Upper Urinary Tract and Renal Pelvis Cytology
Cytology of the upper urinary tract — the ureters and renal pelvis — is used to evaluate suspected upper-tract urothelial carcinoma, a less common but clinically important disease. Specimens are obtained by selective catheterisation, washing, or ureteroscopic brushing, and their interpretation must account for instrumentation-induced changes that can mimic malignancy.
Definition
Upper urinary tract cytology is the cytologic evaluation of cells obtained from the ureters and renal pelvis — by selective washing, catheterisation, or ureteroscopic brushing — chiefly to detect urothelial carcinoma of the upper tract.
Scope
This entry covers upper-tract specimen types and how they differ from bladder samples, the application of standardised reporting to upper-tract cytology, the diagnostic challenge of instrumentation artefact, and the role of cytology in evaluating upper-tract urothelial carcinoma. It is an educational reference and provides no clinical guidance.
Core questions
- How are upper-tract cytology specimens obtained and how do they differ from bladder samples?
- Why does instrumentation complicate upper-tract cytologic interpretation?
- How well does standardised reporting perform on upper-tract specimens?
- What is the role of cytology in evaluating upper-tract urothelial carcinoma?
Key concepts
- Selective (upper-tract) urinary cytology
- Ureteroscopic brushing
- Instrumentation artefact
- Upper-tract urothelial carcinoma
- Atypical urothelial cells in brushings
- Application of The Paris System to upper-tract specimens
Mechanisms
Upper-tract specimens are collected by passing catheters or ureteroscopes to wash or brush the ureter and renal pelvis. Brushing and catheterisation mechanically dislodge urothelial cells, producing crowded, pseudopapillary clusters and reactive changes that can simulate neoplasia; this instrumentation artefact inflates the proportion of specimens called atypical and is the principal interpretive pitfall. Because upper-tract sampling is targeted and often low-volume, and because instrumentation effects are common, the diagnostic accuracy and category distribution of standardised reporting can differ from that seen in voided bladder cytology (mansour-2025; kurtycz-2020).
Clinical relevance
Upper-tract cytology contributes to the evaluation of suspected upper-tract urothelial carcinoma alongside imaging and endoscopy; its performance characteristics describe how it adds to diagnostic evidence and are not a basis for individual management decisions. The content is educational only.
Epidemiology
Upper-tract urothelial carcinoma is considerably less common than bladder urothelial carcinoma but shares its urothelial origin and high-grade cytomorphology. Studies applying standardised reporting to upper-tract specimens report category-specific accuracy, with the atypical category posing particular difficulty (mansour-2025; nikas-2022).
Evidence & guidelines
The Paris System is applied to upper-tract specimens, but its performance is influenced by instrumentation artefact; recent diagnostic-accuracy studies highlight the 'atypical urothelial cell conundrum' specific to upper-tract sampling, where mechanically induced atypia is difficult to separate from genuine neoplasia (mansour-2025; kurtycz-2020).
History
Selective upper-tract cytology developed alongside retrograde catheterisation and, later, ureteroscopy, which improved access to the ureter and renal pelvis but introduced instrumentation artefact as a recurring interpretive challenge; standardised reporting was subsequently extended to and evaluated in these specimens (mansour-2025).
Debates
- How should instrumentation-induced atypia be classified in upper-tract specimens?
- Brushing and catheterisation produce crowded, reactive cell clusters that mimic neoplasia, so the boundary between artefact and a genuinely atypical or suspicious finding is especially uncertain in the upper tract.
Key figures
- Daniel Kurtycz
- Eva Wojcik
- Güliz Barkan
Related topics
Seminal works
- mansour-2025
- kurtycz-2020
Frequently asked questions
- How is an upper-tract cytology specimen collected?
- By selective washing or catheterisation of the ureter and renal pelvis, or by ureteroscopic brushing, which targets the upper tract directly rather than relying on voided urine.
- Why is upper-tract cytology harder to interpret than bladder cytology?
- Instrumentation mechanically dislodges urothelial cells into crowded, reactive clusters that can mimic carcinoma, increasing atypical interpretations and making the distinction from true neoplasia more difficult.