[TA] a sickle-shaped fold of peritoneum, sometimes found arching between the left side of the duodenojejunal flexure and the medial border of the left kidney; its right free edge contains the ascending branch of the left colic artery and inferior mesenteric vein; forms anterior boundary of the paraduodenal recess.paraduodenal recess. SYN: plica paraduodenalis [TA], Treitz arch.