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P A Merguerian

Publications and source records attributed to P A Merguerian.

At least 19 recordsLinked to original sources
PubMed2002

22 week assessment of bladder acellular matrix as a bladder augmentation material in a porcine model.

Previous studies on the reconstruction of porcine bladder using bladder acellular matrix allograft (BAMA) have indicated positive preliminary results with respect to graft shrinkage and cellular repopulation. The current study was conducted to investigate the feasibility of using BAMA in a similar model of bladder reconstruction out to longer time frames (22 weeks). At predetermined time points, the macroscopic, histological and mechanical properties of explanted native and BAMA tissues were evaluated and compared. Macroscopically, contracture of the BAMA was observed. The peripheral regions of the grafts experienced extensive cellular repopulation. Towards the centre however, all grafts were consistently devoid of organized smooth muscle bundles and a well-developed urothelium. An alteration in both the amount and organization of collagen was also observed within this region. Significant differences (p < 0.05) in the rupture strain and the elastic modulus of the BAMA compared to native bladder tissue appear to correlate with macroscopic graft contracture as well as the fibroproliferative tissue response of the matrix.

Animals↗
PubMed2001

A population based analysis of continence outcomes and bladder exstrophy.

PURPOSE: Whereas the literature on bladder exstrophy is replete with outcomes of specific continence surgical procedures in highly select patients, there are no data on the outcomes related to continence for a complete exstrophy population, which is more comprehensive with respect to a variety of surgical procedures performed to achieve continence. To provide urologists and patients with an overview of potential continence outcomes devoid of any selection bias, we report on a comprehensive exstrophy population, focusing on the various procedures required for urinary continence. MATERIALS AND METHODS: We reviewed the charts of all patients with bladder and cloacal exstrophy who underwent a staged repair to achieve urinary continence at a single institution between 1988 and 1998. Urinary continence was then correlated to the types of surgical procedures, and subgroup analysis for predictors of urinary continence was performed. The type of bladder neck reconstruction allowed subgrouping cases into group 1-bladder neck reconstruction only, group 2-bladder neck reconstruction with augmentation and/or appendicovesicostomy and group 3-bladder neck closure. RESULTS: Of the 43 patients identified 26 were male, 4 had cloacal exstrophy and 3 had complex exstrophy variants with ectopic hindgut and spina bifida. Groups 1 to 3 comprised 9, 15 and 19 patients with urinary continence rates of 56%, 67% and 100%, respectively. The age at which patients became continent was delayed in groups 2 and 3 (8.2 and 8.7 years, respectively) compared to group 1 (4.8). Of all the potential variants measured gender was the strongest predictor of continence with 94% of females versus 69% of males achieving it. Of the males those with (57%) compared to those without (83%) a history of bladder neck stenosis or paraexstrophy flaps had worse continence. Repeat bladder neck reconstruction was only successful in 23% of patients. CONCLUSIONS: All patients can be rendered continent but many may achieve this successful outcome by other procedures following initial bladder neck reconstruction. When managing failed bladder neck reconstruction, the type of surgical repair chosen may need to address the need for enhanced bladder storage and the issue of potential bladder augmentation. The advances made in the treatment of the epispadiac urethra may now facilitate clean intermittent catheterization. Earlier recognition of the need for adjunctive storage procedures in addition to bladder neck reconstruction may facilitate the timing of providing enhanced continence, independence and self-esteem, and do so with fewer operative procedures. We speculate that the current complete urethral and bladder repair in newborns will add further to the storage functions of the native bladder tissues and improve the potential of achieving more effective bladder outlet control.

Bladder Exstrophy↗
PubMed2001

Pediatric genitourinary tumors.

Each year advances are made in the evaluation and management of genitourinary tumors in children. There is increased understanding of molecular and genetic processes in tumorigenesis. In addition, knowledge concerning the current treatment modalities is increasing, thus allowing us to tailor treatments in order to decrease long-term complications. In this article, we review this past year's literature regarding pediatric genitourinary tumors with emphasis on Wilms tumor, rhabdomyosarcoma, and testicular tumors.

Adolescent↗
PubMed2000

Outcomes of primary valve ablation versus urinary tract diversion in patients with posterior urethral valves.

OBJECTIVES: Although valve ablation is the treatment of choice for patients with posterior urethral valves, debate continues as to the role of urinary diversion. We sought to retrospectively compare the clinical and radiologic outcomes between valve ablation and urinary diversion for patients with posterior urethral valves. METHODS: We retrospectively reviewed the records of 50 consecutive patients with posterior urethral valves since January 1995. On the basis of the initial renal function and radiologic findings, patients were divided into three groups: group 1, normal renal function and radiologically normal upper tracts; group 2, normal renal function with hydronephrosis and/or reflux; and group 3, azotemia with hydronephrosis or reflux. RESULTS: All 22 patients in group 1 were treated with valve ablation. After a mean follow-up of 32 months, these children had normal renal function and no evidence of upper tract deterioration. All 13 patients in group 2 were also treated with valve ablation. The radiologic abnormalities (hydronephrosis, reflux) resolved in 50% of cases, with an average follow-up of 28 months. Of the 15 patients in group 3, 7 underwent valve ablation and 8 underwent urinary diversion. Urinary diversion was performed in patients with renal deterioration and severe hydronephrosis and/or high-grade reflux. Renal function returned to normal in all patients who underwent valve ablation except one; renal function returned to normal in only 3 of 8 patients who underwent urinary diversion. Radiologically, the severity of the hydronephrosis and reflux was downgraded in patients who underwent valve ablation but not in the diverted group. CONCLUSIONS: Valve ablation is the mainstay of treatment for patients with posterior urethral valves. Prenatal and postnatal factors, such as renal dysplasia and urinary tract infection, respectively, rather than the posterior valve treatment dictate the long-term renal and radiologic outcomes.

Adolescent↗
PubMed2000

Acellular bladder matrix allografts in the regeneration of functional bladders: evaluation of large-segment (> 24 cm) substitution in a porcine model.

OBJECTIVES: To evaluate the use of a large-segment (> 24 cm2) bladder substitution with porcine bladder acellular matrix allograft (BAMA) in a large animal model. Materials and methods Bladders were harvested from pigs at the time of necropsy and subjected to detergent and enzymatic extractions to render them acellular. The BAMA produced had the surgical handling and suture-retaining properties of normal bladder tissue. Six pigs had BAMA segments implanted under general anaesthesia, through a low midline abdominal incision and after partial cystectomy. The defect was repaired with a BAMA patch (mean size 43.88 cm2, range 12-72), with no urinary diversion. Two animals each were then killed at 9, 16 and 30 days and the bladders explanted. The native bladder and BAMA patch were analysed morphometrically to evaluate cellular re-population and matrix re-organization. RESULTS: All animals survived surgery; there were no urinary leaks and no stones detected in any of the bladders. At 9 days there was a diffuse infiltration with acute inflammatory cells, but no areas of necrosis. There were isolated areas of smooth muscle cell (SMC) infiltration of the BAMA. At 16 days the luminal surface was lined with a single layer of urothelium, there was stromal infiltration with disorganized SMC and angiogenesis, with mature vessels in the BAMA patch. At 30 days the urothelium was multilayered with organizing groups of SMCs and angiogenesis. The highest cell density was at the periphery of the repopulated BAMA patch, decreasing towards the centre. CONCLUSIONS: The implantation of large patches of BAMA is technically feasible and may prove to be a viable surgical alternative to bladder augmentation with intestinal segments. The advantages of BAMA include the potential for complete and functional regeneration of a bladder substitute. This model provides a tool with which to obtain a better understanding of the cellular and molecular aspects of matrix re-population.

Animals↗
PubMed2000

Pediatric genitourinary tumors.

Advances in our knowledge of pediatric genitourinary tumors are being made at both the basic science and clinical levels. The molecular mechanisms underlying these pediatric malignancies are being uncovered and will aid in uncovering novel treatments. Because of the high success rate in treating these tumors, treatment options are being modified to decrease both short- and long-term morbidity, while maintaining the improved survival.

Adolescent↗
PubMed2000

Regeneration of functional bladder substitutes using large segment acellular matrix allografts in a porcine model.

PURPOSE: We previously reported on the short-term (4 weeks) morphometric analysis of a large bladder acellular matrix allograft used as a bladder bioprosthesis (average size 24 cm.2). We demonstrated cellular repopulation through the entire thickness of the graft. We now present the long-term (12 weeks) morphometric results of graft regenerated porcine bladders using segments measuring an average of 40 cm.2. MATERIALS AND METHODS: Bladders harvested from pigs were subjected to detergent and enzymatic extractions to render them acellular. Partial cystectomy was performed in 21 pigs and the defect was repaired with a bladder acellular matrix allograft (average size 40.52 cm.2). Of the animals 8 were sacrificed at 1, 2 and 4 weeks and 13 were sacrificed at 8 and 12 weeks. To evaluate cellular repopulation and matrix reorganization the native bladder and graft were analyzed using standard histological and immunofluorescent techniques. To evaluate for calcium deposits in the grafts a radiological evaluation of the graft was performed after explantation. RESULTS: All animals survived the surgical procedure and there were no significant urinary leaks. No stones were noted in any of the bladders. At 1 week there was a diffuse infiltration with acute inflammatory cells. At 2 weeks the luminal surface of the graft was lined with a single layer of urothelium, and there was stromal infiltration with unorganized smooth muscle cells and angiogenesis. At 4 weeks the urothelium was multilayered with organizing groups of smooth muscle cells and angiogenesis. At 8 and 12 weeks there was repopulation throughout the bladder acellular matrix allograft implant with all native cellular components participating. CONCLUSIONS: We present evidence that large patch bladder acellular matrix allograft implantation is technically feasible and may prove to be a viable surgical alternative to bladder augmentation with intestinal segments. Its advantages may include the potential for complete and functional regeneration of a bladder substitute.

Animals↗
PubMed2000

The dysfunctional voiding scoring system: quantitative standardization of dysfunctional voiding symptoms in children.

PURPOSE: Academic research on pediatric nonneurogenic voiding dysfunction has long been hampered by the lack of a standardized reporting system for voiding symptoms. We evaluated the performance of a newly devised, objective instrument to quantify or grade the severity of abnormal voiding behaviors of children. MATERIALS AND METHODS: There were 10 voiding dysfunction parameters that were assigned scores of 0 to 3 according to prevalence, and possible total scores ranged from 0 to 30. The Dysfunctional Voiding Symptom Score was completed by 2 groups of patients. Group 1 consisted of patients 3 to 10 years old presenting to the pediatric urology clinic with a history of diurnal urinary incontinence, urinary tract infections or abnormal voiding habits. Group 2 consisted of an age matched cohort with no history of urological complaints presenting to hospital clinics outside of urology. Patients diagnosed with organic or anatomical disease, such as posterior urethral valves or meningomyelocele, were excluded from our analysis. RESULTS: Group 1 consisted of 104 patients (female-to-male ratio 4:1) with a median symptom score of 14 and group 2 consisted of 54 patients (female-to-male ratio 1.3:1) with a median score of 4. The dysfunctional voiding odds ratio was 2.93 for females compared to that of males. Using receiver operating characteristics the optimum cutoff score was 6.026 (sensitivity 92.77% and specificity 87.09%) for females and 9.02 (sensitivity of 80.95% and specificity of 91. 30%) for males. In addition, we found certain questions to be more reflective than others of dysfunctional voiding symptoms in our population. CONCLUSIONS: The Dysfunctional Voiding Symptom Score appears to provide accurate and objective, that is, numerical, grading of voiding behaviors of children. Comparative research studies of dysfunctional voiding diagnosis and response to therapy as well as objective measurements of treatment efficacy and outcomes analysis should be aided greatly by this system.

Child↗
PubMed2000

Are postoperative studies justified after extravescial ureteral reimplantation?

PURPOSE: We evaluated the usefulness of postoperative imaging studies after extravesical ureteroneocystostomy and identified patient subsets in which these studies are necessary. MATERIALS AND METHODS: Records of 438 patients who had undergone extravesical ureteroneocystostomy from 1991 to 1997 were reviewed retrospectively. Study inclusion criterion was primary reflux with at least 1 year of postoperative followup. Grades I to III reflux were defined as low, and grades IV and V were defined as high. All patients were on prophylactic antibiotics. Evaluation included ultrasound and a voiding cystourethrogram 3 months postoperatively, and if reflux persisted the studies were repeated at 12 months. RESULTS: A total of 438 patients (723 renal units) underwent extravesical ureteral reimplantation. At 3 months the procedure was successful in 93.2% of ureters (91.3% patients), and at 12 months the success rate increased to 97.9% of ureters (95.4% patients). There were 49 renal units in 38 cases that were refluxing at 3 months, 11 of which were contralateral. At 12 months reflux resolved spontaneously in 20 of 38 ipsilateral and 8 of 11 contralateral ureters. Of the remaining 18 ipsilateral units reflux was high grade preoperatively in 12 and persisted postoperatively in 4. There was a statistically significant difference in the success rate at 1 year between high (94%) versus low (99%) grade reflux (p = 0.007). Age and preoperative bladder function did not significantly affect the success rates but males had a lower success rate. Hydronephrosis was noted in 7.2% of ureters at 6 weeks and in only 0.005% at 12 months. CONCLUSIONS: Extravesical reimplantation is successful in treating vesicoureteral reflux. Postoperative voiding cystourethrogram should be reserved for high grade reflux. Limiting these studies will help reduce patient discomfort and the cost of treatment.

Child↗
PubMed2000

Lessons learned from laser tissue soldering and fibrin glue pyeloplasty in an in vivo porcine model.

PURPOSE: We compared sutured pyeloplasty to 2 newer techniques of tissue anastomosis, including laser soldered pyeloplasty using a diode laser with 50% albumin solder mixed with indocyanine green and fibrin glue. MATERIALS AND METHODS: We performed 53 pyeloplasties in 50 pigs using suture, laser or fibrin glue. In the immediate group anastomotic leak pressure was measured immediately postoperatively, and then animals were euthanized. At 1, 3 and 4 weeks postoperatively a pressure flow study at 10 cc per minute in cm. H2O was performed, and tissue was sent for histological and collagen content analysis. RESULTS: In the immediate studies laser soldering achieved a significantly higher mean anastomotic leak pressure (50.5 +/- 15.1 cm. H2O) than sutured (17.3 +/- 5.4) or fibrin glued (3.5 +/- 1.5) repairs. In the 1, 2 and 4-week studies animals in the sutured pyeloplasty group had no complications, and all pressure flow studies except 1 were normal. However, in the laser soldered groups we observed 8 urinomas in 19 animals, and most occurred during the first part of our study. This complication was prevented by stopping urine flow at the anastomotic site at laser irradiation and by improving application of the solder. Of the 11 animals in which pressure flow studies were performed only 2 were obstructed. Of the 7 chronic fibrin glue group 4 animals had urinomas and 2 had unobstructed pressure flow studies. Histological studies and immunohistochemical staining for collagen showed no differences in collagen distribution among the 3 procedures. CONCLUSIONS: Laser soldering and fibrin glue pyeloplasties are not superior in the long-term compared to sutured pyeloplasty. Fibrin glue in our animal model had the highest failure rate. Further improvements in the technical aspect of laser tissue welding need to be made to benefit from its theoretical advantages in minimally invasive surgery.

Anastomosis, Surgical↗
PubMed2000

The use of magnetic resonance imaging in the diagnosis and followup of pediatric pelvic rhabdomyosarcoma.

PURPOSE: Previous radiological descriptions of pelvic rhabdomyosarcoma emphasized ultrasonography and computerized tomography (CT). Few reports are available on the use of magnetic resonance imaging (MRI) for diagnosing and following pelvic rhabdomyosarcoma. We retrospectively compared MRI to CT for diagnosing and following children with pelvic rhabdomyosarcoma. MATERIALS AND METHODS: We treated 4 boys and 3 girls for pelvic rhabdomyosarcoma. Initial and followup evaluations included pelvic CT and MRI at intervals determined by treatment and disease status. We retrospectively reviewed the clinical charts and imaging studies of these patients. The initial radiological report was evaluated and then 1 radiologist reviewed all studies. Attention was directed toward identifying lesions revealed by CT or MRI but not by the other modality. RESULTS: MRI detected all lesions shown by CT. On the other hand, MRI detected residual disease in 1 case that was not demonstrated by CT. In 2 other patients MRI was superior to CT for delineating the local extent of disease, especially urethral involvement. CONCLUSIONS: Compared with CT, MRI improves the detection of residual pelvic rhabdomyosarcoma. Tissue planes are well delineated, allowing more accurate assessment of tumor invasion into adjacent structures. MRI is the imaging modality of choice for following pediatric patients with pelvic rhabdomyosarcoma.

Child↗
PubMed1999

Urinary retention after bilateral extravesical ureteral reimplantation: does dissection distal to the ureteral orifice have a role?

PURPOSE: We evaluated the outcome and incidence of urinary retention after bilateral detrusorrhaphy using 2 modifications of the original Lich-Gregoir procedure. MATERIALS AND METHODS: We evaluated the charts of 220 patients who underwent correction of bilateral vesicoureteral reflux using the extravesical approach from January 1991 to December 1997. Inverted Y detrusorrhaphy was performed in 154 patients and the advancing suture modification was done in 66. RESULTS: The success rate using the advancing suture technique was 92.4 and 95.4% at 3 and 12 months, respectively. The Y detrusorrhaphy technique was successful in 91.6 and 97.4% of cases at 3 and 12 months, respectively. The difference in the techniques was not statistically significant. Urinary retention developed in 8.4% of the patients who underwent Y detrusorrhaphy compared to 15.2% of those who underwent the advancing suture technique (not statistically significant). However, patients with grades IV and V reflux, children younger than 3 years and boys had significantly (p <0.05) higher postoperative retention rates of 24.6, 35.6 and 20.3%, respectively, when all 220 patients were considered. CONCLUSIONS: Each modification of the original Lich-Gregoir technique is highly effective for treating bilateral vesicoureteral reflux and each is associated with a low rate of temporary urinary retention. Although there seems to be a lower incidence of retention with the Y detrusorrhaphy technique, this was not statistically significant. Because of the higher incidence of urinary retention in young children, boys and/or patients with high grade reflux, we recommend that physicians consider a longer period of catheterization regardless of the technique chosen.

Child↗
PubMed1999

Utility of SPECT DMSA renal scanning in the evaluation of children with primary vesicoureteral reflux.

OBJECTIVES: DMSA renal scanning is more sensitive than ultrasound in detecting renal parenchymal scars. We proposed to determine the utility of single-photon emission computed tomography (SPECT) dimercaptosuccinic acid (DMSA) renal scanning in children with primary vesicoureteral reflux (VUR). METHODS: During a 24-month period, we evaluated the charts of 368 patients who had undergone SPECT DMSA renal scanning for primary VUR. Patients were divided into three age groups: (a) less than 1 year, (b) between 1 and 5 years, and (c) older than 6 years. Renal scars were deemed severe or focal. The data were analyzed to evaluate the utility of SPECT DMSA scanning in children with primary VUR and to determine the indications for performing SPECT DMSA. We also evaluated the sensitivity of recent renal ultrasound technology in detecting focal and diffuse scars. RESULTS: One hundred twenty-eight patients were younger than 1 year at presentation. These included 24 cases that were detected prenatally. One hundred eighty-five were between the ages of 1 and 5 years, and 55 were 6 years or older. Reflux nephropathy at presentation was found in 99 (26.9%) of 368 patients. DMSA scanning changed the treatment in only 13 patients (3.5%). When scarring was diffuse, ultrasound examination correlated 100% with DMSA scanning; when focal scarring was present, the correlation was poor. CONCLUSIONS: Our results suggest that DMSA scans should be tailored to children who have ultrasound abnormalities, high-grade reflux, or recurrent breakthrough urinary tract infections. These guidelines will result in a substantial cost savings and a significant decrease in radiation exposure.

Child↗
PubMed1999

Pediatric genitourinary tumors.

Advances in our knowledge of pediatric genitourinary tumors are being made at a rapid pace at both the basic science and clinical levels. As the molecular mechanisms underlying these malignancies are being uncovered, treatment options are being modified to decrease morbidity and, ultimately, increase survival. This article reviews the recent literature on Wilms' tumor, rhabdomyosarcoma, and testicular tumors.

Child↗
PubMed1999

Initial experience with endoscopic holmium laser lithotripsy for pediatric urolithiasis.

PURPOSE: Due to the unavailability of suitable pediatric instruments children have not benefited from advances in endoscopic lithotripsy. This limitation may be overcome by the holmium: YAG laser. We evaluated the indications for, and efficacy and complications of holmium:YAG laser lithotripsy. MATERIALS AND METHODS: We retrospectively reviewed all cases of laser lithotripsy. Access to the calculus was antegrade or retrograde. A solid state holmium:YAG laser was used. RESULTS: Eight patients 4 to 14 years old underwent laser lithotripsy during the study period. Average calculous surface area was 357.13 mm.2 (range 14 to 1,645). Five patients required 1 procedure to render them stone-free, while the remaining 3 required multiple procedures. No complications were associated with laser lithotripsy. CONCLUSIONS: The ability of the holmium:YAG laser to pulverize urinary calculi makes it an alternative choice for lithotripsy. In our series all patients are stone-free with stable renal function. The advantages of the holmium:YAG laser are that it may be precisely applied via small fibers, and it pulverizes calculi with minimal scattering of energy and retropulsion of the calculus, decreasing trauma to tissues at the perioperative site. There is also a lower risk of residual fragments, which is associated with a lower incidence of calculous regrowth. Holmium: YAG laser is safe and effective for treating pediatric urolithiasis.

Adolescent↗
PubMed1998

Detrusorrhaphy for repair of unilateral vesicoureteral reflux: report of 76 patients using a modified technique.

OBJECTIVE: To present our results for repair of unilateral vesicoureteral reflux in 76 children using a modified technique of detrusorrhaphy. METHODS: A retrospective chart review was performed for 76 children who underwent repair of unilateral vesicoureteral reflux by a modified technique of detrusorrhaphy. Of the 76 refluxing ureters, 12 were associated with historically refluxing contralateral ureters. In addition, 72/76 were grades II to IV; 4/76 grade V; three had a paraureteral diverticulum; four completely duplicated collecting systems; and two had associated ureteroceles. The surgical technique was modified to preserve both the obliterated umbilical artery and superior vesical pedicle and to minimize trigonal distortion through dissection lateral to the trigone in a direct path to the bladder neck. RESULTS: Seventy-five of 76 ureters were successfully repaired (99%). The remaining ureter showed initial improvement to grade I reflux and spontaneous resolution by 1 year. Obstruction did not occur. Three episodes of "new onset" contralateral vesicoureteral reflux were noted postoperatively. This represents a substantial decrease in incidence (3.9%) when compared with previously reported series (18%). CONCLUSION: Detrusorrhaphy is a reasonable treatment of unilateral vesicoureteral reflux with utility in the full range of anatomic associations. This approach is also associated with a lower incidence of new onset, contralateral reflux when compared with intravesical surgery.

Adolescent↗
PubMed1998

Laparoscopy for the evaluation and management of the nonpalpable testicle.

OBJECTIVE: To assess the usefulness of laparoscopy for the diagnosis and treatment of the nonpalpable testicle and to evaluate the results of laparoscopic orchidopexy. METHODS: We retrospectively reviewed the charts of 91 laparoscopies performed over a period of 4 years. We reviewed the following parameters: findings, complications, patency of the processus vaginalis, appearance of the cord structures, and the success of the different procedures performed for the intra-abdominal testicle. RESULTS: Fourteen patients had bilateral and 77 unilateral nonpalpable testicles. The mean age of the patients was 39.5 +/- 50.8 months. There were three laparoscopic complications (3.2%) one of which was a major bowel laceration. Laparoscopy defined the intra-abdominal anatomy accurately in 90 of the 91 cases Of the 26 intra-abdominal testicles above the ring, a one-stage laparoscopic orchidopexy was performed in five and a single-stage standard orchidopexy in seven. All of these testicles remain viable and are in good position. Eight patients underwent a staged Fowler-Stephens orchidopexy with laparoscopic clipping of the spermatic vessels as the first stage. Of these, a second-stage open orchidopexy was performed in five and a laparoscopic orchidopexy in three. Testicular atrophy occurred in two of the patients who underwent the second-stage open orchidopexy. Three one-stage Fowler-Stephens orchidopexies were performed with testicular atrophy occurring in two of these testicles. Laparoscopic orchiectomy was performed on two patients. CONCLUSIONS: Laparoscopy is a valuable tool in the diagnosis and treatment of the nonpalpable testicle. Laparoscopic orchidopexy may decrease the rate of testicular atrophy since most of these can be performed laparoscopically in one stage, thus preserving the vascular supply.

Adolescent↗