Upper urinary tract epithelial cancer (UTUC) has an incidence of less than 1 in 100,000 in Western countries, so current guidelines lack large data to support a specific process for UTUC diagnosis. However, when UTUC is diagnosed definitively, it has a higher rate of muscular infiltration than bladder cancer, with a consequent increase in mortality. The tests recommended (grade A) in the EAU guidelines for the diagnosis of UTUC include: urine cytology, cystoscopy and CT urography (CTU). There is a lack of definitive answers as to whether and when ureteroscopy should be performed. Professor Potretzke et al. from the University of Washington School of Medicine conducted a retrospective review and analysis of the literature on the diagnosis of UTUC and concluded that cystoscopy, CTU and urocytology should be the first choice of investigations, whereas ureteroscopy and biopsy are not mandatory. The article was recently published in Urology. The study summarized the indications, advantages, and disadvantages of the various tests based on 33 articles retrieved from Pubmed. First, CTU has a high sensitivity (96%) and specificity (99%) for the diagnosis of UTUC, as demonstrated by a filling defect in the collecting system that is markedly enhanced by the use of contrast, although this may also be seen in certain benign lesions (e.g., chronic inflammation). Ureteroscopy is needed to identify those cases that cannot be accurately identified by CTU. Although invasive, ureteroscopy is valuable in cases that cannot be diagnosed by CTU. At the same time, urologists can also determine whether the cancer has invaded the muscularis propria through microscopy, which is clinically important for the development of subsequent treatment plans. As to whether ureteroscopy causes tumor implantation and metastasis, this issue is still controversial. A study in 2014 showed that no significant difference in patient prognosis was seen with or without ureteroscopy before radical nephroureterectomy (RNU), but if imaging and urine cytology are already highly suggestive of UTUC, there is no need to perform ureteroscopy again. The reason for including cystoscopy in the guidelines is that approximately 17% of patients with UTUC have concurrent bladder cancer, and 22% to 47% of patients with UTUC develop bladder cancer later in the course of the disease, so cystoscopy should be a mandatory part of both the initial diagnosis of patients suspected of having UTUC and during the postoperative follow-up period after UTUC. Urinary cytology, which is also a routine test, has a high specificity (89%-100%) but a low sensitivity, especially in patients with low-grade UTUC, with a false-negative rate of more than 50%. Post-flush exfoliative cytology is generally considered to be more sensitive than exfoliative cytology of naturally excreted urine in UTUC, reaching 74%, but with a specificity of only 50%. Similar to urine cytology, brush testing has a high specificity (94%) but a lower sensitivity (32%). It was also mentioned that if the patient is predicted to have poor residual postoperative renal function after RNU, nephron-sparing surgery (NSS) may be a therapeutic option for low-grade UTUC. In particular, NSS for those with moderately impaired preoperative renal function (i.e., 30 ml/min < eGFR < 60 ml/min) slows the rate of progression to renal failure compared with those undergoing RNU, but those with eGFR < 30 ml/min do not benefit from it. Biopsy is primarily performed preoperatively to clarify tumor grade in patients undergoing NSS, but 15% of patients undergo NSS due to misdiagnosis of low-grade tumors; furthermore, the prognosis of all patients undergoing NSS is less favorable than that of patients undergoing RNU, but the greater postoperative costs (e.g., dialysis) associated with RNU need to be considered in the context of the overall prognosis. The value of ureteroscopy is undeniable when UTUC is suspected but no other disease can be ruled out. If there is sufficient information from CTU and urine cytology to support the diagnosis of UTUC, and the patient has no indication for NSS, there is no need for ureteroscopy. In patients who have a clear diagnosis of UTUC but are being considered for NSS, ureteroscopy may be performed to determine the grade of the tumor and the presence of muscularis propria infiltration for more appropriate clinical decision making.