Mieke Bus

6 87 Introduction At present, nephroureterectomy is the reference standard for treatment of upper urinary tract urothelial carcinoma (UUT-UC). During the past decade, minimal invasive endoscopic treatments are recognized as a viable treatment option in selected cases with low-grade, non-invasive, UUT-UC and limited tumor volume. (1) The advantage of endoscopic treatment is preservation of kidney function. The choice of treatment depends on accurate visualiza- tion and pre-treatment information on grade and stage of suspected lesions. The contem- porary mainstay in the diagnosis of UUT-UC is based on imaging (CT urography (CT-U)), Ureterorenoscopy (URS), biopsy and urine cytology. CT-U has the highest diagnostic accu- racy for the upper urinary tract with a sensitivity of 0.67-1.0 and specificity of 0.93-0.99. How- ever, its accuracy decreases in case of small lesions whereas flat lesions are not detectable unless they cause a filling defect or ureter thickening. (2) Unfortunately, histology obtained during URS is often inconclusive due to small biopsy samples and crush artefacts and usu- ally no frozen section on biopsy specimen is done because of the limited and small biopsy specimens. (3) If histological diagnosis, grading and staging of UUT-UC is obtained intra-op- eratively, optimal patient selection and immediate decision on endoscopic conservative management might be possible. In addition, Patients who receive a conservative treatment need to undergo a thorough follow up consisting of URS, cytology and imaging regularly according to the guidelines. A minimal invasive endoluminal imaging technique could pos- sible provide an more optimal, less invasive follow up for patients and diminish the amounts of biopsies taken. A technology that provides simultaneous imaging of the ureter with high resolution and depth penetration could give this information. However, all imaging tech- niques suffer from a trade-off between imaging depth and resolution. Several technologies are studied for the upper urinary tract, including optical coherence tomography (OCT) and endoluminal ultrasound (ELUS). Each of these technologies harbours limitations. OCT pro- duces high-resolution cross-section images of the ureter but has a maximal imaging depth of 1-2mm. If tumor thickness transcends this limited imaging depth, tumor invasiveness cannot be assessed. (4) ELUS has an increased imaging depth compared to OCT (table 1), but produces images of a low resolution.