Which assessment finding in a neonate shortly after delivery is most concerning?

The assessment finding of ptosis of the right eyelid in a neonate shortly after delivery is particularly concerning because it may indicate a potential neurological or muscular issue, such as Horner's syndrome or a third cranial nerve palsy. Ptosis suggests that there could be an underlying problem with the oculomotor nerve function, which could compromise the eye's ability to open fully. This condition may arise from birth trauma or developmental issues that impact the nerves or muscles of the eye, warranting further investigation to rule out serious complications.

Other options do present with potential clinical significance but are not as immediately alarming. Bilateral rales might indicate fluid in the lungs or transitional respiratory distress, which is often temporary and can resolve with supportive care in neonates. Dullness over the bladder on percussion could suggest urinary retention, which may require monitoring or intervention, but is usually less critical. The presence of a single testicle, or cryptorchidism, is common and usually not linked to acute issues, though it does require follow-up as it could lead to fertility problems later if not addressed.