Reduction of ureteral stent encrustation by modulating the urine pH and inhibiting the crystal film with a new oral composition: a multicenter, placebo controlled, double blind, randomized clinical trial

BMC Urol. 2020 Jun 5;20(1):65. doi: 10.1186/s12894-020-00633-2.


Background: Encrustation of ureteral double J stents is a common complication that may affect its removal. The aim of the proposed study is to evaluate the efficacy and safety of a new oral composition to prevent double J stent encrustation in indwelling times up to 8 weeks.

Methods: A double-blinded, multicenter, placebo-controlled trial was conducted with 105 patients with indwelling double J stents enrolled across 9 public hospitals in Spain. The patients were randomly assigned (1:1) into intervention (53 patients) or placebo (52 patients) groups for 3 to 8 weeks and both groups self-monitored daily their morning urine pH levels. The primary outcome of analysis was the degree of stent ends encrustation, defined by a 4-point score (0 - none; 3 - global encrustation) using macroscopic and electron microscopy analysis of crystals, after 3 to 8-w indwelling period. Score was exponentially transformed according to calcium levels. Secondary endpoints included urine pH decrease, stent removal, and incidence of adverse events.

Results: The intervention group benefits from a lower global encrustation rate of stent ends than placebo group (1% vs 8.2%; p < 0.018). Mean encrustation score was 85.12 (274.5) in the placebo group and 18.91 (102.27) in the intervention group (p < 0.025). Considering the secondary end points, treated patients reported greater urine pH decreases (p = 0.002). No differences in the incidence of adverse events were identified between the groups.

Conclusions: Our data suggest that the use of this new oral composition is beneficial in the context of ureteral double J indwelling by decreasing mean, as well as global encrustation.

Trial registration: This trial was registered at under the name "Combined Use of a Medical Device and a Dietary Complement in Patient Urinary pH Control in Patients With an Implanted Double J Stent" with date 2nd November 2017, code NCT03343275, and URL.

Keywords: Double J stent; Encrustation; L-methionine; Nutraceutical; Phytin; pH.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial

MeSH terms

  • Administration, Oral
  • Adult
  • Calcinosis / etiology*
  • Calcinosis / prevention & control*
  • Crystallization
  • Double-Blind Method
  • Female
  • Humans
  • Hydrogen-Ion Concentration
  • Male
  • Methionine / administration & dosage*
  • Middle Aged
  • Phytic Acid / administration & dosage*
  • Postoperative Complications / etiology*
  • Postoperative Complications / prevention & control*
  • Prospective Studies
  • Prosthesis Failure
  • Stents / adverse effects*
  • Ureter / surgery*
  • Urine / chemistry


  • Phytic Acid
  • Methionine

Associated data