce the need for procedures such as ESWL or surgery in selected patients, especially when stones are relatively small and kidney function is preserved.

At the same time, the study has important limitations. There was no control group for direct comparison, and follow-up lasted only a few months. The researchers also did not perform 24-hour urine metabolic testing, which would have provided more detail on how potassium citrate changed urine chemistry. Because the study did not restrict itself to a specific stone composition, the exact response of different stone types (for example, calcium oxalate versus uric acid) remains unclear.

The authors call for larger, controlled studies with longer follow-up to confirm how effective potassium citrate is for active dissolution, which patients benefit the most, and how best to monitor safety.

This scientific paper reports that potassium citrate tablets used for up to 16 weeks were linked with marked shrinking and frequent dissolution of kidney stones under 10 millimeters in a group of 56 adults. Many stones became completely stone-free, the average stone size dropped from just over 5 mm to well under 2 mm and then below 1 mm, and side effects were mostly mild and digestive in nature.

These findings suggest that potassium citrate may be viewed as a potential non-surgical management approach for selected patients with small renal stones, in addition to its established role in preventing recurrence in clinical practice. However, because this study lacked a control group and had a relatively short follow-up, potassium citrate should still be seen as a promising therapy supported by growing evidence, rather than a guaranteed solution for every patient with kidney stones.