In cryptorchidism (from Greek kryptos ["hidden"] and orchis ["testis"]), the testis is not located in the scrotum; it can be ectopic, incompletely descended, retractile, and absent or atrophic.  Cryptorchidism is the most common abnormality of male sexual development.
Sir John Hunter, the British anatomist, reported this condition in 1786. In 1877, Annandale performed the first successful orchidopexy. In 1899, Bevan published the principles of testicular mobilization, separation of the processus vaginalis, and repositioning of the testis into the scrotum. Since then, testicular maldescent has been the subject of many clinical studies, but its embryology, effects on fertility, and ultimate clinical impact still remain topics of discussion and research.
Physical examination is the most important tool in the diagnostic evaluation of cryptorchidism. Closely observing the scrotum before manipulation is important. The frog-leg or catcher position may be used to facilitate palpation of the testis. Determining if the testis is palpable is essential. If the testis is palpable, ascertain whether it can be retracted. The retractile testis should stay in the dependent portion of the scrotum after manipulation.
Diagnostic laparoscopy is the most reliable technique for localizing the nonpalpable testis.
The main goals of treatment, whether hormonal or surgical, are (1) to allow the testicle to occupy a normal anatomic position, (2) to preserve fertility and hormonal production, and (3) to diagnose potential testicular malignancies. Other putative benefits include correction of associated hernias and prevention of testicular torsion.
More to read: https://emedicine.medscape.com/article/1017420-overview