The preduodenal portal vein, which runs at the ventral side of the duodenum is a rare congenital anomaly in humans. The theory to account for the development of a preduodenal portal vein was put forth by His in 1885 [1], and an example of this anomaly in a pig embryo was reported by Begg in 1912 [2]. The first case report in humans was made by Knight in 1921 [3], who found this anomaly in a dissecting-room cadaver.

Since then, many cases have been reported in children and adults, as well as during surgery [4-6]. It is found sporadically during investigations of epigastric pain or other symptoms, such as vomiting or jaundice. This anomaly has a high association with other congenital anomalies, such as malrotation; situs inversus; pancreatic, duodenal, biliary system, and splenic anomalies; as well as dextrocardia. Its incidence is about 1 in 10000 [7,8]. PDPV is found in only 4% of cases with congenital obstruction [9]. Such an anomalous vein is a hazard in operations on the duodenum or biliary tract because of the dangers of inadvertent division or ligation.

A one-day-old female outborn neonate weighing 2.5 kg, born to a primigravida mother at 37 weeks of gestation by cesarean section, presented to us because of persistent non-bilious vomitings. An antenatal ultrasound scan was suggestive of duodenal atresia with polyhydramnios. On admission, the baby had respiratory distress. Per abdominal examination revealed upper abdomen distended with no visible peristalsis and no palpable lump. On cardiovascular examination, a systolic murmur of grade 3/6 intensity was heard, with the rest of the examination unremarkable. Clinical diagnosis of proximal duodenal obstruction with congenital heart disease was made. Routine supportive care and IV fluids were initiated as per unit protocol. The sepsis screen sent at admission was negative. X-ray erect abdomen done revealed a hugely distended stomach. 2DECHO done was suggestive of the infracardiac type of TAPVC. Delayed passage of meconium was present with the baby first passing stools at 45 hours of life. The pediatric surgeon's opinion was taken and as per his advice, barium meal with follow-through was done which showed the delayed passage of contrast in the small intestine.

The 8th to 12th weeks of development see parts of this plexus atrophy (Figure 4). The superior and the inferior anastomosis atrophy, followed by the proximal part of the left and the distal parts of the right vitelline vein. This leaves the anastomotic network around the duodenum with one vessel, the portal vein. This vein lies posterior to the duodenum.

Fig-3: Schematic diagram of portal vein embryology. The left and right vitelline veins (colored black) form a ladder-like cross-anastomosis around the primitive foregut seen in A. In B the middle posterior anastomosis remains patent (colored black) and the remainder of the anastomosis atrophies, resulting in the normal posterior position of the portal vein (black arrow).

Fig-4: A schematic representation of PDPV development without malrotation. Note that the inferior preduodenal anastomosis remains patent (B) resulting in a pre-duodenal position of the portal vein (black arrow) (C).

Fig-5: PDPV development with malrotation. Steps A and B are the same as in Fig. 2a; however, malrotation of the primitive gut results in a PDPV.

To explain the anomaly of a preduodenal portal vein, one of two possible events can occur (Figure 4 and 5).