Hemorrhagic cystitis is defined as acute or chronic bleeding of the bladder. Patients with hemorrhagic cystitis often present with gross hematuria and dysuria. In severe forms, bleeding can lead to a significant decrease in blood hemoglobin levels. Hemorrhagic cystitis can occur in response to chemical toxins (cyclophosphamide, penicillins, busulfan, thiotepa, dyes, insecticides), viruses (adenovirus types 11 and 21 (Chapter 254), and influenza A), radiation, and amyloidosis. The polyoma BK virus, present latently in immunocompetent hosts, has been recognized as playing an important role in the development of drug-induced cystitis in immunosuppressed patients.

For chemical irritation related to use of cyclophosphamide, hydration, and the use of mesna disulfide, which inactivates cyclophosphamide metabolites, helps to protect the bladder. Administration of oral cyclophosphamide in the morning followed by aggressive oral hydration throughout the remainder of the day is very effective in minimizing the risk of hemorrhagic cystitis. Bladder irrigation with saline, alum, silver nitrate, or aminocaproic acid may be necessary in more severe forms of this disorder regardless of etiology. Gross hematuria associated with viral hemorrhagic cystitis usually resolves within 1 wk.

Gross or microscopic hematuria can follow vigorous exercise. Exercise hematuria is rare in girls and can be associated with dysuria. About 30-60% of runners completing marathons have dipstick-positive urine for blood. In limited follow-up, none appeared to have any significant urinary tract abnormalities. The color of the urine following vigorous exercise can vary from red to black. Blood clots may be present in the urine. Findings on urine culture, intravenous pyelography, voiding cystourethrography, and cystoscopy are normal in most patients. This seems to be a benign condition, and the hematuria generally resolves within 48 hr after cessation of exercise. The absence of red blood cell casts or evidence of renal disease and the presence of dysuria and blood clots in some patients suggest that the source of bleeding lies in the lower urinary tract. Rhabdomyolysis with myoglobinuria or hemoglobinuria must be considered in the differential diagnosis when associated with symptoms in the appropriate clinical context. Hydronephrosis or anatomic abnormalities must be considered in any child who presents with hematuria (particularly gross) after mild exercise or following mild trauma. Appropriate imaging studies are indicated in this setting.