I went into the er in june of 2021 for rectal bleeding and a ct scan was performed of my abdomen and pelvis. should i be concerned with this: there is a prominent left periaortic lymph node measuring 13 mm short axis. spoke to pcp and no worry?

Translation: prominent= easy to see, it does not necessarily mean anything bad. Your cited measurement is a normal size for a lymph node.

Imaging was not diagnostic for your symptom of rectal bleeding suggesting a mildly enlarged lymph node, finding that will have to be placed in clinical context, specifically if still having any symptoms.

Depends on age. If you are older you should be seen by a Gastro-Ent. to determine cause which will include exam and possibly other tests like colonoscopy. Good luck.