Final answer:
A postvoid residual (PVR) volume of 40 mL is considered normal and the nurse should document this as a normal finding without the need for further immediate action.
Step-by-step explanation:
After catheterization, if a nurse obtains 40 mL of urine to measure the postvoid residual (PVR), the appropriate next step would be to document this normal finding for postvoid residual. A PVR of 40 mL indicates that the bladder has emptied effectively, as a normal PVR is typically less than 50 mL. In cases where the PVR is high, it could suggest incomplete bladder emptying, which might be due to various conditions such as medication interference, prostate issues, or kidney stones. However, since 40 mL is within the normal range, there is no need for concern regarding this particular measurement, and the nurse should simply document the result.