Imaging of Umbilical Venous Catheter-Related Hepatic Complications in Neonates

Abstract

An umbilical venous catheter (UVC) is commonly placed for central venous access in preterm or critically ill full-term neonates to provide total parenteral nutrition (TPN) and medication. However, UVCs can result in complications, including infection, portal vein thrombosis, and hepatic tissue injury. The inadvertent administration of hypertonic fluid through a malpositioned UVC can also cause hepatic parenchymal damage with mass-like fluid collection that simulates a tumorous condition during imaging. Ultrasonography and radiographic examinations play an essential role in detecting UVC-related complications. This pictorial essay aims to present the imaging findings of UVC-related hepatic complications in neonates.

INTRODUCTION

An umbilical venous catheter (UVC) is commonly placed in preterm or critically ill full-term neonates for central venous access to provide total parenteral nutrition (TPN) and medications. Despite its widespread use and relative safety, a UVC may lead to various complications including infection, portal vein thrombosis and hepatic tissue injury (1,2,3,4,5,6,7). Since a UVC is usually blindly inserted at bedside by pediatricians with a predetermined length, a malpositioned UVC is not uncommon, which increases the risk of hepatic complications (6). Furthermore, when hypertonic fluid is inadvertently administered through a malpositioned UVC, accumulation of such fluid can cause hepatic parenchymal damage. Therefore, properly located UVC tip should be vigilantly monitored on plain radiographs. Early detection of UVC-related hepatic complications such as portal vein thrombosis or extravasation of TPN fluid, forming a mass-like fluid collection called TPNoma, is important to minimize morbidity and mortality by iatrogenic injury. Such hepatic complications can be promptly and accurately diagnosed with ultrasonography (US) without radiation or sedation. In this article, we will review imaging findings of UVC-related hepatic complications in neonates.

NORMAL POSITION OF UVC AND IMAGING MODALITY

A UVC, which starts from the umbilicus and the umbilical vein, travels superiorly in the midline of the abdomen within the anterior portion of the abdominal cavity. After reaching the liver, it passes through the umbilical portion of the left portal vein, ductus venosus and middle or left hepatic vein, finally terminating in the suprahepatic inferior vena cava (IVC) (Fig. 1). Therefore, the UVC travels posteriorly within the liver shadow on a lateral radiograph (Fig. 1C). The ideal location of the UVC tip is at the junction of the right atrium and the IVC, corresponding to the level of the right diaphragm or between T8 and T10 vertebral bodies on a plain radiograph (Fig. 1B) (8,9,10,11). When a UVC is located outside the expected course or shows suboptimal tip location within or below the liver on a radiograph, a malpositioned catheter should be suspected. A UVC can be malpositioned in the portal venous system or within the liver parenchyma at the time of the initial placement. An initially well-positioned catheter can also migrate or withdraw after placement. This may result in complications such as portal vein thrombosis or hepatic parenchymal injury.

Fig. 1. Normal position of the UVC.

A. Diagram of the umbilical and portal venous system in neonates. In the liver, the umbilical vein is joined by the left PV to form the umbilico-portal confluence. It then joins the ductus venosus, which leads to the inferior vena cava via the middle or left hepatic vein.

B. Infantogram shows a properly positioned UVC (yellow dotted line) tip at the level between the T8 and T9 vertebral bodies (white arrow). The tip of the UAC (black arrow) is placed either in the thoracic or abdominal aorta.

C. Lateral view abdominal radiograph of another neonate shows the course of the UVC (white arrow) starting from the umbilical vein, where it travels directly superiorly. It remains in the anterior portion of the abdominal cavity until it reaches the liver. The UAC (black arrow), on the other hand, typically loops inferiorly in the umbilical artery into the internal iliac artery before reaching the aorta. Note that there is free air (asterisk) in the anterior peritoneal cavity, representing pneumoperitoneum caused by perforated necrotizing enterocolitis.

PV = portal vein, UAC = umbilical arterial catheter, UVC = umbilical venous catheter

Interpretating the location of a UVC on a radiograph can be a pitfall when a patient has an altered anatomy due to congenital diaphragmatic hernia and herniation of the liver (12). For these patients, US can be helpful in confirming the location of the UVC tip by tracing its course within the liver. In general, US is used as a primary tool for detecting and monitoring any UVC-related hepatic complications in neonates. A high-frequency linear transducer should be used during US evaluation. Doppler US should also be used when evaluating the vascular system of the liver. In rare occasions, CT scans can be used to evaluate the extent of a hepatic lesion.

UVC-RELATED HEPATIC FLUID COLLECTION (TPNoma)

Infusion of hypertonic fluids including TPN through a malpositioned UVC can cause an endothelial damage, leakage of fluid into the liver parenchyma and tissue necrosis (13), resulting in the formation of a complicated fluid collection in the liver, called a TPNoma. On US, TPNomas can vary in appearance and size depending on the duration of TPN infusion and on the stage of the TPNoma (Figs. 2, 3, 4). While an acute collection appears as a homogeneous hyperechoic mass-like lesion (Fig. 3C), a subacute lesion is seen as a heterogeneous mass with a hyperechoic rim and a hypoechoic center containing cystic areas due to parenchymal necrosis (Fig. 4C, D). Derinkuyu et al. (14) have described three presenting patterns of UVC-related hepatic parenchymal injury, including single nodular echogenic lesion, branching nodular echogenic lesions, and large irregular heterogeneous lesions. Among these, large heterogeneous lesions were the most clinically important, but the least frequent complication of UVC placement. These large heterogeneous lesions may accompany hepatic laceration and perihepatic ascites (14). With time, most TPNomas usually decrease in size spontaneously, evolving into irregular echogenic lesions with calcifications and posterior shadowing (Fig. 2C, D) or resolving completely. However, if TPNomas are complicated by infection, compromised portal circulation or hepatic laceration by the UVC penetrating into the perihepatic space, they can be life-threatening. A surgical or interventional drainage may be necessary. A CT scan may be indicated to evaluate an extensive or complicated TPNoma, which appears as a multi-lobulating or a multi-septated cystic mass with internal fat and/or air between liver lobes and along the ductus venosus (6,14). Without paying attention to the indwelling UVC or to the history of previous UVC placement, TPNoma may be misinterpreted as a hepatic tumor such as a mesenchymal hamartoma (13).

Fig. 2. TPNoma with serial changes according to time in a preterm neonate.

A. Abdominal radiograph on DOL 3 shows the umbilical venous catheter tip (arrow) placed within the hepatic shadow at the level of the T12 vertebral body, which is below the expected position.

B. The initial transverse US image on DOL 5 shows a large multi-septated, complicated fluid collection surrounded by an echogenic wall in the central liver.

C, D. Follow-up US images reveal gradual shrinkage of the complicated fluid collection, leaving calcifications on DOL 7 (C) and DOL 120 (D).

DOL = day of life, TPN = total parenteral nutrition

Fig. 3. Hepatic parenchymal lesion related to a malpositioned UVC in a term neonate with early post-natal closure of the ductus venosus.

A. Radiograph from DOL 0 shows a curved course of the UVC tip (arrow) placed between the level of the T9 and T10 vertebral bodies.

B. Longitudinal US image of the liver on DOL 0 shows obliteration of the ductus venosus (arrowheads) and the UVC tip (arrow) located at the umbilical portion of the left portal vein.

C. Transverse US image of the liver on DOL 0 shows a hyperechoic lesion (arrow) with a lobulated contour in the anterior subcapsular area of segment 2 of the liver caused by infusion of fluid through a malpositioned UVC. Ultrasonography done on DOL 4 after the catheter removal showed spontaneous regression of the lesion. DOL = day of life, UVC = umbilical venous catheter

Fig. 4. TPNoma in a term neonate with a malpositioned UVC.

A, B. Anteroposterior and lateral abdominal radiographs on DOL 0 show the UVC tip (arrows) placed below and anterior to the proper location.

C, D. Longitudinal (C) US image of the liver on DOL 2 shows the UVC (arrow) passing from the umbilical portion of the left portal vein into the liver parenchyma. Longitudinal (C) and transverse (D) US images show a heterogeneous echogenic lesion (arrowheads) with a lobulated contour adjacent to the catheter tip, suggesting complicated fluid collection formed from the infusion of fluid through the catheter.

DOL = day of life, UVC = umbilical venous catheter

PORTAL VEIN THROMBOSIS

Portal vein thrombosis is not an uncommon complication of a UVC placement (15). Although spontaneous resolution has been reported in many cases of non-occlusive, small thrombus formed from a short duration use of a catheter, long-standing or occlusive thrombus in the portal vein can result in significant portal vein obstruction, causing portal hypertension (15). Acute portal vein thrombosis presents as an isoechoic to hypoechoic lesion within a vessel lumen on grayscale US (Fig. 5). On color Doppler US, blood flow is absent in part or in full diameter of the portal vein (16). With time, aged thrombus may show areas of increased echogenicity with calcifications (Fig. 6). Long-standing portal vein thrombosis may result in the formation of collateral veins around the thrombotic segment, leading to cavernous transformation, which appears as serpiginous mixed color sign around the main portal vein on color Doppler US (17). Other features of portal hypertension including splenomegaly and ascites may also be seen (18).

Fig. 5. Portal venous thrombosis in a preterm neonate with a malpositioned UVC.

A, B. Anteroposterior and lateral abdominal radiographs on DOL 0 show a malpositioned UVC (arrows). The UVC tip is placed below, anterior to, and on the left side of the expected ideal location, suggesting its placement within the left hemiliver.

C, D. Transverse grayscale and color Doppler US images on DOL 7 demonstrate iso-to-hypoechogenicity (arrow) in the left portal vein and the absence of blood flow on color Doppler US, suggesting the presence of a thrombus.

DOL = day of life, UVC = umbilical venous catheter

Fig. 6. Portal venous thrombosis in a preterm neonate with a UVC.

A. Longitudinal US image of the liver on DOL 5 shows the UVC (white arrow) passing through the left portal vein and into the ductus venosus. There is a heterogeneous echoic lesion (black arrows) surrounding the catheter, suggesting thrombus formation.

B. Follow-up US image on DOL 14 after catheter removal shows echogenic thrombus (arrows), which extends from the ductus venosus to the left portal vein.

DOL = day of life, UVC = umbilical venous catheter

Fibrin sheath is a thin circumferential proteinaceous coat which forms around the indwelling catheter. It may appear as a tubular structure that simulate a retained catheter after catheter removal (Fig. 7). Fibrin sheath may also be complicated by co-existing thrombi (19).

Fig. 7. Fibrin sheath formation in a preterm neonate with a malpositioned UVC.

A. Anteroposterior radiograph taken on DOL 0 reveals a malpositioned UVC (arrow) in the right portal vein.

B. Transverse US image on DOL 5 after UVC removal shows a catheter-simulating intraluminal tubular lesion (arrow) within the portal vein, suggesting a fibrin sheath formation.

C. Transverse color Doppler US image on DOL 5 shows that the blood flow was maintained within the portal vein.

DOL = day of life, UVC = umbilical venous catheter

EXOGENOUS PORTAL VENOUS GAS

Among many complications of UVC placement, exogenous gas within the portal venous system has been reported to be the most common hepatic complication (14). On US, portal venous gas appears as small echogenic foci with acoustic shadowing or reverberation artifact flowing within the peripheral branches of the portal vein (Fig. 8). It is important to ensure that there are no signs of necrotizing enterocolitis to confirm that it is exogenous gas associated with catheter placement. Exogenous portal venous gas should normally dissolve within a few days after UVC placement, although incautious injection of fluid with air bubbles may result in detection of portal venous gas even after this period (14).

Fig. 8. Exogenous portal venous gas in a preterm neonate with a malpositioned UVC.

A, B. Anteroposterior and lateral abdominal radiographs taken on DOL 21 show a malpositioned UVC (arrows) with the tip placed below and anterior to the expected ideal location.

C, D. Transverse ultrasound images of the liver on DOL 22 show the UVC tip (arrows) positioned in the left portal vein (C) and closing of the ductus venosus (D). Note that there are numerous echogenic foci within the peripheral branches of the portal vein, which suggest portal venous gas due to the injection of medication through the UVC just before the ultrasonography examination.

DOL = day of life, UVC = umbilical venous catheter

CONCLUSION

A UVC commonly used in neonates can lead to various hepatic complications including formation of TPNoma, portal venous thrombosis, and introduction of exogenous portal venous gas. Since plain radiograph and US play a pivotal role in detecting a malpositioned UVC and diagnosing its related hepatic complications, radiologists should be familiar with imaging features of UVC-related hepatic complications and be vigilant in interpretating radiographs of neonates with UVC.