Renal Trauma
Renal injuries are the most common injuries of the urinary system. Although well protected by lumbar muscles, ribs, vertebral bodies and viscera, the kidneys have a great mobility, consequently, parenchymal damage and vascular injuries can easily occur.
Trauma is generally caused by falls, road traffic accidents, blows, sporting accidents, stab wounds and gunshot wounds. Spontaneous rupture of the kidney is uncommon, nevertheless most urologists will have seen at least two or three cases during a lifetime of urological practice.
Renal trauma can be classified as either blunt (non penetrating) or penetrating, and both can be divided into two major classifications, the major and minor injuries.
Blunt renal trauma can be classified according to the severity of injury and the most common is the renal contusion. Blunt trauma in the region of 12th rib compresses the kidney against the lumbar spine, and the injuries will commonly involve the waist or lower pole of the kidney, where the 12th rib makes its impact. The kidney can be damaged from a blow in the abdomen anteriorly, just below the rib cage, particularly in road traffic accidents, such as the victim is thrown onto the steering column or some other projecting object. Abdominal injuries due to seat belts include 11% which involve the urinary tract and half of those are renal.
Penetrating injuries (usually from gunshot or stab wounds) account for 20% of renal traumas in an urban setting. The damage from a bullet will depend not only on direction, but also on the velocity of the missile. Low-velocity missiles will penetrate all structures in their path. With high-velocity missiles it is necessary to assume that the shock wave will have damaged an area around the track of the missile. A knife or stilleto stab can readily cut the cortex of the kidney if the weapon is driven more than 3 inches into the victim. Although a peri-renal hematomas usually develops, the patient may not show haematuria unless the weapon has reached the calyces or renal pelvis.
There is also the possibility of iatrogenic injuries, that can occur in the passage of a catheter up the ureter (damage of renal pelvis), when a renal biopsy is done or when there is an infection carried indirectly into the renal pelvis.
There are many types of classification, but the principal objective is to determine the extension of the injury and the possible management according to the type of injury. Basically we can divide it in five grades (Smith's General Urology, 13th ed., 1992). The grades I and II are classified as minor traumas, and the grades III, IV and V as major traumas:
GRADE I: contusion or contained subcapsular hematoma, without parenchymal laceration.
GRADE II: non expanding, confined perirenal hematoma or cortical laceration less than 1 cm deep, without urinary extravasation.
GRADE III: parenchymal laceration extending less than 1 cm into the cortex without urinary extravasation.
GRADE IV: parenchymal laceration extending through the corticomedullary junction and into the collecting system. There can be also thrombosis of a segmental renal artery without a parenchymal laceration.
GRADE V: three situations are possible:
The presence of associated pathologies can make the kidney be more liable to present with signs and symptoms after trauma. We should suspect of a pre-existing renal disease when the patient is apparently in good conditions, except for haematuria, and if there are major symptoms and signs after a trivial injury. The most common pathology found is hydronephrosis.
The cardinal sign of a renal trauma is haematuria, that can be massive or microscopic, but the extent of the injury cannot be measured by the volume of haematuria or the appearance of wound.
Another signs that can be present are the lumbar and the abdominal pain, sometimes with rigidity of the anterior abdominal wall and local tenderness.
If the patient presents a small flattening of the normal contour of the loin we should suspect of perinephric hematoma. In the case of retro peritoneal hematoma or effusion, the renal injury may be associated with paralytic ileus, what produces a danger confusing diagnosis of intra peritoneal trauma.
The physician should pay attention in rib fractures, pelvic fractures or vertebral injury, that can elicit a renal trauma.
Nausea and vomiting can be present. Extensive blood loss and shock may result from retroperitoneal bleeding.
Whatever the type of injury, the investigation for the staging of a renal injury begins with excretory urogram. This exam permits not only the identification of bone fractures, free intraperitoneal air and displaced bowel but also identify the presence or not of both kidneys, define the renal outlines, the collecting system and the ureters.
The intravenous pyelography is indicated when there is the possibility of nephrectomy. This exam shows if the opposite kidney has a normal function, ensuring that the patient will have a normal renal function after nephrectomy.
The use of ultrasonography is controversy, while some authors believe that every patient should undergo an ultrasonic scanning because it may show the size of a possible perirenal hematoma and monitor whether its extending or resolving, others authors believe that this exam is nonspecific and does not provide sufficient information.
When the excretory urogram does not define well the extent of injury, the patient can be evaluated by a CT scanning or an arteriography. The CT scanning can distinguish better a major from minor injury, can identify extravasation that were not demonstrated in excretory urogram. It can also distinguish renal laceration and outline an intrarenal hematoma. Arteriography can be used when there is no CT scan available or when the CT is not a definitive exam, and it may reveal the actual bleeding vessel, show occlusion of the main renal artery or its branches, and also renal lacerations.
The treatment of patients with renal injuries will depend on the extent of the injury.
The patients with minor injuries, that only present microscopic haematuria, need only observation for 48 to 72 hours and an urologic follow-up care.
In the cases of parenchymal lacerations, that are restrict to the cortex, the patient should be hospitalized, at bed rest and with broad-spectrum antibiotics.
When there is deep parenchymal laceration, the patient should be treated conservatively and the physician should attempt for the posterior presence of abscess, infection, hypertension, renal atrophy and secondary hemorrhage.
Patients with the more significant parenchymal lacerations (major injuries), extensive extravasation, vascular injuries or pulsatile hematoma, should undergo surgery exploration. The surgery exploration is best done through a trans abdominal transperitoneal approach, trying to make the best wide exposure and an early vascular control at the first moment.
Penetrating injuries from gunshot or stab wounds require surgical exploration, but it is not necessary if the CT scan or arteriography show a minor injury, without extravasation of contrast medium, what confirms preservation of vascularities.
The most common and possible complications of renal injuries are:
1. Current; Emergency Diagnosis & Treatment; 4th ed.; Chap. 20; 291-295.
2. Sabiston's; Textbook of Surgery; 15th ed.; Chap 17; 328-329; Chap 45; 1539-1540.
3. Mitchell, P.; Urinary Tract Trauma; ed.; ( ano ); Chap. 1; 3-16; Chap. 2; 18-20; Chap. 3; 23-37; Chap. 4; 44-48, 51-53.
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