The inguinal canal is a natural passage or opening through the muscles of the abdominal (belly) wall. Before babies are born, the testicles descend from the abdomen into the scrotum through the inguinal canal, or a ligament passes through the canal to the large folds of skin (labia) surrounding the vagina.

The inguinal canal varies in length, depending on a person's age. It can be up to 7.5 cm (3 in.) in adults.

The inguinal canal usually closes before a baby is born or by age 2. But the canal may stay open into adulthood. If the canal is open, tissue from inside the abdomen may bulge through the canal, causing an indirect inguinal hernia.