Dr. med. Dirk Manski

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Cryptorchidism – Undescended Testicle

Definitions of Cryptorchidism

Cryptorchidism is the absence of one testis or both testes from the scrotum, caused by a deficient or irregular testicular descent EAU Guidelines Paediatric Urology, AUA cryptorchidism guideline.

Abdominal testis:

An abdominal testis is also called "true cryptorchidism" (Greek: hidden testis); the testis is located proximal to the deep inguinal ring.

Inguinal testis:

The undescended testis is palpable between the internal and external inguinal ring and cannot be displaced into the scrotum (in contrast to the retractile testis). Some inguinal testes may be displaced to the scrotum, but immediately after examination, they slide back into the inguinal position. In contrast to retractile testes, inguinal testes do not descend to a scrotal position with muscular relaxation (e.g., warm bath).

Ectopic testes:

The ectopic testis is outside the path of normal descent, e.g., inguinal above the facia, perineal, femoral, or pubic localization.

Retractile testis:

A retractile testis has an inguinal position due to the contraction of the cremaster muscle. With muscular relaxation (e.g., warm bath), the retractile testis descends to a scrotal position. Retractile testes should not be considered cryptorchidism.

Epidemiology of Cryptorchidism


Risk factors for cryptorchidism:

Familiar disease:

The concordance rate is 7% for brothers, 17% for dizygotic twins, and 27% for monozygotic twins.

Frequency of Monorchism:

Monorchidism (lack of one testis) is the underlying cause for 5–20% of patients with real (nonpalpable) cryptorchidism. Most often, the cause for a missing testicle is the vanishing testis syndrome (intrauterine testicular torsion). The absent testis causes compensatory hypertrophy of the contralateral testis. Thus, a testicular volume greater than 2 ml indicates monorchy in children with nonpalpable cryptorchidism (Hodhod et al., 2016).

Etiology (Causes) of Cryptorchidism

The complex mechanisms of testicular descent are susceptible to interference (Hutson and Hasthorpe, 2005):

Mechanisms of Testicular Descent

The testicular descent is controlled by the antimüllerian hormone, insulin-like hormone 3 (Insl3), and by androgens (DHT and testosterone). The gubernaculum testis, also called genitoinguinal ligament, connects the testis to the inguinal region and is the key structure for the abdominal part of the descent. The hormones mentioned above cause a swelling reaction of the gubernaculum and enlarge the inguinal canal. The testis migrates caudally due to the growth in length of the embryo. As the descent progresses, muscle cells migrate into the gubernaculum. Regression of the gubernaculum and muscle contraction (innervation by the genitofemoral nerve) trigger the inguinal part of the testicular descent.

Lack of Androgens:

An absolute (low concentration) or relative (reduced sensitivity of the target tissue) androgen deficiency leads to cryptorchidism, although the abdominal part of the testicular descent is not impaired. Many reasons for androgen deficiency are known, e.g., 5α-reductase deficiency or mutations of the androgen receptor. Hormone treatment with HCG or GnRH leads to higher testosterone concentrations and has been a treatment option in cryptorchidism (see below).

Genetic syndromes:

Many genetic syndromes are associated with cryptorchidism: e.g., Noonan syndrome, WAGR syndrome, Kallmann syndrome, prune-belly syndrome, exstrophy of the bladder, omphalocele or gastroschisis. Gene candidates for heritable nonsyndromatic cryptorchidism are mostly unknown and the genetic etiology is multifactorial.


Prenatal treatment of the mother with DES (diethylstilbestrol) leads to cryptorchidism.

Environmental Factors:

The increasing incidence in industrialized countries argues for environmental toxins, which increase the risk for hypospadias and other diseases (infertility, cryptorchidism, premature births, testicular cancer). Numerous substances (endocrine disruptors) in plastics and pesticides are discussed as causal substances (Rodprasert et al., 2021).

Decreased abdominal pressure:

Decreased abdominal pressure may be a factor for impaired testicular descent in Prune-belly syndrome, exstrophy, omphalocele, or gastroschisis.

Pathophysiology of Cryptorchidism

Male Infertility:

Cryptorchidism is a risk factor for male infertility: 87% of untreated men with unilateral cryptorchidism have children, but only 33% of men with bilateral cryptorchidism.

Impaired germ cell development:

Cryptorchidism results in testicular damage with impaired germ cell development: persistence of fetal gonocytes and the lack of development of the adult dark spermatogonia (see pathology). Early orchidopexy can prevent histopathological changes.

Malformations of the epididymis:

An open processus vaginalis is a risk factor for epididymal anomalies. The higher the position of the testis in cryptorchidism, the more likely the epididymal malformations, such as disturbed fusion of epididymis and testis or even missing epididymal structures. The epididymal malformations are probably caused by similar mechanisms as cryptorchidism. Epididymal anomalies are the most common reasons for infertility after "successful surgical therapy".

Germ Cell Tumors:

The reasons for the increased testicular cancer risk (10–20× if untreated) are unclear. Testicular dysgenesis is a probable cause. The higher the testis position, the higher the risk of malignancy. Germ cell tumors usually develop after puberty. A testicular biopsy at the time of orchidopexy cannot judge the risk of tumors. The contralateral orthotopic testis is also at risk, but to a lesser extent.

Testicular Pathology in Cryptorchidism

Typical histopathological signs of testicular damage in untreated cryptorchidism:

Signs and Symptoms of Cryptorchidism

Diagnostic Workup in Cryptorchidism


Palpation (search for a missing testis) should be done either in a relaxed supine position, while sitting (infants), or while standing (children). 80% of undescended testes are palpable. For nonpalpable testes, 20% are missing, 30% are atrophic inguinal testes, and 50% are abdominal testes.


Testicular ultrasound imaging with a high-resolution linear array transducer is suitable for the location of the undescended testis in the inguinal canal. Anesthesia is necessary for an abdominal MRI in infants, which is only required for particular questions (concomitant malformations?).

Laboratory tests:

Laboratory tests are particularly indicated for bilateral nonpalpable testes.


An elevated FSH before puberty is a sign of bilateral missing testes.

HCG stimulation test:

An HCG stimulation test is indicated for bilateral nonpalpable testes: serum testosterone is measured before and 32 h after administration of 5000 IU HCG. An increase in testosterone proves the existence of dystopic testicle(s).


Inhibin is a testicular peptide hormone that can predict testicular damage. It is not yet in the clinical routine.

Genetic diagnosis and counseling:

If cryptorchidism is associated with other malformations or developmental anomalies, genetic diagnosis and counseling should be offered if appropriate after a detailed family history.

Diagnostic laparoscopy:

Diagnostic laparoscopy is indicated if abdominal testes are suspected (see section cryptorchidism treatment).

Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


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T. F. Kolon, A. Herndon, L. A. Baker, L. S. Baskin, and C. G. Baxter, “AUA Guideline: Evaluation and Treatment of Cryptorchidism,” 2018. [Online]. Available: https://www.auanet.org/guidelines-and-quality/guidelines/cryptorchidism-guideline.

Kolon u.a. 2004 KOLON, T. F. ; PATEL, R. P. ; HUFF, D. S.: Cryptorchidism: diagnosis, treatment, and long-term prognosis.
In: Urol Clin North Am
31 (2004), Nr. 3, S. 469–80, viii-ix

C. Radmayr, G. Bogaert, H. S. Dogan, and Tekg&uuml, “EAU Guidelines: Paediatric Urology,” 2022. [Online]. Available: https://uroweb.org/guidelines/paediatric-urology/.

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W. Rodprasert, J. Toppari, and H. E. Virtanen, “Endocrine Disrupting Chemicals and Reproductive Health in Boys and Men.,” Front Endocrinol., vol. 12, p. 706532, 2021.

A. V. Thorsson, P. Christiansen, und M. Ritzen. Efficacy and safety of hormonal treatment of cryptorchidism: current state of the art.
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