Split bolus technique
The split bolus technique is a CT imaging investigation used in patients with haematuria aiming to put together, in a single image acquisition, both the nephrographic and renal excretory phases and thus reducing the radiation dose of the study. It is a CT protocol adopted for some institutions for assessing a patient with haematuria 1-2.
Usually, a prior unenhanced study of the abdomen and pelvis in the form of a CT-KUB has been performed or undertaken before the split bolus component, excluding nephrolithiasis as the cause of the haematuria. Then, the patient receives 50 ml of IV contrast followed by an additional 50 ml eight minutes later. Images are then acquired 55 seconds following the second dose of IV contrast. This provides contrast imaging of the kidneys to look for a renal mass, such as renal cell carcinoma along with a CT-IVU, allowing for the detection of upper tract disease, such as transitional cell carcinoma. Bladder images are acquired which are insightful, but this should not be a substitute for cystoscopic assessment.
The technique has been shown to have a high sensitivity, specificity and accuracy for detecting upper tract tumours 3 .
- 1. O'Connor OJ, McSweeney SE, Maher MM. Imaging of hematuria. Radiol. Clin. North Am. 2008;46 (1): 113-32, vii. doi:10.1016/j.rcl.2008.01.007 - Pubmed citation
- 2. Chow LC, Kwan SW, Olcott EW et-al. Split-bolus MDCT urography with synchronous nephrographic and excretory phase enhancement. AJR Am J Roentgenol. 2007;189 (2): 314-22. AJR Am J Roentgenol (full text) - doi:10.2214/AJR.07.2288 - Pubmed citation
- 3. 3. Maheshwari E, O'Malley ME, Ghai S et-al. Split-bolus MDCT urography: Upper tract opacification and performance for upper tract tumors in patients with hematuria. AJR Am J Roentgenol. 2010;194 (2): 453-8. AJR Am J Roentgenol (full text) - doi:10.2214/AJR.09.3228 - Pubmed citation