Determination of Success by Objective Scintigraphic Criteria After Laparoscopic Pyeloplasty

Unsupervised Machine Learning to Identify Risk Factors of Pyeloplasty Failure in Ureteropelvic Junction Obstruction

Introduction: In adult patients with ureteropelvic junction obstruction (UPJO), little data exist on predicting pyeloplasty outcome, and there is no unified definition of pyeloplasty success. As such, defining pyeloplasty success retrospectively is particularly vulnerable to bias, allowing researchers to choose significant outcomes with the benefit of hindsight. To mitigate these biases, we performed an unsupervised machine learning cluster analysis on a dataset of 216 pyeloplasty patients between 2015 and 2023 from a multihospital system to identify the defining risk factors of patients that experience worse outcomes. Methods: A KPrototypes model was fitted with pre- and perioperative data and blinded to postoperative outcomes. T-test and chi-square tests were performed to look at significant differences of characteristics between clusters. SHapley Additive exPlanation values were calculated from a random forest classifier to determine the most predictive features of cluster membership. A logistic regression model identified which of the most predictive variables remained significant after adjusting for confounding effects. Results: Two distinct clusters were identified. One cluster (denoted as "high-risk") contained 111 (51.4%) patients and was identified by having more comorbidities, such as old age (62.7 vs 35.7), high body mass index (BMI) (26.9 vs 23.8), hypertension (66.7% vs 17.1%), and previous abdominal surgery (72.1% vs 37.1%) and was found to have worse outcomes, such as more frequent severe postoperative complications (7.2% vs 1.0%). After adjusting for confounding effects, the most predictive features of high-risk cluster membership were old age, low preoperative estimated glomerular filtration rate (eGFR), hypertension, greater BMI, previous abdominal surgery, and left-sided UPJO. Conclusions: Adult UPJO patients with older age, lower eGFR, hypertension, greater BMI, previous abdominal surgery, and left-sided UPJO naturally cluster into to a group that more commonly suffers from perioperative complications and worse outcomes. Preoperative counseling and perioperative management for patients with these risk factors may need to be thought of or approached differently.

The Utility of Radiologic and Symptomatic Surveillance After Minimally-invasive Adult Pyeloplasty

OBJECTIVE

To evaluate different types of failure after minimally-invasive pyeloplasty (MIP) when stratified by initial radiologic study and symptoms after ureteral stent removal.

METHODS

We retrospectively reviewed adults who underwent MIP (1996-2019) at a single academic center. Patients with at least 11 months of follow-up and patients who had a Mag3 scan as their initial postoperative imaging were included. Postprocedure, patients were categorized as having normal, equivocal, or obstructed imaging based on their initial radiologic test. Patients who were obstructed were excluded. Primary outcome was procedural failure, defined as the need for a procedure to treat recurrent obstruction. Secondary outcomes were radiologic failure and symptomatic failure. Groups were compared to assess for statistical significance (P <.05).

RESULTS

Overall, 122 patients met inclusion criteria. On initial postoperative imaging, 108 (89%) patients had no obstruction and 14 (11%) had equivocal findings. The procedural failure rate was 6.5% in the unobstructed group and 28.6% in the equivocal group (P = .023). Seven unobstructed patients (6.5%) and 2 equivocal patients (14.3%) eventually experienced radiologic failure (P = .275). Among patients who had no obstruction on initial imaging and remained asymptomatic, only one (0.9%) required a salvage procedure.

CONCLUSION

Recurrent obstruction after pyeloplasty varied based on the outcome of the initial radiologic study. These rates can be used to counsel patients and guide physicians' choice of surveillance schedules. The risk of future failure is very low in asymptomatic patients with normal initial imaging. The utility of routine radiologic surveillance in these patients may be limited.

The Impact of Preoperative Double-J Stent on Perioperative Complications, Recurrence, and Quality of Life in Adult Patients Undergoing Pyeloplasty

PURPOSE

This study aimed to evaluate the impact of preoperative double-J stent (DJ) in pyeloplasty patients on perioperative complications, recurrence, and quality of life (QoL).

METHODS

Pyeloplasties due to ureteropelvic junction obstructions between January 2010 and December 2020 were consecutively identified. A standardized follow-up questionnaire was used. Tabulation was made according to preoperative DJ versus no DJ. Subgroup analyses addressed primary robotic pyeloplasties.

RESULTS

Of 95 pyeloplasty patients, 62% received a preoperative DJ. Patients with preoperative DJ exhibited higher rates of Clavien-Dindo (CD) 2 (22 vs. 11%) complications, but not of CD3 (8.5 vs. 8.3%, p = 0.5). After a median follow-up of 61 months, 9 patients exhibited a recurrence, of whom 7 had a preoperative DJ. In QoL assessment, comparable findings were made between patients with and without preoperative DJ. In robotic pyeloplasty patients (n = 73), patients with preoperative DJ (58%, n = 42) experienced higher CD3 complication rates, compared to patients without preoperative DJ (12 vs. 6.5%). Moreover, higher rates of recurrences were observed in preoperative DJ patients (12 vs. 3.2%).

CONCLUSION

In a contemporary pyeloplasty cohort, the midterm success rate was good with 91%. Our findings suggest that preoperative DJ is associated with higher recurrence rates. However, QoL did not differ between patients with and without preoperative DJ.

Primary vs redo robotic pyeloplasty: A comparison of outcomes

INTRODUCTION

Robot-assisted laparoscopic pyeloplasty (RALP) is a safe and efficacious option for repair of UPJO. We hypothesize that redo-RALP is technically more difficult but has comparable outcomes to primary RALP.

METHODS

An IRB-approved single institutional registry was utilized to identify all patients undergoing primary or redo RALP from 2012 to 2019. Redo RALP consisted of pyeloplasty and ureterocalicostomy (RALUC). Peri-operative and post-operative details and outcomes were aggregated. Successful reconstruction was defined as resolution of symptoms, improved hydronephrosis and no need for additional procedures.

RESULTS

From 399 patients who underwent UPJO repair at our center, a total of 306 with a median age of 4.9 years at surgery and a median follow-up of 18.5 months were included: 276 primary and 30 redo (21 RALP and 9 RALUC). Redo group had significantly longer procedure time and length of stay compared to the primary group. However, no significant difference was noted in the post-operative complications, need for additional endoscopic procedures or redo reconstruction, and success between the two groups. Multivariate analysis showed that when controlled for age, gender, 30-days post-operative complication and anatomy of obstruction, redo as compared to primary reconstruction did not have a significant effect on success.

DISCUSSION

This study is the largest controlled cohort in the pediatric population comparing redo RALP with an established control group -primary RALP. This retrospective chart review possesses the biases innate to any retrospective study. The low number of re-operative cases as well as low rate of failure in redo RALP further complicates identification of statistically significant predictors of outcomes following redo RALP.

CONCLUSION

Redo RALP is an efficient and safe approach for reconstruction of recurrent UPJO, with low complication rate and high success rate, comparable to primary RALP.

Laparoscopic renal surgery is here to stay

Objectives

To review the current literature comparing the outcomes of renal surgery via open, laparoscopic and robotic approaches.

Materials and methods

A comprehensive literature search was performed on PubMed, MEDLINE and Ovid, to look for studies comparing outcomes of renal surgery via open, laparoscopic, and robotic approaches.

Results

Limited good-quality evidence suggests that all three approaches result in largely comparable functional and oncological outcomes. Both laparoscopic and robotic approaches result in less blood loss, analgesia requirement, with a shorter hospital stay and recovery time, with similar complication rates when compared with the open approach. Robotic renal surgeries have not shown any significant clinical benefit over a laparoscopic approach, whilst the associated cost is significantly higher.

Conclusion

With the high cost and lack of overt clinical benefit of the robotic approach, laparoscopic renal surgery will likely continue to remain relevant in treating various urological pathologies.

Laparoscopic management of recurrent ureteropelvic junction obstruction following pyeloplasty: a single surgical team experience with 38 cases

Purpose

To describe and analyze our experience with Anderson-Hynes transperitoneal laparoscopic pyeloplasty (LP) in the treatment of recurrent ureteropelvic junction obstruction (UPJO).

Materials and methods

38 consecutive patients who underwent transperitoneal laparoscopic redo-pyeloplasty between January 2007 and January 2015 at our department were included in the analysis. 36 patients were previously treated with dismembered pyeloplasty and 2 patients underwent a retrograde endopyelotomy. All patients were symptomatic and all patients had a T1/2>20 minutes at pre-operative DTPA (diethylene-triamine-pentaacetate) renal scan. All data were collected in a prospectively maintained database and retrospectively analyzed. Intraoperative and postoperative complications have been reported according to the Satava and the Clavien-Dindo system. Treatment success was evaluated by a 12 month-postoperative renal scan. Total success was defined as T1/2≤10 minutes while relative success was defined as T1/2between 10 to 20 minutes. Post-operative hydronephrosis and flank pain were also evaluated.

Results

Mean operating time was 103.16±30 minutes. The mean blood loss was 122.37±73.25mL. The mean postoperative hospital stay was 4.47±0.86 days. No intraoperative complications occurred. 6 out of 38 patients (15.8%) experienced postoperative complications. The success rate was 97.4% for flank pain and 97.4% for hydronephrosis. Post-operative renal scan showed radiological failure in one out of 38 (2.6%) patients, relative success in 2 out of 38 (5.3%) patients and total success in 35 out of 38 (92.1%) of patients.

Conclusion

Laparoscopic redo-pyeloplasty is a feasible procedure for the treatment of recurrent ureteropelvic junction obstruction (UPJO), with a low rate of post-operative complications and a high success rate in high laparoscopic volume centers.

Is One Early Renographic Follow-Up Adequate to Measure the Success of Robotic Pyeloplasty?

PURPOSE

Diuretic renography (DRG) is commonly used to diagnose ureteropelvic junction obstruction (UPJO) and to evaluate the success of surgical repair (pyeloplasty). Duration, frequency, and interpretation of renographic follow-ups are still under dispute.

METHODS

We retrospectively reviewed 94 consecutive patients diagnosed with UPJO who underwent a minimally invasive, robotically assisted laparoscopic pyeloplasty at our institution between January 2009 and September 2015. DRG was carried out preoperatively and again routinely 4 to 6 weeks postoperatively the day after stent removal (early DRG). Patients were scheduled for repeat (late) DRG and follow-up examinations, including clinical status and ultrasonography.

RESULTS

Nineteen patients with missing preoperative DRG were excluded from the study; the remaining 75 patients were eligible for statistical evaluation. At follow-up, 98.7% reported no or only very mild and rare symptoms. On early DRG, 52.5% had T_1/2 ≤ 10 min (unobstructed), 39.3% had T_1/2 between 10 and 20 minutes (equivocal), and 8.2% had T_1/2 ≤ 20 minutes (obstructed). At late follow-up, the DRG results had improved to 80.8% unobstructed with 19.2% remaining equivocal, and no patients were obstructed; thus, the overall success rate was 80.8%. There was only one patient who worsened from unobstructed to equivocal from early to late DRG assessment.

CONCLUSION

In case of complete symptom resolution, a nonobstructive diuretic half-time of ≤10 minutes on early DRG following stent removal suggests that further routine renographic follow-up is unnecessary. Patients with an equivocal early DRG (T_1/2 between 10 and 20 minutes) require further scintigraphic follow-up, as they have a 42.1% chance of staying equivocal.

Laparoscopic pyeloplasty versus open pyeloplasty for recurrent ureteropelvic junction obstruction in children

INTRODUCTION AND OBJECTIVES

Recurrent ureteropelvic junction obstruction (UPJO) in children is an operative challenge. Minimally invasive endourological treatment options for secondary UPJO have suboptimal success rates; hence, there is a re-emergence of interest about redo pyeloplasty. The present study presented experience with laparoscopic management of previously failed pyeloplasty compared with open redo pyeloplasty in children.

STUDY DESIGN

Twenty-four children with recurrent UPJO who underwent transperitoneal dismembered laparoscopic pyeloplasty were studied. Operative, postoperative, and follow-up functional details were recorded and compared with those of open pyeloplasty (n = 15) carried out for recurrent UPJO by the same surgeon during the same study period.

RESULTS

Demographic data were comparable in the laparoscopic and open groups, except for a significantly lower GFR in the open group (24.8 vs 38.2 ml/min, P = 0.0001). Mean time to failure of the original repair was 20.2 months (23.6 months for redo laparoscopic pyeloplasty, 18.8 months for redo open). The success rate of laparoscopic redo pyeloplasty was 91.7 vs 100% in open redo pyeloplasty. Compared with redo open pyeloplasty, the mean operative time was longer (211.4 ± 32.2 vs 148.8 ± 16.6, P = 0.002), estimated blood loss was higher (102 vs 75 ml, P = 0.06), while hospital stay was shorter and pain score was lower in the laparoscopy group (P = 0.02) in the laparoscopic group. There were no intraoperative complications, while the postoperative complication rate was similar in the two groups (20.8 vs 20.0%).

DISCUSSION

Before the laparoscopic approach became a viable option, endopyelotomy was widely used for managing recurrent UPJO. However, the success rate of endopyelotomy for secondary UPJO was approximately 10-25% lower than for open pyeloplasty. Redo pyeloplasty had excellent results, with reported success rates of 77.8-100%. Laparoscopic redo pyeloplasty is becoming a viable alternative to open redo pyeloplasty in many centers with experience in minimally invasive techniques. The present study revealed that redo laparoscopic pyeloplasty appeared to have advantages over redo open surgery, in that it was associated with shorter hospital stay (4 vs 6 days, P = 0.046), reduced postoperative pain score (P = 0.02), and less need for postoperative analgesia (P = 0.001), still with comparable successful outcomes and patient safety. However, the procedure had a longer operative times and more blood loss.

CONCLUSION

Laparoscopic pyeloplasty is a viable alternative to open pyeloplasty in children with recurrent UPJO, with shorter hospital stays and less postoperative pain. However, the procedure is technically demanding and should be attempted in high-volume centers by laparoscopists with considerable experience in laparoscopic reconstructive procedures.

National Trends in Secondary Procedures Following Pediatric Pyeloplasty

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.

An up-to-date overview of minimally invasive treatment methods in ureteropelvic junction obstruction

Introduction

Over the last two decades, minimally invasive treatment options for ureteropelvic junction obstruction have been developed and are bcoming more popular. Multiple series of laparoscopic pyeloplasty have demonstrated high success rates and low perioperative morbidity in pediatric and adult populations, for both the transperitoneal and retroperitoneal approaches. In this review, we aimed to analyze the current status of minimally invasive therapy of ureteropelvic junction obstruction.

Material and methods

A PubMed database search was conducted to examine minimally invasive treatments of ureteropelvic junction obstruction.

Results

A large number of cases have been reported for adult patients, confirming that robotic pyeloplasty represents a viable option for either primary or secondary repair. Comparative studies demonstrate similar success and complication rates between minimally invasive and open pyeloplasty in both the adult and pediatric populations. A clear advantage, in terms of hospital stay, of minimally invasive over open pyeloplasty was observed only in the adult population.

Conclusions

Studies have shown that minimally invasive pyeloplasty techniques are a safe, effective, and feasible in adult and pediatric populations.

Laparoscopic pyeloplasty for secondary ureteropelvic junction obstruction: long-term results

OBJECTIVE

To evaluate the long-term results of laparoscopic pyeloplasty in patients with secondary ureteropelvic junction obstruction after failed primary interventions.

METHODS

Between August 2000 and October 2012, transperitoneal dismembered laparoscopic pyeloplasty was carried out in 13 patients with a surgical history of failed prior surgical interventions. Perioperative outcomes as well as long-term results were assessed. These outcomes were compared with those of the same procedure carried out for primary ureteropelvic junction obstruction by a single surgeon during the same study period.

RESULTS

Laparoscopic transperitoneal pyeloplasty was completed successfully in all cases without converting to open surgery or requiring blood transfusion. The preoperative symptoms in 12 of 13 patients all disappeared soon after the operation. Asymptomatic severe hydronephrosis found in a 2-year-old boy reduced in size postoperatively. When comparing the primary with the secondary laparoscopic pyeloplasty carried out by the same surgeon, the mean operative time was longer (183 vs 241 min, P = 0.002), estimated blood loss was larger (33 vs 66 mL, P = 0.03) and the complication rate was higher (8.8% vs 22.2%, P = 0.01) in the secondary group. Success rates were 97.9% and 100% (P = 0.41) at a mean follow up of 25.9 and 40.0 months (P = 0.14) for the primary and secondary groups, respectively.

CONCLUSIONS

Laparoscopic pyeloplasty is an excellent option for patients who failed previous surgical management. This approach provides durable long-term outcomes comparable with those of primary treatment for ureteropelvic junction obstruction.

Management of secondary pelviureteric junction obstruction

Pelviureteric junction obstruction (PUJO) of the kidney can lead to a number of different clinical manifestations, which often require surgical intervention. Although the success of pyeloplasty and endopyelotomy are good, there are still a number of patients who fail primary treatment and develop secondary PUJO. These treatment failures can be a challenging cohort to manage. This article aims to provide a comprehensive overview on the surgical options available to the urologist for managing secondary PUJO as well as providing some guidance on assessing factors that will influence management decisions.

Prone versus supine lasix renal scan to assess surgical success after laparoscopic and robot-assisted pyeloplasty

PURPOSE

Success after laparoscopic pyeloplasty (LP) for ureteropelvic junction obstruction is determined based on renal scan (RS) results and patient symptoms ± ultrasonography. The upright or prone position during RS may facilitate drainage. This study reports on outcomes after LP and robot-assisted pyeloplasty (RALP) and determines if patient position (supine vs prone) alters the results of the postoperative RS and surgical "success."

PATIENTS AND METHODS

A retrospective review of LP and RALP performed by one surgeon between 2005 and 2012 was performed. Follow-up consisted of RS ± ultrasonography. The paired t test was used to assess for a significant difference between mean T1/2 for supine vs prone scans in each patient. Linear regression was used to determine if preoperative split renal function on the affected side or degree of preoperative hydronephrosis predicted difference in supine vs prone T1/2.

RESULTS

There were 11 LP and 81 RALP performed; 84 had follow-up data. There were four (4.3%) failures. Thirty-eight patients had sufficient supine and prone RS for analysis. The difference in T1/2 between supine and prone RS was significant (mean difference 10.18 ± 27.28 min, P = 0.03). Strict success increased to 65.8% from 44.7% and combined strict plus technical success increased to 78.9% from 63.1% on prone vs supine RS. Split function and degree of hydronephrosis were not predictors of difference in RS results.

CONCLUSIONS

LP and RALP have good technical results. Prone position for RS may facilitate drainage and may be a more accurate representation of postoperative outcome after pyeloplasty, particularly in equivocal cases.

Robot-assisted and laparoscopic repair of ureteropelvic junction obstruction: a systematic review and meta-analysis

CONTEXT

Over the last two decades, minimally invasive treatment options for ureteropelvic junction obstruction (UPJO) have been developed and popularized.

OBJECTIVE

To critically analyze the current status of laparoscopic and robotic repair of UPJO.

EVIDENCE ACQUISITION

A systematic literature review was performed in November 2012 using PubMed. Article selection proceeded according to the search strategy based on Preferred Reporting Items for Systematic Reviews and Meta-analyses criteria.

EVIDENCE SYNTHESIS

Multiple series of laparoscopic pyeloplasty have demonstrated high success rates and low perioperative morbidity in pediatric and adult populations, with both the transperitoneal and retroperitoneal approaches. Data on pediatric robot-assisted pyeloplasty are increasingly becoming available. A larger number of cases have also been reported for adult patients, confirming that robotic pyeloplasty represents a viable option for either primary or secondary repair. Robot-assisted redo pyeloplasty has been mostly described in the pediatric population. Different technical variations have been implemented with the aim of tailoring the procedure to each specific case. The type of stenting, retrograde versus antegrade, continues to be debated. Internal-external stenting as well as a stentless approach have been used, especially in the pediatric population. Comparative studies demonstrate similar success and complication rates between minimally invasive and open pyeloplasty in both the adult and pediatric setting. A clear advantage in terms of hospital stay for minimally invasive over open pyeloplasty was observed only in the adult population.

CONCLUSIONS

Laparoscopy represents an efficient and effective less invasive alternative to open pyeloplasty. Robotic pyeloplasty is likely to emerge as the new minimally invasive standard of care whenever robotic technology is available because its precise suturing and shorter learning curve represent unique attractive features. For both laparoscopy and robotics, the technique can be tailored to the specific case according to intraoperative findings and personal surgical experience.

Efficacy and late complications of laparoscopic pyeloplasty: experience involving 125 consecutive ureters

INTRODUCTION

Laparoscopic pyeloplasty is now widely recognized as a minimally invasive alternative for the surgical management of ureteropelvic junction obstruction. However, there have been insufficient reports describing the long-term outcomes and the stability of the results. In addition, late complications have not been thoroughly discussed.

METHODS

Between October 1999 and December 2010, we performed laparoscopic pyeloplasty on 125 consecutive ureters in 119 patients with an obstruction of the ureteropelvic junction. We performed dismembered Anderson-Hynes pyeloplasty, Fenger plasty and Y-V flap in 108 (86.4%), 15 (12.0%), and 2 ureters (1.6%), respectively.

RESULTS

All procedures were completed successfully. Median operative time was 200 min (range, 80-775 min) and median estimated blood loss was 20 mL (range, 20-250 mL). Intraoperative and postoperative complications categorized as Clavien grade II and III occurred in 11 (8.9%) procedures. Among them, three were observed after 12 months postoperative and all involved renal stones in the collapsed pelvis. In 120 (96%) ureters, hydronephrosis improved and/or obstructive pattern on diuretic renography disappeared during a median follow-up period of 45 months (range, 5-146 months). The degree of hydronephrosis steadily improved for more than 2 years, and re-obstruction was never observed after 1 year postoperative.

CONCLUSION

The efficacy of laparoscopic pyeloplasty seems to be durable over 2 years postoperatively. Because obstruction recurrence was not observed after 12 months postoperative, patients with complete disappearance of hydronephrosis may unnecessarily be followed longer than 2 years. However, cases with persisting hydronephrosis should be regularly monitored because of the remaining possibility of stone formation.

Development of a relational database to capture and merge clinical history with the quantitative results of radionuclide renography

Our objective was to design and implement a clinical history database capable of linking to our database of quantitative results from (99m)Tc-mercaptoacetyltriglycine (MAG3) renal scans and export a data summary for physicians or our software decision support system.

METHODS

For database development, we used a commercial program. Additional software was developed in Interactive Data Language. MAG3 studies were processed using an in-house enhancement of a commercial program. The relational database has 3 parts: a list of all renal scans (the RENAL database), a set of patients with quantitative processing results (the Q2 database), and a subset of patients from Q2 containing clinical data manually transcribed from the hospital information system (the CLINICAL database). To test interobserver variability, a second physician transcriber reviewed 50 randomly selected patients in the hospital information system and tabulated 2 clinical data items: hydronephrosis and presence of a current stent. The CLINICAL database was developed in stages and contains 342 fields comprising demographic information, clinical history, and findings from up to 11 radiologic procedures. A scripted algorithm is used to reliably match records present in both Q2 and CLINICAL. An Interactive Data Language program then combines data from the 2 databases into an XML (extensible markup language) file for use by the decision support system. A text file is constructed and saved for review by physicians.

RESULTS

RENAL contains 2,222 records, Q2 contains 456 records, and CLINICAL contains 152 records. The interobserver variability testing found a 95% match between the 2 observers for presence or absence of ureteral stent (κ = 0.52), a 75% match for hydronephrosis based on narrative summaries of hospitalizations and clinical visits (κ = 0.41), and a 92% match for hydronephrosis based on the imaging report (κ = 0.84).

CONCLUSION

We have developed a relational database system to integrate the quantitative results of MAG3 image processing with clinical records obtained from the hospital information system. We also have developed a methodology for formatting clinical history for review by physicians and export to a decision support system. We identified several pitfalls, including the fact that important textual information extracted from the hospital information system by knowledgeable transcribers can show substantial interobserver variation, particularly when record retrieval is based on the narrative clinical records.