[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Clinical exam](https://durgical.com/en/clinical-exam/) › [Kidney, genitourinary, breast and obstetric exam](https://durgical.com/en/clinical-exam/#a-renal) › Male genital exam: transillumination, cremasteric reflex, Prehn sign [Clinical exam](https://durgical.com/en/clinical-exam/) · [Kidney, genitourinary, breast and obstetric exam](https://durgical.com/en/clinical-exam/#a-renal) # Male genital exam: transillumination, cremasteric reflex, Prehn sign - Exam technique A respectful check of the penis, scrotum and testes, with consent and a chaperone, to find lumps, hernias or a twisted testis. Updated 2026-11-01 **See it in 3D:** [Scrotum](https://durgical.com/en/anatomy/scrotum/) · [Epididymis](https://durgical.com/en/anatomy/epididymis/) · [Ductus deferens](https://durgical.com/en/anatomy/ductus-deferens/) · [Testes](https://durgical.com/en/anatomy/testis/) · [Spermatic cord](https://durgical.com/en/anatomy/spermatic-cord/) · [Inguinal canal](https://durgical.com/en/anatomy/inguinal-canal/) · [Testicular veins and pampiniform plexus](https://durgical.com/en/anatomy/testicular-vein-pampiniform-plexus/) ## Key points - What transilluminates is fluid (hydrocele, spermatocele); what does not is solid (tumour) or a hernia with bowel. - Absent cremasteric reflex plus a high, tender testis: testicular torsion, a surgical emergency. - Prehn sign: relief on lifting the testis in epididymitis; it is unreliable. - Varicocele: left side, 'bag of worms', grows on standing and with Valsalva. - A hard, painless testicular lump in a young man: rule out testicular cancer. - Consent, chaperone, privacy and gloves for every genital exam. ## What it is The male genital exam covers inspection and palpation of the penis, scrotum, testes, epididymis and spermatic cord, plus a check for inguinal hernias. Three tests help with a scrotal mass or scrotal pain: transillumination (separates fluid from solid), the cremasteric reflex (almost always absent in testicular torsion) and the Prehn sign (unreliable). Torsion is an emergency: recognising it on examination saves the testis. ## Landmark anatomy - The testis is wrapped in the tunica vaginalis; fluid collecting in it is a hydrocele, which is why it surrounds and hides the testis. - The epididymis lies along the back and top of the testis; the vas deferens leaves it and runs up the spermatic cord to the inguinal canal. - The cremasteric reflex uses the genitofemoral nerve (segments L1 and L2): stroking the thigh contracts the cremaster muscle and lifts the testis. - The left testicular vein drains into the left renal vein at a right angle, which is why varicocele is far more common on the left. ## Technique, step by step - Explain what will be done and why, obtain verbal consent, offer a chaperone, protect privacy and wear gloves. - Examine standing first (hernias, varicocele), then lying down; uncover only the area needed. - Inspect the penis, skin, hair and the position of the urethral opening; if there is a foreskin, retract it gently and always return it at the end. - Inspect the scrotum: symmetry, colour, swelling; the left testis normally hangs a little lower. - Palpate each testis between the thumb and the index and middle fingers: size, consistency, surface, tenderness; then the epididymis, behind and above. - Palpate the spermatic cord up to the inguinal ring; the vas deferens feels like a firm, smooth cord. Standing, with Valsalva, look for a varicocele. - Transillumination: in a dark room, hold a penlight behind the scrotal mass; clear fluid glows, solid tissue does not. - Cremasteric reflex: lightly stroke the upper inner thigh; normally the testis on that side rises. - Prehn sign: gently lift the painful testis and ask whether the pain eases. - Hernia: invaginate the scrotal skin with a finger up to the external inguinal ring and ask the patient to cough. ## Abnormal findings - Testicular torsion: sudden severe pain, a high testis, sometimes lying horizontally, very tender, with an absent cremasteric reflex. It is a surgical emergency; tests must not delay urology review. - Epididymitis: more gradual pain, a thick, tender epididymis, sometimes with fever or urinary symptoms; the cremasteric reflex is usually present. - Hydrocele: painless, smooth swelling that transilluminates; the testis is hard to make out through the fluid. - Varicocele: a soft 'bag of worms' above the testis, mostly on the left, that grows on standing and with Valsalva and does not transilluminate. - Testicular tumour: a hard, painless lump that is part of the testis and does not transilluminate; the most common solid tumour in young men. - Inguinoscrotal hernia: a mass that reduces or bulges with a cough; if it holds bowel it may have bowel sounds and does not transilluminate. ## Common errors - Relying on the Prehn sign: its value in separating torsion from epididymitis is low. - A present cremasteric reflex does not fully rule out torsion; with clinical suspicion, urgent assessment still follows. - Some solid masses let a little light through and some thick-walled hydroceles do not; scrotal Doppler ultrasound confirms. - Forgetting to return the foreskin, with a risk of paraphimosis. - Skipping consent, the chaperone or the explanation of each step. ## Test yourself Think of the answer, then tap the question to see it. ## What does it mean when a scrotal mass glows with a penlight held behind it? That it contains clear fluid, such as a hydrocele or a spermatocele. ## Which nerve and spinal segments carry the cremasteric reflex? The genitofemoral nerve, segments L1 and L2. ## Which exam findings suggest testicular torsion? A very tender testis lying high and sometimes horizontal, with an absent cremasteric reflex. ## Why is varicocele more common on the left? Because the left testicular vein drains at a right angle into the left renal vein, with higher pressure and poorer drainage. ## What limits the value of the Prehn sign? Relief on lifting the testis can be missing in epididymitis and present in torsion, so it does not separate them reliably. [Add to my cards (5)](https://durgical.app/estudiar/?add=/en/clinical-exam/male-genital-exam-transillumination-cremasteric-reflex-prehn-sign/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Scrotum](https://durgical.com/en/anatomy/scrotum/) - [Epididymis](https://durgical.com/en/anatomy/epididymis/) - [Ductus deferens](https://durgical.com/en/anatomy/ductus-deferens/) - [Testes](https://durgical.com/en/anatomy/testis/) - [Spermatic cord](https://durgical.com/en/anatomy/spermatic-cord/) - [Inguinal canal](https://durgical.com/en/anatomy/inguinal-canal/) - [Testicular veins and pampiniform plexus](https://durgical.com/en/anatomy/testicular-vein-pampiniform-plexus/) ## Related - [Examination of the groin and abdominal wall for hernias](https://durgical.com/en/clinical-exam/examination-of-the-groin-and-abdominal-wall-for-hernias/) - [Digital rectal examination](https://durgical.com/en/clinical-exam/digital-rectal-examination/) - [Urinary symptoms: dysuria, frequency, oliguria and hematuria](https://durgical.com/en/clinical-exam/urinary-symptoms-dysuria-frequency-oliguria-and-hematuria/) - [Lymph node examination](https://durgical.com/en/clinical-exam/lymph-node-examination/) ## Related conditions - [Testicular torsion](https://durgical.com/en/conditions/testicular-torsion/) - [Hydrocele](https://durgical.com/en/conditions/hydrocele/) - [Varicocele](https://durgical.com/en/conditions/varicocele/) - [Epididymitis](https://durgical.com/en/conditions/epididymitis/) - [Testicular cancer](https://durgical.com/en/conditions/testicular-cancer/) - [Inguinal hernia](https://durgical.com/en/conditions/inguinal-hernia/) [← All of the clinical exam](https://durgical.com/en/clinical-exam/) Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis. Sources: [Testicular torsion: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000517.htm) (MedlinePlus (U.S. National Library of Medicine), 2024); [Hydrocele: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000518.htm) (MedlinePlus (U.S. National Library of Medicine), 2024); [Testicular self-exam: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003909.htm) (MedlinePlus (U.S. National Library of Medicine), 2024); [Testicle pain: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003160.htm) (MedlinePlus (U.S. National Library of Medicine), 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/clinical-exam/male-genital-exam-transillumination-cremasteric-reflex-prehn-sign/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/clinical-exam/male-genital-exam-transillumination-cremasteric-reflex-prehn-sign/