What are the recommended tests for diagnosing undescended testis?

Diagnostic Evaluation of Undescended Testis

Physical examination alone is the primary diagnostic test for undescended testis—imaging studies such as ultrasound should not be performed prior to specialist referral, as they rarely assist in clinical decision-making and have poor diagnostic accuracy. 1

Primary Diagnostic Approach: Physical Examination

The diagnosis of undescended testis relies entirely on careful physical examination by an experienced provider. 1, 2

Key Physical Examination Technique

• Palpate the testis at each well-child visit to assess quality and position, starting from the external inguinal ring and sweeping downward toward the scrotum. 3, 2

• Examine in a warm room with the child relaxed, in both supine and cross-legged sitting positions to minimize cremasteric reflex. 2

• Assess scrotal symmetry visually—asymmetric scrotum strongly predicts true undescended testis rather than retractile testis. 4

• Determine if the testis is palpable or non-palpable, as this fundamentally changes surgical approach. More than 70% of cryptorchid testes are palpable by an experienced examiner. 1

• Distinguish true undescended testis from retractile testis—a retractile testis can be manually brought into the scrotum and remains there temporarily without tension, while an undescended testis cannot be manipulated into a stable scrotal position. 2

Why Imaging Should NOT Be Used

Ultrasound and other imaging modalities have unacceptably poor performance characteristics and should be avoided. 1

• Ultrasound sensitivity for localizing non-palpable testis is only 45%, with specificity of 78%, making it unreliable for clinical decision-making. 1

• In one prospective study, ultrasound agreed with pediatric urologist examination in only 34% of cases for palpable undescended testis. 5

• Ultrasound cannot reliably confirm testicular absence, which is critical information—only surgical exploration can definitively determine this. 1

• Imaging delays appropriate referral and treatment without adding diagnostic value. 1, 2

• The Choosing Wisely Canada campaign specifically recommends against ultrasound for evaluating undescended testes. 2

Historical and Clinical Features That Support Diagnosis

Obtain specific historical details that increase likelihood of true undescended testis:

• History of undescended testis noted at birth strongly predicts persistent cryptorchidism. 4

• Prematurity significantly increases risk—15-30% of premature infants have undescended testes at birth compared to 1-3% of full-term infants. 3, 4

• Gestational age and birth weight—nearly 100% of extremely low birth weight infants (<900g) have undescended testes at birth. 3

Laboratory Testing for Specific Clinical Scenarios

Bilateral Non-Palpable Testes in Newborns (URGENT)

This is a medical emergency requiring immediate specialist consultation to rule out life-threatening congenital adrenal hyperplasia and disorders of sex development. 3, 6

Required urgent laboratory evaluation includes:

• Serum electrolytes to assess for salt-wasting crisis. 6

• Karyotype analysis to determine genetic sex. 6

• Müllerian inhibiting substance (MIS) to determine if functional testicular tissue is present. 1, 6

• Inhibin B (undetectable with elevated FSH and LH suggests anorchia). 1

• Serum FSH and LH levels—elevated levels with undetectable MIS and inhibin B indicate anorchia. 1

HCG Stimulation Test (Limited Role)

• HCG stimulation testing is disputed and not routinely recommended, as failure to respond does not definitively diagnose anorchia—testicular dysgenesis with undescended testis may also fail to respond. 1

• If used, must be confirmed with elevated FSH/LH and undetectable MIS/inhibin B to diagnose isolated anorchia. 1

Surgical Exploration as Definitive Diagnostic Test

For non-palpable testes, diagnostic laparoscopy or open surgical exploration is the gold standard to confirm presence or absence of testicular tissue. 1, 6

• No radiological test can conclude with 100% accuracy that a testis is absent—surgical exploration is mandatory for definitive diagnosis. 1

• Laparoscopy allows simultaneous diagnosis and treatment if viable testis is identified. 6

Timing of Referral

• Refer to surgical specialist by 6 months of corrected gestational age if testes remain undescended, as spontaneous descent after this age is unlikely. 1, 3, 2

• Do not delay referral for imaging studies—refer based on physical examination findings alone. 1, 2

Common Pitfalls to Avoid

• Ordering ultrasound before referral—this is the most common error, occurring in 50% of referrals in one study, and provides no clinical benefit. 5, 2

• Confusing retractile testis with undescended testis—70% of referrals for "undescended testis" are actually normal or retractile testes, particularly in boys aged 1-10 years. 4

• Delaying referral beyond 6 months—most boys are referred at median age of 43-45 months, well beyond the recommended timeframe. 7, 4

• Failing to recognize bilateral non-palpable testes as an emergency in newborns. 3, 6