Drainage of infected kidneys with ureteral stents: does size matter?

PURPOSE: The purpose of our study was to evaluate the ability of ureteral stents with different diameters to drain pus that accumulates in an obstructed kidney using an in vitro model. METHODS: We developed an in vitro model of an obstructed kidney filled with pus. The model included a silicon kidney unit based on computed tomography (CT) data, a 3D printed ureteral stone based on a real extracted ureteral stone, a latex ureter model, a bladder vessel, and a fluid with qualities resembling pus. Identical printed stones were inserted into four ureter models containing stents with varying diameters (4.8F, 6F, 7F, 8F), each of which was connected to the kidney unit and the bladder vessel. The kidney unit was filled with artificial pus to pressures of 30 cmH2O to simulate an infected and obstructed kidney. The obstruction was relieved with stents in place, while artificial urine was pumped into the kidney; pressure in the kidney and remaining pus were measured continuously. RESULTS: The rate of pressure drop and the final pressure measured in the kidney were unaffected by the diameter of the stent. For all stent diameters, the pressure reached non-obstructed levels within 30 s, final pressure was reached within 90-120 s, and minimal amounts of pus remained in the kidney after 120 min. CONCLUSIONS: In vitro experiments demonstrate that all stent diameters drain pus-filled, obstructed kidneys with the same efficacy. The common perception that larger diameter tubes are more effective under such circumstances should be re-examined.

Magnetic resonance imaging of in vitro urine flow in single and tandem stented ureters subject to extrinsic ureteral obstruction.

OBJECTIVE: To quantify the relative volumetric flows in stent and ureter lumina, as a function of stent size and configuration, in both unobstructed and externally obstructed stented ureters. METHODS: Magnetic resonance imaging was used to measure flow in stented ureters using a phantom kidney model. Volumetric flow in the stent and ureter lumina were determined along the stented ureters, for each of four single stent sizes (4.8F, 6F, 7F, and 8F), and for tandem (6F and 7F) configurations. Measurements were made in the presence of a fully encircling extrinsic ureteral obstruction as well as in benchmark cases with no extrinsic ureteral obstruction. RESULTS: Under no obstruction, the relative contribution of urine flow in single stents is 1-10%, while the relative contributions to flow are ~6 and ~28% for tandem 6F and 7F, respectively. In the presence of an extrinsic ureteral obstruction and single stents, all urine passes within the stent lumen near the extrinsic ureteral obstruction. For tandem 6F and 7F stents under extrinsic ureteral obstruction, relative volumetric flows in the two stent lumina are ~73% and ~81%, respectively, with the remainder passing through the ureter lumen. CONCLUSIONS: Magnetic resonance imaging demonstrates that with no extrinsic ureteral obstruction, minimal urine flow occurs within a stent. Stent lumen flow is significant in the presence of extrinsic ureteral obstruction, in the vicinity of the extrinsic ureteral obstruction. For tandem stents subjected to extrinsic ureteral obstruction, urine flow also occurs in the ureter lumen between the stents, which can reduce the likelihood of kidney failure even in the case of both stent lumina being occluded.

Comparative study of renal drainage with different ureteral stents subject to extrinsic ureteral obstruction using an in vitro ureter-stent model.

BACKGROUND: To compare the efficacy of different ureteral stents subject to extrinsic ureteral obstruction (EUO), in a controlled in vitro stented ureter experiment. METHODS: We employ an in vitro ureter-stent experimental set-up, with latex tubing simulating flexible ureters attached to vessels simulating renal units and bladders. The flow behavior of five ureteral stents-polymeric 8F, tandem 6F, tandem 7F, endopyelotomy and metal-was tested under a ureteral deformation configuration of 40°, with 2000 g external force over a 3.5 cm length of the ureter. A constant fluid flow was applied through the ureter-stent configurations, and pressure fluctuations in the renal unit were monitored. We considered a renal unit pressure of 10 cmH2O or flow discontinuation in the bladder as stent failure. Urine containing debris was mimicked by use of a colloidal solution. RESULTS: Of all assessed ureteral stents, under EUO conditions, only the single 8F stents remained patent throughout the length of the experiment. All other stents-tandem 6F and 7F, single 7F, metal and endopyelotomy-displayed limitations. CONCLUSIONS: Tandem and metal stents show no superiority over large luminal polymeric stents for EUO treatment in this in vitro model. Larger luminal stents offer excellent resistance to external pressure and allow adequate colloidal flow. The need for frequent exchange and bladder irritation should also be considered in the choice of stent configuration for treatment of kidney drainage under EUO.

Do organic substances act as a degradable binding matrix in calcium oxalate kidney stones?

BACKGROUND: Calcium oxalate (CaOx) stones are considered to be highly resistant to chemolysis. While significant organic matter has been identified within these stones, which is presumed to bind (inorganic) CaOx particles and aggregates, most chemolysis efforts have focused on methods to attack the CaOx components of a stone. We examine the feasibility of inducing chemolysis of CaOx kidney stones, within hours, by specifically attacking the organic matrix present in these stones. METHODS: In contrast to previous studies, we focused on the possible "brick and mortar" stone configuration. We systematically tested, via in vitro experiments, the ability of an extensive range of 26 potential chemolysis agents to induce relatively fast disintegration (and/or dissolution) of a large set of natural CaOx stone fragments, extracted during endourological procedures, without regard to immediate clinical application. Each stone fragment was monitored for reduction in weight and other changes over 72 h. RESULTS: We find that agents known to attack organic material have little, if any, effect on stone chemolysis. Similarly, protein and enzymatic agents, and oral additive medical treatments, have little immediate effect. CONCLUSIONS: These findings suggest that the organic and inorganic constituents present in CaOx stones are not structured as "brick and mortar" configurations in terms of inorganic and organic components.

Do patients with ureterolithiasis treated conservatively return to follow up?

INTRODUCTION Distal ureteral stones (DUS) are common in patients presenting to the emergency department (ED) with renal colic. The majority of DUS will pass spontaneously and therefore conservative care is common. Follow up is imperative as some of these stones might not pass and potentially lead to complications. The aim of our study was to evaluate the rate of compliance with follow up and to find predictive variables for it. MATERIALS AND METHODS: We retrospectively surveyed the medical records of all patients who had a non-contrast computed tomography (NCCT) at our ED between 01/03/16 and 31/5/17. We included patients with a DUS smaller than 10 mm that were treated conservatively. We obtained demographic, clinical, laboratory and imaging data. Compliance to follow up was evaluated by surveying the medical records and by calling the patients. We then compared the characteristics of patients who returned for follow up to those who did not. RESULTS: A total of 230 consecutive patients were included in our cohort: 194 (84%) patients were male and the average age was 46 y (21-82); 138 patients (60%) returned for a follow up visit while 92 patients (40%) did not. Univariate analysis revealed stone size and admission to hospital to be predictive of compliance to follow up while multivariate analysis revealed only hospital admission to be predictive of compliance. CONCLUSIONS: Only 60% of the patients with DUS treated conservatively return for a follow up visit. Hospital admission, which likely reflects appropriate patients counseling by a urologist and adequate follow up scheduling, was found to be associated with increased compliance with follow up.

Surgical Outcomes in High-risk Prostate Cancer and Salvage Radical Prostatectomy.

BACKGROUND: Patients with high-risk prostate cancer are at higher risk of treatment failure, development of metastatic disease, and mortality. There is no consensus on the treatment of choice for these patients, and either radical prostatectomy (RP) or external beam radiation therapy (EBRT) is recommended. Surgery is less common as the initial treatment for high-risk patients, possibly reflecting the concerns regarding morbidity as well as oncological and functional outcomes. Another high-risk group includes patients with failure of previous EBRT or focal treatment. For these patients, salvage radical prostatectomy (SRP) can be offered. OBJECTIVES: To describe our experience with surgery of high-risk patients and SRP. METHODS: This cohort included all high-risk patients undergoing RP or SRP at our institution between January 2012 and December 2019. We reviewed the electronic medical charts and collected pathological, functional, and oncological outcomes. RESULTS: Our cohort included 39 patients; average age was 67.8 years, and average follow-up duration was 40.9 months. The most common postoperative morbidity was transfusion of packed cells. There were no life-threatening events or postoperative mortality. Continence was preserved (zero to one pad) in 76% of the patients. Twenty-three patients (59%) had undetectable prostate specific antigen levels following the surgery, 11 (30%) were treated with either adjuvant or salvage EBRT, and 12 patients (31%) were found with no evidence of disease and no additional treatment was needed. CONCLUSIONS: Radical prostatectomy and SRP are safe options for patients presenting with high-risk prostate cancer, with good functional and oncological outcomes.

Radical Cystectomy after Previous Radiation or Pelvic Surgery: Is It Associated with Increased Morbidity?

BACKGROUND: Radical cystectomy is a complicated surgery with significant risks. Complications of Clavien-Dindo grade 3-4 range from 25% to 40% while risk of mortality is 2%. Pelvic surgery or radiotherapy prior to radical cystectomy increases the challenges of this surgery. OBJECTIVES: To assess whether radical cystectomy performed in patients with prior history of pelvic surgery or radiation was associated with increased frequency of Clavien-Dindo grade 3 or higher complications compared to patients without prior pelvic intervention. METHODS: We retrospectively evaluated all patients who underwent radical cystectomy at our center over a 7-year period. All patients with pelvic radiation or surgery prior to radical cystectomy comprised group 1, while group 2 included the remaining patients. RESULTS: In our study, 65 patients required radical cystectomy at our institution during the study period. Group 1 was comprised of 17 patients and group 2 included 48 patients. Four patients from group 2 received orthotopic neobladder, while an ileal conduit procedure was performed in the remaining patients. Estimated blood loss and the amount of blood transfusions given was the only variable found to be statistically different between the two groups. One patient from group 1 had four pelvic interventions prior to surgery, and her cystectomy was aborted. CONCLUSIONS: Radical cystectomy may be safely performed in patients with a history of pelvic radiotherapy or surgery, with complication rates similar to those of non-irradiated or operated pelvises.

Contemporary Series of Robotic-Assisted Distal Ureteral Reconstruction Utilizing Side Docking Position.

PURPOSE: The robot-assisted approach to distal ureteral reconstruction is increasingly utilized. Traditionally, the robot is docked between the legs in lithotomy position resulting in limited bladder access for stent placement. We examined the use of side docking of the daVinci robot® to perform distal ureteral reconstruction. MATERIALS AND METHODS: A retrospective review of distal ureteral reconstruction (ureteral reimplantation and uretero-ureterostomy) executed robotically was performed at a single institution by a single surgeon. The daVinci robotic® Si surgical platform was positioned at the right side of the patient facing towards the head of the patient, i.e. side docking. RESULTS: A total of 14 cases were identified from 2011-2013. Nine patients underwent ureteral reimplantation for ureteral injury, two for vesicoureteral reflux, one for ureteral stricture, and one for megaureter. One patient had an uretero-ureterostomy for a distal stricture. Three patients required a Boari flap due to extensive ureteral injury. Mean operative time was 286 minutes (189-364), mean estimated blood loss was 40cc (10-200), and mean length of stay was 2.3 days (1-4). Follow-up renal ultrasound was available for review in 10/14 patients and revealed no long-term complications in any patient. Mean follow-up was 20.7 months (0.1-59.3). CONCLUSION: Robot-assisted laparoscopic distal ureteral reconstruction is safe and effective. Side docking of the robot allows ready access to the perineum and acceptable placement of the robot to successfully complete ureteral repair.

Comparison of lower urinary tract symptoms between women with detrusor overactivity and impaired contractility, and detrusor overactivity and preserved contractility.

PURPOSE: We compared symptoms in women with detrusor overactivity with impaired contractility and women with detrusor overactivity who had preserved contractility. MATERIALS AND METHODS: The study included 359 consecutive women with detrusor overactivity who underwent multichannel urodynamics at our department between 2009 and 2011. The women were divided into 2 groups, including 151 (42%) with detrusor overactivity and impaired contractility, and 208 (58%) with detrusor overactivity and preserved contractility. We compared the 2 groups. RESULTS: Women with detrusor overactivity and impaired contractility were older (mean ± SD age 73.2 ± 17.3 vs 54.1 ± 20.7 years) with a higher frequency of diabetes mellitus (49% vs 31%, each p <0.001). The prevalence of previous urinary retention and recurrent cystitis was significantly higher in women with impaired contractility (7% vs 1%, p <0.01 and 22% vs 7%, p <0.001, respectively). Mean post-void residual urine was greater in the group with impaired contractility (89 ± 42 vs 21 ± 18 ml) and the mean maximal flow rate was lower (11 ± 6 vs 23 ± 5 ml per second, each p <0.001). The frequency of storage symptoms was similar in the 2 groups. However, voiding symptoms were more common in women with impaired contractility, including a slow stream in 69% vs 42%, an intermittent stream in 72% vs 26%, hesitancy in 35% vs 22%, straining in 84% vs 26%, terminal dribbling in 73% vs 42% and incomplete emptying in 71% vs 49% (p <0.001). CONCLUSIONS: Women with detrusor overactivity and impaired contractility are older than women with detrusor overactivity and preserved detrusor contractility. Urinary retention and recurrent cystitis are more frequent in women with detrusor overactivity and impaired contractility, and voiding symptoms are significantly more common.

How accurate is our clinical prediction of "minimal prostate cancer"?

BACKGROUND: Recommendations for active surveillance versus immediate treatment for low risk prostate cancer are based on biopsy and clinical data, assuming that a low volume of well-differentiated carcinoma will be associated with a low progression risk. However, the accuracy of clinical prediction of minimal prostate cancer (MPC) is unclear. OBJECTIVES: To define preoperative predictors for MPC in prostatectomy specimens and to examine the accuracy of such prediction. METHODS: Data collected on 1526 consecutive radical prostatectomy patients operated in a single center between 2003 and 2008 included: age, body mass index, preoperative prostate-specific antigen level, biopsy Gleason score, clinical stage, percentage of positive biopsy cores, and maximal core length (MCL) involvement. MPC was defined as < 5% of prostate volume involvement with organ-confined Gleason score < or = 6. Univariate and multivariate logistic regression analyses were used to define independent predictors of minimal disease. Classification and Regression Tree (CART) analysis was used to define cutoff values for the predictors and measure the accuracy of prediction. RESULTS: MPC was found in 241 patients (15.8%). Clinical stage, biopsy Gleason's score, percent of positive biopsy cores, and maximal involved core length were associated with minimal disease (OR 0.42, 0.1, 0.92, and 0.9, respectively). Independent predictors of MPC included: biopsy Gleason score, percent of positive cores and MCL (OR 0.21, 095 and 0.95, respectively). CART showed that when the MCL exceeded 11.5%, the likelihood of MPC was 3.8%. Conversely, when applying the most favorable preoperative conditions (Gleason < or = 6, < 20% positive cores, MCL < or = 11.5%) the chance of minimal disease was 41%. CONCLUSIONS: Biopsy Gleason score, the percent of positive cores and MCL are independently associated with MPC. While preoperative prediction of significant prostate cancer was accurate, clinical prediction of MPC was incorrect 59% of the time. Caution is necessary when implementing clinical data as selection criteria for active surveillance.

Hyperbaric oxygen therapy for hemorrhagic radiation cystitis.

BACKGROUND: Hemorrhagic radiation cystitis (HRC) is a significant clinical problem that occurs after pelvic radiation therapy and is often refractory. OBJECTIVES: To evaluate the efficacy and safety of hyperbaric oxygen therapy (HBO) for HRC. METHODS: Daily 90 minute sessions of HBO at 2 ATM 100% oxygen were given to 32 HRC patients with ASTRO grades 3-4 hematuria. RESULTS: The median age was 72.5 (48-88 years). The median time interval between radiation therapy and HBO was 4 years (1-26 years). The patients received a median of 30 HBO sessions (3-53). Hematuria resolved in 27 patients (84%) and persisted in 5. Cystectomy was required in two, and ileal-conduit and bilateral percutaneous nephrostomies were performed in one and two patients, respectively. With a median follow-up of 12 months (5-74 months), the hematuria cleared completely in 16 patients (59%) and mild hematuria requiring no further treatment recurred in 10 others. Another patient with ASTRO grade 4 hematuria needed bladder irrigation and blood transfusions. Complications included eardrum perforation in four patients and transient vertigo and mild hemoptysis in one case each. None of them required HBO discontinuation. CONCLUSIONS: HBO controlled bleeding in 84% of the patients. A durable freedom from significant hematuria was achieved in 96% of the patients. HBO seems to be an effective and safe modality in patients with HRC.

Adjuvant chemotherapy after radical cystectomy: Do all patients who need chemotherapy after surgery actually receive it?

Background: Compliance with the guideline recommendations for neoadjuvant chemotherapy in patients with muscle-invasive bladder cancer is incomplete. The adjuvant chemotherapy approach has the advantage of pathology-based decision-making, allowing for patient selection. In addition, radical surgery is not delayed and treatment-related toxicity does not impair surgical fitness. The proportion of patients who completed chemotherapy after cystectomy among those who were fit and in need of treatment were evaluated. The reasons for not completing adjuvant chemotherapy were determined. Materials and methods: We retrospectively evaluated all patients who had undergone radical cystectomy at our center over the last 7 years. Indications for adjuvant chemotherapy included pathological T > 2, any node+, or surgical margin involvement. Only patients who were fit for chemotherapy before surgery were included in the study. Results: Of the 52 patients with muscle-invasive bladder cancer, 14 received neoadjuvant chemotherapy or unfit for chemotherapy were excluded. Of the remaining 38 patients, 14 (37%) had bladder-confined cancers and did not require additional chemotherapy. Of the 24 patients who needed chemotherapy and were fit to receive it, 8 patients completed treatment (33%), and 3 discontinued treatment due to toxicity. Twelve patients (50%) declined chemotherapy, whereas 1 patient became unfit for chemotherapy after surgery. Conclusions: While the adjuvant chemotherapy approach could save unnecessary treatment in 37% of patients, two-thirds of those who needed chemotherapy did not complete it. Patient refusal was the primary reason for not receiving treatment.

Imaging and Chemical Analysis of External and Internal Ureteral Stent Encrustation.

Introduction: Ureteral stents are effective in alleviating flow disruptions in the urinary tract, whether due to ureteral stones, strictures or extrinsic ureteral obstruction. However, significant stent encrustation on the external and/or internal stent lumen walls can occur, which may interfere with stent functioning and/or removal. Currently, there is only limited, generally qualitative, information on the distribution, mineral structure, and chemical content of these deposits, particularly in terms of stent lumen encrustation. Objective: To quantify, in an initial investigation, external and internal encrustation in representative, intact ureteral stents. The study investigates possible correlations between patterns of external and internal encrustation, determines mineral structure and chemical composition, and examines the potential for stent lumen obstruction even in the absence of external stent wall encrustation. Study Design: High-resolution, laboratory micro-computed tomography (micro-CT) was used to non-destructively image external and internal stent encrustation in four representative stents. X-ray diffractometry (XRD) and scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDS) enabled parallel analysis of mineral structure and chemical content of samples collected from external and internal encrusted material along the distal, proximal and mid-ureteral stent regions. Results: Extensive stent lumen encrustation can occur within any region of a stent, with only incidental or minor external encrustation, along the entire length of the stent. External and internal encrusted materials in a given stent are generally similar, consisting of a combination of amorphous (mostly organic) and crystalline mineral deposits. Conclusion: Micro-CT demonstrates that significant stent lumen encrustation can occur, which can lead to partial or full stent lumen occlusion, even when the exterior stent wall is essentially free of encrusted material.

Design of a fully intraureteral stent and proof-of-concept in vivo evaluation.

Background: Ureteral stents are employed regularly to facilitate urine drainage and ureteral healing in a wide variety of endourological procedures, associated mainly with ureteral stone obstruction. However, stent use frequently impairs patient quality of life, which is generally attributed to the presence of anchoring stent curls in the bladder and/or kidney. The purpose of this study was to examine the potential effectiveness and safety of a newly designed, fully intraureteral stent, in an initial proof-of-concept in vivo evaluation. Methods: "Yoticurl" stents were synthesized from copolymeric, commercially-available ureteral stents. A first test to confirm the intended expansion of the spiral curls in a ureter was performed on a pig cadaver. Subsequently, a preliminary in vivo evaluation in a single pig model was completed to test stent viability, over a period of 25 days. Two stents were inserted to fully intraureteral positions into the two ureters, by standard human endourological procedure. Daily observational checks of the pig, and regular radiographic analyses were performed; the animal was then euthanized and examined by explorative laparotomy, followed by histological analysis of kidney, ureter and bladder tissue samples. Results: The pig displayed normal activity, appetite and sleep patterns, and radiography indicated free flow of urine, and no significant stent migration nor anatomical abnormalities. Subsequent histology found only mild inflammation in the ureter. Conclusions: The innovative stent design tested here, if ultimately proven safe and effective for human use, may offer an alternative to currently available stents for multiple indications.

Influence of Single Stent Size and Tandem Stents Subject to Extrinsic Ureteral Obstruction and Stent Occlusion on Stent Failure.

Background and Purpose: Drainage of obstructed kidney attributable to extrinsic ureteral obstruction (EUO), required to prevent renal damage, is often achieved using Double-J ureteral stents. However, these stents fail frequently, and there is considerable debate regarding what stent size, type, and configuration offer the best option for sustained drainage. In this study, we examine the impact of stent diameter and choice of single/tandem configuration, subject to EUO and various degrees of stent occlusion, on stent failure. Materials and Methods: Computational fluid dynamics simulations and an in vitro ureter-stent experiment enabled quantification of flow behavior in stented ureters subject to EUO and stent occlusions. Various single and tandem stents under EUO were considered. In each simulation and experiment, changes in renal pressure were monitored for different degrees of stent lumen occlusion, and onset of stent failure as well as simulated distributions of fluid flow between stent and ureter lumina were determined. Results: For an encircling EUO that completely obstructs the ureter lumen, with or without partial stent occlusion, the choice of stent size/configuration has little effect on renal pressure. The pressure increases significantly for ∼90% stent lumen occlusion, with failure at >95% occlusion, independent of stent diameter or a tandem configuration, and with little influence of occlusion length along the stent. Conclusions: Stent failure rate is independent of stent diameter or single/tandem configuration, for the same percentage of stent lumen occlusion, in this model. Stent failure incidence may decrease for larger diameter stents and tandem configurations, because of the larger luminal area.

When should we give up on expectant management for patients with proximal ureteral stones?

Background: Proximal ureteral stones (PUS) have relatively low rates of spontaneous expulsion. However, some patients do well on expectant management. Our aim was to compare risk factors for surgical intervention in patients with PUS who underwent primary intervention to those subjected to expectant management. Materials and methods: We retrospectively reviewed the medical charts of patients presented to the emergency room with symptoms of renal colic and underwent computerized tomography between August 2016 and August 2017. A total of 97 consecutive patients were identified with up to 10mm PUS. We collected patient demographics, clinical, and imaging data, and performed binary regression analysis for risk of intervention. Results: The average age was 49years (range 17-97) and average stone size was 7.1mm (range 3-10). Forty-one patients underwent immediate intervention while the remaining 56 patients were treated conservatively. Of the 56 patients treated conservatively, 26 underwent delayed intervention while 30 reported spontaneous stone expulsion. On univariate analysis of all 97 patients, statistically significant risk factors for intervention were found based on stone size, age, serum lymphocyte, platelet counts, and stone density. Of these risk factors, stone size ≥ 7mm (p = 0.012, odds ratio = 5.4) and platelet count ≤ 230K/µL (p = 0.027, odds ratio = 4.9) remained statistically significant on multivariate analysis. Conclusion: Stone size and platelet count were found to be risk factors for surgical intervention in patients with up to 10mm PUS. These findings may assist in identifying patients who are more suitable for conservative approach.

Potential Markers to Reduce Non-Contrast Computed Tomography Use for Symptomatic Patients with Suspected Ureterolithiasis.

Most patients with ureterolithiasis are managed successfully with conservative treatment. In this context, delineation of clinical risk factors that identify patients with low risk for surgical intervention may reduce use of Non-Contrast Computed Tomography (NCCT). Here, emergency department patient files from a 14-month period were reviewed retrospectively, to identify patients who underwent NCCT and showed a ureteral stone. Demographic, clinical and laboratory information was collected. Patients were grouped to either requiring surgical intervention (Group 1) or having successful conservative management (Group 2). The cohort included 368 patients; 36.1% ultimately required surgical intervention (Group 1) and 63.9% were successfully treated conservatively (Group 2). On univariate analysis, patients who required surgical intervention were older, had longer duration of symptoms, had history of urolithiasis and surgical intervention for urolithiasis and had higher serum creatinine levels. Multivariate analysis identified the following risk factors associated with surgical intervention: creatinine >1.5 mg/dL, duration of symptoms ≥ 1.5 days and age > 45 years. Patients with 0, 1, 2 or 3 of the identified risk factors had 19%, 32%, 53% and 73% likelihood, respectively, of surgical intervention. Incorporating these data may reduce the use of NCCT scans in patients who are likely to pass a stone via conservative management.

The Impact of Radiographic, Metabolic and Demographic Characteristics on Kidney Stone Recurrence.

Urolithiasis is a frequent disease with cited rates of recurrence after initial diagnosis that vary widely and range between 35% and 50%. We assessed the radiographic recurrence rate in patients with urinary stones and its risk factors. We retrospectively identified patients who were diagnosed with urinary stones on non-contrast computed tomography from 2010 to 2011, and underwent another imaging examination at least six months afterwards. We collected patient demographic, clinical, laboratory and radiologic data and compared patients with and without urinary stone recurrence. Ultimately, 237 patients were included in the study; the mean follow-up was 6.7 years; 88 patients (37.1%) had recurrence based on our recurrence criteria. On univariate analysis, the significant parameters for recurrence were baseline serum calcium and uric acid, stone location in the kidney, surgical intervention and stone burden volume. On multivariate analysis, surgical intervention (OR 3.07, p = 0.001), baseline calcium (OR 2.56, p = 0.011), baseline uric acid (OR 1.30, p = 0.021) and stone location in the kidney (OR 2.16, p = 0.012) were associated with higher risk of recurrence. These findings may guide personalized follow-up protocols for patients with urolithiasis based on their risk factors.

[Female urethral diverticula--clinical and surgical aspects].

Urethral diverticula are a common cause of chronic genitourinary symptoms in women. They occur in 5% of women overall, with higher frequencies in selected populations of symptomatic women. The classical presentation is with recurrent urinary tract infections and post-micturition dribbling but almost any urinary symptom may be a presenting feature. Newer imaging modalities such as magnetic resonance imaging and perineal ultrasound are now widely available and urethral diverticula, that were previously unrecognized, can now be more easily detected. However, despite the availability of effective diagnostic techniques, diagnosis is often delayed. This is due to a lack of awareness among clinicians. These patients are often inappropriately treated for other conditions, significantly delaying the proper management of their condition. A high index of suspicion, a careful examination and referral for appropriate investigation will improve the number correctly diagnosed and lead to considerable benefit since most symptomatic cases can be cured by appropriate surgery. This review aims to summarize the presentation, investigation and management of female urethral diverticulum. Hopefully, greater awareness will lead to more timely diagnosis and appropriate treatment.

Failure of ureteral stents subject to extrinsic ureteral obstruction and stent occlusions.

PURPOSE: To quantify the occurrence of stent failure and the dynamic behavior of urine flow in ureter-stent systems, including the relative flow in the ureter and stent lumina, subject to various degrees of ureter and stent blockage. METHODS: Numerical simulations based on computational fluid dynamics (CFD) were used to quantify urine flow behavior in stented ureters, in the presence of extrinsic ureteral obstruction (EUO) and stent occlusions. Two stented ureter configurations were considered, one with circumferential occlusion of the ureter and the second with pressure on one side of the ureter wall. The pressure within the renal unit for different degrees of ureter closure and stent lumen occlusion was determined systematically. Onset of stent failure and the distribution of urine flow between stent and ureter lumina were determined. RESULTS: In the case of EUO completely encircling the ureter, causing 100% obstruction of the ureter lumen, pressure in the renal unit is essentially unaffected until the stent lumen reaches ~ 90% occlusion, and fails only with > 95% occlusion. Occlusions of 50% in stent side holes in the vicinity of the EUO only alter local flow patterns but have no significant influence on renal unit pressure. For EUO deforming and compressing the ureter from one side, with ~ 50% reduction in ureter lumen, urine drainage proceeds with negligible increase in renal pressure even with 100% occlusion in the stent lumen. CONCLUSION: CFD simulations show that stent failure under EUO tends to occur suddenly, only when both ureter and stent lumina become almost fully blocked.