An Overview of Kidney Lacerations

Symptoms, Causes, Diagnosis, and Treatment

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Table of Contents

A kidney laceration is an injury in which a tear in the kidney tissue might lead to bleeding or leaking of urine into the abdominal cavity. Lacerated kidneys can also lead to blood in the urine. All kidney injuries (also known as renal trauma) account for one to five percent of all traumatic injuries that are severe enough to require treatment at a trauma center. Kidney lacerations can result from either blunt or penetrating trauma.

There are two kidneys in the body which together filter almost 400 gallons of blood every day to adjust blood composition, fluid, and electrolyte balance, and remove waste through urine. In a pinch, we can function with one. They are shaped like kidney beans and are located toward the back of the abdomen on either side of the body, just below the diaphragm and the ribcage.

Each kidney is made up of chambers that work individually to drain urine into a central collection point. If one chamber is damaged, the others can still function.

There is a large artery feeding blood into the kidney and large vein taking blood out. Urine is drained out of the kidney and transferred to the bladder via the ureter.

Symptoms

Kidney lacerations don't just happen, so there has to be some sort of mechanism of injury. In addition to a history of trauma, there are several symptoms of kidney laceration:

  • Pain in the flank (back and side of the abdomen)
  • Bruising in the flank
  • Tenderness (hurts when you touch it)
  • Dizziness
  • Low blood pressure (top number below 90)

Blood in the urine is a telltale sign of kidney injury, but there could still be a kidney injury if you don't see blood in the urine. The blood might be microscopic or absent altogether.

Causes

Lacerated kidneys can occur from blunt trauma, which is when the body collides with an object that does not enter the body (such as a rock). However, they can also occur from penetrating trauma, which is when the object does enter the body (such as an arrow).

Most (four out of five) kidney injuries are caused by blunt trauma such as car accidents or falls. Some kidney injuries can be caused by penetrating trauma such as stabbing or shooting.

Diagnosis

Kidney injuries are classified by five grades. Each grade indicates increasing severity of the injury.

  1. A small hematoma (bruise) on the kidney. This grade does not require surgery and could easily be missed in the emergency department. The good news is that these injuries usually recover without treatment.
  2. A kidney laceration smaller than 1 centimeter deep. This type of kidney laceration will bleed and develop into a small hematoma on the outside of the kidney. These lacerations are not deep enough to affect the chambers of the kidney where urine is collected, so it is very unlikely that there will be any blood in the urine.
  3. A kidney laceration more than 1 centimeter deep, but not deep enough to affect urine collection. Just like in a grade 2 kidney laceration, this is very unlikely to cause blood in the urine.
  4. A kidney laceration deep enough to affect urine collection or the renal vessels (such as the ureter). Bleeding from a grade 4 kidney laceration will be self-limiting, meaning it will reach a point where the hematoma around the kidney will stop growing in size. Urine can leak out of the kidney and into the surrounding tissue from a grade 4 kidney injury.
  1. A shattered kidney. In a grade 5 injury, large ruptures of kidney tissue or vessels lead to massive bleeding around and in the kidney. Grade 5 kidney injuries almost always require surgery and often require removal of the injured kidney.

To diagnose a kidney injury, the doctor in the emergency department might order lab tests and a CT scan.

The clinical exam is the best tool to collect a good history of the events leading up to the visit (whether there is trauma or not), as well as to determine whether there is blood in the urine or not.

If blood is not visible in the urine, the doctor may order a urinalysis to look for microscopic blood.

Treatment

If you suspect a kidney injury, you should go to the emergency department for evaluation. If you feel dizzy or weak, call 911 rather than drive yourself to the hospital.

At the emergency department, treatment will depend entirely on the severity of the injury. In most cases, grades 1-4 can be managed without surgery. The doctor may admit you to the hospital for evaluation, order strict bed rest, and monitor vital signs as well as your fluid intake and urine output.

A Word From Verywell

Anytime you see blood in the urine following an injury, even if it doesn’t seem like your abdomen was involved, you should see a doctor. If you are feeling pain in the flank, tenderness in this area, or lightheadedness when you stand, you should go see the doctor (even if the injuring accident was several weeks prior). There are instances of delayed bleeding that can occur following blunt trauma to the abdomen. The good news with low-grade kidney injuries—and even many grade 3 and grade 4 injuries—is that the body can heal itself very well even without surgery.

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