Decreased Interstitial Cells of Cajal-like Cells, Possible Cause of Congenital Refluxing Megaureters: Histopathologic Differences in Refluxing and Obstructive Megaureters

Spontaneous resolution and the role of endoscopic surgery in the treatment of primary obstructive megaureter: a review of the literature

The megaureter accounts for almost a quarter of all urinary tract dilations diagnosed in utero and is the second leading cause of hydronephrosis in newborns, following pyeloureteral junction obstruction. The current standard treatment for progressive or persistent, symptomatic primary obstructive megaureter is ureteral anti-reflux reimplantation, which can be associated with ureteral remodeling or plication. Due to the associated morbidity, postoperative recovery challenges, and the complications that may arise from the open surgical approach, there has been a natural inclination towards validating new minimally invasive techniques. This study reviews the literature, extracting data from three major international databases, from 1998 to 2022. Out of 1172 initially identified articles, only 52 were deemed eligible, analyzing 1764 patients and 1981 renal units. Results show that 65% of cases required surgical intervention, with minimally invasive techniques constituting 56% of these procedures. High-pressure endoscopic balloon dilation was the preferred endourologic technique. The degree of ureterohydronephrosis is considered one of the factors indicating the need for surgery. There is an inverse relationship between the diameter of the ureter and the likelihood of spontaneous resolution. Conditions such as renal hypoplasia, renal dysplasia, or ectopic ureteral insertion strongly indicate a poor prognosis. Endoscopic surgical techniques for treating primary obstructive megaureter can be definitive, firstline treatment options. In selected cases, they might be at least as effective and safe as the open approach, but with advantages like quicker recovery, fewer complications, shorter hospital stays, and reduced costs.

Telocytes, c-Kit positive cells, Smooth muscles, and collagen in the ureter of pediatric patients with congenital primary obstructive megaureter: elucidation of etiopathology

Congenital primary obstructive megaureter (POM) is an uncommon pediatric anomaly that is due to obstructive distal ureter leading to the loss of peristalsis with consequent ureterohydronephrosis causing loss of kidney function. The objectives are to elucidate the etiology of POM by demonstrating the presence of interstitial cells of Cajal (ICC), telocytes, smooth muscles, and collage in the obstructive and dilated ureteral segments. The study was carried out on 15 surgical specimens of congenital POM in pediatric patients, age range was 4 to 24 months, they were operated upon by excision of the obstructed segment, tailoring the dilated ureter, and anastomosing it to the bladder. Specimens included the obstructed ureteral segment and part of the dilated ureter. Specimens were examined with hematoxylin and eosin (H&E) stain, Modified Gomori trichrome stain, immunohistochemistry (IHC) with α-muscle actin, and c-kit (CD117), and transmission electron microscopy (TEM). Obstructed segment showed excess collagen intervening between smooth muscles, excess c-Kit positive cells, and presence of telocytes. The dilated segment of the ureteral wall is formed of smooth muscle bundles with scanty collagen. Staining with c-Kit did not demonstrate positive cells. TEM showed myofibroblasts and close adherence of smooth muscle cells to each other with absence of telocytes. The pathophysiology of POM is multifactorial. Loss of interstitial cells and rarity of collagen result in loss of elasticity of dilated segment leading to massive dilatation. While the obstructed segment had no muscle conductivity due to excess collagen irrespective of presence of telocytes.

Erythropoietin promotes functional recovery via anti-apoptotic mechanisms in mouse unilateral ureteral obstruction

The purpose of the work was to investigate mechanisms of erythropoietin-induced protection and accelerated recovery of kidneys and ureters from obstructive injury. Unilateral ureteral obstruction was established for 24, 48, and 72 h in C57BL/6 mice using a non-traumatic micro-clip followed by the microscopic quantification of ureteral peristalsis pre- and post-obstruction. Expression of erythropoietin, erythropoietin receptor, β-common receptor, and downstream apoptosis-related markers was assessed by RT-PCR and immunohistochemistry in ureters and kidneys and compared to the respective organs on the contralateral side within each animal. Expression of genes in kidneys and ureters from mice treated with 20 IU of erythropoietin daily for 72 h prior to obstruction was compared to that of untreated mice following obstruction. Apoptosis in ureteral tissues after 72-h obstruction was assessed via TUNEL assay. Ureteral obstruction increased apoptosis in affected ureters, with peristaltic function halted following all periods of obstruction. Erythropoietin treatment suppressed apoptosis in obstructed tissues and increased the percentage of mice retaining ureteral function immediately following obstruction reversal. Erythropoietin, erythropoietin receptor, Bcl-2, and Bcl-xl mRNA expression were down-regulated, while phospho-Nf-ĸb p65 was up-regulated in ureteral epithelia following obstruction. Erythropoietin treatment induced anti-apoptotic signaling via down-regulated Bax mRNA expression and abrogated phospho-Nf-ĸb p65. Erythropoietin-induced protection of ureteral function and accelerated recovery post-obstruction removal is mediated via anti-apoptotic mechanisms. Ureteral function is disrupted even following obstruction removal, negatively affecting renal function due to delayed recovery. Thus, our results represent a potential target for the development of safe therapeutic agents aimed at improving functional recovery from obstructive injury.

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.

The search for the definition, etiology, and effective diagnosis of upper urinary tract obstruction: the Whitaker test then and now

INTRODUCTION

Robert Whitaker, inspired by Dr William W Scott at the Brady Institute at Johns Hopkins and by Sir David Innes Williams at Great Ormond Street Hospital for Children in the late 1960s, spent much of his career exploring the meaning of persistent dilatation of the upper urinary tract, in an attempt to define obstruction and to find a means of diagnosing it accurately.

OBJECTIVE

This is a historical review of Bob Whitaker's journey from his definition of obstruction to the inception of his eponymous test.

RESULTS

In 1975, he proposed a theory to explain the pathophysiology behind obstructive hydronephrosis and megaureter. He was among the first pediatric urologists to observe that 'it is wrong… to assume that dilatation necessarily indicates obstruction', a statement that was widely stated and even appeared in the textbooks at the time. He defined obstruction as 'an increased pressure in the pelvicalyceal system of the kidney at normal physiological flow rates such that the renal function is adversely affected'. This realization led to the development of a percutaneous pressure-measuring technique at controlled flows, later referred to as the Whitaker test. It predated and later assisted in the interpretation of diuretic renograms.

DISCUSSION

Whitaker questioned the etiology of 'hydronephrosis' and challenged other hypotheses proposed at the time, which often included causes of mechanical occlusion at the ureteropelvic junction (UPJ) or ureterovesical junction (UVJ). Whitaker's hypothesis is that 'obstruction' at UPJ and UVJ levels is not mechanical but the result of a failure of normal peristalsis to form and propagate a bolus. This, in turn, depends on the potentially abnormal distensibility of the renal pelvic and ureteric wall whether it be congenital or acquired. The aim of this review is to recall the history of the development of a technique to evaluate dilated upper urinary tracts and to re-evaluate various theories that might explain the etiology of the dilatation in the light of more recent evidence. Robert (or Bob, to his colleagues) Whitaker was among the founder members of the British Association of Paediatric Urologists, which now has more than 50 members, in 1992. Together with his colleagues Philip Ransley and David Thomas, Whitaker established the annual pediatric urology course for pediatric surgery and urology trainees in Cambridge, U.K., which still runs to this day. He retired from his surgical practice in 1990 and up until the present time has taught clinical anatomy in the Cambridge University School of Medicine.

The role of HCN channels in peristaltic dysfunction in human ureteral tuberculosis

Objective

To explore the role of HCN channels in ureteral peristaltic dysfunction by comparing the changes in HCN channel levels between normal and tuberculous ureters.

Methods

A total of 32 specimens of human upper ureters were collected by nephrectomy from patients with renal tumor (control group, n = 16) or from patients with renal tuberculosis (experimental group, n = 16); the two groups did not receive radiotherapy, chemotherapy, immunotherapy, or any other special treatment before the surgical procedure. An experimental study on smooth muscle strips of human upper ureters showed variation in contraction amplitude and frequency after adding ZD7288, a specific blocker of HCN channels. The expression of HCN channels in the ureter was confirmed by Western blot (WB) and by confocal analysis of double immunostaining for c-kit and HCN channel proteins.

Results

Before the addition of ZD7288, the experimental and control groups showed significant differences in the frequency and amplitude of the spontaneous contraction of isolated ureteral smooth muscle strips. After ZD7288 was added, the frequency and amplitude of the contractions of the ureteral smooth muscle strips were significantly lower in both groups. The differences observed before and after ZD7288 treatment in each group were significant (P < 0.001), and the difference in contraction amplitude observed between the two groups before ZD7288 was also significantly different (P < 0.001). By using WB technology, we showed that the expression of HCN channels was present in normal human ureters, with the expression of HCN4 and HCN1 being the highest; the expression of HCN4 and HCN1 in the control and experimental groups were both statistically significant (P < 0.001). HCN4 and HCN1 were expressed in the mucosal and smooth muscle layers of human control ureters and tuberculous ureters, as revealed by a confocal analysis of double immunostaining for c-kit and HCNs proteins; there were significant differences between the two groups (P < 0.001).

Conclusion

Four HCN channels are expressed in the ureter, mainly HCN4 and HCN1, suggesting that HCN channels are involved in the peristaltic contraction of ureteral ICCs, which may be an important reason for peristaltic dysfunction in ureteric tuberculosis.

Protein Kinase 2β Is Expressed in Neural Crest-Derived Urinary Pacemaker Cells and Required for Pyeloureteric Contraction

Nonobstructive hydronephrosis, defined as dilatation of the renal pelvis with or without dilatation of the ureter, is the most common antenatal abnormality detected by fetal ultrasound. Yet, the etiology of nonobstructive hydronephrosis is poorly defined. We previously demonstrated that defective development of urinary tract pacemaker cells (utPMCs) expressing hyperpolarization-activated cyclic nucleotide-gated channel 3 (HCN3) and the stem cell marker cKIT causes abnormal ureteric peristalsis and nonobstructive hydronephrosis. However, further investigation of utPMC development and function is limited by lack of knowledge regarding the embryonic derivation, development, and molecular apparatus of these cells. Here, we used lineage tracing in mice to identify cells that give rise to utPMCs. Neural crest cells (NCCs) indelibly labeled with tdTomato expressed HCN3 and cKIT. Furthermore, purified HCN3+ and cKIT+ utPMCs were enriched in Sox10 and Tfap-2α, markers of NCCs. Sequencing of purified RNA from HCN3+ cells revealed enrichment of a small subset of RNAs, including RNA encoding protein kinase 2β (PTK2β), a Ca²⁺-dependent tyrosine kinase that regulates ion channel activity in neurons. Immunofluorescence analysis in situ revealed PTK2β expression in NCCs as early as embryonic day 12.5 and in HCN3+ and cKIT+ utPMCs as early as embryonic day 15.5, with sustained expression in HCN3+ utPMCs until postnatal week 8. Pharmacologic inhibition of PTK2β in murine pyeloureteral tissue explants inhibited contraction frequency. Together, these results demonstrate that utPMCs are derived from NCCs, identify new markers of utPMCs, and demonstrate a functional contribution of PTK2β to utPMC function.

Long-Term Outcomes in Primary Obstructive Megaureter Treated by Endoscopic Balloon Dilation. Experience After 100 Cases

Aim: To assess long-term effectiveness, complications, and outcomes of primary obstructive megaureter (POM) treated by endoscopic balloon dilation (EBD) in the largest series reported. Patients and Methods: Hundred POM in 92 consecutive patients were treated by EBD between years 2004 and 2016. A total of 79 POM (73 patients) with more than 18 months of follow-up after treatment have been analyzed. EBD of the vesicoureteral junction was performed with semicompliant high-pressure balloon catheters (2.7FG) with minimum balloon diameter of 5 mm, followed by temporary Double-J stent placement. Follow-up protocol included periodical clinical reviews, US and MAG-3 renogram scans. Results: Median age at surgery was 4 months (15 days-3.6 years), with median operating time of 20 min (10-60) and hospital stay of 1 day (1-7). Initial renal function was preserved in all patients with significant improvement in renal drainage on the MAG-3 diuretic renogram after endoscopic treatment (p < 0.001 T-test). Significant post-operative differences were observed in hydronephrosis grade and ureteral diameter that were maintained in the long-term (p < 0.001 T-test). Endoscopic approach of POM had a long-term success rate of 87.3%, with a mean follow-up of 6.4 ± 3.8 years. Secondary VUR was found in 17 cases (21.5%), being successfully treated by endoscopic subureteral injection in 13 (76.4%). Nine cases developed long-term re-stenosis (12.2%) that were successfully treated with a new EBD in 8. Endoscopic management of POM failed in 10 cases (12.7%) that required ureteral reimplantation. Five were early failures (4 intraoperative technical problems and 1 double-J stent migration with severe re-stenosis), and 5 long-term (4 persistent VUR and 1 re-stenosis recurrence). Conclusion: EBD has shown to be an effective treatment of POM with few complications and good outcomes at long-term follow up. Main complication was secondary VUR that could also be treated endoscopically with a high success rate. In our opinion, EBD may be considered first-line treatment in POM.

Interstitial cell modulation of pyeloureteric peristalsis in the mouse renal pelvis examined using FIBSEM tomography and calcium indicators

Typical and atypical smooth muscle cells (TSMCs and ASMCs, respectively) and interstitial cells (ICs) within the pacemaker region of the mouse renal pelvis were examined using focused ion beam scanning electron (FIB SEM) tomography, immunohistochemistry and Ca²⁺ imaging. Individual cells within 500-900 electron micrograph stacks were volume rendered and associations with their neighbours established. 'Ribbon-shaped', Ano1 Cl^- channel immuno-reactive ICs were present in the adventitia and the sub-urothelial space adjacent to the TSMC layer. ICs in the proximal renal pelvis were immuno-reactive to antibodies for Ca_V3.1 and hyperpolarization-activated cation nucleotide-gated isoform 3 (HCN3) channel sub-units, while basal-epithelial cells (BECs) were intensely immuno-reactive to Kv7.5 channel antibodies. Adventitial to the TSMC layer, ASMCs formed close appositions with TSMCs and ICs. The T-type Ca²⁺channel blocker, Ni²⁺ (10-200 μM), reduced the frequency while the L-type Ca²⁺ channel blocker (1 μM nifedipine) reduced the amplitude of propagating Ca²⁺ waves and contractions in the TSMC layer. Upon complete suppression of Ca²⁺ entry through TSMC Ca²⁺ channels, ASMCs displayed high-frequency (6 min^-1) Ca²⁺ transients, and ICs distributed into two populations of cells firing at 1 and 3 min^-1, respectively. IC Ca²⁺ transients periodically (every 3-5 min^-1) summed into bursts which doubled the frequency of ASMC Ca²⁺ transient firing. Synchronized IC bursting and the acceleration of ASMC firing were inhibited upon blockade of HCN channels with ZD7288 or cell-to-cell coupling with carbenoxolone. While ASMCs appear to be the primary pacemaker driving pyeloureteric peristalsis, it was concluded that sub-urothelial HCN3(+), Ca_V3.1(+) ICs can accelerate ASMC Ca²⁺ signalling.

Altered expression of interstitial cells of Cajal in primary obstructive megaureter

OBJECTIVE

A marked decrease in the density of interstitial cells of Cajal (ICC) has been shown in patients with ureteropelvic junction obstruction. ICC may also play a role in primary obstructive megaureter (POM). An immunohistochemical study was conducted to investigate the density of ICC in ureterovesical junction (UVJ) segments resected from patients with POM and from control autopsy specimens.

MATERIALS AND METHODS

Resected UVJ segments from 11 patients operated for POM comprised the study group. Control UVJs were obtained from autopsy specimens of 7 children who died from causes other than urogenital pathology. The UVJs including the narrowest parts were studied using immunohistochemical staining for C-kit positive cells.

RESULTS

The number of ICC was significantly lower in the UVJs of the POM compared to the control group. The UVJs of the POM group had 1.75 ± 1.14 ICC (mean ± 1SD), whereas the control group had 5.76 ± 2.99 ICC (mean ± 1SD).

CONCLUSION

The number of ICC was decreased in the UVJs of the patients with POM compared to the normal control group. As dilation of the ureter during fetal life is a common condition and ureteral dilation is often self limiting, we hypothesize that ureteral peristalsis is a maturational event including the maturational development of ICC.

Identification of telocytes in the upper lamina propria of the human urinary tract

The upper lamina propria (ULP) area of interstitial cells (IC) has been studied extensively in bladder, but is rather unexplored in the rest of the urinary tract. This cell layer is intriguing because of the localization directly underneath the urothelium, the intercellular contacts and the close relationship with nerve endings and capillaries. In this study, we examine the ULP layer of IC in human renal pelvis, ureter and urethra, and we make a comparison with ULP IC in bladder. Tissue was obtained from normal areas in nephrectomy, cystectomy and prostatectomy specimens, and processed for morphology, immunohistochemistry and electron microscopy. A morphological and immunohistochemical phenotype for the ULP IC was assessed and region-dependent differences were looked for. The ULP IC in renal pelvis, ureter and urethra had a similar ultrastructural phenotype, which differed somehow from that of bladder IC, that is, thinner and longer cytoplasmic processes, no peripheral actin filaments and presence of dense core granules and microtubules. Together with their immunohistochemical profile, these features are most compatible with the phenotype of telocytes, a recently discovered group of stromal cells. Based on their global ultrastructural and immunohistochemical phenotype, ULP IC in human bladder should also be classified as telocytes. The most striking immunohistochemical finding was the variable expression of oestrogen receptor (ER) and progesterone receptor (PR). The functional relevance of ULP telocytes in the urinary tract remains to be elucidated, and ER and PR might therefore be promising pharmacological research targets.

Potassium and ANO1/ TMEM16A chloride channel profiles distinguish atypical and typical smooth muscle cells from interstitial cells in the mouse renal pelvis

BACKGROUND AND PURPOSE

Although atypical smooth muscle cells (SMCs) in the proximal renal pelvis are thought to generate the pacemaker signals that drive pyeloureteric peristalsis, their location and electrical properties remain obscure.

EXPERIMENTAL APPROACH

Standard patch clamp, intracellular microelectrode and immunohistochemistry techniques were used. To unequivocally identify SMCs, transgenic mice with enhanced yellow fluorescent protein (eYFP) expressed in cells containing α-smooth muscle actin (α-SMA) were sometimes used.

KEY RESULTS

Atypical SMCs were distinguished from typical SMCs by the absence of both a transient 4-aminopyridine-sensitive K(+) current (I(KA) ) and spontaneous transient outward currents (STOCs) upon the opening of large-conductance Ca(2+) -activated K(+) (BK) channels. Many typical SMCs displayed a slowly activating, slowly decaying Cl(-) current blocked by niflumic acid (NFA). Immunostaining for K(V) 4.3 and ANO1/ TMEM16A Cl(-) channel subunits co-localized with α-SMA immunoreactive product predominately in the distal renal pelvis. Atypical SMCs fired spontaneous inward currents that were either selective for Cl(-) and blocked by NFA, or cation-selective and blocked by La(3+) . α-SMA(-) interstitial cells (ICs) were distinguished by the presence of a Xe991-sensitive K(V) 7 current, BK channel STOCs and Cl(-) selective, NFA-sensitive spontaneous transient inward currents (STICs). Intense ANO1/ TMEM16A and K(V) 7.5 immunostaining was present in Kit(-) α-SMA(-) ICs in the suburothelial and adventitial regions of the renal pelvis.

CONCLUSIONS AND IMPLICATIONS

We conclude that K(V) 4.3(+) α-SMA(+) SMCs are typical SMCs that facilitate muscle wall contraction, that ANO1/ TMEM16A and K(V) 7.5 immunoreactivity may be selective markers of Kit(-) ICs and that atypical SMCs which discharge spontaneous inward currents are the pelviureteric pacemakers.

Magnetic resonance urography and X-ray urography findings of congenital megaureter

OBJECTIVE

To observe the imaging findings of congenital megaureter in order to enhance the understanding of this disease.

METHODS

Image data of 5 patients with congenital megaureter and 2 misdiagnosed patients were analyzed, and image findings of congenital megaureter were summarized.Elscint Prestig 2.0T superconductive magnetic resonance urography (MRU) with conventional sequence (spin-echo, T1WI560 ms/16 ms; fast spin-echo, T2WI 9600 ms/96 ms ) was performed. Raw data were acquired with fastspin-echo sequence from heavy T2-weighted image (9600 ms/120 ms). Post-processing method of MRU was the maximum intensity projection with three-dimensional reconstruction in the workstation. Intravenous pyelography (IVP) was conducted, in which X-rayfilms were taken 7 minutes, 15 minutes, and 30 minutes after injecting contrast agent, exceptthat in 2 patients the films were taken delayed at 60 and 90 minutes .X-ray retrograde pyelography was performed on 2 patients, successful in one butfailed in the other.

RESULTS

The dilated ureter showed hypointensity on T1-weighted images and hyperintensity on T2-weighted images in conventional MRI. The mass wall was intact, uniform in thickness, and showing hypointensity on T1-weighted and T2-weighted images. The MRU images showed a retroperitoneal mass appearing as an elongated tubular cystic structure spreading from kidney to bladder. MRU also revealed dilated calices and renal pelvis, pelviureteric obstruction, and renal duplication. The main signs of congenital megaureter in X-urography was significant dilatation of ureter, or normal renal pelvis with ureter dilatation, hydronephrosis, deformity, and displacement.

CONCLUSIONS

MRU with X-urography could visualizethe characteristics of congenital megaureter, including the dilation of renal pelvis and ureter, calculi, urinary tract duplication, and stenosis location. The two techniques can complement each other in disease diagnosis and provide more detailed information for preoperative treatment.

Endoscopic placement of double-J ureteric stents in children as a treatment for primary obstructive megaureter

AIM

To determine the efficacy and potential complications of double-J ureteric stents in the treatment of persistent or progressive primary obstructive megaureter in pediatric patients within our institution.

MATERIALS AND METHODS

A retrospective case-note review of all patients with double-J ureteric stents, between 1997 and 2004, was performed. In all, 38 stents were inserted in 31 patients aged between 2 months and 15 years of age. Complications and results of follow-up investigations and the need for follow-up investigations were recorded. Patients were followed up clinically and radiologically for a minimum of 2 years following stent insertion.

RESULTS

Endoscopic placement of double-J ureteric stents in childhood is straightforward and complications are uncommon (8/38 insertions). In non-resolving or progressive primary non-refluxing megaureter, double-J ureteric stenting alone is effective with resolution of primary non-refluxing megaureter in 66% of cases (25/38 insertions).

CONCLUSIONS

Ureteric stenting provides an alternative to early surgery in patients with primary non-refluxing megaureter. The youngest patient in our series was 2 months old at the time of endoscopic ureteric double-J stent insertion. Endoscopic placement of ureteric double-J stents should be considered as a first-line treatment in the management of persistent or progressive non-refluxing megaureter leading to progressive hydronephrosis or pyonephrosis.

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.

Effects of mechanical stretch on interstitial cells of Cajal in guinea pig bladder

OBJECTIVES

C-kit positive interstitial cells of Cajal (ICCs) play an important role in the regulation of the smooth muscle motility. In this study, we investigated the mechanical sensitivity of ICCs in guinea pig bladder and their possible relationship with detrusor overactivity (DO).

METHODS

Stretch load was performed in vivo in DO models produced by 4 wk of partial bladder outlet obstruction (PBOO). Number and morphology of ICCs were examined using a specific ICC marker, c-kit, immunochemistry staining. The spontaneous and stretch-induced calcium transients (SICT) of ICCs were investigated in cells cultured onto flexible silicone membranes preloaded with the Ca(2+) indicator fluo-4AM in vitro.

RESULTS

C-kit positive ICCs were mainly located along and between bladder smooth muscle bundles. ICCs in DO bladders displayed more lateral branching with mutual connections. The number of c-kit positive bladder ICCs was increased in the DO group compared with the control group (n = 50, P < 0.05). Cultured ICCs from DO bladders showed spontaneous calcium waves with higher frequency and lower amplitude than those from control bladders (n = 15, P < 0.05). Significant SICT were detected in cultured bladder ICCs. SICT generated in ICCs from DO were more likely to transfer to adjacent smooth muscle cells through cell membrane connection than ICCs from control bladders.

CONCLUSIONS

Long-term overload tension following PBOO caused changes in morphology, quantity and spontaneous calcium transients of ICCs in guinea pig bladder. Mechanical sensitivity and interaction with SMC of ICCs may contribute to the mechanosensitive conductances in bladder regulation, and may play a role in the pathogenesis of DO.

Functions of ICC-like cells in the urinary tract and male genital organs

Interstitial cells of Cajal (ICC)-like cells (ICC-LCs) have been identified in many regions of the urinary tract and male genital organs by immunohistochemical studies and electron microscopy. ICC-LCs are characterized by their spontaneous electrical and Ca²⁺ signalling and the cellular mechanisms of their generation have been extensively investigated. Spontaneous activity in ICC-LCs rises from the release of internally stored Ca²⁺ and the opening of Ca²⁺-activated Cl⁻ channels to generate spontaneous transient depolarizations (STDs) in a manner not fundamentally dependent on Ca²⁺ influx through L-type voltage-dependent Ca²⁺ channels. Since urogenital ICC-LCs have been identified by their immunoreactivity to Kit (CD117) antibodies, the often-used specific marker for ICC in the gastrointestinal tract, their functions have been thought likely to be similar. Thus ICC-LCs in the urogenital tract might be expected to act as either electrical pacemaker cells to drive the smooth muscle wall or as intermediaries in neuromuscular transmission. However, present knowledge of the functions of ICC-LCs suggests that their functions are not so predetermined, that their functions may be very region specific, particularly under pathological conditions. In this review, we summarize recent advances in our understanding of the location and function of ICC-LCs in various organs of the urogenital system. We also discuss several unsolved issues regarding the identification, properties and functions of ICC-LCs in various urogenital regions in health and disease.