Physiology and evaluation of ureteropelvic junction obstruction

Pelviureteric junction obstruction in adults: A systematic review of the literature

Background

Pelviureteric junction obstruction (PUJO) is a common urological disorder that can present at any stage of life. The underlying etiology in children has been well studied; however, a gap exists in the literature for the adult population. Herein, we performed a systematic review of the literature to evaluate the current evidence on the underlying etiologies of adult patients presenting with PUJO.

Materials and methods

Four electronic databases were searched for relevant studies assessing the underlying etiologies of pelviureteric junction obstruction in adults. Studies were assessed for eligibility based on predefined inclusion and exclusion criteria, and a critical appraisal of methodological quality and risk of bias was performed. Finally, qualitative and quantitative data analyses were performed.

Results

Twelve studies comprising a total of 513 patients with radiologically confirmed PUJO met the inclusion criteria and were included in our analysis. The most common finding was crossing vessels, which were observed in 50.5% of patients, followed by intrinsic ureteral stenosis (27.1%), adhesions (15.3%), and high insertion of the ureter (10.1%).

Conclusions

The underlying etiologies of PUJO in adults remain unclear. This study indicated that obstruction secondary to crossing vessels is the most common cause of obstruction in adults and occurs more frequently than in the pediatric population.

Learning robotic pyeloplasty without simulators: an assessment of the learning curve in the early robotic era

OBJECTIVE

To analyze our experience and learning curve for robotic pyeloplasty during this robotic procedure.

METHODS

Ninety-nine patients underwent 100 consecutive procedures. Cases were divided into 4 groups of 25 consecutive procedures to analyze the learning curve.

RESULTS

The median anastomosis times were 50.0, 36.8, 34.2 and 29.0 minutes (p=0.137) in the sequential groups, respectively. The median operative times were 144.6, 119.2, 114.5 and 94.6 minutes, with a significant difference between groups 1 and 2 (p=0.015), 1 and 3 (p=0.002), 1 and 4 (p<0.001) and 2 and 4 (p=0.022). The mean hospital stay was 7.08, 4.76, 4.88 and 4.20 days, with a difference between groups 1 and 2 (p<0.001), 1 and 3 (p<0.001) and 1 and 4 (p<0.001). Clinical and radiological improvements were observed in 98.9% of patients. One patient presented with recurrent obstruction.

CONCLUSIONS

Our results demonstrate a high success rate with low complication rates. A significant decrease in hospital stay and surgical time was evident after 25 cases.

Laparoscopic single-incision triangulated umbilical surgery (SITUS) pyeloplasty: a description of the first 32 cases

INTRODUCTION AND OBJECTIVES

Transumbilical laparoendoscopic (LESS) procedures reduce access trauma. Laparoendocopic single-incision triangulated umbilical surgery (SITUS) utilizes straight instruments in a triangulated fashion, via three trocars placed through a single umbilical incision.

METHODS

Thirty-two consecutive patients underwent an SITUS pyeloplasty. Access is performed by incision of the umbilical fold by 3/4 of its circumference, a 5-mm camera port, and consequently, cranial and caudal 3 or 5 mm working trocars are placed at a distance of 3-6 cm, thus allowing triangulation. SITUS laparoscopy utilizes the standard straight instruments with a length of 43 cm.

RESULTS

All procedures were successfully performed and no conversion to open, or conventional laparoscopic approach was deemed necessary. Thirty patients underwent a dismembered and two a Fenger pyeloplasty. A crossing vessel was identified in 68.75% of the cases. The median laparoscopic and suturing times were 130 and 30 min, respectively; median blood loss was 50 ml. The median duration of hospitalization was 4 days. The visual analogue scores (VAS) reported were 1 on the first and 0 on the third postoperative day. The indwelling double-J or mono-J stents were removed after a median time of 5 weeks and 4 days, respectively. The overall success rate was 96.8%.

CONCLUSIONS

The SITUS technique for pyeloplasty is an attractive alternative to conventional laparoscopy and a viable competitor to LESS surgery. It combines the common principles of traditional laparoscopy, such as conventional instrumentation and triangulation, with the benefits of single-port surgery.

(99m) T c-DTPA Study to Validate an Experimental Model of Ureteral Obstruction in Rabbits: Preliminary Results

Objective. To create a ureteral obstruction experimental model that can be proved through (99m)Tc-DTPA renal scintigraphy and histopathological studies, without causing total renal function loss. Materials and Methods. Ten New Zealand white rabbits were submitted to a surgical experiment to create a model of unilateral obstruction to urinary flow. Surgery procedure provided unilateral ureteral obstruction (left kidney) to urinary flow and posteriorly was evaluated by (99m)Tc-DTPA renal scintigraphy and histopathological study. (99m)Tc-DTPA renal study was performed to detect and quantify signs of obstruction and to evaluate renal function. Statistical analysis was performed through the Student t-test with a significance level of P<0.05. Results. Nine of the ten rabbits presented left renal unit obstruction and one nonobstructive on the (99m)Tc-DTPA and histopathological studies. All the right renal units, which were not submitted to surgical procedure, were nonobstructed by the studies. There was a general agreement between scintigraphy and histopathological results in both groups. Conclusion. The experimental model promoted the creation of ureteral obstruction in rabbits, confirmed by nuclear medicine scintigraphy and histopathology, and could be used in further studies to better understand urinary obstruction.

A novel quantitative method for measuring obstruction in the upper urinary tract: the 'obstruction coefficient'

OBJECTIVES

To define an exact pressure-flow correlation in the upper urinary tract using an improved measurement method, to quantitatively characterize the degree of postrenal obstruction and to find a simple way of calculating it in everyday urological practice.

METHODS

The data of 112 cases were included in the analysis. The dynamic method of a multistep, constant pressure perfusion study was used to precisely measure a wide range of pressure-flow dependences. Values of established parameters measuring the degree of obstruction were compared: the intrapelvic pressure, the ureteral opening pressure and the newly introduced 'obstruction coefficient'.

RESULTS

Pressure-flow relations can be best presented by a parabolic curve described by the simple formula Y = AX(2) + B. Depending on the degree of obstruction, the shape of this curve can be characterized by a single number, that we defined as the 'obstruction coefficient'. Computer-based evaluation software for the easy calculation of this coefficient is presented here and freely available on demand. The Whitaker-test, the ureteral opening pressure, and the 'obstruction coefficient' showed significant correlation proving that the latter was clinically applicable in measuring the degree of obstruction.

CONCLUSION

Calculation of the 'obstruction coefficient' enables us to exactly define the degree of upper urinary tract obstruction and to safely monitor for a long period conditions inhibiting ureteric passage.

The use of endoluminal ultrasonography for preventing significant bleeding during endopyelotomy: evaluation of helical computed tomography vs endoluminal ultrasonography for detecting crossing vessels

OBJECTIVE

To evaluate, in a prospective study, the efficiency of helical computed tomography (CT) and endoluminal ultrasonography (ELUS) for detecting significant crossing vessels, a major cause of bleeding complications when treating patients with pelvi-ureteric junction (PUJ) obstruction, and to compare our results using ELUS with those of an earlier multicentre study (not using ELUS), to see whether the complication rate decreased.

PATIENTS AND METHODS

The study included 27 patients with a PUJ who had isotope renography, intravenous urography, helical CT and ELUS before surgery. Depending on the findings of ELUS, patients were treated with a pure lateral Acucise incision (Applied Medical, Irvine, CA, USA) an Acucise with changed cutting direction, or (later) a laparoscopic pyeloplasty.

RESULTS

ELUS detected 15% more crossing vessels than helical CT; 16 patients had Acucise (seven lateral, nine other cutting direction), eight were treated with a laparoscopic pyeloplasty and three with other procedures. By contrast with earlier reports and as a consequence of using ELUS, there was no bleeding, vs 16% in the study not using ELUS. The success rate of 73% of the endourological approach is comparable with previous reports.

CONCLUSION

ELUS is more sensitive in detecting relevant crossing vessels than helical CT and therefore the use of ELUS can better prevent bleeding complications. ELUS can also improve the success rate by helping in selecting the correct treatment. Because it is minimally invasive and safe, ELUS combined with Acucise (or other possible endourological techniques, like holmium laser incision) should be the first choice of treatment for PUJ stenosis.

Ureteropelvic Junction Obstruction: Some new Acquisitions about Etiology, Pathophysiology and Diagnostics

The etiopathogenesis of uretero-pelvic junction obstruction (UPJO) has been the subject of many speculations and it remains, in some ways, a debatable matter. Some recently reported thorough research refer to neuro-mediated pathogenetic mechanisms rather than (or together with) myogenic ones.

Advances in US, radioisotopic functional imaging, CT and RM contribute to differentiate the obstructive conditions from the non-obstructive ones and to afford today a better assessment of renal functional damage. Particularly, diuretic renography is a non-invasive test for characterization of the renal functional abnormalities resulting from UPJO. Helical CT with angiography is a useful technique for identification of crossing vessels (pyelo-vascular tangle) which can be used for the pre-surgical planning of endopyelotomy. Endoluminal ultrasonography can be used to guide the position of the incision for endopyelotomy (US-guided endopyelotomy).

Laboratory examinations are important to determine the overall renal function (serum creatinine, acid-base balance, serum electrolytes, etc.), urinary MCP-1 and NAG (markers of tubular damage), and to rule out urinary tract infections.

The management of UPJO (watchful waiting; either open or laparoscopic dismembered pyeloplasty; endoluminal procedures) is greatly influenced by the diagnostic evaluation.

The paper aims to outline the advances in both physiopathology and diagnostics of UPJO on the basis of a review of the literature.

Renal Doppler ultrasonography in infants with hydronephrosis

The objective was to evaluate the importance of obstruction in unilateral hydronephrosis by using renal Doppler ultrasonography. A total of 19 infants were examined. It was revealed that patients of group with obstruction have in the affected kidney a higher mean resistive index [RI = 0.77 +/- 0.04] than in the healthy kidney [RI = 0.69 +/- 0.02] [p < 0.001]. In patients of group with nonobstructive dilatation this difference was not observed. In infants it is not possible to evaluate only absolute changes of the resistive index. It is much more useful to compare values of RI of both kidneys using the above indices. The determination of RI, RIR and delta RI can be helpful in distinguishing obstructed from non-obstructed hydronephrosis.

Resistive index in rabbits with experimentally induced hydronephrosis: effect of furosemide

RATIONALE AND OBJECTIVES

The purpose of this study in rabbits was to evaluate the effect of furosemide on resistive index (RI) in the diagnosis of partial hydronephrosis.

MATERIALS AND METHODS

In 14 rabbits the left ureter was ligated by being tied to an angiographic guide wire. Doppler sonography was performed before and 1 and 6 hours, 1 and 3 days, and 1, 2, and 4 weeks after ureteral ligation. At each interval it was performed both before and after intravenous injection of saline and furosemide. RIs were compared (a) between obstructed and contralateral kidneys and (b) before and after furosemide administration, and the statistical significance of any differences was determined.

RESULTS

Obstructed kidneys had significantly higher RIs than the contralateral kidneys before furosemide administration at five of seven postligation measurements and after furosemide administration at all seven. The differences between obstructed and contralateral kidneys were significantly higher after furosemide administration (P < .05). The increase in RI after furosemide administration was significantly greater in obstructed than in contralateral kidneys (P < .05).

CONCLUSION

The results in a rabbit model indicate that Doppler sonography with furosemide administration is a valuable method for evaluating hydronephrosis. The administration of furosemide accentuates the difference in RI between obstructed and nonobstructed kidneys.

Endopyelotomy failure is associated with reduced urinary transforming growth factor-beta1 levels in patients with upper urinary tract obstruction

BACKGROUND AND PURPOSE

We previously demonstrated that obstructed ureteropelvic junction (UPJ) segments from patients who had secondary pyeloplasty after endopyelotomy failure expressed transforming growth factor-beta1 (TGF-beta1) at levels significantly lower than patients who had primary pyeloplasty. In order to determine whether these differences in secreted TGF-beta1 are detectable preoperatively in the urine, the TGF-beta1 concentration of urine from patients undergoing endopyelotomy was determined and compared with that from subjects without urologic disease.

MATERIALS AND METHODS

Bladder and renal pelvic urine from the obstructed side was obtained from patients (N = 34) undergoing primary endopyelotomy for UPJ obstruction. Bladder urine was also obtained from sex- and age-matched patients (N = 26) having no evidence of urinary tract obstruction. The TGF-beta1 concentration was determined by ELISA and normalized to the creatinine concentration.

RESULTS

The bladder urine TGF-beta1 concentration was significantly (P < 0.02) higher in patients with UPJ obstruction (86.1+/-20.5 pg/mg of creatinine) than in those without obstruction (29.7+/-8.0 pg/mg creatinine). The TGF-beta1 concentration in the bladder urine of patients who underwent endopyelotomy and later returned because of UPJ obstruction (25.7+/-12.3 pg/mg of creatinine; N = 6) was not significantly different from the value in unobstructed patients but was significantly lower (P < 0.01) than in patients for whom endopyelotomy was successful (100+/-24.29 pg/mg of creatinine; N = 28). The renal pelvic urinary TGF-beta1 concentration was higher in patients for whom endopyelotomy was successful (772+/-490.1 pg/mg of creatinine) than in patients who underwent endopyelotomy and later returned because of UPJ obstruction (126.1+/-41.9 pg/mg of creatinine).

CONCLUSIONS

These data suggest that preoperative concentration of TGF-beta1 in the bladder urine of patients with UPJ obstruction who fail endopyelotomy is not significantly different from that in subjects with no urologic disease and significantly lower than in those patients for whom endopyelotomy is successful. Thus, the preoperative bladder urine concentration of TGF-beta1 may assist in selecting patients for this operation, although further investigation is necessary.

Utility of the resistance index ratio in differentiating obstructive from nonobstructive hydronephrosis in children

PURPOSE

We assessed the utility of the resistance index ratio (RIR) in distinguishing between obstructive and nonobstructive upper urinary tract dilatation in children.

METHODS

Twenty-three children (7 days-14 years old) with unilateral dilated collecting systems and a contralateral normal kidney were prospectively evaluated by duplex Doppler sonography. We measured the resistance index (RI) of the intrarenal arteries and calculated the RIR. Ninety-six normal kidneys in 48 controls were also evaluated.

RESULTS

Twelve kidneys were proved to be obstructed at the ureteropelvic junction, and 11 were found by renal scintigraphy with furosemide and/or by surgery to have nonobstructive dilatation. The mean RIR differed significantly between the obstructed and dilated nonobstructed kidneys (1.16+/-0.04 versus 1.04+/-0.04, respectively; p < 0.01). After surgical correction of ureteropelvic junction obstruction, the obstructed kidneys showed significant drops in the RIR (1.18+/-0.03 to 1.07+/-0.03, p < 0.01). The RIR showed no statistically significant relationship with age (r = -0.268, p > 0.01); however, the RI declined with increasing age (r= -0.414, p < 0.01). An RIR cut-off value of > or = 1.10 provided a good discriminatory level, resulting in a sensitivity of 92%, a specificity of 97%, a positive predictive value of 85%, and a negative predictive value of 97%.

CONCLUSIONS

An RIR cut-off value of > or = 1.10 appears to be an effective parameter for evaluation and follow-up of unilateral obstructive hydronephrosis in children.

Endopyelotomy failure is associated with reduced transforming growth factor-beta

PURPOSE

Approximately 15% of patients with ureteropelvic junction obstruction have endopyelotomy failure and require an additional surgical procedure to remove the obstruction. Transforming growth factor-beta (TGF-beta), a cytokine which stimulates mesenchymal cell proliferation and extracellular matrix deposition, increases in the renal pelvis in response to obstruction. However, TGF-beta also is implicated in smooth muscle regeneration and wound healing. To understand the pathophysiology of ureteropelvic junction obstruction and determine why endopyelotomy fails in some obstructed ureteropelvic junctions, TGF-beta expression in obstructed and normal ureteropelvic junction segments was compared.

MATERIALS AND METHODS

Immunohistochemical staining using a rabbit polyclonal anti-TGF-beta was performed on deparafinfized 4 microm. sections of paraffin blocked ureteropelvic junction segments. Human obstructed ureteropelvic junction segments were removed during primary pyeloplasties (11) and secondary pyeloplasties after endopyelotomy failure (11). Normal ureteropelvic junction segments were removed during nephrectomy for purposes unrelated to obstruction (11). Grading on a scale of 0 to 4 was performed by a physician blinded to the source of the specimen.

RESULTS

Mean TGF-beta expression plus or minus standard error of the mean was significantly increased (p <0.02) in obstructed ureteropelvic junctions from primary pyeloplasties (2.6+/-0.7) compared to normal ureteropelvic junctions (1.6+/-0.7), as expected. However, TGF-beta expression in the endopyelotomy failure group (1.8+/-0.6) was not significantly different from that in normal ureteropelvic junctions and was significantly lower (p <0.05) than that in obstructed ureteropelvic junctions from primary pyeloplasties.

CONCLUSIONS

Obstructed ureteropelvic junctions in cases of endopyelotomy failure have decreased expression of TGF-beta compared with other obstructed ureteropelvic junctions. These data suggest that an elevation of TGF-beta in obstructed ureteropelvic junctions may be necessary for successful tissue repair after endopyelotomy.

Laser endopyelotomy: minimally invasive therapy of ureteropelvic junction stenosis

Endoscopic pyelotomy is a minimally invasive procedure that is increasingly used for the management of ureteropelvic junction (UPJ) obstruction. We report the results and advantages in the management of UPJ obstruction using a ureteroscopic retrograde laser-assisted approach (laser endopyelotomy; LEP). Thirty-four patients were treated between December 1994 and June 1997 by this new technique. Twenty-seven obstructions were primary. The mean time of follow-up is 18 months. An indwelling ureteral catheter was placed 3 weeks prior to treatment. Intraoperatively, after the removal of the stent, a guidewire was passed across the stenosis, and the ureter was entered with a semirigid ureteroscope. The LEP was then performed under visual control using a contact laser fiber until all obstructive fibers had been cut. Follow-up examinations included sonography, intravenous urography, and, in unclear cases, a radionuclide renal scan with furosemide application after 3 months. The success rate was 85%. The most important factor influencing the outcome was the grade of hydronephrosis. Postoperative side effects have been minimal, and minor complications occurred in only 5 patients (15%). Laser endopyelotomy is a minimally invasive procedure with less morbidity for the treatment of UPJ obstruction. Only patients with a severe extrinsic cause of obstruction should be excluded from this technique. These cases can be approached laparoscopically.

Endopyelotomy after failed pyeloplasty: the long-term results

PURPOSE

Endopyelotomy has been proposed as a technique to treat ureteropelvic junction obstruction after failed open pyeloplasty. However, to our knowledge no long-term results of this treatment have been reported. We report the long-term followup of a cohort of patients in whom pyeloplasty failed and who subsequently were treated with endopyelotomy.

MATERIALS AND METHODS

From January 1985 to February 1996, 72 patients in whom open surgical pyeloplasty failed were treated with percutaneous endopyelotomy. Mean patient age was 35 years (range 5 to 82). The interval between pyeloplasty and subsequent failure ranged from 2 months to 30 years (mean 57 months). The major presenting symptoms were pain in 82% of cases, fever and urinary tract infections in 37.5%, stone formation in 25% and gross hematuria in 21%.

RESULTS

Antegrade endopyelotomy using a hooked knife was performed in all patients with no unusual difficulty and minimal complications. A total of 63 patients (87.5%) had long lasting clinical and radiographic treatment success after a mean followup of 88.5 months. Of the 9 endopyelotomy failures (12.5%) 7 (77.8%) were detected immediately after stent removal at 6 weeks, 1 (11.1%) at 6 months and 1 (11.1%) at 10 months postoperatively (mean failure interval 3.3 months). The failures were corrected with repeat endopyelotomy in 1 patient, pyeloplasty in 3, ileal interposition in 1 and nephrectomy in 4.

CONCLUSIONS

Endopyelotomy is the treatment of choice for recurrent ureteropelvic junction obstruction after failed pyeloplasty, with a high and sustained long-term success rate and no reported new failures after 1-year followup. Furthermore, endopyelotomy is technically easier with less morbidity than repeat open pyeloplasty.

Helical CT and CT angiography for the identification of crossing vessels at the ureteropelvic junction

In comparison with pyeloplasty, endourologic procedures for the treatment of ureteropelvic junction obstruction offer good success rates with less morbidity and a shorter hospitalization; however, studies have found lower success rates and increased complications in patients with crossing vessels. Conventional diagnostic angiography and intravenous urography have both been used to identify crossing vessels at the UPJ; but, a reliable, less invasive, less costly, and simpler preoperative procedure to identify crossing vessels is needed. Helical CT with CT angiography is a promising noninvasive technique for the identification of crossing vessels at the ureteropelvic junction, which can be used for surgical planning of endourologic treatment of UPJ obstruction.

Prenatal diagnosis. Therapeutic implications

Prenatal diagnosis of structural anomalies provides the opportunity to influence the postnatal outcome. The greatest value of antenatal screening is, in fact, the awareness of the urogenital abnormalities, such as presumed UPJ obstruction, so that appropriate investigation and treatment can be offered immediately after birth and before permanent damage occurs owing to obstruction or infection. Crombleholme and coworkers reported that prenatal consultation impacted favorably on outcomes by preventing early termination of pregnancy owing to misconceptions about the existing condition. It also permitted delivery of complex cases in a tertiary care setting, thereby preventing a delay in postnatal management. A systematic approach to the infant in the prenatal and postnatal periods is important. The natural history of prenatally detected hydronephrosis continues to be defined, and there is no ideal test to predict the outcome of UPJ obstruction. Several investigators are evaluating various markers in urine that may help to identify fetuses who require early postnatal intervention. More complete understanding regarding the natural history of unilateral pediatric UPJ obstruction and its response to surgery will not be available until several randomized, prospective clinical studies are completed. The collaborative effort of obstetricians, neonatologists, geneticists, radiologists, and pediatric urologists should provide answers to many questions surrounding prenatally diagnosed UPJ obstruction.