Fig. 1

The pathophysiologies of anorectal and anorectosigmoid VM in KTS. Panel A: Anorectal and circumferential VM mainly drain into internal iliac vein (IIV), rarely into median sacral vein (MSV). It is noteworthy that the superior rectal vein (SRV) and inferior mesenteric vein (IMV) are not affected. Panel B: Anorectosigmoid VM drains into the IIV, the SRV and IMV, which means that the IMV and portal vein system is involved. Therefore, ectatic IMV and portal hypertension can be identified in patients. The latter is partly caused by the thrombi within VM migrating up into and obstructing the branches of portal vein via the IMV. Multifocal lymphatic malformation (LM) in spleen also can be seen in KTS patients