Irreversible Renal Function Impairment Due to Silent Ureteral Stones

A novel in vivo model of ureteral fibrosis induced by calcium oxalate beads in C57BL/6J mice

The global incidence of ureteroliths in humans is increasing, particularly posing a problem in developed countries. The most common stone type is calcium oxalate, which is associated with a high recurrence rate. In veterinary medicine, stones are the most common cause of ureteral obstruction in cats, accounting for 72-87% of cases. In cats, stones cause irreversible ureteral damage, necessitating stone treatment as well as ureteral therapy. However, the mechanisms underlying the ureteral damage caused by stones remain unclear. Therefore, this study aimed to create a mouse model suitable for studying the ureteral fibrosis caused by oxalate stones by artificially embedding calcium oxalate in the ureter. Pathological tissue analysis was used to compare normal ureters without ligation and ureters with sham or oxalate bead implantation. The ureters of the sham and oxalate bead groups showed granulation tissue formation, transitional epithelium exfoliation, and densely packed connective tissue in the proprietary and muscle layer regions. Particularly in the oxalate bead group, infiltration of degenerated neutrophils, presence of foreign body giant cells, and hyperplasia of the transitional epithelium were observed. The proportion of fibrosis was higher in the oxalate group than in the sham group. Overall, this mouse model created using oxalate bead implantation has the potential to efficiently induce ureteral obstruction. This mouse model is expected to be used for elucidating the molecular mechanisms of ureteral fibrosis and evaluating therapeutic drugs in future.

A prospective evaluation of patient-reported outcomes during follow-up of ureteral stones managed with medical expulsive treatment (MET)

Patient-reported outcomes (PROs) for ureteral stones predominantly assess the pain. Despite the lack of evidence, multiple trials studying the efficacy of medical expulsive therapy (MET) have used PROs to define spontaneous stone passage (SSP). We aim to objectively evaluate the accuracy of PROs to predict successful SSP and the probability of patient's symptom resolution after stone passage. A single-center, prospective observational study recruiting adults with isolated, uncomplicated, ≤ 10 mm ureteral calculus was conducted. All patients received 4 weeks of MET, and SSP was confirmed by low-dose non-contrast-enhanced computed tomography (NCCT). The accuracy of PROs: "pain cessation," "decreased pain," "stone seen," and "stone capture" to predict successful SSP were evaluated in 1 month. The patient's symptom resolution rate was assessed at 1 and 4-month follow-ups. A total of 171 patients were included, and the overall SSP rate was 66.4% (n = 99). Patient-reported pain cessation, stone visualization, and stone capture were associated with successful SSP, but their accuracy was 59, 53, and 43%, respectively. Moreover, 25% of patients reporting complete pain cessation still harbored ureteral calculus. Pain resolved in 91% of patients after SSP at a 4-month follow-up. While hematuria and nausea resolved in all patients, lower urinary tract symptoms (LUTS) were not resolved in 17% of patients. We concluded that patient-reported pain cessation, stone visualization, and stone capture predict successful SSP, but confirmatory imaging is required due to the poor accuracy of these measures. The significant rates of non-pain-related symptoms indicate their significant contribution to patient morbidity. Clinical Trial Registration: Registered in Clinical Trial Registry of India (CTRI), Registration number: CTRI/2020/10/028777 (29th October 2020).

A comparison between asymptomatic and symptomatic ureteral stones

To investigate the characteristics and impact of asymptomatic (silent) ureteral stones on renal function and compare them with those of symptomatic stones. We retrospectively reviewed the medical records of 677 patients who underwent ureteroscopic lithotripsy or laparoscopic ureterolithotomy for ureteral stones between 2016 and 2020. Patients were divided into two groups according to the presence of recognizable symptoms. We investigated the characteristics and impact of silent stones on post-treatment renal function recovery and compared them with those of symptomatic stones. Among the 677 patients, 43 (6.4%) had asymptomatic ureteral stones, and 634 (93.6%) had symptomatic ureteral stones. Compared to symptomatic stones, asymptomatic stones were larger (11.4 mm vs. 9.6 mm, p = 0.003), more commonly present in the upper ureter (62.7% vs. 48.0%, p = 0.04), and more commonly associated with high-grade hydronephrosis (32.8% vs. 12.3%, p < 0.001); however, no difference in metabolite composition was observed between the two group of stone. In the asymptomatic stone group, the mean preoperative estimated glomerular filtration rate (eGFR) was 77.37 ± 23.54 mL/min/1.73 m², and the mean postoperative eGFR indicated no significant improvement at 1 day, 7 days, 3 months, and 12 months (76.66 ± 21.45, 77.89 ± 20.87, 77.29 ± 22.22, and 76.71 ± 24.21 mL/min/1.73 m², respectively; p = 0.567, p = 0.613, p = 0.924, and p = 0.202, respectively). In the symptomatic stone group, the mean preoperative eGFR was 78.17 ± 28.25 mL/min/1.73 m²; the mean postoperative eGFRs at 1 day, 7 days, 3 months, and 12 months were 81.24 ± 26.38, 86.16 ± 25.61, 89.11 ± 25.43, and 89.50 ± 26.01 mL/min/1.73 m², respectively and demonstrated significant improvement (p = 0.002, p < 0.001, p < 0.001, and p < 0.001, respectively). Silent stones irreversibly impaired renal function, even after proper management. Therefore, active treatment strategies are required for all patients who are hesitant to receive treatment for silent stones because of their asymptomatic status to prevent permanent renal impairment.

Ureteral Obstruction Promotes Ureteral Inflammation and Fibrosis

BACKGROUND

Hydronephrosis and renal impairment may persist even after relieving an obstruction, particularly in cases of chronic obstruction. Obstruction can cause fibrotic changes of the ureter, potentially contributing to long-term kidney damage.

OBJECTIVE

To characterise pathophysiological changes of obstructed ureters with focus on inflammatory responses triggering fibrosis and potential impairment of ureteral function.

DESIGN, SETTING, AND PARTICIPANTS

Eighty-eight mice were randomly assigned to unilateral ureteral obstruction (UUO) for 2 d, UUO for 7 d, and UUO for 7 d followed by 8 d of recovery, or a control group (no prior surgical intervention).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Peristaltic rate was determined over 2 min by direct visualisation with a microscope, while hydronephrosis was assessed by ultrasound. Obstructed and contralateral ureters were harvested, and underwent histopathological evaluation. We quantified 44 cytokines/chemokines, and five matrix metalloproteases using Luminex technology. Cell composition was characterised via immunofluorescence. Statistical significance was assessed using Welch analysis of variance, Kruskal-Wallis test, and Dunnett's T3 multiple comparison test.

RESULTS AND LIMITATIONS

Obstruction resulted in hydronephrosis and significantly impaired peristalsis. Marked fibrosis was observed in lamina propria, muscle layer, and adventitia. Connective tissue in obstructed ureters showed hyperaemia and leucocyte infiltration. Unsupervised hierarchical clustering demonstrated different cytokine/chemokine patterns between groups. Ureters obstructed for 7 d followed by recovery were notably different from other groups. Inflammatory cytokines, chemoattractants, and matrix metalloproteases increased significantly in obstructed ureters. Contralateral unobstructed ureters showed significantly increased levels of chemokines and matrix metalloproteases. Immunofluorescence confirmed activation of T cells, Th1 and Th2 cells, and M1 macrophages in obstructed and contralateral ureters, and a shift to M2 macrophages following prolonged obstruction.

CONCLUSIONS

Ureteral obstruction triggers severe inflammation and fibrosis, which may irreversibly impair ureteral functionality. Function of the unobstructed contralateral ureter may be regulated by a systemic immune response as a result of the obstruction.

PATIENT SUMMARY

Here, we studied in more detail the way the ureter responds to being blocked. We conclude that a strong immune response is activated by the blockage, leading to changes in the structure of the ureter possibly impacting function, which may not be reversible. This immune response also spreads to the opposite ureter, possibly allowing it to change its function to compensate for the reduced functionality of the blocked ureter.

The Long-Term Follow-Up of Patients with Cystine Stones: A Single-Center Experience for 13 Years

Introduction: Cystine stone development is relatively uncommon among patients with urolithiasis, and most studies have reported only on small sample sizes and short follow-up periods. We evaluated clinical courses and treatment outcomes of patients with cystine stones with long-term follow-up at our center. Methods: We retrospectively analyzed 22 patients diagnosed with cystine stones between January 1989 and May 2019. Results: The median follow-up was 160 (range 6–340) months, and the median patient age at diagnosis was 46 (range 12–82) years. All patients underwent surgical interventions at the first visit (4 extracorporeal shockwave lithotripsy, 5 ureteroscopy, and 13 percutaneous nephrolithotripsy). The median number of stone events and surgical interventions per year was 0.45 (range 0–2.6) and 0.19 (range 0–1.3) after initial surgical intervention. The median time to stone events and surgical intervention was 2 years and 3.25 years, respectively. There was a significant difference in time to stone events and second surgical intervention when patients were divided at 50 years of age at diagnosis (p = 0.02, 0.04, respectively). Conclusions: Only age at a diagnosis under 50 was significantly associated with recurrent stone events and intervention. Adequate follow-up and treatment are needed to manage patients with cystine stones safely.

Effect of Endoscopic Ureteral Stone Treatment on Kidney Function

INTRODUCTION

Ureteral stones may have an influence on kidney functions due to postrenal obstruction or urinary infections. Urgent decompression or stone removal is necessary and recommended to prevent further complications in case of severe conditions such as anuria and urosepsis. Although it is believed that ureteral stone removal would result in renal function improvement, there are still unclear points on whether ureteroscopy (URS) can provide benefit as expected and has some adverse effects. In this study, we aimed to evaluate the alteration of kidney functions of patients who undergo rigid or flexible URS for ureteral stones and find if there are any influencing factors on kidney function alteration.

MATERIALS AND METHOD

We analyzed 126 patients who underwent retrograde intrarenal surgery (RIRS) for renal stones between May 2018 and February 2020 prospectively. The estimated glomerular filtration rate (eGFR) was calculated on the day before the surgery, by modification of diet in renal disease (MDRD) formula. The calculation was repeated and saved three times during follow-up for the same patient; on the day after the operation, on the postoperative 30th day, and the postoperative 90th day. Then, we evaluated the renal function by comparing eGFR and assessed the predicting factors affecting the kidney function.

RESULTS

Preoperative mean eGFR was 82.28 ± 25.20 mL/min/1.73 m2 for the study group. Mean eGFR was calculated 90.92 ± 22.97 mL/min/1.73 m2 on the first postoperative day, and 94.54 ± 21.95 mL/min/1.73 m2 on the third-month follow-up. The mean change in eGFR was 8.63 ± 16.68 mL/min/1.73 m2 in the early period and 12.26 ± 21.09 mL/min/1.73 m2 in the long-term follow-up period. Fifty-one patients improved on chronic kidney disease (CKD) stage, and 13 deteriorated in three months follow-up.

CONCLUSION

Removing the stone and relieving the obstruction by ureteroscopic treatment have an alteration on eGFR. Although eGFR improves in the short-term follow-up, amelioration is evident in long-term follow-up, especially in female patients. The other predictive factors for eGFR improvement after URS are the presence of ureteral obstruction and high preoperative serum creatinine levels.

Implementation of a Ureteric Colic Telemedicine Service: A Mixed Methods Quality Improvement Study

OBJECTIVE

To assess the effectiveness of a telemedicine service for ureteric colic patients in reducing the number of unnecessary face-to-face consultations and shortening waiting time for appointments.

METHODS

A telemedicine workflow was implemented as a quality improvement study using the Plan-Do-Study-Act method. All patients presenting with ureteric colic without high-risk features of fever, severe pain, and hydronephrosis, were recruited, and face-to-face appointments to review scan results were replaced with phone consultations. Data were prospectively collected over 3 years (January 2017 to December 2019). Patient outcomes including the reduction in face-to-face review visits, time to review, reattendance and intervention rates, were tracked in an interrupted time-series analysis, and qualitative feedback was obtained from patients and clinicians.

RESULTS

Around 53.2% of patients presenting with ureteric colic were recruited into the telemedicine workflow. A total of 465 patients (46.2%) had normal scan results and 250 patients (24.9%) did not attend their scan appointments, hence reducing the number of face-to-face consultations by 71.1%. A total of 230 patients (22.9%) required subsequent follow-up with urology, while 61 patients (6.1%) were referred to other specialties. Mean (SD) time to review was 30.0 (6.2) days, 6-month intervention rate was 3.4% (n = 34) and unplanned reattendance rate was 3.2% (n = 32). Around 93.1% of patients reported satisfaction with the service.

CONCLUSION

The ureteric colic telemedicine service successfully and sustainably reduced the number of face-to-face consultations and time to review without compromising on patient safety. The availability of this telemedicine service has become even more important in helping us provide care to patients with ureteric colic in the current COVID-19 pandemic.

Changes in separate renal function in patients who underwent minimally invasive renal stone surgery according to the preoperative functional deterioration

The significant predictors for the postoperative deterioration of separate renal function after minimally invasive stone surgery were investigated in the present prospective and observational study. A total of 117 consecutive patients who underwent retrograde intrarenal surgery or mini-percutaneous nephrolithotomy for renal calculi >10 mm were included in the present study. Perioperative changes in separate renal function were evaluated with Technetium-99m-Diethylene TriaminePenta acetic acid scan prior to intervention and at postoperative 3 months. Based on the functional differences between bilateral renal units, deterioration of separate renal function was graded into the following three groups: normal deterioration (<10%), moderate deterioration (10–20%), and severe deterioration (>20%). A total of 46 patients had a normal separate renal function, while 71 (60.7%) showed abnormal separate function in the involved side, including 29 (24.8%) moderate and 42 (35.9%) severe deterioration. Postoperatively, 48 patients (41.0%) showed aggravation or no recovery of separate renal function. Of the 46 patients with normal separate function, only 9 patients (19.5%) showed postoperative aggravation. Patients with moderate and severe deterioration showed aggravation (n = 7, 24.1%) or no recovery of separate renal function (n = 32, 76.1%, P < 0.001). Preoperative severe deterioration of separate renal function was an independent significant predictor for the postoperative deterioration of renal function (OR: 9.09, 95% CI: 4.007–20.624, P < 0.001). Lower preoperative deterioration of separate renal function showed a high probability of functional recovery. Therefore, it is hypothesized that early intervention might be necessary in cases where the patient exhibits severe aggravation of renal function.

Clinical factors associated with postoperative hydronephrosis after ureteroscopic lithotripsy

Purpose

This study aimed to determine the predictors of ipsilateral hydronephrosis after ureteroscopic lithotripsy for ureteral calculi.

Materials and Methods

From January 2010 to December 2014, a total of 204 patients with ureteral calculi who underwent ureteroscopic lithotripsy were reviewed. Patients with lack of clinical data, presence of ureteral rupture, and who underwent simultaneous percutaneous nephrolithotomy (PNL) were excluded. Postoperative hydronephrosis was determined via computed tomographic scan or renal ultrasonography, at 6 months after ureteroscopic lithotripsy. Multivariable analysis was performed to determine clinical factors associated with ipsilateral hydronephrosis.

Results

A total of 137 patients were enrolled in this study. The mean age of the patients was 58.8±14.2 years and the mean stone size was 10.0±4.6 mm. The stone-free rate was 85.4%. Overall, 44 of the 137 patients (32.1%) had postoperative hydronephrosis. Significant differences between the hydronephrosis and nonhydronephrosis groups were noted in terms of stone location, preoperative hydronephrosis, impacted stone, operation time, and ureteral stent duration (all, p<0.05). On multivariable analysis, increasing preoperative diameter of the hydronephrotic kidney (adjusted odds ratio [OR], 1.21; 95% confidence interval [CI], 1.12–1.31; p=0.001) and impacted stone (adjusted OR, 3.01; 95% CI, 1.15–7.61; p=0.031) independently predicted the occurrence of postoperative hydronpehrosis.

Conclusions

Large preoperative diameter of the hydronephrotic kidney and presence of impacted stones were associated with hydronephrosis after ureteroscopic stone removal. Therefore, patients with these predictive factors undergo more intensive imaging follow-up in order to prevent renal deterioration due to postoperative hydronephrosis.