Which condition involves a bleed that does not cross suture lines?

Cephalohematoma is characterized by a collection of blood between the skull and the periosteum, the membrane that covers the outer surface of bones. One of the key distinguishing features of cephalohematoma is that the blood does not cross the suture lines of the skull. This is due to the fact that the periosteum is tightly adhered to the skull sutures, which confines the bleeding to the area over the specific cranial bone where the rupture of vessels occurred.

In contrast, caput succedaneum, another type of head swelling, involves edema of the soft tissues of the scalp that does cross suture lines because it is not contained by the periosteum. Erythema toxicum neonatorum is a common newborn rash and does not involve any bleeding. Imperforate anus is a congenital condition affecting the gastrointestinal tract and does not involve any bleeding or head injuries.

Understanding these distinctions helps clarify why cephalohematoma is identified by its localized nature and inability to cross suture lines, making it a uniquely recognized condition among the options presented.