High-resolution computed tomography and pulmonary capillary volume in patients with probable pulmonary Kaposi's sarcoma*

Summary Objective : pulmonary Kaposi's sarcoma (KS) remains difficult to diagnose because of the poor specificity of clinical and radiological signs and the low yield of biopsies. Computed tomography (CT) has been used to describe characteristic aspects of pulmonary KS, and high-resolution CT (HRCT) may be able to depict more precise features. An increase in pulmonary capillary volume has been reported in patients with cutaneous KS. Design and patients : in a prospective study, we determined the specificity of HRCT for pulmonary KS and divided 51 HIV patients into four groups, as follows : 10 asymptomatic patients without KS (control group 1), 14 patients with cutaneous KS (control group 2), 15 patients with mucocutaneous KS (control group 3) and 12 patients with probable pulmonary KS (group 4) documented by HRCT and/or bronchoscopy. Major patterns of probable pulmonary KS i.e spiculated nodules and peribronchovascular thickenings were precisely described. Pulmonary function tests (PFT) were done in every case. Results : total lung capacity (TLC), transfer lung capacity ( DLco ) and its components: pulmonary capillary volume Vc and membrane factor Dm were not different in the 4 groups. Forced expiratory volume for one second over vital capacity (FEV1/VC) was significantly lower in control group 2 and in group 4 than in control groups 1 and 3. DLco was normal in patients with pulmonary KS (group 4); no significant change in Dm (mean = 71.5 ± 17.5 % of predicted values) or Vc (mean = 83.6 ± 14.1 % of predicted values) was observed. Conclusions : these results show that Vc alone is unsuitable for the early diagnosis of pulmonary KS, but that HRCT combined with bronchoscopy can yield findings strongly suggestive of pulmonary KS and obviate the need for more invasive investigations.