Patient referred for microscopic hematuria. What is the next question you should ask your patient?
A 21-year-old female is referred to nephrology for microscopic hematuria, found on a routine urinalysis. She has no medical problems. She takes no medications. She has no history of urinary tract infections. She is having no symptoms of a current UTI.
When the urinalysis was done, she was not having her period. It revealed dysmorphic erythrocytes but no erythrocyte casts.
This helps differentiate gross versus microscopic hematuria. We are concerned about glomerulonephritis as the cause of microscopic hematuria. The presentation is consistent with glomerular hematuria.
Hematuria can be classified as intermittent or constant, glomerular or nonglomerular, symptomatic or asymptomatic, with the most clinically useful classifications being gross or microscopic.
Microscopic hematuria is the detection of urinary red blood cells (RBCs) on a dipstick or by microscopic urinalysis, despite the visual appearance of the urine being normal.
Glomerular hematuria on urine microscopy is characterized by dysmorphic erythrocytes or acanthocytes, which have a ring shape with blebs protruding from their membrane.
Discussion:
Microscopic Hematuria
Definition and Prevalence
Hematuria is defined as the abnormal presence of blood in the urine and is one of the most commonly diagnosed urological disorders, accounting for over 20% of all urological evaluations.
Classification of Hematuria
Hematuria can be classified in various ways, including: * Intermittent or constant * Glomerular or nonglomerular * Symptomatic or asymptomatic
The most clinically useful classifications are: Gross Hematuria: Visible blood in the urine. Microscopic hematuria: Detection of urinary red blood cells (RBCs) via dipstick or microscopic urinalysis, with normal visual appearance of urine.
Diagnostic Approach
When a patient reports seeing blood in her urine, the next appropriate diagnostic test for suspected glomerulonephritis is the measurement of the urine protein-creatinine ratio. This helps determine the degree of proteinuria. It is also important to assess kidney function.
Urine Microscopy Findings
In cases of glomerular hematuria, urine microscopy may reveal: Dysmorphic Erythrocytes: Acanthocytes, which have a ring shape with membrane protrusions. Erythrocyte Casts: Their presence is highly associated with glomerular causes of bleeding, suggesting glomerulonephritis.
Intact erythrocytes may also be detected, but they are less specific for glomerular disease. The presence of proteinuria is a key feature in diagnosing glomerular disease and guides further diagnostic steps.
Further Evaluation
After determining the degree of proteinuria and kidney function, further evaluation for glomerular disease may be warranted. This may include: Kidney Biopsy: Conducted after quantitative determination of proteinuria and serologic testing to help identify the cause of the glomerulonephritis. This invasive test is not appropriate before evaluating asymptomatic hematuria.
Asymptomatic Hematuria
Asymptomatic hematuria is considered nonglomerular if there are no dysmorphic red cells and no proteinuria. In such cases, it is essential to evaluate for nonglomerular causes: * In a 21-year-old female, the first step is to exclude uterine bleeding. * In older patients, kidney ultrasonography and cystoscopy are important to evaluate for urologic malignancies.
Exclusion of Urinary Tract Infection
In this case, there is no indication of a urinary tract infection. Also, there were no leukocyte esterase or leukocytes present on microscopic urinalysis.
Potential Causes of Hematuria
This patient may have several conditions that could cause hematuria, including:
IgA nephropathy Alport syndrome Thin basement membrane disease Hypercalciuria Polycystic kidney disease Lupus And more
The differential diagnosis is broad, necessitating further evaluation of the patient’s microscopic hematuria as previously described.
