Risk of portal obstruction in newborns
Article Outline
The portal vein and its branches are particularly susceptible to thrombosis in the neonatal period. The presence of the ductus venosus connecting the umbilical to the hepatic veins means that 60% of the umbilical blood flow bypasses the liver. The ductus venosus is also connected to the left branch of the portal vein. Umbilical vein catheters (UVC) use the ductus venosus pathway to reach the right atrium. Normally, spontaneous closure of the ductus venosus starts at day 1 or 2 of life and ends by day 15 to 20. Its anatomic location explains the complications of local trauma by UVC and the left lobe atrophy after ipsilateral portal vein thrombosis (PVT). Several variations in the intrahepatic branching of the portal venous system have been described, with a frequency of 1 per 1000 of color Doppler ultrasound examinations.1 Some of these variants might make the passage of a catheter more difficult and facilitate the development of thrombosis.
See related article, p 735
Partial or complete obstruction of the portal vein and/or its branches is a frequent cause of portal hypertension in children.2 In almost half of the cases of newly diagnosed portal vein obstruction in children, a history of umbilical venous catheterization is found.2 Other recognized causes of portal vein obstruction include omphalitis, trauma, sepsis, malignancy, and hypercoagulability. In most cases, the portal vein obstruction presents as isolated splenomegaly with or without signs of hypersplenism or as gastrointestinal bleeding.2 One third of children bleed before the age of 3 years; and more than 80% of patients have gastrointestinal bleeding at the pediatric or young adult age.3 Other less frequent complications of this disorder are growth retardation, pulmonary hypertension, hepatopulmonary syndrome, and cholestasis. The latter is the consequence of the compression of the bile ducts by the dilated peribiliary veins forming the portal cavernoma. Doppler ultrasound scanning is a reliable noninvasive technique to assess the portal vein system anatomy1; it can confirm the diagnosis of portal vein obstruction and in some cases aid in the planning of shunt surgery.
Umbilical vein catheterization in newborns can lead to portal vein thrombosis.4 The incidence of this complication after umbilical vein catheterization is not known.4 In some cases, portal vein repermeabilization occurs, and portal flow recovery is observed. However, how and when this occurs needs further study. Some risk factors contributing to the development of portal vein thrombosis and obstruction have been identified. In the neonatal period, placement of an umbilical vein catheterization, sepsis, and local infections or other medical conditions may play major roles.
In this issue of The Journal, Morag et al 5 present a large retrospective study carried out on infants admitted to a tertiary care university hospital during a 5-year period. Patients with an ultrasound diagnosis of portal vein thrombosis were considered for analysis, and those with at least 1 additional ultrasound examination in follow-up were included in the study. The authors recorded gestational age and the history of umbilical vein catheterization placement. The location of the tip was classified as appropriate when it was in the right atrium or the suprahepatic inferior vena cava or inappropriate when in the hepatic, portal, or umbilical veins.
An interesting and original part of this work is the grading of the extent of the thrombus in the portal veins and its comparison with the final outcome. Grade 1 thrombosis was nonocclusive with normal liver parenchyma; grade 2 was occlusive with normal liver parenchyma; and grade 3 was occlusive with abnormal liver parenchyma.
The authors found 133 infants filling the inclusion criteria, representing 3.6 per 1000 admissions to their hospital. This number underestimates the true incidence, because not all infants were screened. Around 70% of infants had an umbilical vein catheterization, and in half of them, it was inappropriately placed. In 60 patients, the thrombosis was of grade 1, in 44 of grade 2, and in 29 of grade 3. Interestingly, no differences in grade of the portal vein thrombosis were observed between infants with or without umbilical vein catheterization. Complete or partial resolution was more frequently observed in infants with grade 1 portal vein thrombosis and inversely, progression to portal hypertension and lobar atrophy (mainly left lobe atrophy) was observed in those with grade 3 thrombi.
These results showed that inappropriate placement of UVC may be associated with a risk of portal vein thrombosis. The ultrasound grading of the thrombi and their consequences on the liver parenchyma were well correlated with the final outcome.
The study reported in this issue confirms previous work in smaller series of patients on the relative safety of UVC when appropriately placed in the newborn at the intensive care unit. We must insist on the need to confirm umbilical vein catheterization tip location and to use this intravenous route for as short a period of time as possible. Indications for ultrasound examination in newborns are not clearly established, and a prospective study would be useful. Such a study could also confirm the value of PVT grading and its potential use to prospectively evaluate anticoagulation or other therapies. Further evaluation is also recommended to assess the importance of other potential risk factors as hypoxemia, sepsis, trauma, or congenital heart malformations. Pediatricians ensuring the long-term follow-up of infants needing neonatal intensive care should specifically consider the possibility of PVT and portal hypertension in their patients.
References
- . Intrahepatic portal venous system (variations demonstrated with duplex and color Doppler US) . Radiology . 1990;177:523–526
- . Portal obstruction in children. I. Clinical investigation and hemorrhage risk . J Pediatr . 1983;103:696–702
- . Risk of gastrointestinal bleeding during adolescence and early adulthood in children with portal vein obstruction . J Pediatr . 2000;136:805–808
- Umbilical venous catheterization and the risk of portal vein thrombosis . J Pediatr . 1997;131:760–762
- Portal vein thrombosis in the neonate (risk factors, course and outcome) . J Pediatr . 2006;148:735–739
PII: S0022-3476(06)00188-0
doi:10.1016/j.jpeds.2006.03.012
© 2006 Elsevier Inc. All rights reserved.
Refers to article:
- Portal vein thrombosis in the neonate: Risk factors, course, and outcome
