Testicular Microlithiasis

Testicular microlithiasis is an ultrasound finding of tiny calcified foci within the testis, each about 1 to 3 mm, bright and without acoustic shadowing.

It is classic when 5 or more microliths are seen in at least one ultrasound field, and limited when fewer than 5 are seen.

It is found in roughly 0.6 to 9% of men scanned, depending on the population, and in about 2 to 5% of healthy young men.

It is a finding, not a disease. The clinical question is germ cell tumour risk, and in an otherwise low risk man with isolated microlithiasis the risk is not meaningfully raised.

Pathophysiology. Microliths are laminated calcium deposits around degenerating epithelial cells in the lumina of the seminiferous tubules. They may reflect abnormal tubular function and debris clearance.

Associations:

• Cryptorchidism, testicular atrophy, infertility and varicocele.
• Previous or contralateral germ cell tumour, and germ cell neoplasia in situ.
• Klinefelter syndrome and Down syndrome.
• Pulmonary alveolar microlithiasis, Carney complex and androgen insensitivity.

The finding is more frequent in men with germ cell tumours than in the general population. The reason is shared developmental disease rather than the stones themselves.

Most men are asymptomatic, and the finding arises when ultrasound is done for pain, swelling, infertility or trauma. A palpable mass, a hard or irregular testis, or focal pain is not explained by microlithiasis and points to tumour, infection or torsion.

• High frequency scrotal ultrasound (linear probe of 7 to 15 MHz) of both testes: number of microliths in the most affected field, laterality, testicular volume, echotexture, focal hypoechoic lesion, and varicocele.
• Examination of the testes, epididymis and cord, and of the abdomen and breasts.
• AFP, beta-hCG and lactate dehydrogenase when a focal lesion, atrophy or other risk factors are present.
• Semen analysis in men with infertility.
• MRI of the scrotum when an equivocal lesion needs characterisation.
• Testicular biopsy for germ cell neoplasia in situ only in selected men (previous testicular tumour with contralateral microlithiasis plus testicular volume under 12 mL or age under 40).

Differential diagnosis.

• Calcified testicular tumour or burned out tumour
• Scarring after infection, infarction or trauma
• Tunical or epididymal calcification
• Scrotal pearls
• Granulomatous disease (tuberculosis, sarcoidosis)
• Calcified haematoma

• Isolated microlithiasis in an asymptomatic man with a normal examination and no risk factors: no routine ultrasound surveillance and no tumour markers. Reassure, and teach monthly testicular self-examination with prompt review for any lump, swelling or pain.
• Microlithiasis with risk factors (previous or contralateral germ cell tumour, cryptorchidism, testicular volume under 12 mL, or infertility): ultrasound and examination every 12 months, usually until age 55, with markers if anything changes. Review at once for a new lesion.
• Contralateral biopsy for germ cell neoplasia in situ is considered after a previous testicular tumour when there is also microlithiasis, atrophy (volume under 12 mL) or age under 40. If germ cell neoplasia in situ is found: radiotherapy to the testis at 16 to 20 Gy in 2 Gy fractions (which ends sperm production and impairs Leydig cell function), or orchidectomy, or surveillance in men who want fertility. Offer sperm banking before treatment.
• Orchidopexy for undescended testis, ideally by 12 to 18 months of age.
• Infertility and varicocele are managed on their own indications.
• Children and adolescents: no surveillance for isolated microlithiasis. Ultrasound yearly from puberty when a risk factor is present.

Monitoring. Yearly ultrasound and examination where indicated. Earlier review for a new lump, pain, swelling or growth of a lesion.

Referral and escalation. Refer to urology for any solid lesion, atrophy with risk factors, or infertility. Urgent referral for a palpable mass or a focal lesion on ultrasound.