ARRS 2022 Abstracts

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E1368. Go With the Flow: Pathology and Pitfalls of Upper Tract Collecting System by CT Urogram
Authors
  1. Luyao Shen; Stanford University College of Medicine
  2. Justin Tse; Stanford University College of Medicine
  3. Kristen Bird; Stanford University College of Medicine
  4. Edwina Chang; Santa Clara Valley Medical Center
Background
A CT urogram (CTU) is part of the daily life of an abdominal radiologist. However, the vast majority of CTUs demonstrate a normal intrarenal collecting system and ureters. Many fellows and residents go through training without seeing a wide range of pathologies on CTU. Therefore, this proposed work presents a great opportunity for residents, fellows, and junior attendings to review and learn different pathologies of the intrarenal collecting system and ureters. We will also present some pitfalls and how to avoid them when interpreting CTU.

Educational Goals / Teaching Points
CTU helps to diagnose pathology related to the intrarenal collecting system and ureter, but it needs to be properly protocoled. Knowing the anatomy of the intrarenal collecting system is crucial to identity pathology. Participants will learn different pathologies related to contour abnormality and filling defects and become aware of pitfalls such as using the wrong window and overcalling pathologies that are related to contrast mixing or incomplete opacification of the collecting system and peristalsis.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
We will start with a general introduction of CTU, indication, and protocol. We will then learn the anatomy of the intrarenal collecting system and the ureters on a normal study. Then we will talk about variant anatomy: compound calyx, aberrant papilla, and duplicated collecting system. Next, we will show abnormal cases related to contour abnormalities: calyceal diverticulum, renal tubular ectasia/medullary sponge kidney, papillary necrosis, calyceal rupture, extrinsic compression from parapelvic cysts and crossing vessels, urinary tuberculosis, ureterocele, ureteral diverticulum, and strictures. Then we will learn pathologies related to filling defects: transitional cell carcinoma (TCC), fibroepithelial polyp, inverted papilloma, blood/suburothelial hemorrhage, pus, stone, and ureteritis cystica. Last, we will go over some pitfalls and tricks to help improve diagnostic skills. Cases of pitfalls include: prominent pyramids can mimic filling defects; layering contrast in an incompletely opacified collecting system can mimic filling defects; wrong windowing can overlook pathology; and a tortuous ureter with focal peristalsis can mimic a stricture.

Conclusion
CTU is frequently performed for microscopic hematuria. When there is a positive finding, it is important to accurately diagnose the pathology and recommend the appropriate follow-up. This exhibit teaches the normal and variant anatomy of the upper tract collecting system. This exhibit also showcases a variety of pathology related to contour abnormalities and filling defects. It is important for us to learn and avoid potential pitfalls when interpreting a CTU.