Renal Injury

Microscopic or gross hematuria may be encountered in patients with low-grade injury, while signs of hypovolemic shock (hypotension, weakness, loss of consciousness) may be the only symptoms in the setting of life-threatening hemorrhage as a result of severe kidney damage.

In order to obtain information regarding the cause of trauma and assess basic vital functions, a detailed patient history, and a thorough physical examination is crucial. Imaging studies, however, are needed to confirm the diagnosis and determine the extent of the injury. MDCT is the method of choice, as ultrasonography, magnetic resonance imaging, intravenous pyelogram and arteriography provide inferior results and may be useful in evaluating only specific areas of interest (blood vessels, ureters or the ureteropelvic junction and the renal pelvis) [1] [3].

Blood pressure control, ensuring adequate respiration and oxygen saturation, as well as transfusions (both whole red blood cell and fresh frozen plasma) in the setting of hypovolemic shock, are some of the main conservative measures employed in the setting of renal injury and they may be sufficient in patients who experience as high as stage IV injury [1]. Surgical exploration, vascular repair through angioembolization, salvage of the remaining kidney tissue and nephrectomy, on the other hand, are indicated in the setting of life-threatening hemorrhage and extensive trauma (stage V) [1] [6]. Urinary extravasation and the formation of urinomas, hypertension, renal failure, infection, and sepsis are possible complications of renal trauma [1], implying that early recognition and timely initiation of treatment is imperative.

The prognosis directly depends on the severity of kidney damage and the classification of renal injury is as follows [2] [4] [5]:

• Stage I - Characterized by contusion or the presence of a nonexpanding subcapsular hematoma, this form accounts for 80% of cases.
• Stage II - A nonexpanding perinephric hematoma confined to the retroperitoneum or the presence of a cortical laceration with a depth of < 1 cm that preserves the collecting system are the main features.
• Stage III - Apart from the laceration depth of > 1 cm, stage III is similar to stage II.
• Stage IV - Injuries of the renal vessels causing hemorrhage and devascularization of renal segments, as well as multiple lacerations involving the renal cortex, medulla, and the collecting system are predominant findings while expanding subcapsular hematomas and fractured kidneys also belong to stage IV.
• Stage V - Avulsion of the ureteropelvic junction that leads to complete kidney devascularization and a shattered kidney are hallmarks of the most severe clinical stage.

Based on the mechanism of injury, blunt or penetrating trauma are described as causes [1]. Motor vehicle accidents, contact sports (eg. martial arts), or fall from height are most common forms of blunt trauma [1], while gunshot and stabbing wounds are main examples of penetrating trauma, which is much rarely encountered in clinical practice [4].

Compared to splenic or liver damage, a renal injury is a less commonly encountered as a part of abdominal trauma and is established to occur in 1-5% of cases [1]. Penetrating forms of injury are predominantly seen in males [4].

Mechanical trauma to the renal parenchyma is the main event in kidney injury and the severity of trauma directly influences the extent of damage [2].

Having in mind the fact that kidney injury most likely occurs accidentally, early recognition of the condition may significantly improve the outcome and thus represent an important strategy in reducing mortality rates.

Seen in approximately 1-5% of all traumas, a renal injury is a broad term encompassing damage of the kidneys most frequently caused by blunt trauma (motor vehicle accidents, contact sports, fall from height) or penetrating trauma [1]. The clinical presentation depends on the severity of the injury, and stages from I (contusion, microscopic hematuria, normal urinalysis) to V (completely shattered kidney with devascularization) are described, but milder forms are seen in approximately 95% of cases [2] [3]. Multidetector computed tomography (MDCT) is the recommended diagnostic method in assessing renal injury [3]. A detailed multidisciplinary approach is necessary when deciding on optimal therapy, as the presence of other organ trauma (most commonly the spleen and the liver), and the potential development of numerous complications (hypovolemic shock, infection, hemorrhage, renal failure) may significantly complicate the clinical course [1] [3].

Renal injury is a broad term that encompasses various forms of kidney injury caused by trauma. Motor vehicle accident, falls from height and injury during contact sports (such as martial arts) are main modes of "blunt" trauma that may present with no external evidence of injury, whereas gunshot and stabbing wounds (also known as penetrating trauma) may also cause significant damage to the kidney. Depending on the severity of injury, symptoms may range from microscopic or gross appearance of blood in urine (hematuria) to life-threatening shock manifesting as hypotension, loss of consciousness and weakness, which is why early recognition of kidney injury is imperative. To assess the extent of damage and decide on optimal therapy, computed tomography should be performed, but only after a thorough physical examination that will make a presumptive diagnosis and evaluate whether additional organs may be damaged. For milder injuries, conservative measures consisting of blood pressure management and breathing control, together with blood transfusions may be sufficient, while surgery to repair damage and prevent complications (infection, leakage of urine, bleeding, kidney failure) may be necessary in more severe kidney damage.

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5. Tasian GE, Aaronson DS, McAninch JW. Evaluation of renal function after major renal injury: correlation with the American Association for the Surgery of Trauma Injury Scale. J Urol. 2010;183(1):196-200.
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