Budd Chiari syndrome (BCS), the entity resulting from an obstructed hepatic venous outflow tract,^1,2 is a so-called ultra rare disease³: the estimated incidence was approximately 1 per 2.5 million per year in France or Japan in the 1990s.⁴ This rarity explains why classical randomised trials could not be performed in the past. Trials cannot be foreseen in the near future either, even though excellent collaborations have been developed in European countries, nationwide, and at an international level (see http://www.envie-project.org/origin.html). The report by the Birmingham group⁵ in this issue of Gut should be analysed in the context of the rarity of this disease (see page 878).

The authors retrospectively analysed the outcome of patients with primary BCS treated percutaneously with repermeation (hepatic vein or inferior vena cava angioplasty, with or without stenting) or transjugular intrahepatic portosystemic shunting (TIPS). They included 29 patients referred between 1985 and 1999, and 32 patients referred between 1999 and 2004. This is the largest series of BCS patients treated with interventional radiology in a single Western centre. There are several reports on large series from China^6–8 and India⁹ where, unlike Western countries, there is a large predominance of inferior vena cava occlusion. Inferior vena cava occlusion differs from pure hepatic vein occlusion in many aspects.¹⁰

The authors made considerable efforts to circumvent the usual limitations in treatment evaluation of rare diseases. Firstly, as above mentioned, they included a remarkably large number of cases, given the ultra rarity of the disease. Secondly, although the study focused on a particular treatment modality, all other modalities were available at this referral centre. Thirdly, they stratified the …