External hernias of the abdomen are clinically common problems and frequently require imaging evaluation preoperatively. Various kinds of external hernias can occur in the abdominal wall. In the era of three-dimensional imaging using CT and MRI, a more precise evaluation of the structure of each hernia (hernia orifice, hernia sac, its content, and its covering) and complications such as inflammation, bowel obstruction/incarceration, and strangulation can be analyzed than before. In this presentation, we review various kinds of external hernias of the abdomen and show radiological anatomy using three-dimensional images with representative cases as well as their rare types. Understanding the membranous structures of the abdominal wall related to external hernias will be essential for GI radiologists to provide more critical information to surgeons in patient management and surgical planning.

1. General consideration of external hernias of the abdomen2. Classification of external abdominal hernias and their imaging findings: case presentations a. groin (inguinal): indirect (external), direct (internal), femoral, b. umbilical/periumbilical: cf. omphalocele, c. ventral (anterior): epigastric/hypogastric (linea alba), suprapubic, Spigelian (linea semilunaris), d. lumbar (lateral): superior lumbar (Grynfeltt-Lesshaft), inferior lumbar (Petit), e. pelvic floor (inferior): obturator foramen, sciatic foramen, perineal, f. cicatricial: traumatic, incisional, parastomal, trocar site3. Conclusions