Purpose: The fast helical CT technique allows examination of the kidneys du
ring different phases of contrast medium enhancement. However, every additi
onal phase increases the radiation dosage to the patients. We investigated
the detection rate and characterisation of renal lesions during different p
hases and evaluated them separately, and considered the possibility of excl
uding phases without loss of important information.
Material and Methods: Sixty patients who underwent contrast-enhanced multip
hasic renal helical CT examination were included. Every CT phase was evalua
ted separately The number of lesions and the characteristics of the lesions
were noted and all lesions were viewed together.
Results. A total of 153 cysts and 17 solid lesions were detected. The large
st and an equal number of cysts (142/143) was detected in the nephrographic
and excretory phases. However, the nephrographic phase detected more corti
cal cysts and the excretory phase detected more sinus cysts. All solid lesi
ons were detected in all phases. Renal parenchymal tumours were best charac
terised in the cortical phase and angiomyolipomas in the native phase.
Conclusion: The cortical phase was best for characterisation of renal paren
chymal tumours. The nephrographic and excretory phases were best in detecti
ng and characterising renal cysts. The nephrographic phase was the phase gi
ving the least diagnostic information.