Lithotripsy is a non-invasive procedure that uses external energy to break kidney stones into smaller pieces that can pass naturally through the urinary tract. Seeing blood in the urine, known as hematuria, is a common and expected side effect after this treatment. This bleeding is a direct result of the process used to fragment the dense stone material and is a normal part of the recovery phase. Understanding the mechanics of the procedure helps explain why this temporary side effect occurs.
Understanding Lithotripsy’s Mechanism
The most common form is Extracorporeal Shock Wave Lithotripsy (ESWL), which uses a specialized machine called a lithotripter to generate high-energy acoustic shock waves outside the body. These pressure waves are focused precisely onto the kidney stone using imaging guidance like X-rays or ultrasound. The energy waves travel harmlessly through soft tissues until they reach the dense stone.
Upon hitting the stone, the shock waves create internal stresses and cavitation bubbles that cause the stone to shatter. The goal is to break the stone into tiny, sand-like fragments, ideally smaller than one millimeter, which can then be passed through the urinary system. A typical session may involve delivering up to 2,000 shock waves.
The Source of Blood in Urine
The source of the blood is the kidney tissue itself, not irritation from stone fragments passing through the ureter. As the focused shock waves pass through the kidney’s soft tissue, known as the renal parenchyma, before converging on the stone, they cause temporary micro-trauma.
This damage includes a disruption of the delicate blood vessels and capillaries within the kidney. The resulting vascular injury causes blood to leak directly into the kidney’s collecting system, where it mixes with the urine. While the shock waves target the stone, some energy dissipation affects the surrounding tissue. This temporary bleeding is self-limiting and indicates successful energy delivery.
Duration and Appearance of Hematuria
Hematuria after lithotripsy can be either microscopic or macroscopic (visible to the naked eye), which occurs in about 17% of patients. When visible, the urine may appear pink, light red, or smoky due to the presence of blood. This is generally a temporary finding that resolves quickly.
For most people, the visible blood in the urine lasts for only a few days, often clearing up within 48 hours. However, it is not uncommon for trace amounts of blood to appear intermittently for up to a week or even a few weeks as the stone fragments continue to pass.
Increasing fluid intake is crucial to help flush the blood and stone fragments out of the urinary system. Drinking at least two to three liters of water per day helps maintain a high urine flow, which prevents blood clots from forming and obstructing the ureter. If the bleeding seems to worsen or persist heavily beyond the first week, contact a healthcare provider.
When to Seek Immediate Medical Attention
While mild bleeding is a normal part of recovery, certain symptoms signal a complication that requires urgent medical review. The inability to urinate suggests a blockage where stone fragments or blood clots are completely obstructing the flow of urine. This can cause urine to back up into the kidney.
A high fever or the presence of chills and shivering, even without severe pain, requires immediate medical attention. These signs can indicate a urinary tract infection or a more severe systemic infection.
Additionally, any pain that becomes severe, worsens over time, or is not managed by prescribed pain medication should be promptly evaluated. Heavy, continuous bleeding, especially if large, dark red blood clots are being passed, requires immediate contact with a healthcare professional.