Microanatomy and morphometry of the hydronephrotic "obstructed" renal pelvis in asymptomatic infants

Clues for the early loss of renal function in congenital hydronephrosis: Analysis of renal pelvis collagen ratio, diuresis renography and upper urinary tract morphology

INTRODUCTION

Diagnosing real urinary obstruction and surgical decision making for the operative correction of urinary obstruction, are still problematic in congenital hydronephrosis (CH). Compliance of the renal pelvis is one of the important defense mechanisms of renal parenchyma against urinary obstruction. We observed early loss of function in some cases of CH with low and moderate anteroposterior diameter of the renal pelvis (APDRP).

OBJECTIVE

To evaluate structural properties of the renal pelvic tissue of patients with CH and the relation of these structural properties with renal function and Anteroposterior diameter of the renal pelvis.

STUDY DESIGN

Ureteropelvic junction (UPJ) excised during UPJ obstruction operations from 2013 to 2019 were evaluated histopathologically. The patients were divided into the two groups according to initial renal function, i.e. group with initial preoperative differential renal function (DRF) less than 35% and group with initial DRF greater than 35%. The percentage of collagen to whole tissue area were analyzed using image processing program. The relationship between DRF and tissue collagen ratio, SFU and APDRP was evaluated.

RESULTS

There were 5 patients in the DRF <35% group and 16 patients in the DRF >35% group. However, APDRP's of the DRF <35% group were also significantly lower than the DRF >35% group. The collagen distribution in the muscle layer was more prominent in the DRF <35% group. Proportionally, percentage of collagen stained surface was significantly higher in DRF <35% group.

DISCUSSION

There are numerous histopathological studies evaluating the cause of UPJ obstruction. Besides these studies that are oriented to etiology, there are many studies comparing the histopathological changes at UPJ with surgical outcome and prognosis. In the present study, we found that renal pelvis collagen ratio was significantly increased in patients with lower APDRP and with severe renal function loss. This increase in the collagen content in the renal pelvis have been shown to affect the compliance negatively and decrease APDRP, which leads to a faster loss of renal function. Thus, pelvic structural changes accompanying UPJ obstruction may aggravate urinary obstructive process.

CONCLUSION

Increased renal pelvis collagen ratio negatively affects the expansion of the renal pelvis, which is one of the protective mechanisms of the renal parenchyma, and may be one of the triggering mechanisms of early loss of renal function.

Embryology and Morphological (Mal)Development of UPJ

Kidney parenchyma and collecting system arise from two different embryologic units as a result of a close interaction between them. Therefore, their congenital abnormalities are classified together under the same heading named CAKUT (congenital abnormalities of the kidney and urinary tract). The pathogenesis of CAKUT is thought to be multifactorial. Ureteropelvic junction obstruction (UPJO) is the most common and most investigated form of CAKUT. Despite years of experimental and clinical research, and the information gained on the embryogenesis of the kidney; its etiopathogenesis is still unclear. It involves both genetic and environmental factors. Failure in development of the renal pelvis, failure in the recanalization of ureteropelvic junction, abnormal pyeloureteral innervation, and impaired smooth muscle differentiation are the main proposed mechanisms for the occurrence of UPJO. There are also single gene mutations like AGTR2, BMP4, Id2 proposed in the etiopathogenesis of UPJO.

Renal pelvis reduction during dismembered pyeloplasty: is it necessary?

OBJECTIVE

To compare treatment results in patients who underwent pyeloplasty with and without pelvic reduction for ureteropelvic junction obstruction (UPJO).

METHODS

This randomized prospective study involved 40 patients, all diagnosed with unilateral UPJO; 20 each were randomly selected to undergo open dismembered pyeloplasty with pelvic reduction (group A) or pelvis-sparing pyeloplasty (group B). Patients were evaluated with ultrasound and DPTA renography scans 6 months postoperatively. Mean follow-up was 9 months.

RESULTS

The mean age in group B was 5.71 ± 6.36 years; in group A it was 4.81 ± 6.78 years. There was a decrease in mean anteroposterior renal pelvic diameter (from 49.9 to 26.35 ± 0.949 mm in A and 50.9 to 30.8 ± 1.556 mm in B) with improvement of split renal function (from 39 ± 22.47% to 42.4 ± 22.13% in A and 34.92 ± 16.79% to 38.8 ± 19.66% in B), glomerular filtration rate (from 37.25 ± 15.33 to 41.7 ± 19.34 ml/min in A and 31.3 ± 18.50 to 38.1 ± 23.23 ml/min in B) and draining curves on the 6-month scans, but without any significant difference between groups (p > 0.05). Two cases in group A and three in group B needed redo pyeloplasty, but without any significant difference in failure rate.

CONCLUSION

Excision of the pelvis is not necessary in dismembered pyeloplasty procedures. We had similar surgical outcomes for patients with or without pelvis reduction.

Immunohistochemical and morphometric evaluation of neuronal dysfunction in pelviureteral junction obstruction

PURPOSE

The pathophysiology of pelviureteral junction obstruction remains unclear. In this study, we attempted to evaluate the neuronal dysfunction using immunohistochemical and morphometric parameters.

MATERIALS AND METHODS

Using specific antibodies, we studied the neuronal markers and morphometry of specimens from 10 cases of pelviureteral junction obstruction and 10 normal pelviureteral junctions by immunohistochemistry using synaptophysin (synaptic vesicle membrane protein), S-100 (nerve cell fiber marker), protein gene product 9.5 (neuron specific protein) and CD-117 (transmembrane receptor with tyrosine kinase activity).

RESULTS

In pelviureteral junction obstruction, smooth muscle thickness was significantly higher than in normal specimens. Cytoplasmic cells stained by synaptophysin were found in the pelviureteral junction obstruction specimens but were absent in normal pelviureteral junction specimens. In addition, significantly more intense staining for S-100 was found in the pelviureteral junction obstruction specimens compared with the normal specimens. Immunohistochemical staining for protein gene product 9.5 showed no differences between the normal and pelviureteral junction obstruction specimens. Neither the normal specimens nor pelviureteral junction obstruction groups were stained by CD-117.

CONCLUSION

We propose that the cause of neuronal dysfunction in pelviureteral junction obstruction depends on the increase in number and structure of neuronal cells and smooth muscle thickness. These factors could play an important role in the pathophysiology of pelviureteral junction obstruction by affecting motility and peristalsis.

The distribution of interstitial cells of Cajal in congenital ureteropelvic junction obstruction

Purpose

The authors analysed the distribution of c-kit-positive interstitial cells of Cajal (ICCs) in obstructed ureteropelvic junction (UPJ) and its age-related changes.

Methods

Twenty specimens were obtained from children with intrinsic ureteropelvic junction obstruction (UPJO), at the average age of 8.1 years (8 months–16.8 years), fixed in formalin and embedded in paraffin. Five control samples were taken from children at the average age of 2.3 years (2.4 months–7.4 years). All specimens were analysed by the immunohistochemistry test with light microscopy with respect to c-kit expression. The distribution of c-kit-positive ICCs in the two groups was compared and the correlation between the distribution of c-kit-positive ICCs and the patients’ age in UPJO cases was analysed. The results were examined by Yates’ χ² test, Mann–Whitney U test, and t test for Pearson’s correlation coefficient. A P value < 0.05 was considered as statistically significant.

Results

No statistically significant differences were found in the distribution of c-kit-positive ICCs between UPJO and the control group. No correlation was established between the age of patients with UPJO and the distribution of c-kit-positive ICCs.

Conclusion

No distributional difference found in obstructed and unobstructed UPJ seems to indicate that UPJO is not associated with anomalous distribution of c-kit-positive ICCs. Age-related changes in the expression of c-kit-positive ICCs are equally distributed in obstructed UPJ.

Changes in interstitial cell of Cajal-like cells density in congenital ureteropelvic junction obstruction

PURPOSE

The authors examined the number of interstitial cells of Cajal-like cells (ICC-LCs) in obstructed ureteropelvic junction (UPJ) in comparison with normal UPJ specimens and age-related changes.

MATERIALS AND METHODS

A total of 20 human formalin fixed, paraffin-embedded specimens of intrinsic UPJO from children at the mean age of 8.1 years (age range: 8 months-16.8 years) and 5 control samples from children at the mean age of 2.3 years (range 2.4 months-7.4 years) were investigated immunohistochemically for the expression of c-kit proto-oncogene by light microscopy with computerized image analysis. The results were examined by Fisher's exact test, Yates' chi-square test, and t test for Pearson's correlation coefficient. A P value less than 0.05 was considered statistically significant.

RESULTS

The number of ICC-LCs-dense fields was significantly higher in UPJO specimens in comparison with the normal group (P = 0.0004). The number of ICC-LCs-sparse fields was significantly lowered in UPJO specimens in comparison with the normal group (P = 0.0122). There was no significant difference in the number of ICC-LCs-medium fields in obstructed and normal UPJ specimens. The number of ICC-LCs was decreasing significantly with increasing age of the patients with UPJO (P = 0.0038).

CONCLUSIONS

The higher density of c-kit-positive ICC-LCs in UPJ may manifest the compensation of altered peristalsis in UPJO. The number of ICC-LCs-dense fields decreasing with age may show the failure of compensation and regression of the compensatory changes.

Pelvic reduction during pyeloplasty for antenatal hydronephrosis: does it affect outcome in ultrasound and nuclear scan postoperatively?

OBJECTIVE

To compare ultrasound (US) scan and nuclear renography findings in patients who underwent pyeloplasty with and without pelvic reduction in a randomized prospective study.

METHODS

A total of 42 patients, all prenatally diagnosed with unilateral hydronephrosis, were included. Hydronephrosis was confirmed postnatally. Twenty patients were randomly selected to undergo pyeloplasty with pelvic reduction and 22 underwent pelvis-sparing pyeloplasty. Patients were evaluated with mercaptoacetyltriglycine-3 scans on the sixth month and US scans on the first, third, and sixth months, postoperatively. Mean follow-up was 37 +/- 5.6 weeks. Statistical analyses were performed using chi-square test and significance was set as P <.05. Power analyses were performed by the NCSS-PASS program. Power value of 0.84 was calculated for a sample size of 42.

RESULTS

The anteroposterior pelvic diameter decreased significantly in the pelvic reduction group compared with pelvis-sparing group in the first- and third-month US scans. However, the difference was not significant in the sixth month. The improvements in the US findings for the pelvis-sparing group match with those of the pelvic reduction group later in the postoperative period. Pelvic reduction significantly improved the renal washout time (T(1/2)) in mercaptoacetyltriglycine-3 renography when compared with pyeloplasty group without reduction at postoperative sixth month. Differential renal function was found to be unaffected from pelvic reduction.

CONCLUSIONS

Resolution of anteroposterior diameter in US scan is more prominent in the pelvic reduction group at earlier stages of the postoperative period. Although T(1/2) decreases more prominently in the pelvic reduction group, the utility of this procedure is still indecisive. This feature can reveal possible surgical failures earlier and strengthen the values of US and renography postoperatively.

Bypass pyeloplasty: description of a procedure and initial results

INTRODUCTION AND OBJECTIVE

Dismembered pyeloplasty is the surgical technique of choice for open, laparoscopic and/or robot-assisted repair of ureteropelvic junction obstruction (UPJO). We describe a new technique, bypass pyeloplasty, ideally suited for the high inserting ureter, and present initial results.

PATIENTS AND METHODS

A wide 1-2-cm side-to-side anastomosis is created between the dilated and elastic portion of the ureter just distal to the UPJO and the lower and dependent portion of the hydronephrotic renal pelvis. The UPJ is not disturbed and the renal pelvis is not surgically reduced. Since 2004, of 27 patients requiring surgery for UPJO, 7 underwent bypass pyeloplasty. The indications for surgery included increasing hydronephrosis or decreasing individual renal function in four, pain in two and pyelonephritis in one. The remaining 20 underwent a classic dismembered pyeloplasty.

RESULTS

During a mean follow-up of 26 months, the anteroposterior diameter of the repaired kidney decreased by a mean of 55%. The individual renal function in the repaired kidney improved in two and remained stable in the remainder.

CONCLUSION

These favorable initial results justify further exploration of this simplified technique and its adaptation for laparoscopic and robot-assisted approaches. Bypass pyeloplasty may be a more physiologic procedure in patients with mid to high insertion of the ureter.

Relation between radionuclide imaging and pathologic findings of ureteropelvic junction obstruction in neonatal hydronephrosis

OBJECTIVE

An excessive amount of collagen fibers around the muscle cells in the ureteropelvic junction could be responsible for obstruction in patients with hydronephrosis. We aimed to elucidate the ultrastructure of the ureters and correlate this finding with the prognostic outcome and to correlate the histopathological findings with diuretic radionuclide renography findings.

MATERIAL AND METHODS

Biopsy specimens of 20 children who underwent dismembered pyeloplasty for ureteropelvic junction obstruction were analyzed. The patients were grouped according to their age: infants (<12 months) and others (>12 months). Diuretic radionuclide imaging was performed using (99m)Tc mercaptylacetyltriglycine in the pre- and postoperative periods. Changes in differential renal function and excretion patterns on diuretic renography were evaluated in relation to the findings noted on histopathological examination of the biopsy specimens. Excretion patterns were classified as follows: A, normal; B, responsive to diuretic; C, minimal response to diuretic with some excretion after postural change; and D, very poor/no drainage despite diuretics. Biopsy materials were analyzed for the presence and extent of inflammation, fibrosis and changes in the smooth muscle layer using Masson's trichrome stain and immunohistochemical staining. Histopathological findings were graded from zero to three, depending on severity.

RESULTS

In patients aged <12 months, preoperative differential renal function (DRF) was associated with fibrosis (F) and smooth muscle hypertrophy (SMH) [mean (SD) DRF for both F and SMH were Grade 0-1, 47.8% (6.4%); Grade 2-3, 36.2% (11.3%); p<0.05]; and change in DRF was associated with inflammation [Grade 0-1, -0.1% (4.0%); Grade 2-3, 5.8% (3.0%); p<0.05]. Excretion patterns or improvement in excretion were not associated with any of the histopathological features. Change in DRF was significantly associated with inflammation Grade 2-3 (beta coefficient, 5.8; 95% CI 1.4-10.3).

CONCLUSIONS

Histopathological evaluation of renal parenchymal biopsy specimens obtained during pyeloplasty may be useful to provide an objective method for predicting the recovery of renal function. In addition, this will allow comparison of the types of histopathological alterations with the changes in differential renal function in order to predict the potential final improvement.

Upper urinary tract dilatation: prenatal diagnosis, management and outcome

Upper urinary tract dilatation is one of the most common abnormalities detected on prenatal ultrasound scanning. It is commonly due to transient urine flow impairment (UFI) at the level of the pelvi-ureteric and vesico-ureteric junctions, which improves with time in most cases. It is usually in the neonatal period that the diagnosis is confirmed and during the first 18 months of life that the prognosis of the dilatation is defined.

Glial cell line-derived neurotrophic factor and synaptophysin expression in pelviureteral junction obstruction

OBJECTIVES

To examine the expression of neuronal markers in congenital pelviureteral junction (PUJ) obstruction as a causative factor. The findings from some investigations have suggested that defective neuronal innervation may play an important role in the pathogenesis of PUJ obstruction.

METHODS

Using specific antibodies, we studied the neuronal markers of specimens from 12 cases of PUJ obstruction and 10 normal PUJs by immunohistochemistry using glial cell line-derived neurotrophic factor (GDNF), synaptophysin, S-100, and neurofilament.

RESULTS

In the PUJ obstruction specimens, staining with hematoxylin-eosin and Masson's trichrome revealed muscular hypertrophy and an increase in collagen tissue and fibrosis in the lamina propria and tunica muscularis. The most striking finding on immunohistochemistry was the marked nuclear staining of cells with synaptophysin in all layers of the PUJ obstruction specimens that was totally absent in the normal PUJ specimens. In addition, significantly less intense staining for GDNF was found in the PUJ obstruction specimens compared with the normal PUJ specimens. The underexpression of GDNF in PUJ obstruction specimens was localized in the muscular layer especially. Immunohistochemical staining for S-100 and neurofilament showed no differences in the expression level of these neuronal markers in normal and PUJ obstruction specimens.

CONCLUSIONS

Because GDNF is a survival factor for central and peripheral neurons, defective expression of GDNF could play an important role in the defective neuronal innervation of PUJ obstruction. Intense nuclear expression of synaptophysin in all layers of obstructed PUJ specimens suggested that obstructed PUJs have a serious structural abnormality.

Structural changes of smooth muscle in congenital ureteropelvic junction obstruction

BACKGROUND/PURPOSE

Ureteropelvic junction (UPJ) obstruction is the most common cause of congenital hydronephrosis. Previous studies have reported that the excess amount of collagen restricting mobility and resiliency of the UPJ is the result of an impaired collagen production by anomalous smooth muscle cells (SMCs). Our purpose was to evaluate the role of SMC differentiation in the pathogenesis of UPJ obstruction.

METHODS

Surgical specimens of UPJ from 21 patients (8 girls/13 boys) who were subjected to dismembered pyeloplasty were examined immunohistochemically using monoclonal antibodies against smooth muscle (SM) myosin heavy chain isoforms including SM1, SM2, and SMemb. The age ranged from 1 month to 13 years. Ureteropelvic walls taken from 14 forensic autopsy cases, with no urological abnormalities, served as age-matched control group.

RESULTS

The immunohistochemical expression of SM1 and SM2 in UPJ obstruction was significantly increased when compared with controls (P < .05). In contrast, there was no statistical difference of expression of SMemb.

CONCLUSION

Our findings supported the hypothesis that the primary anomaly in UPJ obstruction may be attributed to a malfunction of SMCs in the ureter.

Interstitial cell of Cajal-like cells in the upper urinary tract

Autorhythmicity in the upper urinary tract (UUT) has long been considered to arise in specialized atypical smooth muscle cells (SMC) predominately situated in the most proximal regions of the pyeloureteric system. These atypical SMC pacemakers have been thought to trigger adjacent electrically-quiescent typical SMC to fire action potentials which allow an influx of Ca2+ and the generation of muscle contraction. More recently, the presence of cells with many of the morphological, electrical and immunohistochemical characteristics of interstitial cells of Cajal (ICC), the pacemaker cells of the gastrointestinal tract, have been located in many regions of both the upper and lower urinary tract. This article reviews the evidence from the literature and from our laboratory supporting a role of both atypical SMC and ICC-like cells in the initiation and propagation of pyeloureteric peristalsis in the UUT. We propose a new model in which there are 2 populations of pacemaker cells, high frequency atypical SMC and lower frequency ICC-like cells, both of which can drive electrically-quiescent typical SMC. The relative presence of these 2 populations of pacemaker cells and the relatively-long refractoriness of typical SMC determines the decreasing frequency of contraction with distance from the renal fornix. In the absence of the proximal pacemaker drive from atypical SMC after pyeloureteral/ureteral obstruction or surgery, ICC-like cell pacemaking provides a compensatory mechanism allowing the ureter to maintain rudimentary peristaltic waves and movement of urine from the pyelon towards the bladder.

ELASTIN CONTENT OF THE RENAL PELVIS AND URETER DETERMINES POST-PYELOPLASTY RECOVERY

PURPOSE

We evaluated the collagen-to-smooth muscle tissue matrix ratio and percentage of elastin in the renal pelvis, ureteropelvic junction (UPJ) and ureter, and compared these findings with the degree of obstruction, patient age and post-pyeloplasty renal recovery.

MATERIALS AND METHODS

We analyzed histological sections from 75 patients with UPJ obstruction. Nine patients were excluded owing to bilateral UPJ obstruction and an improper specimen. We divided the specimen obtained from pyeloplasty into 3 parts, namely the renal pelvis above the obstruction, the obstructed UPJ portion and the ureter below the obstruction. To examine the collagen and smooth muscle, sections were stained using Masson's trichrome, and elastic van Giesson stain was used for elastin, smooth muscle and collagen. Collagen, smooth muscle and elastin populations were identified, and the tissue matrix ratio and percentage of elastin were calculated by color image analysis.

RESULTS

In patients with lower ratios of collagen-to-smooth muscle in the UPJ proper hydronephrosis was more improved postoperatively (p = 0.049). In patients with a lower percentage of elastin in the renal pelvis, UPJ and ureter hydronephrosis was more improved postoperatively (p <0.0001).

CONCLUSIONS

Because the UPJ portion was resected during pyeloplasty, the renal pelvis and the ureter remaining after pyeloplasty are likely to be related to improved hydronephrosis. A higher percentage of elastin in the renal pelvis and ureter contributes to inelasticity and low compliance, and results in a slower recovery from hydronephrosis after pyeloplasty.

The expression of epidermal growth factor and transforming growth factor-beta1 in the stenotic tissue of congenital pelvi-ureteric junction obstruction in children

PURPOSE

The aim of this study was to test the hypothesis that expression of epidermal growth factor (EGF) and transforming growth factor-beta 1 (TGF-beta 1) may be altered in stenotic tissue of patients with congenital hydronephrosis caused by pelviureteric junction (PUJ) obstruction and to evaluate the role of these 2 growth factors.

METHODS

The expression of EGF and TGF-beta 1 was evaluated in tissue specimens in 25 children with PUJ obstruction and 15 controls with normal PUJs by immunohistochemistry, in situ hybridization, and reverse transcriptase polymerase chain reaction (RT-PCR) techniques. All the signals of mRNA products were normalized to the mRNA levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) a housekeeping gene, as a ratio.

RESULTS

On RT-PCR study, the amount of TGF-beta 1 mRNA in stenotic tissue was higher than in controls, in addition, EGF gene expression in the obstructed junction was significantly lower than in normal junctions. The TGF-beta 1 to GAPDH ratio was 0.57 +/- 0.26 and 0.36 +/- 0.19 in the stenotic tissue and the normal ureter, respectively (P =.012). The EGF to GAPDH ratio was 0.17 +/- 0.08 and 0.37 +/- 0.14 in the stenotic tissue and the normal ureter, respectively (P =.0001). Furthermore, the positive correlations were found between TGF-beta1 gene and protein expression (r = 0.601; P =.001), TGF-beta 1 gene and drainage clearance half-time (T1/2) (r = 0.474; P =.017), TGF-beta 1 protein expression, and T1/2 (r = 0.516; P =.008). A negative correlation was found between EGF gene and T1/2 (r = -0.448; P =.025). On immunolabeling and in situ hybridization labeling, the expression of TGF-beta 1 protein was strongly positive and confined to the muscle cells, spindle cells, and collagen fibers in the stenotic tissue; the expression of TGF-beta 1 mRNA was moderately positive and mainly distributed in the collagen of the stenotic segment, both the expression of EGF protein and mRNA were negative in the normal ureter.

CONCLUSIONS

There were increased TGF-beta 1 mRNA expression and decreased EGF mRNA expression in the stenotic tissue after clinical ureteropelvic junction obstruction. The alteration of EGF and TGF-beta 1 expression may be involved in the pathogenesis of congenital hydronephrosis.

Pelviureteric junction obstruction: how much is the extent of the upper ureter with defective innervation needing resection?

BACKGROUND/PURPOSE

It is well realized that Anderson-Hyne's pyeloplasty fails to improve the drainage pattern and renal functional parameters in a few cases of hydronephrosis because of pelviureteric junction (PUJ) obstruction. The purpose of this study is to delineate the lower extent of the abnormally innervated pelviureteric junction by S-100 immunohistochemistry, which requires surgical removal.

METHODS

Thirty pelviureteric junction (PUJ) specimens were analyzed by histology and by S-100 immunohistochemistry after serial sectioning of the resected ureter and compared with the variables age, calyceal separation, parenchymal thickness, differential renal function, glomerular filtration rate (GFR), and the measured constricted ureteral segment on gross examination.

RESULTS

No significant correlation was noted (P >.05) when the histology was analyzed to find any association with any of the variables studied. The length of the visible constricted segment ranged from 2 mm to 15 mm (mean, 5.37 mm). The abnormally innervated segment was much longer than the length of the visible constricted segment in 24 and of the same length in 5 specimens. However, in 1 case, the abnormal innervation segment was shorter than the macroscopic constriction by 3 mm. The maximum difference in length between the visible constriction and the lower limit of defective innervation was 8 mm.

CONCLUSIONS

The abnormally innervated ureteral segment below the PUJ in hydronephrosis is longer than the visible constricted segment at the time of surgery, and the ureter should be excised at least 8 mm or more beyond the visible lower limit of the constricted segment in cases of Anderson-Hyne's pyeloplasty.

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.

Ureteral ischemia model: an explanation of ureteral dysfunction after chronic obstruction

BACKGROUND AND PURPOSE

Many models of smooth muscle ischemia have been developed to explain organ insufficiency or failure. Ureteral decompensation may also be described in these terms. We anticipate that ureteral ischemia will result from overdistention brought about by obstruction. A preliminary model to create an ischemic ureter is described herein.

MATERIALS AND METHODS

Six white New Zealand female rabbits were used for this study. All had their left ureters surgically ligated at the level of the urinary bladder. The right ureters served as controls. In the acute-phase group, the ureters were all reexplored 2 weeks postobstruction. Exploration of the other rabbits was delayed for 3 more weeks. A laser Doppler needle (Transonics Inc.) was used to measure tissue perfusion in the rental artery, renal vein, renal parenchyma, renal pelvis, ureteropelvic junction, upper ureter, mid ureter, lower ureter, and lateral wall of the bladder. Baseline and postobstructive measurements of tissue perfusion were collected and compared.

RESULTS

In both the acute and the chronic obstruction groups, there was a demonstrable drop-off in perfusion of the ureteral sidewall. A more notable loss of perfusion was seen in the distal ureter.

CONCLUSION

The increased wall tension in the obstructed ureter results in a significant decrease in smooth muscle perfusion. This ischemia may result in the same functional and histologic changes that occur in other smooth muscle organs. Ultimately, the poor outcomes of some restorative/reconstructive procedures on the ureter may be explained in terms of smooth muscle ischemia.

Ureteropelvic junction obstruction in infants and children

An important question that needs to be answered in larger numbers of children is the potential recoverability of function in those followed up until function decreases. Most series involve small numbers. Some investigators claim that the function, once lost, does not return; others believe that early repair yields better improvement than does repair after 1 year. In the meantime, the authors continue to recommend a restrained interventional approach. The authors use surgical therapy early for infants with grade 3 or 4 dilatation and decreased function in the involved kidney or, overall, those with solitary kidneys or bilateral involvement. Those followed up undergo surgery if they show increased dilatation or loss of function, develop symptoms, or have dilatation that does not improve beyond the second year of life. The authors prefer to operate before there is loss of function, even at the risk of operating in a few infants that might have remained stable, because the long-term outcome of those who remain dilated is unknown and follow-up in some environments is not always reliable. Whether improved analysis of the excretory pattern on renography will prove to have prognostic value is unknown.

Ureteral ischemia model: an explanation of ureteral dysfunction after chronic obstruction

BACKGROUND AND PURPOSE

Many models of smooth muscle ischemia have been developed to explain organ insufficiency or failure. Ureteral decompensation may also be described in these terms. We anticipate that ureteral ischemia will result from overdistention brought about by obstruction. A preliminary model of an ischemic ureter is described herein.

MATERIALS AND METHODS

Six female New Zealand rabbits were used for this study. All had their left ureters surgically ligated at the level of the urinary bladder. The right ureters served as controls. In the acute-phase group, the ureters were reexplored 2 weeks after creation of obstruction. The other three rabbits were explored 3 weeks later. A laser Doppler needle was used to measure tissue perfusion with bilateral measurements of the renal artery and vein; renal parenchyma; renal pelvis; ureteropelvic junction; upper, mid, and lower ureter; and the lateral wall of the bladder. Baseline and postobstructive measurements of tissue perfusion were collected.

RESULTS

In both the acute and chronic obstruction groups, there was a demonstrable drop-off in perfusion of the ureteral wall.

CONCLUSION

The increased wall tension in the obstructed ureter results in a significant decrease in smooth muscle perfusion. This ischemia may result in the same functional and histologic changes that occur in other smooth muscle organs deprived of normal blood flow. Ultimately, poor outcomes of some restorative/reconstructive operations on the ureter may be explainable in terms of smooth muscle ischemia.

Elevated bladder urine concentration of transforming growth factor-beta1 correlates with upper urinary tract obstruction in children

PURPOSE

We evaluated urinary transforming growth factor-beta1 (TGF-beta1) concentration in children with upper urinary tract obstruction as a potential tool for supporting the diagnosis of clinically significant obstruction.

MATERIALS AND METHODS

Renal pelvic and bladder urine samples were obtained for analysis from 30 patients a median of 5 months old who underwent surgery for obstruction at the ureteropelvic (29) and ureterovesical (1)junctions. Urinary TGF-beta1 concentration was measured using a quantitative sandwich enzyme-linked immunoassay technique. Bladder urine TGF-beta1 in patients with obstruction was compared with that in controls. In addition, we compared renal pelvic and bladder urine TGF-beta1 in patients with obstruction.

RESULTS

Mean bladder urine TGF-beta1 plus or minus standard error of mean was 4-fold higher in patients with upper tract obstruction than in controls (195 +/- 29 versus 47 +/- 7 pg./mg. creatinine, p <0.001). In the obstructed group mean TGF-beta1 in the renal pelvic urine was 378 +/-86 pg./mg. creatinine, or twice that of the bladder urine (p = 0.02).

CONCLUSIONS

Bladder urine TGF-beta1 in patients with upper urinary tract obstruction is significantly elevated compared with that in controls. To our knowledge our study is the first to identify a bladder urinary marker that correlates with upper urinary tract obstruction with greater than 90% sensitivity. Measuring TGF-beta1 in a voided bladder urine sample may provide an objective and noninvasive test for assisting in the diagnosis of upper urinary tract obstruction.

Angiotensin induces the urinary peristaltic machinery during the perinatal period

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.

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.

Dynamic ultrasound for assessing obstructions in the upper urinary tracts: Usefulness and reliability

Renal ultrasound is not a functional type of examination, which means it cannot be used to determine the degree of obstruction of the upper urinary tract, for which more or less invasive exams such as Whitaker's test, renogram and/or urography must be perfomed. Dynamic ultrasound with furosemide test gives information on the morphology and also the degree of obstruction and is extremely useful in the pre and post-operative assessment of patients with upper urinary tract pathologies. A total of 72 renoureteral units in 39 patients were studied. Patients with a normal “dynamic” ultrasound picture were excluded, while the others were also studied with renogram and/or urography. Data analysis shows dynamics ultrasound reliability is on a par with that of the above-mentioned invasive methods (88–95%). Given the simplicity of use and its availability in all hospital structures, it is therefore considered that dynamic ultrasound should be used immediately in studying obstructions of the upper urinary tracts.

Urine levels of transforming growth factor-beta 1 in children with ureteropelvic junction obstruction

OBJECTIVES

To determine if there are measurable quantities of transforming growth factor-beta 1 (TGF-beta 1) in the urine of children with either normal or pathologic conditions of the urinary tract, specifically vesicoureteral reflux (VUR) and ureteropelvic junction obstruction (UPJO). We also sought to determine if the urine TGF-beta level could distinguish between renal obstruction and no obstruction.

METHODS

Preoperative bladder urine from consecutive patients undergoing pyeloplasty (UPJO group; n = 13), ureteral reimplantation (VUR group; n = 11), or circumcision/orchiopexy (control group; n = 19) as well as urine from the renal pelvis of the UPJO group was collected. The urine level of TGF-beta 1 was measured using a quantitative sandwich enzyme immunoassay technique.

RESULTS

Urine level of TGF-beta 1 was detected in each group: control (26.6 +/- 6.3 pg/mL), reflux (22.1 +/- 9.6), UPJO-pelvic urine (82.4 +/- 19.3), UPJO-bladder urine (31.2 +/- 8.2). The urine TGF-beta 1 concentration in pelvic urine in the UPJO group was significantly higher than that in bladder urine in children in the UPJO group (p = 0.03). TGF-beta 1 concentrations were similar from the bladder of children in all three study groups (p = NS).

CONCLUSIONS

Urine TGF-beta 1 is detectable in children with normal and pathologic urinary tracts. The level of this urine marker is elevated in the renal pelvis of children with UPJO compared to the level in the bladder of either obstructed or nonobstructed upper urinary tracts.

Urinary tract obstruction in children

PURPOSE

Perinatal identification of children with congenital urinary obstruction has challenged our understanding of the pathophysiology and clinical treatment of many children with hydronephrosis.

MATERIALS AND METHODS

A critical review of recent reports relating to congenital urinary obstruction in children was performed in an attempt to integrate clinical and experimental information.

RESULTS

Several themes emerged from the many reports relating to congenital urinary obstruction that have not been previously emphasized. Congenital obstruction begins and evolves in a developing fetal kidney, indicating the importance of the effect of obstruction on renal growth and development, which is distinct from the postnatal renal response to obstruction. Variation in the ability of the developing kidney to compensate for obstruction may be an important factor in explaining variability in clinical and experimental reports. Clinical data show an unpredictable outcome of congenital hydronephrosis. Nonoperative management of hydronephrosis is supported by empirical evidence yet raises many questions regarding the certainty of outcome and the risks involved. It imposes on the practitioner a significant clinical obligation. The ability to differentiate between clinically significant and insignificant obstruction is the current challenge to be fulfilled by integrated clinical and experimental investigation.

CONCLUSIONS

The unique features of congenital urinary obstruction separate it from better understood acquired postnatal obstruction. Understanding the effects of obstruction on the developing kidney prenatally and postnatally is critical. A definition is proposed for congenital urinary obstruction in children, that is a condition of impaired urinary drainage which, if uncorrected, will limit the ultimate functional potential of a developing kidney.

Urinary tract obstruction in children

PURPOSE

Perinatal identification of children with congenital urinary obstruction has challenged our understanding of the pathophysiology and clinical treatment of many children with hydronephrosis.

MATERIALS AND METHODS

A critical review of recent reports relating to congenital urinary obstruction in children was performed in an attempt to integrate clinical and experimental information.

RESULTS

Several themes emerged from the many reports relating to congenital urinary obstruction that have not been previously emphasized. Congenital obstruction begins and evolves in a developing fetal kidney, indicating the importance of the effect of obstruction on renal growth and development, which is distinct from the postnatal renal response to obstruction. Variation in the ability of the developing kidney to compensate for obstruction may be an important factor in explaining variability in clinical and experimental reports. Clinical data show an unpredictable outcome of congenital hydronephrosis. Nonoperative management of hydronephrosis is supported by empirical evidence yet raises many questions regarding the certainty of outcome and the risks involved. It imposes on the practitioner a significant clinical obligation. The ability to differentiate between clinically significant and insignificant obstruction is the current challenge to be fulfilled by integrated clinical and experimental investigation.

CONCLUSIONS

The unique features of congenital urinary obstruction separate it from better understood acquired postnatal obstruction. Understanding the effects of obstruction on the developing kidney prenatally and postnatally is critical. A definition is proposed for congenital urinary obstruction in children, that is a condition of impaired urinary drainage which, if uncorrected, will limit the ultimate functional potential of a developing kidney.

Correlation of renal biopsy and radionuclide renal scan differential function in patients with unilateral ureteropelvic junction obstruction

To understand better the relationship among radionuclide renal scan differential function, renal histology and the outcome of pyeloplasty we performed ipsilateral renal biopsies in a series of patients undergoing primary pyeloplasty. A total of 17 consecutive patients with unilateral ureteropelvic junction obstruction underwent renal biopsy at the time of pyeloplasty. Biopsies were examined systematically after sections were stained with hematoxylin and eosin, periodic acid, Schiff, Jones modified silver or Masson trichrome stains, and they were reviewed by 1 pathologist. Biopsy results were correlated with preoperative and postoperative radionuclide renal scan differential functions. Patient age ranged from 1 month to 7 years (mean 19.8 months). Renal biopsy was abnormal in 6 kidneys, of which 5 had a preoperative differential function of less than 33%. None of these kidneys had evidence of postoperative improvement in renal function on followup scans despite a technically successful result. All remaining 11 kidneys had normal biopsies and a preoperative differential function of greater than 44%. We conclude from these data that patients with ureteropelvic junction obstruction with a differential function of less than 35% have a high probability of significant histological changes on biopsy and a low probability of postoperative improvement in differential function.

Response of the newborn ureteropelvic junction complex to induced and later reversed partial ureteral obstruction in the rabbit model

The clinical controversy regarding the timing of surgery for asymptomatic newborns with obstructed hydronephrosis was addressed using a model of reversible partial ureteral obstruction in the newborn rabbit. The histomorphometric changes in the ureteropelvic junction complex (for example, pelvis, ureteropelvic junction and upper ureter) and kidney in 44 normal cases were determined and compared with the effects of 47 cases of ongoing partial obstruction and timed reversal of partial obstruction at 1 week in 9 cases, at 2 weeks in 10 or at 4 weeks in 10 (end of the study at age 8 weeks). After partial obstruction hydronephrosis appeared by 1 week postoperatively. There were progressive increases in the thickness of the lamina muscularis and mass index of smooth muscle and collagen (all p < 0.001). However, since the per cent surface area of smooth muscle did not change significantly in comparison to normal, there was disproportionately more collagen. For reversals at 1 week the muscle and collagen in the lamina muscularis were not significantly different from normal. For reversals at 2 weeks the mass index of collagen was greater than normal (p < 0.05) and reversal at 1 week (p < 0.05). For reversals at 4 weeks the lamina muscularis was thicker, and the mass index of collagen and muscle was greater than the earlier reversal groups and normal (all p < 0.05). In conclusion, partial ureteral obstruction causes progressive thickening of the lamina muscularis by collagen and muscle with a disproportionately greater increase in collagen than muscle. The earlier the obstruction can be reversed, the more normal is the ureteropelvic junction complex histology. The functional significance of these changes needs to be determined.

Bladder smooth muscle cells in culture: I. Identification and characterization

This report documents the growth and culture characteristics of human and fetal bovine bladder smooth muscle cells in vitro. Bladder smooth muscle cell strains have been identified by their spindle shaped morphology, noncontact inhibited growth characteristics and the expression of smooth muscle cell specific alpha-actin. Extracellular matrix protein biosynthesis by these cells in vitro has been characterized by metabolic labeling of proteins with [14C] radiolabeled proline and analysis by SDS gel electrophoresis. These studies demonstrate that bladder smooth muscle cells synthesize predominantly types I and III collagen, and fibronectin. In addition type III collagen exists in both a partially processed (pN alpha 1[III]) form and processed form. Complementary immunohistochemical studies show localization of type I, III, and IV collagens, and fibronectin to bladder smooth muscle cell extracellular matrix. We conclude that both fetal bovine and human smooth muscle bladder cells are capable of secreting the classic components of the surrounding connective tissue.