Cryptorchidism (1/3) – 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 (undescended testis):
An abdominal testis is also called "true cryptorchidism" (greek: hidden testis), the testis is located proximal to the deep inguinal ring.
The undescended testis is palpable between the internal and external inguinal ring, it 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).
The ectopic testis has a position outside the "path of descent", e.g. inguinal above the facia, perineal, femoral or opposite scrotum.
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 as cryptorchidism.
Epidemiology of Cryptorchidism
- 1% of one-year old boys
- 3% of the boys at birth (normal pregnancy)
- 9–30% in premature infants
Risk factors for cryptorchidism:
- Premature births
- Low birth weight (7% cryptorchidism in children with a birth weight <2000 g)
- Breech presentation
- Other factors: preeclampsia, positive family history
Frequency of Monorchism:
Monorchism (lack of one testis) is the underlying cause for 5–20% of patients with real (non-palpable) cryptorchidism. Most often, the cause for a missing testicle is the vanishing testis syndrome (intrauterine testicular torsion).
Etiology (Causes) of Cryptorchidism
The complex mechanisms of testicular descent is susceptible to interference (Hutson and Hasthorpe, 2005):
Mechanisms of Testicular Descent
It is suspected that the abdominal part of the testicular descent is controlled by the antimüllerian hormone and insulin-like hormone 3 (Insl3). The inguinal and scrotal part of the testicular descent is controlled by androgens.
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. A swelling reaction is caused by above mentioned hormones and prevents elongation of the gubernaculum, while the embryo enlarges. In addition, the cranial suspensory ligament of the gonade regresses in male fetuses. This leads to the descent of the male gonade close to the internal inguinal ring.
The inguinal and scrotal part of the testicular descent is controlled by androgens, which need the genitofemoral nerve and his release of Calitonin Gene-Related Peptid (CGRP) for complete 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, mutations of the androgen receptor and many more. Hormone treatment with HCG or GnRH leads to higher testosterone concentrations and is a treatment option in cryptorchidism (see below).
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.
Prenatal treatment of the mother with DES (diethylstilbestrol) leads to cryptorchidism.
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
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:
The increased testicular temperature in cryptorchidism results in a 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 the histopathological changes.
Malformations of the epididymis:
An open processus vaginalis is a strong 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 probable caused by the same mechanisms as the cryptorchidism. Epididymal anomalies are the most commen reasons for infertility after "successful surgical therapy".
Germ Cell Tumors:
The exact mechanims for the increased risk for testicular cancer (10–20×) is unclear. Testicular dysgenesis is the probable cause, since the contralateral orthotopic testis has the same increased risk of malignancy. The higher the position of the testis, the higher the risk of malignancy. Germ cell tumors develop usually after puberty. A testicular biopsy at the time of orchidopexy cannot judge the risk of tumors.
Orchidopexy and testicular cancer risk:
Orchidopexy before the 10th year of age reduces the incidence of germ cell tumors and enables clinical controls for early detection of testicular tumor. An early orchidopexy enhances the protective effect. Some studies could not demonstrate the protective effect by early orchidopexy.
Testicular Pathology in Cryptorchidism
Typical histopathological signs of testicular damage in untreated cryptorchidism:
- Decreased number of Leydig cells (early signs)
- Degeneration of Sertoli cells
- Persistence of fetal gonocytes and missing development of the adult dark spermatogonia
- Missing development of primary spermatocytes
- Peritubular fibrosis
- Within two years after birth, the complete histopathological picture can be expected.
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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