2.3. CT Examination
kidney stone, renal stones
HYDRONEPHROSIS, KIDNEY STONE
All the patients underwent CT examination. The dual CT scanner was used for examination. The patient was in a supine position. Scanning parameters were composed of voltage 120 kV, current 130 mA, slice thickness 7 mm, and interslice distance 10 mm. For enhanced scan, contrast agent Ultravist was intravenously injected, with the specification of 300 mgI/mL, the dose of 1.5–2.0 mL/kg, and the injection rate of 1.5–2.0 mL/s. The scanning mode was the whole abdominal scan, and delayed sweep was made after 0.5 hr.The following general requirements were stated for CT examination in patients with KSD. First, according to the patients' renal condition, the time of urography scan was decided by the radiologist. For patients with no hydronephrosis, it could be appropriately delayed for 15–30 min; for patients who have hydronephrosis, generally, a delay of 1–3 hr was allowed with the upper limit of 6 hr. Second, before the formal examination, the patients should keep an empty stomach, drink water appropriately, and exercise more. Drinking water could dilute the urine and prevent it from crystallizing. Third, the patients could be instructed to hold back the urine properly, so that the bladder was in a full state. When the bladder was in a moderately full state, both kidneys were scanned using a CT machine, and it was observed whether the patient had renal stones with the CT images. Fourth, it should be noted that gastrointestinal angiography should not be performed within 1 week before CT examination in patients with KSD. This was to avoid the interference of barium sulfate chemical reagents on surrounding normal tissues and organs, which might affect the results of kidney stone examination.