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Urine Transitional (Urothelial) Epithelial Cells

A count of cells shed from the lining of your bladder and urinary tract. A few are normal.

AI-drafted. Awaiting verificationAlso called Trans Epi, Trans CellsLOINC 30089-7

What it is

Transitional epithelial cells, also called urothelial cells, line the inside of the bladder, the tubes from the kidneys (ureters) and the upper part of the urethra. Old cells shed into the urine all the time, so a few show up in most samples. They are smaller and rounder than the flat squamous cells from the skin and genital area, and they have a larger nucleus. Labs report them as a number per high-power field (HPF) under the microscope or in words such as few, moderate or many.

Why it matters

A few of these cells are normal. This count is a small part of the whole urinalysis, and your clinician reads it with red cells, white cells, bacteria and your symptoms. Larger numbers, clumps, or cells that look unusual may lead to a separate test called urine cytology, which looks closely at the cells.

If it’s high

More transitional cells than usual do not point to one cause. They can come from a recent catheter or urinary procedure, irritation or infection, or stones. If the cells look unusual, or you have blood in your urine, your clinician may order cytology or other tests.

Common causes

  • Normal shedding in a larger sample than usual
  • A recent urinary catheter, cystoscopy or similar procedure
  • Irritation or infection of the bladder or urinary tract
  • Kidney or bladder stones
  • Less often, changes in the urinary lining, which is why unusual-looking cells are checked further

What can help

  • Give a clean-catch midstream sample and take it to the lab promptly
  • Tell your clinician about a recent catheter, procedure or kidney stone
  • Ask whether a repeat urinalysis or urine cytology is needed if the finding is new or keeps showing up, or if you see blood in your urine

What can affect your result

  • A recent catheter or urinary procedure
  • Infection, irritation or stones
  • How fresh the sample is and how it was collected
  • How your lab counts and names the cells, since some groups transitional cells with other non-squamous cells
  • A recent urinary catheter, cystoscopy or similar procedure can add cells to the sample.
  • A sample that sat for hours before testing can give unreliable results; AFP advises examining within 2 hours or refrigerating.
  • Labs count and name cells differently: per high-power field, per low-power field, in words, or grouped with other non-squamous cells.
  • Automated analyzers sort cells by shape and may group transitional cells with renal tubular cells.

A midstream clean-catch sample, examined fresh. AFP advises examining urine within 2 hours, or refrigerating it if there will be a delay. Reflects the sample at the moment of collection.

When to talk to a clinician

A transitional cell count alone is not a reason for urgent care. See a clinician soon if you can see blood in your urine, or if you have burning with urination, fever, or back or side pain, whatever this result says.

Questions you could ask

  • Do my other urinalysis results and symptoms point to anything, whatever this cell count shows?
  • Could a recent procedure, infection or stone explain these cells?
  • Do I need a repeat urinalysis or a urine cytology test?

Questions people ask

Are transitional cells in my urine a sign of cancer?

Usually not. A few are normal because the lining of the urinary tract sheds cells all the time. Unusual-looking cells are checked with a separate test called urine cytology, so a count on a routine urinalysis does not say much on its own.

How are these different from squamous cells?

Squamous cells are large and flat and come from the skin and the last part of the urethra, so many of them usually means the sample picked up cells on the way out. Transitional cells come from inside the bladder and urinary tract.

Why does my report say "few" instead of a number?

Many labs grade cells in words. There is no single definition of "few" or "many", so the same word can mean different counts at different labs. Your lab's own flag is the best guide.

Show the science and sources

For clinicians and researchers

Transitional (urothelial) cells line the bladder, ureters and proximal urethra and desquamate continuously. The 2005 AFP review states their presence is normal and describes them as smaller and rounder than squamous cells with larger nuclei. There is no standard numeric reference interval, and word grades (few, moderate, many) have no universal definition, so this entry stores them as an ordered scale. Many automated analyzers do not report transitional cells separately: urine flow cytometers such as the Sysmex UF-100 identify transitional epithelial and renal tubular cells, and other platforms report a non-squamous epithelial cell class (LOINC 41284-1, 105089-7), which is not mapped to this marker because it also includes renal tubular cells. Automated image analysis has been used to flag atypical urothelial cells (Ann Lab Med 2019), but evaluating atypia is a cytology question. LOINC has no single code for all methods; 30089-7 (count per HPF) is listed first by analogy with other urine sediment counts, and the presence code 8249-5 is also in use.

LOINC 30089-7 (primary), 8249-5, 46136-8, 105095-4. Specimen: urine.

Sources

  1. Urinalysis: A Comprehensive Review, American Family Physician (2005)
  2. Office-Based Urinalysis: A Comprehensive Review, American Family Physician (2022)
  3. Progress in Automated Urinalysis, Annals of Laboratory Medicine (2019)

AI-drafted. Awaiting verification. Last reviewed 2026-10-03. How we build and check these pages.

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