Microscopic hematuria

Microscopic hematuria is a medical condition characterized by the presence of red blood cells (RBCs) in the urine that are not visible to the naked eye but can be detected under a microscope. It is a common finding in clinical practice and can be an indicator of various underlying conditions, ranging from benign to potentially serious diseases.

Definition

Microscopic hematuria is typically defined as the presence of three or more RBCs per high power field (HPF) in a urine sediment examined under a microscope from at least two out of three urine samples. This definition helps to distinguish it from gross hematuria, where blood in the urine is visible to the naked eye.

Causes

The causes of microscopic hematuria are diverse and can be classified into glomerular and non-glomerular sources based on the origin of the bleeding.

Glomerular Causes

Glomerular causes are related to diseases that affect the glomerulus, a network of tiny blood vessels in the kidneys that performs the first step of filtering blood. Conditions such as glomerulonephritis, IgA nephropathy, and Alport syndrome can lead to microscopic hematuria.

Non-Glomerular Causes

Non-glomerular causes include a wide range of conditions affecting the urinary tract outside the glomerulus, such as urinary tract infections (UTIs), kidney stones, bladder cancer, and prostate disease in men. Trauma, vigorous exercise, and certain medications can also cause microscopic hematuria.

Diagnosis

The diagnosis of microscopic hematuria involves a thorough history and physical examination, followed by laboratory and imaging studies to identify the underlying cause. Initial evaluation includes a detailed medical history, focusing on risk factors such as age, smoking history, and exposure to potential nephrotoxic substances. Urinalysis is performed to confirm the presence of RBCs and to look for other abnormalities. Further diagnostic tests may include urine culture, cystoscopy, and imaging studies such as ultrasound or CT scan of the abdomen and pelvis.

Management

The management of microscopic hematuria depends on the underlying cause. In cases where a specific cause is identified, treatment is directed at that condition. For example, UTIs are treated with antibiotics, while kidney stones may require lithotripsy or surgical removal. In cases where no specific cause is found, patients may be monitored with periodic urinalysis to detect any changes in their condition.

Prognosis

The prognosis of microscopic hematuria varies widely depending on the underlying cause. While many cases are benign and resolve spontaneously, persistent or recurrent hematuria requires careful evaluation to rule out serious conditions such as cancer.