What are normal findings for blood on a catheterized (urinary catheter) urinalysis?

From the Guidelines

In a normal catheterized urinalysis, the presence of 0-3 red blood cells (RBCs) per high-power field is considered within normal limits. According to the American Urological Association's Best Practice Policy recommendations 1, the definition of microscopic hematuria is three or more red blood cells per high-power field on microscopic evaluation of urinary sediment from two of three properly collected urinalysis specimens.

Key Considerations

• The presence of blood in urine, even in small amounts, can be a sign of underlying disease, including malignancy, and warrants further investigation 1.
• Catheterization itself can cause minor trauma to the urethra, resulting in a small amount of blood in the sample, but this should be minimal and transient.
• Healthcare providers should consider that even trace amounts of blood (>3 RBCs/HPF) may indicate conditions such as urinary tract infections, kidney stones, tumors, or glomerular disease.

Interpretation of Results

When evaluating catheterized urine samples, the timing and context of catheterization should be considered when interpreting results. The absence of blood in urine is physiologically normal because intact blood vessels in the urinary tract should prevent RBCs from entering the urine, and the glomerular filtration barrier in healthy kidneys prevents blood cells from passing into the filtrate. If blood is detected in a catheterized sample, further investigation is necessary to determine the underlying cause.

Normal Findings

• 0-3 red blood cells (RBCs) per high-power field: considered within normal limits
• Any value above this threshold: indicates hematuria, which warrants further investigation 1.

From the Research

Normal Findings for Blood on a Catheterized Urinalysis

• The presence of blood in the urine, either on voiding or in a catheterized specimen, is defined as hematuria 2
• Hematuria can be broadly divided into microscopic and gross hematuria, and may be symptomatic or asymptomatic 2
• The causes of hematuria include a wide spectrum of conditions, such as calculus, trauma, tumors, vascular, and miscellaneous causes 2, 3

Evaluation of Hematuria

• CT urography is a useful technique for evaluating hematuria, and can be used alone for this task 2, 3
• The optimum diagnostic imaging strategy for patients with hematuria at high-risk for urothelial cell carcinoma involves the use of CT urography as a replacement for other imaging tests 3
• Ultrasound alone is insufficient for imaging of hematuria, and may not be able to differentiate renal transitional cell carcinoma from other causes of filling defects of the renal collecting system 4

Reporting of Hematuria

• Hematuria on a urinalysis should be reported as 0 to 3 RBC/HPF, 4 to 10 RBC/HPF, 11 to 25 RBC/HPF, 26 to 50 RBC/HPF, >50 RBC/HPF, or gross hematuria 5
• Referral to urology is recommended for all people with gross hematuria or high-grade hematuria (>50 red blood cells per high-power field [RBCs/HPF]) on a single urinalysis (UA) 5

Key Points

• Hematuria can be a sign of serious disease, such as bladder cancer, upper urinary tract urothelial cell carcinoma, renal cell cancer, or urinary tract stones 3
• CT urography is a sensitive and specific test for evaluating hematuria, and can help to identify the underlying cause of the condition 2, 3
• The evaluation and management of hematuria should be guided by national practice recommendations, which emphasize the importance of referral to urology and the use of CT urography in high-risk patients 5