Diffusion weighted imaging in the detection of upper urinary tract urothelial tumors

Diffusion-weighted (DW) magnetic resonance imaging (MRI) provides information about the biophysical properties of tissues such as cell organization and density. DW imaging (DWI) is becoming important in the assessment of malignant tumors. The purpose of our study was to evaluate the capability and reliability of DWI in the evaluation of upper urinary tract urothelial tumors.

DWI was performed in seventeen patients with upper urinary tract urothelial tumor, previously diagnosed by either CT or retrograde pyelography. An histological evaluation was performed after surgical resection. Each MRI was carried out using a 1.5T superconductive magnet MRI system. DWI images were obtained with b value of 1000 s/mm(2) under normal breathing. The apparent diffusion coefficient (ADC) values were measured.

In nine patients with renal pelvis tumors and seven patients with ureteral tumors, the lesions were shown as high-signal intensity in the corresponding region on DWI. In one patient with carcinoma in situ (CIS) of the ureter, the lesion was not depicted with DWI. The mean ADC value of the tumor was 1.125 + or - 0.217 x 10(-3) mm(2)/s and was significantly lower than those of the renal parenchyma (1.984 + or - 0.238 x 10(-3) mm(2)/s, p < 0.01) and the urine (2.941 + or - 0.315 x 10(-3) mm(2)/s, p < 0.01).

In our study, the renal pelvic and ureteral tumors except CIS were shown clearly with DWI. Although further studies are required, DWI may take the place of invasive retrograde urography for detecting tumors of the upper urinary tract.