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Comparison of Quality of Urinary Bladder Filling in CT Urography with Different Doses of Furosemide in the Work-up of Patients with Macroscopic Hematuria - Beyond the Abstract 

Malignancy in the urinary tract has followed a standardized care pathway in Sweden since 2015, meaning that symptoms raising suspicion of malignancy must be quickly assessed. The symptoms are defined as patients older than 50 years with at least one episode of macroscopic hematuria or patients with a suspicious finding during another investigation.1 CT urography (CTU) is important in the work-up of these patients as it can detect malignancy in the upper and lower urinary tract. The protocol for preparation of CTU at Uppsala University Hospital was changed in 2013 to improve the quality of urinary bladder filling,2 since the bladder is best examined when adequately full.3 Changes were the addition of a furosemide injection at the beginning of the examination, emptying of the bladder after the corticomedullary phase (CMP), and obtaining the excretory phase (EP) after a 30-minute delay.2 An earlier study concluded 10 mg furosemide provides discomfort in patients with the urge to void and increased diuresis several hours after the examination,4 why 5 mg furosemide is used today. To reduce the risk of patient discomfort, could the dose be lowered even more without compromising on the quality of urinary bladder filling?

215 patients undergoing elective CTU due to macroscopic hematuria were administered either 5, 2.5, or 0 mg furosemide. The control group of 15 patients given 0 mg was considered too small to draw any conclusions. The results were focused on bladder volume, bladder distension, and attenuation of bladder content in CMP and EP. The effect of furosemide comes approximately 10 minutes after administration according to the manufacturer, hence should only affect the results in EP. 5 mg provided a larger average bladder volume in EP with 370±224 ml (28-1052), compared to 274±120 ml (43-628) after 2.5 mg (p<0.001). Satisfactory distension was defined as primarily convex bladder walls in both axial and coronary planes. The ratio was 85% after 5 mg and 80% after 2.5 mg. To reduce the risk of hiding tumors by the contrast blooming effect,5 a low difference of attenuation between contrast-enhanced urine and bladder tumors (which is around 57 HU in EP)6 is desirable. The closest attenuation was reached after 5 mg with 266±89 HU (103-524), compared to 362±156 HU (118-948) after 2.5 mg (p<0.001).

In conclusion, 5 mg furosemide is preferred rather than 2.5 mg since the higher dose resulted in larger bladder volume and a more suitable attenuation of the bladder content. There was no difference between the doses concerning rate of satisfactory bladder distension. However, to find the most optimal furosemide dose, both the quality of bladder filling and patients’ experiences are important. Further research assessing patients’ experiences with these furosemide doses is welcome.

Written by: Adina Ljungberg,1 Monica Segelsjö,1 Pär Dahlman,1 Malin Helenius,1 Mats Magnusson,2  Anders Magnusson1

  1. Uppsala University Section of Radiology, Department of Surgical Sciences, Uppsala Sweden.
  2. Pharmetheus AB, Uppsala Sweden
References: 

  1. Regionala cancercentrum i samverkan [Regional Cancer Centers in Collaboration]. Cancer i urinblåsan och övre urinvägarna: standardiserat vårdförlopp [Cancer in the urinary bladder and the upper urinary tract: standardised care pathway]. 2018. Available at: https://www.cancercentrum.se/globalassets/cancerdiagnoser/urinvagar/urinblase--och-urinrorscancer/vardforlopp/svf-cancer-urinblasa-ovre-urinvagarna.pdf (accessed 30 May 2018).
  2. Uppsala University Hospital. Metodbok CT urinvägar, hematuri [Book of Procedure of CT urinary tracts, hematuria], version 0.9. 2017.
  3. Pettersson H. The Nicer Global Textbook of Radiology II Chest, Abdomen, Urogenital system, Tropical disease. Lund Sweden: The NICER institute, 1995:1126.
  4. Helenius M, Segelsjö M, Dahlman P, et al. Comparison of four different preparation protocols to achieve bladder distension in patients with gross haematuria undergoing CT urography. Radiography 2012;18:206-211.
  5. Grimes J, Duan X, Yu L, et al. The influence of focal spot blooming on high-contrast spatial resolution in CT imaging. Med Phys 2015;42:6011-6020.
  6. Helenius M, Dahlman P, Magnusson M, et al. Contrast enhancement in bladder tumors examined with CT urography using traditional scan phases. Acta Radiol 2014;55:1129-1136.
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