What are the common causes of acute scrotal pain? The prevalence of different etiologies has varied in different studies. Testicular torsion, epididymitis and adnexal torsion are the most common causes, together accounting for 85% of the causes. 1. Testicular torsion: The incidence of testicular torsion is about 1/4000 in young men younger than 25 years of age and is more frequent on the left side. 2753 patients were admitted to hospital with testicular torsion in the UK in 2012-2013, the average age of these patients was 16 years. Testicular torsion usually occurs in newborns and late adolescence, but cases have been reported in all age groups. Testicular torsion occurs when the spermatic cord rotates along its longitudinal axis resulting in obstruction of the blood supply to the testis and is usually spontaneous. Testicular torsion can be divided into two types: intratesticular and extratesticular. The intratesticular type is caused by the absence of the posterior aspect of the testis and the fixed portion of the testicular sheath, where the testis is free to rotate within the testicular sheath. This anatomical abnormality, also known as “pendulum malformation”, has a prevalence of about 12% in men; 40% of these patients are bilateral. With this type of anatomic abnormality, testicular torsion usually occurs during adolescence. In contrast, the extra-sphincteric form usually occurs during the fetal and neonatal periods. Testicular torsion occurs intrauterine or in the perinatal period, when the testis is not yet immobilized in the scrotum by the testicular lead. As a result, the spermatic cord and sheath torsion occur simultaneously within or below the inguinal canal. 2, Epididymo-orchitis, epididymo-orchitis and orchitis: Epididymo-orchitis is an inflammation of the epididymis and testis, and the etiology of the disease is usually an infection secondary to urinary reflux, uropathogens, or infections due to sexually transmitted diseases. Inflammation confined to the epididymis is called epididymitis, while confinement to the testicles is called orchitis. The cause of epididymo-orchitis in children is inconclusive, with definitive evidence of the cause found in only 25% of patients. In post-pubertal males with a history of unprotected sex, the cause is most often a sexually transmitted disease. Urinary tract infections can cause acute epididymitis in men of any age. Therefore, it is important to know the risk factors for urinary tract infections, such as (anatomical or functional) urethral abnormalities or recent invasive urinary tract manipulation (e.g., catheterization or cystoscopy). 3, Testicular adnexal torsion ( cyst of Morgagni, cyst of Morgagni): The cyst of Morgagni is a small embryonic remnant of the upper pole of the testis, also known as the testicular adnexa. Testicular adnexal torsion can be spontaneous. After testicular adnexal torsion, ischemia of the cyst can lead to pain. Testicular adnexal torsion usually occurs in prepubertal males. What are the less common causes of acute scrotal pain? 1, acute idiopathic scrotal edema: Acute idiopathic scrotal edema is self-limiting edema of the scrotal skin with normal testicles and epididymis. It is more common in children under 10 years of age and usually has a unilateral onset. The diagnosis is confirmed by ultrasound findings of thickened scrotal skin and normal testes. The cause of acute idiopathic scrotal edema is not known, and it is not excluded that it is caused by allergic reaction. 2. Testicular cancer: Testicular cancer usually manifests as a slow-growing painless mass in the testicle or hardening of the testicle. Doctors should note that although testicular pain is not a typical manifestation of testicular cancer, it is reported that as many as 20% of testicular cancer patients have testicular pain, which may be caused by bleeding within the tumor. Moreover, nearly 10% of patients with inflammatory testicular cancer have manifestations similar to epididymo-orchitis, leading to misdiagnosis. 3, Varicocele: Varicocele is due to testicular venous valve insufficiency that leads to venous reflux, which makes the veins in the scrotum abnormally dilated, prolonged and tortuous. 15-20% of adolescents will have varicocele, and it is rare in children under 10 years old. It is most common on the left side (78%-93%). Varicocele can cause pain, edema and low fertility. 4. Testicular syringomyelia: The syringomyelia in the spermatic cord does not close, leading to inflow of fluid from the abdominal cavity and formation of testicular syringomyelia. 5. Testicular Injury: Most testicular trauma has no specific history; the typical history is of a violent blow to the testicle, a straddle injury, or a penetrating injury, the latter of which presents with traumatic inlet and outlet. A complete clinical examination should be performed for any associated injury. The injury may result in an accumulation of blood in the scrotum – the testicle ruptures, the fibrous tissue covering the testicle (tunica albuginea) may be torn, or a hematoma may develop. 6. Involving pain: Inguinal scrotal hernias may radiate to the scrotum and have a clinical presentation similar to scrotal disease. Typically, an incarcerated hernia will be edematous and tender to palpation. Abdominal pain is also present, and if the hernia contents contain small bowel that has become obstructed, the patient may vomit. Appendicitis and inflammation of the renal flexure of the colon also present similarly to scrotal disease. A detailed history, physical examination, and imaging (if necessary) can identify scrotal edema and testicular torsion due to these conditions.