Differential diagnosis of fat-containing lesions in the inguinal canal using ultrasound

Abdominal hernias are usually located in the inguinal canals. Differential diagnosis of hernias should consider other pathologies, which typically occur at this site. The aim of this review paper is to present fat-containing lesions located in the inguinal canal based on both our own experience and literature. The first part of the paper describes the embryogenesis and differences in the structure and content of male and female inguinal canal. The canal is clearly wider in men, which results from the presence of the spermatic cord and its components. The female canal contains only the narrow round ligament of the uterus. The second part of the paper discusses the incorrect use of the term "lipoma" for retroperitoneal fat, which penetrated into the lumen of the patent processus vaginalis - the authors using this term acknowledge its incorrectness. These lesions often coexist with oblique inguinal hernia and should be excised during a surgery as they may cause inguinal pain. As for other fat-containing inguinal pathologies, we discussed lipomatosis of the spermatic cord, liposarcoma and the greater omentum. Differential diagnosis of these lesions considers their echogenicity, echostructure and vascularity. Furthermore, attention was paid to the adipose tissue surrounding the lower epigastric vessels, which may be incorrectly localized in the inguinal canal. Finally, the importance of proper diagnostic methodology and knowledge of the inguinal anatomy for the correct ultrasonographic diagnosis was emphasized.