In his excellent monograph on the anatomy and pathology of the rarer forms of hernia, Moynihan1 very accurately defines the different types of bilocular hernia.
The essential feature of both the properitoneal and the interstitial protrusions is that the loculi have a common neck, osteum abdominale. In the properitoneal the inner loculus lies between the serosa and the fascia transversalis, the outer usually occupying the ring or canal, while in the interstitial the upper loculus may be interor extra-parietal, and the lower in the inguinal canal, the loculi having a common outlet to the abdominal cavity.
The presence of two distinct hernial sacs, the one opening into the abdomen at the internal ring, the other having a distinct neck at the external ring, that is to say, the presence of both the direct and the indirect forms in a hernia on the same side is, so far as I
ALLISON CC. DOUBLE INGUINAL HERNIA UPON THE SAME SIDE: ILLUSTRATION.. JAMA. 1900;XXXIV(17):1048–1049. doi:10.1001/jama.1900.24610170028002