What is Kidney Trauma (Kidney Injury)?
Kidney trauma can lead to damage within the kidney or to its blood vessels, which can result in bleeding or injury to the urine collecting system. Despite being relatively uncommon, with only 10% of all injuries affecting the genitourinary tract (the system involving the organs used for urination and reproduction), the kidney is usually the organ most impacted. Kidney damage accounts for about 1% to 5% of all trauma patients, and a large majority of cases are due to blunt impact to the abdomen. However, injuries caused by a penetration of the kidney can occur up to 20% of the time depending on location and demographics.
Young men participating in sports, vehicular accidents, assaults or falls at an average age of 30 are most likely to sustain kidney injuries. According to a classification system from the American Association for the Surgery of Trauma, kidney injuries are categorized into five levels, guiding the treatment plan and projected outcome. Over time, treatment for kidney trauma has primarily shifted towards non-surgical methods, which often show success in preserving a functional kidney. This method stands as a better alternative to urgent surgical exploration that often leads to the removal of the kidney.
However, don’t overlook the fact that if a life-threatening kidney bleed occurs, it’s absolutely critical to explore surgically, especially for a patient with unstable vital signs.
What Causes Kidney Trauma (Kidney Injury)?
Kidney injuries tend to happen more from blunt force trauma than from penetrative wounds. There are several ways these injuries can happen. Motor vehicle accidents are the most common cause, followed by falls, sports injuries, and injuries caused by someone getting hit by a car. Blunt force can harm the kidney in different ways, like a direct hit, by crushing them against the back muscles, or due to sudden stops.
Sudden deceleration can be quite harmful, causing the connection between the kidney and the ureter, which carries urine to the bladder, to tear. It can also cause the blood vessels in the kidney to tear, or trigger a blood vessel disease that may lead to the kidney not getting enough blood. Penetrating kidney injuries, on the other hand, usually come from gunshot wounds, with stab wounds following close behind.
Risk Factors and Frequency for Kidney Trauma (Kidney Injury)
Renal trauma, or injuries to the kidneys, is seen in approximately 1% to 5% of all trauma patients. The majority of these injuries (80% to 90%) are caused by blunt abdominal trauma. Out of those with such trauma, 8% to 10% will have kidney injuries. If the trauma is penetrating, that number decreases to 6%. Both blunt and penetrating renal injuries often come with other injuries, with an 86% rate of associated injuries.
Morbidity (illness) and mortality (death) rates depend heavily on the severity of the injury, associated injuries, and the way it’s managed. Despite kidneys injuries still leading to serious illness, total kidney loss is decreasing. This is because of a standard care approach of non-surgical management for patients who are stable despite the severity of their injuries.
This decrease is also due to the increased use of a process called superselective renal artery angioembolization. This is where the bleeding blood vessel is deliberately blocked (embolization), targeting only the injured part of the kidney. It’s a more specific approach compared to traditional methods involving blocking the main artery to the kidney or removing the kidney completely (nephrectomy), both of which can lead to complete kidney loss.
Signs and Symptoms of Kidney Trauma (Kidney Injury)
Injuries to the chest, stomach, and pelvis area can increase the risk of kidney damage, particularly in trauma patients. Keep in mind that patients with existing kidney abnormalities may experience significant kidney damage even from minor injuries. This drives home the importance of thoroughly understanding a patient’s medical history.
Doctors need to conduct a detailed examination of a patient’s chest, stomach, sides, and lower abdomen areas. A kidney injury might be likely if the patient has tenderness or pain, or if they can feel a lump or see blueish-purple skin discoloration in their flank, abdomen, or back. Blood in the urine can also be a potential sign of kidney injury, but this isn’t always the case, especially in patients with multiple injuries. In cases of penetrating trauma, like stabbings or gunshot wounds, the location of the kidney injury could potentially be predicted based on where the entrance or exit injuries are.
- A stab wound in the front side of the body, for example, might indicate a possible injury towards the renal hilum – the area where the blood vessels, nerves, and tubes that carry urine out of the kidney are located.
- If the wound is towards the back, it could mean the actual kidney tissue, known as the renal parenchyma, is likely to be injured.
However, for gunshot wounds, the path of the bullet can vary, and even if the entry or exit points suggest possible kidney damage, there might not be any kidney injury present at all.
Testing for Kidney Trauma (Kidney Injury)
When dealing with potential trauma, doctors usually conduct a series of standard tests. These can include a complete blood count, a comprehensive metabolic panel, a coagulation panel, and a lactate test among others. They might also ask for urine to be analyzed. Blood in the urine is more commonly seen in patients who have experienced a blunt trauma to the kidneys than in those who have suffered a piercing kidney injury. However, the presence and amount of blood in the urine has not been shown to directly correlate with the severity of the kidney injury.
Doctors often resort to imaging to examine suspected kidney trauma. The preferred imaging method in these cases is a contrast-enhanced computed tomography (CT) scan, which involves capturing images immediately and after a delay. This type of scan allows them to evaluate the outer layer of the kidney, the renal vessels, and the collecting system accurately as each element responds differently to the contrast agent. The CT scan can also determine the extent of the injury, helping to validate if surgery is necessary. Moreover, the scan can indicate active bleeding by creating a “blush” image.
A patient with suspected kidney trauma may first undergo a focused assessment with sonography for trauma (FAST) exam. This exam, usually conducted in the trauma bay, primarily checks for fluid in the abdomen or in the pericardial sac around the heart. The presence of fluid usually points to bleeding in the patient, assisting with a faster diagnosis and decision on surgical intervention. However, this sonography exam has its limitations and doesn’t always detect retroperitoneal bleeding (bleeding behind the inner lining of the abdominal wall) or minor kidney injuries.
Patients who are hemodynamically stable or who have responded well to resuscitation efforts may require further examination with contrast-enhanced computed tomography. A negative result on this scan doesn’t rule out a kidney injury; further checks depend on the patient’s overall health status. If the patient shows signs of instability that calls for immediate surgery, an intraoperative intravenous urography (IVU) can be performed to better understand the functioning of the second kidney.
Kidney imaging could be necessary in the following situations: blunt abdominal trauma with either visible or microscopic blood in urine, blunt abdominal trauma with instability in vital signs, penetrating injury to the chest, abdomen, flank or back with suspected damage to the kidneys, or high clinical suspicion based on the specifics of the injury, like displaced rib fractures near the kidneys, severe car crashes or falls from significant height.
Injury grading relies on the system proposed by the American Association for the Surgery of Trauma (AAST). Using a contrast-enhanced CT scan, which is the best technique for kidney imaging, doctors determine the grade of the renal injury based on the AAST’s classification system.
Treatment Options for Kidney Trauma (Kidney Injury)
Trauma and urological surgeons agree that initial non-surgical treatment for patients with stable kidney trauma tends to yield better outcomes. This success is due to improvements in CT scan technology, which allows doctors to classify the severity of kidney damage, and a technique called angioembolization. Non-surgical management usually includes intensive care unit (ICU) monitoring, regular medical check-ups, blood level checks every 6 to 8 hours, blood product transfusion and angioembolization or placement of a drain if there’s urine leakage. This approach aims to preserve kidney function and avoid unnecessary kidney removal.
Patients who respond well to treatment can enjoy reduced medical screenings, potential reassignment from ICU to standard care, or even be discharged from the hospital. However, it’s suggested that patients with severe high-grade kidney injuries should have repeat CT scans two to three days after the initial scan to look for common complications like internal bleeding or urine accumulation in the kidney.
Angiographic embolization, a technique where a catheter is used to control bleeding through the arteries, has changed how doctors manage patients who are bleeding due to kidney injury. This technique is highly successful with a success rate as high as 88% and can save the kidney in up to 92% of cases. However, this procedure requires a specialized radiologist and facilities, and is only possible at hospitals where these resources are readily available. If not, the patient may need to be transferred to another hospital if it’s safe to do so. This technique is preferred over surgery as it has been shown to preserve kidney function more effectively and increase the success of kidney salvage.
However, if a patient with a kidney injury is unstable, unresponsive to treatment or doesn’t respond to non-surgical treatments, they may need surgery. Continuing to need blood transfusion, worsening urine leakage, severe kidney injuries, or when the upper urinary tract is ripped from the kidney are all conditions that may call for surgery. The primary goal in surgical intervention is to stop the bleeding and save the kidney, if possible. If removal of the kidney is being considered, it’s essential to confirm the patient has a second functional kidney. Surgery doesn’t always mean removal of the kidney; some injuries can be fixed with stitches or partial kidney removal if enough healthy kidney tissue remains.
Regardless of the grade of injury, most kidney injuries are low grade and are treated with supportive care. However, this doesn’t mean these patients can’t undergo angiographic embolization or surgery if needed. Higher-grade injuries, even if they’re stable, may require a trial period of supportive management. Injuries to specific kidney structures can initially be treated with a drainage tube or repair surgery if necessary, while extreme injuries require surgical repair. Some less severe injuries can be treated by using a tube to divert urine flow or to keep the ureter, the tube that carries urine from the kidney to the bladder, open.
Any puncture wound accompanied by active bleeding, urine leakage or affecting an area called the hilum, will need surgical exploration.
What else can Kidney Trauma (Kidney Injury) be?
- Sudden damage to the tube-like structures in the kidneys (Acute tubular necrosis)
- Build-up of waste products in the blood due to poor kidney function (Azotemia)
- Long-term disease where the kidneys do not work as well as they should (Chronic kidney disease)
- Fast action needed due to sudden inflammation of the small filters in your kidneys (Emergent management of acute glomerulonephritis)
- Condition that damages the blood vessels in the kidneys, often after a diarrheal illness (Hemolytic uremic syndrome)
- A disorder that could cause a rash, stomach pain, and kidney damage (Henoch-Schonlein purpura)
- High levels of potassium in your blood, which can affect your heart rhythm (Hyperkalemia)
- Too much magnesium in your blood, which could cause muscle weakness or heart problems (Hypermagnesemia)
- High sodium (salt) levels in your blood, which can dehydrate you (Hypernatremia)
- Dangerous high blood pressure levels that need immediate care (Hypertensive emergencies)
These all might sound quite ominous, but the important thing to remember is that they’re just names for different conditions. Each has its own symptoms and treatment options. If you’re dealing with one of these conditions, the best course of action is to speak with a healthcare professional. They can give you more information and guide you towards the treatment you need.
Possible Complications When Diagnosed with Kidney Trauma (Kidney Injury)
Active bleeding is often a serious complication associated with a traumatic kidney injury. This can frequently be seen with severe injuries, but even lower grade injuries can result in active bleeding. Delayed bleeding can occur 2 to 3 weeks after the injury and is typically due to either an arteriovenous malformation (an abnormal connection between arteries and veins) or a pseudoaneurysm (a false aneurysm). These complications are usually associated with severe injuries and penetrating trauma.
While active bleeding requires immediate attention, another complication – urine leakage outside of the kidney, or “urine extravasation” – is more common and affects roughly 7% of patients with kidney injuries. When this leaked urine accumulates, it gets trapped, typically in the layer covering the kidney. This is known as a urinoma. Most urinomas resolve on their own, but those that persist or get infected may need to be drained, either by using a needle or through surgery.
In addition to these, other delayed complications like kidney swelling due to fluid retention (hydronephrosis), chronic kidney infection (pyelonephritis), and high blood pressure due to kidney issues (postrenal hypertension) can occur.
The non-surgical treatment of severe kidney injuries often results in complications such as blood in the urine (hematuria), fever, acute kidney damage and urinomas. On the other hand, if these injuries are managed with surgery, complications may include wound infection, abscess around the kidney, and urinary tract infection.
Here are the common complications:
- Active bleeding
- Delayed bleeding
- Arteriovenous malformation
- Pseudoaneurysm
- Urine leakage outside the kidney
- Urinoma formation
- Kidney swelling due to fluid retention
- Chronic kidney infection
- High blood pressure due to kidney issues
- Blood in urine post non-surgical treatment
- Fever
- Acute kidney damage
- Wound infection post-surgery
- Abscess around the kidney
- Urinary tract infection
