A preterm infant was born at 27 weeks of gestation with intrauterine growth restriction (IUGR), weighing 500 grams. The pregnancy was complicated by maternal hypertension and placental insufficiency, confirmed by Doppler ultrasound showing reversal of end-diastolic flow and by pathological examination of the placenta. At birth, the infant required intubation and surfactant administration for respiratory distress syndrome. Umbilical lines were placed for vascular access and parenteral nutrition, which were later transitioned to a peripherally inserted central catheter (PICC). 

At approximately one month of life, in the context of clinical instability, persistent thrombocytopenia, and failure to clear a bacteremia, an echocardiogram was performed. It revealed a large thrombus extending from the inferior vena cava (IVC) into the right atrium, with intermittent protrusion into the tricuspid valve. The thrombus had both a fixed and a mobile component. Anticoagulation with low molecular weight heparin (enoxaparin) was initiated. Serial echocardiograms were performed to monitor the thrombus. Over time, the mobile component was no longer visualized, raising concerns for either thrombus resolution or embolization, potentially resulting in a silent pulmonary embolism. 

Ascites was initially detected on abdominal ultrasound at one month of age. The infant progressively developed hepatomegaly and splenomegaly. As abdominal distension worsened, paracenteses were performed to decompress the abdomen. At the time, the infant was nil per os. Analysis of the peritoneal fluid were non-conclusive, and culture results were negative. Despite drainage, ascites reaccumulated rapidly. Multiple subsequent paracenteses were performed, with fluid analysis consistently within normal limits. The combination of rapid reaccumulation and inconclusive findings supported a diagnosis of portal hypertension. 

Due to persistent and worsening ascites and concerns for venous obstruction, a cardiac catheterization was performed at three months of life. The procedure demonstrated severely elevated pressure in the IVC and a subtotal occlusion at the junction of the IVC and right atrium. The infant underwent successful balloon angioplasty and stent placement via both femoral and jugular venous access. A guidewire was advanced from the IVC into the right atrium, and angiography confirmed subtotal obstruction at the infra-atrial IVC. Following balloon dilation, a stent was deployed, resulting in excellent angiographic resolution and disappearance of previously noted venous collaterals. The patient was maintained on enoxaparin for several months post-procedure, then transitioned to low-dose acetylsalicylic acid for stent patency. 

Of note, on angiography, no evidence of pulmonary embolism was seen. The cath-based evaluation confirmed portal hypertension as the likely etiology of the ascites. Following the intervention, there was a marked reduction in ascites and abdominal girth. The infant's abdomen became softer and more compliant on examination. Follow-up abdominal ultrasounds demonstrated good stent patency with unobstructed flow in both the IVC and hepatic veins. This case highlights a rare presentation of neonatal IVC thrombosis complicated by portal hypertension and significant ascites, ultimately managed through successful endovascular intervention.

Parasternal Long Axis View

Parasternal Short Axis View

Apical View

Subcostal Views

Ascites may be seen in some of the views, as well as proximal IVC dilatation (and sub-hepatic venous dilatation) before the IVC-RA junction.

Catheterization

Here we can appreciate that the IVC is significantly stenose with limited flow to the RA. 

Balloon dilatation allowed for some improved flow in the IVC-RA junction

Stent placement allowed for complete resolution of the IVC-RA stenosis