Classification and ultrasound findings of vascular anomalies in pediatric age: the essential

Capillary malformation
This category includes various forms of lesions, some com-
mon and others very rare. In general, being very superficial, 
clinically they do not present many problems with the excep-
tion of esthetic implications. However, their importance 
lies in the fact that they can often be associated with other 
diseases, including, for example, Sturge–Weber syndrome, 
Parkers–Weber syndrome, or to forms of overgrowth [
40
, 
41
].
With normal ultrasound probes, the capillary malforma-
tion is not visible in a direct way but only as a nonspecific 
thickening of the skin and subcutaneous tissue compared 
with the contralateral healthy side. Only with dedicated 
dermatological probes of 20 MHz is it possible to detect an 
increase in vascularization [
40
, 
42
, 
43
].
Venous malformation
Venous malformations are the most frequent form of vas-
cular malformations with a prevalence of about 1% [
44
, 
45
]. Their presentation may be varied; they may appear as 
a group of ectatic and dysplastic superficial veins or, more 
frequently, be deeper and appear as a real mass in soft tis-
sues with a bluish appearance of the superficial skin [
1
, 
39
]. 
These masses are always soft and compressible (Fig. 
12
). 
Only in rare cases can they increase in consistency due to 
the formation of internal clots. Like all vascular malforma-
tions, they can rapidly grow and become symptomatic with 
puberty or pregnancy.
Sonographically, venous malformations appear as 
well-margined masses with a “spongiform” heterogene-
ous echostructure (hypoechoic venous spaces separated by 
hyperechoic septa), which is hypoechoic in comparison to 
the surrounding tissues. Isoechoic or hyperechogenic echo-
structure can rarely occur [
14
, 
46
]. The mass is always well 
compressible. Sometimes it is possible to identify anechoic 
tubular structures that are recognized as vascular channels 
[
47
]. Certainly the ultrasound aspect is nonspecific, and it is 
often not possible to make a differential diagnosis. However, 
it is a pathognomonic sign that, in addition to the exploration 
in B-mode, aids in the diagnosis of venous malformation: the 
presence of a 
phlebolith
(i.e., an intralesional calcification). 
The presence of phleboliths is extremely rare in the other 
masses of soft tissues in the pediatric age. Unfortunately, 
this sign is not frequent in venous malformations being pre-
sent, depending on the various series, from 9 to 16% of cases 
[
14
, 
46
] (Fig. 
13
).
In the color Doppler examination, venous malforma-
tions are slow flow lesions. Vascular density is very low. 
Veins show low-velocity flow with non-modulated spectrum 
(Fig. 
14
). Sometimes the flows are so slow that they are not 
identifiable [
46
]. In this case, a light compression on the 
lesion may be useful to reduce the caliber of the vessels and 
try to increase the velocity of the intravascular flow [
34
]. 
The absence of vascularization may also be due to extensive 
thrombosis of the vessels involved which must therefore be 
recognized [
39
]. Venous malformations can often occur near 
the joints. In this case, it is necessary to identify whether