2. RENAL INJURY
• Renal injury is common, occurring in 8–10% of cases.
• About 90% of renal injuries result from blunt force
injury and 10% from penetrating trauma.
• imaging depends on
- haemodynamic status
- haematuria
- other injuries
- USG is relatively insensitive for detection of renal
lacerations and contusions, extravasation of blood or
urine, collecting system disruption and parenchymal
haematoma
- A positive ultrasound was more likely with higher
grades of renal injury, but a negative renal ultrasound
had a very low negative predictive value
3. • The significance of haematuria as an
indicator of significant renal injury has been
the subject of debate
• As a rule, all patients with penetrating flank
and back trauma should have a CT
examination
4. Indication Imaging study
Penetrating flank and back trauma Chest, abdominal–pelvic CT with IV and
oral contrast medium
Gross haematuria Abdominal–pelvic CT with oral and IV
contrast medium if haemodynamically
stable or resuscitated
Haemodynamically unstable requiring
emergency surgery
Intraoperative IVU when stabilized
Haemodynamically stable with microscopic
haematuria, but no other indication for
abdominal–pelvic CT
Observation until resolution of haematuria
Haemodynamically stable with microscopic
haematuria, but other indications for
abdominal–pelvic CT (+ abdominal
examination, decreasing haematocrit,
indeterminate result of peritoneal lavage or
abdominal ultrasound, unreliable physical
examination)
Abdominal–pelvic CT with oral and IV
contrast medium
Haemodynamically stable with or without
microscopic haematuria with evidence of
major flank impact (e.g. lower posterior rib
or lumbar transverse process fracture,
Abdominal–pelvic CT with oral and IV
contrast medium
5. AAST injury grade Description
I Renal contusion or subcapsular haematoma
with intact capsule
II Superficial cortical laceration that does not
involve the deep renal medulla or collecting
system or nonexpanding perinephric
haematoma
III Deep laceration(s) with or without
extravasation of urine
IV Lacerations extending into the collecting
system with contained urine leak
V Shattered kidney, renal vascular pedicle
injury, devascularized kidney
6. • CT of renal contrast medium extravasation. (A) Nonenhanced CT performed approximately 24 h after intravenous contrast-enhanced study for blunt
trauma shows iodinated urine that has extravasated into the right renal parenchyma at several points, possibly through disruption of the collecting
system tubules. (B) Coronal reformation shows several areas (arrows) of residual extravasated contrast-enhanced urine.
7. • CT of renal infarct. IV contrast-enhanced CT image reveals a sharply
demarcated region of low density (no enhancement) in the upper pole of
the right kidney, indicating segmental infarction after blunt trauma.
8. • Subcapsular renal haematoma. The haematoma compresses the right
renal parenchyma leading to delay in renal perfusion and contrast
excretion. The renal parenchyma otherwise appears intact.
9. Description or CT finding
I
Superficial laceration(s) involving cortex
Renal contusion(s)
<1 cm subcapsular haematoma
Perinephric haematoma not filling Gerota's space and no
Segmental renal infarction
II Deeper renal laceration extending to medulla, with intact collecting system
> 1 cm subcapsular haematoma with intact renal function
Perinephric haematoma limited to and not distending the perinephric space; no active bleeding
III
Laceration extending into collecting system with urine extravasation limited to retroperitoneum
Perinephric haematoma distending perinephric space or extending into pararenal spaces; no active bleeding
IV
Fragmentation (three or more segments) of the kidney (usually partially devitalized with large perinephric
haematoma)
Devascularization > 50% of parenchyma
Main renal pedicle injury
10. • Most renal injuries are minor (75–98%)[16],
represented by CT grades I and II, and are successfully
treated without intervention. Contusions are
visualized as ill-defined low attenuation areas with
irregular margins. They may appear as regions with a
striated nephrogram pattern due to differential blood
flow through the contused parenchyma.
• Segmental renal infarcts are relatively common in
blunt renal trauma, and result from stretching and
subsequent occlusion ofan accessory renal artery,
extrarenal or intrarenal branches of the renal artery,
or a capsular artery[18]. These infarcts appear as
sharply demarcated, wedge-shaped areas of very low
attenuation, typically involving the renal pole
11. • Post-traumatic urinoma. Injury to the collecting system with contrast collection
(urine) accumulating in the urinoma posterior to the right kidney.
12. • Major renal injury. Posterior view of a volumetric 3D image shows
a renal split with the lower pole significantly displaced caudally.
Blood supply is maintained by an attenuated single vessel.
13. • CT of active renal haemorrhage. Multiple foci of active bleeding are seen in the centre of a large perinephric
haematoma displacing the kidney markedly anteriorly, indicating a high-pressure bleeding source. There is
haemorrhage in both the anterior and posterior pararenal spaces. The posterior portion of the kidney is lacerated.
14. • Subcapsular renal haematomas are rare, particularly
in older adults, as the renal capsule is not easily
separated from the cortex. In most cases the injury
will resolve without specific treatment, although
acute or delayed onset of hypertension from renal
parenchymal compression (Page kidney) should be
sought. Large subcapsular haematomas could
theoretically compress the kidney to near systolic
level pressures, preventing perfusion and requiring
surgical release of renal tamponade.
• Renal lacerations can be either superficial, involving
the cortex only, or deep, extending to the renal
medulla. Usually lacerations are self-limited injuries,
typically accompanied by small amounts of
perinephric haemorrhage.
15. • In blunt trauma the kidneys are displaced
outward toward the lateral aspect of the
retroperitoneum. This motion stretches the
intima beyond its elastic limit, leading to
dissection. Later, clot begins to form on and
around the disrupted intima, leading to partial
or complete occlusion of the renal artery.
• The artery usually occludes between the
proximal and middle third of the vessel
• Using contrast-enhanced spiral CT, the lack of
perfusion is obvious from the lack of
opacification, diminished size and (occasionally)
peripheral enhancement (rim sign) from
collateral vessels.
16. • Clinically significant renal vein disruption is
less common than injury to the renal artery.
It can produce extensive perinephric
bleeding, but as the venous pressure is low
this is usually limited in the retroperitoneum
17. • Injury to the renal pelvis is most likely to
result from hyperextension with secondary
overstretching of the pelvis. The injury
manifests as gross contrast/urine
extravasation near the pelviureteric junction.
• The injury can be missed on helical CT and
can mimic a duodenal rupture.
18. • Severe fragmentation of the renal
parenchyma usually requires surgical
treatment and typically results in
nephrectomy
