Kidney Injury (Renal Trauma)

How kidneys are injured

Each kidney is about the size of a fist, sitting on either side of the spine under the lower ribs, surrounded by fat and protected by muscles. Despite this, about 1 in 10 people with significant abdominal trauma have a kidney injury.

• Blunt trauma (80 to 90 percent of cases): road traffic crashes, falls, contact sports (football, rugby, hockey), horse riding, assaults. A sudden deceleration can also tear the kidney's blood vessels.
• Penetrating trauma: stab and gunshot wounds, which more often need surgery.
• Medical procedures: kidney biopsy, lithotripsy or surgery can occasionally cause injury.

Kidneys that are already abnormal, such as with cysts, tumors, a blocked kidney or a horseshoe kidney, are more easily injured.

This page covers physical trauma. For a sudden loss of kidney function from illness, dehydration or medicines, see acute kidney injury.

Symptoms

• pain in the flank, side or back, below the ribs
• bruising or abrasions over the flank or lower ribs
• blood in the urine, visible or found on a urine test
• abdominal pain or tenderness
• nausea and vomiting
• signs of bleeding: dizziness, fainting, fast pulse, low blood pressure
• a flank mass from a collection of blood

The amount of blood in the urine does not always match the severity; a torn kidney artery may cause no blood in the urine at all.

Grades of kidney injury

Most injuries are grade I to III.

Diagnosis

1. Assessment of vital signs and the overall injury in a trauma setting.
2. Urine test for blood.
3. CT scan with contrast, including delayed images: the main test to grade the injury, show urine leaks and check other organs. It is done when there is visible blood in the urine, microscopic blood with low blood pressure, a high-energy mechanism, or penetrating injury.
4. Blood tests: blood count, kidney function and blood group.
5. Follow-up imaging for higher-grade injuries.

Treatment

Non-operative management

Most kidney injuries, including many high-grade blunt injuries, are managed without surgery:

• bed rest or reduced activity until visible blood in the urine clears
• close monitoring of vital signs and blood counts
• pain relief
• blood transfusion if needed
• follow-up imaging for higher grades

Procedures

• Angioembolization: a radiologist blocks a bleeding artery through a catheter from the groin, stopping bleeding while preserving most of the kidney.
• Ureteral stent: a thin tube placed through the bladder to drain a persistent urine leak.
• Drainage of an infected collection.

Surgery

Needed for uncontrolled bleeding, an expanding blood collection, some penetrating injuries and when other organs need surgery. Surgeons repair the kidney when possible, and remove it (nephrectomy) only when necessary. People can live normally with one healthy kidney.

Recovery

• Minor injuries usually heal within 2 to 6 weeks.
• Avoid contact sports, heavy lifting and strenuous activity for several weeks, typically until imaging shows healing for higher grades; your doctor will advise.
• Drink normally and watch for blood in the urine, fever or increasing pain.

Complications

• delayed bleeding, sometimes days to weeks later
• urine leak (urinoma) and infection or abscess
• high blood pressure, which can develop months to years later from scarring or compression of the kidney
• loss of function in the injured kidney
• arteriovenous fistula or pseudoaneurysm

Prevention

• Wear seat belts and use appropriate car seats.
• Use protective padding in contact sports and riding.
• People with a single kidney should discuss sports participation and protective gear with their doctor.

Frequently asked questions

What are the signs of a kidney injury after a fall?

Signs include pain in the side or back below the ribs, bruising over the flank, blood in the urine, abdominal pain and nausea. Dizziness, fainting or a racing pulse suggest internal bleeding and need emergency care.

Can a bruised kidney heal on its own?

Yes. Most kidney bruises and small tears heal on their own over several weeks with rest and monitoring. Your doctor will advise when it is safe to return to sports. Seek care if pain worsens, blood in the urine returns, or you develop a fever.

Is blood in the urine after an injury serious?

It should always be checked. Visible blood in the urine after a blow to the back or side suggests kidney or bladder injury and usually needs a CT scan. Most cases heal without surgery, but some injuries need treatment for bleeding.

What is the difference between kidney injury and acute kidney injury?

A kidney injury here means physical trauma to the kidney, such as a bruise or tear from a fall or crash. Acute kidney injury (AKI) is a sudden drop in kidney function, usually from illness, dehydration, sepsis or medicines, rather than a physical blow.