Interventional Radiology · Vascular malformations and embolisation · Original four-type Cho–Do classification

Cho–Do Angiographic Classification of Arteriovenous Malformations

Angiographic classification of arteriovenous malformations according to shunt and nidus morphology, used to guide the embolisation approach. Although applicable to uterine and pelvic AVMs, it is not a classification of uterine artery origin or branching anatomy.

Purpose

To classify arteriovenous malformations by angiographic shunt architecture and thereby identify the most appropriate component and route for embolisation.

Type	Angioarchitecture	Angiographic hallmark	Embolisation principle
Type I	Arteriovenous fistulae with three or fewer feeding arteries and a single draining vein	Focal direct arteriovenous communication without an intervening nidus	Occlude the fistulous connection, commonly with coils or a vascular plug
Type II	Multiple arterioles shunt into a dominant outflow vein or venous sac	Dilated venous component resembles the nidus on angiography	Target the venous sac or dominant outflow vein; direct-puncture or transvenous access may be more effective than feeder-only embolisation
Type IIIa	Multiple arterioles shunt into multiple venules through numerous non-dilated fistulae	Fine, diffuse, blush-like microshunts	Superselective transarterial nidus-directed embolisation; diffuse microshunts make complete eradication difficult
Type IIIb	Multiple arterioles shunt into multiple venules through enlarged fistulae	Complex vascular network containing visibly dilated high-flow shunts	Transarterial or direct-puncture nidus treatment, often requiring flow control

How to use it

The classification is based on digital subtraction angiographic morphology rather than clinical severity or anatomical location.
Type II is characterised by a dominant venous target; embolising arterial feeders alone may leave the venous nidus and permit recruitment or recurrence.
Type IIIa contains innumerable fine microfistulae and generally has the least favourable embolisation response.
The original classification was developed for body and extremity AVMs; its use in uterine or pelvic AVMs is an extrapolation that can assist procedural planning.

Common mistake

Do not describe this as a classification of uterine artery origin or branching anatomy. It classifies AVM angioarchitecture and is also distinct from the Razavi classification of ovarian artery–uterine artery anastomoses.

Exam pearl

A venous sac or dominant outflow vein indicates Type II and suggests a venous-targeted strategy; a fine diffuse angiographic blush indicates Type IIIa.

Viva questions

What does the Cho–Do classification describe?: It is an angiographic classification of arteriovenous malformations based on the morphology of the fistulae, nidus and venous outflow, with implications for embolisation strategy.
Enumerate the original Cho–Do AVM types.: Type I is arteriovenous fistulous, Type II is arteriolovenous with a dominant venous component, Type IIIa is arteriolovenulous with non-dilated fistulae, and Type IIIb is arteriolovenulous with dilated fistulae.
What is the defining angiographic feature of a Type I AVM?: There are three or fewer feeding arteries communicating through focal fistulae with a single draining vein, without an intervening nidus.
What distinguishes Type II from Type III AVMs?: Type II has multiple arterial feeders converging on a dominant outflow vein or venous sac. Type III has multiple arteriolovenulous fistulae distributed through a vascular network.
How does Type IIIa differ from Type IIIb?: Type IIIa contains numerous non-dilated, fine, blush-like fistulae, whereas Type IIIb contains visibly enlarged fistulous channels within a complex vascular network.
Why is recognising a Type II uterine or pelvic AVM important?: The dominant venous sac or outflow vein is the key therapeutic target. A transvenous or direct-puncture approach may achieve more complete exclusion than embolising multiple arterial feeders alone.
Which Cho–Do type is generally the most difficult to eradicate by embolisation?: Type IIIa, because its innumerable fine microfistulae form a diffuse blush-like nidus that is difficult to penetrate and completely occlude.
What is the common nomenclature trap regarding the Cho classification in uterine embolisation?: The Cho–Do system classifies AVM angioarchitecture, not uterine artery origin or branching anatomy. It should also not be confused with classifications of ovarian artery–uterine artery anastomoses.