The position of the testis during the fetal period: an additional parameter to estimate fetal weight

Inguinoscrotal stage of testicular descent: analysis in 217 human fetuses

BACKGROUND

Testicular descent is a complex process of relevant importance for the comprehension of cryptorchidism. Studies about the inguinoscrotal stage of testicular migration correlating the testicular position with fetal parameters are rare in the literature. Our hypothesis is that the transition of the testis by the inguinal canal is a very fast process and occurs at the end of the third gestational trimester.

AIM

To analyze the inguinoscrotal stage of testicular descent during the human fetal period.

STUDY DESIGN

This is an observational study in human fetuses. We studied 217 human male fetuses ranging from 10 to 35 weeks postconception (WPC). The fetuses were well preserved and evaluated regarding crown-rump length (CRL) and body weight before dissection. Testicular position was classified as: a) abdominal, when the testis was proximal to the internal ring; b) inguinal, when it was found between the internal and external inguinal rings; and c) scrotal, when being inside the scrotum. Means were statistically compared using the unpaired t-test (P < 0.05).

RESULTS

Of the 434 testes, 329 (75.8%) were abdominal, 48 (11.05%) were inguinal, and 57 (13.13%) were scrotal. The first case of inguinal testis was observed in a fetus with 17 WPC, 203 g, and 15 cm CRL. The 48 inguinal testes were observed in 29 fetuses (13.36%), aged between 17 and 29 WPC, weighing between 203 and 1220 g, and with CRL between 15 and 27.5 cm. Of the 29 fetuses with inguinal testes, 23 (79.32%) were aged between 20 and 26 WPC; 3 (10.34%) had 17 WPC; and 3 (10.34%) had more than 26 WPC. All the fetuses with more than 30 WPC had testes in the scrotum. We did not observe fetuses less than 17 WPC with the testes in the canal.

DISCUSSION

We found that all fetuses with more than 30 WPC had the testes located in the scrotum and that in fetuses between 17 WPC and 25 WPC, 38 testes (8.7% of the sample) were situated in the canal and only 1 testis in a fetus with 25 WPC was located in the scrotum, showing that the second stage of testicular migration through the inguinal canal rarely occurs before the 20th WPC.

CONCLUSION

The inguinoscrotal stage of testicular descent is a fast process, observed only in 13% of the fetuses and occurring with more intensity between 20 and 26 WPC.

Is there a trans-abdominal testicular descent during the second gestational trimester? Study in human fetuses between 13 and 23 weeks post conception

OBJECTIVES

To confirm if a real inner descend of testis occurs, correlating the testicular position with fetal parameters and analyzing the position of the testes relative to the internal ring.

MATERIAL AND METHODS

Twenty nine human fetuses between 13 and 23 weeks post conception (WPC) were studied. The fetuses were carefully dissected with the aid of a stereoscopic lens with 16/25X magnification and testicular position observed. With the aid of a digital pachymeter the distance between the lower pole of the kidney and the upper extremity of the testis (DK-T) was measured to show the position of the testis. During the dissection we also indicated the position of the testes relative to the internal ring. Means were statistically compared using simple linear regression and the paired T-test.

RESULTS

The 58 testes had abdominal position. The DK-T in the right side measured between 0.17 and 1.82cm (mean=0.79cm) and in the left side it was between 0.12 and 1.84cm (mean=0.87cm), without statistically differences (p=0.0557). The linear regression analysis indicated that DK-T in both sides correlated significantly and positively with fetal age. All fetuses with more than 20 WPC, heavier than 350g and with CRL over 22cm had a greater distance than the average DK-T. We xobserved that the 58 testis remains adjacent to the internal ring throughout the period studied.

CONCLUSIONS

The testes remains adjacent to the internal ring throughout the period studied, indicating that there is no real trans-abdominal testicular descent during the second gestational trimester.