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Biomedical subjects

A R Mundy

Publications and source records attributed to A R Mundy.

At least 55 records · Page 3Linked to original sources
PubMed1999

Changing practice in anterior urethroplasty.

OBJECTIVE: To describe our experience of penile urethral repair and reconstruction, cataloguing the change in practice from one-stage flap to two-stage free graft procedures for anterior urethroplasty. PATIENTS AND METHODS: Between January 1992 and December 1996, 79 patients underwent anterior urethroplasty. Of the 45 one-stage bulbar patch urethroplasties, 37 (76%) used buccal mucosal free grafts rather than flaps. Of the 34 penile urethroplasties, 26 (82%) (including all of the circumferential reconstructions) were two-stage procedures. RESULTS: Buccal mucosal free grafts were at least as good as local skin flaps for patch urethroplasty and two-stage repairs gave much better results than one-stage repairs for total circumferential reconstruction of the penile urethra. CONCLUSIONS: For a patch urethroplasty of an uncomplicated stricture in the bulbar urethra, buccal mucosal free grafts are now the material of choice. For a patch urethroplasty of an uncomplicated stricture in the penile urethra the Orandi procedure remains the 'gold standard'. For a circumferential repair of the urethra, particularly the penile urethra, a two-stage repair using a free graft gives better results than a one-stage repair using a flap.

Follow-Up Studies↗
PubMed1999

Neuromodulation by implant for treating lower urinary tract symptoms and dysfunction.

OBJECTIVE: Patients with irritative micturition complaints, pelvic pain, involuntary urine loss or urinary retention are sometimes difficult to treat. The advent of direct sacral nerve stimulation offers a therapeutic alternative if conservative measures fail and surgery is considered. This paper reviews therapeutic neuromodulation by implant for treating lower urinary tract symptoms and dysfunction. METHODS: The international literature is reviewed on topics such as the physiological basis of neuromodulation, techniques of acute testing and chronic implantation, and clinical results. Future developments and ways for possible improvement are discussed. RESULTS: The mode of action of neuromodulation is probably through restoring the correct balance between excitatory and inhibitory impulses from and to the pelvic organs at a sacral and supra-sacral level. Depending on the predefined success criteria, average success rates of definitive implants vary from 50 to 70%. From the data it seems that patients with urge incontinence and urinary retention are the best candidates for neuromodulation. In the literature the lack of standardisation of selection criteria, stimulation parameters and definitions of success is striking. CONCLUSIONS: Neuromodulation by implant is a useful therapeutic alternative. It should at least be considered in patients with therapy-resistant urge incontinence and urinary retention before proceeding to surgery. Issues such as underlying physiology, methodological standardisation, technical improvements, and patient selection must be addressed in future research.

Animals↗
PubMed1999

Continent urinary diversion using the Mainz-type ureterosigmoidostomy--a valuable salvage procedure.

OBJECTIVES: To review the indications and outcome of patients undergoing a Mainz-type ureterosigmoidostomy. PATIENTS AND METHODS: Fourteen patients who had lost or were about to lose their urethra and sphincter mechanism underwent this operation to provide a continent urinary diversion. Patients had a minimum follow-up of 2 years. RESULTS: There were no significant postoperative complications. Three patients have died from recurrent malignant disease. All patients were continent. CONCLUSION: The Mainz-type ureterosigmoidostomy is a useful technique in situations where orthotopic reconstruction is not possible. Incontinence and reflux do not occur with this detubularized pouch.

Adult↗
PubMed1999

A computer generated interactive transurethral prostatic resection simulator.

PURPOSE: We developed a computer generated model of the prostate gland and an interactive simulator for use in training urologists in transurethral resection of the prostate. MATERIALS AND METHODS: Software was developed on a standard personal computer which allowed images of the lumen of the prostatic urethra and resectoscope loop to be generated and interacted with using a magnetic position sensor input device attached to a dummy resectoscope. RESULTS: An anatomically accurate computer model of the prostate was generated at low cost which permitted user interaction and which simulated key elements of transurethral prostatic resection. CONCLUSIONS: Although not a substitute for learning transurethral prostatic resection on patients, the simulator enabled the user to become familiar with the technique of transurethral prostatic resection in the absence of time constraints and without risk to patients. The simulator may become an important tool in training and assessing surgeon competency, and may reduce the costs of training. Further development is needed to refine the transurethral prostatic resection simulator and expand its surgical range.

Computer Simulation↗
PubMed1999

A quantitative study of atropine-resistant contractile responses in human detrusor smooth muscle, from stable, unstable and obstructed bladders.

PURPOSE: The objective of the study was to quantify in vitro the magnitude of atropine-resistant contractions using human detrusor samples and to determine the cellular processes underlying these contractions. MATERIALS AND METHODS: Isometric contractile responses were measured in isolated strips of human detrusor muscle obtained from patients with i) stable, ii) unstable or iii) obstructed bladders. Preparations were electrically stimulated or exposed to carbachol and ATP in the superfusate. RESULTS: Force-frequency curves were shifted to the right in samples from unstable and obstructed bladders. These same tissue groups also showed significant atropine-resistant contractions which were abolished by the neurotoxin TTX, or the non-hydrolysable ATP analog, alpha,beta-methylene ATP, suggesting that these contractions were mediated by neurally released ATP. Sub-division of the patient group with unstable bladders demonstrated that those with neuropathic instability did not show atropine-resistance, whereas those with idiopathic instability or secondary instability after obstruction did show atropine-resistant contractions. The potency of carbachol in generating a contracture was significantly greater than ATP (mean EC50 0.65 microM and 151 microM respectively) however, for each agonist there was no difference in potency between the three patient groups. Direct muscle excitability was similar in all three patient groups. CONCLUSIONS: It is concluded that purinergic, atropine-resistant contractions are present in some types of dysfunctional bladder, and these are not caused by a differential sensitivity of the muscle to ATP and cholinergic agonists.

Adenosine Triphosphate↗
PubMed1999

A comparison of the mode of action of ATP and carbachol on isolated human detrusor smooth muscle.

PURPOSE: The objectives of the study were: i) to examine the ability of carbachol and ATP to raise intracellular [Ca2+] in isolated detrusor myocytes; ii) to determine the origin of the intracellular Ca2+ and iii) to address the question of whether the appearance of purinergic contractions in detrusor from unstable and obstructed human bladders is reflected in the sensitivity of the cell to the two agonists. MATERIALS AND METHODS: Intracellular Ca2+ transients generated by extracellular ATP and carbachol were recorded from isolated human detrusor myocytes. Cells were dissociated by collagenase disruption of the biopsy. Intracellular Ca2+ was measured by epifluorescence microscopy using Fura-2 and electrophysiological recordings were made with patch electrodes. RESULTS: In cells from stable bladder biopsies the half-maximal concentrations (EC50) for ATP and carbachol to generate Ca2+ transients were 0.10 and 0.25 microM respectively. With cells from unstable bladders the EC50 values for both agonists and the magnitude of the Ca2+ transients were not significantly different from those obtained in cells from normal bladders. The transient in ATP was preceded by a transient depolarisation generated by a large inward current. The carbachol-Ca2+ transient was independent of changes to membrane potential, except in a subset of cells where complex membrane potential changes followed the rise of intracellular Ca2+. The ATP-Ca2+ transient was partially abolished by nicardipine and completely abolished by zero-Ca solutions, the carbachol-Ca2+ transient was unaffected by nicardipine and less completely attenuated by zero-Ca solutions. Prior exposure to caffeine suggested that the carbachol-Ca2+ transient, but not the ATP-Ca2+ transient, originated from intracellular stores. CONCLUSIONS: It is concluded that both agonists are equipotent in increasing intracellular Ca2+, but by different routes. The generation of purinergic contractions in detrusor from unstable bladder is not due to altered sensitivities of the detrusor myocyte to ATP or cholinergic agonists.

Adenosine Triphosphate↗
PubMed1999

Measurement of intercellular electrical coupling in guinea-pig detrusor smooth muscle.

PURPOSE: The electrical impedance of detrusor smooth muscle strips to alternating current has been measured to calculate the resistance of the intracellular pathway, in particular gap junction resistance. Values have been compared with myocardium, which is electrically well-coupled. MATERIALS AND METHODS: Alternating current was passed along the intracellular pathway of muscle strips by creating a high extracellular resistance around the preparation. The data were analyzed in terms of an equivalent circuit consisting of an intracellular and extracellular pathway. RESULTS: Intracellular resistance was divided into two series components, a cytoplasmic resistance and a gap junction resistance. Detrusor intracellular resistance was about three times that of myocardium. The greater value was attributed to a larger gap-junction resistance. Superfusion of detrusor strips with an isosmotic solution of 50% sucrose, 50% Tyrode's increased both cytoplasm and gap junction resistances. CONCLUSIONS: Gap-junction resistance is larger in detrusor compared with myocardium. However, significant electrical current can still pass between adjacent detrusor cells. Calculation of the space constant however shows that functionally detrusor is electrically well-coupled because of the high membrane resistance. The functional consequences of these findings are discussed.

Animals↗
PubMed1998

Transperineal bulbo-prostatic anastomotic urethroplasty.

Transperineal bulbo-prostatic anastomotic urethroplasty is the procedure of choice for the treatment of pelvic-fracture urethral distraction defects. Surgery is usually performed at 3-6 months after the injury. Endoscopic urethroplasty may prove to be an alternative if long-term follow-up confirms the initial enthusiasm for the procedure. Alternative urethroplasty techniques have not proved appropriate in long-term follow-up. The procedure depends on a progressive series of steps to capitalise on the elastisity of the urethra and then straighten out the natural curve of bulbar urethra. A retropubic or (truly) transpubic approach is rarely necessary except for complicated problems. The restricture rate is approximately 10% and is generally associated with poor vascularity. Other complications are generally the complications of the original injury rather than of the procedure itself.

Anastomosis, Surgical↗
PubMed1998

Early experience with the use of buccal mucosa for substitution urethroplasty.

OBJECTIVE: To evaluate the early results of anterior urethroplasty using a one-stage free graft with buccal mucosa. PATIENTS AND METHOD: Thirty-nine patients (aged 23-59 years) underwent a one-stage urethroplasty using buccal mucosa, 28 as a patch and 11 as tube grafts. All patients were evaluated by post-operative urethrography at 6 months and were followed using urinary flow rates and symptoms for 2-5 years. RESULT: There was one recurrent stricture (3%) in the group with a patch urethroplasty but five of the 11 patients with tube grafts had a recurrent stricture. CONCLUSION: The early results using buccal mucosa for patch urethroplasty are encouraging. Although the results from tube grafts are poor, they are similar to those from other methods of single-stage urethroplasty.

Adult↗
PubMed1998

Urethroplasty for balanitis xerotica obliterans.

OBJECTIVE: To review the results of different methods of urethroplasty for anterior urethral strictures caused by balanitis xerotica obliterans (BXO). PATIENTS AND METHODS: Twenty-eight patients underwent urethroplasty for BXO; 12 had a one-stage pedicled penile skin-flap urethroplasty and 16 excision and a two-stage free-graft urethroplasty using nongenital skin. RESULTS: The treatment failed in all patients undergoing a one-stage pedicle penile skin urethroplasty because the disease recurred with BXO, whereas the treatment failed in only one patient using a two-stage free graft procedure. CONCLUSION: A two-stage free-graft urethroplasty using nongenital skin is recommended for anterior urethral strictures caused by BXO.

Balanitis↗
PubMed1998

'Nerve-sparing' cystectomy and substitution cystoplasty in patients of either sex: limitations and techniques.

OBJECTIVES: To determine the limitations of cystectomy and orthotopic substitution cystoplasty in men and women with bladder cancer. PATIENTS AND METHODS: Cystectomy and orthotopic substitution cystoplasty were carried out in 79 patients (mean age 60 years, range 31-74, including eight women) who were followed for a mean of 7 years (range 1-13) to evaluate continence, potency and survival. RESULTS: Overall, 80% of the patients were continent without further treatment and 55% of the men who were potent before surgery remained so afterward. The best results were obtained with retrograde cystectomy in both sexes and are only achievable in women in this way. Continence was achieved more easily in women than in men, although pathological delineation of the tumour preoperatively and technical considerations per-operatively make both the selection and the procedure more demanding in women than in men. CONCLUSIONS: Cystectomy and orthotopic substitution cystoplasty is possible in patients of either sex and should be offered to all patients as an alternative to ileal conduit urinary diversion, unless preoperative assessment suggests that the urethra must be removed with the bladder, which is rare in men and uncommon in women. In such patients, a continent diversion may be the preferred option.

Adult↗
PubMed1998

Long-term results of augmentation cystoplasty.

OBJECTIVES: To present the long-term results and complications of augmentation cystoplasty. METHODS: 267 patients underwent augmentation cystoplasty with a minimum follow-up of 3 years. RESULTS: Patients with neuropathic bladders had a 78% continence rate with cystoplasty alone increasing to 90% with the addition of an artificial urinary sphincter. Patients undergoing cystoplasty for detrusor instability had a 93% continence rate. The complications of this procedure include bacteriuria, absorption disorders, stones and the potential risk of malignancy. DISCUSSION: The overall results of continence with augmentation cystoplasty are excellent. Long-term follow-up is required to ensure prompt treatment of the complications.

Adolescent↗