Massive right atrium thrombus in an extremely‐low‐birthweigh
A 24 weeks and 3 days old female infant weighing 543 g was delivered by emergency cesarean section after preterm labor. The infant was intubated and endotracheal surfactant was administered. An umbilical venous catheter (UVC) was inserted to administer inotropic medications and to start early parenteral nutrition (PN), including calcium, phosphate, and amino acids. After beginning enteral feeding, the infant developed progressive abdominal distension on day 6. After removal of the UVC for abdominal surgery, a peripherally inserted central catheter (PICC) was inserted into her right lower limb. Thoracoabdominal radiography demonstrated free intraperitoneal air and the PICC tip touching the inferior vena cava (IVC).

Laparotomy revealed a small perforation located 6 cm from the ileocecum on the oral side therefore loop ileostomy, including the perforation site, was performed. After the operation, she was able to tolerate enteral feeding. On day 9, lipid infusion was started through the PICC to provide sufficient energy and essential fatty acids. On day 22, her blood pressure suddenly dropped from 55/35 mmHg to 37/ 21 mmHg and she developed oliguria and hyponatremia. After hydrocortisone therapy, based on the diagnosis of late-onset circulatory dysfunction (LCD), her circulatory status immediately improved. On day 23, however, a mobile 4 9 3-mm mass in the right atrium (Fig. 1A), which was extending into the IVC (Fig. 1b, c), was found on two-dimensional echocardiography. The blood flow was not observed because of complete IVC obstruction by thrombosis (Fig. 1c). Her platelet count decreased from 274 000 (day 22) to 161 000/L (day 23), and D-dimer increased to 29.3 g/mL (day 23).

However, no increase in inflammatory markers was observed. We then diagnosed the mass as a right atrium thrombus that progressed from PICC-related thrombosis of the IVC. After removing the PICC (from day 6 to day 23), recombinant tissue plasminogen activator (r-tPA) treatment was considered. However, the mass gradually disappeared within 2 weeks by only continuous intravenous heparin infusion. The patient was discharged without symptoms after removing the ileostomy. Brain magnetic resonance imaging findings were normal at discharge. At 44 weeks postmenstrual age, the IVC was undetectable and the azygos vein was markedly enlarged on contrast-enhanced computed tomography (Fig. 1d). Coagulation tests, including protein C, protein S, and anti-thrombin III, were normal.