Trans-anorectal curved linear-array endoscopic ultrasound: Comprehensive pictorial guide (with videos)

Interest in using flexible endoscopic ultrasound (EUS) probes for transrectal applications is growing, including tissue sampling and therapeutic procedures. In this review, we describe of the techniques and anatomical considerations for trans-anorectal ultrasound using a flexible, curved linear array EUS probe (CLA-EUS). Orientation with flexible CLA-EUS in the ano-rectum can be challenging; bony structures should be used as the posterior reference and pelvic organs as the anterior reference structures. Key landmarks, including aortic division, iliac vessels and their divisions, and peritoneal reflections and recesses are described. These vascular and anatomical landmarks are essential for N and M staging of rectal cancers. The anatomy and zonal structure of the prostate, along with the appearance of seminal vesicles, ejaculatory ducts, bladder, ureters, uterus, cervix, and ovaries on CLA-EUS, are detailed. Finally, we describe the anatomy and imaging of the anal canal and pelvic floor muscles, emphasizing differences between CLA-EUS and radial EUS imaging techniques.