Which term describes a 'Crowded pulmonary vessels' indication?

The term that best describes 'crowded pulmonary vessels' is associated with atelectasis. When a portion of the lung collapses, it can lead to diminished air exchange in that part of the lung and cause the surrounding pulmonary vessels to appear crowded on imaging studies. This crowding occurs because the blood vessels are still present but the lung tissue around them is not fully inflated, giving the impression of congestion.

In the context of the other options, acute respiratory distress syndrome (ARDS) or infant respiratory distress syndrome (IRDS) primarily involve inflammation and fluid accumulation in the alveoli, which is distinct from the concept of crowded vessels. A pulmonary embolus can obstruct blood flow, leading to different symptoms such as sudden onset of shortness of breath and chest pain, but does not specifically imply the appearance of crowded vessels. Tuberculosis involves infection that leads to the consolidation of lung tissue rather than a crowded appearance of pulmonary vessels.

Thus, the presence of crowded pulmonary vessels as seen in imaging is characteristic of atelectasis due to the mechanics of lung collapse and resultant vascular changes.