The presence or absence of an impalpable testis can be predicted from clinical observations alone.

Objective: To evaluate, in a prospective study, the accuracy of predicting the presence or absence of unilateral or bilateral impalpable testes from a clinical examination, particularly whether the contralateral descended testis (CDT) is hypertrophied.

Patients And Methods: Whether the ipsilateral scrotal appendages were palpable, and the size of the CDT, were determined before surgery in a series of patients, and compared with age-matched controls. Between 1992 and 2000, 100 impalpable testes in 86 consecutive patients (mean age at orchidopexy 45 months, range 6-223; 66% <36 months) were evaluated and treated. In addition to the presence or absence of palpable ipsilateral scrotal appendages, the size of the CDT, when present, and the intraoperative findings were recorded. Logistic regression analysis was used to model the probability of the presence or absence of the testis, as determined by the preoperative clinical findings alone.

Results: Of the 86 testes that were located at surgery, 50 (58%) were intracanalicular, 28 (32%) intra-abdominal and the remainder (10%) were in the superficial inguinal pouch. Of 13 patients with the 'vanishing testis syndrome', the atrophic testicle was intracanalicular in nine, in the upper scrotum in three and intra-abdominal in only one. All viable testes were successfully relocated in the scrotum, with one atrophic after surgery. The positive predictive value (PPV, with 95% confidence interval) of a testis being present when the ipsilateral appendages were palpable and the CDT was not hypertrophied was 0.93 (0.83-0.97). Conversely, the PPV of the impalpable testis being absent when the appendages were impalpable and the CDT was hypertrophied was 0.95 (0.64-0.99).

Conclusion: When evaluating and surgically treating impalpable testes, the presence of palpable ipsilateral scrotal appendages and a CDT with no hypertrophy is associated with a 93% likelihood of discovering a testis that can be successfully relocated to the scrotum. Conversely, when the ipsilateral scrotal appendages cannot be palpated and the CDT is hypertrophied, there is a 96% probability that the impalpable testis is absent (vanishing testis syndrome). This readily available information may be valuable in preoperative counselling and planning.