Figure 6. Diagram of visceral (A and B) and visceral-systemic (C) abdominal collateral pathways. The celiac trunk and superior mesenteric artery can supply each other with bidirectional blood flow (A). The superior and inferior mesenteric arteries also can supply each other bidirectionally through the Riolano arcade (ie, the meandering mesenteric artery) (B). The inferior mesenteric artery can supply blood to the internal iliac artery via the hemorrhoidal plexus (C).