【General Internal Medicine】What causes elevated epithelial cells?

Epithelial cells in urine are normally present in small numbers, but an elevated count—often reported as “increased” or “many” on urinalysis—can indicate several underlying conditions. The most common cause is contamination during sample collection, particularly if proper midstream clean-catch technique was not followed; skin or vaginal epithelial cells may inadvertently enter the specimen. However, when contamination is ruled out, increased epithelial cells may reflect genuine urological pathology.

Squamous epithelial cells—large, flat cells with abundant cytoplasm—are typically associated with lower urinary tract or external genital sources and are less concerning unless accompanied by symptoms like dysuria, frequency, or visible discharge. Transitional epithelial cells (urothelial cells), which line the renal pelvis, ureters, bladder, and proximal urethra, may increase in response to inflammation, infection (e.g., cystitis or pyelonephritis), or irritation from stones, catheters, or tumors. Renal tubular epithelial cells—smaller, cuboidal cells—suggest involvement of the renal parenchyma and may be seen in acute tubular necrosis, interstitial nephritis, or glomerulonephritis, especially when accompanied by other urinary sediment abnormalities such as granular casts or proteinuria.

Clinical correlation is essential: asymptomatic individuals with isolated mild epithelial cell elevation often require no further action beyond repeat testing with proper collection. In contrast, patients with concurrent hematuria, pyuria, proteinuria, flank pain, fever, or abnormal renal function warrant targeted evaluation—including urine culture, renal ultrasound, or referral to nephrology or urology—depending on the suspected source and severity.