Mieke Bus

41 3 An alternative for 5-ALA instillation is oral administration of the same fluorophore, which has been described in three studies. The first in-human study demonstrated the feasibility on oral 5-ALA in patients with suspicion on UTUC. (19) In two larger studies, more lesions were found in the upper urinary tract compared to stand- ard white light imaging. (20, 21) Although a study on sensitivity and specificity of UUT-PDD revealed an increased sensitivity compared to standard white light endoscopy, this differ- ence was not statistically significant. In summary, PDD enables improved visualization of upper urinary tract tumours. However, major limitations are the administration of 5-ALA and the higher false positive rate due to the tangential viewing angle of the ureteroscopes. Confocal Laser Endomicroscopy Confocal Laser Endomicroscopy (CLE) is an ultra-high resolution microscopy technique that allows imaging of tissue up to a depth of 400µm (Table 1). This imaging depth and Figure 6: Confocal endomicroscopy is based on the suppression of out-of-focus light by the insertion of a pin-hole before the detector. This results in the detection of backscattered light that originates from the focal plane only (red and blue in the overview) while light that is backscattered outside the focal plane (green in the overview) is stopped by the pin-hole. Miniaturization of a confocal microscope affects the numerical aperture (NA) of the system, which will directly influence the resolution of the system. Insert shows ex-vivo CLE of normal proximal ureter from a radical nephrectomy specimen. Normal urothelium showing uniform, monomorphic cells consistent with intermediate cells. (Insert image courtesy of Aristeo Lopez and Joseph Liao, Stanford University)