Final answer:
The appropriate nursing diagnosis for a patient suffering from an inability to have a bowel movement after taking narcotic pain medication for four days is Constipation related to opioid use, which is a common side effect of the medication.
Step-by-step explanation:
The appropriate nursing diagnosis for a patient who has been unable to have a bowel movement for four days after taking prescribed narcotic pain medication is Constipation related to opioid use. Narcotic pain medication, also known as opioids, can slow down the movement of the digestive tract leading to constipation. This is a well-recognized side effect. The nurse should assess the patient for any signs of abdominal pain, distention, or bowel sounds, and provide interventions such as increasing fiber intake, fluid intake, and encouraging mobility, if appropriate. Additionally, the nurse might coordinate with the healthcare provider to consider laxatives or stool softeners to alleviate the patient's symptoms.