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Medicine distinguishes between vascular tumours (haemangiomas) and pathological vessel connections (vascular malformations).

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Further information: What are AVMs?

Table 1 shows the differences between hemangiomas and vascular malformations. here are also mixed forms, which makes a standardised approach to such lesions difficult.

Table 1:

Differences between haemangiomas and vascular malformations (from 4)



Vascular malformation

Special characteristics

Exhibits cellular proliferation

Made up of dysplastic vessels


Small or absent at birth

Already present at birth


Rapid growth during early childhood

Growth proportional to the patient’s growth


Involution / resolution during late childhood

No regression / resolution

Vascular malformations are defects in the vessels’ embryonic development and are always present at birth, although they may not necessarily be visible or symptomatic. The malformations can arise from the arterial, capillary, venous or lymphatic vascular system (Table 2). With regard to the fluid velocity in the abnormal vascular connections, vascular malformations are classified into two groups: Malformations with fast blood flow (high-flow) and malformations with slow blood flow (low-flow) (Table 3).

Table 2:

Simplified ISSVA classification of vascular anomalies

Vascular tumour

Vascular malformations







Lymphatico-venous (LVM)


Haemangioendothelioma angioma

Arterial / arterio-venous malformation (AVM)



Table 3:

Classification into high-flow and low-flow malformations according to Burrows & Mulliken 1983 (7)





Connection to the arterial or capillary vascular system

Connection to the venous or lymphatic vascular system


Arterio-venous fistula
Arterio-venous malformation

Venous malformation
Lymphatic malformation
Capillary malformations
Combined types


Trans-arterial embolisation


High-flow malformations have a connection to the arterial or capillary blood vessel system, whereas low-flow malformations have connections to the venous or lymphatic vascular system (Figure 1).


Figure 1:

A An infantile haemangioma is made up of a solid cellular mass (grey) with an organised, glandular (aziniform) arrangement of the supplying arteries (red) and drainage into one or more enlarged (dilated) regional veins (blue).

B An arterio-venous fistula (AV fistula) is a sharply delimited (focal) macrosopic connection between an artery and a usually dilated vein.

C An arterio-venous malformation usually comprises a core (nidus) with arterio-venous connections (shunts) and a network of abnormal vascular channels with supplying arteries and draining veins.

D The venous malformation is a vascular dilatation after the capillary level (post-capillary lesion) made up of abnormally-shaped, dilated venous vascular channels. Larger veins can be incorporated into them.

E A lymphatic malformation is made up of fluid-filled spaces or channels that are surrounded by lymphatic endothelium. These hollow spaces are like rabbit warrens, filled with lymphatic fluid and have no significant flow.

Figure 2:

Angiographic classification of arterio-venous malformations (AVM):

Typ I(arterio-venous fistula): Shunt connection (S) between at least three separate arteries (A) and a single draining vein (V)

Typ II (arteriolo-venous fistula): Shunt connection (S) between multiple arteries (A) and a draining vein (V)

Typ III (arteriolo-venulous fistula): Multiple shunt connections (S) between arterioles (A) and venules (V)

Case examples

Figure 3: Arterio-venous malformation of the 4th toe of the right foot with significant vessel malformation on arterial angiography (left image). Using a thin needle, the hyper-vascular area at the base of the 4th toe (middle image) was pierced and embolisation was performed using gel-like alcohol (Sclerogel). Following sclerotherapy there was a significant reduction in blood supply (right image) and the patient’s symptoms improved.
Figure 4: Pulmonary arterio-venous malformation in which the shunt connection was closed using two vascular plugs inserted via the pulmonary artery.
Figure 5: Combined trans-venous sclerotherapy with high-percentage alcohol gel (Sclerogel) and trans-arterial embolisation with a tissue adhesive (Onyx) in a total of two sessions. Top images: Malformation in the area of the left shoulder with space-occupying effect and pain prior to embolisation. Middle images: Result after the first therapy session with marked reduction in vascularisation. Bottom images: Result after the second session of combined therapy.

If you have any questions about the treatment of vascular malformations, please do not hesitate to contact us. We would be delighted to assist you!


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  • Burrows PE, Mulliken JB, Fellows KE, Strand RD. Childhood hemangiomas and vascular malformations: angiographic differentiation. AJR Am J Roentgenol. 1983;141(3):483-8.