Embryology · Urogenital system
Cryptorchidism !
- Malformation
One or both testes did not come down into the scrotum before birth. It is the commonest genital malformation in boys.
Updated 2026-11-01
See it in 3D: Scrotum · Inguinal canal · Spermatic cord · Testicular arteries
What it is
Cryptorchidism is a testis that stopped somewhere along its normal path from the abdomen to the scrotum. It affects about 3% of full-term boys and many more preterm boys, and some testes come down on their own in the first months. It matters because a testis outside the scrotum is linked to lower fertility and a higher risk of testicular cancer.
Embryological cause
- Failure of the transabdominal phase (weeks 8–15): a defect of INSL3, its receptor or the gubernaculum; the testis stays intra-abdominal.
- Failure of the inguinoscrotal phase (third trimester): androgen deficiency or impaired action; the testis stays in the inguinal canal.
- Prematurity: birth interrupts a descent that mostly happens in the third trimester.
- Ectopic testis: it leaves the normal route (perineal, femoral, at the base of the penis).
Markers
- INSL3
- RXFP2
- AR
How it presents
- An empty or small hemiscrotum, with the testis palpable in the groin or not palpable.
- Often accompanied by an indirect inguinal hernia through a patent processus vaginalis.
- Associated with hypospadias, especially proximal forms.
- Long term: lower sperm production and higher risk of seminoma, which persists even after the testis is brought down.
Diagnosis
- Diagnosis rests on repeated physical examination, with the child relaxed and squatting or cross-legged.
- Ultrasound does not replace the examination and rarely changes management.
- Bilateral impalpable testes, or with hypospadias: karyotype and hormonal profile.
- Laparoscopy locates an intra-abdominal testis or confirms its absence.
Test yourself
Think of the answer, then tap the question to see it.
Where is an undescended testis most often found?
In the inguinal canal, along the normal route of descent.
Which hormone and which phase of descent fail in an intra-abdominal testis?
The transabdominal phase, which depends on INSL3 from Leydig cells acting on the gubernaculum.
How is a retractile testis told apart from cryptorchidism?
A retractile testis can be brought into the scrotum and stays there when released; it retracts through the cremasteric reflex and is not a malformation.
Why do two impalpable testes in a newborn call for a karyotype?
Because the baby may be a 46,XX girl with congenital adrenal hyperplasia and virilized genitalia, who is also at risk of a salt-wasting crisis.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Gonads and the descent of the testis
- Processus vaginalis: hydrocele and indirect inguinal hernia
- Hypospadias and epispadias
- Differences of sex development: CAH, AIS and 5α-reductase
- Sex determination: SRY, anti-Müllerian hormone and testosterone
Related conditions
Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.
Sources: Undescended testicle: MedlinePlus Medical Encyclopedia (MedlinePlus, U.S. National Library of Medicine, 2024); Embryology, Testicle - StatPearls - NCBI Bookshelf (StatPearls Publishing (NCBI Bookshelf), 2023).
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Representative model, for educational purposes only.