Intravenous urography is also known as intravenous pyelopelvic drainage imaging. The method is to inject organic iodine contrast into a vein and then examine the mucosa and internal lumen of the renal papillae, calyces, ureters and bladder under X-ray for stenosis and occupying lesions as well as their morphology and contour. It has reference significance for the diagnosis of renal tuberculosis, chronic pyelopathy, hydrocele, polycystic kidney, urinary tract stone and tumor. Intravenous urography has been used for many years as the main diagnostic tool for patients with low back pain and renal colic, but CT urography has been increasingly used in clinical practice in the past 10 years or so. CTU has the following advantages over IVU: 1. The specificity and sensitivity of CTU is higher than IVU in the diagnosis of ureteral stones. CTU can also detect other non-stone factors causing low back pain such as: exudative abdominal aortic aneurysm; 2. CTU examination does not require the use of contrast agents, which can avoid the appearance of contrast agent adverse reactions (allergic reactions, contrast agent nephropathy, etc.). Although fatal allergic reactions occur only at the level of 1/100,000 when hypotonic contrast agent is used for IVU examination; 3. CTU examination saves time, and images of the kidneys and ureters can be obtained in only a few minutes. In contrast, IVU takes 30 minutes to several hours in diagnosing ureteral stones causing obstruction; 4. The cost of both is comparable.