A quantitative histological evaluation of the dilated ureter of childhood. II: Ectopia, posterior urethral valves and the prune belly syndrome

Physiopathology of vesico-ureteral reflux

Vescico-Ureteral Reflux (VUR) is a common condition in childhood, caused by a congenital anomaly at the Vescico-Ureteral Junction (VUJ) level. It seems that the main cause could be an abnormal embryological development occurred during the early stage of fetal life.

Refluxing ureteral endings show structural and functional anomalies: previous studies have shown a significant decrease in alfa actin, miosin and desmin contents as well as an high rate of atrophy and muscular degeneration with disorganized muscular fibres. The roles played by Cajal cells and Connexin 43 in generating peristaltic waves appears to be fundamental for the physiological VUJ function and activity. Attention was focused also on the congenital muscular deficiency of the RUs, on regard to general morphology, smooth muscle cells architecture, inflammatory markers and the distribution of collagen composition.

This review will discuss and investigate the importance of the modified configuration of Sarcoglycan (SG) sub complex (particularly the deficiency of the ε-SG and the increased expression of the α-SG), the role played by Cajal Cells, the intravescical tunnel length to ureteral diameter ratio as possible causes of the functional alterations in the refluxing ureteral ends leading towards the VUJ incompetence.

New congenital anomalies of the kidney and urinary tract and outcomes in Robo2 mutant mice with the inserted piggyBac transposon

BACKGROUND

Disruption of ROBO2 in humans causes vesicoureteral reflux (VUR)/congenital anomalies of the kidney and urinary tract (CAKUT). PiggyBac (PB) is a DNA transposon, and its insertion often reduces-but does not eliminate-gene expression. The Robo2 insertion mutant exhibited non-dilating VUR, ureteropelvic junction obstruction (UPJO) not found in reported models. We studied the incidence and outcomes of VUR/CAKUT in this mutant and explored the relationship between Robo2 gene expression and the occurrence and severity of VUR/CAKUT.

METHODS

The urinary systems of newborn mutants were evaluated via Vevo 770 micro-ultrasound. Some of the normal animals-and all of the abnormal animals-were followed to adulthood and tested for VUR. Urinary obstruction experiments were performed on mice with hydronephrosis. The histology of the kidney and ureter was examined by light microscopy and transmission electron microscopy. Robo2 (PB/PB) mice were crossed with Hoxb7/myr-Venus mice to visualize the location of the ureters relative to the bladder.

RESULTS

In Robo2 (PB/PB) mice, PB insertion led to an approximately 50 % decrease in Robo2 gene expression. The most common (27.07 %, 62/229) abnormality was non-dilating VUR, and no statistically significant differences were found between age groups. Approximately 6.97 % displayed ultrasound-detectable CAKUT, and these mice survived to adulthood without improvement. No severe CAKUT were found in Robo2 (PB/+) mice. The refluxing ureters showed disorganized smooth muscle fibers, reduced muscle cell populations, intercellular edema and intracytoplasmic vacuoles in smooth muscle cells. Both UPJ and UVJ muscle defects were noted in Robo2 (PB/PB) mice.

CONCLUSIONS

Robo2 (PB/PB) mice is the first Robo2-deficient mouse model to survive to adulthood while displaying non-dilating VUR, UPJO, and multiple ureters with blind endings. The genetic background of these mutants may influence the penetrance and severity of the CAKUT phenotypes. VUR and other CAKUT found in this mutant had little chance of spontaneous resolution, and this requires careful follow-up. We reported for the first time that the non-dilated refluxing ureters showed disorganized smooth muscle fibers and altered smooth muscle cell structure, more accurately mimicking the characteristics of human cases. Future studies are required to test the role of Robo2 in the ureteric smooth muscle.

Detailed evaluation of the upper urinary tract in patients with prune belly syndrome using magnetic resonance urography

INTRODUCTION

Magnetic resonance urography (MRU) has proven to be useful in the setting of complex urologic anatomy. Prune belly syndrome (PBS) patients are known to have malformed and highly variable urinary tract anatomy due to significant dilation and renal dysplasia.

OBJECTIVE

To further characterize the renal and ureteral anatomy and renal function in patients with PBS via MRU.

STUDY DESIGN

Children with PBS undergoing MRU (2006-2011) were identified. Studies were performed to evaluate severe hydronephrosis in all patients. Demographics, previous imaging, and MRU findings were collected. A single radiologist reviewed all studies.

RESULTS

MRU was performed on 13 boys, with a median age of 29.3 months (IQR 6-97). Two patients underwent >1 study for ureteropelvic junction obstruction (UPJ obstruction) and calyceal diverticulum with a solitary kidney, respectively. Hydroureteronephrosis (HUN) was identified in 12 boys (92%), while one (8%) did not have ureteral dilation. All patients demonstrated morphologic abnormalities beyond HUN as follows: five (38%) renal dysplasia; five (38%) scarring; four (31%) calyceal diverticula; and three (23%) thickened bladder. The median renal transit time (RTT) was 6 min (IQR 3.5-10.5), and >8 min (range 8.5-35) in six patients; one patient was ultimately diagnosed with obstruction. The mean serum creatinine was 0.5 ± 0.3 mg/dl. This summary figure is a coronal excretory phase T1 MRU image demonstrating absence of well-defined calyces and a 5-cm calyceal diverticulum (white arrow).

DISCUSSION

This study reports significant anatomic and functional findings on MRU that were not readily apparent when using standard imaging for children with PBS. The high-resolution images and functional data obtained with MRU allowed for visualization of calyceal diverticula and abnormal renal pelvic anatomy not previously described in PBS. In addition, renal dysplasia could be identified with MRU, which is badly characterized in the PBS population outside of renal biopsy studies. Potential limitations of the study included its nature as a small retrospective case series, which limited the ability to compare imaging modalities. Imaging modalities were based on individual clinical needs; therefore, comparison with diuretic renal scintigraphy was limited.

CONCLUSION

MRU provided anatomic and functional details of the urinary tract in children with PBS that allowed for characterization of new renal anatomic abnormalities, including the incidence of calyceal diverticula and renal dysplasia, which have not been previously described. While renal scarring, dysplasia and calyceal diverticula were easily discerned on MRU in ten patients, their clinical significance requires longer follow-up in a larger patient population.

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.

Altered 'active' antireflux mechanism in primary vesico-ureteric reflux: a morphological and manometric study

OBJECTIVE

To immunolocate c-kit-positive interstitial cells of Cajal (ICCs, known to be responsible for pacemaker activity in human ureters, coordinating ureteric motility) in the intramural ureter of patients with different grades of vesico-ureteric reflux (VUR), to assess the ureteric histology and correlate these findings with manometric patterns.

PATIENTS AND METHODS

The VU junction (VUJ) represents the boundary between the low-pressure of the upper and high pressure of the lower urinary tract, protecting the upper tract from VUR using active and passive antireflux mechanisms. The contraction of the longitudinal muscle coat of the VUJ possibly functions as an 'active' antireflux system, but previous manometric findings on refluxing ureteric units (RUs) have shown altered patterns. In all, 32 RU ends were stained using both picro-Mallory and Sirius Red techniques; in a parallel immunohistochemical procedure, using mast cell tryptase and CD117 antibodies (to identify ICCs), they were compared with eight control ureteric ends. Ureteric manometry of the VUJ was also done during ureteric reimplantation.

RESULTS

The histochemical and immunohistochemical results in the RUs showed a replacement of the altered smooth muscle fascicles by collagenous stroma and significant loss of ICCs in RU ends, both correlated with the grade of VUR. Ureteric manometry showed significant impairment of basal and maximum pressure in RUs, correlated, respectively, with histological lesions and loss of ICCs.

CONCLUSION

Deficiency of the longitudinal muscle coat probably leads to dysfunction and insufficiency of the ostial valve mechanism, with subsequent impairment of the active valve mechanism. Histological, histochemical and immunohistochemical changes support the alterations of ureteric peristalsis in RUs.

The Intravesical Ureter in Children With Vesicoureteral Reflux: A Morphological and Immunohistochemical Characterization

PURPOSE

We investigated intravesical ureteral endings using immunohistochemical methods to study general morphology, smooth muscle architecture and collagen composition in children with vesicoureteral reflux.

MATERIALS AND METHODS

Samples were obtained from 29 ureterorenal units in children with a mean age of 52.3 months undergoing reflux surgery. Routine histological paraffin embedded sections were stained with hematoxylin and eosin, and Masson trichrome to assess general morphology. Staining for actin, myosin and desmin was performed to evaluate the presence, allocation and architecture of the ureteral smooth muscle wrap. In addition, indirect immunohistochemical methods were used to study the collagen composition of the ureteral wall and CD68 was used for macrophage labeling as a marker of tissue remnant scavenging. All investigations were done using high power field magnification for quantification. In addition, age matched, nonrefluxing ureteral specimens served as controls.

RESULTS

Smooth muscle alpha-actin, myosin and desmin expression were extensively decreased in all specimens pertaining to the ureteral ending. This distal part showed a high degree of muscle atrophy and degeneration as well as a disordered fiber arrangement associated with increased extracellular matrix collagen accumulation. In addition, CD68 positive macrophages were significantly increased. In contrast to these observations, the proximal intravesical portion of the ureter showed intact morphology and arrangement of the muscular coat.

CONCLUSIONS

Refluxing intravesical ureteral endings showed dysplasia, atrophy and architectural derangement of smooth muscle fibers. Consequently symmetrical contraction of the distal ureteral smooth muscle coat creating the active valve mechanism to protect reflux is not achievable.

Prune belly syndrome

Prune belly is a lax, wrinkled abdominal wall and frequently is associated with other anomalies. The prune belly syndrome is a specific constellation of anomalies consisting of an abdominal wall deficient in muscular tissue, dilated urinary tract, and bilateral cryptorchidism. This group of anomalies is also called the Eagle-Barrett syndrome and the triad syndrome. In about 3 of 4 patients with the prune belly syndrome, there are associated malformations of the cardiopulmonary, gastrointestinal, and orthopedic systems.

Histologic evaluation of spermatic veins in patients with varicocele

BACKGROUND

Information concerning varicocele is limited in spite of its clinical importance. This study intends to clarify anatomical features of varicocele.

METHODS

Spermatic veins were obtained from varicocele patients at surgery. Areas of two distinct portions (extracellular matrix and smooth muscle) were measured by a micro computer imaging device image analysis system on histologic slides with Masson trichrome stain. In addition, we evaluated the shape and arrangement of the smooth muscle fibers by a scanning electron microscope (SEM).

RESULTS

Masson trichrome stain revealed that grade of varicocele partly correlated with thickness of the wall and with amount of the smooth muscle fibers. In the patients with grade 3 varicocele, SEM examination showed marked hypertrophy of longitudinal smooth muscle fibers, which were discriminated clearly from the inner circular fibers.

CONCLUSIONS

This study indicated that morphological changes occurred in the muscle layers of varicoceles in the worst grade of varicocele. These structural changes which result from abnormal venous blood circulation may cause development of varicocele, resulting in male infertility.

Smooth muscle development in the obstructed fetal bladder

OBJECTIVES

To evaluate changes in the smooth muscle and connective tissue development in the obstructed and normal fetal bladder.

METHODS

The smooth muscle and connective tissue composition of 19 fetal urinary bladders, including those of 9 fetuses with anatomic obstruction and 10 controls free of urologic disease, were analyzed by light microscopy and computer-assisted color image analysis.

RESULTS

The bladder wall thickness was markedly increased in obstructed fetuses throughout gestation as compared with that in controls. The disparity in bladder wall thickness increased rapidly during gestation. The percent area density of smooth muscle and connective tissue as well as the ratio of smooth muscle to connective tissue remained the same in the obstructed and normal control fetal bladders.

CONCLUSIONS

Although bladder outlet obstruction is associated with a marked increase in bladder wall thickness, the percent of smooth muscle and connective tissue comprising the mural histology remains relatively constant as compared with that of normal fetal controls. This study suggests that bladder outlet obstruction in the fetus is not associated with excess collagen deposition but rather with an increased amount of bladder with normal cellular content and a concomitant increase in smooth muscle development.

Long-term results after megaureter folding in children

In 56 megaureters treated by the folding technique, good results were obtained in 52 (93%). Complications in four ureters included stenosis (2) and vesico-ureteral reflux (2). The width of the megaureters and minor renal calyces, the degree of hydronephrosis, and the serum urea and creatinine levels decreased significantly after the operation. The renal parenchyma thickness and the creatinine clearance level increased significantly.