Kidney Injury

Overview

Kidney injury, in the sense of trauma, means physical damage to one or both kidneys caused by an external force or wound. The kidneys are bean-shaped organs in the back of the abdomen that filter the blood and make urine. They are partly protected by the lower ribs, back muscles, and surrounding fat, but a strong blow or a penetrating wound can still injure them.

Injuries range from a minor bruise that heals on its own to a severe tear or shattering of the kidney with significant internal bleeding, which can be life-threatening. This page focuses on traumatic kidney injury. A separate, very different condition called acute kidney injury refers to a sudden drop in kidney function from illness or medications rather than physical trauma.

Symptoms

Symptoms depend on how badly the kidney is injured. They may include:

• Blood in the urine, which may make urine pink, red, or brown, a common sign of kidney injury.
• Pain in the flank or side, the back, or the abdomen.
• Bruising over the lower back or side.
• Swelling or tenderness in the area.
• Nausea and vomiting.
• In severe injuries, signs of significant blood loss, such as a rapid heartbeat, lightheadedness, pale skin, low blood pressure, or fainting, which are emergencies.

Because kidney injuries often happen with other injuries, symptoms may be part of a larger picture after an accident.

Causes

Kidney injuries are usually caused by trauma. Causes fall into two main groups:

• Blunt trauma, the most common type, from falls, motor vehicle or bicycle crashes, contact sports, or a direct blow to the back or side.
• Penetrating trauma, from stab or gunshot wounds.

Less commonly, a kidney can be injured during certain medical procedures. Kidneys that are enlarged or abnormal, or located lower than usual, may be somewhat more vulnerable to injury.

Risk Factors

Factors that raise the risk of a traumatic kidney injury include:

• Participation in contact or high-impact sports.
• Activities with a high risk of falls or collisions.
• Motor vehicle and bicycle use without proper protection.
• Occupations or situations with exposure to violence or penetrating wounds.
• Pre-existing kidney abnormalities that make the kidney larger or more exposed.

Diagnosis

After significant trauma, doctors evaluate for kidney injury using examination and imaging:

• Physical examination and vital signs to look for tenderness, bruising, and signs of internal bleeding.
• Urine testing, often the first clue, to check for blood.
• CT scan, the main imaging test, which shows the kidney in detail and reveals the type and severity of injury and any bleeding.
• Blood tests to assess blood loss and kidney function.
• Ultrasound in some settings.

Injuries are graded by severity, which guides treatment.

Treatment

Treatment depends on the severity of the injury and the person's overall condition:

• Minor injuries, such as bruises and small tears, often heal with rest, monitoring, fluids, and pain control, without surgery.
• Observation in the hospital with repeat tests for moderate injuries, watching for bleeding.
• Procedures to stop bleeding, such as a minimally invasive technique to block a bleeding vessel, in some cases.
• Surgery for severe injuries with major bleeding or other organ damage, which may aim to repair or, rarely, remove the kidney.
• Treatment of any other injuries that occurred at the same time.

Many people recover well, and the remaining healthy kidney can usually maintain normal function if one kidney is significantly damaged.

Prevention

Kidney injuries can be reduced with general safety measures:

• Wearing seatbelts and using proper child restraints in vehicles.
• Using appropriate protective gear in contact and high-impact sports.
• Taking precautions to prevent falls, especially in older adults.
• Following safety guidelines at work and during recreation.
• People with a single kidney or known kidney abnormality may wish to discuss activity precautions with a doctor.

When to See a Doctor

Seek emergency care immediately after a significant blow or wound to the back or side if you have blood in the urine, severe flank or abdominal pain, large bruising, or signs of major blood loss such as dizziness, fainting, a racing heartbeat, or pale, clammy skin. These can indicate serious internal bleeding.

Also see a doctor promptly for any blood in the urine after an injury, even if pain is mild, and for persistent flank pain, swelling, or tenderness following trauma. Prompt evaluation helps ensure injuries are not missed.

Related Topics

Frequently Asked Questions

References

1. MedlinePlus, U.S. National Library of Medicine.
2. Mayo Clinic.
3. American Urological Association.