Correlation between renal sonographic measurements and differential renal function obtained from nuclear renography in children with unilateral hydronephrosis.

INTRODUCTION: Children with higher grades of hydronephrosis often undergo mercaptoacetyltriglycine nuclear renography scans (MAG3) to assess differential renal function (DRF) and drainage. Although MAG3 helps identify the potential need for pyeloplasty, its use incurs increased costs, radiation exposure, and stress for children and families. Several studies demonstrate pyramidal thickness (PT) ≤ 3 mm as a reliable predictive risk factor for pyeloplasty in children with a history of prenatal hydronephrosis. Our hypothesis was that renal sonographic measurements including PT and parenchymal thickness (ParT) correlate with DRF in children with high-grade unilateral hydronephrosis and may be used to better select the need and frequency of MAG3 scans in children at increased risk for diminished relative renal function. The objective of this project was to determine the correlation between sonographic renal measurements and DRF in patients with unilateral hydronephrosis, we assessed: 1) the correlation between PT, ParT, and the ratio of PT/ParT in hydronephrotic kidneys to DRF, 2) the correlation between the ratio of hydronephrotic PT/contralateral non-hydronephrotic PT and DRF, 3) the correlation between the ratio of hydronephrotic ParT/contralateral non-hydronephrotic ParT and DRF, and 4) the correlation between the ratio of (hydronephrotic PT/ParT)/(contralateral non-hydronephrotic PT/ParT) and DRF. MATERIALS AND METHODS: We retrospectively reviewed 71 children with grades 3 or 4 unilateral hydronephrosis. Most patients presented with a history of prenatally detected hydronephrosis at median age (IQR) of 112 days (43-274). Measurements of PT and ParT were completed on 98 renal ultrasounds and DRF was collected from corresponding MAG3 scans. Threshold values were identified visually through scatterplots. Spearman's correlation coefficient and Fisher's p-values were calculated. DISCUSSION: Ratios of PT and ParT in hydronephrotic kidneys to contralateral non-hydronephrotic kidneys were positively correlated with DRF. Ratios of hydronephrotic PT/non-hydronephrotic PT > 0.8 and hydronephrotic ParT/non-hydronephrotic ParT >0.7 occurred more frequently in patients with a DRF >40% (p = 0.11 and p = 0.001, respectively). A PT > 3 mm and ParT >5 mm occurred significantly more frequently in patients with a DRF >40% (p = 0.008 and p = 0.006, respectively). CONCLUSIONS: Renal sonographic measurements including threshold values of PT > 3 mm, ParT > 5 mm, ratio of hydronephrotic PT/contralateral non-hydronephrotic PT (>0.8), and ratio of hydronephrotic ParT/contralateral non-hydronephrotic ParT (>0.7) are good predictors of DRF >40% in unilateral high-grade hydronephrosis. These identified threshold values have potential utility in determining the need for nuclear renal scans in children with high-grade hydronephrosis.

A simple technique for percutaneous antegrade retrieval of proximally migrated double J stents after pyeloplasty in infants.

Proximal migration of double J (DJ) stent after pyeloplasty poses a difficult problem in infants whose small ureter renders retrograde ureteroscopic retrieval difficult. Previously described antegrade techniques used large access sheaths or blind removal under fluoroscopic guidance. We describe a technique for antegrade retrieval of the stent under direct vision. A 8F vascular access sheath is placed into the renal pelvis under ultrasound guidance. A 6F nephroscope with 3F forceps placed through the sheath grasps and retrieves the stent under direct visualization. This technique is simple, quick, avoids radiation exposure and was used by us successfully in 2 small infants.

Robotic-Assisted Laparoscopic Pyeloplasty in Challenging Cases of Ureteropelvic Junction Obstruction in the Pediatric Population: A Multicenter Review.

Purpose: To report a multi-institutional international experience in performing robotic pyeloplasty for complicated cases of ureteropelvic junction obstruction (UPJO) in the pediatric population and assess feasibility and outcomes. Materials and Methods: Retrospective chart review of all pediatric patients who underwent robotic-assisted laparoscopic pyeloplasty (RALP) for UPJO in challenging cases between 2013 and 2021 was included. Demographics, perioperative surgical data, complications, and results are described. Challenging cases were defined as bilateral UPJO, failure of previous open pyeloplasty (thus re-do cases), correction of UPJO in kidneys with anatomical variations, huge hydronephrosis, and low-weight infants (<6 kg). Results: Over an 8-year period, 36 children (62% males and 38% females) met the inclusion criteria for our study. Fifteen patients underwent RALP for recurrent UPJO; among them, 2 children required simultaneous surgery for renal stones, 3 cases of lower pole UPJO in double collecting system, 3 cases of pelvic and horseshoe kidneys, 10 cases of infants weighing <6 kg, 3 cases of huge hydronephrosis, and 2 cases of bilateral UPJO. The median age and weight were 36 months (interquartile range [IQR] 14-84) and 12 kg (IQR 10-20.5), respectively. All robotic cases were completed successfully with no conversion to an open procedure. The median operative time was 120 minutes (IQR 90-135). The mean length of hospital stay was 2.6 days. Four patients (17%) had postoperative complications-1 ileus (Clavien-Dindo grade [CDG] I) and 3 urinary tract infections (CDG II). No CDG III or higher complication was encountered. At a median follow-up of 36 months, the success rate was 95% with 1 patient requiring another re-do procedure due to recurrent obstruction. Conclusions: Our data suggest that RALP is safe and effective even for challenging cases of UPJO in children.

Parental experience and understanding of parent-provider discussions of treatment for infants with ureteropelvic junction obstruction.

Objective: The purpose of the current study was to understand what families identify as necessary information to guide decision-making in the treatment of their child with UPJO. Methods: We conducted semi-structured interviews with parents of children with UPJO using phenomenological methodology. Data were systematically analyzed according to principles of thematic analysis, using a team-based inductive approach. Results: 32 parents were interviewed. Findings are organized by three major themes including barriers to meaningful participation in decision making, logistical aspects of the decision, and psychosocial aspects of the decision. Conclusion: These findings suggest the need to increase parent education and understanding around medical and surgical decision-making, and the need to enhance psychosocial support for more meaningful parental engagement in the surgical decision-making process. Practice implications: The findings from the interviews highlight the importance of caregivers needing clear and accurate information in order to engage in meaningful discussions related to surgical decision-making for decisions around surgery for UPJO treatment.

Robot-assisted pyeloplasty: How to deal with anatomic variants? A step-by-step video presentation.

INTRODUCTION: Pyeloplasty (open or Robot-assisted) is the gold standard of a symptomatic UPJ stenosis. Sometimes anatomic variants make the procedure challenging. This video describes a step-by-step approach in three settings: a crossing blood vessel and two different presentations of incomplete duplicated system. MATERIALS AND METHODS: Under general anesthesia, patient positioned in lateral decubitus, three trocars are placed. After mobilization of the colon, the Gerota's fascia is opened, and the renal pelvis is dissected off the surrounding structures. Ureter and obstructed pyelum were subsequently identified, mobilized, and hinged on a traction stitch. The pyelum and ureter are divided and spatulated according to the Anderson-Hynes technique; anastomosis is achieved. In variants, the drainage is one of the challenging steps, needing custom-made drainage of both moieties. Correct positioning of the drainage is confirmed with reflux of methylene blue from the bladder. RESULTS: JJ stent was removed 6 weeks postoperatively in surgical day-clinic, additional drainage was removed 1 week after surgery in the outpatient clinic. All three children remain asymptomatic with over a year of follow-up. CONCLUSION: A step-by-step plan for pyeloplasty in case of anatomic variants is presented with a video demonstrating a robot-assisted approach in duplicated systems. Moiety drainage can be challenging.

Comparison of laparoscopic pyeloplasty vs. robot-assisted pyeloplasty for the management of ureteropelvic junction obstruction in children.

Background: Ureteropelvic junction obstruction (UPJO) is a commonly observed abnormality in pediatric urology. Minimally invasive approaches have gained popularity in recent years. Studies have demonstrated excellent results with both laparoscopic pyeloplasty (LAP) and robot-assisted pyeloplasty (RAP). Few studies have compared the experience of both procedures performed in a single institution. Our objective is to compare laparoscopic pyeloplasty and robot-assisted pyeloplasty in the Puerto Rican pediatric population. Methods: We conducted a retrospective cohort study using our clinic's database on patients with UPJO that were operated by the same surgeon (MPB) from 2008 to 2019. Statistical analysis was conducted of demographics, preoperative studies, perioperative data and complications of both procedures. This study was approved by our local IRB committee. Results: A total of 86 patients that underwent pyeloplasty with at least 3 years of follow up were recorded for this study. Laparoscopic pyeloplasty and robot-assisted pyeloplasty were performed in 44 (51.1%) and 42 (48.8%) patients, respectively. Patient age ranged between 4 months and 17 years (LAP group - mean age of 6.19 years/RAP group - mean age of 7.07 years). Success rates was high in this series (LAP - 100% and RAP -95%). Using Wilcoxon signed rank test and Mann whitney sum test, significant differences between preoperative and postoperative hydronephrosis grading were observed in both LAP and RAP groups. However, no significant difference was seen regarding reduction of hydronephrosis grading when comparing both groups. No intraoperative complications were seen on either group. Conclusion: Both LAP and RAP are safe and effective procedures that can properly manage UPJO. Our study shows that, under experienced hands, pure laparoscopic pyeloplasty achieves comparable results to robotic assisted laparoscopic pyeloplasty. Pediatric urologists should be comfortable offering either of these approaches as they demonstrate high success rates in our pediatric population. Selection of LAP vs. RAP approach depends on the Surgeon's preference or experience, and on institutional availability. Minimally invasive therapies will continue to gain popularity with future advances in laparoscopic and robotic technology.

Initial observational management of hydronephrosis in infants with reduced differential renal function and non-obstructive drainage parameters.

INTRODUCTION: Hydronephrosis secondary to ureteropelvic junction (UPJ) obstruction is a common finding in infants with prenatally-diagnosed hydronephrosis and often results in pyeloplasty due to obstructive drainage parameters and/or renal function compromise. However, little is known regarding the natural history of hydronephrosis with reduced differential renal function (DRF) but non-obstructive drainage. OBJECTIVE: We sought to explore our experience with initial observational management of these patients. STUDY DESIGN: A retrospective review of our institutional database of all diuretic MAG-3 renal scans obtained between 2000 and 2016 was performed. We included patients with antenatally-detected unilateral hydronephrosis ≥ SFU grade 2, first MAG-3 scan prior to 18months of age, DRF <40% and post-furosemide half-time (T1/2) <20 min. Exclusion criteria were: hydroureter, VUR, solitary kidney, duplication anomalies. Outcomes of interest were a progression of T1/2 ≥ 20 min and/or further decline in DRF >5%. RESULTS: Of 704 patients with unilateral hydronephrosis, 91 had DRF≤40%, of which 29 (18 boys, 11 girls) met our inclusion criteria and were followed for a mean of 2.8 years (1.4 months-6.6 years). Mean age at first sonogram was 2.3 months. 2 patients had SFU grade 2, 16 had grade 3, and 9 had grade 4 hydronephrosis, and 2 unknown grade. Median half-time on initial MAG-3 scan across all patients was 10 min (3-20 min). Initial MAG3 scan was performed at a median of 2.3 months of age (0.3-17 months). 22/29 patients had >1 MAG3 scan. Of the 7 remaining, 5 were lost to follow-up and 2 demonstrated improvement in hydronephrosis. Worsening drainage occurred in 10/22(45%), median final T1/2 was 45.5 min 8 of these underwent pyeloplasty and 2 were lost to follow up. 4/22 patients (18%) had progressive decline in DRF (mean 8.3%, range 6-10%). 3/4 maintained non-obstructive drainage patterns and stable/improved hydronephrosis, and 1 underwent pyeloplasty. 13/18 remaining patients had stable DRF and 5 had improvement in DRF. 7(39%) of these underwent surgery for worsening drainage (Summary Figure). Overall, 7/29(24%) patients had sufficient resolution of hydronephrosis to be discharged from our care, 8(28%) are under continued observation, 9(31%) underwent pyeloplasty, and 5(17%) were lost to follow-up. In the observational group [median follow-up 4.5 years (3.7-6.6 years)], all 8 demonstrated improved non-obstructive drainage (T1/2 <20 minutes) and/or improvement in hydronephrosis. 4/10(40%) with DRF <35% underwent pyeloplasty versus 5/19(26%) with DRF 35-40%(p=0.67). CONCLUSION: Initial observational management of unilateral hydronephrosis with reduced DRF and nonobstructive drainage is recommended as most kidneys maintain nonobstructive drainage and do not demonstrate further decline in DRF. Even when DRF decreases, the majority remain non-obstructive. Worsening drainage over time more often leads to the decision for pyeloplasty rather than change in DRF.

Symptomatic Parapelvic Cysts in Children: Anatomical and Histological Features, Diagnostic Pitfalls and Urological Management.

BACKGROUND: Symptomatic parapelvic cysts (PPC) are rare entities. Our objective is to highlight specific features of PPC to avoid a misdiagnosis of UPJ obstruction. METHODS: We retrospectively reviewed the records of children managed between 2012-2017. RESULTS: All four patients (18 months-8 years) presented with acute renal colic with a large intra-sinusal liquid mass (42-85 mm) on ultrasound, evoking a diagnosis of UPJ obstruction. On preoperative renal scintigraphy (n = 3) there was no dilatation of the renal pelvis and ipsilateral differential function was impaired in 2. Diagnosis of PPC was suspected preoperatively in three children (CT scan (n = 1); MRI (n = 2)) and made peri-operatively (n = 1). Preoperative retrograde pyelography (n = 3) and a further intraoperative retrograde pyelography with methylene blue (n = 1) did not identify communication with the cyst. No renal pelvis was identified in two patients. De-roofing of the cyst was curative in all cases at 5 years mean follow-up (no leakage, cyst recurrence or loss of function) and all 4 patients became asymptomatic after surgery. Histology demonstrated a single flat epithelial cell layer. Renal function normalized in one patient but remained impaired in the other. CONCLUSION: In case of symptoms of UPJ obstruction with a medial renal liquid mass on ultrasound, PPC should be considered when no dilatated pelvis on renal scan is identified. In such cases, a complementary imaging work-up is mandatory prior to surgery.

Systematic Review and Meta-Analysis of Pediatric Robot-Assisted Laparoscopic Pyeloplasty.

Introduction: To perform a systematic review (SR) and meta-analysis (MA) of outcomes of robot-assisted laparoscopic pyeloplasty (RALP) for ureteropelvic junction (UPJ) obstruction in children. Evidence Acquisition: A SR of the English-language literature on surgical techniques and perioperative outcomes of RALP for UPJ obstruction in children was performed without time filters using the MEDLINE (through PubMed), EMBASE, and Cochrane databases in July 2020 according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement recommendations. Evidence Synthesis: Overall, 58 studies were selected for qualitative analysis, 46 of which were included in the MA. Nearly all studies included were observational and retrospective, either cohort or case-control. The quality of evidence was assessed using Modified Newcastle-Ottawa Scoring, with the majority of studies scoring medium or high quality. The mean success rate was 95.4% (confidence interval 91.0%-99.3%), over a wide age range. There was a noticeable heterogeneity in reported follow-up length and definitions of success rate. The majority of studies reported length of stay of ∼1 day. The mean overall complication rate was 12%. For studies that reported complication rate by grade, the mean low Clavien grade (Grade 2 or less) complication rate was 9.3% and the mean high Clavien grade (Grade 3 or more) complication rate was 6.5%. Conclusions: Robot-assisted surgery is technically feasible and has been shown to achieve very favorable outcomes for pyeloplasty in children. The evidence, however, is mostly retrospective and from single sites, which introduces potential biases. Further research is needed to further elucidate RALP benefits compared with the open and laparoscopic approach. As a randomized control trial may not be practical in this space, perhaps a prospective multi-institutional design with a uniform reporting system of pediatric RALP is the next step to define its benefits and limits.

Giant hydronephrosis secondary to ureteropelvic junction obstruction, a rare occurrence, case report.

Giant hydronephrosis (GH) is very rare in adults. We report a case of a 46-year-old man who presented with progressively increasing abdominal swelling. A contrast-enhanced CT scan of the abdomen and pelvis was used for the diagnosis. Left side open nephrectomy was performed and 22 L fluid was evacuated. UPJ obstruction was noted intraoperatively. No recurrence of abdominal swelling was noted on follow up examination.

Learning curve of robotic-assisted laparoscopic pyeloplasty (RALP) in children: how to reach a level of excellence?

It has been suggested that up to 40 cases of RALP are required to reach the operative results equal to open surgery. We have hypothesized that previous experience in open and laparoscopic surgeries might shorten the learning curve of robotic surgery. We have retrospectively evaluated the data of all children who underwent pyeloplasty in our institute by a single surgeon since 2003. The children were divided into three groups: open pyeloplasty (OP) of 72 children, laparoscopic pyeloplasty (LAP) of 22, and RALP of 33 patients subsequently. The data included: demographics, duration of surgery, length of stay, success of surgery, and complication rate according to the Clavien-Dindo score. The groups were ordered chronologically by the operation date and each group was divided into two different phases: early and late. A comparison was made between the data of the early and the late phase. There was no difference in the demographic data between the groups; however, the patients who underwent laparoscopic surgery were significantly older compared with the patients from the other groups. The median duration of surgery in the RALP group was significantly shorter than the OP group (65 min vs 72.5 min P < 0.01), while the first RALP case was already shorter than the median duration of surgery in OP group. There was no significant decrease in the duration of surgery of the RALP group over the study period, though there was a significant trend of decreasing operative time in the OP and LAP groups. There was no difference in the length of stay in the early vs late phases in the RALP group. There was no difference in the complication and success rate between the RALP and OP group, as well as the early and late phases of the RALP group. Our data show that previous experience in OP and LAP surgery may contribute to a shorter learning curve of robotic surgery required for the surgeon to achieve a similar outcome to that of OP.

Physician perspectives on discussions with parents of infants with suspected ureteropelvic junction obstruction.

INTRODUCTION: The purpose of this study was to understand pediatric urologists' perceived role of patient characteristics on discussions about treatment of infants with suspected UPJ obstruction. METHODS: We conducted semi-structured interviews with pediatric urologists from three geographically diverse sites. Interview domains included: clinical indications for surgery, discussions with parents, and consideration of parent socioeconomic factors. Transcribed data and field notes were analyzed using a team-based, inductive grounded theory approach. RESULTS: Thirteen physicians were interviewed. Physicians reported a standardized approach to discussions to facilitate parental understanding. While they did not report overt consideration of demographics, they tailored discussions based on educational and cultural background and language barriers. Physicians also reported that concerns about risk of loss to follow up contributed to their treatment recommendations. Most physicians recognized that the lack of clear data often led to use of personal experience to guide recommendations. CONCLUSION: Physicians recognize a gap in data to guide surgical decisions and utilize personal experience to augment this gap. They also recognize the influence of educational and language barriers on discussions with families and consider risk of loss to follow up when making recommendations, suggesting an implicit consideration of demographics. These findings suggest that development of evidence-based guidelines may reduce treatment variations. LEVEL OF EVIDENCE: Not applicable (qualitative research study written in compliance with COREQ guidelines).

Managing Ureteropelvic Junction Obstruction in the Young Infant.

In the last decade, management of congenital UPJ obstruction has become progressively observational despite the lack of precise predictors of outcome. While it is clear that many children will have resolution of their hydronephrosis and healthy kidneys, it is equally clear that there are those in whom renal functional development is at risk. Surgical intervention for the young infant, under 6 months, has become relatively infrequent, yet can be necessary and poses unique challenges. This review will address the clinical evaluation of UPJO in the very young infant and approaches to determining in whom surgical intervention may be preferable, as well as surgical considerations for the small infant. There are some clinical scenarios where the need for intervention is readily apparent, such as the solitary kidney or in child with infection. In others, a careful evaluation and discussion with the family must be undertaken to identify the most appropriate course of care. Further, while minimally invasive pyeloplasty has become commonly performed, it is often withheld from those under 6 months. This review will discuss the key elements of that practice and offer a perspective of where minimally invasive pyeloplasty is of value in the small infant. The modern pediatric urologist must be aware of the various possible clinical situations that may be present with UPJO and feel comfortable in their decision-making and surgical care. Simply delaying an intervention until a child is bigger may not always be the best approach.

Surgical decision-making in infants with suspected UPJ obstruction: stakeholder perspectives.

INTRODUCTION: Although there are significant demographic and clinical variations in treatment decisions for infants with high-grade hydronephrosis concerning for ureteropelvic junction obstruction (UPJO), there has been little research on the roles of parents and surgeons in the surgical decision-making (DM) process. OBJECTIVE: The purpose of this study was to understand parents' and surgeons' perceived roles in the surgical DM process for infants with high-grade hydronephrosis. STUDY DESIGN: Semistructured interviews were conducted with pediatric urologists from three regionally diverse tertiary referral sites and parents of infants diagnosed and treated for unilateral Society for Fetal Urology grade 3 or 4 hydronephrosis at one tertiary pediatric urology practice. Purposive sampling was used to ensure adequate representation of parents based on treatment choice, patient gender, race/ethnicity, and distance from the practice. Survey domains included (1) discussions about diagnosis and treatment options, (2) factors guiding treatment choice, and (3) participants' role in the DM process. Transcribed data and field notes were analyzed using a team-based, inductive grounded theory qualitative approach. RESULTS: Thirteen physicians and 32 parents were interviewed between November 2016 and November 2017. Parents and surgeons agreed that the surgeon was best equipped to guide treatment decisions because of their clinical knowledge and experience. Parents reported that their trust in the surgeon was the primary factor in their decisions. Surgeons reported tailoring discussions with parents to not only educate them about treatment options but also to develop an ongoing relationship with parents. Both parents and surgeons reported being satisfied with their roles in the DM process. DISCUSSION: This study suggests that parental trust in the surgeon and surgeon recommendations drive DM. This may be due to a lack of explicit discussion of options or of parental values and preferences for care. Limited discussions may also impact parental understanding of risks and potential complications. These findings are similar to those of prior studies in adults and children considering elective surgery. CONCLUSIONS: In this study, parents and surgeons reported that surgeon recommendations, rather than parent preferences, guide treatment choices for infants with suspected UPJO. Both parents and surgeons are satisfied with a physician-driven approach to DM, suggesting that, in situations where the perceived risk is low and parental knowledge is limited, parents may find a physician-led approach beneficial. Data gleaned from this study will be used to inform future quantitative studies evaluating factors guiding surgeon recommendations for treatment and their associations with underlying treatment variation.

Current Concepts in Pediatric Robotic Assisted Pyeloplasty.

Robotic surgery in pediatric urology has been gaining popularity since its introduction almost two decades ago. Robotic assisted pyeloplasty is the most common robotic procedure performed in pediatric urology. Advances in robotic technology, instrumentation, patient care and surgical expertise have allowed the correction of ureteropelvic junction (UPJ) obstruction in most patients using this minimally invasive technique. The excellent experience with robotic assisted pyeloplasty has challenged other approaches as a new standard for the treatment of UPJ obstruction. In this review, we will describe the technique as it relates to the different robotic platforms, review the surgical experience and compare its results to other surgical approaches. Also, we will discuss patient and parent satisfaction, cost and financial considerations, along with evaluating the future of robotic surgery in the treatment of UPJ obstruction.

Urinary antimicrobial peptides: Potential novel biomarkers of obstructive uropathy.

INTRODUCTION: Antimicrobial peptides (AMPs) have historically been evaluated for their role in protecting against uropathogens. However, there is mounting evidence to support their expression in noninfectious injury, with unclear meaning as to their function. It is possible that AMPs represent urothelial injury. Urinary tract obstruction is known to alter the urothelium; however, AMPs have not been evaluated for expression in this noninfectious injury. OBJECTIVE: A pilot study to compare urinary AMP expression in children undergoing surgical intervention for ureteropelvic junction obstruction (UPJO) with nonobstructed controls. STUDY DESIGN: Bladder urine was collected from consenting/assenting pediatric patients with UPJO at intervention. Control bladder urines were obtained from age-matched and sex-matched healthy children without known obstruction or infection. Enzyme-linked immunosorbent assays were run for the following AMPs: ß defense 1 (BD-1), neutrophil gelatinase-associated lipocalin (NGAL), cathelicidin (LL-37), hepatocarcinoma-intestine-pancreas/pancreatitis-associated protein (HIP/PAP), and human α defensin 5 (HD-5); and normalized to urine creatinine. Results were analyzed with Student's t-test or Mann-Whitney U test, when appropriate, and receiver operating characteristic curves. A P-value of <0.05 was considered significant. RESULTS: Thirty bladder urine samples were obtained from children with UPJO at the time of decompressive intervention. Mean patient age was 4.7 years (range 0.3-18.4); 20 (67%) patients were male. Fifteen bladder urine samples were obtained from age-matched and sex-matched controls. Urinary AMP levels were significantly higher in UPJO patients than controls for BD-1 (P = 0.015), NGAL (P < 0.001), LL-37 (P < 0.001), and HIP/PAP (P = 0.046). Optimal threshold values of these AMPs were determined, with each demonstrating significant odds ratios of predicting urinary obstruction. DISCUSSION: Certain urinary AMPs are altered even in noninfectious urinary tract pathology. This represents a novel induction of AMP expression, as the current study is the first to report elevations in BD-1 and HIP/PAP in urinary tract obstruction. This suggests other roles for these AMPs outside of their antimicrobial properties, and likely is a reflection of the urothelial and tubular stress resulting from obstructive uropathy. CONCLUSIONS: Induction of AMPs BD-1, NGAL, LL-37, and HIP/PAP was found to occur in urinary tract obstruction. Further evaluation of AMP expression as a biomarker of uroepithelial injury outside of infection is indicated.