Which landmarks form the ostomy triangle?

• A. The iliac crest and the pubic symphysis
• B. The xiphoid process, the ASIS, and the pubic bone
• C. The umbilicus, the anterior superior iliac spine, and the pubis symphysis
• D. The umbilicus, the pubic symphysis, and the greater trochanter

Answer: (C)

A reliable, repeatable site for the stoma is planned by outlining an ostomy triangle using three fixed abdominal landmarks. The corners are the umbilicus, the anterior superior iliac spine (ASIS), and the pubic symphysis. This triangle provides a stable, wrinkle-free zone on the abdomen where the stoma can be placed so the appliance adheres well, is easy to access, and won’t be affected by belt lines or folds.

Why this set is best: these landmarks offer a consistent reference point on almost every patient, helping the clinician mark a spot that sits on a relatively flat area of the abdomen and is suitable for a appliance pouching system. It also helps keep the stoma away from scars, creases, and the belt line, which reduces leakage risk and skin irritation.

The other options use landmarks that don’t form the standard, widely taught ostomy triangle or place the stoma in less suitable locations, such as too high, too lateral, or near bony prominences, making them less ideal for predictable, functional site marking.