High resolution computed tomography of Pneumocystis carinii pneumonia in AIDS.

High resolution computed tomography (CT) was performed on 11 homosexual men with the Acquired Immune Deficiency Syndrome (AIDS). All had bronchoscopically proven Pneumocystis carinii pneumonia (PCP). Six patients were re-scanned following treatment and symptomatic recovery. All the scans were abnormal, most showing fine diffuse bilateral alveolar consolidation with bronchial wall thickening, despite having a normal or near-normal chest radiograph in three cases. A variety of unexpected changes such as peripheral consolidation only, upper or lower zone predominance, unilaterality, bronchial dilatation, cystic air spaces and sub-pleural sparing were also seen. Following therapy, resolution of CT changes was shown to be incomplete despite clinical recovery, and whilst all the cases showed a reduction in alveolar consolidation, other findings such as new interstitial shadowing, peripheral predominance, and persistent cystic changes were observed, suggesting the healing process to be complex. Whilst the changes of PCP and its progression following treatment are well described on the plain chest radiograph, this is the first specific documentation of its appearances on narrow section CT, and its response to therapy. The usefulness of high resolution CT scanning to show early infection with PCP in the face of a normal chest radiograph is discussed, and the wide variety of CT changes occurring once the disease is established is emphasized.