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Individual and associated effects of length of inguinal canal and caliber of the sac on clinical outcome in children
Individual and Associated Effects of Length of Inguinal Canal and Caliber of the Sac on Clinical Outcome in Children ¨ cal, Ergun Karaag˘aog˘lu, and Nebil Bu¨yu¨kpamukc¸u By F. Cahit Tanyel, Turgay O Ankara, Turkey
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 ⫻ age3 (months) ⫺ 0.00292 ⫻ age2 (months) ⫹ 0.3168 ⫻ age (months) ⫹ 19.979 (r2 ⫽ 0.47). Inguinal canal is longer in boys
C
ONGENITAL HYDROCELE (H) and congenital inguinal hernia (IH) are among frequent problems encountered in children. The difference between a H and a IH usually is accepted to be the caliber of the processus vaginalis (PV).1 However, in almost all of the boys with undescended testis (UT), the PV shows a patency of varying calibers.2 Despite the patency of the PV, IH or H does not frequently associate to the clinical picture in boys with UT.3 Furthermore, the presence of a patent PV does not mandate the occurrence of an IH.4 The role of caliber is accused as an axiom, and the relationship of the clinical picture to the caliber never has been evaluated. Inguinal canal is suggested to be one of the structures that differs among boys and girls.5 However, the length of inguinal canal usually has been accepted to remain short in children without considering a sex difference.6 Furthermore, the length of inguinal canal at different ages according to the sexes has not been evaluated thoroughly in the literature. Therefore, a clinical study has been planned to determine the length of inguinal canals at various ages in both sexes and the caliber of sacs in inguinal pathologies to evaluate if the length or caliber or any of their relations Journal of Pediatric Surgery, Vol 35, No 8 (August), 2000: pp 1165-1169
(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. J Pediatr Surg 35:1165-1169. Copyright r 2000 by W.B. Saunders Company. INDEX WORDS: Inguinal canal, inguinal hernia, hydrocele, cryptorchidism.
either differ according to the age, sex, and diagnosis or influence the clinical outcome. MATERIALS AND METHODS Boys and girls operated on for IH and boys operated on for H and UT were evaluated. Patients with only 1 pathology finding were included in the study group, and patients with coexisting pathology findings such as boys with both UT and IH in the same side were excluded. All of the operations were performed by or under the supervision of the same author. The anterior wall of the inguinal canal was opened routinely. The sacs were dissected up to the preperitoneal fat tissue and double ligated. After high ligation, a string was placed into the inguinal canal. One end of the string was located to the suture used for high ligation close to the abdominal cavity. The external inguinal ring was marked on the string, and the length of inguinal canal, which was accepted to be the distance from the tip of the string to the mark, was measured by a ruler (Fig 1A). The sac excised after high ligation was opened longitudinally,
From the Departments of Pediatric Surgery, Anesthesiology, and Biostatistics, Hacettepe University, Faculty of Medicine, Ankara, Turkey. Address reprint requests to F. Cahit Tanyel, MD, Hacettepe University, Faculty of Medicine, Department of Pediatric Surgery, 06100, Ankara, Turkey. Copyright r 2000 by W.B. Saunders Company 0022-3468/00/3508-0004$03.00/0 doi:10.1053/jpsu.2000.8719
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the sac, length of inguinal canal, the ratio of length of inguinal canal to the circumference of the sac, in classifying boys into 1 of 3 diagnostic groups including IH, H, and UT, a stepwise discriminant analysis was performed.
RESULTS
A total of 24 girls and 112 boys with IH, 30 boys with H or hydrocele of the cord, and 31 boys with UT have been evaluated for the current study. A total of 10 boys and 5 girls have presented with bilateral IH, and 5 boys have presented with bilateral UT. Thus, a total of 217 inguinal canals have been evaluated (Table 1). When all of the 217 inguinal canals independent of the sex or the side have been evaluated through the Pearson correlation analysis, a significant correlation has been encountered between the age and the length of the inguinal canal (correlation r ⫽ 0.66, P ⬍ .001). If a linear relation is supposed to exist between the age and the length of the inguinal canal, the regression equation is: the length of inguinal canal (millimeters) ⫽ 21.745 ⫹ 0.136 ⫻ age (in months). The r2 for this model is 0.43. If both girls and boys are evaluated together, the regression model that defines best the relation between the age and the length of inguinal canal, appears to be an equation of third degree (r2 ⫽ 0.47). According to this model, the equation is: the length of inguinal canal (millimeters) ⫽ 0.0000119 ⫻ age3 (in months) ⫺ 0.00292 ⫻ age2 (in months) ⫹ 0.3168 ⫻ age (in months) ⫹ 19.979. Among boys and girls who are at or younger than 24 months of age, the r2 ⫽ 0.309. This suggests that there is no significant relation between the age and the length of inguinal canal until 24 months of age. However, the length of the inguinal canal increases with age after 24 months. The relationship between the age and the length of inguinal canal among boys and girls who are at or older than 25 months of age can be defined by the length of inguinal canal (millimeters) ⫽ 23.954 ⫹ 0.112 ⫻ age (in months). The correlation between age and the length of the canal is significant among girls (r ⫽ 0.611, P ⫽ .000). The
Fig 1. Schematic explanation of the measurements of length of inguinal canal (A) and circumference of the sac (B).
and the circumference of the sac at its closest end to the abdominal cavity was measured by a ruler (Fig 1B). Although the circumference is not constant throughout a sac, the circumference was measured and evaluated at a point at which the caliber plays the role in determining the content and clinical outcome. The lengths of inguinal canals in boys and girls according the ages in months were evaluated independently of the clinical diagnoses. The lengths at similar ages were compared and evaluated. The lengths of inguinal canals of right and left sides were compared to find out if the side influences the length of the inguinal canal. Means, standard deviations, and 95% confidence intervals were found either for the whole group or for subgroups where necessary. Analysis of variance and t test were used for group comparisons. When analysis of variance yielded a significant difference between groups, Least Significant Difference (LSD) test was used to detect the group or groups that differ significantly from the others. Because high correlation was observed between age and other parameters, age has been taken as a covariate, and covariance analysis was performed to test the significance of the difference between the groups, after adjusting the parameter of age. Observed and adjusted group means were displayed in such analysis. Pearson correlation coefficient has been used for assessing the magnitude of the relationships, and regression analysis (linear and non-linear) was performed to study the nature of the relationship between variables and to predict the length of inguinal canal by using the age as the predictor variable. Model fit was tested by using analysis of variance, and r2 were supplied to show the success of the model in explaining the change in the dependent variable. To find out the values of parameters, which include circumference of
Table 1. The Minimum and Maximum Values and the Distribution of Parameters According to Diagnoses Among Sexes Age (mo) Groups
No.
Female hernia (Right) 18 Female hernia (Left) 11 Male hernia (Right) 75 Male hernia (Left) 47 Hydrocele (Right) 19 Hydrocele (Left) 11 Undescended testis (Right) 19 Undescended testis (Left) 17 Total 217
Mean ⫾ SD
Length of Canal (mm)
Minimum Maximum
Mean ⫾ SD
Circumference of Sac mm)
Minimum Maximum
Mean ⫾ SD
Length/ Minimum Maximum Circumference
52.33 ⫾ 41.77 35.45 ⫾ 33.65 28.98 ⫾ 32.75 28.93 ⫾ 35.89 52.16 ⫾ 27.20 60.91 ⫾ 47.54
2 2 1 2 13 4
144 108 132 144 108 132
25.72 ⫾ 6.39 25.18 ⫾ 9.34 25.50 ⫾ 7.06 25.83 ⫾ 8.75 30.95 ⫾ 6.16 30.73 ⫾ 9.26
15 14 10 11 20 17
37 43 40 43 42 51
29.94 ⫾ 09.76 30.55 ⫾ 11.03 30.16 ⫾ 13.37 33.00 ⫾ 14.84 10.53 ⫾ 04.86 10.55 ⫾ 05.87
12 18 9 3 3 4
50 50 80 70 20 22
0.97 ⫾ 0.47 0.88 ⫾ 0.34 1.00 ⫾ 0.49 1.04 ⫾ 0.98 3.86 ⫾ 2.47 3.86 ⫾ 2.30
70.10 ⫾ 45.87
24
168
31.89 ⫾ 8.32
21
52
23.37 ⫾ 19.58
5
84
2.50 ⫾ 1.82
68.71 ⫾ 41.39 41.60 ⫾ 39.50
18 1
156 168
31.81 ⫾ 8.08 27.33 ⫾ 8.09
22 10
52 52
21.00 ⫾ 15.64 26.75 ⫾ 15.14
5 3
60 84
2.42 ⫾ 1.46 1.63 ⫾ 1.60
CANAL LENGTH AND SAC CALIBER
linear regression equation, which is found to be highly significant for the length of inguinal canal among girls is (in millimeters) ⫽ 20.149 ⫹ 0.117 ⫻ age (in months). If the girls are divided into 2 groups, those 24 months of age or younger and those 25 months or older, the correlation between the age and length of inguinal canal decreases and lacks the significance in both of the groups (for those 24 months or older, r ⫽ 0.156, P ⫽ .628, and for those older, r ⫽ 0.408, P ⫽ .104). If the length of inguinal canals only among boys are evaluated (n ⫽ 188), the correlation between the age and the length of inguinal canal becomes more obvious (correlation r ⫽ 0.677). If a linear regression is supposed to exist between the age and the length of inguinal canal, the regression equation is: the length of inguinal canal (millimeters) ⫽ 21.959 ⫹ 0.14 ⫻ age (in months). Observed points fit very well to this model (r2 ⫽ 0.458, P ⬍ .001). The relationship between the age and the length of inguinal canal among boys who are 24 months or younger (r ⫽ 0.327, P ⫽ .002) is less significant than that of boys who are equal or older than 25 months of age (r ⫽ 0.595, P ⫽ .000). Although the linear regression equation for boys who are equal or younger than 24 months of age is the length of inguinal canal (millimeters) ⫽ 20.24 ⫹ 0.284 ⫻ age (in months), for boys who are 25 months of age or older the linear regression equation is the length of inguinal canal (millimeters) ⫽ 24.176 ⫹ 0.117 ⫻ age (in months). The mean ages for girls and boys have been 45.93 and 40.93 months. If the ages are not taken into consideration, the mean lengths of inguinal canals among girls and boys are 25.517 and 27.612 mm, and the difference is not significant (P ⫽ .522). If mean lengths of inguinal canals are adjusted for age, the mean lengths of inguinal canals among girls and boys are 25.133 and 27.996 mm, and the difference is significant (P ⫽ .018). Although the mean age for the 113 lengths of the right sides have been 39.79 months, and the mean age for the 75 lengths of the left sides have been 42.64 months, the difference between the ages and the lengths of inguinal canals of boys do not significantly differ between right and left sides (P ⫽ .755). Because the age has been a parameter that influences the length of the inguinal canal, the right and left sides have been reevaluated through a covariance analysis after removing the effect of age. The means adjusted according to the ages have been 27.639 and 27.667 mm for right and left sides (P ⫽ .975). Regardless of the age, length of inguinal canal differs significantly between inguinal hernia, hydrocele, and undescended testis groups (F ⫽ 4.65, P ⫽ .0005). However, when age is considered, covariance analysis showed no significant difference between the groups (F ⫽ 0.48, P ⫽ .792).
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The circumference of the sac could successfully classify only 55.3% of boys into 1 of the 3 groups including IH, UT, and H. The success rate has been higher in defining H (86.7%) compared with the success rates encountered in defining IH (54.1%) and UT (33.3%; Table 2). Among the length of inguinal canal, circumference of the sac, the ratio of length of inguinal canal to circumference of the sac, and the ratio of circumference of the sac to the length of inguinal canal, stepwise discriminant analysis has shown that the ratio of length of inguinal canal to circumference of the sac is the only significant parameter in classifying boys into 1 of the 3 groups. Addition of the other parameters did not make any significant contribution to the correct classification of boys. Taking the ratio of length of inguinal canal to circumference of the sac as the only parameter, 70.2% of the boys including 91.8% of IH cases, 50% of H cases and 13.9% of UT cases were classified correctly. However, 6.6% and 1.6% of boys with IH have been placed into UT and H groups, respectively, whereas 52.8% and 33.3% of boys with UT were placed into IH and H groups, respectively, and 13.3% and 36.7% of boys with H were placed into IH and UT groups, respectively (Table 3). DISCUSSION
The length of inguinal canal has been reported to remain short at less than 2 years.6 Our results also confirm that the length of inguinal canal does not show a linear increase during the first 24 months of life. This finding suggests that, the proportion of inguinal canal to the body is higher in infancy. Therefore, its growth is relatively retarded. The proportion that should be maintained seems to be reached at or around 24 months of age. After that age, the inguinal canal lengthens steadily. The linear increase in length is obvious among boys. However, the reported median lengths of 1 and 1.1 cm for inguinal canals in children younger than 2, and 4 years of age or older,6 are not in accord with our findings. We have found the length of inguinal canal to be 27.33 ⫾ 8.08 mm in children at 41.60 ⫾ 39.50 months of age. The length of inguinal canal has been reported to be 4.7 cm among Table 2. Predicted Diagnoses Among Boys if the Circumference of Sacs Is Accepted as the Sole Parameter Predicted Group Membership Hernia
Hernia Undescended testis Hydrocele Percentage Hernia Undescended testis Hydrocele
Undescended Original Count Testis Hydrocele (n ⫽ 188)
66 9 0
43 12 4
13 15 26
122 36 30
54.1 25.0 0
35.2 33.3 13.3
10.7 41.7 86.7
100 100 100
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Table 3. Predicted Diagnoses According to the Ratio of Length of Inguinal Canal to Caliber of Sacs Among Boys Predicted Group Membership Hernia
Hernia Undescended testis Hydrocele Percentage Hernia Undescended testis Hydrocele
Undescended Original Count Testis Hydrocele (n ⫽ 188)
112 19 4
8 5 11
2 12 15
122 36 30
91.8 52.8 13.3
6.6 13.9 36.7
1.6 33.3 50.0
100 100 100
adults. The current results seem to be in accord with those reported by Peri et al.7 The length of inguinal canal does not differ according to the clinical picture or right or left side within the same sex. However, it differs according to the age and sex. The inguinal canals are longer in boys compared with girls at the same age. The development of gubernaculum, that fills the inguinal canal during the fetal period, is known to show a sexual dimorphism. Although its development is similar in both sexes until 41⁄2 months of pregnancy, its further development ceases in girls. In addition to the further growth, the gubernaculum shows a swelling reaction, which is suggested to dilate the inguinal canal before descent of testis.5 Because of those developmental differences related to the descent of testis, the inguinal canal in boys seem to be more developed compared with girls in whom only the round ligament remains. Because the caliber defines the clinical picture in 55.3%, it does not appear to be the most important parameter that determines the clinical outcome. The ratio of length of inguinal canal to circumference of the sac has been the best parameter in classifying boys in 1 of 3 groups including IH, UT, and H. Compared with only caliber, the relation of length of inguinal canal to the caliber appears to play a more determinative role on the clinical outcome. Although this parameter has been the best, it could classify only 70.2% of the boys correctly. The least successful classification has been among boys with UT. Only 13.9% of UT cases were classified correctly. According to the ratios, 52.8% of boys with UT also should have an IH, and 33.3% of boys also should
have a H. However, none of the boys have either had IH or had H. The incidence of IH in association with UT is known to be low. Only 13 IH have been encountered among 150 operations for UT.3 Although the most successful classification has been among boys with IH with a ratio of 91.8%, 50% of boys with H could have been classified correctly. These data show that the caliber is not the unique factor that determines the clinical outcome. Furthermore, neither the caliber nor the ratio of length of inguinal canal to circumference of the sac are the sole determinants of the clinical outcome. Therefore, some factors in addition to caliber of the sac and length of inguinal canal appear to influence the developments of H and IH. A recent study also supports the possible contribution of other factors. In majority of boys with H, the pressure within the H sac exceeds the intraabdominal pressure.8 The excess in pressure cannot be explained by the caliber. The walls of sacs from different inguinal pathologies contain different amounts of smooth muscles.9,10 The persistence of smooth muscle, which possibly plays a role in the descent of the testis during fetal period,11 has been suggested to be responsible for the failed obliteration of the PV. The amount of persisting smooth muscle, which was more in sacs associated with IH, less in sacs associated with H, and least in sacs associated with UT, has been proposed to affect the clinical outcome.8,9,11 The additional factor that influences the clinical outcome to be H or IH may be the amount of persisting smooth muscle. Inguinal canal is longer and shows a linear increase in length in boys after 24 months of age. Its length does not differ according to the clinical picture but differs according to the age. Although the clinical picture is best defined by the ratio of length of inguinal canal to caliber of the sac, especially the sacs associated with UT and H cannot be defined satisfactorily by this parameter. Factors other than the length of inguinal canal and the caliber of the sac, such as the smooth muscle content, may play roles in determining the clinical outcome. ACKNOWLEDGMENT The authors thank Dr Fatih Kızılcan for preparing the figure.
REFERENCES 1. Lloyd DA, Rintala RJ: Inguinal hernia and hydrocele, in O’Neill JA Jr, Rowe MI, Grosfeld JL, et al (eds): Pediatric Surgery. St Louis, MO, Mosby, 1998, pp 1071-1086 2. Elder JS: Cryptorchidism: Isolated and associated with other genitourinary defects. Pediatr Clin North Am 34:1033-1053, 1987 3. Johansen TEB: The anatomy of gubernaculum testis and processus vaginalis in cryptorchidism. Scand J Urol Nephrol 22:101-105, 1988 4. Golka T, Holschneider AM, Fischer R, et al: Pathogenicity of the open processus vaginalis peritonei. Z Kinderchir 44:88-90, 1989
5. Heyns CF, Hutson JM: Historical review of theories on testicular descent. J Urol 153:754-767, 1995 6. Parnis SJ, Roberts JP, Hutson JM: Anatomical landmarks of the inguinal canal in prepubescent children. Aust N Z J Surg 67:335-337, 1997 7. Peri G, Farina F, Marciano V, et al: Clinical and anatomic features of the inguinal canal during hernia. Ital J Anat Embryol 101:69-80, 1996 ¨ cal T, Bu¨yu¨kpamukc¸u N: The pressure within the sac 8. Tanyel FC, O
CANAL LENGTH AND SAC CALIBER
exceeds the intra-abdominal pressure in majority of boys with hydrocele. J Pediatr Surg (submitted) 9. Tanyel FC, Dag˘deviren A, Mu¨ftu¨ug˘lu S, et al: Inguinal hernia revisited through comparative evaluation of peritoneum, obliterated sac, and sacs obtained from children with hernia, hydrocele and undescended testis. J Pediatr Surg 34:552-555, 1999
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10. Tanyel FC, Talim B, Kale G, et al: Processus vaginalis is a sexually dimorphic structure which also contains myofibroblasts. Pathol Res Pract (submitted) 11. Tanyel FC, Sara Y, Ertunc¸ M, et al: The lack of carbachol response indicates the absence of cholinergic receptors in sacs associated with undescended testis. J Pediatr Surg 34:1339-1344, 1999
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 ⫻ age3 (months) ⫺ 0.00292 ⫻ age2 (months) ⫹ 0.3168 ⫻ age (months) ⫹ 19.979 (r2 ⫽ 0.47). Inguinal canal is longer in boys
C
ONGENITAL HYDROCELE (H) and congenital inguinal hernia (IH) are among frequent problems encountered in children. The difference between a H and a IH usually is accepted to be the caliber of the processus vaginalis (PV).1 However, in almost all of the boys with undescended testis (UT), the PV shows a patency of varying calibers.2 Despite the patency of the PV, IH or H does not frequently associate to the clinical picture in boys with UT.3 Furthermore, the presence of a patent PV does not mandate the occurrence of an IH.4 The role of caliber is accused as an axiom, and the relationship of the clinical picture to the caliber never has been evaluated. Inguinal canal is suggested to be one of the structures that differs among boys and girls.5 However, the length of inguinal canal usually has been accepted to remain short in children without considering a sex difference.6 Furthermore, the length of inguinal canal at different ages according to the sexes has not been evaluated thoroughly in the literature. Therefore, a clinical study has been planned to determine the length of inguinal canals at various ages in both sexes and the caliber of sacs in inguinal pathologies to evaluate if the length or caliber or any of their relations Journal of Pediatric Surgery, Vol 35, No 8 (August), 2000: pp 1165-1169
(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. J Pediatr Surg 35:1165-1169. Copyright r 2000 by W.B. Saunders Company. INDEX WORDS: Inguinal canal, inguinal hernia, hydrocele, cryptorchidism.
either differ according to the age, sex, and diagnosis or influence the clinical outcome. MATERIALS AND METHODS Boys and girls operated on for IH and boys operated on for H and UT were evaluated. Patients with only 1 pathology finding were included in the study group, and patients with coexisting pathology findings such as boys with both UT and IH in the same side were excluded. All of the operations were performed by or under the supervision of the same author. The anterior wall of the inguinal canal was opened routinely. The sacs were dissected up to the preperitoneal fat tissue and double ligated. After high ligation, a string was placed into the inguinal canal. One end of the string was located to the suture used for high ligation close to the abdominal cavity. The external inguinal ring was marked on the string, and the length of inguinal canal, which was accepted to be the distance from the tip of the string to the mark, was measured by a ruler (Fig 1A). The sac excised after high ligation was opened longitudinally,
From the Departments of Pediatric Surgery, Anesthesiology, and Biostatistics, Hacettepe University, Faculty of Medicine, Ankara, Turkey. Address reprint requests to F. Cahit Tanyel, MD, Hacettepe University, Faculty of Medicine, Department of Pediatric Surgery, 06100, Ankara, Turkey. Copyright r 2000 by W.B. Saunders Company 0022-3468/00/3508-0004$03.00/0 doi:10.1053/jpsu.2000.8719
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the sac, length of inguinal canal, the ratio of length of inguinal canal to the circumference of the sac, in classifying boys into 1 of 3 diagnostic groups including IH, H, and UT, a stepwise discriminant analysis was performed.
RESULTS
A total of 24 girls and 112 boys with IH, 30 boys with H or hydrocele of the cord, and 31 boys with UT have been evaluated for the current study. A total of 10 boys and 5 girls have presented with bilateral IH, and 5 boys have presented with bilateral UT. Thus, a total of 217 inguinal canals have been evaluated (Table 1). When all of the 217 inguinal canals independent of the sex or the side have been evaluated through the Pearson correlation analysis, a significant correlation has been encountered between the age and the length of the inguinal canal (correlation r ⫽ 0.66, P ⬍ .001). If a linear relation is supposed to exist between the age and the length of the inguinal canal, the regression equation is: the length of inguinal canal (millimeters) ⫽ 21.745 ⫹ 0.136 ⫻ age (in months). The r2 for this model is 0.43. If both girls and boys are evaluated together, the regression model that defines best the relation between the age and the length of inguinal canal, appears to be an equation of third degree (r2 ⫽ 0.47). According to this model, the equation is: the length of inguinal canal (millimeters) ⫽ 0.0000119 ⫻ age3 (in months) ⫺ 0.00292 ⫻ age2 (in months) ⫹ 0.3168 ⫻ age (in months) ⫹ 19.979. Among boys and girls who are at or younger than 24 months of age, the r2 ⫽ 0.309. This suggests that there is no significant relation between the age and the length of inguinal canal until 24 months of age. However, the length of the inguinal canal increases with age after 24 months. The relationship between the age and the length of inguinal canal among boys and girls who are at or older than 25 months of age can be defined by the length of inguinal canal (millimeters) ⫽ 23.954 ⫹ 0.112 ⫻ age (in months). The correlation between age and the length of the canal is significant among girls (r ⫽ 0.611, P ⫽ .000). The
Fig 1. Schematic explanation of the measurements of length of inguinal canal (A) and circumference of the sac (B).
and the circumference of the sac at its closest end to the abdominal cavity was measured by a ruler (Fig 1B). Although the circumference is not constant throughout a sac, the circumference was measured and evaluated at a point at which the caliber plays the role in determining the content and clinical outcome. The lengths of inguinal canals in boys and girls according the ages in months were evaluated independently of the clinical diagnoses. The lengths at similar ages were compared and evaluated. The lengths of inguinal canals of right and left sides were compared to find out if the side influences the length of the inguinal canal. Means, standard deviations, and 95% confidence intervals were found either for the whole group or for subgroups where necessary. Analysis of variance and t test were used for group comparisons. When analysis of variance yielded a significant difference between groups, Least Significant Difference (LSD) test was used to detect the group or groups that differ significantly from the others. Because high correlation was observed between age and other parameters, age has been taken as a covariate, and covariance analysis was performed to test the significance of the difference between the groups, after adjusting the parameter of age. Observed and adjusted group means were displayed in such analysis. Pearson correlation coefficient has been used for assessing the magnitude of the relationships, and regression analysis (linear and non-linear) was performed to study the nature of the relationship between variables and to predict the length of inguinal canal by using the age as the predictor variable. Model fit was tested by using analysis of variance, and r2 were supplied to show the success of the model in explaining the change in the dependent variable. To find out the values of parameters, which include circumference of
Table 1. The Minimum and Maximum Values and the Distribution of Parameters According to Diagnoses Among Sexes Age (mo) Groups
No.
Female hernia (Right) 18 Female hernia (Left) 11 Male hernia (Right) 75 Male hernia (Left) 47 Hydrocele (Right) 19 Hydrocele (Left) 11 Undescended testis (Right) 19 Undescended testis (Left) 17 Total 217
Mean ⫾ SD
Length of Canal (mm)
Minimum Maximum
Mean ⫾ SD
Circumference of Sac mm)
Minimum Maximum
Mean ⫾ SD
Length/ Minimum Maximum Circumference
52.33 ⫾ 41.77 35.45 ⫾ 33.65 28.98 ⫾ 32.75 28.93 ⫾ 35.89 52.16 ⫾ 27.20 60.91 ⫾ 47.54
2 2 1 2 13 4
144 108 132 144 108 132
25.72 ⫾ 6.39 25.18 ⫾ 9.34 25.50 ⫾ 7.06 25.83 ⫾ 8.75 30.95 ⫾ 6.16 30.73 ⫾ 9.26
15 14 10 11 20 17
37 43 40 43 42 51
29.94 ⫾ 09.76 30.55 ⫾ 11.03 30.16 ⫾ 13.37 33.00 ⫾ 14.84 10.53 ⫾ 04.86 10.55 ⫾ 05.87
12 18 9 3 3 4
50 50 80 70 20 22
0.97 ⫾ 0.47 0.88 ⫾ 0.34 1.00 ⫾ 0.49 1.04 ⫾ 0.98 3.86 ⫾ 2.47 3.86 ⫾ 2.30
70.10 ⫾ 45.87
24
168
31.89 ⫾ 8.32
21
52
23.37 ⫾ 19.58
5
84
2.50 ⫾ 1.82
68.71 ⫾ 41.39 41.60 ⫾ 39.50
18 1
156 168
31.81 ⫾ 8.08 27.33 ⫾ 8.09
22 10
52 52
21.00 ⫾ 15.64 26.75 ⫾ 15.14
5 3
60 84
2.42 ⫾ 1.46 1.63 ⫾ 1.60
CANAL LENGTH AND SAC CALIBER
linear regression equation, which is found to be highly significant for the length of inguinal canal among girls is (in millimeters) ⫽ 20.149 ⫹ 0.117 ⫻ age (in months). If the girls are divided into 2 groups, those 24 months of age or younger and those 25 months or older, the correlation between the age and length of inguinal canal decreases and lacks the significance in both of the groups (for those 24 months or older, r ⫽ 0.156, P ⫽ .628, and for those older, r ⫽ 0.408, P ⫽ .104). If the length of inguinal canals only among boys are evaluated (n ⫽ 188), the correlation between the age and the length of inguinal canal becomes more obvious (correlation r ⫽ 0.677). If a linear regression is supposed to exist between the age and the length of inguinal canal, the regression equation is: the length of inguinal canal (millimeters) ⫽ 21.959 ⫹ 0.14 ⫻ age (in months). Observed points fit very well to this model (r2 ⫽ 0.458, P ⬍ .001). The relationship between the age and the length of inguinal canal among boys who are 24 months or younger (r ⫽ 0.327, P ⫽ .002) is less significant than that of boys who are equal or older than 25 months of age (r ⫽ 0.595, P ⫽ .000). Although the linear regression equation for boys who are equal or younger than 24 months of age is the length of inguinal canal (millimeters) ⫽ 20.24 ⫹ 0.284 ⫻ age (in months), for boys who are 25 months of age or older the linear regression equation is the length of inguinal canal (millimeters) ⫽ 24.176 ⫹ 0.117 ⫻ age (in months). The mean ages for girls and boys have been 45.93 and 40.93 months. If the ages are not taken into consideration, the mean lengths of inguinal canals among girls and boys are 25.517 and 27.612 mm, and the difference is not significant (P ⫽ .522). If mean lengths of inguinal canals are adjusted for age, the mean lengths of inguinal canals among girls and boys are 25.133 and 27.996 mm, and the difference is significant (P ⫽ .018). Although the mean age for the 113 lengths of the right sides have been 39.79 months, and the mean age for the 75 lengths of the left sides have been 42.64 months, the difference between the ages and the lengths of inguinal canals of boys do not significantly differ between right and left sides (P ⫽ .755). Because the age has been a parameter that influences the length of the inguinal canal, the right and left sides have been reevaluated through a covariance analysis after removing the effect of age. The means adjusted according to the ages have been 27.639 and 27.667 mm for right and left sides (P ⫽ .975). Regardless of the age, length of inguinal canal differs significantly between inguinal hernia, hydrocele, and undescended testis groups (F ⫽ 4.65, P ⫽ .0005). However, when age is considered, covariance analysis showed no significant difference between the groups (F ⫽ 0.48, P ⫽ .792).
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The circumference of the sac could successfully classify only 55.3% of boys into 1 of the 3 groups including IH, UT, and H. The success rate has been higher in defining H (86.7%) compared with the success rates encountered in defining IH (54.1%) and UT (33.3%; Table 2). Among the length of inguinal canal, circumference of the sac, the ratio of length of inguinal canal to circumference of the sac, and the ratio of circumference of the sac to the length of inguinal canal, stepwise discriminant analysis has shown that the ratio of length of inguinal canal to circumference of the sac is the only significant parameter in classifying boys into 1 of the 3 groups. Addition of the other parameters did not make any significant contribution to the correct classification of boys. Taking the ratio of length of inguinal canal to circumference of the sac as the only parameter, 70.2% of the boys including 91.8% of IH cases, 50% of H cases and 13.9% of UT cases were classified correctly. However, 6.6% and 1.6% of boys with IH have been placed into UT and H groups, respectively, whereas 52.8% and 33.3% of boys with UT were placed into IH and H groups, respectively, and 13.3% and 36.7% of boys with H were placed into IH and UT groups, respectively (Table 3). DISCUSSION
The length of inguinal canal has been reported to remain short at less than 2 years.6 Our results also confirm that the length of inguinal canal does not show a linear increase during the first 24 months of life. This finding suggests that, the proportion of inguinal canal to the body is higher in infancy. Therefore, its growth is relatively retarded. The proportion that should be maintained seems to be reached at or around 24 months of age. After that age, the inguinal canal lengthens steadily. The linear increase in length is obvious among boys. However, the reported median lengths of 1 and 1.1 cm for inguinal canals in children younger than 2, and 4 years of age or older,6 are not in accord with our findings. We have found the length of inguinal canal to be 27.33 ⫾ 8.08 mm in children at 41.60 ⫾ 39.50 months of age. The length of inguinal canal has been reported to be 4.7 cm among Table 2. Predicted Diagnoses Among Boys if the Circumference of Sacs Is Accepted as the Sole Parameter Predicted Group Membership Hernia
Hernia Undescended testis Hydrocele Percentage Hernia Undescended testis Hydrocele
Undescended Original Count Testis Hydrocele (n ⫽ 188)
66 9 0
43 12 4
13 15 26
122 36 30
54.1 25.0 0
35.2 33.3 13.3
10.7 41.7 86.7
100 100 100
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TANYEL ET AL
Table 3. Predicted Diagnoses According to the Ratio of Length of Inguinal Canal to Caliber of Sacs Among Boys Predicted Group Membership Hernia
Hernia Undescended testis Hydrocele Percentage Hernia Undescended testis Hydrocele
Undescended Original Count Testis Hydrocele (n ⫽ 188)
112 19 4
8 5 11
2 12 15
122 36 30
91.8 52.8 13.3
6.6 13.9 36.7
1.6 33.3 50.0
100 100 100
adults. The current results seem to be in accord with those reported by Peri et al.7 The length of inguinal canal does not differ according to the clinical picture or right or left side within the same sex. However, it differs according to the age and sex. The inguinal canals are longer in boys compared with girls at the same age. The development of gubernaculum, that fills the inguinal canal during the fetal period, is known to show a sexual dimorphism. Although its development is similar in both sexes until 41⁄2 months of pregnancy, its further development ceases in girls. In addition to the further growth, the gubernaculum shows a swelling reaction, which is suggested to dilate the inguinal canal before descent of testis.5 Because of those developmental differences related to the descent of testis, the inguinal canal in boys seem to be more developed compared with girls in whom only the round ligament remains. Because the caliber defines the clinical picture in 55.3%, it does not appear to be the most important parameter that determines the clinical outcome. The ratio of length of inguinal canal to circumference of the sac has been the best parameter in classifying boys in 1 of 3 groups including IH, UT, and H. Compared with only caliber, the relation of length of inguinal canal to the caliber appears to play a more determinative role on the clinical outcome. Although this parameter has been the best, it could classify only 70.2% of the boys correctly. The least successful classification has been among boys with UT. Only 13.9% of UT cases were classified correctly. According to the ratios, 52.8% of boys with UT also should have an IH, and 33.3% of boys also should
have a H. However, none of the boys have either had IH or had H. The incidence of IH in association with UT is known to be low. Only 13 IH have been encountered among 150 operations for UT.3 Although the most successful classification has been among boys with IH with a ratio of 91.8%, 50% of boys with H could have been classified correctly. These data show that the caliber is not the unique factor that determines the clinical outcome. Furthermore, neither the caliber nor the ratio of length of inguinal canal to circumference of the sac are the sole determinants of the clinical outcome. Therefore, some factors in addition to caliber of the sac and length of inguinal canal appear to influence the developments of H and IH. A recent study also supports the possible contribution of other factors. In majority of boys with H, the pressure within the H sac exceeds the intraabdominal pressure.8 The excess in pressure cannot be explained by the caliber. The walls of sacs from different inguinal pathologies contain different amounts of smooth muscles.9,10 The persistence of smooth muscle, which possibly plays a role in the descent of the testis during fetal period,11 has been suggested to be responsible for the failed obliteration of the PV. The amount of persisting smooth muscle, which was more in sacs associated with IH, less in sacs associated with H, and least in sacs associated with UT, has been proposed to affect the clinical outcome.8,9,11 The additional factor that influences the clinical outcome to be H or IH may be the amount of persisting smooth muscle. Inguinal canal is longer and shows a linear increase in length in boys after 24 months of age. Its length does not differ according to the clinical picture but differs according to the age. Although the clinical picture is best defined by the ratio of length of inguinal canal to caliber of the sac, especially the sacs associated with UT and H cannot be defined satisfactorily by this parameter. Factors other than the length of inguinal canal and the caliber of the sac, such as the smooth muscle content, may play roles in determining the clinical outcome. ACKNOWLEDGMENT The authors thank Dr Fatih Kızılcan for preparing the figure.
REFERENCES 1. Lloyd DA, Rintala RJ: Inguinal hernia and hydrocele, in O’Neill JA Jr, Rowe MI, Grosfeld JL, et al (eds): Pediatric Surgery. St Louis, MO, Mosby, 1998, pp 1071-1086 2. Elder JS: Cryptorchidism: Isolated and associated with other genitourinary defects. Pediatr Clin North Am 34:1033-1053, 1987 3. Johansen TEB: The anatomy of gubernaculum testis and processus vaginalis in cryptorchidism. Scand J Urol Nephrol 22:101-105, 1988 4. Golka T, Holschneider AM, Fischer R, et al: Pathogenicity of the open processus vaginalis peritonei. Z Kinderchir 44:88-90, 1989
5. Heyns CF, Hutson JM: Historical review of theories on testicular descent. J Urol 153:754-767, 1995 6. Parnis SJ, Roberts JP, Hutson JM: Anatomical landmarks of the inguinal canal in prepubescent children. Aust N Z J Surg 67:335-337, 1997 7. Peri G, Farina F, Marciano V, et al: Clinical and anatomic features of the inguinal canal during hernia. Ital J Anat Embryol 101:69-80, 1996 ¨ cal T, Bu¨yu¨kpamukc¸u N: The pressure within the sac 8. Tanyel FC, O
CANAL LENGTH AND SAC CALIBER
exceeds the intra-abdominal pressure in majority of boys with hydrocele. J Pediatr Surg (submitted) 9. Tanyel FC, Dag˘deviren A, Mu¨ftu¨ug˘lu S, et al: Inguinal hernia revisited through comparative evaluation of peritoneum, obliterated sac, and sacs obtained from children with hernia, hydrocele and undescended testis. J Pediatr Surg 34:552-555, 1999
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10. Tanyel FC, Talim B, Kale G, et al: Processus vaginalis is a sexually dimorphic structure which also contains myofibroblasts. Pathol Res Pract (submitted) 11. Tanyel FC, Sara Y, Ertunc¸ M, et al: The lack of carbachol response indicates the absence of cholinergic receptors in sacs associated with undescended testis. J Pediatr Surg 34:1339-1344, 1999