Final answer:
The nurse should assess the patient for atelectasis, which is a common postoperative complication marked by collapsed lung tissue due to inadequate lung expansion. Pneumonia should also be considered, indicated by fever and diminished breath sounds, both of which require immediate medical attention. The option (C) is correct.
Step-by-step explanation:
Given the described symptoms of abdominal pain, a temperature of 100.2, and diminished breath sounds in the left lower base, as well as the client's failure to comply with pre-operative instructions to use the incentive spirometer consistently, the nurse should assess this elderly patient for atelectasis. Atelectasis is a common postoperative complication, especially in patients who are not effectively using a spirometer post-surgery, leading to inadequate lung expansion, mucus accumulation, and potential collapse of part of the lung tissue.
Furthermore, the presence of a fever, along with diminished breath sounds, could also indicate the onset of pneumonia, a serious infection of the lungs. Pneumonia is particularly concerning in elderly patients due to the increased risk it poses to their health. Both atelectasis and pneumonia require prompt medical attention to prevent further complications or deterioration of the patient's condition. Therefore, option (C) is correct.