LAUSR

Background Congenital abnormalities are not very common and are even rarer when two or more are combined. Congenital malformation of the superior mesenteric vein may not affect normal development, or it may lead to moderate or even severe symptoms. In combination with intestinal malrotation, however, it may lead to the need for surgical intervention in the early years of life. Case presentation We present the case of a 22-year-old patient who had been diagnosed with iron deficiency anaemia at the age of two months. As a result of the absence of the proximal section of the superior mesenteric vein, the patient has always needed iron supplements and an occasional erythrocyte transfusion. This has resulted from the formation of collaterals throughout the small bowel, causing chronic blood loss with its clinical manifestation. Although, there are some congenital abnormalities of the superior mesenteric vein, the absence of the superior mesenteric vein is rare, and in this case the clinical course was quite severe. Therefore, we planned bypass surgery for this patient to reduce the duodenal collaterals and resolve the persistent anaemia caused by chronic blood loss from the duodenum. We successfully performed the surgery consisting of the formation of anastomosis between the large collateral vein from the distal end of the superior mesenteric vein and the anterior inferior pancreaticoduodenal vein. Conclusion The purpose of this case report is to describe the rare anatomical malformation of the superior mesenteric vein accompanied by intestinal malrotation, with its potential clinical implications regarding symptoms, clinical presentation, and the impact on potential surgery planning.