Is a urinalysis report showing nitrite, positive leukocyte esterase, many bacteria, and significant white blood cells (WBCs) per high power field (hpf) consistent with a urinary tract infection (UTI) and what does the presence of renal tubular epithelial (RTE) cells indicate?

Urinalysis Report Analysis for Suspected UTI

The urinalysis report is strongly consistent with a urinary tract infection (UTI), showing classic findings of pyuria, bacteriuria, positive nitrite, and positive leukocyte esterase; however, the presence of renal tubular epithelial (RTE) cells is concerning and not consistent with a simple UTI, suggesting possible renal involvement or tubular injury.

Analysis of Urinalysis Results

a. Consistency with UTI

The urinalysis report shows multiple findings highly consistent with a UTI:

• Positive nitrite: Indicates the presence of bacteria that can reduce nitrate to nitrite (typically gram-negative organisms). Nitrite has high specificity (93-98%) for UTI 1, though moderate sensitivity (53%).
• Positive leukocyte esterase (2+): Indicates the presence of white blood cells, with sensitivity of approximately 83% for UTI 1.
• Microscopic findings of 80-100 WBCs/hpf: Represents significant pyuria, well above the threshold of ≥10 WBCs/hpf that strongly indicates UTI with sensitivity of 77-84% and specificity of 78-91% 1.
• Many bacteria: Direct visualization of bacteria supports the diagnosis.
• Hazy appearance: Consistent with pyuria and bacteriuria.

The combination of positive nitrite, positive leukocyte esterase, pyuria, and visible bacteria provides the highest diagnostic accuracy for UTI 1. When these parameters are positive together, the sensitivity for UTI approaches 94% 2.

b. Concerning Microscopic Finding

The presence of 10-15 RTE cells/hpf is concerning and not consistent with a simple UTI. Renal tubular epithelial cells are not typically found in significant numbers in uncomplicated lower UTIs. Their presence suggests:

1. Possible upper urinary tract involvement (pyelonephritis)
2. Renal tubular injury or inflammation
3. Possible nephrotoxicity from medications
4. Other renal parenchymal disease

This finding warrants further investigation beyond simple UTI treatment.

c. Probable Cause of Error

The most probable cause of error in the report would be misidentification of transitional epithelial cells as RTE cells. Transitional epithelial cells from the bladder and lower urinary tract can sometimes be confused with RTE cells, especially when:

• Cells are damaged or altered by inflammation
• Laboratory personnel have limited experience
• Staining techniques are suboptimal
• Cells are viewed at different angles

Transitional epithelial cells would be expected in a UTI due to inflammation of the bladder mucosa, while true RTE cells would suggest kidney involvement.

Clinical Implications

1. Diagnosis: The urinalysis strongly supports a UTI diagnosis with multiple positive indicators (nitrite, leukocyte esterase, pyuria, and bacteria).

2. Further evaluation needed: The presence of RTE cells, if confirmed, suggests:

   • Possible pyelonephritis rather than simple cystitis
   • Need for more aggressive treatment approach
   • Consideration of renal function tests
   • Possible imaging studies to evaluate upper urinary tract

3. Laboratory follow-up: Consider requesting confirmation of RTE cells by an experienced technologist, as this finding significantly changes the clinical interpretation.

4. Treatment considerations: If RTE cells are confirmed, treatment should address potential upper tract involvement with appropriate antibiotic coverage and duration.

Pitfalls and Caveats

• Relying solely on dipstick without microscopy can lead to false positives. The sensitivity of combined leukocyte esterase and nitrite is high (94%), but specificity is lower (50%) 2.
• Proper specimen collection is crucial. This specimen was catheterized, which reduces contamination risk compared to clean catch specimens 1.
• Urine culture remains the gold standard for UTI diagnosis despite positive urinalysis findings 3.
• False-positive results for leukocyte esterase can occur even in disease-free women, with rates of 35-50% depending on collection technique 4.
• The presence of RTE cells should trigger consideration of nephrotoxic medication review and renal function assessment.