A 35-year-old man arrives at the ED with pain in the right flank that began 2 hours ago, spontaneously abated, and then suddenly recurred. The pain is severe, sharp, and radiates to the groin. Physical examination reveals tenderness in the right costovertebral angle. The patient’s pulse rate is 110 beats/minute, blood pressure 150/94 mmHg, temperature 100o F (37.8oC), and respiratory rate 24 breaths/minute. Laboratory results indicate a WBC count of 10,000/mm3 , normal hemoglobin and hematocrit levels, and normal serum electrolyte, BUN, and glucose levels. Urinalysis reveals an RBC count greater than 100 cells via high-powered field. An indwelling urinary catheter is inserted, and 800 mL of urine is obtained. The patient is sent for an emergency IVP. The nurse knows that management of a patient with obstructive uropathy is directed primarily toward: