An Overview of Kidney Lacerations

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. The blood or urine collects in a space called the retroperitoneum, which is behind the peritoneum, where your bowels are located. Lacerated kidneys can also lead to blood in the urine. All kidney injuries (also known as renal trauma) account for 1% to 5% 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.

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 steering wheel after a car crash). However, they can also occur from penetrating trauma, which is when the object does enter the body (such as a knife or bullet).

Types of Kidney Injuries

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

• Grade 1: Subcapsular hematoma and/or renal contusion. This grade does not require surgery and causes little to no permanent damage to the kidney.
• Grade 2: Laceration ≤ 1 cm in depth without urine leakage. In this grade a small blood collection occurs around the kidney which over time will heal on its own and not require any surgery.
• Grade 3: Laceration > 1 cm without urine leakage. In this grade a small blood collection occurs around the kidney which over time can heal on its own and not require any surgery.
• Grade 4: Laceration involving the collecting system with urine leakage, injury to blood vessels going into the kidney, or injury to the kidney pelvis where the urine funnels into the ureter This grade laceration will likely require a surgical procedure depending on nature of injury. Treatment can be as simple as placement of a stent into the ureter by a urologist or exploration and repair of the kidney or even removal of the kidney.
• Grade 5: Shattered or devascularized kidney with active bleeding; main renal vascular laceration or avulsion. This grade of injury requires emergency surgery and in most cases removal of the entire kidney and repair of injured blood vessels.

Diagnosis

The diagnosis of a renal injury is done through a detailed history and physical. Labs and imaging will be ordered to evaluate the injury and to help plan for treatment. Labs may include checking urine for blood, hemoglobin, and hematocrit to check for blood loss, and renal function tests to check functioning of the kidneys. The standard imaging is a CT Urogram which is cat scan done with IV contrast and delayed films to help visualize the kidney in its entirety.

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.

Based on the findings from the workup you may be sent home or admitted to the hospital for observation with frequent lab checks, strict bed rest, and close monitoring of vital signs. If you are sent home after observation there may be a plan to check repeat imaging in the future. If your injury is high-grade, you may require emergency surgery.

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.