HEMATURIA

ERICA L. LIEBELT, MD, FACMT AND VALERIE DAVIS, MD, PhD

Hematuria, the presence of red blood cells (RBCs) in the urine, is a presenting complaint in the emergency department (ED). The required evaluation for hematuria (either gross or microscopic) in the ED and its urgency is dictated by the patient’s history and clinical presentation. Recent literature has demonstrated that isolated gross hematuria in children and adolescents most often has a benign cause (hypercalciuria without nephrolithiasis or no apparent etiology) and long-term prognosis is good. Disease processes manifested by gross hematuria accompanied by other symptoms (e.g., acute onset of edema, headache, and hypertension), or with a history of trauma, are the context in which hematuria requires urgent/emergent evaluation in the ED. Microscopic hematuria (more than five RBCs per high-power field [HPF]) may be accompanied by other signs and symptoms or may be completely asymptomatic; it can usually be evaluated in the outpatient setting. In addition, asymptomatic microscopic hematuria in children is rarely indicative of serious illness and may warrant only a limited or even no diagnostic evaluation.

Red or brown urine does not always indicate hematuria. Several foods, substances, and drugs may color the urine; therefore, it is important to document the presence of blood in the urine. Reagent strips can be used as the initial screening test for hematuria. Heme-positive reagent strips must be confirmed by microscopic examination for the presence of RBCs because both hemoglobinuria and myoglobinuria can cause a positive reaction in the absence of RBCs. The evaluation of a child with hematuria must take into consideration the clinical presentation, patient and family histories, physical examination, and complete urinalysis so that a logical, orderly, and cost-effective approach can be undertaken.

PATHOPHYSIOLOGY

The pathophysiology of hematuria can be explained by categorizing it as either glomerular or nonglomerular. Immune-mediated inflammatory damage to the glomerular filtration surface, as seen in postinfectious nephritis, causes disruption of the glomerular basement membrane with subsequent leakage of RBCs and protein. Glomerular bleeding that results in gross hematuria may be brown, smoky, or cola or tea colored. RBCs may become enmeshed in the protein matrix to form RBC casts, a sensitive indicator of glomerular hematuria. The renal papillae are sites of nonglomerular bleeding that are susceptible to microthrombi and anoxia in patients with sickle cell disease or trait. Inflammation of the tubules and interstitium caused by antibiotics can result in hematuria, proteinuria, and eosinophiluria. Nonsteroidal agents can produce hematuria from both tubulointerstitial nephritis and inhibition of prostaglandin synthesis. Grossly bloody urine that is bright red or pink with or without clots is more likely to be originating from the lower urinary tract, usually the bladder or urethra. Hematuria from trauma to the kidney or bladder is caused by contusions, hematomas, or lacerations anywhere along the tract. Increased vascularity from infection or chemical irritation can lead to leakage of RBCs into the urine. Exercise-related hematuria results from ischemic injury as well as direct trauma. Benign familial hematuria, a principal cause of asymptomatic hematuria, is caused by leakage of RBCs through a thin glomerular basement membrane and rarely comes to the attention of the emergency physician except as an incidental finding.

DIFFERENTIAL DIAGNOSIS

The differential diagnosis of hematuria is vast and can be categorized on the basis of whether the cause of bleeding is disease restricted to the urinary system or secondary to a systemic process (Table 32.1). The most common causes of hematuria (Table 32.2) are urinary tract infection (UTI), hypercalciuria without nephrolithiasis, acute poststreptococcal glomerulonephritis, and trauma; the latter two also being the most common of the potentially life-threatening causes. Other potentially serious causes of hematuria include hematologic disorders, renal stones with obstruction, tumors, and hemolytic uremic syndrome (HUS). Other glomerular causes of hematuria that are primary renal diseases include nonstreptococcal postinfectious glomerulonephritides, membranous glomerulonephritis, immunoglobulin A (IgA) nephropathy, and Alport syndrome (hereditary nephritis). Hematuria as a manifestation of a systemic condition is most commonly seen in children with a vasculitis such as Henoch–Schönlein purpura, or systemic lupus erythematosus (SLE) (Table 32.3).

Extraglomerular causes of hematuria include congenital anomalies such as diverticula of the urethra and bladder; hemangiomas in the bladder; cysts of the kidneys, as in polycystic or multicystic kidney; and obstruction of the ureteropelvic junction. In addition to congenital anomalies, renal vein thrombosis secondary to a coagulation disorder or to the placement of an umbilical catheter is a cause of hematuria in the neonate. Wilms tumor is a common childhood solid tumor associated with hematuria. Nephrolithiasis should be considered if there is a family history or a predisposing condition such as recurrent infection, bladder dysfunction (seen in myelomeningocele), or chronic diuretic therapy. Hypercalciuria and cystinuria are metabolic diseases that also predispose patients to renal stones and hematuria. Finally, urethral prolapse may present with vaginal bleeding that can contaminate a collected urine specimen and be misinterpreted as hematuria.

EVALUATION AND DECISION

The initial evaluation of hematuria must begin with the confirmation of blood in the urine. Further investigation of the cause and treatment includes detailed patient and family histories, careful physical examination, and microscopic urinalysis. A specific diagnosis may or may not be made in the ED, and the patient may require further diagnostic testing. The most important role for the emergency physician in evaluating a child with hematuria is to identify serious, treatable, and progressive conditions such as trauma, nephritis associated with hypertension, bleeding disorders, and infection.

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