Myocyte Apoptosis in Primary Obstructive Megaureters: The Role of Decreased Vascular and Neural Supply

Evaluation of PGP 9.5, NGFR, TGFβ1, FGFR1, MMP-2, AT2R2, SHH, and TUNEL in Primary Obstructive Megaureter Tissue

Primary obstructive megaureter (POM) morphogenesis is not fully known. The aim of the study was to evaluate the appearance of different factors that might take part in the pathogenesis of POM. Megaureter tissues of 14 children were stained with hematoxylin and eosin as well as with immunohistochemistry for protein gene product 9.5, nerve growth factor receptor, transforming growth factor beta 1 (TGFβ1), fibroblast growth factor receptor 1 (FGFR1), matrix metalloproteinase 2 (MMP-2), angiotensin 2 receptor type 2, and sonic hedgehog (SHH) protein. Apoptosis was detected by terminal dUTP nick-end labeling reaction. POM tissues revealed transitional epithelium with scattered vacuolization, submucosa with inflammatory cells, and focally vacuolized and chaotically organized muscle layers. Apoptosis, appearance of MMP-2, FGFR1, and SHH prevailed, but TGFβ1 positive cell number was lower in patients. Correlation between MMP-2 in epithelium and endothelium, FGFR1 and MMP-2 in epithelium, and TGFβ1 in epithelium and connective tissue in patients was detected. POM morphopathogenesis involves an apoptotic cell death of epithelium and smooth muscle as well as tissue degradation in epithelium and connective tissue of the ureter wall. The decrease of tissue growth through diminished TGFβ1 expression and stimulation of FGFR1 and MMP-2 suggests a disbalance of tissue remodelation in the megaureter wall.

Pathological changes in ureterovesical and ureteropelvic junction obstruction explained by fetal ureter histology

The etiology of ureterovesical junction obstruction (UVJO) and ureteropelvic junction obstruction (UPJO) is obscure with an adynamic narrow segment causing the obstruction. In this study, the authors compared interstitial cells of Cajal (ICC) and collagen-to-muscle ratio (CM ratio) between UVJO, UPJO, and fetal ureters to investigate whether a maturational arrest of the fetal ureter could explain both clinical pathologies.

METHODS

Group 1 (control) involved specimens of the normal ureter (nephrectomy for trauma/tumor; n = 20), while group 2, specimens of UVJO (n = 14); group 2 was further divided into group 2a, the dilated megaureter above UVJO, and group 2b, UVJO narrow segment; group 3, UPJO narrow segment excised during pyeloplasty (n = 31); and group 4, normal fetal ureters (n = 12). The specimens were analyzed for ICC using immunohistochemistry and CM ratio on Masson's trichrome (stains collagen in blue and muscle in red).

RESULTS

The median ICC/10 high-power field was 16.1 (8.3) in the normal and 17.3 (7.9) in the dilated segment of the megaureter, with no significant difference, but was significantly less in the narrow segment of UVJO at 4.5 (2.0), narrow segment of UPJO at 5.1 (2.3), and fetal ureter at 5.0 (2.3). The median CM ratio was 0.75 (0.29) in the normal and 0.65 (0.2) in the dilated segment of the megaureter, with no significant difference between them (figure), but was significantly higher in the narrow segment of UVJO at 3.0 (0.8), narrow segment of UPJO at 2.5 (0.71), and fetal ureter at 3.1 (0.61). Overall UVJO, UPJO, and fetal ureter segment had significantly less ICC density and more collagen compared with the normal ureter (P < 0.001 by Mann-Whitney U test).

DISCUSSION

There are conflicting reports on the etiopathogenesis of UVJO and UPJO, with several authors showing decreased ICC and increased collagen in the narrow segment. In this study, the authors found that the pathological changes at UVJ and UPJ segments resemble fetal ureter morphology. We also found that in fetal ureters, as the gestation progressed, there was an increase in the ICC density/smooth muscle, whereas the collagen content decreased. While the entire ureter has uniform embryological origin, it essentially remains an epithelial tube until the late gestation. The maturational process involves differentiation of smooth muscles cells/ICC to establish the peristaltic machinery required to functionally connect the ureter at both ends. This process, probably, starts at the mid ureter during fetal life and extends toward the UPJ and UVJ, and its failure, probably, results in UPJO or UVJO. The study's limitations are small numbers, and further larger studies are required to validate this hypothesis.

Resolution of primary non-refluxing megaureter: an observational study

AIM

A prospective review of conservative management of primary non-refluxing megaureters (PM) was performed to determine the time taken for resolution (TTR) and complications.

MATERIAL AND METHODS

Patient details were obtained from a prospectively maintained database from January 1, 2003, to December 31, 2011. The clinical features of USS and MAG3 findings were analyzed. All had annual USS and MAG 3 scans two yearly (and whenever necessary).

RESULTS

Fifty ureteric units (UU) in forty-four patients (six bilateral) were studied. There were thirty-three (75%) males. In the unilateral PM, 22/38 were left-sided. Children were classified according to the lower ureteric diameter (UD) into two groups: Group A (Gp A) UD < 10 mm (n=25, 26 UU), and Group B (Gp B) UD ≥ 10 mm (n=19, 24 UU). Antenatal diagnosis was achieved in 21 (84%) UU in Gp A and 11 UU (58%) in Gp B. In Grp A, the median presenting UD was 6 (range 4-9) mm, and 76% resolved completely over a median duration of 60 (18-204)months. In Grp B, the median UD was 15 (10-27)mm, and 17% resolved completely over a median duration of 102 (42-210) months. Two developed ureteric calculi (removed ureteroscopically). Three with complications (obstructive drainage pattern in MAG 3 with decreasing function and debilitating infections) underwent ureteric tapering and reimplantation. An obstructed megaureter resolved after endoscopic dilatation. Another underwent temporary ureterostomy on developing hypertension.

CONCLUSION

The exclusively conservative management of PM seems highly successful within Group A (i.e. UD <10 mm). Complications (stones, decreasing renal function) were more common with higher UD. TTR seems to take over five years in both groups.

[Primary megaureter]

A primary megaureter is an anomaly with a prevesical or overall dilated ureter of more than 6 mm in diameter. It is important to distinguish between cases of primary non-refluxing and primary obstructive-refluxing megaureters, as the treatment of both is completely different. The basic diagnostic work-up includes ultrasonography and voiding cystourethrography. Diuretic renography is used to detect split renal function and the degree of upper urinary tract obstruction. In most cases of primary non-refluxing megaureter surgical treatment is unnecessary due to the high remission rate, whereas obstructive refluxing megaureters commonly only need to be corrected. Antibiotic prophylaxis may be indicated in infants with a primary obstructive megaureter during the first 6 months of life due to a higher risk of complications due to pyelonephritis especially in this age group.

Current perspectives on congenital obstructive nephropathy

Congenital obstructive nephropathy is the leading cause of chronic renal disease in children. As a result, it represents a tremendous societal burden in terms of morbidity and mortality, as well as in health care expenses of caring for children with chronic kidney disease and end-stage renal disease. The various diagnostic, prognostic, and therapeutic challenges associated with congenital obstructive nephropathy highlight the importance of developing effective experimental models for studying this disease process. In this review, we define the clinical entity that is congenital obstructive nephropathy, outline the current standards of diagnosis and care, and discuss the utilization of current experimental models designed to help clarify some of the clinical conundrums associated with this important disease.

The utilization of stents in the management of primary obstructive megaureters requiring intervention before 1 year of age

OBJECTIVE

To analyse the long-term outcome of 16 infants with primary obstructive megaureter managed by (endoscopic or open) stenting over a 10-year period.

METHODS

A retrospective case-note and imaging review was performed between 1997 and 2007. Data are presented as medians (range) and were compared using the Mann-Whitney test.

RESULTS

Sixteen infants with 19 obstructed megaureters were stented at a median age of 24 weeks, for a median of 6 months. One-third of stents were inserted endoscopically. Complications (stent migration, stone formation or infection) occurred in 31.6%. One infant was excluded due to a co-existent pelviureteric junction obstruction. Drainage improved in 10 ureters (56%) following stent removal. Of the remaining renal units, 6 were reimplanted, and 2 underwent a nephrectomy due to deterioration in renal function following stent removal. Resolution of the vesicoureteric junction obstruction occurred in 4 of 6 infants following endoscopic stent insertion, and in 6 of 12 infants following open stent insertion (P=0.60). There was no difference in the length of time that ureters were stented in the resolved (7.5 (6-15) months) versus the reimplanted (6.0 (1-18) months) group (P=0.13).

CONCLUSIONS

Of obstructive megaureters managed by stenting for a median of 6 months, 56% did not require further surgery. However, morbidity occurred in one third of patients, and function deteriorated after removal of stent in two patients who later required a nephrectomy.

Vitamin E administration at the onset of fever prevents renal scarring in acute pyelonephritis

We evaluated the protective effects of antioxidant at the onset of fever on renal damage in a rat model of acute pyelonephritis. Twenty rats were allocated to four groups. In groups 1 to 3, the animals were given direct inoculation of Escherichia coli into the right kidney, and group four served as control. All rats in groups 1 to 3 were given once-daily intraperitoneal injections of ceftriaxon for five consecutive days, beginning on the third day after inoculation. The animals' body temperatures were monitored; as soon as body temperature reaches 38 degrees C, the rats in group 2 were given allopurinol co-treatment, whereas, in group 3, vitamin E co-treatment was started at fever onset. Both kidneys were excised 6 weeks later, for the evaluation of histopathologic changes, apoptotic damage, and concentrations of transforming growth factor-beta (TGF-beta). Only minimal changes were found in control samples. Pathologic scores of inflammation and fibrosis in group 1 were higher than in the vitamin E and allopurinol groups (P < 0.05). Apoptosis index was also decreased in groups 2 and 3, compared to group 1 (P < 0.05). There was no significant difference in average TGF-beta levels between study groups. These findings suggest that administration of vitamin E or allopurinol following the onset of fever can reduce renal damage in pyelonephritis.