From the Guidelines
Trace blood in a urinalysis (UA) should be further evaluated to determine the underlying cause, and according to the American College of Physicians, clinicians should confirm heme-positive results of dipstick testing with microscopic urinalysis that demonstrates 3 or more erythrocytes per high-powered field before initiating further evaluation in all asymptomatic adults 1. This finding can be an indication of various conditions, including urinary tract infections, kidney stones, glomerulonephritis, bladder or kidney tumors, trauma, strenuous exercise, menstruation in women, or certain medications like anticoagulants. Some key points to consider when evaluating trace blood in a UA include:
- The presence of blood in the urine can be a sign of serious underlying disease, including malignancy 1
- The initial determination of microscopic hematuria should be based on microscopic examination of urinary sediment from a freshly voided, clean-catch, midstream urine specimen 1
- The recommended 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 1
- Clinicians should refer for further urologic evaluation in all adults with gross hematuria, even if self-limited, and consider urology referral for cystoscopy and imaging in adults with microscopically confirmed hematuria in the absence of some demonstrable benign cause 1
- Clinicians should pursue evaluation of hematuria even if the patient is receiving antiplatelet or anticoagulant therapy 1 It is essential to follow up with a healthcare provider if trace blood is found on a UA, as they may order additional tests or referrals to determine the underlying cause and provide appropriate treatment.
From the Research
Urinalysis and Blood Traces
- Urinalysis is a diagnostic tool used to determine the etiology of various acute or chronic pathologies, including urinary tract infections (UTIs) 2
- The presence of blood in urine, also known as hematuria, can be either gross or microscopic and warrants a thorough history and physical to determine potential causes and assess risk factors for malignancy 3
- Microscopic hematuria most commonly has benign causes, such as urinary tract infection, benign prostatic hyperplasia, and urinary calculi 3
Urine Blood and UTI Resistance
- A study found that less urine blood was associated with an increased likelihood of resistance to nitrofurantoin, a commonly prescribed antibiotic for UTIs 4
- The study also found that the presence of any history of kidney stones was significantly associated with an increased risk of resistance to nitrofurantoin 4
- Another study found that bacteriuria is more specific and sensitive than pyuria for detecting urinary tract infection, even in older women and during pregnancy 5
Diagnosis and Treatment of UTIs
- Urine culture is the gold standard for detection of urinary tract infection, but asymptomatic bacteriuria is common, particularly in older women, and should not be treated with antibiotics 5
- First-line treatments for urinary tract infection include nitrofurantoin, fosfomycin, and trimethoprim-sulfamethoxazole (when resistance levels are <20%) 5
- A review of studies found that trimethoprim-sulfamethoxazole, nitrofurantoin, and fosfomycin are all appropriate first-line therapies for uncomplicated cystitis 6