CT urography

Author: Mikael Häggström

Planning

Indication for CT urography in hematuria

Most patients with macroscopic hematuria, especially when over 50 years, should undergo both cystoscopy and CT urography.

Microscopic hematuria indicates further workup with cystoscopy and/or CT urography if there are significant underlying risk factors, mainly:

• Male sex
• Age, especially being older than 60 years
• Smoking
• Pelvic radiation

Configuration

In Swedish practice, the protocol is determined by age:

• In patients under 40 years:

1. Low-radiation-dose of urinary system, without IV contrast
2. Normal-radiation-dose with split bolus IV contrast, 7.5 minutes and 90 seconds before image acquisition.

• In patients over 40 years:

1. Low-radiation-dose of whole abdomen, without IV contrast
2. Normal-radiation-dose of whole abdomen 20 seconds after bolus tracking, for visualization of renal cortex.
3. Normal-radiation-dose of upper abdomen 40 seconds after the previous, for visualization of all renal parenchyma.
4. Normal-radiation-dose of urinary system 7.5 minutes after IV contrast, for renal pelvises and ureters.

Regardless of age, 1 liter water is given orally 1 hours before the CT, as well as avoiding urination during 1 hour before, in order to increase renal filtration and distend the bladder. If the images show insufficient contrast filling in the renal pelvices and ureters, an additional image is taken after 5 minutes, possibly with the patient lying on the stomach to make gravity help fill the ureters.

Evaluation

• CT without contrast: Look for kidneys stones. If found, see CT of kidney stone disease.
• CTs with contrast: Tumors within the kidney, ureters or bladder.

• Signs of bladder tumor:

• Bladder wall thickening, especially when nodular or irregular. However, the anterior wall is frequently thickened in a normal underdistended bladder. Also, diffuse bladder wall thickening rarely represents malignancy. Look both at images 40 seconds after IV contrast and with contrast-containing bladder lumen, since that contrast may both demarcate a tumor as well as obscure one by beam-hardening artifacts.

• Lymph nodes. Enlarged lymph nodes may be metastases. Generalized lymphadenopathy may indicate lymphoma, and in such cases tumors in the urinary system may be lymphomas as well.

Further evaluation of suspected tumors

Nodular bladder tumor.

• Evaluate contrast enhancement by comparing images before and after IV contrast. Any focal hyperenhancement of the bladder wall must be considered suspicious for malignancy. For transitional cell cancers, the most common form of bladder cancer, enhancement peaks at about 100 HU at approximately 60 seconds, and then decreasing slowly. In lack of enhancement, consider a differential diagnosis of a hematoma, although the presence of an underlying tumor is still difficult to exclude.
• Measure size
• For bladder tumors:

• Classify shape such as for example nodular or polypoid. In case of well circumscribed and smoothly marginated borders, consider bladder leiomyoma as a differential diagnosis.
• Note any calcification of the bladder wall, indicates cystoscopy, particularly when there is bladder wall thickening.
• Signs of local spread or metastasis. The most commons sites of metastasis of bladder cancers are lymph nodes, bones, lungs, liver and peritoneum.