I’ve noticed reduced scrotal fullness and possible testicular atrophy; could this be testicular atrophy and what evaluation and treatment are recommended?

Evaluation and Management of Reduced Scrotal Fullness

You need a scrotal ultrasound with Doppler to measure testicular volume and assess blood flow, plus hormonal testing (FSH, LH, testosterone) to determine whether you have true testicular atrophy and what is causing it. 1

Understanding Testicular Atrophy

Testicular volumes below 12 mL are definitively considered atrophic and associated with significant pathology, including impaired sperm production and increased cancer risk. 1 However, not all perceived "empty space" in the scrotum means atrophy—the cremasteric reflex can temporarily pull testes higher, and normal testicular position varies throughout the day. 2

The critical threshold is 12 mL volume—anything at or below this level warrants thorough investigation, especially if you're under 40 years old or have a history of undescended testicles. 1

Immediate Diagnostic Steps

Physical Examination Findings to Document

• Testicular size and consistency: Normal adult testes measure approximately 4–5 cm in length and 15–18 mL in volume by Prader orchidometer. 1
• Presence of both vasa deferentia: Absence suggests congenital abnormality (CBAVD). 3
• Size discrepancy between sides: Differences greater than 2 mL or 20% require ultrasound evaluation to exclude pathology. 1
• Testicular position: Document whether testes are fully descended into the scrotum or retractile. 2

Essential Laboratory Tests

Order morning blood work (8:00–10:00 AM) on two separate occasions: 1

• FSH (follicle-stimulating hormone): Elevated FSH >7.6 IU/L indicates impaired testicular function and reduced spermatogenic capacity. 3
• LH (luteinizing hormone): Helps distinguish primary testicular failure (elevated LH) from secondary causes (low/normal LH). 1
• Total testosterone: Low levels combined with small testes suggest hypogonadism. 1
• Prolactin: Elevated levels from pituitary adenoma or medications can cause secondary testicular atrophy. 1

Imaging Studies

Scrotal ultrasound with color Doppler is mandatory to: 1

• Calculate precise testicular volume using the Lambert formula (Length × Width × Height × 0.71). 1
• Assess testicular architecture—non-homogeneous or coarse patterns indicate irreversible damage. 4
• Evaluate blood flow—reduced arterial velocity and increased resistive index suggest atrophy. 3
• Screen for testicular masses or microcalcifications (18-fold higher cancer risk in infertile men). 4

Common Causes of Testicular Atrophy

Primary Testicular Dysfunction (High FSH)

• Klinefelter syndrome (47,XXY): Most common genetic cause; obtain karyotype if FSH elevated and volume <12 mL. 1
• History of cryptorchidism: Uncorrected or late-corrected undescended testes dramatically increase atrophy risk. 1
• Prior scrotal trauma: Causes atrophy in 50% of cases through venous thrombosis and ischemia. 5
• Previous inguinal hernia repair: Surgical trauma to spermatic cord vessels can cause thrombosis and atrophy. 6, 7
• Chemotherapy or radiation: Causes irreversible testicular shrinkage. 1
• Mumps orchitis or autoimmune orchitis: Can produce bilateral painless atrophy. 1

Secondary Testicular Dysfunction (Low FSH/LH)

• Anabolic steroid or testosterone use: Completely suppresses spermatogenesis; atrophy can persist months to years after stopping. 1
• Chronic opioid use: Suppresses GnRH secretion leading to low gonadotropins and atrophy. 1
• Hyperprolactinemia: From pituitary tumor or medications (antipsychotics, metoclopramide). 1

Systemic Conditions

• Type 2 diabetes/metabolic syndrome: Linked to functional hypogonadism and reduced testicular volume. 1
• Chronic liver disease (cirrhosis): Contributes to secondary hypogonadism. 1
• Chronic kidney disease: Associated with decreased testosterone and testicular size. 1

Cancer Risk Stratification

If you are under 30–40 years old with testicular volume <12 mL, you have a ≥34% risk of intratubular germ cell neoplasia (TIN) if testicular cancer develops. 1 If TIN is left untreated, approximately 70% progress to invasive cancer within 7 years. 2, 1

High-risk scenarios requiring urology referral: 1

• Age <30–40 years with volume <12 mL
• History of cryptorchidism combined with volume <12 mL
• Palpable testicular mass
• Testicular microcalcifications on ultrasound

You should learn testicular self-examination given the 3.6–7.4 times higher cancer risk with smaller testicular volumes. 1

Fertility Implications

Testicular volume <12 mL strongly correlates with impaired spermatogenesis, lower total sperm count, and reduced sperm concentration. 1 However, volume alone does not predict fertility—men with unilateral cryptorchidism achieve paternity rates nearly equivalent to normal men despite smaller affected testes. 4

If fertility is a concern: 1

• Obtain semen analysis (two samples, one month apart, 2–3 days abstinence before collection). 3
• Discuss sperm banking before any testosterone therapy or surgical intervention. 1
• Never start testosterone replacement without clarifying fertility intentions—exogenous testosterone causes azoospermia that may take months to years to recover. 1

When to Worry vs. When to Be Reassured

Reassuring Features (Lower Concern)

• Testicular volume 12–15 mL with normal FSH (<7.6 IU/L). 1
• Homogeneous testicular architecture on ultrasound with normal blood flow. 4
• No history of cryptorchidism, trauma, or hernia surgery. 1
• Normal secondary sexual characteristics (facial/body hair, muscle mass). 3

Concerning Features (Require Urgent Evaluation)

• Volume <12 mL with elevated FSH >7.6 IU/L (indicates spermatogenic failure). 3
• Non-homogeneous testicular architecture or reduced blood flow on Doppler. 3, 4
• Rapid testicular shrinkage over weeks to months. 1
• Palpable mass or firm nodule. 1
• Age <30 years with history of cryptorchidism. 1

Critical Pitfalls to Avoid

• Do not assume "empty scrotum" equals atrophy—retractile testes from hyperactive cremasteric reflex can mimic atrophy but are normal. 2
• Do not rely on visual inspection alone—accurate volume measurement requires orchidometer or ultrasound. 1
• Do not start testosterone therapy without hormonal workup and fertility discussion—it will worsen testicular atrophy and cause azoospermia. 1
• Do not ignore size discrepancy >20% between testes—this warrants ultrasound to exclude tumor or torsion sequelae. 1

Recommended Action Plan

1. Schedule scrotal ultrasound with Doppler to measure testicular volume using the Lambert formula (0.71 coefficient) and assess architecture/blood flow. 1

2. Obtain morning blood work (8:00–10:00 AM) on two separate days: FSH, LH, total testosterone, prolactin. 1

3. If volume <12 mL or FSH >7.6 IU/L: Refer to urology for evaluation, especially if age <40 years or history of cryptorchidism. 1

4. If fertility is a concern: Obtain semen analysis (two samples, one month apart) regardless of testicular size. 3, 4

5. If volume <12 mL with elevated FSH and age <30 years: Discuss testicular biopsy to screen for TIN given 34% risk. 1

6. Repeat semen analysis every 6–12 months if borderline findings to detect early decline. 1