Predictive value of urinary cultures in assessment of microbial colonization of ureteral stents

Bridging the knowledge gap: past, present and future of antibiotic use for ureteral stents

OBJECTIVE

To evaluate the available literature on ureteric stent-related infections, the use of antibiotics and bacterial colonisation to identify the current incidence of stent-related infections, unveil knowledge gaps and generate potential hypotheses for future research.

METHODS

A literature review was conducted using PubMed, Cochrane and urological association websites identifying relevant English literature published between 1983 and January 2024.

RESULTS

There is a worldwide lack of guidelines for antibiotic prophylaxis for stent placement, exchange or extraction. In patients with a negative preoperative urine culture undergoing ureteroscopy and stent placement, it may be considered to only provide prophylaxis in presence of risk factors. However, in pre-stented patients a preoperative urine culture is important to guide prophylaxis during endourological surgery. During stent indwell time, antibiotic prophylaxis does not show any advantage in preventing urinary tract infections (UTIs). There is no strong evidence to support the use of antibiotics at time of stent removal. In the absence of any clear evidence, management strategies for treating UTIs in patients with ureteric stents vary widely. Stent exchange could be considered to remove the biofilm as a potential source of bacteria. Stent culture can help to guide treatment during infection as urine culture and stent culture can differ.

CONCLUSION

In terms of good antibiotic stewardship, urologists should be aware that unnecessary use of antibiotics provokes bacterial resistance. There is a great need for further research in the field of antibiotic prophylaxis and stent-related infections to develop evidence that can help shape clear guidelines for this very common urological practice.

The effect of no oral antibiotic versus 7 days oral antibiotic during discharge in double J stented patients on stent related urinary tract infection: A randomized study

OBJECTIVE

To evaluate effects of 7 days oral antibiotic prophylaxis versus no antibiotics in the patients with DJ stents after 3 days iv antibiotic on discharge with respect to urinary tract infection and stent related symptoms.

MATERIAL AND METHODS

A prospective randomized study in 90 patients being stented post PCNL/URSL. Group A: no oral antibiotics was given at the time of discharge, Group B: 7 days of oral antibiotic was given at the time of discharge. Patients were followed up and outcomes were assessed in the form of lower urinary symptoms (LUTS), urine culture and sensitivity at 1 and 3 weeks and DJ stent culture and sensitivity on removal at 3 weeks.

RESULTS

There was no significant difference in age, gender, type of surgery (PCNL/URSL), duration of DJ stent between the two groups. Patients in group A and Group B have comparable UTI and stent related symptoms at 1 and 3 weeks respectively (p = 0.95 and p = 0.916 respectively). Similarly, there were no marked difference in urine culture at 1 and 3 weeks, respectively between two groups (p = 0.71 and p = 0.63, respectively). Overall there were no significant differences in Urinary symptoms, urine culture/sensitivity at 1 and 3 weeks and also DJ stent culture and sensitivity on removal at 3 weeks between the two groups.

CONCLUSION

The incidence of UTI and stent related symptoms are same in both the groups. Therefore, prescribing oral antibiotics on discharge in selected patient with DJ stent has no added benefit and should be avoided.

Bacteriuria in patients with stented ureters: predictors of infection in patients presenting to the hospital and when not to treat

PURPOSE

Patients with ureteric stents have symptoms that overlap with infection symptoms. Thus, clinicians unnecessarily give antibiotics to stented patients with bacteriuria despite guidelines. In stented patients, little is known about risk factors for developing bacteriuria or urosepsis. The objectives were to identify the frequency and risk factors for developing bacteriuria and urosepsis in patients with stents.

METHODS

In this retrospective cohort study, we reviewed patients with ureteric stents placed or exchanged over 1 year. We examined associations between bacteriuria or urosepsis and host risk factors. Univariable and multivariable logistic analyses were performed.

RESULTS

Of 286 patients (mean age: 57.2 years), 167 (58.4%) were male. The main stent indications were stone, stricture, cancer and extrinsic compression. The median stented period was 61 days. The frequency of bacteriuria was 59/286 (21%). ASA status 3 and 4 had 5 times the odds of having bacteriuria relative to ASA status 1. Stent duration > 2 months had 5.5 times the odds relative to ≤ 2 months. Urosepsis was infrequent, 13/286 (4.5%). Five patients had bacteraemia. A stent duration over 2 months had nearly 6 times the odds of urosepsis.

CONCLUSION

ASA status higher than 2 and stent time greater than 2 months raise the odds of developing bacteriuria. A stent duration longer than 2 months was the only predictor of urosepsis. Though 21% of patients had bacteriuria, 4.5% had urosepsis. Hence, bacteriuria without sepsis should not be treated with antibiotics, thus aiding antimicrobial stewardship.

Analysis of Pathogens of Urinary Tract Infections Associated with Indwelling Double-J Stents and Their Susceptibility to Globularia alypum

Ureteral double-J stents are frequently used to prevent urinary obstruction. They can develop bacterial colonization and encrustation, which leads to persistent infections that seldom respond to antibiotic treatment. Thus, the goal of this study was to evaluate the local spectrum of bacterial pathogens and their susceptibility to natural compounds. A total of 59 double-J ureteral stents from 59 consecutive patients were examined. The samples were inoculated on agar culture mediums. Extracts of Globularia alypum L. were evaluated for their antibacterial activity with the diffusion and broth dilution methods; for antibiofilm activity, the crystal violet assay was used. The identification and the quantification of the different constituents of extracts were determined by reverse-phase high-performance liquid chromatography (RP-HPLC). Bacterial growth was found in three patients (5.1%). Enterococcus faecalis (1.7%), Acinetobacter baumanii (1.7%), and Pseudomonas putida (1.7%) strains were more commonly detected. They were resistant to several common antibiotics. All extracts presented several components, mainly nepetin-7-glucoside and trans-ferulic-acid, and they had antibacterial activity (MIC = 6.25 mg/mL and MBC = 6.25 mg/mL), and antibiofilm (59.70% at 25 mg/mL) properties, especially against Acinetobacter baumanii. The results achieved confirm the important role of this plant as a source of therapeutic activities.

Optimal Dwelling Time for Ureteral Stents Placed for Passive Dilation after Impassable Ureteroscopy

INTRODUCTION

The aim of the study was to determine the correlation between the dwelling time for a ureteral stent placed for passive dilation after impassable ureteroscopy and success and complications.

METHODS

A retrospective evaluation was made of patients who underwent stent placement after impassable ureteroscopy and a repeat ureteroscopy due to kidney stones. A total of 161 patients were included in the study between 2015 and 2022. Demographic, clinical, preoperative, and perioperative data were collected. Logistic regression analyses were performed on the data showing a significant difference in the univariate analyses performed to determine the predictive factors of ureteroscopy after the stent dwelling period in terms of stone-free status and perioperative complications.

RESULTS

Stone-free status was achieved in 110 (68.3%) of 161 patients, and perioperative complications were observed in 41 (25.4%). Factors that affected the stone-free status were determined as the dwelling time and the S-ReSC score, while factors affecting perioperative complications were the stent dwelling time and the operation time. The stone-free rates were observed to increase from 46.4% in the first 2 weeks to 72.9% after the 2nd week, an increase of 1.5-fold. Perioperative complications were determined at the rate of 17.5% during the first 5 weeks and increased 2.1-fold to 37.5% after the 5th week.

CONCLUSION

It can be recommended that great care is taken during the stent dwelling period and ureteroscopy should be performed within 5 weeks (14-35 days) but no earlier than 2 weeks, so as not to affect the success of the procedure.

Ureteral Stent Colonization and Urinary Tract Infection in Children Undergoing Minimally Invasive Pyeloplasty

INTRODUCTION

 Minimally invasive pyeloplasty (MIP), namely, laparoscopic and robot-assisted interventions, has gained popularity in recent years. Double-J ureteral stents are frequently inserted during surgery. Foreign bodies in the urinary tract are considered as risk factor for developing urinary tract infection (UTI). This study aimed to specify the bacteria cultured from urine and stents responsible for UTI in children with indwelling ureteral stents undergoing MIP.

PATIENTS AND METHODS

 We retrospectively reviewed medical records of 30 children (22 boys and 8 girls) who had undergone MIP between 2014 and 2017. Median age at surgery was 2.7 years (interquartile range [IQR]: 0.5-7.9). Urine cultures were obtained before surgery, before stent removal, 1 month after stent removal, and if UTI was suspected. Stents were removed 4 to 8 weeks after surgery and cultured. Patients' demographics, types of stents, and surgical details were recorded.

RESULTS

 Median stent indwelling time was 5.09 weeks (IQR: 4-6). Postoperative febrile UTI developed in 4/30 (13%) patients. Afebrile UTI occurred in another 4/30 (13%) patients. Stent cultures were positive in 19/30 (63%) patients. Stent and urinary cultures were identical in only one patient. Three of four patients with preoperative asymptomatic bacteriuria developed postoperative UTI. There was no association between UTI, gender, stent diameter, and duration of indwelling catheter.

CONCLUSION

 After MIP, febrile UTI and afebrile UTI occurred in about one quarter of patients. Pathogens isolated postsurgically from urinary cultures were unrelated to those colonizing the stents. Therefore, routine stent culturing is of low clinical significance. Moreover, small-caliber stents and longer indwelling periods were not risk factors for UTI. Optimizing antibiotic treatment for children with preoperative UTI may potentially prevent morbidity after surgery.

Does bacterial colonization influence ureteral stent-associated morbidity? A prospective study

Objective

to evaluate the effect of bacterial colonization on ureteral stent-associated morbidity.

Methods

This was a prospective study that took place between February 2019 and March 2022. We examined one hundred fifteen patients for ureteric stents application. On the same day of stent removal, the Arabic version of Ureteral Stent Symptoms Questionnaire (USSQ) was used to assess stent-associated morbidity. The stent-associated morbidity and the specificity and sensitivity of culture in the stent and midstream urine were recorded.

Results

In 15.6% of the patients stent colonization was positive; E. coli was the most common isolated organism. There was no statistically significant difference between sex, age, irrigation fluid volume and duration of operation for stent colonization. However, stent indwelling time was significantly higher in patients with stents with positive cultures. In the colonized stents, there was a statistically significant difference with regards to the total score of USSQ, pain, urinary symptoms, work performance and additional problems of USSQ. Meanwhile, there was no statistically significant difference in the general health and sexual matter.

Conclusions

stent colonization may be a contributing factor in stent-related morbidity. Stent bacterial colonization increases with the time of stent retention. Stent cultures are not needed as the same microorganisms are detected in urine cultures.

Interactive Effects of Copper-Doped Urological Implants with Tissue in the Urinary Tract for the Inhibition of Cell Adhesion and Encrustation in the Animal Model Rat

The insertion of a ureteral stent provides acute care by restoring urine flow and alleviating urinary retention or dysfunction. The problems of encrustation, bacterial colonization and biofilm formation become increasingly important when ureteral stents are left in place for a longer period of time. One way to reduce encrustation and bacterial adherence is to modify the stent surface with a diamond-like carbon coating, in combination with copper doping. The biocompatibilities of the Elastollan^® base material and the a-C:H/Cu-mulitilayer coating were tested in synthetic urine. The copper content in bladder tissue was determined by atomic absorption spectroscopy and in blood and in urine by inductively coupled plasma mass spectrometry. Encrustations on the materials were analyzed by scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. A therapeutic window for copper ions of 0.5–1.0 mM was determined to kill bacteria without affecting human urothelial cells. In the rat animal model, it was found that copper release did not reach toxic concentrations in the affecting tissue of the urinary tract or in the blood. The encrustation behavior of the surfaces showed that the roughness of the amorphous carbon layer with the copper doping is probably the causal factor for the higher encrustation.

Primary versus delayed ureteroscopy for ureteric stones: A systematic review and meta-analysis

Background:

Ureteric colic is a major clinical and economic burden on the National Health Service. There has been a recent paradigm shift to consider definitive surgery as the primary intervention at the time of initial presentation.

Objective:

To systematically evaluate the outcomes of primary/emergency ureteroscopy versus delayed/elective ureteroscopy.

Methods:

We performed a critical review of MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials–CENTRAL, CINAHL, Clinicaltrials.gov, Google Scholar and individual urological journals in April 2020. A robust database search was performed using a combination of the terms ‘primary ureteroscopy’, ‘immediate ureteroscopy’, ‘delayed ureteroscopy’ and ‘emergency ureteroscopy’. Adult patients (> 16 years) with ureteric stones presenting as an emergency were included.

Results:

Twelve studies met the inclusion criteria, with 4 studies directly comparing primary/emergency to delayed/elective ureteroscopy for an acute presentation of ureteric colic. Across the studies, 1708 patients underwent primary/emergency ureteroscopy for ureteric calculi and 990 underwent delayed ureteroscopy. No significant differences in stone-free rates were found between both groups with primary/emergency achieving 85% and delayed/elective 91% ( p = 0.68). The majority of stones treated were located in the distal ureter in both groups. Overall, there were no differences in complications between the groups ( p = 0.42) or major complications (0.17). However, there were fewer minor complications in the primary URS group ( p = 0.02). Ureteral catheter or double-J stent insertion was used in 71% of delayed/elective ureteroscopy cases, compared to 46.8% of primary/emergency cases (p = 0.001). For patients undergoing primary/emergency ureteroscopy, 6.4% patients required auxiliary procedures. In the delayed/elective group, 7.6% required further definitive treatment (NS).

Conclusion:

Primary ureteroscopy is a safe and feasible procedure, when performed in suitable patients in the acute setting. It is associated with significantly lower stent usage, equivalent stone clearance, no increase in overall or major complications including sepsis, and fewer minor complications when compared to delayed/elective ureteroscopy. Prospective studies will do well to explore this area further but on current evidence, primary ureteroscopy is the safe procedure.

Level of evidence:

Not applicable

Optimum duration of ureteral prestenting dwelling time in children undergoing retrograde intrarenal surgery

INTRODUCTION AND OBJECTIVES

Ureteral prestenting before retrograde intrarenal surgery (RIRS) causes passive dilatation of the ureter, improves stone-free rate and is associated with shorter operative time. However, the presence of a ureteric stent may increase the risk for septic complications, which accelerates with increased dwelling time duration. The aim of the present study is to explore the impact of ureteral prestenting timing in a group of children undergoing retrograde intrarenal surgery (RIRS) on perioperative outcomes and complication rates and to define the optimum duration of prestenting dwelling time.

PATIENTS AND METHODS

A retrospective study on 60 children aged less than 14 years, presented with upper tract urinary stones, who were subdivided into two groups: Group 1 and 2, each included 30 children who had undergone RIRS after ureteric stenting for two weeks and four weeks respectively. Success of ureteroscope introduction, operative time, stone free rate (SFR), intraoperative and postoperative complications and number of retreatment procedures after definitive RIRS were recorded and compared between the two treatment groups.

RESULTS

Ureteric access was successfully obtained in all children in both groups. Patients in group 1 and 2 had a SFR of 86.6% and 90%, respectively (p = 0.199). The mean operative time of group 1 and 2 were 56.5 and 52.9 min (p = 0.612). Postoperative UTI rates increased with prolonged dwelling time from 6.7% in group 1 to 30% in group 2. No patient in both groups developed high grade complications.

CONCLUSIONS

Increasing prestenting dwelling time from two to four weeks had no statistically significant effect on the successful ureteroscopic access nor the stone free rate in children undergoing RIRS. Reducing the ureteric stent dwelling time minimizes the rate of postoperative UTI without compromising the success of operative outcomes.

Effects of Continuous Catheterization on Reducing Postoperative Urinary Tract Infection in Cervical Cancer Patients with Double J Stent Placement

This study aims at exploring the effect of continuous catheterization on reducing postoperative urinary tract infection in cervical cancer patients with double J tube placement. To be specific, a retrospective analysis was performed on 120 cases of cervical cancer patients who underwent laparoscopic or open radical hysterectomy in Shengjing Hospital of China Medical University from January to December 2019. They were divided into a persistent group (n = 70) and a short-term group (n = 50) according to indwelling catheter time. The incidence of postoperative complications and the positive rate of bacterial culture in bladder urine and double J tube bacterial culture were compared between the two groups. As a result, it was found that the incidence of postoperative fever and urinary tract infection in the short-term group was significantly higher than that in the persistent group (P < 0.05). There was no significant difference in the incidence of postoperative hematuria, bladder stimulation, and urinary system injury between the two groups. The positive rate of double J tube bacterial culture in both groups was also proved to be higher than that in bladder culture, and the difference was statistically significant (P < 0.05). And in the short-term group (P < 0.05), the difference in the positive rate of bladder culture between the two groups was not statistically significant. To conclude, we found that continuous catheterization can reduce the incidence of postoperative urinary tract infection in cervical cancer patients with double J tube placement, which might be helpful for the treatment of cervical cancer.

Risk factors in bacterial colonization of internal ureteral stent

A ureteral stent is most broadly used to manage upper urinary tract disorders such as obstruction and prevent post-endoscopic complications. However, the stent may become a niche for bacterial colonization. This study aimed to determine the rate of bacterial colonization and type of bacteria in internal ureteral stents and the risk factors associated with bacterial colonization. This prospective cross-sectional study included 100 consecutive adult patients who had temporary ureteral stenting as preparation for a secondary ureterorenoscopy at Al-Yarmook Hospital/ Baghdad. All included patients were negative for bacterial culture before stenting. Stent and urine culture were performed at the time of stent removal. The colonization rate and bacteriuria in patients with internal ureteral stent were 19% and 9%, respectively. The most common bacteria in-stent and urine were E. coli accounting for 31.58% and 33.33%. Pseudomonas aeruginosa was common in stent culture, representing 21.05%. Positive bacterial culture was confirmed in 19 stents and 9 urine samples. All cases with positive urine samples were also positive for culture. Thus, the sensitivity and specificity of urine culture for detection of stent colonization were 47.37% and 100%, respectively. Diabetes mellitus, chronic renal failure, and prolonged stenting were significantly associated with increased stent colonization. The ureteral stent could be a source of urinary tract infection. The most pathogenic bacteria associated with the ureter stent are E. coli and Pseudomonas aeruginosa. Risk factors associated with stent colonization are diabetes mellitus, chronic renal failure, and prolonged indwelling time.

Prospective Evaluation of Antibiotic Management in Ureteral Stent and Nephrostomy Interventions

INTRODUCTION

Screening for and treating asymptomatic bacteriuria (ABU) or administering antibiotic prophylaxis is recommended during ureteral stent and nephrostomy interventions. This study investigates the frequency of postinterventional infectious complications to gain insight into the need for antibiotics.

METHODS

Between September 2016 and June 2019, 168 insertions/exchanges of ureteral stents or nephrostomies were recorded in a prospective multicenter study. Patients without a symptomatic UTI did not receive antibiotic treatment/prophylaxis. Asymptomatic patients in whom their urologist already administered an antibiotic treatment served as a comparative group. Follow-up included postinterventional complications within 30 days. Symptoms were assessed by the Acute Cystitis Symptom Score (ACSS) before and after the intervention. Predictors of increasing postinterventional symptoms were analyzed by a multivariable logistic regression model.

RESULTS

One hundred forty-five interventions were eligible. One hundred twenty-two (84.1%) interventions were performed without antibiotic treatment. Preinterventional ABU was detected in 54.4% and sterile urine in 22.8% (22.8% without culture). Postinterventional infectious complications did not differ between patients with versus without antibiotics. Transurethral interventions aggravate symptoms (p = 0.034) but do not increase infectious complications compared to percutaneous interventions. Patients without diabetes mellitus are at higher risk for increasing symptoms.

CONCLUSION

Results indicate that peri-interventional antibiotic treatment may be omitted in patients without symptomatic UTI. Symptoms must be differentiated between infectious and procedure-associated origins.

Recommendations of the AFU Infectious Diseases Committee on the prevention, diagnosis and treatment of infections of endo-ureteral equipment

INTRODUCTION

No recent national guidelines exist regarding the management of urinary tract infections (UTIs) in the presence of ureteral stent. This situation could lead to discrepancies in clinical management and less opportunity for a favorable patient's outcome.

METHODS

All available data published on Medline® between 1998 and 2018 were systematically searched and reviewed. All papers assessing adult patients carrying ureteral stent were included for analysis. After studies critical analysis, national guidelines for clinical management were elaborated in order to answer clinical questions.

RESULTS

A total of 451 articles were identified, of which 58 have been included. The prevalence of urinary tract infections in the presence of ureteral stent remains unknown. After 3 months, all endo-ureteral devices were colonized on microbiological study. These patients also presented a positive urine culture in 25 to 70% of the cases, often polymicrobial. Staphylococci, E. coli, Klebsiella, Pseudomonas, Enterococcus and Candida were the commonest micro-organisms responsible for urinary colonization or infection. The risk of UTI on endo-ureteral devices seemed higher the longer it stayed implanted. There is no justification in the literature to recommend a systematic change of endo-ureteral devices following a urinary tract infection.

DISCUSSION

The existing literature is rich but of poor methodological quality, and therefore does not allow to draw robust conclusions. The greatest difficulty faced in this work was to accurately differentiate urinary colonizations from true infections, including clinical symptoms and not only microbiological results.

CONCLUSION

These guidelines propose a standardized management of such common clinical situations. Well-designed studies are needed to upgrade the level of evidence of these guidelines.

Epidemiology and risk factors for ureteral stent-associated urinary tract infections in non-transplanted renal patients: a systematic review of the literature

PURPOSE

Pathophysiology and risk factors for Ureteral Stent-Associated Urinary Tract Infection (USAUTI) have been poorly investigated. This situation results in highly diverse practices regarding USAUTI prevention, diagnosis and treatment. The aim of the present study was to describe the epidemiology and risk factors for USAUTI in non-transplanted patients.

METHODS

We conducted a systematic literature review based on a comprehensive PubMed® bibliographic strategy, between October 1998 and March 2020. The methodological quality of the studies included was analyzed according to dedicated grids. The main endpoints were the correlation between different potential risk factors and infection ureteral stent-associated urinary tract infection or colonization rate. Conclusions and their level of evidence were reported on the basis of a critical analysis of the best available scientific evidence. This work has been submitted to a national review, which enabled the potentially divergent opinions of experts to be collected, thereby ensuring adequate quality of data.

RESULTS AND CONCLUSION

Twenty-six studies out of the 505 articles identified, were included in the final analysis. Staphylococcus spp, E. coli, Klebsiella spp, Pseudomona aeruginosa, Enterococcus spp. and Candida spp. were the microorganisms most often responsible for asymptomatic bacteriuria (ABU) or USAUTI. Longer indwelling time, diabetes mellitus, female gender, chronic renal failure, diabetic nephropathy and cancer were identified as risk factors for ABU and ureteral stent colonization. No specific risk factor for UTI was identified in the literature studied. A causal relationship between ureteral stent colonization and USAUTI or urosepsis remains to be demonstrated.

Predictors of urosepsis in struvite stone patients after percutaneous nephrolithotomy

Purpose

This study aims to identify clinical factors that may predispose struvite stone patients to urosepsis following percutaneous nephrolithotomy (PCNL).

Materials and Methods

A retrospective review was conducted on patients who received PCNL for struvite stones. The Systemic Inflammatory Response Syndrome (SIRS) criteria and quick-Sepsis Related Organ Failure Assessment (q-SOFA) criteria were used to identify patients who were at an increased risk for urosepsis. Statistical analysis was performed using Fisher's exactness test, Wilcoxon rank test, and logistic regression.

Results

Chart review identified 99 struvite stone patients treated with PCNL. Post-operatively, 40 patients were SIRS positive (≥2 criteria) and/or q-SOFA positive (score ≥2). Using SIRS as an approximation for urosepsis, longer operative times (p<0.001), higher pre-operative white blood cell counts (p=0.01), greater total stone surface area (p<0.0001), and pre-operative stenting (OR, 5.75; p=0.01) were identified as independent risk factors for urosepsis. Multivariate analysis demonstrated pre-operative stenting (OR, 1.46; p=0.01) to be a risk factor. With q-SOFA, univariable analysis found that antibiotic use within 3 months prior to a PCNL (OR, 4.44; p=0.04), medical comorbidities (OR, 4.80; p=0.02), longer operative times (p<0.001), lengthier post-operative hospitalization (p<0.01), and greater total stone surface area (p<0.0001) were risk factors for urosepsis. Multivariate analysis revealed that bladder outlet obstruction (OR, 2.74; p<0.003) and pre-operative stenting (OR, 1.27; p=0.01) significantly increased odds of being q-SOFA positive.

Conclusions

Several risk factors for urosepsis following PCNL for struvite stones have been identified. These risk factors should be taken into consideration in peri-operative care to mitigate the risks of urosepsis.

Association between ureteric stent dwell time and urinary tract infection

BACKGROUND

Ureteric stone obstruction commonly presents to the emergency department, with definitive management often involving ureteroscopy and laser lithotripsy. Insertion of a ureteric stent prior to staged lithotripsy is commonly performed in the public healthcare system. Foreign bodies in the urinary tract are also known to increase urinary tract infection (UTI) risk. This study aims to evaluate the association between stent dwell time and UTI prior to lithotripsy.

METHODS

The medical records of all patients who were treated for ureteric stones with initial stent insertion and staged lithotripsy, from 1 January 2018 to 30 June 2019 at a single tertiary centre, by eight urologists were retrospectively reviewed. Demographic features, disease factors and urine culture data were collected and analysed.

RESULTS

Of the 172 patients (median age 56.7 years) identified, one-third had a positive pre-stent urine culture. Twenty-three percent had a positive pre-lithotripsy urine culture with 38% of females compared with 15% of males having a positive culture (P = 0.001). Only 4.3% of patients had a pre-lithotripsy UTI when the stent dwell time was less than 1 month compared with 26.2% when ureteric stents were in situ for longer than 1 month (P = 0.021). The correlation between ureteric stent dwell time and pre-lithotripsy UTI was not linear. Patient comorbidities, stone size, burden and location were not statistically correlated to pre-lithotripsy UTI.

CONCLUSION

In delayed two-staged surgical management of acute urolithiasis, optimal ureteric stent dwell time is less than 1 month to reduce pre-lithotripsy UTI. Female gender is an independent risk factor for pre-lithotripsy UTI.

Clinical significance of DJ stent culture in patients with indwelling ureteral stents prior to endourological intervention

BACKGROUND

Ureteral stents are placed to relieve ureteral obstruction in various endourological surgery. As soon as it is inserted it is rapidly colonized by host of microorganism. Culture and sensitivity pattern of these growing microorganism on the stent may provide us an insight to treat postoperative urosepsis in high risk patients with indwelling DJ stents.

MATERIALS AND METHODS

Prospective study between September 2018 and August 2019 with enrollment of 100 patients to determine the ability of urine culture (UC) to predict stent culture (SC) status, to identify associated infectious pathogens with their antibiotic sensitivity patterns and to evaluate the association between SC and post-endourological intervention sepsis.

RESULTS

Colonization of bacteria on stent culture (SC) was identified in 53 out of 100 patients (53%). Most of the organism grown on SC were multidrug resistant and they were resistant to most commonly prescribed antibiotics like fluroquinolones, cephalosporins, and aminoglycosides .These organisms were only sensitive to newer antibiotics. Indwelling time of ureteral stent was directly proportional with SC positivity (p < 0.05). Association of Urine culture at DJ Removal and DJ stent culture was not statistically significant.

CONCLUSION

Very low rates of colonization within 6 weeks after the insertion of stents. Sterile culture of urine does not rule out colonization of the stent. Most of the urinary pathogens as well as the organisms grown on DJ stent are resistant to fluroquinolones and cephalosporins.

The Interaction of Urinary Components with Biomaterials in the Urinary Tract: Ureteral Stent Discoloration

Purpose: Ureteral stents are fraught with complications. Not much is known regarding what causes these issues. Studies suggested that discoloration of indwelling stents changes surface characteristics to promote stent-associated complications. Occasional stent discoloration has been observed; however, underlying mechanisms and potential material changes are unknown. In this study, we identify a potential mechanism for stent discoloration and characterize potential changes in stent surface characteristics and their impact on encrustation and bacterial colonization. Materials and Methods: Twenty Polaris Ultra and 20 Percuflex Plus stents (same polymer material) with varying degrees of discoloration were collected from Japanese and Canadian patients. Surface characterization using scanning electron microscopy and Fourier transmission infrared spectroscopy was conducted. Encrustation of variably discolored stents was assessed via atomic absorption spectroscopy and bacterial adhesion to discolored and control stents via colony-forming unit counts. Results: Bismuth subcarbonate was found in control stents, and discoloration was induced via incubation in 1% sodium sulfide and increasing concentrations of hydrochloric acid (HCl) to produce hydrogen sulfide (H₂S). Discoloration of either patient-derived stents or in vitro discolored stents did not result in significant changes in stent material or increased rates of encrustation or bacterial adhesion. Conclusions: Ureteral stent discoloration may be triggered by sulfur containing urinary components reacting with bismuth subcarbonate in the stent material, rather than the surface deposition of unusual crystals as previously proposed. Stent discoloration does not result in increased levels of encrustation or bacterial adhesion. Given this, stent discoloration appears to be cosmetic and has no effect on the functionality of the indwelling stent.

Role of cultural analysis in patients with indwelling ureteral stent submitted to ureteroscopy for stones

BACKGROUND

Aim of our study is to analyze the incidence of postoperative infectious complications and to assess its predictors in patients with indwelling ureteral stent treated with ureteroscopy (URS).

METHODS

We retrospectively evaluated data of patients treated with URS from January 2017 to July 2018 at our center. We included 88 consecutive patients with available stent culture (SC) and urine culture (UC). Cefoxitin 2 g IV was given as prophylaxis in all patients with negative preoperative UC; otherwise, the choice of antibiotic was based on antibiogram. Ureteral stent was removed before URS procedure and analyzed. No postoperative antibiotic was given. Multivariable logistic regression analysis was built to assess preoperative predictors of postoperative infectious complications.

RESULTS

Nineteen patients (22%) developed postoperative infectious complications and fever was the most common one. E. faecalis, which is not responsive to common prophylaxis schemes in force in our institution, was the most frequent pathogen isolated. Overall, 26% of patients were found to have a discordance between SC and UC. At multivariable logistic regression analysis preoperative SC positivity (Odds Ratio [OR]: 11.00, 95% Confidence Interval [CI]:1.08-111.41, P=0.04) was the only significant predictor of postoperative infectious complications.

CONCLUSIONS

About one to five patients treated with URS developed an infectious complication and E. faecalis and E. coli were the most frequent pathogen isolated. A positive SC is the only independent risk factor for postoperative infection: consequently, an early SC analysis could allow a prompt antibiotic therapy in all patients with positive SC even if mildly symptomatic.

Detection of microbial colonization of the urinary tract of patients prior to secondary ureterorenoscopy is highly variable between different types of assessment: results of a prospective observational study

This study compares the findings of different detection methods for microorganisms in patients with ureteral stents undergoing secondary ureterorenoscopy including the use of a novel validated examination pipeline for biofilms on ureteral stents. Of the included 94 patients, 21.3% showed bacteriuria in preoperative urine cultures. Intraoperative urine culture showed bacteriuria in four (4.3%) of the patients. Stent biofilm cultures were positive in 12.9% and qPCR detected bacterial DNA in 18.1%. The findings of the different examinations were poorly correlated with each other. Detection of microorganisms in the urinary tract of patients with indwelling ureteral stents is highly dependent on timing (i.e. pre- vs intraoperative) and method of assessment. Preoperative routine urine cultures are not predictive for intraoperative urine- and stent culture. These results cast doubt on the clinical relevance of enterococcal species, staphylococci, and streptococci if identified preoperatively prior to stent removal. The timing of oral preoperative antibiotic prophylaxis might need to be reconsidered.

Fluorescent Capillary Electrophoresis Is Superior to Culture in Detecting Candida Species from Samples of Urinary Catheters and Ureteral Stents with Mono- or Polyfungal Biofilm Growth

Molecular techniques in fungal detection and identification represent an efficient complementary diagnostic tool which is increasingly used to overcome limitations of routinely used culture techniques. The aim of this study was to characterize Candida sp. representation in samples from urine, urinary catheter, and ureteral stent biofilm using ITS2 ribosomal DNA (rDNA) amplification followed by fluorescent capillary electrophoresis (f-ITS2-PCR-CE) and to compare the results with those obtained by culture. A total of 419 samples were analyzed, and 106 (25.2%) were found positive, out of which 17 (16%) were polyfungal. The positivity rate did not differ between samples from catheters and stents (23.6% versus 20.9%) or between catheter and stent corresponding urine samples (40.2% versus 30.2%). Ten different Candida species were detected, with Candida parapsilosis (31.4%), Candida albicans (26.5%), and Candida tropicalis (12.4%) predominating. f-ITS2-PCR-CE was evaluated as substantially less time-consuming and 8.3 times more sensitive than the routinely applied culture technique with 1 µl of urine/sonicated fluid inoculated, detecting 67 (19.9%) versus 8 (2.4%) positive samples out of 337 initially analyzed samples. The culture sensitivity considerably improved to 1.7 times lower than that of f-ITS2-PCR-CE after the inoculation volume was increased to 100 µl in the additional 82 samples. Moreover, the molecular technique, unlike routine cultivation, enabled precise pathogen composition determination in polymicrobial samples. In conclusion, the f-ITS2-PCR-CE method was shown to be a quick and efficient tool for culture-independent detection and identification of fungi in urinary tract-related samples, demonstrating a higher sensitivity than culture.

The clinical importance of fungal biofilms

Fungal biofilms have become an increasingly important clinical problem. The widespread use of antibiotics, frequent use of indwelling medical devices, and a trend toward increased patient immunosuppression have resulted in a creation of opportunity for clinically important yeasts and molds to form biofilms. This review will discuss the diversity and importance of fungal biofilms in the context of clinical medicine, provide novel insights into the clinical management of fungal biofilm infection, present evidence why these structures are recalcitrant to antifungal therapy, and discuss how our knowledge and understanding may lead to novel therapeutic intervention.

[Fungal infections and ureteral material: How to manage?]

INTRODUCTION

Urinary tract infections due to Candida species are mostly encountered in hospital environment. The management of candiduria on ureteral catheter is not consensual. The objective of our work was to make a review of medical literature related to definition, physiopathology, management and prevention of candiduria on ureteral catheter.

MATERIAL AND METHODS

The research was made on Medline using the following keywords: Candida; fungal; urinary tract infection; ureteral stent; ureteric stent; double-J pigtail.

RESULTS

The threshold defining candiduria is 10(5) CFU/mL. Candiduria corresponds to many different clinical presentations from colonization to candidemia. Species found are mostly Candida albicans (19-72%) and Candida glabrata (15.6-49.4%). The colonization of ureteral stent due to Candida is of 10% and comes with candiduria in 40% of the cases, due to the presence of biofilm. Prevention of infections on ureteral stents requires a regular change of material every 3-6 months depending on the patients risk groups. In case of symptomatic candiduria on ureteral stent, an anti-fungal therapy should be initiated 48 hours to 3 weeks before the change of the stent, in order to get a sterilization of urines and prevent the recolonization of the stent. Fluconazole is the drug of choice to use.

CONCLUSION

Colonization of ureteral stents due to Candida is common and can be responsible of symptomatic infection. Anti-fungal therapy should be introduced before the change of the stent but a consensual duration of treatment before surgery is not found in the literature.

Percutaneous nephrolithotomy for infection stones: what is the risk for postoperative sepsis? A retrospective cohort study

The purpose of this study was to compare the postoperative course of patients with positive stone culture (SC) to patients with sterile SC, and to analyze the predictors for post percutaneous nephrolithotomy (PCNL) sepsis; and to describe the type and resistance patterns of bacteria responsible for post PCNL sepsis. From a cohort of 206 consecutive patients undergoing PCNL, we identified 45 patients with a positive SC (group A) and compared them to patients with a sterile SC (group B). Association between different groups was assessed using Chi square, two-tailed Student's t test and Mann-Whitney U test, as appropriate. Twenty-three patients had postoperative sepsis and regression analysis was performed to identify clinical variables associated with sepsis. Demographics, stone load and hospitalization time were similar in both groups. Postoperative sepsis developed in 31.1% of patients in group A compared to 5.9% in group B. In multivariate analysis, only positive SC was an independent risk factor for postoperative sepsis (OR 6.894, 95% CI 2.31-20.59, P = 0.001). All patients responded well to treatment with no septic complications. Enterococci were the prevalent organism (29.4%) in patients with a positive SC. Quinolone resistance was high in both gram negative and gram positive bacteria. Patients with an infected stone are at high risk to develop postoperative sepsis despite standard preoperative antibiotic preparation. SC is important to direct further treatment as almost half of patients with positive SC have a discordant or sterile urine culture. Determining the prevalent bacteria and resistance patterns in SC can aid the selection of empiric antibiotic therapy in high-risk patients.

Rate of positive urine culture and double-J catheters colonization on the basis of microorganism DNA analysis

Introduction

The aim of the trial was to estimate the relationship between colonization of the Double–J catheter, and the microorganisms cultured from urine.

Material and methods

60 patients, who had Double–J catheters inserted, participated in the study. All the subjects had their midstream urine samples taken prior to the stent insertion and removal. A negative urine culture before catheterization was mandatory to participate in the study. The patients were assigned into three subgroups, according to stenting duration: 1) 20 to 30 days (18 cases); 2) 30 to 90 days (30 cases); 3) longer than 90 days (12 cases). Bacterial and fungal DNA was identified using electrophoresis in polyacrylamide gel with a denaturing gradient (PCR–DGGE). The relationship between the genetic analysis of the catheter and the urine culture was estimated.

Results

Urine cultures were positive in only 8 patients, while Double–J catheter analyses were positive in all cases. In 2 cases one type of microorganism was isolated from the stent surface while the remaining 58 catheters were colonized by more than one pathogen. In three cases fungi were isolated. There were only three types of pathogens cultured from urine specimens. Urine and stent cultures were consistent in 5 cases. In 3 cases urine culture and stent analysis were not consistent.

Conclusions

Double–J catheter retention in the urinary tract is associated with an extremely high risk of bacterial colonization, while the risk of urine infection is about 8–fold lower. There is a great inconsistency between urine infection and catheter colonization, indicating a low predictive value of urine culture for estimating stent colonization.

Comparison of the roll-plate and sonication techniques in the diagnosis of microbial ureteral stent colonisation: results of the first prospective randomised study

BACKGROUND

Microbial ureteral stent colonisation (MUSC) is one leading risk factor for complications associated with ureteral stent placement. As MUSC remains frequently undetected by standard urine cultures, its definitive diagnosis depends on microbiological investigation of the stent. However, a standard reference laboratory technique for studying MUSC is still lacking.

MATERIALS AND METHODS

A total of 271 ureteral stents removed from 199 consecutive patients were investigated. Urine samples were obtained prior to device removal. Stents were divided into four parts. Each part was separately processed by the microbiology laboratory within 6 h. Ureteral stents were randomly allocated to roll-plate or sonication, respectively, and analysed using standard microbiological techniques. Demographic and clinical data were prospectively collected using a standard case-report form.

RESULTS

Overall, roll-plate showed a higher detection rate of MUSC compared with sonication (35 vs. 28 %, p < 0.05) and urine culture (35 vs. 8 %, p < 0.05). No inferiority of Maki's technique was observed even when stents were stratified according to indwelling time below or above 30 days. Compared with roll-plate, sonication commonly failed to detect Enterococcus spp., coagulase-negative staphylococci (CoNS) and Enterobacteriaceae. In addition, sonication required more hands-on time, more equipment and higher training than roll-plate in the laboratory.

CONCLUSIONS

This prospective randomised study demonstrates the superiority of Maki's roll-plate technique over sonication in the diagnosis of MUSC and that urine culture is less sensitive than both methods. The higher detection rate, simplicity and cost-effectiveness render roll-plate the methodology of choice for routine clinical investigation as well as basic laboratory research.

How long should double J stent be kept in after ureteroscopic lithotripsy?

Ureteroscopic lithotripsy (UL), for renal or ureteral stones, is a standard technique for every urologist. However, the length of time the double J (DJ) stent needs to be kept in postoperatively is still controversial. This study investigated how the duration of DJ stenting after UL affects postoperative adverse events, especially infection and pain. One hundred and twenty-five patients were enrolled in this study and data were analyzed retrospectively. We set the median duration for keeping the DJ stent postoperatively as 14 days from median value in all cases and compared it to a longer duration group (>15 days) and a shorter duration group (<14 days) in terms of febrile complications, urinalysis, and the need to give antibiotics at the time of DJ stent removal. The duration of DJ stenting was from 3 to 61 (median 14) days. Thirteen patients had adverse events related to DJ stent removal (febrile complications, 11 patients; lumbago, 2 patients). Thirty-one patients were given antibiotics at the time of DJ stent removal. Patients with longer durations (>15 days) of DJ stenting had a significantly higher ratio of adverse events such as fever or lumbago (p = 0.041). In conclusion, this study demonstrated that shorter duration (<14 days) DJ stent use after UL may decrease adverse events and require less antibiotic use. Further prospective studies are needed to determine the optimal duration of DJ stent use after UL.

Characteristics and clinical significance of bacterial colonization of ureteral double-J stents in children

OBJECTIVE

To determine the frequency, type of pathogen and clinical significance of bacterial colonization of double-J stents after pyeloplasty in children.

PATIENTS AND METHODS

The medical files of 82 consecutive children (22 girls, 60 boys) who underwent pyeloplasty at a tertiary pediatric medical center in 2000-2007 were reviewed. Additional inclusion criteria were sterile urine preoperatively and placement of an indwelling double-J stent during surgery. Intravenous gentamicin was administered prior to pyeloplasty and stent removal; cephalexin was administered postoperatively until discharge. Children with a postoperative urinary tract infection (UTI) received full-dose antimicrobial treatment followed by prophylaxis until stent removal.

RESULTS

Median patient age at surgery was 11 months (1 month-17.5 years). Forty-nine stents were inserted on the left side, 32 on the right, and one bilaterally. Cultures showed bacterial colonization in 58 cases (70.7%); 15 (25.8%) grew Staphylococcus (coagulase negative and positive). Eight children had febrile UTI postoperatively; in four the stent was colonized by Enterococci and in one by Proteus; three were sterile. There was no statistically significant association between positive stent culture and febrile UTI, patient age or sex, or stent laterality. The study was potentially limited by its observational design, small sample size, and the selective antibiotic treatment of patients with UTI which may have affected stent bacterial resistance.

CONCLUSION

Bacterial colonization is not uncommon in double-J stents retained for several weeks after pyeloplasty, but is usually not clinically significant. Enterococcus is the most frequent pathogen.

Contemporary practice of percutaneous nephrolithotomy: review of practice in a single region of the UK

INTRODUCTION

Most series of percutaneous nephrolithotomy (PCNL) from single specialised centres represent optimum results achievable and may not reflect outcomes of everyday practice. We analysed the practice in our region.

PATIENTS AND METHODS

Medical records of 178 patients undergoing PCNL in 2002 in 12 participating hospital trusts were retrospectively analysed.

RESULTS

Even outside the tertiary referral centres, there was a 6-fold difference between trusts in the frequency of PCNL. In 28% of cases, another stone-removing modality had been tried first. Failed renal puncture was a major cause of abandoning surgery (9%). An indication of the difficulty in obtaining complete stone clearance is that only 107 (60%) operation notes recorded complete clearance, while 75 (42%) patients required a subsequent procedure (13% a secondary PCNL). Use of supra 12th rib punctures was small (6%) as was the rate of 'tube-less' PCNL (4%). Some 22% had simultaneous ureteric stent insertion. Approximately 8% of cases required a blood transfusion. Thirty-eight patients (23%) had a proven infection (UTI) pre-operatively (> 10(4) organisms; > 10 white blood cells) with almost all patients receiving antibiotics at anaesthesia induction. Postoperative sepsis rates (temperature > 38.5 degrees C) were similar in those with and without a pre-operative UTI (18.4% versus 14.3%) and pre-operative antibiotics appeared to have little extra protective effect. Severe sepsis was rare with no patient requiring intensive care admission for this reason. Median length of stay postoperatively was 5 days.

CONCLUSIONS

These results present important figures to quote when counselling patients pre-operatively, albeit that the degree of difficulty (and hence the likelihood of problems) is identifiable from stone and anatomical configurations. In addition, the present data are a more accurate reflection of urinary stone surgery in non-tertiary, general urological practice.

Antibiotic pretreatment of hydrogel ureteral stent

PURPOSE

To compare bacterial adhesion to hydrogel-coated and uncoated ureteral stents. The antimicrobial activity of coated and uncoated stents treated with commonly used antibiotic solutions also was evaluated.

MATERIALS AND METHODS

Hydrogel coated and uncoated stent segments were dipped in different antibiotic solutions (ciprofloxacin, gentamicin, and cefazolin). Normal saline was used as the control. The segments were incubated in separate broths of Escherichia coli and Enterococcus faecalis to reach the log phase. They were sonicated to free the bacteria, and colony-forming units were determined after 48 hours. To evaluate antibacterial activity, hydrogel-coated and uncoated stent segments were dipped in the above-mentioned antibiotic solutions. Normal saline was used as the control. Segments were incubated in separate Mueller-Hinton agar plates inoculated with E. coli or Enterococcus faecalis, and the zones of inhibition were determined at 24 hours. The duration of antibacterial activity for each bacterium-antibiotic combination also was studied.

RESULTS

Hydrogel coating did not significantly reduce bacterial adhesion. Zones of inhibition around stent pieces dipped in antibiotic solutions differed with the organism and the antibiotic. Cefazolin produced a significantly larger zone of inhibition with hydrogel-coated stent, but the duration of antibacterial activity was similar to that of uncoated stent. Hydrophilic coating significantly increased the duration of antibacterial activity of ciprofloxacin and gentamicin.

CONCLUSION

Hydrogel coating on the surface of ureteral stents does not prevent or reduce bacterial adhesion. However, after antibiotic treatment, stents exhibit antibacterial activity in the local environment at greater intensity and for a longer time, depending on the bacterium-antibiotic combination.

Retrograde intra-renal surgery for stone extraction

OBJECTIVE

To assess various clinical parameters affecting the efficacy and safety profile of retrograde intra-renal surgery (RIRS) for stone extraction.

MATERIAL AND METHODS

Between the years 2001 and 2003, 63 patients underwent RIRS in our department for renal calculi, including 25 who had stones >/=20mm in size.

RESULTS

Among the 63 patients who underwent the operation, 19 (30%) had infectious complications postoperatively. Although neither preoperative stenting nor stone burden were found to have any direct implication on postoperative course, a trend was seen as 64% of the infected patients had initially had large renal stones (>/=20mm in diameter) and 59% had been preoperatively drained.

CONCLUSIONS

RIRS is currently considered to be a safe standard retrograde endoscopic procedure for treating renal calculi. However, patients with stones>20 mm in diameter or multiple small calculi, especially in the presence of pre-existing tubes or following prior urinary tract infections, represent a subgroup of patients that are, in general, at higher risk of remarkable infectious complication rates and are likely to experience less satisfying stone-free rates when RIRS surgery is performed.

Retrograde intrarenal surgery as second-line therapy yields a lower success rate

BACKGROUND AND PURPOSE

Retrograde intrarenal surgery (RIRS) is a recent addition to the treatment options for renal calculi. Therefore, the indications, as well as the predictors of success, are still being studied. Herein, we report a retrospective comparison of RIRS performed as the primary treatment and as second-line therapy, mostly after shockwave lithotripsy (SWL) failure.

PATIENTS AND METHODS

Between October 2001 and August 2004, 93 patients underwent RIRS (11% of all ureteroscopies), all by the same surgeon. Patients were divided into two groups: group 1 (n = 42) consisted of patients undergoing RIRS as a first-line modality and group 2 (n = 51) of those having RIRS as secondline therapy. The indications for RIRS in group 1 were renal calculi with prior placement of a double-J stent (30%), renal + ureteral stone (25%), pushback of ureteral stone during ureteroscopy (22%), a radiolucent stone (8%), coagulopathy, and abnormal renal anatomy. In group 2, the patients were initially treated by SWL (92%) or percutaneous nephrolithotomy. The groups did not differ significantly in demographic characteristics, mean stone size (9.5 and 8.7 mm, respectively), or stone location (in both 60% in the lower pole). The variables analyzed were operating time, complications, length of hospitalization, and stone-free rate.

RESULTS

The overall stone-free rate was 73%. However, the stone-free rate was significantly higher in group 1 than in group 2: 80% v 67%, respectively. A higher complication rate and longer hospitalization were noted in group 2, although the difference was not statistically significant.

CONCLUSIONS

When RIRS is performed after failed SWL, it has a lower success rate and may be associated with a higher morbidity rate than if it is performed as first-line therapy. These results suggest that the success rate of RIRS may be influenced by the same negative factors that reduce SWL success. Therefore, if a patient fails SWL, careful consideration should be given to the best second-line therapy comparing RIRS with percutaneous stone removal.

Risk factors for lower urinary tract infection and bacterial stent colonization in patients with a double J ureteral stent

OBJECTIVE

We investigated the potential risk factors for lower urinary tract infection and bacterial stent colonization in patients with double-J stents.

PATIENTS AND METHODS

A total of 195 double-J stents from 190 patients (95 men and 95 women, mean age 40.22 years) were examined. In all patients, prophylactic antimicrobial therapy was administered at the time of stenting. The stents and urine samples were removed aseptically and the proximal and distal tip segments of the stents were obtained. Three culture specimens were obtained from each stent segment and urine sample. Chi-square tests, odds ratio, and relative risk were used for the statistical analysis.

RESULTS

Bacterial colonies were found in 24% (47 of 190) of the urine samples, 31% (61 of 195) of the proximal stent segments, and 34% (67 of 195) of the distal stent segments. Of the pathogens identified, Escherichia coli (34 of 47) was the most common. Diabetes mellitus (P < 0.01), chronic renal failure (P < 0.001), and pregnancy (P < 0.01) were found to be risk factors for lower urinary tract infection in patients with stents. An increased stent colonization rate was associated with implantation time, age, and female sex, but these were not statistically significant for lower urinary tract infection

CONCLUSION

Diabetes mellitus, chronic renal failure, and pregnancy are associated with a higher risk of lower urinary tract infection. Therefore, patients in these categories should be monitored carefully for infectious complications.

Colonization of internal ureteral stent and bacteriuria

To demonstrate the infection rates, colonization rates following the internal ureteral stent placement; the correlation of indwelling time with the infection, bacterial colonization and the value of urine culture to identify colonizing bacteria One hundred and forty-eight stents of 146 patients were evaluated for the bacteriuria and colonization after internal ureteral placement average 8.6 weeks according to the indication. All patients were ambulatory and were examined in an outpatient clinic. Urine culture and 1 cm of proximal and distal ends was taken for culture for bacterial evaluation. The rate of colonization is 33, 50 and 54% when indwelling time is less than 4 weeks, 4-6 weeks and more than 6 weeks, respectively. Urine culture can detect colonization in 69%. Colonization was not found if the indwelling time was less than 2 weeks. Escherichia coli, Enterobacter and Pseudomonas spp. were the most common colonized organisms. Colonization is common if the indwelling time is more than 2 weeks, urine culture can detect colonization in about two to three of the patients. Even if the culture is negative, prophylactic antibiotic that cover gram-negative and gram-positive organisms should be administrated when the patients require further procedures.

Febrile Complications Following Insertion of 100 Double-J Ureteral Stents

BACKGROUND AND PURPOSE

Implanted foreign bodies are associated with a higher risk of infection. Little has been published on infectious complications associated with ureteral double-J stents. The aim of this study was to define risk factors and characterize the febrile complications of the insertion of double-J stents.

PATIENTS AND METHODS

One hundred consecutive cases of retrograde stent insertion (55 men and 45 women) were evaluated retrospectively. Eighty-one patients had an obstructing stone, either in the ureter or at the ureteropelvic junction; 10 had an obstructing tumor; and 9 had hydronephrosis and pain without calculi. Risk assessment was calculated for two major categories: urgent (N = 47) and elective (N = 53) insertion. Potentially confounding factors such as age, sex, accompanying medical problems, and types of prophylaxis were assessed. All but six patients received prophylactic antibiotics prior to stent insertion.

RESULTS

All thirteen patients who had fever at the initial evaluation underwent urgent stent insertion. Of the 87 afebrile patients (53 elective and 34 urgent insertions), 22 (25%) developed fever (> or = 38 degrees C) after the procedure. Fever developed in 19 (56%) of the 34 urgent-insertion group who were not originally febrile as opposed to 3 (6%) of the elective-insertion group (P < 0.001). Six of these 22 patients (27%) had a positive urine culture after insertion. None had a positive blood culture, including the 13 patients who underwent the procedure while febrile.

CONCLUSIONS

Urgent insertion of a double-J stent is associated with a high risk of fever but a favorable outcome.

Bacteriology of urinary tract infection associated with indwelling J ureteral stents

PURPOSE

To investigate the microorganisms responsible for urinary tract infection (UTI) and stent colonization in patients with indwelling J ureteral stents and to compare the antimicrobial susceptibility pattern of the isolates from urine and J stents in order to establish the etiologic agents of bacteriuria and colonized stents in such patients and provide baseline data on an antibiotic policy for the urology unit.

PATIENTS AND METHODS

Midstream urine from 250 patients requiring J stent insertion was investigated microbiologically prior to stent insertion and on the day of stent removal. After stent removal, 3 to 5 cm of the tip located in the bladder was also sent for culture. Patients' bio-data and underlying diseases were documented. Those with no known systemic diseases ("normal patients") were also studied as controls. Of the 250 patients studied, 152 (61%) were normal, while 27 (11%), 53 (21%), and 18 (7%) had diabetes mellitus (DM), chronic renal failure (CRF), and diabetic nephropathy (DN), respectively. The mean duration of stent retention was 27 days. All microbial isolates were tested for their susceptibility to a panel of 10 antibiotics.

RESULTS

Twelve patients (5%) before stent insertion and 42 patients (17%; P < 0.001) on the day of stent removal had positive urine cultures. One hundred four stents (42%) were culture positive. Of the 104 patients with positive stent cultures, in 62 patients (60%), urine culture was sterile. The commonest isolates were Escherichia coli, Enterococcus spp., Staphylococcus spp., Pseudomonas, and Candida spp. On the day of stent removal, urine culture was positive in 28% of the normal patients compared with 57% (P = 0.11), 78% (P < 0.001), and 62% (P < 0.001) of patients with CRF, DM, and DN, respectively. Stent isolates were more resistant to antibiotics than the organism isolated before stent insertion.

CONCLUSION

An indwelling J ureteral stent carries a significant risk of bacteriuria and stent colonization. The sensitivity of urine culture to stent colonization is low, and therefore, a negative culture does not rule out a colonized stent. Bacteria cultured from urine after stent insertion and from the stents are more resistant to antibiotics than are those cultured from urine before stent insertion. Norfloxacin or ciprofloxacin is recommended as prophylaxis prior to stent insertion, and an aminoglycoside can be added to treat symptomatic patients with severe infections.

Ancillary instrumentation for ureteroscopy

As the quality of ureteroscopy continues to improve, ancillary instrumentation will advance. The endourologist now has a vast supply of specially designed guidewires, stents, balloons, and baskets. These technologies have expanded the realm of cases that may be managed endoscopically. As the urologist becomes more familiar with the options at his or her disposal, patient care will improve.

Swarming ofProteus mirabilisover Ureteral Stents: A Comparative Assessment

BACKGROUND AND PURPOSE

Encrustation on indwelling ureteral stents is commonly related to the presence of urease-producing bacteria that elevate the pH of the urine through the hydrolysis of urea, resulting in the precipitation of calcium and magnesium salts. Using a model previously shown to measure accurately the ability of Proteus mirabilis to swarm over catheter surfaces (Eur J Clin Microbiol Infect Dis 1999;18:206), we investigated the ability of this organism to swarm over three ureteral stents with potential encrustation-resistance properties.

MATERIALS AND METHODS

Three commercially available ureteral stents were selected for evaluation: a low surface-energy stent, a hydrogel-coated stent, and a silicone stent. Ten-microliter aliquots of a 4-hour culture of P. mirabilis 296 in Trypticase soya (TSA) broth was inoculated 5 mm from a 1-cm channel cut out from TSA plates. Ten-millimeter stent sections were placed as bridges across the central channel adjacent to the inocula. Time to pathogen crossing was measured.

RESULTS

The mean time (+/- SD) to pathogen migration across the three test materials was 15.9 +/- 6.1, 19.8 +/- 9.5, and 29.7 +/- 14.3 hours for the low surface-energy, hydrogel-coated, and silicone stents, respectively. Statistical analysis revealed significant differences between the crossing times of the low surface-energy (P = 0.001) and hydrogel-coated (P = 0.034) stents compared with silicone but not between the low surface-energy and hydrogel-coated stents (P = 0.387).

CONCLUSION

Migration of P. mirabilis 296 across silicone stents was significantly reduced compared with low surface-energy and hydrogel-coated stents. These findings suggest that P. mirabilis may have a lower affinity for silicone stents, which may translate into a reduced risk of infection with P. mirabilis and associated stent encrustation.

Strategies for the control of catheter encrustation

Two general strategies have been adopted to develop catheter materials that resist encrustaion by bacterial biofilms: (a) the incorporation of antimicrobial agents into the polymers and (b) the production of materials with surface properties which prevent the adherence of bacterial cells. Our experience to develop non-adherent surfaces which abstracts design from nature is reported. Compounds based on 2-methacryloloxyethylphosphorylcholine co-polymerised with long-chain alkyl methacrylates have been produced which have structural and surface properties similar to those of the outer membranes of erythrocytes. These PC-coatings have been applied onto catheter base materials where they produce polar surfaces that are extremely hydrophilic. In experiments using a laboratory model of the catheterised bladder we found that the PC-coatings did not reduce colonisation of latex or silicone catheters by crystalline Proteus mirabilis biofilm. There were no significant difference between the amounts of calcium and magnesium salts deposited on coated and non-coated catheters. In a further set of experiments the PC-coatings did not significantly increase the mean times for which catheters drained freely. In a parallel clinical study, the performance of PC-coated ureteral stents was investigated. Scanning electron microscopy and bacteriological analysis on 44 PC-coated stents that had been implanted in patients for 12-week periods and 28 control stents suggested that the PC-coated devices were less vulnerable to encrustation and colonisation by bacterial biofilm than normal stents. It was of interest that in contrast to encrusted catheters, urease producing species such as P. mirabilis were rarely isolated from the stents. The main organisms colonising the stents were enterococci and coagulase-negative staphylococci. These results suggest that the mechanisms of catheter and stent encrustation may be different and require different strategies for control.

Improving biomaterial properties of collagen films by chemical modification

Films of bovine collagen were chemically modified with the goal of improving their biomaterial properties. The modified films were investigated with respect to their affinity to fibroblast and endothelial cells, as well as their antibacterial properties tested by adhesion of Staphylococcus aureus. Modifications that only change the net charge of collagen, such as acetylation, succinylation, and treatment with glutaraldehyde (all increase the negative charge), and amination with ethylenediamine (EDA), N,N-dimethyl-EDA (DMEDA), or butylamine (all increase the positive charge), did not dramatically alter the mammalian cell attachment to the film. In contrast, derivatization of collagen using methoxypoly(ethylene glycol) (PEG) diminished the attachment of fibroblasts by 98 +/- 1% and of endothelial cells by more than 99% compared to unmodified collagen. Moreover, the rate of growth of fibroblasts dropped by 97 +/- 1% and that of endothelial cells by 88 +/- 3% as a result of PEGylation of collagen. Adhesion of S. aureus cells also plummeted by 93 +/- 2% as a result of this PEGylation. With these antifouling properties, PEG-collagen may be a promising coating material for coronary stents. Subsequent derivatization of PEG-collagen with EDA or DMEDA abolished its mammalian cell-repelling ability, whereas bacterial cell repulsion was partially retained: for example, DMEDA-modified PEG-collagen exhibits up to a 5-fold lower bacterial adhesion than collagen. It is worth noting that a material that allows mammalian cell attachment but reduces bacterial adhesion could be useful as an implant or coating.

Catheter-associated urinary tract infections

In the past few years it has been clearly demonstrated that the concept of bacterial biofilm production permits an understanding and provides some explanation of the pathogenesis, diagnosis and treatment of catheter-associated urinary tract infections. This concept describes the colonization of catheter surfaces and the movement of bacteria against the urinary flow. It explains the antibacterial resistance of these matrix-enclosed sessile populations of bacteria. The catheter encrustation can be observed as mineralizing bacterial biofilm. The differentiation in swarming cells exposing a much higher activity of the enzyme urease is responsible for the predominant role of Proteus mirabilis in obstructing encrustations. The guidelines for the prevention of catheter-associated urinary tract infections were developed over the past decades by clinicians and are still valid. They can now be better understood taking into consideration these new theories. As overuse of urethral catheters and non-compliance of their recommended use are still apparent, educational and surveillance programmes are needed to help maintain good standards of care.