The results of a V/Q scan show poor perfusion with adequate ventilation. A chest radiograph shows a wedge-shaped infiltrate over the right lung field. The patient most likely has:

The scenario described indicates a mismatch between ventilation and perfusion, specifically poor perfusion with adequate ventilation evidenced by the V/Q scan results. The presence of a wedge-shaped infiltrate on the chest radiograph strongly suggests the pattern associated with a pulmonary embolism. This occurs because, in cases of pulmonary embolism, an obstruction (such as a clot) prevents blood flow to a segment of the lung, leading to decreased perfusion. Meanwhile, ventilation remains intact in the unaffected areas, creating a V/Q mismatch.

The wedge-shaped infiltrate can be due to the ischemic changes resulting from the impaired blood flow into the lung segment affected by the embolism. This pattern is characteristic and leads to the classic presentation observed in imaging studies.

In contrast, while other conditions like pneumonia and ARDS may also show similar infiltrates or changes on imaging, they typically present with associated perfusion issues differently. For example, pneumonia usually presents with both ventilation and perfusion changes in the affected area due to consolidation and inflammation, and ARDS shows widespread alveolar damage affecting ventilation and perfusion ratios throughout both lungs, rather than localized changes indicated by the V/Q scan. Fluid overload might lead to bilateral opacities rather than a wedge-shaped infiltrate. Therefore, the