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Revista chilena de anatomía

versión impresa ISSN 0716-9868

Rev. chil. anat. v.15 n.2 Temuco  1997

http://dx.doi.org/10.4067/S0716-98681997000200012 

INGUINAL RINGS: A MORPHOMETRIC STUDY ON BRAZILIAN MALE NEWBORNS

ANILLOS INGUINALES: UN ESTUDIO MORFOMETRICO EN VARONES
RECIEN NACIDOS BRASILEÑOS

 

*
**
Fernandes, G. J. M.
Prates, J. C.

* Disciplina de Anatomía de la Facultad de Ciências Médicas de Santos (Fundação Lusíada)
** Disciplina de Anatomía Descriptiva de la UNIFESP Escola Paulista de Medicina

SUMMARY:Although of most importance for pediatricians and pediatric surgeons, the inguinal region of male newborns has never been steadily studied in a morphometric view. Our investigation was performed in order to measure the diameters of the inguinal rings (internal and external) and to determine their exact relative position.

We used 30 fixed bodies of Brazilian male newborns, chosen randomly, from the Laboratories of Anatomy of the Faculty of Medical Sciences of Santos and UNIFESP - EPM. The dissection of the inguinal region was carried out in a classical way and the diameters of the inguinal rings were taken and their relative position observed.

Our data confirmed that exact superposition of inguinal rings is quite rare in male newborns, the majority of them having a wellformed inguinal canal at birth. The diameters of both inguinal rings show no significant differences in size (one to another) nor in comparison to both sides of the body.

KEY WORDS: 1. Anatomy; 2. Inguinal region; 3. Male newborns.

INTRODUCTION

The inguinal region deserves a special attention from pediatricians and pediatric surgeons because of the high frequency of pathologies inciding in it, affecting mainly the male newborn. World-wide data demonstrate that the incidence of congenital inguinal hernia ranges from 1 to 3% in general population, favoring males in a proportion of 9 to 1 and that this disease is considered the most common surgical condition on children of all ages. Of these, 60% present on the right side, 15% on the left and 25% are bilateral and the cause for this significant antimeric difference is imputed to the delayed migration of the right testicle, presumably due to timingslowness in the shortening of the gubernaculum testis on this side in relation to the left one (WHITE et al., 1970; COX, 1985; GROSS, 1971; RICKHAM et al., 1975; ROWE et al., 1969 and RAFFENSPERGER, 1980).

The fact that, in all senses, newborns can not be considered as an adult miniature was already wellknown and stablished in the beginning of this century (HECKER, 1933 and MAHN, 1933) but only recently their anatomy and physiology has been studied with much more interest (MAKHANI & CHAURASIA, 1964), bringing forth a new medical specialty, the Neonatology.

Anatomically, the newborn inguinal region does not differ much from that of the adults for it is formed by the same fascial and muscle-aponeurotic structures (STEVENSON & JOHNSON, 1967; AMARAL, 1979 and CRELIN, 1988). The basic gross anatomy of the inguinal canal is similar in adults and children but in the latter, mainly in neonates, it is shorter (concerning the whole body dimension) and more vertically positioned (CONDON, 1967; BILLI, 1974 and RAFFENSPERGER). As a result of this peculiar anatomical feature, the external (superficial) inguinal ring lies almost directly in front of the internal (deep) one (GROSS, 1971; RAFFENS-PERGER and COX).

Another distinguished anatomic caractheristic is that the posterior wall of the newborn inguinal canal, compared to the adult one, is more resistant and aparently bears no fragile structures (RICKHAM et al.). Due to the protrusion of the processus vaginalis around the gubernaculum testis, the opening of the internal (deep) inguinal ring starts at the end of the 2nd month of intrauterine life. Surrounding this orifice, a loop formed by the fascia transversalis (the interfoveolar ligament) begins to develop by the 5th month and about the 7th month it is quite formed and able of a valvularlike function. This valvular-like structure on the internal (deep) inguinal ring, supporting a great amount of pressure, acts as an effective closing device, protecting some pervious processus vaginalis for months or years and preventing the onset of indirect inguinal hernias (LYTLE, 1970; FOWLER, 1975).

VERGNES et al. (1985) studied the growth and development of the inguinal canal in children and affirmed that the genesis of this structure would be the same in male or female human embryos and that sexual differences of the inguinal canal occur much lately. Thus, the testicular migration inside generally begins at the 32th week of intra-uterine life but the structures of the inguinal canal and its internal (deep) ring are already defined about the 24th week. These authors found a straight relation between the lenght of the inguinal canal and the iliac-pubic distance (from the anterior-superior iliac spine and the pubic tubercle). This observation let them conclude that the growth of the inguinal canal is dependent of the pelvic bonyframe.

Nevertheless, no efforts were ever intended for measuring the inguinal rings (on both sides) on male newborns, in order to settle whether there is a real complete superposition (and so, no welldefined inguinal canal) that could be a predisposing factor in the incidence of congenital inguinal hernia, and also, if the ring's dimensions are significantly different. Considering this lack of information in the medical literature, we performed a morphometric study on these rings, trying to obtain some position/dimension data that could contribute to the investigation of the genesis of congenital inguinal hernia.

MATERIAL AND METHOD

Our sample consisted of 30 fixed bodies of Brazilian male newborns, white and nonwhite, selected randomly at the Anatomical Laboratories of two Medical Schools (UNIFESP - EPM and FCMS). The specimen were restricted according to their pregnancy age (equal or above 32 weeks), height (equal or above 49 cm) and weight (equal or above 2.700 g) and presenting, at inspection, no inguino-scrotal pathology. In respect to the skin color, we got 15 specimen classified as white and other 15 as non-white and all of them were considered as ectipes in the groups.

Mean and standard deviation (SD) of our material were: age, 39,7±1,88 weeks; height, 50,6±1,24 cm and weight, 3.100±188,78 g. In a level of significance of .05 (in a two-tailed test) the data showed to be non-significant. (Table I)

For fixation, we used the following solution:

Formaldehide 40%       =   20 ml
Alcohol 95%                =   20 ml
Cloral hidrate 1%         =   20 ml
Sodium sulphate 5%     =   20 ml
Destiled water              =   312 ml
Phenic acid 20%          =   4 ml
Glicerine                      =   4 ml

The dissection was carried out in a classical way, as follows:

1 - Tegumental layer - skin and subcutaneous tissue dissection for exposing of the aponeurosis of the external oblique muscle.

2 - Aponeurotic layer - section and flapping of aponeurosis and exposure of the inguinal ligament and the external (superficial) inguinal ring.

3 - Muscular layer - section and flapping of the external, internal oblique and transversus muscles with exposure of the fascia transversalis and the internal (deep) inguinal ring.

For greater precision, the measurement procedures were kept under magnifying lenses (x 4) and the measures were taken with a paquimeter 0.05 mm gap.

The maximum transversal diameter of each inguinal ring was measured and compared with each other, homo and contralaterally and all mean and SD data checked for statistical significancy in a twotailed test (test "t").

RESULTS

On the right side, for the external (superficial) inguinal ring we got 6,2 ± 0,5 mm and for the internal (deep) inguinal ring, 5,7 ± 0,4 mm. (Tabela II).

On the left side, for the external (superficial) inguinal ring we got 6,4± 0,5 mm and for the internal (deep) inguinal ring, 5,9 ± 0,5 mm. (Tabela III).

Considering a gap of more than 1 mm to make the transversal diameter of the inguinal rings non-coincidents, we found 7 (seven) cases of supposed superposition, 2 (two) on the right and 5 (five) on the left side. Out of these, there was only 1 (one) case that presented itself bilaterally. According to the skin color, each group had 3 (three) cases (the bilateral one was on the non-white group).

 

TABLE I Distribution of sample for age, weight, height and skin color. São Paulo, Brazil, 1996.

CASE Nº

AGE (wks)

WEIGHT (g)

HEIGHT (cm)

SKIN COLOR


1

39,0

3.010

51,0

W

2

39,5

3.050

50,8

W

3

40,4

3.180

51,1

W

4

41,3

3.200

51,8

    NW

5

36,8

2.820

48,6

    NW

6

42,4

3.360

52,2

    NW

7

39,8

3.150

50,7

W

8

38,6

2.950

49,7

W

9

36,8

2.800

48,5

W

10

42,6

3.380

52,0

W

11

38,2

3.050

50,0

    NW

12

37,7

2.860

49,1

W

13

40,2

3.200

51,3

W

14

39,4

3.060

50,6

W

15

39,1

3.140

50,3

    NW

16

40,1

3.260

51,1

W

17

42,0

3.270

52,5

    NW

18

41,0

3.180

51,7

    NW

19

39,0

3.080

50,2

    NW

20

43,0

3.450

53,0

    NW

21

38,5

2.950

49,9

W

22

37,2

2.830

48,9

W

23

38,8

2.990

49,8

    NW

24

38,0

2.950

49,5

    NW

25

43,0

3.470

53,0

    NW

26

36,5

2.760

48,8

W

27

39,6

3.110

50,9

    NW

28

41,4

3.210

50,0

    NW

29

41,6

3.220

50,5

W

30

39,2

3.070

50,3

    NW


Mean ± SD
 39,7±1,88
   3.100±188,78
        50,6±1,24
 

 

TABLE II Diameters taken from the right inguinal rings. São Paulo, Brazil, 1996.

CASE Nº
RIGHT EXTERNAL
RIGHT INTERNAL
 
INGUINAL RING (mm)
INGUINAL RING (mm)

  1

6,1

5,3

  2

6,4

5,6

  3

6,8

6,0

  4

6,9

6,2

  5

6,0

5,4

        6 (*)

6,1

5,5

  7

6,0

5,4

  8

6,2

5,6

  9

5,8

5,2

10

6,4

5,9

11

6,3

5,7

12

6,2

5,8

13

6,1

5,8

14

6,0

5,5

15

6,5

5,9

16

6,7

6,2

17

6,8

6,2

18

5,9

5,5

19

6,0

5,5

     20(*)

6,8

6,4

21

5,5

5,0

22

6,2

5,7

23

5,6

5,1

24

5,7

5,1

25

6,9

6,2

26

5,6

5,1

27

6,0

5,6

28

5,6

5,2

29

6,5

5,9

30

6,3

5,8


Mean ± SD
         6,2 ± 0,5
         5,7 ± 0,4

 

TABLE III Diameters taken from the left inguinal rings. São Paulo, Brazil, 1996.

CASE Nº
LEFT EXTERNAL
LEFT INTERNAL
 
INGUINAL RING (mm)
INGUINAL RING (mm)

  1

6,3

5,5

  2

6,5

5,7

      3(*)

6,9

6,2

  4

7,0

6,3

  5

5,9

5,2

        6 (*)

6,2

5,7

  7

6,3

5,6

  8

6,4

6,1

       9(*)

5,7

5,1

10

6,6

6,0

     11(*)

6,7

6,2

12

6,5

6,0

13

6,3

5,8

14

6,2

5,8

15

6,8

6,2

16

7,0

6,3

17

7,1

6,5

18

6,2

5,8

19

6,3

5,8

20

7,1

6,8

21

5,7

5,2

22

6,4

6,0

23

5,7

5,3

24

5,9

5,4

25

7,2

6,8

    26(*)

5,5

5,0

27

6,2

5,9

28

5,6

5,3

29

6,8

6,3

30

6,7

6,2


             Mean ± SD
         6,4 ± 0,5
         5,9 ± 0,5

(*) = exact superposition of external and internal inguinal rings

DISCUSSION

Concerning the exact and complete superposition of the inguinal rings in newborns, the authors in medical literature agreed that it is not a constant and common finding (CURTI, 1972; COX; CONDON; AMARAL, 1979 and RAFFENSPERGER) and this feature would turn the neonate's inguinal canal into an actual and specific anato-mical structure, although presenting itself much shorter and vertical than in adults. In our study, we found only 7 cases (11,6%) in which the inguinal rings were considered as superpositioned (the gap between their position was less than 1 mm). As the mean of previous processus vaginalis in pediatric age varies from 2 to 20% (RAFFENSPERGER), our data showed to be pertinent. This situation was more evident at the left side (5 against 2) and only one newborn (case 6) showed a bilateral superposition. These data confirmed the rare frequency of that particular disposition and the fact that the newborn already presents a welldefined inguinal canal. Interestingly, the higher incidence of congenital inguinal hernia is on the right side (60%) but we found the majority of features of inguinal ring superposition on the left. If a well-defined formation of an inguinal canal should be one out of many factors of preventing hernias, why that condition appeared on the contrary ? This should be object of further studies.

RESUMEN: Este estudio, pretende mejorar el conocimiento sobre las dimensiones y la disposición de los anillos inguinales en varones recién nacidos brasileños, considerando que en la literatura anatómica y clínica no existe claridad en estos aspectos, y que esta región es de gran importancia para pediatras y cirujanos.

La investigación se realizó en 30 cadáveres fijados de varones recién nacidos, escogidos al azar, provenientes del Laboratorio de Anatomía de la Facultad de Ciencias Médicas de Santos y de la UNIFESP - Escola Paulista de Medicina, ambos en São Paulo, Brasil.

La disección de la región inguinal fue realizada con lupa. Se registraron los calibres de los anillos inguinales interno (profundo) y externo (superficial) con paquímetro de precisión. También fue observada la posición relativa de cada uno de los anillos con la finalidad de identificar su exacta sobreposición o la formación de un pequeño canal inguinal. Luego, los datos fueron analizados estadísticamente.

Nuestros resultados mostraron que no existen diferencias significativas en los tamaños de los anillos inguinales superficiales y profundos, cuando se relacionan entre sí o, cuando se realiza la comparación homo o contralateral. La exacta sobreposición es rara y lo más común fue el hallazgo de un canal inguinal bién formado.

PALABRAS CLAVE: 1. Anatomía; 2. Región inguinal; 3. Recién nacido varón.

REFERENCES

AMARAL, H. A. B. Anatomía quirúrgica del recién nacido. Barcelona, Jims, 1979.         [ Links ]

BILLI, L. P. Hernia inguinal en el lactante. In CASSARETTO, V. Hernia Inguinal. Barcelona, Salvat, 1974.         [ Links ]

CONDON, R. E. Anatomía de la región inguinal y su relación con las hernias de la ingle. In NYHUS, L. M. & HARKINS, H. N. Hernia. Buenos Aires, Intermédica, 1967.         [ Links ]

COX, J. A. Inguinal hernia of childhood. S. Clin. North America, 65:1331-42, 1985.         [ Links ]

CRELIN, E. S. Anatomia do recémnascido. São Paulo, Panamericana. 1988.         [ Links ]

CURTI, P. Cirurgia pediátrica. São Paulo, Sarvier, 1972.         [ Links ]

FOWLER, R. The applied surgical anatomy of the peritonial fascia of the groin and the secondary internal inguinal ring. Aust. N. Z. J. Surg., 45:8-14, 1975.         [ Links ]

GROSS, R. E. Atlas de cirugía infantil. Barcelona, Salvat, 1971.         [ Links ]

HECKER, E. M. Anatomía del recién nacido. Rev. Chil. Pediat., 5:1-50, 1933.         [ Links ]

LYTLE, W. J. The deep inguinal ring: development, function and repair. Brit. J. Surg., 57:531-6, 1970.         [ Links ]

MAHN, E. Anatomía del recién nacido. Arch. Chil. Morfol., I:59-172, 1933.         [ Links ]

MAKHANI, J. S. & CHAURASIA, B. Anatomy of the child. Indian J. Pediatrics, 31:69-80, 1964.         [ Links ]

RAFFENSPERGER, J.G. Swenson's pediatric surgery. 4 ed. New York, Appleton-Century-Crofts, 1980.         [ Links ]

RICKHAM, P.P.; SOPER, R.T. & STAUFFER, U.G. Synopsis of Pediatric Surgery. Year Book Medical Publishers, 1975.         [ Links ]

ROWE, M. I.; COPELSON, L.W & CLATWORTHY, H. W. The patent processus vaginalis and the inguinal hernia. J. Ped. Surg., 4:102-7, 1969.         [ Links ]

STEVENSON, J. K. & JOHNSON, L. P. Hernias de la ingle en infantes y niños. In NYHUS, L. M. & HARKINS, H.N. Hernia. Buenos Aires, Intermédica, 1967.         [ Links ]

VERGNES, P.; MIDY, D.; BONDONNY, J. M. & CABANNIE, H. Anatomical basis of inguinal surgery in children. Anat. Clin., 7:257-65, 1985.         [ Links ]

WHITE, J. J.; HALLER, J. A. & DORST, J. P. Congenital inguinal hernia and inguinal herniography. S. Clin. North America, 50:823-37, 1970.         [ Links ]

Dirección para correspondencia:
Prof. Dr. Geraldo José Medeiros Fernandes
Rua Dr. Guedes Coelho, 96 Ap. 34B
11050-230
Santos -SP
BRASIL

Recibido : 26-08-1997
Aceptado : 30-10-1997