Hypothesis / aims of study
This study aimed to evaluate the clinical effectiveness of oral citrate-based chemolysis in managing presumed uric acid staghorn nephrolithiasis. Given the radiolucent nature of these stones and their association with low urine pH, conservative therapy may serve as a viable alternative to surgery in selected patients.
Study design, materials and methods
This prospective multicenter cohort study was conducted from January 2023 to October 2024 across outpatient and inpatient urological clinics in Moscow. Adult patients with radiologically suspected uric acid staghorn calculi were enrolled. Inclusion criteria included urine pH ≤ 5.8, stone radiolucency on plain X-ray or CT topogram, and non-contrast CT density ≤ 650 Hounsfield units (HU).
Patients received oral chemolysis therapy using a commercially available citrate-based preparation (Blemaren), containing citric acid, sodium citrate, and potassium bicarbonate. The treatment protocol included regular urine pH monitoring and metabolic adjustment to maintain urine pH between 6.2 and 6.8.
Stone composition was later confirmed in surgically treated patients. Imaging follow-up was performed at 1, 3, and 6 months using low-dose non-contrast CT. Complete dissolution or need for surgical intervention was documented.
Results
Out of 49 enrolled patients, 2 were excluded during early follow-up due to loss to follow-up. Among the remaining 47 patients, complete stone dissolution was achieved in 30 cases (63.8%), while 17 patients (36.2%) required surgical intervention. Of those who responded to therapy, 4 patients (8.5%) achieved full dissolution within 1 month, 18 patients (38.3%) within 3 months, and 8 patients (17%) by 6 months.
Among patients who underwent surgery, stone analysis revealed 12 (70.6%) calcium oxalate and 5 (29.4%) uric acid stones. Thus, only 14.3% of patients with confirmed uric acid composition failed conservative therapy. Stone density was the only parameter with statistically significant influence on outcomes (p < 0.05). Regression analysis showed that each unit increase in stone density reduced the likelihood of complete dissolution by a factor of 1.012 and increased the likelihood of surgical intervention by a factor of 1.008.
Interpretation of results
Oral citrate-based chemolysis demonstrated favorable outcomes in carefully selected patients with suspected uric acid staghorn stones. Imaging parameters, particularly low HU density, proved essential in predicting treatment success. While not universally effective, chemolysis avoided surgery in nearly two-thirds of patients and provided a safe, non-invasive management strategy.