Kidneys are injured more often than any of the organs along the urinary tract from external trauma. Blunt force due to motor vehicle crashes, falls, or sports injuries is the usual cause of urinary tract injury. Penetrating kidney injuries most often result from gunshot or stab wounds. Less commonly, injuries can occur during diagnostic tests, such as a kidney biopsy, or during various treatments, such as those for kidney stones, including extracorporeal shock wave lithotripsy, and are usually minor. Similarly, most blunt kidney injuries are minor. However, some are serious. If serious blunt or penetrating kidney injuries are not treated, complications, such as kidney failure or kidney loss, delayed bleeding, infection, and high blood pressure may result.
Symptoms of a blunt kidney injury may include blood in the urine, pain or bruising in the upper abdomen or the area between the ribs and hip (flank), marks near a kidney made by a seat belt, or pain resulting from fractures of the lower ribs. When kidney injuries are severe, low blood pressure (shock) and anemia may occur if the person loses a significant amount of blood.
Kidney Injuries: Minor to Severe
The history of events that led to the injury, the person's symptoms, and a physical examination help doctors recognize kidney injuries. A sample of urine is taken and examined to see whether blood is present. Blood in the urine in a person with an injury to the trunk indicates that the injury may involve the kidney. The blood may be visible with the naked eye (gross hematuria) or visible only using a microscope (microscopic hematuria).
With penetrating injuries, the location of the wound (whether in the upper or mid part of the abdomen, back, or flank) may help doctors determine whether the kidney is involved.
Adults who have mild symptoms, without an abnormally low blood pressure, and blood in the urine that is visible only with a microscope probably have a minor injury that will heal on its own. Further tests are usually not needed. For children, and for adults in whom doctors suspect a more serious injury, computed tomography (CT) with radiopaque contrast agent, a liquid that is visible on x-rays, should be done.
For minor kidney injuries, careful control of fluid intake and bed rest are often the only treatment needed because these measures allow the kidney to heal itself. For more serious injuries, treatment begins with steps to control blood loss and to prevent shock. Fluids and sometimes blood are given intravenously to help keep blood pressure within a normal range and stimulate urine production.
Only serious blunt injuries, such as when the kidney is bleeding persistently, is surrounded by a blood clot that is expanding, or is torn from its attachments to blood vessels, require surgical repair. Alternatively, some of these injuries can be managed with arterial embolization, in which doctors pass a catheter through a blood vessel in the upper thigh into the bleeding kidney vessel. When the catheter is at the bleeding site, doctors inject a substance or a wire coil to block the blood vessel and thereby stop the bleeding (embolization). Serious penetrating injuries similarly require surgical repair. Rarely, the injured kidney needs to be removed.
Most people recover from even serious kidney injuries, provided the injuries are diagnosed and treated promptly. Chronic kidney disease, when it develops, may require lifelong treatment. Other complications of kidney injuries that require treatment include delayed bleeding, infection, and high blood pressure.