Computed tomography urography

A Computed tomography urography (CT urography or CT urogram) is a computed tomography scan that examines the urinary tract after contrast dye is injected into a vein.[1]

CT urogram
SpecialtyRadiology

In a CT urogram, the contrast agent is through a cannula into a vein, allowed to be cleared by the kidneys and excreted through the urinary tract as part of the urine.[1]

Uses

A CT urogram is used to look for problems relating to the urinary tract, usually to investigate a symptom such as blood in the urine.[2] These may include blockages or narrowing, such as due to kidney stones, cancer, and anatomical abnormalities.[2] It may also be used to investigate whether a cancer is present,[3] or to monitor whether a tumour is responding to treatment.[3][4]

Procedure
FIGURE 8. Selected images from a CT Urography protocol CT. 8a is an axial CT image from the renal parenchymal phase. There is a mildly enhancing soft tissue mass in the left renal pelvis (arrow) consistent with a transitional cell carcinoma. Figure 8b (coronal reformats) and 8c (left oblique coronal reformats) demonstrate the double bolus technique of CT Urography. These images confirm soft tissue mass (arrows) in the renal pelvis with contrast excretion into the collecting system (arrowheads).

CT urography (CTU) is commonly used in the evaluation of hematuria, and specifically tailored to image the renal collecting system, ureters and bladder in addition to the renal parenchyma.

Before the procedure, a person is often asked about things that might put them at risk - for example pregnancy or an allergy to contrast.[2][3] They are asked to drink water, and not to urinate, so that the bladder is full.[2][3] Metal objects such as earrings, which might produce artefact on the image, are removed.[3] An intravenous cannula is inserted and contrast dye is injected through this during the scan.[2] The scan involves a person lying down on a table that is put through a CT Scanner.[2]

The CT scan will image the urinary tract, including the kidney, ureters, bladder, and urethra.[3] It does this by taking many cross-sectional images that can be computationally arranged so as to provide 3D information.[3] The scan itself usually involves a CT scan without contrast (a non-contrast phase), a CT scan while the contrast is within the kidneys (a parencyhmal phase), and a CT scan taken while the contrast travels through the renal tract (an excretory phase).[4]

Risks

A person may have an allergy to the contrast dye. When this occurs, it is usually mild, causing symptoms such as an itch or a rash,[2] however rarely causes a serious reaction such as anaphylaxis that may impair breathing.[3] The contrast dye may not all go inside the vein at the cannula site, and if it extravasates, it may cause pain or bruising to the local area.[3] The scan involves radiation, which may increase the risk of future cancers by a very small amount,[3] or prove damaging to a pregnancy.[3] Additionally, the dye used can damage kidney function.[3]

References
  1. Radiology (ACR), Radiological Society of North America (RSNA) and American College of. "Urography". www.radiologyinfo.org. Retrieved 4 July 2020.
  2. "Computerized tomography (CT) urogram - Mayo Clinic". www.mayoclinic.org. Retrieved 2020-07-04.
  3. "CT urogram | Bladder cancer | Cancer Research UK". www.cancerresearchuk.org. Retrieved 2020-07-04.
  4. Noorbakhsh, Abraham; Aganovic, Lejla; Vahdat, Noushin; Fazeli, Soudabeh; Chung, Romy; Cassidy, Fiona (December 2019). "What a difference a delay makes! CT urogram: a pictorial essay". Abdominal Radiology. 44 (12): 3919–3934. doi:10.1007/s00261-019-02086-0. ISSN 2366-004X.
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