RENAL INJURIES
The kidney is injured in up to 5% to 10% of all severe trauma cases. At most urban trauma centers, approximately 80% to 90% of kidney injuries are blunt, while the remainder are penetrating. Children are more likely to sustain blunt renal injuries because of the relative large size of their kidneys, scant perirenal fat, and incomplete rib ossification. Blunt renal injuries are often minor and heal spontaneously, whereas penetrating renal injuries are typically significant and often require intervention.
GRADING SYSTEM AND RENAL PARENCYHMAL INJURIES
PRESENTATION
AND DIAGNOSIS
Patients
should be suspected of having renal injury if there is trauma to the flank,
abdomen, or lower chest; flank ecchymosis or tenderness; low posterior rib
fractures; or lumbar transverse process fractures. Although hematuria is the
major symptom and is seen in the vast majority of cases, it may be absent in
injuries to the renal pedicle or ureteropelvic junction. In addition, the
degree of hematuria often does not correspond to the severity of the renal
injury.
A detailed
history must be obtained regarding the circumstances of the trauma. Falls or
high-speed motor vehicle accidents, for example, may cause deceleration
injuries to the renal pedicle. In the setting of gunshot wounds, it is
important to determine if the injury is due to a high or low velocity missile
because high velocity missiles often cause more extensive kidney injury and
delayed necrosis.
The location
of any abdominal penetration must also be carefully documented. For example,
stab wound entrance sites posterior to the anterior axillary line and below the
nipple line are unlikely to have associated intraperitoneal organ injury or to
warrant abdominal exploration. The entrance and exit wound sites of a gunshot
should be marked with radiopaque markers so that the missile path can be
inferred on imaging.
In unstable
patients who require immediate abdominal exploration, urologists often advocate
for a one-shot intravenous pyelogram. Intravenous contrast is administered at 2
cc/kg of body weight, followed by a single abdominal radiograph 10 minutes
later. The primary aim of this study is to determine the function of the
contralateral kidney to avoid removing a solitary kidney. In many cases,
however, it can produce ambiguous results that are difficult to interpret.
Therefore, many trauma surgeons instead simply palpate the contralateral side
to assess for the presence of a second kidney. Another option is to infuse
intravenous methylene blue and temporarily occlude the ureter ipsilateral to
the injured kidney. Blue urine in the Foley bag indicates a functional
contralateral kidney.
In stable
patients, in ications for imaging a suspected kidney injury include:
1. Blunt trauma and gross
hematuria
2. Blunt trauma,
microscopic hematuria (5 RBC/ hpf), and shock
3. Major
acceleration-deceleration injury
4. Penetrating flank, back,
or abdominal trauma associated with gross or microscopic hematuria, or with a
missile path that is in line with the kidney
5. Pediatric trauma with
any degree of hematuria
6. Associated injuries/physical
signs suggestive of underlying renal injury
In stable
patients, computed tomography (CT) with intravenous contrast is the imaging
study of choice for demonstrating renal parenchymal injury,
perirenal/retroperitoneal hematomas, urine extravasation, injuries to the renal
hilum, and associated intraabdominal organ injuries. It is essential to obtain
both an arteriographic phase to assess for major vessel injury and a delayed
pyelographic phase to assess for contrast extravasation.
Parenchymal
contusions are noted as areas of reduced enhancement, whereas lacerations
appear as linear, blood-containing areas that interrupt the parenchyma.
Hematomas are visible as hyperattenuating collections that, if large and
confined to the subcapsular space, can compress the adjacent renal parenchyma.
Ultrasonography
is sometimes used as an initial screen but offers limited value. For example,
although ultra-sound can demonstrate perirenal fluid collections, it cannot
distinguish fresh blood from extravasated urine.
Arteriography and superselective embolization have
important roles in the evaluation and treatment of post-traumatic delayed renal
bleeding or pseudoaneurysms. In select cases, arteriography and endoluminal
stent placement have also been successfully used to manage renal artery intimal
tears and thrombosis from blunt trauma.
Based on the
findings from imaging studies, injuries can be graded according to criteria set
by the American Association for the Surgery of Trauma. The odds of intervention
and nephrectomy rise with each increase in grade.
RENAL HILAR INJURIES
TREATMENT
Blunt renal
injuries are often low-grade and can thus receive conservative management. Even
if there is urine extravasation, spontaneous resolution is likely unless there
is complete disruption of the UPJ (grade 5). Conservative management includes
strict bed rest until hematuria resolves, frequent assessments of hematocrit,
and reimaging after 3 to 5 days if there is urine extravasation. Persistent
bleeding demands repeat imaging, arteriography, or surgical exploration.
Worsening or symptomatic urine leaks often require ureteral stenting.
Penetrating renal injuries generally require exploration because they are often
high grade and associated with other major organ damage. Roughly three fourths
of renal gunshot wounds and half of renal stab wounds demand exploration.
The absolute
indication for surgical exploration of any renal injury is persistent and
potentially life-threatening bleeding. Such bleeding will occur if there is
avulsion of the main renal artery or vein, or if there is “shattering” of the
kidney by multiple deep lacerations. A pulsatile, expanding or unconfined
retroperitoneal hematoma suggests ongoing bleeding that requires intervention.
Relative
indications for surgical exploration include:
·
UPJ avulsion
·
High-grade penetrating renal injuries
· High-grade blunt renal injuries where abdominal exploration is performed
for other intraabdominal injuries
·
Devitalized renal parenchyma exceeds 50% of total
·
Persistent urinary leakage with failed endoscopic management
·
Persistent vascular injury with failed angiographic management
·
Bilateral renal artery thrombosis (or thrombosis in a solitary kidney)
·
Incomplete staging that demands either further imaging or renal
exploration
The injured
kidney is best exposed through a midline transperitoneal incision. Proximal
vascular control must be established before entering the renal fascia. If it is
not, there is a high risk of releasing a tamponade and causing a massive bleed
that necessitates a nephrectomy. When consistent proximal vascular control of
the renal pedicle is performed, however, the nephrectomy rate for renal trauma
is low.
Repair of
the damaged kidney requires broad exposure of the injured area, sharp excision of all nonviable parenchyma,
meticulous hemostasis, water-tight closure of the collecting system, and
parenchymal defect closure over a bolster.
The most
common complications after renal trauma include prolonged urinary
extravasation, delayed bleeding, arterial pseudoaneurysm, abscess, urinary
fistula, and hydronephrosis. Renovascular hypertension may occur after renal trauma
but is almost always transient. A rare, sustained hypertension is usually seen
with sub-capsular
hematomas that exert significant parenchymal compression, causing decreased
renal perfusion and subsequent re ease of renin (a phenomenon known as Page kidney).
