Discussion
Abernethy malformation is a congenital portal vein malformation caused
by abnormal selective preservation and degeneration of the
peri-intestinal yolk vein plexus during the formation of the portal vein
system during the embryonic period1. The disease is
rare, affecting an estimated 1/30000 live births7,9.
Various degrees of preservation and degeneration lead to diverse
vascular variations2. In 1994, Morgan et al. divided
Abernethy malformation into two types: Type I, characterized by
intrahepatic portal vein complete loss and complete side-to-side shunt;
and Type II, characterized by the presence of intrahepatic portal vein
and partial side-to-side shunt10. Depending on the
confluence of the superior mesenteric vein and the splenic vein, Type 1
Abernethy malformation can be subsided into two types. Type 1 is more
common than Type 28. In our case, the intrahepatic
vein was present, and there was an extensive shunt between the hepatic
portal vein and the inferior vena cava. Type II Abernethy malformation
was identified.
The clinical manifestations of Abernethy deformity differ depending on
the location of the abnormal shunt vessels and combined malformations,
which are divided into three classes11: (1) abnormal
liver function, liver fatty change, and severe cases such as a
regenerative nodule or tumor formation caused by insufficient liver
bloody supply11; (2) symptoms related to shunt,
including hyperammonemia, hypergalactosemia, hepatic encephalopathy,
liver lung syndrome, pulmonary hypertension, heart failure, and
gastrointestinal bleeding12,13; (3) symptoms
associated with coexisting congenital abnormalities such as congenital
heart disease7. Zhang et al. reported 12 children with
Abernethy malformation, nine of whom presented with hematochezia, and
all had abnormally thick inferior mesenteric vein entering the inferior
vena cava through the iliac vein in the pelvic
cavity5. Other less
common symptoms include abnormal liver transaminase, jaundice, and
hypoxemia5. Abnormal laboratory tests are usually
caused by untreated portal vein blood entering the vena cava system and
include elevated serum ammonia and bile acids. Patients with Abernethy
malformation and congenital heart diseases may initially present with
symptoms related to cardiac dysfunction7. In the
present case, total bile acids and total bilirubin decreased
significantly after portal shunt ligation.
Abernethy’s deformity is rare but often associated with other
malformations. Congenital heart disease is one of the most common
associated malformations. Mistinova et al. reviewed 84 cases with
congenital absence of the portal vein and found that 65% were female,
and 22% had heart disease1. Christiane et al.
reviewed the characteristics of 316 patients with a congenital
portosystemic shunt in the literature and found that the percentage of
patients associated with heart disease was also 22%4.
Patients with cardiac disease are more common in Type 1 than Type 2
(68% vs. 32%)4. The most common type is a
ventricular septal defect, followed by atrial septal defect, patent
ductus arteriosus, atrioventricular septal defect, and
coarctation4. In the present case, we reported a
patient with Type 2 Abernethy malformation and MAPCAs, which is not
found in the literature. Congenital MAPCAs can
be
associated with or without heart defects. Those with heart defects tend
to have cyanotic defects. MAPCAS without cyanotic congenital heart
defects are rare and are associated with premature birth, lung tissue
infection, and pulmonary dysplasia14. Our patient was
born at term and had no other heart defects. In another study, the
authors found that 27.4% of patients with congenital portosystemic
shunts had cardiac disease7.
The
co-existence of Abernethy malformation and cardiac raises the suspicion
that these two diseases might be related. Some authors suggested that
abnormal hemodynamics might cause the abnormal persistence of an
embryonic vitelline vein1, while other authors held
that portosystemic shunts might cause a “congestive effect” and the
heart defects would result from adaptive change15. In
some cases with multiple cardiovascular diseases, angiogenesis might
play a more critical role16. Nevertheless, there is no
definitive explanation for the relationship between these diseases;
further research is needed.
In addition to cardiovascular anomalies, other deformities may be
associated with Abernethy malformation. A small number of patients are
affected by Turner syndrome, Caroli syndrome, Goldenhar syndrome, and
Down syndrome8. The child in our case was incidentally
found to have Dandy-Walker syndrome (revealed by a head CT performed
after a traumatic brain injury). Before that time, no neurological
abnormalities were found. Other deformities may be found in the urinary
and male genital tract, the spleen, brain, and skeletal
system1. More than 40% of patients with Abernethy
malformation may have hepatic lesions such as focal nodular hyperplasia,
adenoma, hepatocellular carcinoma, and cirrhosis1,8.
The relationship between these two diseases might involve absent or
decreased portal vein flow and the contemporaneous increased supply of
the hepatic artery8. There was no hepatic lesion in
our case before surgery and during follow-up. However, the follow-up was
relatively short, and additional attention should be paid to hepatic
lesions in the future.