Alkaline Citrate Medication to Prevent Stent
Encrustation in Urolithiasis Therapy
Department of Urology, Al-Bashir Hospital, Amman, Jordan
Yasin Idweini, Department of Urology Al-Bashir Hospital Amman Jordan, E-mail:
Received: July 09, 2016; Accepted: July 26, 2016; Published: August 05, 2016
Citation: Idweini Y (2016) Alkaline Citrate Medication to Prevent Stent Encrustation in Urolithiasis Therapy. J Urol Nephrol Open
Access 2(3): 1-4.
Objectives: We evaluated the clinical efficacy of long –term
preventive treatment of stent encrustation by using alkaline citrate
medication. The annual and cumulative rates of stents encrustation
were compared before and during the treatment
Material and Methods: We compared two groups of patients
in a retrospective study. First group from June2003 to June 2004,
82 patients were selected among 923 patients with urolithiasis
who underwent extracorporeal shock waves lithotripsy (ESWL)
and needed previously double J (J-J) insertion because of what are
the burden of stone >2cm or treating obstructive anuria due to
urolithiasis or after open surgery on the kidney and ureter for lithiasis
when needed. The second group from June 2010 to June 2011 who
have taken preventive alkaline K and Na citrate therapy to prevent
stent encrustation in addition to ESWL, this second group consisted of
130 patients were chosen from 1182 patients who underwent ESWL
therapy and they needed (J-J) insertion because of similar reasons of
the first group. Patient age ranged from 6 years to 73 years (mean
age 42years) in the first group. But in the second group patient age
ranged from 2 years to 80 years (mean age 37 years). Ratio male to
female was identical in both groups and was 59%: 41%.
Results: Stent encrustation was quantified by visual analog score
0 (none) to 4 (heavy).
Group 1: The mean stenting time was 6.2 months.
a) Score (0 and 1) none encrusted: 55 patients (67%).
b) Score (2, 3 and4) encrusted: 27 patients (33%).
Group 2: The mean stenting time was 8.6 months.
a) Score (0-1) none encrusted: 121 patients (93%).
b) Score (2, 3 and 4) encrusted: 9 patients (7%).
Conclusion: Alkaline medication, potassium and sodium citrate is
effective in preventing and reducing stent encrustation.
Keywords: Stent; Encrustation; Urolithiasis; Citrate
ESWL: Extracorporeal Shock Wave Lithotripsy; J-J Double
J Stent U/S: Ultrasound; CT: Computerized Tomography IVU:
Intravenous Urography; PCNL: percutaneous nephrolithotripsy
Zimskind, in 1967, was the first who prescribed endoscopic
stent placement to relieve ureteral obstruction . This early
era was plagued with frequent stent migration and device
expulsion. It was not until the year 1976; when the revolutionary
development of the Double J and pigtail stents independently by
Finney and Hepperten and colleagues (1978) , that the use
of ureteral stents witnessed widespread status . Since then
Ureteral stents became a fundamental tool in today's urologic
armamentarium and are prescribed for number of indications
including obstruction relief, prophylaxis against obstruction or
ureteral injury and is used as a ureteral splint. Stents are often
inserted to relieve either extrinsic (tumor, retroperitoneal
fibrosis) or intrinsic ureteral obstruction (stones, tumors,
strictures), as a temporary measure while definitive treatment
is instituted, or as permanent tool when no corrective treatment
is possible. Indications for pre- ESWL stenting are stone burden
greater than 2 cm, when bilateral ESWL is recommended to be
undertaken (at least one renal unit) and in solitary kidney's
All stents may cause morbidity such as flank pain, dysuria,
hematuria, infection, migration and encrustation. We reviewed
the literature on the subject of the encrusted stents; discussed
the risk factors for encrustation, and methods of preventing
thereof. We could identify variety of factors that contribute in
determining the occurrence rate of this process, the material of
the stent, urine composition and duration of using thereof. We
noticed that risk of stent encrustation is increased in patient with
a history of urolithiasis and at progressively longer indwelling
time . Selective medical therapy for nephrolithiasis is highly
effective in preventing new stone formation. Citrate efficacy for
the management of hyper uricosuric calcium nephrolithiasis may
stem from inhibitory activity of citrate with respect to calcium and
oxalate crystallization. We evaluated the clinical efficacy of longterm
preventive treatment of stent encrustation with alkaline
citrate medication. The annual and cumulative rates of stents
encrustation were compared before and during the treatment.
Material and Methods
We compared two groups of patients in a retrospective
study First group from June 2003 to June 2004, 82 patients were selected among 923 patients with urolithiasis who underwent
ESWL therapy and needed previously J-J insertion because of
whatever the burden of stone > 2cm or treating obstructive
anuria because of stone formation or after open surgery on the
kidney and ureter due to stones when needed. The second group
from June 2010 to June 2011 who has taken preventive alkaline
K and Na citrate therapy to prevent stent encrustation in addition
to ESWL this second group consisted of 130 patients who were
chosen from 1182 patients who underwent ESWL therapy and
they needed J-J insertion because of similar reasons of the first
group. Material of Stents in both groups was polyurethane which
shares characteristics common to both silicone and polyethylene
the first plastic polymer used in stents and the two companies
of stents we used to use were B. Brown from USA and Coloplast
from France. Patient age ranged from 6 years to73 years (mean
age 42 years) in the first group. But in the second group patient
age ranged from 2 years to 80 years (mean age37 years). Ratio
male to female was identical in both groups and was 59%: 41%.
Patients were evaluated monthly by KUB film; U/S, blood urea
and serum creatinine, urine analysis for each patient. Urine
culture, IVU, and coronal CT scan were done when indicated.
The administration of Uralyt-U granules (potassium sodium
hydrogen citrate) started at the first week of insertion of J-J.
Patients were instructed to take 1-4 spoons of granules (2.5 -
10gr) daily according to the pH of their fresh urine examined by
test strip of indicator paper daily in the early morning.
Stent encrustation was quantified by visual analog score 0
(none) to 4 (heavy)
Group I: The mean stenting time was 6.2 months
a) Score (0 and 1) none encrusted: 55 patients (67%).
b) Score (2, 3 and 4) encrusted: 27 patients (33%). (Figure
Group ΙΙ: The mean stenting time was 8.6 months.
a) Score (0-1) none encrusted: 121 patients (93%).
b) Score (2, 3 and 4) encrusted: 9 patients (7%) (Among
them those patients who did not comply the treatment
or had forgotten the stent).
No complications were recorded in our patients.
Alkaline medication, potassium and sodium citrate( group
two) about 3-fold (Odd- 2.8) significantly effective in
prevention and reducing stent encrustation compared with
group one (Considered significant when P- value < 0.05).
The ideal stent material should be biocompatible and
radiopaque, relieve intraluminal and extra luminal obstruction,
resist encrustation and infection, cause little discomfort to
the patient, and should be widely available at reasonable cost.
Currently, there is no stent material that meets all these criteria.
Minor degrees of encrustation, particularly on the bladder curl,
are not uncommon in many stented patients. More extensive
encrustation often relating to the forgotten/ retained stent can
be one of the most challenging tasks for the urologist requiring
various endourology interventions and sometimes open surgery,
and if are untreated, extreme degrees of encrustation may lead
to compromise of the renal unit and even patient mortality [7, 8]
.The duration of indwelling time seems to affect the rate of stent
encrustation with polyurethane stents. El-Faqih et al reported
an incidence of stent encrustation of (9.2%before 6 weeks,
47.5% in 6-12 weeks, and 76.3% after 12 weeks) . Infection
and encrustation rise due to biofilm formation on the surface
of the stent, which occurs within hours after insertion [10, 11]
after a conditioning film coat, the surface of any foreign object
in the urinary system, glycoprotein, exopolymer and matrix
form a biofilm in which bacteria may become embedded. In our
department, while we use citrate; as medical alkaline therapy
in association to ESWL, in treating staghorn stones of uric acid
and insertion of J-J stent previously to prevent steine-strasse
obstruction, we noted that removal of stent was easier compared
to those patients without alkaline therapy, because of lack heavy
encrustation on it, in spite of long period of stenting. From that
time we started to use alkaline therapy in association to ESWL to
urolithiasis in general, when J-J stent insertion needed, providing
that alkaline citrate is indicated as pharmacological treatment of calcium oxalate stones according to the aetiology, as well as
hypercalciuria, hypocitraturia, enteric hyperoxaluria and distal
renal tubular acidosis as EAU guidelines mentioned in addition to
treating uric acid and ammonium urates stones, as well as support
treatment in cistinuria, we also noted the lack of encrustation on
stent in the majority of cases on removal . These results lead us
to conduct retrospective comparative study between two groups
of stented patients: one with ESWL therapy only and the other
with ESWL and alkaline therapy taking in consideration the base
evidence as we know from the literature that, potassium citrate
therapy may produce a sustained increase in urinary citrate and
a decline in the urine saturation of calcium oxalate. Citrate is an
important inhibitor that can reduce calcium stone formation
through several mechanisms: Citrate reduces urinary saturation
of calcium salts by complexing with calcium . Citrate directly
prevents spontaneous nucleation of calcium oxalate [13, 14].Citrate inhibits agglomeration and sedimentation of calcium
oxalate crystals [15, 16] as well as growth of calcium oxalate
and calcium/ phosphate crystals. Ultimately, normal urinary
citrate levels can enhance the inhibitors effect of Tamm- Horsfall
glycoproteine . And as we know hypocitraturia is an important
and correctable abnormality associated with nephrolithiasis that
exists as an isolated abnormality in up to 10% of calcium stone
formers and is associated with other abnormalities in 20% to
60% [18, 19] and we may correct this underlying cause of lithiasis
by using alkaline therapy to prevent encrustation as stated
hereinabove. An interesting observation deserves mentioning
herein, is that not all stents become encrusted, even after long
indwell times. In a series of patients who had an indwelling stent
for more than 1 year (mean 36 months), Park and colleagues
(2004) found this occurred in only 33% of the stents . In
our series, in the first stented group treated by ESWL only, the
rate of encrusted stent was 33% (27 patients) is identical to the
reported series ratio. Regarding to the second group treated
by ESWL and citrate medication, the rate of encrusted stent
was 7% (9 patients), among them those patients who did not
comply the alkaline treatment or had forgotten the stent with
calcification all over the stent, which also were treated by ESWL
and citrate medication, and in this group the removal of stent was easier because of mild encrustation seen on it. Management
of the retained encrusted ureteral stent may require multiple
procedures; many options include chemolisis, ESWL, endoscopic
lithotripsy, PCNL, open lithotomy and nephrectomy. In our series
we did not need in the second group any further treatment
than ESWL and citrate. We have taken a policy in our hospital
to add a new indication for alkaline citrate medication which is
reducing of ureteral stent encrustation in addition to lithotripsy.
Stent encrustation and management challenges even
experienced urologist. The key to prevent this problem is to
Table 1: Demographic baseline and treated patients characteristics:
Gender:-Male N. (%)
Female N. (%)
37years,(2 - 80y)
Age, years, median,(range)
Rt. Side N. (%)
Lt. Side N. (%)
Bil. N. (%)
Non-encrusted stent N (%)
Encrusted- stent N. (%)
Statistical Analysis: First Group; 55(67%), 27(33%)
Second Group: 121(93%), 9 (7%)
Chi Square (χ2 )=24.12 P-value < 0.0001
give preventive alkaline medication, potassium and sodium
citrate, they are equally effective in preventing uric acid stone
formation because of their ability to increase both urinary Ph and
its inhibitor effect on spontaneous nucleation of Ca oxalate and
growth of Ca phosphate crystals interrupting stone formation,
stent encrustation and decrease stent blockage in the long run.
- Zimskind P D, Fetter TR, Wilkerson J L. Clinical use of long-term indwelling silicone rubber ureteral splints inserted cystoscopically. J. Urol. 1967;97:840.
- Finny RP. Experience with new double J ureteral catheter stent. Jr. Urol 1978;120(6):678-81.
- Chew B H, Duvdevani M, Denstedt J D. New developments in ureteral stent design material and coating . Expert Rev Med Devices. 2006;3(3):395-403.
- Libby J M , Meacham R B, Griffith D P. The role of silicone ureteral stents in ESWL of large renal calculi. J Urol. 1988;139(1):15-7.
- Sulieman M N, Buchholz N P, Clark P B. The role of ureteral stent placement in the prevention of steinstrasse. J of Endourology. 2009;13(3):151-155. doi:10.1089/end.1999.13.151.
- Preminger G M, Assimos D G, Lingeman J E, Nakada S Y, Pearle M S, Wolf J S, et al. AUA guidelines on management of staghorn calculi diagnosis and treatment recommendations. J Urol. 2005;173(6):1991-2000.
- Walther P J, Robertson C N, Paulson D F. Lethal complications of standard self-retaining ureteral stent in patients with ileal conduite urinary diversion. J Urol. 1985;133(5):851-3.
- Singh V, Srinivastava A, Kapoor R, Kumar A. Can the complicated forgotten indwelling ureteric stents be lethal? Int Urol Nephrol. 2005;37(3):541-6.
- El-Faqih S R, Shamsuddin A B, Chakrabarti A, Atassi R, Kardar A H, Osman M K, et al: Polyurethane internal ureteral stents in treatment of stones patients: morbidity related to indwelling times. J Urol. 1991;146(6):1487-91.
- Tieszer C, Reid G, Denstedt J. Conditioning film deposition on ureteral stents after implantation. J Urol. 1998;160(3 Pt 1):876-81.
- Wollin T A, Tieszer C, Riddell J V, Denstedt J D, Reid G. Bacterial biofilm formation, encrustation, and antibiotic adsorption to ureteral stents indwelling in humans. J Endourol. 1998 ;12(2):101-11.
- Pak CY. Citrate and renal calculi: An update. Miner Electrolyte Metab. 1994;20(6):371-7.
- Preminger GM, Sakhaee K, Skurla C, Pak CY. Prevention of recurrent calcium stone formation with potassium citrate therapy in patients with distal renal tubular acidosis. J Urol. 1985 ;134(1):20-3.
- Sakhaee. Recent advances in the pathophysiology of nephrolithiasis. Kidney Int. 2009; 75(6):585-95. doi: 10.1038/ki.2008.626.
- Kok D J, Papapoulos S E, Bijvoet O L. Excessive crystal agglomeration with low citrate excretion in recurrent stones formers. Lancet. 1986;1(8489):1056-8.
- Tiselius H G, Fornander A M, Nilsson M A. The effects of citrate and urine on calcium oxalate crystal aggregation Urol Res. 1993;21(5):363-6.
- Hess B, Zipperle L, Jaeger P. Citrate and calcium effects on Tamm-Horsfall glycoprotein as modifier calcium oxalate crystal aggregation. Am J Physiol, 1993;265-f 784-f 791.
- Menon M, Mahle C J. Urinary citrate excretion in patients with renal calculi . J Urol. 1983;129, 1158-1160.
- Charles C, Pak, Candy Fullen B S, Idiopathic Hypocitraturic Calcium-Oxalate Nephrolithiasis Successfully Treated with Potassium Citrate. Ann Inter Med. 1986;104:33-37.
- Park and Colleagues (2004): Stent Encrustation, risk factors are urinary tract infection from Campbell-Walsh Urology- chapter-7 Fundamentals of instrumentation and urinary tract drainage.