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

Area of Science:

• Gastroenterology and Hepatology
• Surgical Anatomy
• Medical Imaging

Background:

• Growing interest in flexible endoscopic ultrasound (EUS) probes for transrectal applications.
• Need for standardized techniques and anatomical understanding for trans-anorectal ultrasound.

Purpose of the Study:

• To describe techniques and anatomical considerations for trans-anorectal ultrasound using flexible curved linear array EUS (CLA-EUS).
• To identify key landmarks for navigation and staging of rectal cancers.
• To detail pelvic organ anatomy and anal canal imaging via CLA-EUS.

Main Methods:

• Review of techniques for trans-anorectal ultrasound using flexible CLA-EUS probes.
• Description of anatomical landmarks, including bony structures, pelvic organs, and vascular structures.
• Detailed imaging descriptions of the prostate, seminal vesicles, bladder, uterus, cervix, ovaries, anal canal, and pelvic floor muscles.

Main Results:

• Orientation in the ano-rectum with flexible CLA-EUS can be challenging, requiring reference to bony and pelvic organ structures.
• Identification of key vascular and anatomical landmarks crucial for rectal cancer staging (N and M).
• Comprehensive description of pelvic organ and anal canal anatomy as visualized by CLA-EUS, noting differences from radial EUS.

Conclusions:

• Flexible CLA-EUS is a valuable tool for trans-anorectal applications, including tissue sampling and therapeutics.
• Mastery of anatomical landmarks is essential for successful and safe navigation during trans-anorectal ultrasound procedures.
• This review provides a foundational guide for understanding CLA-EUS anatomy in the ano-rectal region.