Which of the following investigation is used to confirm anorchia?
**Core Concept**
Anorchia, also known as vanishing testes syndrome, is a rare congenital disorder where one or both testes do not develop in the scrotum. Confirming anorchia requires a definitive diagnostic test to rule out other conditions such as undescended testes or testicular atrophy.
**Why the Correct Answer is Right**
The correct investigation for confirming anorchia is the presence of SRY gene on Y chromosome. The SRY gene is a crucial factor in testicular development and differentiation. Its presence on the Y chromosome is essential for the development of testes from the genital ridges. In cases of anorchia, the Y chromosome is usually absent or has a deletion of the SRY gene. The presence of SRY gene on Y chromosome can be confirmed through genetic testing, such as PCR or FISH.
**Why Each Wrong Option is Incorrect**
**Option A:** Serum testosterone levels may be low in cases of anorchia, but this is not a definitive diagnostic test. Low testosterone levels can be seen in various conditions, including undescended testes or testicular atrophy.
**Option B:** Ultrasound of the scrotum may show an empty scrotum or a small, non-functional testis, but it cannot confirm anorchia. Ultrasound is a useful tool for detecting testicular abnormalities, but it may not distinguish between anorchia and other conditions.
**Option C:** Chromosomal analysis may show an abnormal karyotype, but this is not a specific test for anorchia. Chromosomal abnormalities can be seen in various conditions, including genetic disorders and chromosomal deletions.
**Clinical Pearl / High-Yield Fact**
In cases of suspected anorchia, a thorough physical examination and a detailed medical history should be taken to rule out other conditions. A genetic test for the SRY gene on Y chromosome is a crucial investigation for confirming anorchia.
**Correct Answer:** D. Presence of SRY gene on Y chromosome.