Biodegradable braided poly(lactic-co-glycolic acid) urethral stent combined with dutasteride in the treatment of acute urinary retention due to benign prostatic enlargement: a pilot study

OBJECTIVE

To evaluate, in a pilot study, the efficacy and safety of combining a braided poly(lactic‐co‐glycolic acid) (PLGA, a copolymer of l ‐lactide and glycolide) urethral stent and dutasteride in the treatment of acute urinary retention (AUR) due to benign prostatic enlargement (BPE).

PATIENTS AND METHODS

Ten men with AUR due to BPE were treated as outpatients. A biodegradable braided PLGA urethral stent was inserted into the prostatic urethra, using a specially designed insertion device under visual control. Dutasteride treatment was started and the patients were followed up for 3 months after insertion of the stents.

RESULTS

In all patients the stents were placed successfully with the new insertion device. All men were able to void after inserting the stent. At 1 month five patients voided freely with a low residual urine volume (<150 mL), two voided but had a high residual urine volume and a suprapubic catheter was placed, and three needed a suprapubic or an indwelling catheter before 1 month, due to AUR or comorbidities. At 3 months five patients were voiding with no problems.

CONCLUSIONS

We have developed a new and effective insertion device for biodegradable braided prostatic stents. The new braided‐pattern stent overcomes the earlier problems of migration and sudden breakage into large particles associated with biodegradable spiral stents. However, the mechanical properties of the new stent need to be improved and tested in a longer follow‐up. We consider that this new biodegradable braided‐pattern urethral stent could provide a new option in the future treatment of AUR.     

Biodegradable urethral stents seeded with autologous urethral epithelial cells in the treatment of post‐traumatic urethral stricture: a feasibility study in a rabbit model

OBJECTIVE

To evaluate the adhesion and growth of rabbit urethral epithelial cells (UECs) on a biodegradable unbraided mesh urethral stent, and to assess the feasibility and effect of the cell‐seeded urethral stent for treating post‐traumatic urethral stricture (PTUS) in a rabbit model.

MATERIALS AND METHODS

Rabbit UECs were collected by biopsy from adult rabbit urethra and seeded onto the outer layer of a mesh biodegradable urethral stent. The growth of UECs in cell‐scaffolds was assessed by scanning electron microscopy, immunohistochemical and fluorescence staining. In all, 32 male New Zealand rabbits were used, with either PTUS or uninjured, as a control group. Cell‐seeded stents were implanted into the rabbits strictured urethra. The histological and immunohistochemical findings were assessed after death at 1, 2, 8, 12 and 24 weeks, respectively. The reconstruction and function were evaluated by urethroscopy and retrograde urethrography.

RESULTS

The cultured UECs adhered to the stent and grew well. Immunohistochemistry showed that the cells were stained positively for cytokeratin. At 4 weeks, vs 2 weeks, the thickness of the papillary projections of the epithelium decreased and inflammatory cell infiltration diminished. At 24 weeks the injured urethra was completely covered by integrated regeneration of three to five layers of urothelium. There was no evidence of voiding difficulty, stricture recurrence or other complications.

CONCLUSIONS

The unbraided mesh biodegradable urethral stent with autologous UECs seemed to be feasible for treating PTUS in the rabbit urethra, and provides a hopeful avenue for clinical application allowing reconstruction of PTUS.     

A new biodegradable braided self-expandable PLGA prostatic stent: an experimental study in the rabbit

PURPOSE: The biodegradable PLGA (a copolymer of L-lactide and glycolide) urethral stent with a spiral configuration has been used clinically for the prevention of postoperative urinary retention after different types of thermal therapy for benign prostatic hyperplasia. A new braiding pattern for this stent has recently been developed by our group. The aim here was to investigate the in situ degradation and biocompatibility of the new braided stent in the rabbit urethra. MATERIALS AND METHODS: PLGA stents with a one-over-one braiding pattern and steel stents served as controls that were inserted into the posterior urethras of 24 male rabbits using a special delivery instrument. The animals were sacrificed after 1 week, 1 month, 2 months, or 4 months, and light microscopy and histologic analyses were performed. RESULTS: The delivery instrument worked well and cystoscopy was not needed in the insertion process. The braided PLGA stents degraded smoothly in 1 to 2 months. The metallic stents induced more epithelial hyperplasia and epithelial changes than the biodegradable stents at all time points analyzed. These differences increased during follow-up. CONCLUSION: The degradation process was well controlled and the biodegradable stents were more biocompatible than the metallic stents. The new stent can be inserted into the posterior urethra without cystoscopic aid.     

Biocompatibility properties of a new braided biodegradable urethral stent: a comparison with a biodegradable spiral and a braided metallic stent in the rabbit urethra

OBJECTIVE: To compare the biocompatibility properties of a new braided biodegradable self-reinforced poly-L-lactic acid (SR-PLLA) urethral stent to the former spiral biodegradable SR-PLLA stent and the stainless steel stent in a rabbit model. MATERIALS AND METHODS: In all, 54 male New Zealand White rabbits were anaesthetized and stents inserted into the prostatic urethra, three of each kind for each sample time. The rabbits were killed after 1, 3, 6, 9, 12 or 15 months and light microscopy and scanning electron microscopy used to analyse the effects. RESULTS: The disintegration of the braided SR-PLLA stent was more closely controlled than that of the spiral SR-PLLA stent. The metallic stent induced epithelial hyperplasia and polyposis earlier than the biodegradable stents, and in these rabbits the polyposis disappeared after the disintegration process. There were no differences in the histological analyses between the biodegradable stents, whereas the metallic stents caused the strongest inflammatory reactions. CONCLUSIONS: The braided SR-PLLA urethral stent functioned well in the rabbit urethra and clinical studies are already planned.     

Biocompatibility and implantation properties of 2 differently braided, biodegradable, self-reinforced polylactic acid urethral stents: an experimental study in the rabbit

PURPOSE: Biodegradable urethral stents have been in clinical use for more than 10 years. To solve the problems connected with the helical spiral configuration of the stents used to date we developed a new tubular mesh configuration and evaluated the biocompatibility properties and degradation time of 2 differently braided stents in the rabbit urethra. MATERIALS AND METHODS: The biodegradable, self-expanding stents were made of self-reinforced polylactic acid polymer blended with BaSO4 (Alfa Chem, Kings Point, New York). Two braiding patterns, namely a diamond 1/1 and a regular 2/2 + 1 (Prodesco, Perkasie, Pennsylvania), were used to produce a tubular mesh configuration. Stainless steel stents with 1/1 braiding served as controls. The stents were inserted into the posterior urethra of 36 male rabbits. The animals were sacrificed after 1 week, 1 month, 6 months or 12 months. Light microscopy and scanning electron microscopy analyses were done. RESULTS: Tissue reactions to operative trauma were seen in all specimens at week 1. The changes gradually abated in the biodegradable stent groups, whereas chronic inflammatory changes and fibrosis were increasingly seen with metallic stents after 6 months. Epithelial hyperplasia increased with time for all stent types and materials. As expected, stent fragmentation started at 6 months. CONCLUSIONS: Biodegradable polymers are suitable materials for braided urethral stents. However, the braided configuration of the stent with a decreased mass of material does not prevent the development of epithelial hyperplasia. The biodegradable, self-expanding, braided stents functioned well in the rabbit urethra and are suitable for clinical studies.     

Expansion and fixation properties of a new braided biodegradable urethral stent: an experimental study in the rabbit

PURPOSE: Biodegradable spiral urethral stents have been used with favorable results combined with thermal treatments of the prostate and for recurrent urethral strictures but the configuration of the helical spiral is not ideal. We developed a new tubular mesh configuration for the biodegradable urethral stent and evaluated its expansion and locking properties in the rabbit urethra. MATERIALS AND METHODS: The stents were made of self-reinforced polylactic acid polymer (Bionx Implants, Ltd., Tampere, Finland) blended with BaSO (Alfa Chem, New York, New York) to achieve radiopacity. Two braiding patterns, that is 1 over 1 and 2 over 2 + 1, were used to produce a tubular mesh structure. Stainless steel stents (pattern 1 over 1) served as controls. The stents were inserted into the posterior urethra of 27 male rabbits. The animals were sacrificed after 1 week, 1 and 6 months, respectively. X-rays were done immediately after stent insertion and at sacrifice. Longitudinal movement and expansion were assessed on the x-rays.(4) RESULTS: All stents maintained position in the urethra without fixation. Macroscopic disorientation of the structure of the 2 over 2 + 1 braided self-reinforced polylactic acid polymer stents began before 1 month, while 1 over 1 braided stents retained their construction. At 6 months 3 of 6 biodegradable stents were degraded. Average longitudinal movement was 2 mm. (range 1 to 3) in the 1 over 1 self-reinforced polylactic acid polymer group, 2 mm. (range 0 to 7) in the 2 over 2 + 1 polylactic acid group and 3 mm. (range 3 to 3) in controls at 1 month. CONCLUSIONS: Biodegradable polymers are suitable materials for braided urethral stents. The expansion properties of the 2 braiding models tested in this study sufficed to fix the stents in situ in the prostatic urethra. However, the 1 over 1 braiding pattern was superior to the 2 over 2 + 1 pattern, in that it retained its macroscopic construction until the degradation of single self-reinforced polylactic acid polymer fibers.     

生物可降解性尿道内支架修复战伤性尿道狭窄的研究

目的建立战伤性尿道狭窄动物模型,探讨生物可降解性尿道内支架对其进行重建修复的可行性。方法将新西兰雄兔28只分为两组,实验组(n=20):以定位爆炸法建立尿道狭窄模型。一月后行逆行尿道造影、尿道镜检查,并切除狭窄段尿道,行病理组织学观察证实。后置入人工合成生物可降解尿道内支架,置入术后2、4、8、12周分别行逆行尿道造影、尿道镜检查以及尿流动力学检测。并在以上各时间点处死5只动物,取狭窄处尿道组织,观察组织学修复重建情况。对照组(n=8):于实验组爆炸处理后4周和支架置入12周,分别取对照组4只动物与实验组对比观察。结果实验组所有动物爆炸后4周在尿道球部狭窄形成稳定狭窄模型(狭窄段长5～10 mm,尿道腔缩窄50%以上)。尿道内支架置入后2周,组织学观察见黏膜上皮新生迹象,并有炎性细胞浸润;4周时上皮新生明显,炎性细胞消失;8周时出现尿道平滑肌细胞再生,12周时见损伤后尿道组织结构完全修复,与正常尿道组织比较差异无统计学意义(P>0.05)。。同时间点尿道镜检查证实尿道腔隙、黏膜形态结构无异于正常对照组。尿流动力学检测显示两组间差异无统计学意义(P>0.05)。。结论应用成功建立的战伤性尿道狭窄动物模型,证实生物可降解性尿道内支架能作为修复战伤性尿道狭窄的理想材料,具有损伤小,易操作,功能恢复快的特点。     

Anatomical approach for surgery of the male posterior urethra

OBJECTIVE

To investigate, in a morphological study, the anatomy of the male rhabdosphincter and the relation between the membranous urethra, the rhabdosphincter and the neurovascular bundles (NVBs) to provide the anatomical basis for surgical approach of the posterior urethra as successful outcomes in urethral reconstructive surgery still remain a challenging issue.

MATERIALS AND METHODS

In all, 11 complete pelves and four tissue blocks of prostate, rectum, membranous urethra and the rhabdosphincter were studied. Besides anatomical preparations, the posterior urethra and their relationship were studied by means of serial histological sections.

RESULTS

In the histological cross‐sections, the rhabdosphincter forms an omega‐shaped loop around the anterior and lateral aspects of the membranous urethra. Ventrally and laterally, it is separated from the membranous urethra by a delicate sheath of connective tissue. Through a midline approach displacing the nerves and vessels laterally, injuries to the NVBs can be avoided. With meticulous dissection of the delicate ventral connective tissue sheath between the ventral wall of the membranous urethra and the rhabdosphincter, the two structures can be separated without damage to either of them. This anatomical approach can be used for dissection of the anterior urethral wall in urethral surgery.

CONCLUSIONS

Based on precise anatomical knowledge, the ventral wall of the posterior urethra can be dissected and exposed without injuring the rhabdosphincter and the NVBs. This approach provides the basis for sparing of the rhabdosphincter and for successful outcomes in urethral surgery for the treatment of bulbo‐membranous urethral strictures.     

A bioresorbable urethral stent

Summary The aim of the present study was to examine the suitability of biodegradable polymers as materials for a urethral stent. A new urethral stent made of biodegradable self-reinforced poly-l-lactide (SR-PLLA) was implanted in 16 male rabbits after urethrotomy. Seven stents of stainless steel served as controls. The dimensions of the two types of stents were identical: length 15 mm, diameter 8.2 mm. The mechanical construction was a helical spiral. The SR-PLLA spiral was sustained with three microspirals, and the whole device was coated withdl-lactide to achieve an active initial tissue reaction and better tissue penetration. The SR-PLLA stent showed more favourable implantation properties than the steel one. Within 6 months all PLLA stents had implanted, and the tissue reaction around the stent material was minimal. The helical spiral of stainless steel induced a remarkable inflammatory reaction due to poor implantation properties. We suggest that biodegradable SR-PLLA is a promising material for a urethral stent to prevent re-stenosis of urethral strictures.     

生物可降解材料聚乳酸/聚羟基乙酸复合壳聚糖在人工冠状动脉血管支架制备中的应用

第一代金属裸支架和第二代涂层支架介入治疗冠状动脉粥样硬化性心脏病(冠心病)已得到广泛应用。由于长期存在金属支架异物刺激及其携带的药物扰乱血管壁各层细胞生长,引起支架内再狭窄和血管栓塞,远期仍有较多的主要心血管不良事件发生和需要再血管化治疗。因此,由聚酯、聚碳酸酐及聚磷酸酯等高分子材料制备的完全可生物降解吸收支架及药物洗脱支架应运而生,其中聚乳酸(poly-lactic acid,PLA)、聚羟基乙酸(poly-glycolicacid,PGA)、壳聚糖、聚己内酯(poly-caprolactone,PCL)及一些共聚物如聚乳酸/聚羟基乙酸共聚物(poly-lactic-co-glycolic acid,PLGA)材料制备的心血管植入支架的安全性、组织及血液相容性已得到证实,然而这些支架具有各自的缺点,如PLA降解较慢质硬易断裂柔韧性不足,PGA降解较快质软支撑力不足,支架降解太快或者太慢,均难以达到有效支撑,支架植入后容易出现血管损伤、弹性回缩,导致血管再狭窄及血栓形成,远期效果不佳。通过优化组合不同摩尔比的PLA和PGA及壳聚糖涂层,可以获得具有更好的生物相容性、适度的降解速率(约3～6个月完全降解)、足够的机械强度、较低的炎症反应和伸展度良好的复合材料,从而为制备完全生物可降解冠状动脉支架奠定实验基础。     

Bulbar urethral ligation for managing persistent urinary incontinence in young men with myelomeningocele

OBJECTIVE

To report our experience with ligation of the bulbar urethra for treating refractory stress incontinence in a selected group of young men with neuropathic bladders secondary to myelomeningocele (MM), in whom primary anti‐incontinence procedures had failed.

PATIENTS AND METHODS

Persistent urethral incontinence leading to chronic perineal skin ulceration can occur in these patients, despite aggressive medical and surgical efforts to decrease wetting by increasing bladder capacity, compliance and outlet resistance. Four young men with MM had bulbar urethral ligation; all had undergone a previous ileocystoplasty and functioning continent catheterizable channels (CCC, three appendicovesicostomies, one Monti procedure). Three patients had primary bladder neck procedures using rectus fascia slings, and secondary attempts were made at urethral bulking in two patients. All patients had persistent incontinence through their native urethra, with dry intervals of <2 h.

RESULTS

The bulbar urethra was ligated through a small midline perineal incision at 1 year after augmentation, and successfully resolved incontinence in all four patients. All reported satisfaction with their bladder regimen at a mean (range) follow‐up of 49 (20–93) months. There were no perineal wound infections. While one patient developed bladder calculi, no patient developed urethral stones, febrile urinary tract infections, fistulae or bladder perforations.

CONCLUSIONS

We report the results of bulbar urethral ligation for resolution of incontinence in patients with MM in whom anti‐incontinence bladder neck procedures had failed. Ligation of the urethra is effective, and can be considered an alternative treatment for refractory urinary incontinence in patients with a functional CCC in whom previous bladder neck‐supporting procedures have failed.     

Non-transecting anastomotic bulbar urethroplasty: a preliminary report

Study Type – Therapy (case series) Level of Evidence 4 What's known on the subject? and What does the study add? Excision of a stricture and end‐to‐end anastomosis of the two ends is thought to be the best form of treatment for short strictures of the proximal bulbar urethra but involves transecting the main blood supply of the corpus spongiosum and the urethra. This is a preliminary report of achieving the same goal but without transecting the blood supply of the corpus spongiosum of the urethra.

OBJECTIVE

• ? To report our early experience with a novel approach to the excision and end‐to‐end anastomotic repair of bulbar urethral strictures.

PATIENTS AND METHODS

• ? A total of 22 patients underwent excision and end‐to‐end anastomosis of a proximal bulbar urethral stricture using a technique in which the corpus spongiosum is not transected, so as to maintain its blood supply intact.
• ? The range of follow‐up was 6–21 months and for 16 patients the follow up was ≥1year.

RESULTS

• ? At 1 year of follow‐up there was no evidence of a recurrent stricture on symptomatic assessment or uroflowmetry in the 16 patients.
• ? On urethrography one patient has a urethral calibre 80% of normal. In the other 15 the calibre is normal or greater than normal.

CONCLUSION

• ? The non‐transecting anastomotic bulbar urethroplasty technique used appears to give results that are as good as those of traditional anastomotic urethroplasty with less surgical trauma.

     

The promise of urethral pressure reflectometry: an update

Introduction and hypothesis

The urethral closure mechanism in women is incompletely understood. Measuring closure function in a collapsed urethral tube without distending the tube and changing its natural shape is impossible with conventional methods. Over the last decade, studies with urethral pressure reflectometry (UPR), a method that measures pressure and the corresponding cross-sectional area along the entire length of the urethra continuously by means of acoustic reflectometry, have been performed. The studies have mainly been performed on patients with stress urinary incontinence (SUI).

Methods

Our aim was to provide an overview of the studies conducted with UPR, establishing whether the method may be used in clinical practice. We reviewed all literature published on UPR.

Results

Urethral pressure reflectometry is easily performed with limited bother for the patient. The catheter consists of a 45-cm-long PVC tube connected to a thin and highly flexible polyurethane bag, which is placed in the urethra. When inserted, the bag only occupies 0.4 mm² of the urethra, respecting the natural shape and orientation of the urethra and, most importantly; respecting the laws of physics when measuring urethral pressure. UPR can discriminate patients with SUI from continent women and separate assessment of the sphincter function and support system is possible. Also, UPR has revealed statistically significant differences in urethral pressures after drug therapy for SUI.

Conclusions

We conclude that UPR has a place in clinical practice. The method has shown groundbreaking potential in the understanding of urethral dysfunction in SUI patients.

     

Transperineal bulbo-prostatic anastomosis for posterior urethral stricture associated with false passage: a single-centre experience

Study Type – Therapy (case series) Level of Evidence 4 What’s known on the subject? and What does the study add? The emergency treatment of patients with PFUDD in developing countries is not currently codified and the majority of these patients have been treated using incorrect procedures that add iatrogenic damage to the trauma. Sometimes urethral dilatation gruffly and repeatedly wound lead to formation of urethral false passage which results in infection and incontinence. The treatment of urethral false passage is still a major challenge for urologists. False passage can lead to prolonged unhealed infections, increase the scar around the urethra, increasing stricture significantly. If preoperative examination was careless, it leads to identify false passage difficultly intra‐operative, the variation of direction when the curved sound was used as internal guidance, anastomosis between distal urethra and bladder wall near the orificium urethrae internum, leading to surgical failure. Cystourethrogram, flexible cystocopy pre‐operatively and dissect urethral bulb carefully are key points of urethroplasty for posterior urethral stricture with false passage. Then to pass a curved sound via the suprapubic tract into the posterior urethra to act as a guide for subsequent excision of all scar tissue.

OBJECTIVE

? To evaluate the management of traumatic posterior urethral stricture associated with false passage, as this remains a challenge for urologists.

PATIENTS AND METHODS

? From January 2000 to February 2010, 19 patients (mean (range) age 34 [25–52] years) with traumatic posterior urethral obliteration associated with false passage were evaluated and treated at our centre. ? All patients underwent perineal excision and primary anastomotic urethroplasty using cystoscopy by the suprapubic route to insert a guidewire into the original bladder neck, allowing exposure of the normal posterior urethra. ? Patients underwent voiding cysto‐urethrography 1 month after the procedure. When symptoms of decreased force of stream were present and uroflowmetry was <15 mL/s, urethrography and urethroscopy were repeated. ? Clinical outcome was considered a failure when any postoperative instrumentation was needed, including dilatation.

RESULTS

? The mean (range) follow‐up was 12 (9–14) months. The overall success rate was 84%. ? Three patients (16%) with persistent voiding difficulty developed a short anastomotic stricture 1–3 months after surgery. ? The mean maximum urinary flow rate after surgery was 20.01 mL/s and no patient had urinary incontinence.

CONCLUSION

? The preoperative use of flexible cystoscopy via the suprapubic route represented a successful key point of urethroplasty for posterior urethral stricture associated with false passage.     

The ‘buoy’ stent: evaluation of a prototype indwelling ureteric stent in a porcine model

OBJECTIVE

To assess a prototype ureteric ‘buoy’ stent with a 10 F upper body tapering to a 3F tail, developed to potentially reduce stent‐related irritative symptoms while providing an adequate mould for healing after endopyelotomy.

MATERIALS AND METHODS

Eighteen Yucatan minipigs had the stent placed either into the intact ureter (phase I) or after Acucise proximal endoureterotomy (phase II). Buoy stents were compared to 10/7 F endopyelotomy stents and to standard 7 F stents in phases I and II, respectively. The pigs were assessed for vesico‐ureteric reflux, hydronephrosis and infection, before stent insertion and at harvest. Stents were weighed before and after placement and the removal force was measured. Pressure/flow studies, antegrade nephrostograms and specimens for histopathology from the renal pelvis, ureter and vesico‐ureteric junction (VUJ) were obtained at harvest.

RESULTS

Thirteen minipigs survived the entire study. Ureteric flow with the stents in situ was better for buoy stents than for 10/7 F stents (P < 0.005). Ureteric flow after endoureterotomy and subsequent stent removal was similar for buoy stents and standard 7 F stents. None of the stents refluxed. There was no difference between stents in removal force, weight change or incidence of hydronephrosis. At 1 and 12 weeks, buoy stents tended to produce lower histopathological alteration scores than control stents, especially at the VUJ (phase I, 2.0 vs 3.9, P = 0.092; phase II, 0.6 vs 1.7, P = 0.18).

CONCLUSIONS

The novel buoy stents are easily placed and removed via the urethra. They can cause less VUJ inflammation than standard stents while allowing for adequate ureteric flow and healing after proximal endoureterotomy.     

Biocompatibility,encrustation and biodegradation of ofloxacine and silver nitrate coated poly-L-lactic acid stents in rabbit urethra

The purpose of this study was to evaluate the biocompatibility, encrustation and biodegradation properties of silver nitrate and ofloxacine blended caprolactone-L-lactide copolymer coated self-reinforced poly-L-lactic acid (SR-PLLA) urospirals in situ in the male rabbit urethra. SR-PLLA urospirals coated with 10% by weight silver nitrate or 5% by weight ofloxacine blended copolymer or pure copolymer were inserted into the posterior urethra of 18 male rabbits. No prophylactic antibiotics were given. The animals were sacrificed 1 or 6 months after insertion. Urethral tissue reactions were histologically scored semiquantitavely and the appearence of the stents assessed using scanning electron microscopy. The biodegradation time of SR-PLLA stents was remarkably reduced by the caprolactone coating. Silver nitrate and ofloxacine blended copolymer coated urospirals caused less tissue reaction than urospirals with a pure copolymer coating. Silver nitrate coating effectively prevented biofilm formation and stent encrustation. Silver nitrate and ofloxacine blended copolymer coated SR-PLLA urospirals had good biocompatibility properties in rabbit urethra. In particular, coating with silver nitrate may provide possibilities of preventing bacterial adhesion to bioabsorbable stents.     

Safer urethral catheters: how study of catheter balloon pressure and force can guide design

What's known on the subject? and What does the study add? The urethal catheter is a ubiquitous device that has not been modified or improved for safety in the last 20 years, although it can be associated with significant patient harm. This study utilizes force and pressure measurements of the urethral catheter in order to aid in future safety modifications.

OBJECTIVES

• ? To better define urethral catheter balloon pressures and extraction forces during traumatic placement and removal of urethral catheters.
• ? To help guide design for safer urethral catheters.

MATERIALS AND METHODS

• ? Measurements of balloon pressure were made upon filling within the urethra vs the bladder.
• ? Extraction forces were measured upon removal of a catheter with a filled balloon from the bladder.
• ? Models for the bladder and urethra included an ex vivo model (funnel, ‘bladder’, attached to a 30 F tube, ‘urethra’) and fresh human male cadavers.
• ? The mean (sem ) balloon pressures and extraction forces were calculated.

RESULTS

• ? In the ex vivo model, the mean (sem ) pressures upon filling the balloon with 10 mL were on average three‐times higher within the ex vivo‘urethra’ (177 [6] kPa) vs ‘bladder’ (59 [2] kPa) across multiple catheter types.
• ? In the human cadaver, the mean balloon pressure was 1.9‐times higher within the urethra (139 [11] kPa) vs bladder (68 [4] kPa).
• ? Balloon pressure increased non‐linearly during intraurethral filling of both models, resulting in either balloon rupture (silicone catheters) or ‘ballooning’ of the neck of the balloon filling port (latex catheters).
• ? Removal of a filled balloon per the ex vivo model ‘urethra’ and cadaveric urethra, similarly required increasing force with greater balloon fill volumes (e.g. 9.34 [0.44] N for 5 mL vs 41.37 [8.01] N for 10 mL balloon volume).

CONCLUSIONS

• ? Iatrogenic complications from improper urethral catheter use is common.
• ? Catheter balloon pressures and manual extraction forces associated with urethral injury are significantly greater than those found with normal use.
• ? The differences in pressure and force may be incorporated into a safer urethral catheter design, which may significantly reduce iatrogenic urethral injury associated with catheterization.

     

Long-term results of permanent urethral stent Memotherm implantation in the management of recurrent bulbar urethral stenosis

Study Type – Therapy (case series) Level of Evidence 4 What’s known on the subject? and What does the study add? Milroy reported 84% success at a mean of 4.5 years follow‐up by usage of a permanently implantable “urolume” spent in 1993. Memotherm was developed later, especially for urologic use. Our study is one of the largest in this urea, with a high number of patients and a long follow‐up period.

OBJECTIVE

? To evaluate the effectiveness and long‐term results of permanent urethral stent (Memotherm) implantation in the treatment of recurrent bulbar urethral stricture.

PATIENTS AND METHODS

? In all, 47 patients with a history of previous unsuccessful treatment for bulbar urethral stricture were treated using Memotherm bulbar urethral stents between 1998 and 2002. ? Long‐term follow‐up data was analysed and discussed.

RESULTS

? At the end of the 7‐year period 37 of 47 patients (78.7%) had been treated successfully. ? Post‐micturition dribbling incontinence lasting up to 3 months after stent placement occurred in 32 (68.1%) patients, but this was reduced to only seven patients (14.9%) by the 7‐year follow‐up. ? There was stress incontinence of various severities in nine (19.2%) patients at the 1‐year follow‐up. These patients were those who had stenosed urethral segments adjacent to the external sphincter. At the long‐term follow‐up <10% of the patients had stress incontinence complaints.

CONCLUSION

? Memotherm is a good treatment option in patients with recurrent bulbar urethral stricture of any cause.     

Urethral Reconstruction Using Bone Marrow Mesenchymal Stem Cell– and Smooth Muscle Cell–Seeded Bladder Acellular Matrix

Background

Congenital or acquired abnormalities may lead to a urethral defect that often requires surgical reconstruction. The traditional methods often lead to complications, including urethrocutaneous fistulae and strictures. In this study, we proposed to construct a tissue-engineered sheet graft (TESG) using a bone marrow mesenchymal stem cell (BMSC)– and smooth muscle cell (SMC)–seeded bladder acellular matrix (BAM) for urethral reconstruction.

Methods

Rabbit BMSCs and SMCs were isolated, expanded, and identified in vitro before seeding into BAM as the experimental group, whereas BAM-only was the control group. The graft was used to construct TESG for implantation into the rabbit omentum for 2 weeks before urethral reconstruction. We divided 24 male rabbits into four experimental groups six each, and six other were the control group. Histological analysis was performed at 2 weeks, 4 weeks, 8 weeks, and 16 weeks postoperatively. Retrograde urethrography was performed at 16 weeks postoperatively.

Results

All experimental rabbits survived to they were humanly killed. At 8 weeks, there was no difference between the graft and the normal urethra with no severe shrinkage. At 8 and 16 weeks after TESG grafting in vivo, multilayer urothelium covered the graft, neovascularization was visible within the center of TESG, and organized smooth muscle bundles were present. Retrograde urethrography failed to demonstrate diverticula formation or urethral stricture. Three control rabbits died within 4 weeks postoperatively. Autopsy showed their urethras to be almost completely blocked whereas another three hosts displays urethral strictures.

Conclusion

A TESG was constructed using a BMSC- and SMC-seeded BAM for urethral reconstruction.     

Evaluation of stretched electrospun silk fibroin matrices seeded with urothelial cells for urethra reconstruction

Background

We investigated the feasibility of urethral reconstruction using stretched electrospun silk fibroin matrices.

Materials and methods

A novel electrospun silk fibroin matrix was prepared. The structure of the material was assessed by scanning electron microscopy and a porosity test. Canine urothelial cells were isolated, expanded, and seeded onto the material for 1 wk to obtain a tissue-engineered graft. The tissue-engineered graft was assessed using hematoxylin and eosin staining and scanning electron microscopy. A dorsal urethral mucosal defect was created in nine female beagle dogs. In the experimental group, tissue-engineered mucosa was used to repair urethra mucosa defects in six dogs. No substitute was used in the three dogs of the control group. Retrograde urethrography was performed at 1, 2, and 6 mo after grafting. The urethral grafts were analyzed grossly and histologically.

Results

Scanning electron microscope and a porosity test revealed that the material had a three-dimensional porous structure. Urothelial cells grew on the material and showed good biocompatibility with the stretched silk fibroin matrices. Canines implanted with tissue-engineered mucosa voided without difficulty. Retrograde urethrography revealed no signs of stricture. Histologic staining showed gradual epithelial cell development and stratified epithelial layers at 1, 2, and 6 mo. The canines in the control group showed difficulty in voiding. Retrograde urethrography showed urethra stricture. Histologic staining showed that no or only one layer of epithelial cells developed. A severe inflammatory reaction was also observed in the control group.

Conclusions

Stretched electrospun silk fibroin matrices have good biocompatibility with urothelial cells, which could prove to be a potential material for use in urethra reconstruction.