Extracellular matrix in fetal kidney after experimental obstruction.

PURPOSE: We studied the long-term effects of complete unilateral ureteral obstruction on the extracellular matrix composition of the fetal kidney interstitium in neonatal opossums. MATERIALS AND METHODS: We created complete left ureteral obstruction in 2-week-old opossum pups. Sham operated animals served as controls. A total of 12 animals were sacrificed 2, 3 and 5 weeks after obstruction, and the kidneys were harvested. Resultant tissue sections were prepared for light and electron microscopy, and immunohistochemical testing for alpha-smooth muscle action (SMA), fibronectin, laminin and type IV collagen. In situ hybridization was done to determine interstitial collagen type I. Western blot analysis was performed on single kidney protein extracts for alpha-SMA, fibronectin and laminin. RESULTS: Light microscopy revealed established interstitial fibrosis and tubular atrophy 2 weeks after obstruction which increased with the duration of obstruction. Electron microscopy showed an increased number of interstitial fibroblasts, increased extracellular lucent substance and thin collagen fibrils. The tubular basement membranes were irregular and thickened compared with the continuous and even contours in controls. The deposition of alpha-SMA, fibronectin, collagen types I and type IV were markedly increased in the interstitium compared with controls and were highest at 5 weeks. Type IV collagen was associated with aberrant peritubular capillaries within the scarred interstitium. There were no appreciable differences in laminin expression in obstructed and sham operated kidneys. CONCLUSIONS: Experimental obstruction in opossums alters the cell phenotype, extracellular matrix and microcapillary composition in the fetal kidney interstitium. Biosynthetic properties of the interstitial fibroblasts in obstructed kidneys appear similar to those of undifferentiated mesenchyma before the induction of nephrons. We propose that these aberrant extracellular matrices coincident with cytoarchitectural disturbance may form a faulty scaffold that hampers normal kidney development secondary to complete unilateral ureteral obstruction.

Cessation of prophylactic antibiotics for managing persistent vesicoureteral reflux.

PURPOSE: We reviewed our experience with patients with vesicoureteral reflux treated off prophylactic antibiotics. MATERIALS AND METHODS: We retrospectively reviewed the records of patients with vesicoureteral reflux treated off prophylactic antibiotics, noting the intervals on and off antibiotics, urinary tract infection, signs and symptoms associated with urinary tract infection, and renal ultrasound and dimercapto-succinic acid scan findings. RESULTS: We identified 196 patients with vesicoureteral reflux treated off prophylactic antibiotics, including 122 who were infection-free while on and 124 who had no urinary tract infection while off prophylactic antibiotics. The infection rate on and off prophylactics was 0.29 and 0.24 urinary tract infections per patient per year, respectively. New scars were identified in 5 patients while on prophylactics and in 7 after antibiotics were discontinued. Comparing different subgroups off prophylactic antibiotics showed that children who presented with scarring had statistically fewer new scars than those with normal initial dimercapto-succinic acid imaging (p <0.043). Girls had significantly more urinary tract infections than boys while off prophylactics (p <0.01) despite the older age at antibiotic cessation. However, after infection occurred while off prophylactic antibiotics, new renal scars developed at about the same rate in boys and girls. Because most patients did not have a urinary tract infection while off prophylactic antibiotics, new renal scars developed in only 2.2% of all boys and 4% of all girls. CONCLUSIONS: Our findings imply that discontinuing antibiotics is reasonable and safe in patients in whom vesicoureteral reflux fails to resolve.

Intravesical electrostimulation in pediatric patients with spinal cord defects.

PURPOSE: Creating a low pressure continent urinary storage mechanism for the pediatric patient with neurogenic bladder is difficult. Current therapy, which is enterocystoplasty with intermittent catheterization, is not an ideal solution. In an effort to optimize storage we used intravesical electrostimulation in patients with spinal cord defects. MATERIALS AND METHODS: A retrospective review of all pediatric patients undergoing bladder stimulation was performed. Parameters reviewed included indication, patient age, initial age adjusted pressure specific bladder volume (less than 30 cm. H2O), initial leak point pressure, number of treatments, number of sessions per treatment, posttreatment age adjusted pressure specific bladder volume, voiding and continence status. RESULTS: Records of all 44 patients treated were reviewed. Indications for treatment included decreasing bladder storage pressures in 24 cases, increased continence between catheterization in 13 and achieving volitional voiding in 7. Patients who became continent had similar age at initiation of treatment, number of treatments, number of sessions, initial leak point pressure and final age adjusted pressure specific bladder volume compared to nonresponders. Nonresponders required surgical intervention to achieve continence with safe storage pressures. Overall, 16% (7 of 44) of patients were continent with safe storage pressures at the completion of treatment and 9% (4 of 44) achieved pretreatment goals. CONCLUSIONS: While some high risk patients were spared surgery due to intravesical electrostimulation, most were not. Spontaneous voiding to completion at safe pressures was not achieved. We were unable to clarify before treatment which patients would benefit from intravesical electrostimulation.

Cell proliferation, apoptosis, Bcl-2 and Bax expression in obstructed opossum early metanephroi.

PURPOSE: Complete ureteral obstruction (CUTO) in the fetal kidney induces tubular and glomerular cysts, interstitial fibrosis, and halts renal development. Previous studies have shown that apoptosis is a predominant mechanism in the chronically injured kidney following obstruction, but the precise cellular and molecular mechanisms are poorly understood. MATERIALS AND METHODS: We have used CUTO in opossum pups with early metanephric kidneys, sacrificed at two weeks, to evaluate the role of cell proliferation, apoptosis and apoptosis regulating genes, Bcl-2 and Bax. RESULTS: Obstructed fetal kidneys demonstrate high apoptosis in the renal pelvis and tubulointerstitium, compared with sham operated animals. Apoptosis is accompanied by statistically significant increased cell proliferation in the interstitium but not in tubules. Apoptosis in the tubules is accompanied by increased Bax and decreased Bcl-2 staining. In the nephrogenic zone apoptosis is increased, even though it is not statistically significant. Bcl-2 and Bax in the nephrogenic zone are unchanged compared with sham, but cell proliferation is increased. CONCLUSIONS: We suggest that abnormal patterns of cell kinetics may contribute to disease pathogenesis in the obstructed fetal kidney.

Prostatorectal fistula associated with tubular colorectal duplication.

Tubular colonic duplications are exceedingly rare. The authors present an unusual case of a boy with a persistent prostatorectal fistula resulting from a tubular colorectal duplication. The current case is unique for 2 reasons: (1) the presence of a fistula without any concomitant genitourinary anomalies and (2) the existence of a prostatorectal fistula.

Multi-institutional study of testicular microlithiasis in childhood: a benign or premalignant condition?

PURPOSE: Testicular microlithiasis, a rare ultrasonographic diagnosis in children, has been shown to coexist in benign and malignant conditions. The natural history of incidentally discovered testicular microlithiasis has not been well defined in the pediatric population. The concern that testicular microlithiasis may be a premalignant condition has been raised. Reports indicate as much as a 45% association of germ cell tumors with testicular microlithiasis at the time of tumor diagnosis and there have been 4 cases of interval testicular tumor development associated with preexisting testicular microlithiasis. To address this issue we performed a multi-institutional study to evaluate children with incidentally diagnosed testicular microlithiasis. MATERIALS AND METHODS: Data on 26 patients with a mean age of 12.3 years at presentation with incidentally discovered testicular microlithiasis were collected from 7 institutions. Presenting scrotal conditions were reviewed. Two children with a previous testicular malignancy were excluded from study. RESULTS: Followup ranged from 1 month to 7 years (mean 27.6 months). Testicular biopsy and tumor marker (alpha-fetoprotein and beta-human chorionic gonadotropin) determinations were performed in 9 and 15 patients, respectively. To date no testicular tumor has developed during clinical followup. CONCLUSIONS: Our multi-institutional study has not yet shown a trend toward the malignant degeneration of incidentally diagnosed testicular microlithiasis in children. However, we still advocate close surveillance of patients with testicular microlithiasis, such as yearly testicular ultrasound, physical examination, and judicious tumor marker determinations. We propose that a registry be started to follow prospectively patients with testicular microlithiasis to define its significance better.

Relationship of renal size, body size, and blood pressure in children.

Somatometric parameters, renal size, and systolic blood pressure (SBP) were studied in 406 patients referred to pediatric nephrology and urology clinics. These patients included 269 females (66%), 67 African Americans (17%), and 87 patients with essential hypertension (21%). Z scores for the study population were comparable to published standards for height, kidney length, and SBP. Weight and body mass index scores were significantly greater than predicted from the standards, especially in the subset of patients with essential hypertension. Age, height, weight, body mass index, kidney length, and SBP all correlated with one another; however, on multiple regression analysis of SBP with the other five independent variables, only weight proved to have a significant correlation. Furthermore, the relationship of kidney length with SBP was positive and hypertensive patients had greater kidney size than published standards. These data do not support reduced kidney size in the population with essential hypertension, nor is there support for a convincing correlation between kidney length and SBP in the general pediatric population. Body weight correlates best with blood pressure. These findings warrant further study in a less-select population. Prevention and treatment of obesity may thus be of prime importance in addressing hypertension in children.

North American opossum Didelphis virginiana as a fetal nephrotoxicity model: histologic and ultrastructural assessment of uranyl nitrate (UN)-induced damage.

We have used our opossum model of fetal nephrotoxicity to investigate uranyl nitrate-induced morphologic changes in the developing kidney. The present study establishes a renal dose response curve for the uranyl nitrate (UN). We find that pups treated with nonlethal doses of UN do not demonstrate growth retardation compared to saline-treated controls. The kidneys of UN-treated pups are heavier than the control animals, an effect less apparent the longer the pups are followed. A low dose of 60 mg/kg of UN administered to small pups causes slight histologic derangement but nevertheless more change than the same dose administered to larger more mature pups. Using a dose of 100 mg/kg of UN that effectively causes nonfatal renal disruption, we examined the kidneys from 4 to 42 days following injection. We find that tubular dilation and epithelial necrosis starts soon after treatment (day 4) and reaches its maximum during the second and third week (11 and 22 days). Architectural restoration appears complete by the end of the third week. By electron microscopy, UN induces sequential structural damage with loss of proximal tubule brush border, epithelial necrosis with intact basement membranes and regeneration at 4, 11, and 22 days. Residual tubular mitochondrial damage is present at 42 days in spite of histologically normal tubules. No apparent lesions are seen in glomeruli. Fibroblastic interstitial proliferation in UN-treated kidneys at 11 days is not followed by appreciable fibrosis when assessed at 22 and 42 days. As the structural changes caused by 100 mg/ml UN administration in fetal opossum kidneys are reversible, this is a useful model to study the molecular mediators responsible for this form of renal damage and repair.

New renal scars in children with urinary tract infections, vesicoureteral reflux and voiding dysfunction: a prospective evaluation.

PURPOSE: Established renal scarring represents areas of the kidney that imaging reveals to be damaged at presentation for medical management of urinary tract infection. New renal scarring represents new renal damage in parts of the kidney that imaging reveals to be normal at presentation. We attempted to characterize patients in whom new renal scars developed while they were under our care. MATERIALS AND METHODS: In 1988 a data base was started to identify patients with new renal scarring. All patients presenting with urinary tract infections were enrolled. Our data base has 250 possible fields per event with multiple events per patient. More than 2,100 patients have been enrolled to date. All patients with pyelonephritis, defined as a febrile urinary tract infection with flank pain and tenderness, and all with reflux underwent dimercapto-succinic acid (DMSA) scan at least 4 months after presenting with infection to assess established renal scars. New renal scars were identified when new renal defects were demonstrated on a second DMSA scan. RESULTS: In our data base there are 1,426 patients with urinary tract infections, 685 (46%) with pyelonephritis and 1,062 (74.5%) with vesicoureteral reflux, including 558 found to have bilateral vesicoureteral reflux and 504 diagnosed with unilateral reflux. A history of daytime urinary incontinence was noted in 538 patients (37.7%), 192 (13.5%) had established scars at initial presentation and in 31 (2.1%) new renal scars developed while they were under our care, including 30 with established scars as well. Of the 25 patients in whom new renal scars developed while on medical therapy 11 underwent surgery. In 6 patients with dysfunctional voiding who were receiving medical treatment renal scars developed postoperatively. Surgery was performed in 17 of the 31 patients and 24 (77%) with new renal scars had a history of dysfunctional voiding. CONCLUSIONS: Previous characterizations of patients with new renal scars have relied on excretory urography for assessing renal architecture and ignored voiding patterns of the children affected. Using the DMSA scan we identified 31 children with reflux, urinary tract infection and dysfunctional voiding in whom new renal scars developed while they were under our care.

Increased expression of platelet-derived growth factor A and collagenous matrix proteins in congenital multicystic renal dysplasia.

The expression of platelet-derived growth factor A (PDGF-A), and its spatial and temporal relationship to interstitial collagens in kidneys with congenital multicystic dysplasia using in situ hybridization, have been examined. Seventeen dysplastic kidneys (16 weeks to 7 months) and 20 normal age-matched controls were used in the study. Increased PDGF-A mRNA was detected in dysplastic compared to normal kidneys in all age groups including extensively fibrotic postnatal kidneys. An abundant PDGF-A mRNA signal was seen within the epithelial cells of cystically dilated or dysplastic tubules and within interstitial fibroblasts and disorganized primitive mesenchyme. A comparable amount of PDGF-A protein was detected by Western blotting. Procollagen I and III mRNA were increased in fibroblasts surrounding cystic and dysplastic tubules. We conclude that tubular epithelial production of PDGF-A may induce collagenous matrix production by adjacent fibroblasts, while marked up-regulation of PDGF-A by interstitial cells may be responsible for sustainable fibrogenic effects in the fetal kidney contributing to renal maldevelopment.

Quantitative technetium-99M dimercaptosuccinic acid renal scanning in children.

OBJECTIVES: To develop a method for assessing absolute renal function (as well as morphology) in children, using gamma camera imaging of intravenously injected technetium-99m (99mTc) dimercaptosuccinic acid (DMSA). METHODS: Forty-five children (ages 1 week to 10 years; mean, 2.0 years) were imaged using a planar technique in which not only the appearance but the absolute amount of intravenously administered 99mTc DMSA taken up by the kidneys was calculated for each child and compared with contemporaneous determinations of creatinine clearance. RESULTS: There was a close correlation between the absolute DMSA uptake and creatinine clearance (r = 0.752). CONCLUSIONS: Renal function in children, expressed as creatinine clearance, can be accurately estimated by measuring absolute DMSA uptake with planar gamma camera imaging using 99mTc DMSA.

Insulin-like growth factor improves renal architecture of fetal kidneys with complete ureteral obstruction.

Others have previously demonstrated that the administration of insulin-like growth factor-I accelerates recovery from ischemic acute tubular necrosis in the rat kidney. We investigated the effect of insulin-like growth factor-I on the histology of unilaterally obstructed kidneys in the pouch young of the North American opossum, Didelphis virginiana. In this model complete unilateral ureteral obstruction reliably induces statistically significant degrees of caliceal dilatation, tubular cystic change, and cortical and medullary fibrosis in kidneys examined 1 week after the creation of complete obstruction. Cortical and medullary inflammation is also increased after 1 week of obstruction in this model but not to a degree that is statistically different than control (sham operated) animals. We administered insulin-like growth factor-I to opossum pups with complete unilateral obstruction created at a length of 5 cm. (age 25 days, human equivalent 18 to 20 weeks). Insulin-like growth factor-I (400 mcg/kg.) was injected subcutaneously on the day of operation and again on days 2 and 4 postoperatively. The animals were sacrificed 1 week after obstruction and the formalin fixed, paraffin embedded kidneys were assessed histologically. In the obstructed kidney insulin-like growth factor-I ameliorated the development of fibrosis (cortical and medullary) and caliceal dilatation such that these characteristics did not differ significantly from those of sham operated animals. Tubular cystic change in the obstructed kidneys was also decreased by insulin-like growth factor-I administration but not to significant levels. Insulin-like growth factor-I treatment in obstructed animals resulted in significantly more inflammation (cortical and medullary) than in the sham operated animals. We also administered insulin-like growth factor-I to normal pups with no other intervention. These insulin-like growth factor-I treated pups did not differ from sham pups for any characteristic studied. Our study suggests that there is protective effect of insulin-like growth factor-I on renal architecture when administered in the setting of experimental fetal ureteral obstruction.

Experimental ureteral obstruction in the fetal opossum: histologic assessment.

In the North American opossum, Didelphis virginiana unilateral complete ureteral obstruction (ECO) and partial unilateral (EPO) ureteral obstruction were created during the early metanephric stage of kidney development in pups attached to the teat (approximately 4.5 cm. long, 20 days old). At 70 days of pouch life (full-term equivalent in the human) some completely obstructed ureters were unobstructed with reanastomosis in the bladder (RECO). Other pups underwent unilateral complete ureteral ligation at this full-term equivalent (70 days of pouch life) and constituted the late obstruction (LCO) group. Unoperated animals constituted the control (C) group. All animals were harvested when full grown (.7 to 2.2 kg.), and paraffin sections of the kidneys were stained with hematoxylin and eosin and Masson's Trichrome. In each a semiquantitative assessment of 24 histologic features was made and a digital score assigned. All experimental groups except EPO demonstrated significant epithelial and mesenchymal alterations. The changes can be broadly categorized as those secondary to obstruction of urine flow (dilation and cystic changes), those affecting epithelial differentiation in both cortex and medulla and those affecting mesenchymal differentiation. The EPO group demonstrated significantly fewer glomerular generations than did control kidneys. For all other characteristics studied, the EPO group did not differ from control. The ECO group demonstrated significant changes when compared with control for most parameters studied. Medullary dysplasia was more prominent in kidneys obstructed early. Reanastomosis (RECO) at a full-term equivalent did ameliorate the changes of medullary dysplasia and cortical atrophy. More collecting duct hyperplasia, cortical and medullary aplasia were present in the LCO group compared with the ECO. The LCO group also had less primitive duct formation and less medullary dysplasia than the ECO group. Renal blastema, previously unreported in experimental obstruction, was present in 41% of experimental kidneys.

Acute urinary retention in children.

Acute urinary retention (AUR) is an uncommon diagnosis in childhood, associated with a variety of causes. The emergency physician is often the first to be called upon to evaluate and treat these children. To assist in making the diagnosis, we present our five-year experience with AUR presenting to the pediatric urology service, often through the pediatric emergency department. We present and discuss examples of not only the common reasons for AUR but also uncommon diagnoses and, in two cases, etiologies for retention we believe have not been previously described in the pediatric literature.

Testicular torsion: pitfalls of color Doppler sonography.

Only 25% of boys with acute scrotal swelling have testicular torsion. A noninvasive test that reliably distinguishes torsed testes from all other acute scrotal conditions would benefit patients presenting with pain and swelling of the scrotum. Recent reports suggest that color Doppler ultrasound may be the long-awaited test that clearly differentiates testes with compromised blood flow from all other conditions. However, we report on 2 patients with positive blood flow on color Doppler ultrasonography who subsequently were found at surgery to have testicular torsion. Inability to distinguish normal testes and normal epididymis on physical examination is still the best indicator to proceed with surgical exploration in pediatric patients with acute scrotal swelling.

Urinary PGE2 in rats with chronic partial unilateral ureteral obstruction.

Urinary prostaglandin E2 (PGE2) was measured in Munich-Wistar rats with surgically created chronic partial unilateral ureteral obstruction (UUO). Mean values of bladder urine PGE2 were higher in sham than in UUO (24.5 +/- 14.4 vs 12.9 +/- 8.2 ng/mg creatinine, respectively, P less than 0.05). Following diuresis, both ureters were cannulated and urine was collected. PGE2 excretion was increased in sham (66.5 +/- 34.4 and 70.1 +/- 44.5 ng/mg creatinine, left and right, respectively). But in UUO, the obstructed kidney excreted less PGE2 than the contralateral kidney (32.1 +/- 6.0 vs 62.3 +/- 40.4 ng/mg creatinine, obstructed vs contralateral, respectively, P = 0.08). PGE2 synthesis was then determined in separated renal medullary and cortical slices. Renal medullary slices from kidneys with severe obstruction synthesized less PGE2 than the contralateral unobstructed side (3.30 +/- 1.22 vs 10.52 +/- 3.23 ng/mg wet wt-30 min, respectively, P less than 0.05) and failed to respond to arachidonic acid stimulation with any significant increase in PGE2 synthesis (3.30 +/- 1.22 vs 4.47 +/- 1.04 ng/mg wet wt-30 min, baseline vs stimulated). In contrast, contralateral unobstructed kidney slices responded with a significant increase in PGE2 synthesis (10.52 +/- 3.23 vs 21.10 +/- 2.50 ng/mg wet wt-30 min, baseline vs stimulated, P less than 0.05). We conclude that chronic partial UUO in the Munich-Wistar rats resulted in significantly less PGE2 elaboration.