As a stone protocol CT detects all renal stones, when is urography necessary in patients with urinary tract stones?
IVU, CTU, and MRU are helpful to show the anatomy of the urinary tract in patients with recurrent stones, in patients in whom stone passage is arrested in the ureter, and in patients in whom surgical intervention is being considered to treat the stones. In such cases, urography helps identify congenital or acquired abnormalities that may be potentiating stone formation, collecting system damage related to chronic stone disease, and ureteral strictures that may prevent spontaneous passage of stones. Stones that are smaller than 5 to 6 mm almost always pass spontaneously, whereas larger stones may require surgical intervention.
Urography may also show abnormalities, such as medullary nephrocalcinosis, that may be contributing to recurrent stone disease.
