Potassium Citrate as a Preventive Treatment for Double-J Stent Encrustation: A Randomized Clinical Trial

Introduction

Nowadays, ureteral stents have become inseparable from urologists' routine practices (1). The ureteral stent has been employed as adjuvant therapy in the treatment of renal stones and urinary obstruction, identification of the ureter during surgery, and handling of urinary leakage (2). Although a broad spectrum of ureteral stents is used in urological settings, they may be associated with various complications, including, but not limited to, stent discomfort, infection, encrustation, and stone formation (2, 3).

Stent encrustation over Double J (DJ) stent is a prevalent complication of ureteral stenting  (2, 4). The incidence of encrustation has a positive association with the DJ stent indwelling time (5). Stent encrustation can cause urinary infection (6), reconstruction (7), and even renal failure (8); therefore, it has the potential to be detrimental to patients' health (9, 10).

The applicability of potassium nitrate to reduce urolithiasis recurrence has been investigated in several studies, and virtually all of them have emphasized a significant reduction in renal stones through this approach (11-13). Moreover, high clearance rates of stones can be expected using potassium citrate through several mechanisms, including modulating the concentrations of urine electrolytes and saturation of calcium oxalate (14). Encrustation and resultant urine stones are common following stent insertion. Because potassium citrate is of proven value in reducing the rate of renal stones formation, we designed a randomized clinical trial to assess whether potassium citrate can decrease stent encrustation in patients with ureteral stents.

Methods

A total of 70 patients with ureteral stones were enrolled and underwent transurethral lithotripsy at the Urology Department of Sina Hospital in 2020. The study was under the Tehran University of Medical Sciences Ethical Committee after receiving the Iranian Randomized Clinical Trial code (IRCT20190624043991N8). Patients enter the study after signing the written informed consent. All the enrolled patients were indicated for transurethral lithotripsy and randomized to two groups. The exclusion criteria for our study were as follows: 1. Any metabolic abnormality; 2. Digoxin use; 3. History of hyperkalemia; 4. Pregnancy; 5. Calcium supplements usage; 6. Potassium-sparing diuretics; 7. Levodopa prescription; 8. Serum potassium higher than five mmol/l; 9. Glomerular filtration rate lower than 70 ml/min; 10. Patients are treated with citrate potassium for any reason. 

After confirming the inclusion and exclusion criteria, we explained to the patients that their information would only be used to conduct a research project approved by the ethics committee of Tehran University of Medical Sciences, and their written and informed consent was obtained for this purpose. After transurethral lithotripsy, the patients were randomly divided into intervention (n=35) and control group (n=35) using permuted balanced block randomization method (blocks of 4). The intervention group consisted of those who received double-J stents plus ten mEq Alithoral tablets (potassium citrate) three times a day from insertion until double-J removal (Figure 1). The control group included patients receiving only double-J stents with no potassium citrate. Moreover, we recommended that all the patients continue their routine eating habits, reduce sodium and foods rich in oxalate, consume at least two liters of water per day, and have regular calcium intake. To keep the urine pH in the intervention group between 6.8 and 7.2, we measured it every two weeks. The dosage of Alithoral increased to 40 mEq per day if urine pH was lower than 6.8, and if it was higher than 7.2, we decreased the dose of Alithoral to 20 mEq.

Figure 1. Flow diagram of the progress through the phases of a parallel randomized trial of the two target groups.

Moreover, we controlled patients' electrolytes in the intervention group every two weeks to prevent hyperkalemia. All patients were evaluated visually for the formation of stones and crusts on double-J stents at the time of double-J stent removal. Also, double-J stents were sent to the laboratory to assess stones and crust formation. For patients with encrustation, the composition of double-J stent encrustation was analyzed. Moreover, blood and urine samples were taken to evaluate crystalluria, creatinine, and pyuria. Patients' demographic information, including age, gender, smoking habits, recurrent formation of urinary stones, the stone composition (calcium oxalate), and type of double-J (one-way or two-way), were recorded. We also compared the patients of both groups for easy removal of the DJ stent, which was defined as DJ stent extraction without any resistance. 

Statistical analysis

Continuous variables were reported using the median (interquartile range) and the discrete ones (percent). Moreover, to compare these two types of variables between intervention and control groups, nonparametric tests of comparing medians and Chi-squared test were used, respectively. Because a binary variable is designated as the response variable, logistic regression was used to assess the impact of covariates on this dependent variable, and then the odds ratios (ORs) produced by this model and reported in the results.

Results

Due to missing follow-up, three control group participants were excluded from our study. The control and intervention groups were matched for age and sex, duration of the double-J placement, and the number of attack episodes. The median ages of the intervention and control groups were 41 (37-56) and 43 (33-55) years, respectively. Nearly 71.5% of the intervention group and 65.5% of the control group were men. There were no differences concerning crystalluria, renal stone composition, smoking, and type of double-J between the two groups. Although the removal of the double-J stent was easier in patients of the intervention group than in the control group (91.2% and 87.5%, respectively), there were no significant differences between the two groups in this regard (P-value=0.465). There were substantial differences in creatinine, pyuria, and encrustation (Table 1).

Table1. Description of measured variables