Introduction:
Superior mesenteric vein thrombosis (SMVT) and portal vein thrombosis (PVT) are rare, early complications of surgically treated acute appendicitis. They develop secondary to ongoing inflammation in the peritoneal cavity, in organs that drain blood via the portal vein. Early diagnosis can be difficult due to the lack of specific symptoms.

Aim:
Description of a rare complication following surgical treatment of acute appendicitis.

Case study:
We present the case of a 26-year-old patient who returned to our hospital 7 days after appendectomy for acute appendicitis, and 5 days after discharge, with severe pain in the epigastrium and vomiting. Ultrasonography and computed tomography (CT) with contrast (angio-CT) of the abdominal cavity were performed, revealing SMVT and PVT.

Results and discussion:
We administered unfractionated heparin in the therapeutic range and antibiotics, followed by low-molecular-weight heparin from 2nd day of treatment. The pain completely disappeared with an associated decrease in D-dimer levels. On the 7th day of treatment, a repeat angio-CT scan showed numerous thrombi within the lumen of the portal vein, superior mesenteric vein, and its branches. Inflammatory infiltrations in the adipose tissue surrounding the mesenteric vein had decreased. The patient was discharged home well on 8th day of treatment.

Conclusions:
Appendicectomy for appendicitis is one of the most commonly performed surgical procedures, with a low rate of major complications. SMVT and PVT are rare but potentially fatal complications, and this case highlights the importance of early diagnosis and introduction of appropriate treatment.