The fountain sign is a sonographic sign described in acute idiopathic scrotal edema (AISE).
It refers to the appearance of the pattern of vascularity seen during transverse color Doppler sonography of the scrotum with both testes together 1. In this transverse view, in patients with AISE, marked bilateral and symmetrical hypervascularity of the scrotal sac wall can be detected, resembling the appearance of a fountain 1. Hypoechoic scrotal wall thickening is also appreciated on these views in these patients 1.
The sign is thought to be produced due to increased blood flow (hyperemia) in the peritesticular scrotal soft tissues, which become edematous and thickened in AISE 1.
Although more research needs to be conducted on this radiographic sign, it may be able to aid in differentiating AISE from other common causes of the acute scrotum such as epididymo-orchitis, testicular torsion, and torsion of the appendix testis.