Is a Small Epididymis Concerning in an Adult Male?
A small epididymis in an adult male warrants further evaluation, as it may indicate underlying pathology affecting fertility, particularly when associated with small testicular volume, and can be a sign of testicular dysgenesis, obstruction, or developmental abnormalities. 1
Clinical Significance and When to Investigate
Scrotal ultrasound is specifically indicated when a small testis is present and the epididymis appears large in comparison to total testicular volume, as this disproportionate relationship suggests potential pathology. 1 This finding may indicate:
- Testicular dysgenesis with impaired spermatogenesis 1
- Developmental abnormalities affecting the entire reproductive tract 1
- Atrophic changes from prior inflammation or vascular compromise 1
Differential Diagnosis Framework
Primary Concerns with Small Epididymis
In the context of infertility evaluation, a small epididymis combined with small testicular volume (particularly <12 mL) raises concern for:
- Non-obstructive azoospermia with testicular atrophy and elevated FSH (>7.6 IU/L) 1
- Genetic abnormalities including Klinefelter syndrome or Y-chromosome microdeletions 1
- History of cryptorchidism affecting both descended and undescended testes, where the contralateral testis may show smaller volume and structural abnormalities 1
Contrast with Enlarged Epididymis
An enlarged epididymis suggests obstruction or inflammation, not developmental hypoplasia. 1 Ultrasound findings of obstruction include:
Recommended Evaluation Algorithm
Step 1: Physical Examination Details
- Testicular volume assessment using Prader orchidometer (normal ≥15 mL) 1
- Testicular consistency (soft suggests impaired spermatogenesis) 1
- Epididymal palpation for induration, enlargement, or absence 1
- Vas deferens presence bilaterally 1
Step 2: Laboratory Workup
If small epididymis is associated with small testes (<12 mL) or infertility concerns:
- Semen analysis (two samples, 2-7 days apart) 1
- FSH level: Elevated (>7.6 IU/L) suggests non-obstructive azoospermia 1
- Testosterone and LH to assess hypogonadism risk 1
Step 3: Genetic Testing Indications
Karyotype testing is recommended for:
- Azoospermia or sperm concentration <5 million/mL with elevated FSH, testicular atrophy, or impaired sperm production 1
Y-chromosome microdeletion testing is mandatory for:
- Azoospermia or sperm concentration <1 million/mL 1
- Recommended for sperm concentration <5 million/mL 1
Step 4: Imaging
Scrotal ultrasound with Doppler is indicated when:
- Large hydrocele, inguinal testis, or thickened scrotal skin prevents accurate physical examination 1
- Small testis with disproportionately large epididymis 1
- Suspicion of testicular dysgenesis (non-homogeneous architecture, microcalcifications) 1
- Concern for testicular malignancy (infertile men have 1.91 times higher risk) 1
Critical Clinical Pitfalls
Do not dismiss a small epididymis as a normal variant without:
- Assessing testicular volume and consistency 1
- Evaluating fertility status if the patient desires future paternity 1
- Screening for testicular malignancy risk, particularly with microcalcifications (18-fold higher cancer risk) 1
Men with cryptorchidism history (even if corrected) may have bilateral testicular abnormalities including smaller volume and reduced fertility markers, requiring counseling about 35-53% paternity rates with bilateral cryptorchidism and increased testicular cancer risk (3.6-7.4 times higher). 1
Impact on Fertility and Quality of Life
A small epididymis associated with testicular atrophy predicts:
- Impaired spermatogenesis with potential azoospermia or severe oligozoospermia 1
- Reduced fertility potential requiring assisted reproductive technology 1
- Possible hypogonadism affecting quality of life 1
The epididymis is essential for sperm maturation, motility acquisition, and fertilizing capacity; however, a small epididymis itself is more a marker of underlying testicular pathology than a direct cause of infertility. 2, 3