隐睾

Cryptorchidism

Introduction:The most common genital problem encountered in pediatrics is Cryptorchidism. Literal meaning of Cryptorchidism is hidden or obscure testis and generally refers to an undescended or maldescended testis. Untreated cryptorchidism clearly has deleterious effects on the testis over time. Understanding the abnormalities of morphogenesis and the molecular and hormonal milieu associated with cryptorchidism is critical to contemporary diagnosis and treatment of this extremely common entity
Problem
Normal testicular development begins at conception. The testis-determining factor is now identified as the SRY gene (sex-determining region on Y chromosome). The presence of this gene and an intact downstream pathway generally result in testicular formation. At 3-5 weeks' gestation, the gonadal ridge or indifferent gonad develops, and, at 6 weeks' gestation, primordial germ cell migration occurs. Soon after, Sertoli cells develop and secrete müllerian-inhibiting substance (MIS), the level of which remains high throughout gestation and causes regression of müllerian ducts. At 9 weeks' gestation, Leydig cells develop and secrete testosterone. Other than trans-abdominal movement to the internal inguinal ring, prenatal ultrasonography shows no testicular descent before 28 weeks' gestation. Trans-inguinal migration, thought to be under hormonal control, occurs at 28-40 weeks' gestation, usually resulting in a scrotal testis by the end of a full term of gestation.
Frequency
Factors that Predispose to cryptorchidism include prematurity, low birth weight, small size for gestational age, twinning, and maternal exposure to estrogen during the first trimester. Seven percent of siblings of boys with undescended testes have cryptorchidism. Spontaneous descent after the first year of life is uncommon.
Etiology
The etiology of cryptorchidism is multi-factorial. Birth weight is the principal determining factor for undescended testes at birth to age one year, independent of the length of gestation. Until 23 weeks’ gestation, Transabdominal descent of the testis involves differential growth of vertebrae and pelvis. Afterward, further descent is facilitated by the development of the gubernaculum, processus vaginalis, spermatic vessels, and scrotum. A normal hypothalamic-pituitary-gonadal axis is a prerequisite for testicular descent. Moreover, testosterone and its conversion to dihydrotestosterone (DHT) are also necessary for continued migration, especially during the inguinoscrotal phase.

In patients with cryptorchidism, the gubernaculum is not firmly attached to the scrotum, and the testis is not pulled into the scrotum. Both hormonal and mechanical factors appear to mediate the aid of the gubernaculum and descent of the testis. The genitofemoral nerve may also aid in descent and gubernacular differentiation, which may be mediated by calcitonin gene-related peptide.

Intra-abdominal pressure also appears to play a role in testicular descent. Conditions associated with decreased pressure include prune belly syndrome, cloacal exstrophy, omphalocele, and gastroschisis, among other various syndromes. With an increased risk of undescended testes each one is associated. The effect of decreased intra-abdominal pressure is most significant during trans-inguinal migration to the scrotum, probably in conjunction with androgens and a patent processus vaginalis.
Presentation
In cryptorchidism, the most useful determination is whether the testes are palpable upon physical examination. Although this is seemingly self-explanatory, it is occasionally difficult to accurately determine the exact location of the testis. Body habitus, testicular position, and compliance of the child all are factors during the physical examination. Nonpalpable testes may be intra-abdominal or absent. Palpable testes may be undescended, ectopic, or retractile.
Within a few centimeters of the internal ring most intra-abdominal testes are found. Absent or vanishing testes are thought to be due to an intrauterine or perinatal vascular event, most likely during late gestation since most of these testicular nubbins are found below the internal inguinal ring.
Ectopic testes exit the external inguinal ring and are then misdirected along the normal course of the testis. Retractile testes may be palpated anywhere along the natural course of the testis, although most are inguinal. Although not truly undescended, these testes may be supra-scrotal secondary to an active cremasteric reflex. This reflex is most active in boys aged 5 years and usually weak in infants. These testes can be manipulated into the scrotum, where they remain without tension. This condition is considered a variant of normal; however, the risk of ascent may approach fifty percent. Ascent probably represents an undescended testis that was almost in normal position.
Associated anomalies and conditions may include the following:

• Cerebral palsy
• Mental retardation
• Patent processus vaginalis
• Abnormal epididymis
• Wilms tumor
• Abdominal wall defects (e.g., gastroschisis, omphalocele, prune belly syndrome)
• Hypospadias
  

In general, ductal abnormalities, hernias (patent processus vaginalis), and testicular mal-development are more common in patients with abdominal testes.
Medical history

• Was the patient born premature?
• What was the patient's birth weight?
• Has the testis ever been palpable in scrotum?
• Has the patient undergone prior inguinal surgery?
• Is or was the patient's mother on a vegetarian diet? Was the patient fed soy formula during infancy?
• Determine the prenatal history, including whether the patient's parents used an assisted reproductive technique, whether his mother received hormonal treatment, and whether there were multiple gestations.
• Does the patient have a family history of cryptorchidism, hypospadias, intersexuality, precocious puberty, infertility, or consanguinity?
  

Physical examination

• The patient should be warm and relaxed for the examination.
• Observation should precede the examination.
• The patient should be placed in the frog-leg position for examination. This is especially useful in obese children with fatty infiltration of the scrotum and when retractility is a concern.
• Milk down, palpating from iliac crest to scrotum (soap or lubrication on fingertips may help).
• What are the features of the scrotum and its contents (e.g., hypoplasticity, bifidity, rugae, transposition and pigmentation)?
• Is the contra-lateral testicle hypertrophic?
• Is the undescended testis located in an unusual position, such as in an ectopic site (i.e., superficial inguinal pouch or transverse scrotal, femoral, prepenile, perineal, or contralateral hemiscrotum)?
• Note the presence of any hypospadias or chordee. Does the patient have a normal stretched penile length?
• If the findings are equivocal, perform serial examinations.
  

Indications
Indications for hormonal or surgical correction of cryptorchidism include the following:

• Increase the likelihood of fertility
  
  • Abnormal germ cell maturation correlates with abnormal spermiogram findings in adulthood.
  • A well-recognized consequence of cryptorchidism is impairment of germ cell maturation.
  • To reduce the risk of infertility early reposition of the testis into the scrotum has been a mainstay of treatment.
    
• Facilitation of testicular self-examination for testicular cancer
  
  • The location of the undescended testis affects the relative risk of testicular cancer.
  • Clearly, the ability for patients to perform testicular self-examination with the testes in the scrotum is a benefit of surgery.
  • Males with undescended testis are forty times as likely to develop testicular cancer as males without undescended testis. Ten percent of testicular cancer cases involve patients with undescended testis.
  • The most common malignant tumor type associated with cryptorchidism is Seminoma.
    
• Psychological effects of an empty scrotum
• Prevention of testicular torsion
• Prevention of injury against pubic bone
  

Relevant Anatomy
The testis, when palpable, is usually found in the superficial inguinal pouch or in the inguinal canal under the external oblique aponeurosis. Care must be taken during dissection to avoid the ilioinguinal nerve near the spermatic cord. After dissection of the cremasteric fibers off the cord, the patent processus vaginalis, or hernia sac, may be located on the anteromedial surface of the cord. The vas deferens can be seen exiting the internal inguinal ring and crossing the median umbilical ligament. The testicular vessels (i.e., spermatic artery) can be seen entering the internal ring from its origin off the aorta near the renal hilum.
Contraindications
Nothing contraindicates intervention for undescended testis in prepubertal boys.