Epithelial cells in urine levels: what squamous, transitional and renal tubular cells mean, the normal count, and when a repeat sample is enough

Urine microscopy counts and classifies the cells shed from the lining of the urinary tract. Squamous epithelial cells are large, flat cells with a small nucleus from the lower urethra, the vagina and the skin of the genital area; they are the most common type seen and, in any number beyond a few, mean the sample picked up surface cells rather than coming cleanly from the bladder. Transitional (urothelial) cells are smaller and rounder, from the lining of the bladder, ureters and renal pelvis. Renal tubular epithelial cells are small, cuboidal cells with a large round nucleus, from the kidney tubules.

Labs report them per high-power field (hpf) or as none, few, moderate or many. Up to about 5 squamous cells per hpf is accepted as normal; some laboratories allow more in women. Transitional cells are normal in small numbers, more after catheterization; renal tubular cells are abnormal in anything beyond an occasional cell, and more than 15 per ten high-power fields is a marker of tubular injury.

The count only means something on a properly collected sample. Many squamous cells also bring white cells and bacteria from the skin and vagina, producing false-positive leukocyte esterase and culture results, which is why a contaminated urinalysis is repeated rather than acted on.

Epithelial cells are not ordered by themselves; they are reported with every urinalysis that includes microscopy, and the question is what to do when they are flagged. A high squamous count on a routine urinalysis calls for a repeat clean-catch sample if anything else on the report is abnormal and nothing if everything else is normal. Transitional cells in clusters or with blood in the urine in someone over 50 or a smoker warrant urine cytology and often cystoscopy. Renal tubular cells, especially with casts or protein, matter in anyone with kidney disease, after contrast or a nephrotoxic drug, with a recent severe illness or in a kidney-transplant recipient.

A complete urinalysis with microscopy can be ordered online through TestWell and collected as a walk-in urine sample at a Labcorp patient service center (the urinalysis with reflex to culture is also offered at Quest). The microscopy is what reports the cells, so a dipstick-only test will not.

The collection is the test. Wash hands; women should separate the labia and clean front to back with the wipe provided, men retract the foreskin and clean the tip; pass the first part of the stream into the toilet; catch the middle portion without touching the inside of the cup; finish in the toilet. Avoid collecting during menstruation or with a vaginal discharge, which add squamous cells and white cells, and deliver the sample within an hour or refrigerate it, because cells degrade. A first-morning sample is the most concentrated and is preferred when kidney tubular cells or casts are the question.

0–5 squamous cells per high-power field, reported as 'none' or 'few'. 'Moderate' or 'many' squamous cells is a contaminated specimen; the result is not wrong, but the rest of the urinalysis on that sample — particularly leukocyte esterase, bacteria and the culture — cannot be trusted and is repeated. Occasional transitional cells are normal; renal tubular cells should be absent or rare.

Many squamous cells with otherwise normal findings and no symptoms need nothing further. Many squamous cells with white cells, bacteria, nitrite or symptoms of infection need a repeat clean-catch urinalysis with culture before an antibiotic is prescribed; a culture from a contaminated sample grows mixed skin and vaginal organisms that are not an infection.

Squamous cells: a non-midstream or poorly cleaned sample, collection during menstruation or with vaginal discharge, vaginitis, and in men an unretracted foreskin — contamination in all cases. Transitional cells: a recent catheter or cystoscopy, kidney stones, urinary infection and bladder inflammation; clusters of transitional cells, atypical cells or transitional cells with persistent blood raise the possibility of urothelial (bladder or upper tract) cancer and prompt urine cytology and cystoscopy. Renal tubular cells: acute tubular necrosis after shock, sepsis or contrast; nephrotoxic drugs (aminoglycosides, cisplatin, NSAIDs); acute interstitial nephritis; glomerulonephritis; viral infections of the kidney (CMV, BK virus in transplant recipients); kidney-transplant rejection; and heavy-metal exposure. Renal tubular cells filled with fat (oval fat bodies) are a feature of nephrotic syndrome.

For many squamous cells: repeat the urinalysis as a careful clean-catch midstream sample, with a culture if infection is the question; if the repeat is clean and normal, nothing more. For transitional cells: a repeat urinalysis with microscopy; urine cytology and a urology referral for cystoscopy if the cells are clustered or atypical, if there is blood in the urine, or in a smoker or anyone over 50 with urinary symptoms. For renal tubular cells: serum creatinine and eGFR, a urine albumin-to-creatinine ratio, a review of casts on the same microscopy (granular and epithelial casts point to tubular necrosis, white-cell casts to interstitial nephritis), a medication review for nephrotoxins, and a nephrology referral when kidney function is reduced or falling.