After how many hours without urinating should a diagnostic evaluation of a newborn be undertaken?

A diagnostic evaluation of a newborn should be considered after 48 hours without urination. This timeframe is critical for monitoring a newborn's urinary output as it is an essential indicator of kidney function and hydration status. In the first few days of life, a newborn may have limited urine output; however, by 48 hours, most healthy newborns should exhibit at least some urine production.

The rationale behind this specific timeframe is that a lack of urination beyond 48 hours can potentially indicate underlying issues such as dehydration, renal problems, or other pathologies that require medical attention. Early identification and intervention are crucial in addressing any complications that may arise. This guideline helps ensure that any potential health concerns are addressed promptly to promote the well-being of the newborn.