Thomas D. Clarnette

Incomplete Disappearance of the Processus Vaginalis as a Cause of Ascending Testis

PURPOSE Recently evidence has been accumulating that some undescended testes present later in childhood after apparent normalcy in infancy. These ascending testes appear to explain why a significant number of orchiopexies are performed later in childhood despite the recommendation that surgery for cryptorchidism be performed in infancy. We aimed to determine whether the cause of these ascending testes was persistence of the processus vaginalis. MATERIALS AND METHODS A total of 25 boys 4 to 13 years old with no history of testicular maldescent at birth underwent transscrotal orchiopexy in a 2-year period. A total of 33 orchiopexies was performed (8 bilateral). The spermatic cord was carefully dissected and operative findings of the nature of the spermatic cord were noted. RESULTS In all cases dissection within the spermatic cord revealed a similar finding, namely a fibrous string situated deep to the cremasteric muscle and spermatic fasciae. Transection of this string allowed adequate elongation of the vas deferens and gonadal vessels to permit scrotal placement of the testis. Histological examination revealed characteristic processus vaginalis tissue in which the peritoneal derived mesothelial lining cells were present within a partially obliterated processus vaginalis. CONCLUSIONS Cryptorchidism presenting later in childhood may be an acquired abnormality caused by failure of natural growth of the spermatic cord when the processus vaginalis leaves a fibrous remnant, which prevents normal elongation. These observations suggest that the ascending testis is acquired postnatally and the cause may be related to inguinal hernia.

Ventriculo-peritoneal shunts in children reveal the natural history of closure of the processus vaginalis

Abstract Purpose: Little information is known about the natural history of closure of the processus vaginalis. The authors studied children who had ventriculoperitoneal shunts to determine the natural history of closure of the processus vaginalis and to better understand the role of intraabdominal pressure in the etiology of congenital inguinal hernia. Materials and Methods: A retrospective review of all children undergoing insertion of ventriculoperitoneal shunts between 1985 and 1995 at the Royal Childrens Hospital was undertaken. In each case, the sex, the cause of hydrocephalus, the age at insertion of the shunt, and the subsequent development of an inguinal hernia or hydrocele was recorded. Results: There were 430 children in the study. An inguinal hernia developed in 15% of children after insertion of a ventriculoperitoneal shunt, and a hydrocele developed in an additional 6% of boys. Inguinal hernias were bilateral in 47% of boys and 27% of girls. The incidence of subsequent development of an inguinal hernia or hydrocele was closely related to the age of insertion of the ventriculoperitoneal shunt, being 30% during the last 8 weeks of gestation and the first few months of life, then falling quite sharply to reach about 10% at 1 year. Conclusions: The high occurrence of inguinal hernias and hydroceles after ventriculoperitoneal shunt insertion supports the role of raised intraabdominal pressure in the etiology of these conditions. It appears that raised intraabdominal pressure is associated with an increased incidence of clinical hernias, but not with increased incidence of patency of the processus vaginalis. The development of an inguinal hernia or hydrocele after inserton of a ventriculoperitoneal shunt can be used as an indirect marker of patency of the processus vaginalis at the time of insertion of the shunt. From this, we propose that the processus vaginalis remains patent in at least 30% of children in the first few months of life, after which time the patency rate appears to fall off quite sharply.

Is the ascending testis actually 'stationary'? Normal elongation of the spermatic cord is prevented by a fibrous remnant of the processus vaginalis.

The processus vaginalis (PV) forms as a peritoneal diverticulum within the gubernaculum testis to allow the testis to exit from the abdominal cavity. Failure of its closure leads to inguinal hernias and hydroceles. Ascending testis, which is likely to be an acquired form of undescended testis, may also be part of the spectrum of failure of regression of the PV At orchidopexy for cryptorchidism in older boys with a history of a scrotal testis in infancy, we find that the PV persists as a fibrous string, preventing normal elongation of the vas deferens and gonadal vessels with increasing size of the boy. We propose that the ascending testis is actually ‘stationary’, and is caused by persistence of a fibrous remnant of the PV Seen in this light, ascending testes are directly related to inguinal hernias.

In vitro fusion of human inguinal hernia with associated epithelial transformation.

The processus vaginalis (PV) is a peritoneal diverticulum which forms to allow descent of the fetal testis to the scrotum. During human development fusion and obliteration of the PV often fails to occur with the result that inguinal hernias are the most prevalent congenital abnormality requiring surgery in childhood. Androgen is proposed to regulate testicular descent via the genitofemoral nerve which releases the neuropeptide calcitonin gene-related peptide (CGRP). It is possible that subsequent fusion of the PV and tissue remodelling following descent is indirectly controlled by androgen via CGRP action. An organ culture assay was developed to assess fusion of the PV taken from inguinal herniotomy in infants. Fusion was induced in vitro by CGRP but not by CGRP 8–37, CGRP 27–37 or dihydrotestosterone in equimolar concentrations. Fusion was accompanied by transformation of the epithelium, as shown by staining of intermediate filament proteins, cytokeratin and vimentin. Localization studies for CGRP receptors on 25 specimens indicated CGRP acts on mesenchymal fibroblasts but not directly on PV epithelium suggesting an indirect pathway. Hepatocyte growth factor/scatter factor was found to induce fusion of PV and may be involved as an intermediate molecule in the fusion cascade. This study represents the first approach to understanding the humoral control and underlying mechanism by which the PV fuses.

Does the gubernaculum migrate during inguinoscrotal testicular descent in the rat

The role of the gubernaculum in descent of the testis is controversial. The mechanism of testicular descent has been studied in the rat, because inguino‐scrotal descent occurs postnatally in this species. Several authors have claimed that the cremasteric sac forms by eversion of the gubernacular cone, whereby regression of the extra‐abdominal part of the gubernaculum creates a space into which the gubernacular cone everts to form the processus vaginalis within the scrotum. This postulated lack of any gubernacular migration phase contrasts with the situation in the human, where gubernacular migration appears to be an integral component of testicular descent. This study was designed to determine in the rat whether there is any gubernacular migration toward the scrotum during testicular descent, or whether eversion of the cremasteric sac alone could account for the extension of this sac into the bottom of the scrotum.

Exogenous calcitonin gene-related peptide can change the direction of gubernacular migration in the mutant trans-scrotal rat.

PURPOSE The mutant trans-scrotal (TS) rat shows unilateral or bilateral suprainguinal testes in more than 70% of males. Calcitonin gene-related peptide (CGRP) has been proposed as the neurotransmitter released from the genitofemoral nerve (GFN), which controls gubernacular migration to the bottom of the scrotum during inguinoscrotal descent. Results of previous studies in this rat suggest a down-regulation of CGRP receptors in gubernaculum occurring caused by excess release of the neuropeptide from the GFN. The aim of this study was to test the hypothesis that division of the GFN in neonatal TS rats, potentially allowing the gubernaculum to become sensitive to CGRP, followed by exogenous CGRP injections, would change the direction of gubernacular migration and the final position of the testis. METHODS Four study groups were used: group 1 (n = 43), sham operation, in which the peritoneal cavity was opened and the left genitofemoral nerve was exposed but not divided, and oil injections into left hemiscrotum; group 2 (n = 70), division of left GFN and CGRP injections into left hemiscrotum; group 3 (n = 36), sham operation and CGRP injections into left hemiscrotum; group 4 (n = 30), division of left GFN and oil injections into left hemiscrotum. RESULTS In group 2 (GFN division and CGRP injection), 18 testes were located in a position not previously described in this model. In 16 (23%) rats, the testis was located at the entrance of the internal inguinal ring with the gubernaculum directed down toward the scrotum. This contrasts with the normal position of the testis in the superficial inguinal pouch, where the testis is located superficial to the external oblique muscle, with the gubernaculum directed craniolaterally. In two (3%) rats, there was incomplete descent of the testis. In group 3 (sham operation and CGRP injection), two (6%) testes were located at the internal ring. The remaining testes in the above groups and all of the testes in groups 1 and 4 were found in either the superficial inguinal pouch, completely descended, or adherent to scar tissue. CONCLUSIONS These findings suggest that division of the GFN in neonatal TS rats followed by CGRP injections into the scrotum can change the direction of gubernacular migration in the TS rat. The effectiveness of this experimental model is limited by the inability to accurately localize injected CGRP into the scrotum.

Factors Affecting the Development of the Processus Vaginalis in the Rat

PURPOSE We examined the factors that influence development of the processus vaginalis in the rat. MATERIALS AND METHODS Neonatal Sprague-Dawley rats 0 to 3 days old underwent distal or proximal gubernaculotomy, unilateral orchiectomy or proximal genitofemoral nerve transection. At ages 28 to 60 days the rats were sacrificed, position of the testis was noted and length of the processus vaginalis was measured. RESULTS There was no development of the processus vaginalis after distal gubernaculotomy. Proximal gubernaculotomy enabled the processus vaginalis to achieve a mean length similar to that of controls (p = 0.06) when the testis descended into the scrotum. Mean length of the processus after proximal gubernaculotomy with an abdominal testis, surgical orchiectomy and torsion of the testis after proximal gubernaculotomy was similar (p = 0.9) but less than that of controls (p < 0.05). Proximal division of the genitofemoral nerve produced variable results depending on how and when the surgical procedure was performed, and whether the psoas muscle was divided. CONCLUSIONS Distal attachment of the gubernaculum is essential for normal development of the processus vaginalis. Distal gubernaculotomy prevents development of the processus vaginalis because of mechanical disruption of the gubernaculum. Proximal attachment is not essential for normal development of the processus vaginalis but it serves to anchor the testis to the region of the internal inguinal ring, allowing intra-abdominal pressure to facilitate descent of the testis. In the presence of an innervated gubernaculum the processus vaginalis achieves greater length when the testis descends into the scrotum, suggesting that its complete development demands the presence of a testis in the sac. The timing of genitofemoral nerve division may be crucial in determining the subsequent effect on the development of the processus vaginalis and testicular descent, since programming of the gubernaculum by calcitonin gene-related peptide released from the genitofemoral nerve appears to occur just before birth in the rat.

The development and closure of the processus vaginalis

SummaryIt is now well known that the failure of the processus vaginalis (PV) to close off following descent of the testis not only accounts for nearly all inguinal hernias of childhood [Rothenberg et al, 1953], but also for other common congenital conditions of childhood such as scrotal hydroceles and encysted hydroceles of the cord. Despite the direct relationship of the PV to these conditions and its intimate association with the mechanism of testicular descent, surprisingly little is known about this important structure. It is not known, for instance, how the PV develops, what precise role it plays in testicular descent, what makes it close, or exactly when it closes. The purpose of this paper is to review the past and present literature on the PV, examining specifically its role in testicular descent, its postulated modes of development, and the mechanisms of its closure and disappearence following descent of the testis.

Ventriculo-Peritoneal Shunts in Children Reveal the Natural History of Closure of the Processus Vaginalis

PURPOSE Little information is known about the natural history of closure of the processus vaginalis. The authors studied children who had ventriculoperitoneal shunts to determine the natural history of closure of the processus vaginalis and to better understand the role of intraabdominal pressure in the etiology of congenital inguinal hernia. MATERIALS AND METHODS A retrospective review of all children undergoing insertion of ventriculoperitoneal shunts between 1985 and 1995 at the Royal Childrens Hospital was undertaken. In each case, the sex, the cause of hydrocephalus, the age at insertion of the shunt, and the subsequent development of an inguinal hernia or hydrocele was recorded. RESULTS There were 430 children in the study. An inguinal hernia developed in 15% of children after insertion of a ventriculoperitoneal shunt, and a hydrocele developed in an additional 6% of boys. Inguinal hernias were bilateral in 47% of boys and 27% of girls. The incidence of subsequent development of an inguinal hernia or hydrocele was closely related to the age of insertion of the ventriculoperitoneal shunt, being 30% during the last 8 weeks of gestation and the first few months of life, then falling quite sharply to reach about 10% at 1 year. CONCLUSIONS The high occurrence of inguinal hernias and hydroceles after ventriculoperitoneal shunt insertion supports the role of raised intraabdominal pressure in the etiology of these conditions. It appears that raised intraabdominal pressure is associated with an increased incidence of clinical hernias, but not with increased incidence of patency of the processus vaginalis. The development of an inguinal hernia or hydrocele after insertion of a ventriculoperitoneal shunt can be used as an indirect marker of patency of the processus vaginalis at the time of insertion of the shunt. From this, we propose that the processus vaginalis remains patent in at least 30% of children in the first few months of life, after which time the patency rate appears to fall off quite sharply.