Bilateral impalpable testes at birth are associated with complex endocrine disorders and prune belly syndrome, so should be investigated within 2 weeks.
Warm hands and room will help find a testis, of course. Can the testis be manipulated into the scrotum? In that case retractile, not undescended.
A testis can be undescended but palpable eg in the inguinal canal. If retractile, then needs no intervention.
For suspected unilateral undescended testis, re-examine at 6–8 weeks, and again at 4–5 months of age, if needed. If the testis remains undescended, refer to paediatric surgery to consider surgery.
Rarely non retractile testis found later in childhood – “ascending testis” – ?cord shortening. Usually age 8-10, not so urgent as initial development already complete. Seems to be more likely if retractile in the first place – family should keep an eye on them!
If not palpable then may be intraabdominal, absent, small (dysplastic, but in the right place) or else ectopic. Imaging is not sensitive so often diagnostic laparascopy is required. Ectopic testes are found in the perineum or femoral triangle, they are usually normal and orchidopexy is straightforward.
An undescended testis is seen in 5% of term infants but less than 2% of 1yr olds. It is theorized that part of the reason for poor descent is that they are fundamentally abnormal. If left for more than 4yrs then histological abnormalities often seen so generally repaired/removed between 1 and 4 yrs of age. Commonly associated with inguinal hernia, in which case fixed earlier with the hernia.
After surgery, advise self examination as increased risk of testicular cancer.[NICE CKS]