Acute idiopathic scrotal oedema (AISE) is a self-limiting condition characterised by marked oedema of the skin and dartos fascia without involvement of the deeper layers, testes, or epididymis. It is an important condition to recognise in order to avoid unnecessary surgical exploration.
While it can occur in both children and adults, it mostly occurs in children <10 years of age 3.
Swelling and erythema in the scrotal wall are characteristic, but the condition is not universally painful. AISE can be unilateral or bilateral (approximately 90% of cases are unilateral 3) and extension of erythema to the perineum or inguinal region is seen in half of cases.
The exact etiology of AISE is unclear. It has been hypothesised that it represents a hypersensitivity reaction related to a variant of angioneurotic edema. It has been associated with eosinophilia, with a 66.7% incidence in one case series.
Ultrasound is the imaging modality of choice in the investigation of the acute scrotum. Thickening and oedema of the scrotal wall, hypervascularity of the scrotum, and normal appearance of the testes are considered specific for the condition.
Geiger et al. has described the “fountain sign,” a novel finding on colour Doppler interrogation which is highly suggestive of the diagnosis 7. The “fountain” depicted on transverse imaging of the scrotum is due to marked increased hypervascularity in the scrotal wall which derives its blood supply from branches of the deep external pudendal and internal pudendal arteries via the anterior and posterior sacral arteries.
Other sonographic findings described in AISE include mild reactive hydrocoele and enlarged, hypervascular inguinal lymph nodes.
Treatment and prognosis
AISE is a self-limiting condition, which tends to resolve in around 3-5 days. NSAIDs and antibiotics have been used in management. A correct diagnosis can obviate surgical intervention and the characteristic ultrasound findings can be particularly helpful given the overlap in clinical presentation with testicular torsion and other conditions. The use of Doppler ultrasound was shown to reduce the rate of surgical exploration by more than half in one study.
Acute idiopathic scrotal oedema was first reported as a cause of the acute scrotum by Qvist in 1959.
The clinical differential diagnosis for AISE includes other causes of acute scrotum such as:
- testicular torsion
- Henoch-Schönlein purpura (in the setting of a paediatric patient with joint pain and rash) 8
- torsion of the testicular and epididymal appendages
Lymphatic malformations of the scrotum can also present with bilateral scrotal pain and hydrocoele.
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