Fasting is not required for CT kidney examination. Because eating food will affect the digestive system of the gastrointestinal tract, fasting is required for abdominal CT, but it is not necessary to fast at all for kidney CT. CT of both kidneys is mainly to check the volume and morphological size of the kidneys as well as the presence of stones, occupancy, malformation and other conditions. Kidney CT may have an advantage over renal ultrasound, which may be affected by the pneumoperitoneum and may not be particularly clear to see, while kidney CT can make up for this defect. When doing kidney CT, patients are advised to drink more water, and after the bladder is full, it is more beneficial to observe the CT of kidney and bladder.