What is the rationale for performing a scrotum and testicular ultrasound in a patient with low testosterone?

Scrotal and Testicular Ultrasound in Low Testosterone: Clinical Indications

Scrotal ultrasound is NOT routinely indicated for the evaluation of low testosterone alone; it should only be performed when physical examination of the scrotum is difficult or inadequate, or when a testicular mass is suspected. 1

Primary Evaluation Framework

The standard workup for low testosterone focuses on hormonal assessment and physical examination, not imaging. 1

Essential Physical Examination Components

When evaluating low testosterone, the physical exam must specifically assess: 1

• Testicular size, consistency, and presence of masses - This can typically be accomplished by palpation alone
• Varicocele presence - Usually detected clinically
• Body habitus and virilization status - Hair patterns in androgen-dependent areas
• Gynecomastia - Breast tissue examination

Hormonal Workup Takes Priority

The algorithmic approach to low testosterone emphasizes laboratory evaluation over imaging: 1

• Measure serum LH - Distinguishes primary (testicular) from secondary (pituitary/hypothalamic) hypogonadism
• If LH is low or low-normal with testosterone <150 ng/dL - Consider pituitary MRI, not testicular ultrasound 1
• Measure prolactin if LH is low/normal - Screens for prolactinoma 1
• Measure FSH if fertility is a concern - Assesses spermatogenesis 1

Specific Indications for Scrotal Ultrasound

When Ultrasound IS Indicated

Physical examination limitations: 1

• Obesity preventing adequate palpation
• Scrotal edema or inflammation obscuring examination
• Patient discomfort limiting examination

Suspected testicular mass: 1

• Palpable nodule or irregularity
• Asymmetric testicular consistency
• Unexplained testicular enlargement

Infertility evaluation context: 1

• When low testosterone occurs with abnormal semen analysis (sperm concentration <10 million/mL)
• To evaluate testicular size objectively when fertility preservation is desired
• To detect varicoceles not clearly identified on physical exam

When Ultrasound is NOT Indicated

Routine low testosterone workup - The 2018 AUA guideline on testosterone deficiency does not include scrotal ultrasound in the diagnostic algorithm for uncomplicated low testosterone. 1

Normal physical examination - If testes are normally descended, of normal size and consistency, without masses, ultrasound adds no diagnostic value. 1

Clinical Reasoning

The rationale for limiting ultrasound use stems from the pathophysiology of testosterone deficiency: 1

• Secondary hypogonadism (low LH, low testosterone) originates from pituitary/hypothalamic dysfunction - testicular imaging is irrelevant
• Primary hypogonadism (high LH, low testosterone) indicates testicular failure, but the diagnosis is made hormonally, not radiographically
• Testicular pathology causing hypogonadism (tumors, infiltrative disease) typically presents with palpable abnormalities

Special Populations

Infertility patients: Scrotal ultrasound has higher utility when low testosterone coexists with infertility concerns, as it can identify structural abnormalities affecting spermatogenesis (varicoceles, testicular microlithiasis, testicular atrophy). 1, 2

Post-chemotherapy or radiation: While these patients warrant testosterone measurement even without symptoms 1, ultrasound is only indicated if physical exam suggests testicular damage or mass.

Congenital adrenal hyperplasia: Testicular adrenal rest tumors can cause primary testicular failure; ultrasound may be warranted if CAH is present with abnormal testicular exam. 3

Common Pitfalls

• Ordering ultrasound reflexively - This wastes resources when hormonal evaluation and physical exam are sufficient 1
• Missing pituitary pathology - Focusing on testes when the problem is central (low LH should prompt pituitary MRI, not testicular ultrasound) 1
• Inadequate physical examination - Proper testicular palpation eliminates most indications for ultrasound 1