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Re: CT Urography: Clarification

Dear Sir/Madam,

We read with great interest the excellent article in the September 2008 issue of the journal by Ulahannan et al entitled “Benefits of CT Urography in patients presenting to the emergency department with suspected ureteric colic”[1]. They employed a test designated a “non-contrast CT Urogram” and concluded that CT is the preferred test of choice for patients over 40 with suspected ureteric colic. We understand the authors aim, methods and fully agree with the conclusion. However we feel the title and nomenclature are incorrect and potentially misleading to practitioners.

Advanced 3D CT can now offer a number of distinct studies of the urinary tract with specific protocols which are designed around various clinical questions (e.g. Routine CT, Urinary Stone CT, Renal CT Angiography (CTA), Dynamic Renal Mass CT and CT Urography (CTU). Much has been written in the literature regarding CTU[2, 3], and there is more than one way to perform this test[4]. There is however one common theme: in a CT Urogram, contrast material must be administered to demonstrate the urothelium-lined tract.

The CT Urography working group of the European Society of Urogenital Radiologists has recently provided very comprehensive and most welcome guidelines on CT Urography[5]. They define a CTU as “a diagnostic examination optimized for imaging the kidney, ureters and bladder. The examination involves the use of multidetector CT with thin-slice imaging, intravenous administration of a contrast medium and imaging in the excretory phase”. ‘Direct’ CTU is performed by administering contrast through nephrostomy, urostomy or bladder catheter. Urinary stone CT performed for detection of renal, ureteric or bladder stones is a non- contrast study and should not be referred to as “non-contrast CT Urography”, as the authors repeatedly do in their article. Most institutions do not give intravenous contrast routinely to patients for investigation of acute ureteric colic.

CT Urography is reserved for those patients in whom it is important to define the urothelial tract with contrast (e.g. investigation of hematuria, urothelial neoplasms, differentiating parapelvic cysts and assessment of ileal diversion). In summary, CT performed for the evaluation of urolithiasis in the setting of acute renal colic is a renal or urinary stone CT and is not a CT Urogram. Labelling it as a CT Urogram is a patient safety issue under current guidelines. If a contrast-enhanced scan is performed instead of a urinary stone CT it is a reportable event as it involves a misadministration of a drug, radiation exposure for the wrong test and a possible needless IV access. While we welcome this paper, we also feel that nomenclature is important for all readers and hope this clarifies any confusion.