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Hydrodynamic injection creates a local, high-pressure environment to transfect various tissues with plasmid DNA and other substances. Hydrodynamic tail vein injection, for example, is a well-established method by which the liver can be transfected. This manuscript describes an application of hydrodynamic principles by injection of the mouse kidney directly with plasmid DNA for kidney-specific gene expression. Mice are anesthetized and the kidney is exposed by a flank incision followed by a fast injection of a plasmid DNA-containing solution directly into the renal pelvis. The needle is kept in place for ten seconds and the incision site is sutured. The following day, live animal imaging, Western blot, or immunohistochemistry may be used to assay gene expression, or other assays suited to the transgene of choice are used for detection of the protein of interest. Published methods to prolong gene expression include transposon-mediated transgene integration and cyclophosphamide treatment to inhibit the immune response to the transgene.
PURPOSE - Although reported success rates after pediatric pyeloplasty to correct ureteropelvic junction are high, failure may require intervention. We sought to characterize the incidence and timing of secondary procedures after pediatric pyeloplasty using a national employer based insurance database.
MATERIALS AND METHODS - Using the MarketScan® database we identified patients 0 to 18 years old who underwent pyeloplasty from 2007 to 2013 with greater than 3 months of postoperative enrollment. Secondary procedures following the index pyeloplasty were identified by CPT codes and classified as stent/drain, endoscopic, pyeloplasty, nephrectomy or transplant. The risk of undergoing a secondary procedure was ascertained using Cox proportional hazards models adjusting for demographic and clinical characteristics.
RESULTS - We identified 1,976 patients with a mean ± SD followup of 23.9 ± 19.8 months. Overall 226 children (11.4%) had undergone at least 1 post-pyeloplasty procedure. The first procedure was done within 1 year in 87.2% of patients with a mean postoperative interval of 5.9 ± 11.1 months. Stents/drains, endoscopic procedures and pyeloplasties were noted in 116 (5.9%), 34 (1.7%) and 71 patients (3.1%), respectively. Length of stay was associated with undergoing a secondary procedure. Compared with 2 days or less the HR of 3 to 5 and 6 days or greater was 1.65 and 3.94 (p = 0.001 and <0.001, respectively).
CONCLUSIONS - Following pediatric pyeloplasty 1 of 9 patients undergoes at least 1 secondary procedure with the majority performed within the first year. One of 11 patients undergoes intervention more extensive than placement of a single stent or drain, requiring management strategies that generally signify recurrent or persistent obstruction. Estimates of pyeloplasty success in this national data set are lower than in other published series.
Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.
PURPOSE - Radiographic followup after pyeloplasty for the correction of ureteropelvic junction obstruction is not well defined in children. We characterize trends in frequency and modality of postoperative imaging after open and minimally invasive pediatric pyeloplasty.
MATERIALS AND METHODS - Using the MarketScan® database, we identified patients 0 to 18 years old undergoing pyeloplasty between 2007 and 2013. Followup imaging was classified as functional (diuretic renography, excretory urography) or nonfunctional (ultrasound, computerized tomography, magnetic resonance imaging). We excluded patients with less than 24 months of postoperative enrollment in MarketScan. Multivariate logistic regression was performed to determine associations between demographic variables and imaging use patterns.
RESULTS - We identified 926 patients with a mean ± SD followup of 3.6 ± 1.3 years, of whom 30% underwent minimally invasive pyeloplasty. Overall 5.9% of patients had no postoperative imaging available. Within the first 6 months postoperatively 853 patients (91%) underwent at least 1 imaging study and 192 (24%) underwent renography. Within the first 12 months postoperatively 91% of patients underwent at least 1 imaging study, most commonly ultrasound. After 12 months almost a third of the patients were not followed with imaging. Of the 71% undergoing imaging most underwent ultrasound. Younger age and female gender were independently associated with frequent imaging (at least yearly) on multivariate logistic regression.
CONCLUSIONS - Following pediatric pyeloplasty there is variation in modality and frequency of imaging followup. The majority of patients are followed with renal ultrasound, with less frequent use of functional imaging. Almost a third of patients do not undergo followup imaging after 1 year.
Copyright © 2015 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.
PURPOSE - Although success rates are reported to be high, radiographic followup after pyeloplasty to correct ureteropelvic junction obstruction varies in intensity and modality. We characterized postoperative care after pyeloplasty to identify imaging trends.
MATERIALS AND METHODS - Using the MarketScan® database we identified patients 17 to 65 years old treated with pyeloplasty from 2007 to 2010. Followup imaging was classified as functional (diuretic renogram or excretory urogram) and nonfunctional (ultrasound, computerized tomography or magnetic resonance imaging). The postoperative period was divided into intervals of less than 6, 6 to 12, 12 to 24, 24 to 36 and greater than 36 months. We excluded from study patients with less than 24 months of postoperative enrollment in MarketScan. Multivariate logistic regression was used to determine associations between demographic variables and imaging utilization patterns.
RESULTS - We identified 742 patients with a mean ± SD followup of 36.8 ± 3.7 months, of whom 65% underwent minimally invasive pyeloplasty. Of the patients 12% underwent no postoperative imaging. Within the first 6 months 554 patients (75%) underwent at least 1 imaging study and within the first 12 months 82% underwent at least 1 imaging study, which was most commonly functional. After 12 months 54% of patients underwent any imaging, which was most commonly nonfunctional. At least annual imaging was significantly associated with older age, female gender and longer hospital stay. Secondary procedures were required in 62 patients (8%).
CONCLUSIONS - After pyeloplasty in adulthood most patients undergo a functional imaging study within 6 months. However, after 1 year only half of patients undergo followup imaging. Variability and insufficient radiological followup may bias the belief of pyeloplasty success.
Copyright © 2014 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.
PURPOSE - Ultrasonic propulsion to reposition urinary tract calculi requires knowledge about ultrasound image capture, device manipulation, and interpretation. The purpose of this study was to validate a cognitive and technical skills curriculum to teach urologists ultrasonic propulsion to reposition kidney stones in tissue phantoms.
MATERIALS AND METHODS - Ten board-certified urologists recruited from a single institution underwent a didactic session on renal ultrasound imaging. Subjects completed technical skills modules in tissue phantoms, including kidney imaging, pushing a stone through a translucent maze, and repositioning a lower pole calyceal stone. Objective cognitive and technical performance metrics were recorded. Subjects completed a questionnaire to ascertain face and content validity on a five-point Likert scale.
RESULTS - Eight urologists (80%) had never attended a previous ultrasound course, and nine (90%) performed renal ultrasounds less frequently than every 6 months. Mean cognitive skills scores improved from 55% to 91% (p<0.0001) on pre- and post-didactic tests. In the kidney phantom, 10 subjects (100%) repositioned the lower pole calyceal stone to at least the lower pole infundibulum, while 9 (90%) successfully repositioned the stone to the renal pelvis. A mean±SD (15.7±13.3) pushes were required to complete the task over an average of 4.6±2.2 minutes. Urologists rated the curriculum's effectiveness and realism as a training tool at a mean score of 4.6/5.0 and 4.1/5.0, respectively.
CONCLUSIONS - The curriculum for ultrasonic propulsion is effective and useful for training urologists with limited ultrasound proficiency in stone repositioning technique. Further studies in animate and human models will be required to assess predictive validity.
PURPOSE - The potential benefits of laparoscopic pyeloplasty may recede in younger age groups. We used a multi-institutional database to address the effect of laparoscopic approach on length of stay and postoperative parenteral narcotic use in specific pediatric age groups.
MATERIALS AND METHODS - We performed a retrospective study of 5,261 children with an ICD-9 procedure code for correction of ureteropelvic junction obstruction from the Pediatric Health Information System, a database of freestanding pediatric hospitals. Discharge dates from January 1, 2002 to June 30, 2007 were included. Laparoscopic cases were identified by ICD-9 procedure codes and hospital equipment charges. We used multivariate linear regression to investigate the effect of laparoscopic approach on length of stay and parenteral narcotic use in several age categories, including infant (1 month to less than 2 years old), preschool (2 to less than 6 years), grade school (6 to less than 10 years), preadolescent (10 to less than 13 years) and adolescent (13 to less than 19 years).
RESULTS - Laparoscopic approach decreased length of stay and number of parenteral narcotic pharmacy charges in the preadolescent (p = 0.03 and p = 0.005, respectively) and adolescent (p = 0.03 and p = 0.006, respectively) groups but not in any of the younger groups.
CONCLUSIONS - Laparoscopic approach was associated with a shorter hospital stay and decreased parenteral narcotic use in patients older than 10 years. Evolving technique may reveal less morbidity in younger patients. Future comparisons to open pyeloplasty should address specific pediatric age groups and outpatient convalescence.
PURPOSE - Pyeloplasty is increasingly performed on a short stay basis. We sought to determine what patient and treatment variables affect postoperative pain and length of stay, and whether an open approach could be considered "minimally invasive."
MATERIALS AND METHODS - We performed a retrospective review of patients younger than 10 years who underwent open pyeloplasty between 2001 and 2007. All patients received ketorolac every 6 hours and acetaminophen with codeine as needed. Data extracted from the medical records included morphine and codeine usage, patient age and gender, incision type, operative time, stent usage and outcome data (pain scores and length of stay). Multiple regression analyses were used to determine the association between variables and outcomes.
RESULTS - A total of 51 patients met the inclusion criteria. Patient age and gender, operative time and stent usage had no significant correlation with mean or median pain scores. Children who received morphine had significantly higher mean, median and maximum pain scores and length of stay (33 vs 23 hours) than those who did not receive morphine. Multiple regression analyses revealed that morphine usage and dorsal lumbotomy incision were independently associated with higher mean, median and maximum pain scores, and a nephroureteral catheter was correlated with a higher maximum pain score. The only variable associated with length of stay was morphine usage.
CONCLUSIONS - Morphine usage was the most significant variable associated with increased pain scores and increased length of stay. Ketorolac and acetaminophen/codeine provide better pain control, and allow children to return home within 24 hours. With mean pain scores less than 1 this series demonstrates that open pyeloplasty can be "minimally invasive."
BACKGROUND - Inhibition of angiotensin action, pharmacologically or genetically, during the neonatal period leads to renal anomalies involving hypoplastic papilla and dilated calyx. Recently, we documented that angiotensinogen (Agt -/-) or angiotensin type 1 receptor nullizygotes (Agtr1 -/-) do not develop renal pelvis nor ureteral peristaltic movement, both of which are essential for isolating the kidney from the high downstream ureteral pressure. We therefore examined whether these renal anomalies could be characterized as "obstructive" nephropathy.
METHODS - Agtr1 -/- neonatal mice were compared with wild-type neonates, the latter subjected to surgical complete unilateral ureteral ligation (UUO), by analyzing morphometrical, immunohistochemical, and molecular indices. Agtr1 -/- mice were also subjected to a complete UUO and were compared with wild-type UUO mice by quantitative analysis. To assess the function of the urinary tract, baseline pelvic and ureteral pressures were measured.
RESULTS - The structural anomalies were qualitatively indistinguishable between the Agtr1 -/- without surgical obstruction versus the wild type with complete UUO. Thus, in both kidneys, the calyx was enlarged, whereas the papilla was atrophic; tubulointerstitial cells underwent proliferation and also apoptosis. Both were also characterized by interstitial macrophage infiltration and fibrosis, and within the local lesion, transforming growth factor-beta 1, platelet-derived growth factor-A and insulin-like growth factor-1 were up-regulated, whereas epidermal growth factor was down-regulated. Moreover, quantitative differences that exist between mutant kidneys without surgical obstruction and wild-type kidneys with surgical UUO were abolished when both underwent the same complete surgical UUO. The hydraulic baseline pressure was always lower in the pelvis than that in the ureter in the wild type, whereas this pressure gradient was reversed in the mutant.
CONCLUSION - The abnormal kidney structure that develops in neonates during angiotensin inhibition is attributed largely to "functional obstruction" of the urinary tract caused by the defective development of peristaltic machinery.
The embryonic development of mammalian kidneys is completed during the perinatal period with a dramatic increase in urine production, as the burden of eliminating nitrogenous metabolic waste shifts from the placenta to the kidney. This urine is normally removed by peristaltic contraction of the renal pelvis, a smooth muscle structure unique to placental mammals. Mutant mice completely lacking angiotensin type 1 receptor genes do not develop a renal pelvis, resulting in the buildup of urine and progressive kidney damage. In mutants the ureteral smooth muscle layer is hypoplastic and lacks peristaltic movements. We show that angiotensin can induce the ureteral smooth muscles in organ cultures of wild-type, but not mutant, ureteral tissues and that, in wild-type mice, expression of both renal angiotensin and the receptor are transiently upregulated at the renal outlet at birth. These results reveal a new role for angiotensin in the unique cellular adaptations of the mammalian kidney to the physiological stresses of postnatal life.