What are some abnormalities that may be seen on a retrograde pyelogram?
Urothelial tumors are seen as irregular filling defects in the collecting systems and ureters. Large lesions in the collecting system may cause obstruction of the calyces. There is often dilation of the ureter distal to the tumor on a retrograde pyelogram, which is referred to as a “goblet” sign. The ureter distal to a stone is usually small in caliber, and thus dilation of the ureter distal to a filling defect in the ureter is highly suggestive of a urothelial tumor.
Stones can be seen as filling defects in the collecting system, but they can be obscured by dense contrast material, as their radiodensity is similar to that of contrast material.
When a filling defect is seen in the collecting system or ureter, major differential diagnostic considerations include a urothelial tumor, a stone, a blood clot, and inflammatory processes such as ureteritis cystica. The latter process occurs in patients with long-standing presence of ureteral stents, stones, or infection, which can lead to reactive enlargement of submucosal glands in the ureter which then protrude into the lumen and appear as filling defects.
Another abnormality seen in the ureters is ureteral pseudodiverticulosis. Here, there are small erosions in the ureteral mucosa, so that contrast material collects into small protrusions from the lumen. An association has been described between urothelial cancer of the bladder and the development of pseudodiverticulosis, although the etiology for this is not understood.
Ureteral strictures may be due to benign or malignant causes; when mild, they can be nonobstructing, and when more severe, they can cause partial or high-grade obstruction.
Chronic stone disease is one of the most common benign causes although endoscopic procedures such as ureteroscopic stone removal or other interventions can also lead to (iatrogenic) strictures.
Ureteral narrowing due to malignancy can be caused by an intrinsic neoplasm of the ureter, such as a urothelial tumor, or by an extrinsic tumor that encases the ureter, which may be a primary tumor (e.g., cervical carcinoma that encases the pelvic ureter) or metastatic lymphadenopathy. A ureter encased by a malignant tumor is particularly likely to stricture after radiation therapy has been used to treat the tumor.