A Rare Variant of the Portal Vein Formation

The portal vein (PV) is a major vessel that supplies blood to the liver and is formed by the union of the superior mesenteric vein (SMV) and the splenic vein (SV) behind the neck of the pancreas. Generally, the inferior mesenteric vein (IMV) drains to the SV. Several variations to this anatomy have been reported, with the most frequent variant being the typical pattern (Type I) just described above, followed by IMV draining into SMV, then SMV joining SV to form PV (Type III), and trifurcation of SMV, IMV, and SV (Type II) respectively. The index case that we report here is unique as it is not described in published classifications such as Thomson or Krumm et al. Such unknown variants when found during surgical procedures may lead to unexpected adverse events during surgical and radiological procedures. Therefore, reporting such variants is important in minimizing iatrogenic injuries.