Age-related changes in inguinal region anatomy from 0 to 19 years of age.

Knowledge of the age-related changes in inguinal region anatomy is essential in pediatric urological and abdominal surgery, yet little is published. This study aimed to determine the position of inguinal region structures and growth of the surrounding pelvis and inguinal ligament in subjects from 0 to 19 years of age. Anonymized contrast-enhanced CT DICOM datasets of 103 patients (63 male: 40 female) aged from 0 to 19 years had left and right sides analyzed by three independent observers. Exclusion criteria were applied. Growth of the pelvis and inguinal ligament were determined using fixed bony reference points. The position of the deep inguinal ring and femoral vasculature were determined as ratio of inguinal ligament length, measured from the anterior superior iliac spine. Growth of the pelvis in vertical and horizontal dimensions and of the inguinal ligament followed a positive polynomial relationship with increasing age, with no observed increase in growth rate during puberty. From 0 to 19 years, the deep inguinal ring moved superolaterally with respect to the inguinal ligament (from 0.74 to 0.60 of the distance along the inguinal ligament) and the femoral artery and vein moved medially (from 0.50 to 0.58, and 0.61 to 0.65 of the distance along the inguinal ligament, respectively). The position of the femoral artery, vein, and deep inguinal ring followed a logarithmic relationship with age. No significant left:right side or male:female differences were observed. From 0 to 19 years of age the femoral vasculature and deep inguinal ring change position as the pelvis grows around them. Clin. Anat. 32:794-802, 2019. © 2019 Wiley Periodicals, Inc.

Identification and Multilineage Potential Research of a Novel Type of Adipose-Derived Mesenchymal Stem Cells from Goose Inguinal Groove.

Adipose tissue-derived mesenchymal stem cells (ADSCs) play a crucial role in the field of regenerative medicine and tissue repair for its own unique features. However, up to date, the isolation and characterizations of multidifferentiation potentials of goose ADSCs are still uncertain. In this study, we successfully isolated ADSCs from goose inguinal groove in vitro for the first time and also attempted to unravel its fundamental differentiation potentials and genetic characteristics. The results showed that isolated ADSCs exhibited a typical fibroblast-like morphology and high proliferative potential, could be passaged for at least 40 passages and maintained high hereditary stability with more than 92.2% of cells were diploid (2n = 78) by G-banding analysis. Moreover, the ADSCs could express pluripotent marker gene (OCT4) and mesenchymal stem cells-related surface antigens, which are similar to previously reported human ADSCs. Additionally, the goose ADSCs could be induced to transdifferentiate into cells of three layers in vitro, such as osteoblasts, chondrocytes, and adipocytes derived from mesoderm, neurocytes from ectoderm, and hepatocytes of the endoderm. Most of all, we confirmed that the induced ß-like cells and hepatocytes had metabolic functions similar to normal cells in vivo. Taken together, these results demonstrated the multidifferentiation potentials of ADSCs in vitro, which conferred an appealing candidate for cell regenerative therapy.

Left-sided cryptorchidism in mice with Wilms' tumour 1 gene deletion in gubernaculum testis.

A significant number of patients with germline mutations in the Wilms' tumour 1 (WT1) gene, a transcriptional factor essential for early renal and gonadal development, display cryptorchidism or non-scrotal testis position. We show here that WT1 is expressed during development in the mouse gubernacular ligament connecting the testis to the abdominal wall. Conditional inactivation of Wt1 in the gubernaculum (GU-WT1KO animals) resulted in abnormal differentiation of the gubernacula during development and, in about 40% of adult males, unilateral, always left-sided, cryptorchidism. At birth the right testis was positioned above the processus vaginalis and eventually moved into the developing scrotal pouch. In affected mutants the left testis was displaced from the normal position and the left processus vaginalis failed to form. The analysis of testicular descent at different stages of postnatal development suggests that unilateral cryptorchidism might be caused by asymmetry in the positions of the abdominal organs providing a higher degree of mobility for the left testis. Spermatogenesis in GU-WT1KO animals was blocked in cryptorchid testes located in a high pararenal position, but was maintained in testes located in a low abdominal position. Conditional inactivation of both Wt1 and androgen receptor (Ar) genes in the gubernaculum led to a bilateral asymmetrical cryptorchidism in all mutant males, with the left testis again located higher than the right one. The malformations induced by WT1 and AR deficiency in the gubernaculum and processus vaginalis, in combination with mechanical constraints on testis descent, determine the final position of the testes. In summary, our data indicate that WT1 is directly involved in gubernaculum differentiation. Taken together, the results of the study underline the complex nature of testicular descent, with an involvement in this process of several genetic factors and developmental events.

Development of the gubernaculum during testicular descent in the rat.

Gubernacular elongation during inguinoscrotal testicular descent and cremaster muscle development remains poorly described in mammals. The role of the genitofemoral nerve (GFN) remains elusive. We performed detailed histological analysis of testicular descent in normal rats to provide a comprehensive anatomical description for molecular studies. Fetuses and neonatal male offspring (5-10 per group) from time-mated Sprague-Dawley dams (embryonic days 15, 16, and 19; postnatal days 0, 2, and 8) were prepared for histology. Immunohistochemistry was performed for nerves (Class III tubulin, Tuj1) and muscle (desmin). At embryonic days 15 and 16, the gubernaculum and breast bud are adjacent and both supplied by the GFN. By embryonic day 19, the breast bud has regressed and the gubernacular swelling reaction is completed. Postnatally, the gubernacular core regresses, except for a cranial proliferative zone. The cremaster is continuous with internal oblique and transversus abdominis. By postnatal day 2 (P2), the gubernaculum has everted, locating the proliferative zone caudally and the residual mesenchymal core externally. Eversion creates the processus vaginalis, with the everted gubernaculum loose in subcutaneous tissue but still remote from the scrotum. By P8, the gubernaculum has nearly reached the scrotum with fibrous connections attaching the gubernaculum to the scrotal skin. A direct link between GFN, gubernaculum, and breast bud suggests that the latter may be involved in gubernacular development. Second, the cremaster muscle is continuous with abdominal wall muscles, but most of its growth occurs in the distal gubernacular tip. Finally, gubernacular eversion at birth brings the cranial proliferative zone to the external distal tip, enabling gubernacular elongation similar to a limb bud.

The antiandrogen flutamide perturbs inguinoscrotal testicular descent in the rat and suggests a link with mammary development.

AIM: Inadequate androgen activity is a likely cause of cryptorchidism in humans, affecting inguinoscrotal testicular descent. Flutamide, a nonsteroidal antiandrogen, produces cryptorchidism in rats. We aimed to determine the anatomical and histologic effects of flutamide. METHODS: Time-mated Sprague-Dawley female rats were injected subcutaneously with flutamide (75 mg/kg in sunflower oil) on days 16 to 19 of pregnancy. Embryonic (E) and postnatal (P) male offspring were collected (E16, E19, P0, P2, P4, P8) in control and flutamide-treated groups (n = 5-10). Samples were fixed in 4% paraformaldehyde. Five-micrometer-thick sections were prepared for hematoxylin and eosin, trichrome and immunohistochemical stains (Desmin, TuJ1, Ki67). This identified muscle and neural cells and areas of cell proliferation. RESULTS: Postnatally, the gubernaculum in flutamide-treated rats had more mesenchyme and muscle than controls. Gubernacular eversion failed, and mammary tissue persisted around the gubernaculum in flutamide-treated rats. Flutamide had no effect on embryonic gubernacular anatomy and histology. CONCLUSIONS: Prenatal androgens altered postnatal gubernacular anatomy and histology in the postnatal period. Our findings indicate that the failure of gubernacular differentiation and migration may be because of the ongoing presence of mammary tissue in the region of the external inguinal ring.

The migrating gubernaculum grows like a "limb bud".

BACKGROUND: The gubernaculum is crucial for testicular descent, and in the second, or inguinoscrotal, phase of descent it has no caudal attachments. Cranially, it is attached to the testis, but its caudal free tip migrates to the scrotum controlled by the genitofemoral nerve. Recent studies show active proliferation in the tip. We hypothesized that the gubernacular tip may grow like a limb bud. METHODS: We performed whole-mount in situ hybridization studies on male and female fetal mice (ages, E14.5-E18.5; n = 162) looking for limb bud regulatory factors. RESULTS: Our results showed that a member of the fibroblast growth factor (Fgf) family, Fgf10, and Hoxa10 were both expressed in the male gubernaculum at E14.5, and Hoxa10 was also expressed in the E16.5 mice. Weak staining was seen in the female gubernaculum for Hoxa10 on days E14.5 and E16.5, whereas no staining for Fgf10 was seen in the female gubernaculums. CONCLUSIONS: These studies, although preliminary, suggest limb bud regulators are essential for gubernacular growth. Hox genes and Fgfs may be fruitful areas of research to unravel the molecular control of gubernacular migration during testicular descent.

Pediatric inguinal hernia repair-a critical appraisal.

Inguinal hernia repair in infants and babies is a routine operation, but many issues have not been addressed scientifically. Thus, it is not known, e.g., if all children with a hernia should be operated on, what is the best timing of surgery, or if the operation should be performed with an open approach or laparoscopically. The review is a critical discussion of these and other issues in pediatric herniorrhaphy pointing out the need for further research.

The anatomy of the cremaster muscle during inguinoscrotal testicular descent in the rat.

BACKGROUND: Extrapolation of rat testicular descent studies to humans has been criticized because of anatomical differences of the cremaster muscle. Human cremaster is described as a thin strip rather than a large, complete sac as in rats, which is proposed to be more important in propelling the testis during descent. This study investigated cremaster muscle anatomy and ontogeny in both normal and cryptorchid rat models. METHODS: Gubernacula from 4 groups of neonatal rats were sectioned longitudinally and transversely: normal Sprague-Dawley, capsaicin pretreated, flutamide pretreated, and congenital cryptorchid rats. Gubernacula were stained with hematoxylin-eosin, Masson trichrome, and desmin immunohistochemistry to study muscle development. RESULTS: Myoblasts are more numerous at the gubernacular tip, whereas the most differentiated muscle is proximal. Rat cremaster develops as an elongated strip rather than a complete sac derived from abdominal wall muscles. Flutamide and capsaicin pretreatment disrupts development. CONCLUSION: Rat cremaster muscle develops as a strip, bearing close resemblance to human cremaster muscle, permitting extrapolation of cremaster function to human testicular descent. The cremaster muscle appears to differentiate from the gubernacular tip during elongation to the scrotum, and requires intact sensory innervation and androgen.

A novel incision for groin pathologies in children: the low inguinal groove approach.

BACKGROUND: The traditional approach to pediatric inguinal pathologies has been the suprapubic transverse inguinal incision. Alternative incisions for better cosmetic results may be considered. MATERIALS AND METHODS: The recently defined "low inguinal groove incision" was used in a consecutive series of 483 children having indirect groin hernias, hydroceles, and palpable undescended testes, etc. The neonates, infants, and children were operated on as elective day surgery cases. RESULTS: All children ended with excellent cosmetic and functional results. There were no complications or morbidity apart from a recurrence of an inguinal hernia in a 7 year-old boy. In addition to the series of girls reported earlier, this novel surgical incision has further been employed in boys with excellent results.

Surgical treatment of inguinal herniae in children.

The aim of this paper was to assess if there is a standard technique for the repair of inguinal herniae in children and to establish if the inguinal canal should be routinely opened during this procedure in different age groups. A postal survey was conducted by sending questionnaires to 264 consultant surgeons who were surgical tutors or advisors to the Royal College of Surgeons of England. Information was sought using a multiple-choice tick-box questionnaire. The surgical techniques of surgeons working in specialist units were compared with those working in general units, and comparisons were also drawn between surgeons performing more operations than those doing only a few and also if the technique varied with the age of the patient. The response rate was 69%. Only 23% working in specialist units and 8% from general units performed more than 30 herniotomies per year. Overall, 15% of surgeons always performed the operation through the inguinal canal, 56% performed it superficial to the external ring, and 29% tended to do both. In children under the age of 2 years, most surgeons performed the operation superficial to the external ring, although a higher proportion of surgeons at specialist units opened the inguinal canal routinely. In the older age groups, the tendency to open the inguinal canal and/or divide the external ring was greater. However, surgeons at specialist paediatric units and those performing more than 30 herniotomies in a year were more likely to open the inguinal canal without dividing the external ring in all age groups. There was quite obviously no standard surgical technique for inguinal herniotomy in children in this survey, and there are only trends.

Role of the gubernacular bulb in cremaster muscle development of the rat.

The role of the gubernaculum during the inguino-scrotal phase of testicular descent remains controversial. Some authors propose involution and eversion while others suggest active migration, although the site of growth is unknown. We aimed to determine whether the gubernacular bulb is actively proliferating or regressing during inguino-scrotal testicular descent in the rat. Gubernacula were removed from Sprague-Dawley rats and congenitally-cryptorchid TS mutant rats. Animals (0, 3, 7, 10, and 11 days of age) were treated with bromodeoxyuridine (BUdR) 2 hr before they were killed. BUdR incorporation into newly synthesized DNA served as a marker of cell division. The gubernacula were histologically processed for hematoxylin-eosin (H&E) and immunoperoxidase staining. Four different areas within the gubernaculum were examined for BUdR-positive cells: area 1: plica gubernaculi (cord); area 2: pars infravaginalis gubernaculi (bulb); area 3: distal part of the cremaster muscle; and area 4: proximal part of the cremaster muscle. The rate of cell division for each of these areas was determined by counting the number of BUdR-positive cells per 100 cells. The highest rate of BUdR labeling in both types of rats was in area 2, which is the tip of the gubernacular bulb, and this was significantly greater (P < 0.0001) than in the gubernacular cord or developing cremaster muscle. The mitotic activity was also noted to be significantly greater (P < 0.0001) at the distal end of the cremaster muscle than at the proximal end. The amount of mitosis decreased significantly (P < 0.01) in areas 2 and 4 of the gubernaculum in Sprague-Dawley rats across the period studied. This trend was not observed in TS rats. Our results suggest that the bulb actively proliferates after birth, with possible differentiation into new cremaster muscle cells. We propose that the bulb is the growing end of the elongating gubernaculum, analogous to the growth of a limb bud.

Effect of an anti-androgen on testicular descent and inguinal closure in a marsupial, the tammar wallaby (Macropus eugenii).

Androgens are essential for testicular descent in eutherian mammals, but little is known about its hormonal control in marsupials. This study reports the effects of daily treatment with the anti-androgen flutamide (10 mg kg(-1)) from day 9 to day 75 after birth on the descent of the testis and inguinal closure in tammar wallabies. By day 75 after birth, the testes of control males had descended and the prostate gland was well developed. The testes of all flutamide-treated males had passed through the inguinal canal and were situated in the base of the scrotum. Three of the nine flutamide-treated males had unilateral inguinal hernias. The size of the inguinal canal, regardless of whether a hernia was present, was significantly wider than that of control males. Development of the prostate gland was significantly inhibited. By day 75 after birth, the phallus was significantly longer in control males than in females, whereas the phallus of flutamide-treated males was similar to that of control females. In flutamide-treated males, the lumbar 1 dorsal root ganglia was feminized and significantly fewer cell bodies expressed calcitonin gene- related peptide. As the anti-androgen treatment resulted in a reduction in the number of calcitonin gene-related peptide-positive cell bodies in the dorsal root ganglion supplying the genitofemoral nerve, the process of inguinal closure in tammar wallabies may be mediated by calcitonin gene-related peptide via the genitofemoral nerve, as indicated in humans. Flutamide treatment inhibited development of the prostate gland and phallus, which are both androgen-dependent structures, but it did not affect the normal descent of the testis, indicating that testicular descent can proceed when the action of androgens is blocked.

Enlargement of the processus vaginalis during testicular descent in rats.

The role of the processus vaginalis (PV) during inguinoscrotal testicular descent remains controversial. Some authors propose passive dragging of the PV by the migrating testis, while others suggest active elongation. In addition, the exact site of growth is unknown. Our aim was to determine whether the PV actively proliferates at its tip or stretches passively during the inguinoscrotal phase of descent in the rat. Gubernacula were removed from Sprague-Dawley (SD) rats and congenitally-cryptorchid TS mutants. Animals (at days 3, 7, 10, and 11) were treated with bromo-uridine deoxyribose (BUdR) 2 h before death. BUdR incorporation into newly-synthesised DNA served as a marker for cell division. The gubernacula were processed for haematoxylin and eosin and immunoperoxidase staining. Three sites were examined: (1) the tip of the PV on either side of the gubernacular bulb; (2) the proximal gubernacular cord; and (3) the proximal parietal PV. At each site, 50 adjacent cells were counted and the number of positive cells recorded. The highest BUdR labelling in SD rats was at the tip (site 1) on day 3 (17/50) compared with sites 2 (11/50) and 3 (9/50) (P < 0.05). Labelling decreased by 7 and 11 days to similar levels in all three sites. In TS rats, labelling rates were lower at day 3 and were highest at the tip at day 11. These results suggest active growth of the caudal tip of the PV during testicular descent. In normal rats, the growth rate slows as the testis approaches the scrotum. By contrast, in TS rats growth continued longer. We propose that the PV elongates actively from the tip to allow the intraperitoneal testis to leave the abdomen in a special peritoneal diverticulum.

Individual and associated effects of length of inguinal canal and caliber of the sac on clinical outcome in children.

PURPOSE: The caliber of processus vaginalis is accepted to define the clinical outcome to be an inguinal hernia or hydrocele not based on any evaluation. The caliber of sacs and length of inguinal canals of boys and girls were evaluated to define the relation of sex, age, and the diagnosis with caliber of the sac and the length of inguinal canal. METHODS: A total of 217 inguinal canals in 24 girls and 112 boys with inguinal hernia, 30 boys with hydrocele or hydrocele of the cord, and 31 boys with undescended testis have been evaluated. Twenty patients had bilateral involvement. The length of inguinal canal, and the circumference of the sac were measured. A formula was developed to predict the length of inguinal canal according to the age and sex. The circumferences of the sacs, length of inguinal canals, and the ratios of the circumference to the length were compared according to the clinical pictures. RESULTS: The regression model of the relationship between the age and the length of the inguinal canal is an equation of third degree (inguinal canal in millimeters) = 0.0000119 x age 3 (months) - 0.00292 x age 2 (months) + 0.3168 x age (months) + 19.979 (r2 = 0.47). Inguinal canal is longer in boys (25.133 and 27.996 mm; P = .018), and length does not differ among diagnoses but differs according to age showing a linear growth after 24 months. Although the circumference as a sole parameter could classify only 55.3% of boys correctly, the ratio of length of inguinal canal to circumference of the sac has been the significant parameter in classifying boys into 1 of 3 groups including inguinal hernia, undescended testis, and hydrocele with a 70.2% success rate. CONCLUSIONS: Inguinal canal that shows a linear growth after 24 months of age is longer in boys. Caliber is not the unique factor that determines the clinical outcome. Although the ratio of length of inguinal canal to the circumference of the sac defines the clinical picture best, even this parameter cannot classify the cases correctly. Therefore, some factors in addition to the caliber and length of inguinal canal might have roles in determining the clinical outcome.

Does the gubernaculum migrate during inguinoscrotal testicular descent in the rat?

BACKGROUND: 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. METHODS: Oblique sagittal sections of the inguino-perineal region were taken from rats aged 21 days of gestation and days 1, 3, 4, 6, 8, and 10 days postnatally. Histological sections were examined and the following measurements were obtained: gubernacular cone height, gubernaculum-scrotum distance, processus vaginalis length, and pubic symphysis-anus distance. RESULTS: The gubernaculum was not in close proximity to the developing scrotum at any age. After 21 days of gestation, there was little evidence of a substantial gubernacular bulb distal to the processus vaginalis. At all ages the gubernacular cone height was significantly less than the distance from the gubernaculum to the scrotum. CONCLUSIONS: These results show that the gubernaculum does not develop in close proximity to the developing scrotum. Even if complete eversion of the gubernaculum takes place, the gubernaculum would still fail to reach the bottom of the scrotum. It is proposed that gubernacular eversion is more apparent than real and that some degree of gubernacular migration is needed for complete extension of the cremasteric sac to the bottom of the scrotum.

Anatomical landmarks of the inguinal canal in prepubescent children.

BACKGROUND: Most adult anatomical texts state that the deep inguinal ring is situated midway between the anterior superior iliac spine and the pubic tubercle. The aim of this study was to determine if this was true in prepubescent children. METHODS: A total of 107 inguinal ligaments and canals were measured during inguinal operations in 80 children (68 boys, age range 1-118 months). RESULTS: The length of the inguinal ligament increased from a median of 4.3 cm (range 3.6-6.8) at less than 1 year of age to 7.5 cm (range 6.7-10.1) at over 4 years of age. The internal ring was situated medial to the midpoint of the inguinal ligament throughout childhood. The ratio of internal ring to public tubercle over inguinal ligament length was 42% (range 27-58) at less than 2 years; and 34% (range 25-46) at over 4 years. The inguinal canal remained short (median 1 cm (range 0.7-1.1) at less than 2 years, and median 1.1 cm (range 0.7-2.3) at over 4 years) suggesting that growth of the inguinal region in this age group occurs outside the canal. CONCLUSIONS: These results have implications for the siting of incisions, and question the necessity of opening the inguinal canal in children.

Is inguinal hernia a defect in human evolution and would this insight improve concepts for methods of surgical repair?

In Homo sapiens sapiens and many mammalian quadrupeds, there is an absence of the posterior rectus sheath below the arcuate line (of Douglas) and an insubstantial transversalis fascia in the groin. This anatomical arrangement presents no particular functional anatomic difficulty for quadrupeds as their inguinal canal is directed "uphill" during ambulation and therefore is not subjected to significant gravitational stress. In humans, however, gravitational stress necessitated by erect posture, including bearing the weight of the intra-abdominal organs directed toward the lower abdomen, considerably amplifies this intrinsic anatomic weakness. It allows a significant number of pathologic inguinal hernias, both direct and indirect, to become clinically manifest and associated with a coincident increase in morbidity and mortality, especially in patients with strangulated hernias and/or delayed treatment. The morbidity is associated with a significant national economic loss secondary to work hour loss from pain, discomfort, surgical treatment, and rehabilitation following therapy. The mortality is usually associated with strangulation, especially in those in patients with delayed treatment. The lack of the evolutionary development of a strong posterior rectus sheath and transversalis fascia in the lower abdomen is thought to represent a significant specific anatomic defect in the evolution of humankind. If so, then perhaps methods for surgical repair will be directed toward correction of this defect and avoid, not encourage, such methods as the utilization of the weak or absent transversalis "fascia," which are doomed to a high recurrence rate, or other methods that are unnecessarily complicated, such as certain laparoscopic repairs of inguinal hernia.

Anatomical basis of inguinal surgery in children.

This paper begins with a review of the embryology of the inguinal region. The authors then point out the special morphological and topographical features of the inguinal canal in male children. These observations were based on the study of 50 inguinal canals from male children. From the anatomical observations described in this study guidelines are proposed for the surgical approach and dissection of the spermatic cord used in the treatment of congenital hernias or abnormal descent of the testis.