Kidney Trauma 112Jonathan Richenberg

Introduction

By 2020, it is estimated that 8.4 million people will die

from injury every year (Murray and Lopez 1997).

Trauma is the most common cause of death in the

United Kingdom in those under 40. In addition to

human cost, injury imposes a considerable economic

burden on Western countries – The Dutch spend 5% of

the health care budget on treating injury while motor

vehicle accidents alone consume 1.35% of the Spanish

gross national product (Alexandrescu et al. 2009). The

British Medical Association puts it more prosaically:

“for every injury death there are 45 hospital episodes,

630 doctor consultations and 5,000–6,000 minor inju-

ries” (British Medical Association 2001) (Table 112.1)

Trauma to the kidneys often occurs as part of more

widespread injury. The nature of the injury – collision,

gunshot, and so on – is usually manifest but not the

exact physical forces acting on the kidneys at the

time of trauma. Contrast-enhanced computed tomog-

raphy (CECT) is the key to diagnosing the injuries to

the viscera and their blood supply. Many trauma pro-

tocols are aimed at looking for liver or splenic damage

and can therefore miss or underestimate renal and

urothelial damage. This chapter will consider briefly

the forces that lead to renal injury and then stress the

optimal sequences and parameters for ensuring the

renal tract is adequately evaluated following trauma.

CECT appearances can be graded by severity, which

can together with clinical and laboratory parameters

direct management. Interventional radiology is central

in this management and is predicated on nephron-

sparing treatment. The role of angiography and embo-

lization is explored in the second half of the chapter.

Trauma Mechanisms in the Abdomen

Approximately 10–15% of abdominal injuries involve

the kidneys (and about one third involve the liver and

one third involve the spleen). Renal trauma may be

divided into the following.

Penetrating

This is usually an aggressive act, gunshot, or knife

attack, but may be accidental including falls on to

railings. The incidence in large European cities of

penetrating trauma is increasing, up to 25% in some

series of renal trauma (Smith et al. 2005), although

10% is a more representative proportion in most series

(Lee et al. 2007). Penetrating injuries tend to be serious

with vascular damage as well as parenchymal change.

Blunt

Eighty to ninety percent of renal trauma is due to blunt

forces, including road traffic accidents (two third blunt

trauma), violence (one fourth blunt trauma), and falls

(�one tenth), and crush injuries. In Europe, blunt

abdominal injury is still much more common than

penetrating trauma (this contrasts with South Africa

and some parts of the United States). Patients

sustaining blunt abdominal trauma die from shock.J. Richenberg

Brighton and Sussex University Hospitals, Brighton, UK

B. Hamm, P. R. Ros (eds.), Abdominal Imaging, DOI 10.1007/978-3-642-13327-5_230,# Springer-Verlag Berlin Heidelberg 2013

1779

Herein lies the power of radiology: the site of blood

loss can be identified by CT and stopped by interven-

tional radiology. No other specialty is so suited to

save victims of the aggression and violence and

pace of today’s world!

Forces

Dividing abdominal trauma into penetrating and blunt

is useful – to a point. In particular, for blunt injuries, it

is easy to underestimate the complexity and violence

of the forces acting on the viscera at the time of the

accident. Rarely do medical texts attempt a Physics

treatment of the mechanisms of trauma.

Isaac Newton’s second law of motion links accel-

eration (or more accurately deceleration in the case

of trauma) to force: blunt injuries combine shearing,

compressive, and rarefaction forces (with cavitation,

also seen in gunshot injuries). The forces act on

pivot points of the kidney – the pedicle, the

pelviureteric junction (PUJ), and the tissue interface

between the parenchyma and the urothelium. The

shearing forces in particular are important (Hallmann

et al. 1985). Add to this maelstrom of forces the possi-

ble impact of the kidneys on the thoracic spine, and it is

surprising that given the speed on many car collisions,

for example, there is not more renal trauma.

A key concept is that these forces act on the body as

a whole, so that any organ may be damaged (Khan

et al. 2006). Indeed, renal injury is reported in only 3%

of trauma patients (Baverstock et al. 2001).

Cushioning

A long pedicle means the kidneys are relatively

mobile, while perinephric fat and the psoas muscle

protect the kidneys, so deceleration forces and shear-

ing forces are more muted than on the liver and spleen.

These countermeasures become less effective if there

is a lesion in the kidney. Thus, a tumor adds mass, adds

rotatory movement, and reduces the distance that has

to be traveled before impact on immovable structures

such as the thoracic spine. This is an important and

somewhat complex concept and is developed further in

a separate section.

The idea of renal trauma rather than visceral trauma

is artificial. When large forces are involved – falls from

more than 2 m, crushing injuries, and many motor

vehicle accidents – assessment must concentrate on

the whole patient, imaging from top of skull to peri-

neum. Acknowledging that spinal, neurological, and/

or thoracic injuries may be more significant than

abdominal injury, systematic analysis of all the

abdominal and pelvic organs for injury is essential.

The key questions are the following: (1) How much

damage has been sustained altogether? (2) Which inju-

ries are immediately life threatening? Only then con-

sider (in the context of this chapter) these questions:

(a) Is there renal damage? (b) How extensive is the

renal damage?

Grading Renal Injury

In answer to the last question, in 2011, the American

Association for the Surgery of Trauma (AAST) pro-

posed a revision of the original 1989 renal organ injury

system (Buckley and McAninch 2011). The revision

expanded their existing grading system to include

segmental vascular injuries and ureteral pelvic injuries

and to establish a more rigorous definition of severe

grade IV and V renal injuries. The system is based

on CT findings; an “enhanced” version in this chapter

Table 112.1 Transport accident deaths in Europe (Union and

Zone) 2008–2009 as absolute number and as proportion of all

deaths in 16–34-year-olds

Transport accident deaths,

total number, 2006

Percentage of transport

accident deaths of all

deaths in the age group

15–34

Total Men Women Men Women

EU-27 49,688 37,860 11,828 26.5 16.4

EU-25 45,281 34,560 10,721 27.1 16.7

EA-15 29,862 22,776 7,086 29.9 17.9

EA-13 29,752 22,685 7,067 30.0 17.9

Source: Eurostat – Causes of death statistics (hlth_cd_anr),

Extraction date: 18.2.2008European UnionEU-27 The 27 Member States of the European Union

from1.1.2007

EU-25 The 25 Member States of the European Union

from1.5.2004 to 31.12.2006:

Euro areaEA-15 The euro area with 15 countries participating

from1.1.2008 to 1.1.2009

EA-13 The euro area with 13 countries participating

from1.1.2007 to 1.1.2008

1780 J. Richenberg

has summary of the CT findings next to each grade

(1–5); see right-hand column of Table 112.2. The

AAST injury scale for kidney predicts for morbidity

in blunt and penetrating renal injury and for mortality

in blunt injury (Buckley and McAninch 2011; Kuan

et al. 2006). Research suggests that decrease in kidney

function is directly correlated with AAST renal injury

grade (Tasian et al. 2010). In patients with grade 3

trauma or above, there is an 80% association with

other injuries (Baverstock et al. 2001).

Indications for Imaging in Renal Trauma

The major indications are set out in Table 112.3,

although the list is not exhaustive and every case

needs local expert input. A reasonable rule of

thumb is to err on the side of caution, with a low

threshold for definitive (CT) imaging. The absence

of hematuria does not exclude a renal lesion, and

hematuria in low-grade renal trauma does not guar-

antee a lesion visible on CT (Grill et al. 2010a;

Nguyen and Das 2002; Perez-Brayfield et al. 2002)

(Table 112.3).

Before dedicating the discussion in the remainder of

the chapter to CT, there will be a brief diversion into

other imaging modalities.

Ultrasound in Renal Trauma

Ultrasound has a role in low-grade renal injury – for

example, a low-velocity impact directly to the loin or

renal area. In a pediatric study, the diagnosis rate of

blunt renal trauma using ultrasonography (US) was

91% (c.f. IVU 82% and CT 100%).

The indications to image with ultrasound rather

than CT would be microscopic hematuria, posterior

abdominal wall, or loin bruising. Ultrasound is

sensitive in looking at subcapsular hematoma,

perinephric collections, free fluid, and some lacera-

tions. An injury to the renal parenchyma is indicated

by hypoechogenic areas of varying sizes in the renal

cortex. Perfusion can be graded to a point by Dopp-

ler, but segmental changes will not be as reliably

shown as on CT especially in the acute setting

(immobility, pain).

A negative ultrasound is no proof of the absence of

renal trauma (Grill et al. 2010b). Ultrasound is not

Table 112.2 Renal trauma grade based on revised American

Association for the surgery of trauma, with CT findings expected

for each grade

Grade Definition CT findings

I (80%) Hematuria with normal

imaging, contusions, or

nonexpanding

subcapsular hematoma

Normal

Focal areas reduced but

persistent enhancement

Hyperattenuating

subcapsular fluid, often

crescentic

II and III Perirenal hematoma

confined to renal

retroperitoneum

Ill-defined high-density

fluid between Gerota’s

fascia and parenchyma

Laceration <1 cm

parenchymal depth

of renal cortex (II)

or >1 cm (III) without

urinary extravasation

Low- to mid-density

parenchymal disruption

“Normal” urographic

phase

IV Renal laceration

involves collecting

system

Urine/contrast leak

Injury to main artery or

vein

Vascular leak or spasm

Segmental infarction Well-delineated

nonenhancing focal region

(s) of parenchyma

Subcapsular hematoma

compressing kidney

Perirenal hematoma

V Shattered kidney Extravasation, especially

medially

Complete detachment

PUJ

No enhancement

(sometimes a bit of cortex)

Devascularized kidney Filling defects, contrast

leakMajor laceration/

thrombus to vessels

Revised

grade

Definition CT findings

Buckley and McAninch

(2011)

IV Renal laceration

involves collecting

system

Urine/contrast leak

Segmental infarction Well-delineated

nonenhancing focal region

(s) of parenchyma

Subcapsular hematoma

compressing kidney

Perirenal hematoma

Shattered kidney Poor tissue planes

Complete detachment

PUJ

Extravasation, especially

medially

V Devascularized kidney No enhancement

(sometimes a bit of cortex)

Major laceration/

thrombus to vessels

Filling defects, contrast

leak

Kidney Trauma 1781

reliable in detecting small lacerations or urothelial dam-

age. In a study of 122 adults, US only managed to

identify grade 1 or 2 injury in 54%, and even in children

it cannot diagnose all grade I injuries (He et al. 2011).

Intravenous Urography

While excretory urography will highlight urothelial

leak, compared to CT, it is extremely limited, and it

seems reasonable to suggest that a patient with signif-

icant trauma should not be treated in a facility unable to

provide acute contrast-enhanced CT.

Renal MRI

There is no place for MRI in acute abdominal trauma,

as scan times are too long and patient access and

resuscitation are severely limited.

CT Technique

A two-part review of adult trauma (1996–1999

and 2000–2003) in Liverpool (UK) identified over

1,200 patients with abdominal injuries http://www.

biomedcentral.com/sfx_links?ui¼1471-2458-9-226&

bibl¼B5. A critical shift in management became appa

rent between the two study periods, with CT usage

rising 40% and reliance on diagnostic peritoneal lava

ge falling by 50% (Smith et al. 2005).

Phases

PrecontrastSome centers advocate this as an immediate investiga-

tion in severe trauma during the resuscitation phase,

with analysis and return for contrast-enhanced CT if

necessary. This seems to work where the patient can go

to CT directly from the ambulance, ideally being

scanned without transfer from the ambulance gurney.

Elsewhere, the patient usually is transferred from the

ambulance to a hospital trolley in the ER receiving

bay, and in these cases, subsequent transfer to CT.

In this situation, there will inevitably be plentiful intra-

venous access (lines for fluids) and the contrast

pump should have been prepared already, so the addi-

tional time of performing a contrast examination

on modern CT is minimal and precontrast CT is not

warranted.

Arterial Phase (20–25 s Postcontrast)In my opinion, this is a crucial phase in trauma to the

thorax, abdomen, or pelvis, as CT angiography may

identify active bleeding arterial points, as opposed to

hematoma or pooled blood. Recognizing these bleed-

ing points is an essential precursor to embolization or

surgical intervention.

The classic pattern of active extravasation is

a jet or focal area of hyperattenuation within

a hematoma that fades into an enlarged, enhanced

hematoma on later phase images. Distinction of con-

trast blush from bone fragments and dense foreign

bodies is usually possible by altering window settings

of the arterial-phase images on the workstation, for

example, looking on bone windows. Analysis of the

vessel or vascular supply to the kidneys often suggests

the bleeding point: dissection flap may be visible

(best appreciated on bone window settings), while

lack of vascular enhancement (caused by occlusion

or spasm) marks the proximal point of vessel damage.

The sentinel clot sign is an important clue for locating

the bleeding source when other more localizing find-

ings of vessel injury are not present (Hamilton

et al. 2008).

Portal Phase (60–70 s Postcontrast)Although this is not the most important phase in eval-

uating renal trauma, it is a crucial phase when seekingsubtle injuries to the liver and spleen. Modern CT

scanners with multiple detectors (32 and increasingly

64 detector platforms are commonplace) can easily

acquire arterial sequences from the head to perineum,

and then portal-phase abdomen, and the minimal addi-

tional radiation and time is justified by the improved

diagnostic information.

Table 112.3 Reasons to image the kidneys following trauma

(Lee et al. 2007; Shoobridge et al. 2011; Heyns 2004)

Blunt Penetrating injury

Hematuria (*absence of hematuria does notmean there is no significant renal injury)

Almost all cases

Shock (systolic BP <90 mmHg)

Polytrauma

Mechanisms including fall from > �2 m,

rapid declaration, crush injury

1782 J. Richenberg

Delayed or Urographic Phase (5–15 minPostcontrast)When there is (suspected) renal injury, delayed-phase

imaging is mandatory; without it, urothelial involve-

ment cannot be accurately assessed. Distinction

between grade 3 and grade 4 injuries becomes fraught.

On the other hand, keeping a patient with polytrauma

on the CT table for 5–10 min after portal-phase acqui-

sition may jeopardize the patient by inhibiting resus-

citation. Naturally, the time can be used to perform

initial reading of the images so far acquired, crucially

determining whether there is any life-threatening inter-

nal bleeding points, reviewing neurological imaging

where necessary, and looking at cervical spine and

dorsal spine reconstructions. Ultimately, the decision

to forego urographic imaging or to keep the patient on

the CT table must be made on a case-by-case basis. As

a helpful guide, provided the patient is not at danger of

imminent demise, imaging postcontrast at 10 min is

recommended, particularly in cases of:

• Hematuria

• Thoracic spine injury

• Pelvic injury

A suitable protocol is summarized in the left col-

umn of Table 112.4.

Adjunct TechniquesCystography using diluted contrast (4% w/v, say 10 ml

contrast in 240 ml normal saline) instilled into the

catheterized bladder before CT is useful in looking for

bladder injuries and/or type I urethral injury. The den-

sity of the contrast is sufficient for easy identification

of retroperitoneal or intraperitoneal (less common form

of bladder injury) leak, with distinction from hematoma

or even active bleeding points on the arterial-phase

images, but not too dense to induce beam hardening

artifact that detracts from the pelvic images.

Plain kidney-ureter-bladder X-ray (effectively

a delayed-phase film from the old IVU series) on return

of patient to the emergency department can be used as

a substitute to the much more informative delayed-

phase CT sequence when the patient’s unstable condi-

tion means that the delayed-phase CT is not safe. Of

course, a delayed-phase CT can always be postponed

so that a limited CT 15 min after contrast injection is

performed some hours or even days after the initial CT,

once the patient has been stabilized – for example,

critical hepatic bleeding embolized or extradural hema-

toma evacuated. When CT urography is postponed, the

severity of the renal injury can only be partially diag-

nosed, but often this translates to an uncertainty

between a grade 3 and grade 4 injury, and the vital

identification of severe vascular renal injury can be

made without the urographic-phase data.

One point is worth emphasizing here: even

acknowledging that CT is a high-radiation-dose tech-

nique, and noting that many trauma victims are young,

the radiation risks inherent in extended CT techniques

(that include additional phases) or inherent in repeat

CT examinations are small compared with risks in

underdiagnosing renal tract injury. Similarly, the “hot

topic” of contrast-induced nephropathy (CIN) is barely

relevant in acute trauma (and in any cases, IV hydra-

tion should be bountiful in these patients).

More Imaginative/Dedicated TraumaProtocolModifications include bolus of IV contrast 25 min

before the patient is stabilized, so that urographic

phase is inherent in the arterial-phase CT. The practical

limitations are however manifest, given the usual

intense activity when a polytrauma patient arrives at

hospital. Another modification beginning to be used in

Table 112.4 Protocols for renal CT following abdominal

trauma

CT conventional trauma

CT traumagram (after protocol

developed for military

casualties)

Multidetector CT recon

1.5–2 mm with workstation

reformation

Unenhanced head as required

Often head to perineum 150 ml contrast bolus. Split

into 100 ml at 1.6 ml/s

immediately followed by last

50 ml at 3.5 ml/s. This gives

a net contrast time of just over

70 s

Lung, bone, and soft tissue

windows

Scan starts at 70 s

Arterial phase: 25 s, 100 ml IV

nonionic CM 4 ml/s (25-s

injection)

Patient arms down

Urographic phase (5–10 min);

limited post-CT KUB X-ray

when this is not feasible

Scan from the circle of Willis

at least to the lesser trochanters

Cystogram (200 ml dilute CM

4% ¼ 8 ml in 190 ml normal

saline) if necessary

Provides CT artery chest,

portal venous abdomen, and

whole body arteriogram

Delayed-phase images at

10 min for urographic phase

Kidney Trauma 1783

trauma has been developed by the military at front-line

CT facilities and is summarized in the right-hand col-

umn of Table 112.4.

Imaging Findings of Renal Trauma

Renal Visceral Injuries

• Perirenal hematoma, Fig. 112.1

• Renal laceration, Figs. 112.2, 112.3, 112.5

• Subcapsular hematoma, Figs. 112.4, 112.5

• Urothelial injury, Fig. 112.6

• Shattered kidney, Fig. 112.7

Vascular Injuries

Complications include arterial thrombosis, venous

thrombosis, arterial pseudoaneurysms, or AV fistulae

(Elliott et al. 2007) (Fig. 112.8). Pedicle injuries may

involve venous as well as arterial (and pelviureteric)

structures, and are usually suggested by hematoma

between the aorta and the kidney. Complete lack of

parenchymal enhancement suggests pedicle injury

(grade 5) with renal artery occlusion. At the time of

impact, there is rapid stretching and then return of the

pedicle to normal which shears the intima and then dis-

section and occlusion occur. Segmental (wedge-shaped,

peripheral) absence indicates infarction due either to

emboli lodged in smaller vessels, intrarenal vascular inti-

mal injury, or preexisting damage. Rarely, there may be

bilateral enhancement limited to the outer cortex and

capsule, from unnamed capsular branches, without any

further renal contrast, and this “trumpets” severe hypo-

tension/shock (Saunders et al. 1995). A similar pattern of

cortical rim enhancement can be seen 8 or more hours

after renal devascularization as collateral perfusion from

perinephric vessels commences.

Management Based on Imaging

The principles guidingmanagement of any patient with

abdominal trauma, and especially when the abdominal

trauma is part of a wider injury pattern, are as follows:

• Keep patient alive.

• Do the least to achieve this, so that morbidity is

lower even in penetrating injury (Kent et al. 1993).

• Preserve function (in the context of this chapter,

renal function).

In renal injury, the decision for many years boiled

down to surgical vs. nonoperative management. With

the development of modern trauma centers, it has

become increasingly established that most grade 1–4

injuries can be treated conservatively, thus avoiding

unnecessary surgery (Baverstock et al. 2001; Simmons

et al. 2010). The widespread use of CT at the outset has

been a large factor in this change in practice. An

analysis of 271 blunt renal injury cases in 2010 iden-

tified (based on CT findings) three warning signs

(Table 112.5, left column) (Simmons et al. 2010);

this chimes with another study in 2010 confined to

102 patients with grade 4 injury (Dugi et al. 2010),

which concluded that key warning signs comprised

those in Table 112.5, right column.

Traditionally, surgery has been recommended for

(Lynch et al. 2005):

• Vascular (renal pedicle) injury

• Shattered kidney

• Expanding or pulsatile hematoma

• Shocked polytrauma patient

Interventional radiology would now challenge this

dogma. Surgical intervention aims to stem life-

threatening bleeding, but now most trauma centers

Fig. 112.1 Contrast-enhanced axial CT (CECT) of upper

abdomen in an adult knocked off a pedal bike by a car. Left

perirenal hematoma and liver laceration and spleen, managed

conservatively with good outcome

1784 J. Richenberg

recognize that interventional radiology can do this as

effectively, and with less stress to an already shocked

patient. As Prof. Karim Brohi from the Royal London

Hospital has written: “interventional radiology tech-

niques offer an opportunity to stop the bleeding. . . .[with the] advantage of avoiding the further trauma

that major surgery inevitably causes” (Intervention

Quarter issue 5, www.intervention-iq.org).

This attitude underpins most trauma centers, which

stress a team approach. Computed tomography findings

and CT angiographic findings are crucial in

distinguishing between those that can be managed

conservatively following blunt renal trauma and those

that should go to interventional angiography with embo-

lization if active bleeding point is identified. If perirenal

hematoma is less than 2.5 cm deep and there is no

vascular extravasation on arterial-phase CT, intervention

is not indicated (Charbit et al. 2011). The paper by

Charbit et al. in 2011 analyzed other CT findings in an

attempt to predict injuries that should be considered for

IR and those that can be managed conservatively

(Charbit et al. 2011). The analysis has limited value,

a bFig. 112.2 Axial CECT –

two adjacent levels in

a polytrauma patient

indicating laceration to left

kidney. Note also the spleen

tip injury (b). The grade of therenal injury cannot be

determined on these images

alone as the integrity of the

urothelium is unclear (not

delayed phase). There is no

active bleeding

Fig. 112.3 Axial CECT urographic phase, grade 2–3 injury as

the renal laceration is in parts just over 1 cm. The key points are

that there is no vascular or urographic extravasation

Fig. 112.4 Axial CECT – grade 3 injury of right kidney with

large subcapsular hematoma. Note the distinct margin and sharp

angle between the kidney and the blood indicating subcapsular

rather than perirenal collection (see Fig. 112.1). Deep laceration

but no urine leak. The kidney is viable, and there is no active

bleeding. The next day the patient had more pain, the hematoma

had expanded (not shown) due to continued venous leak, but by

2 weeks on conservative management, the symptoms had

resolved and the hematoma all but reabsorbed

Kidney Trauma 1785

and there is a risk of oversimplification, or thinking about

imaging findings in isolation. CT findings are critical but

they are a part of a more involved process, predicated on

a team comprising radiologists, surgeons, acute medical

care specialists, intensivists and nursing staff. The edito-

rial comment that follows the paper by Santucci captures

the sentiment perfectly: “Observation of most,

angioembolization of some, renorrhaphy of a few, and

nephrectomy of the absolute minimum are the desired

result” (Santucci 2011).

The US National Trauma Data Bank yields 9,000

cases of blunt and penetrating renal trauma

(2002–2007) in whom 2% underwent diagnostic angi-

ography, with 50% embolization rate; in many cases,

repeat embolization was necessary. Overall salvage

rate was 88% for grade 4 and 5 injury (Hotaling

et al. 2011a). Compare this with the surgical literature

which quotes that 9% of kidney injuries will require

surgical exploration, and of these there is on average

an 11% nephrectomy rate. Most nephrectomies are

for hemorrhage, and 61% of nephrectomies are for

a bFig. 112.5 Even with

extensive subcapsular

hematoma (a), conservativemanagement is justified, as

a CT at 2 weeks (done for

follow-up of other injuries in

this polytrauma patient)

attests. Note the grade 1 and 2

lacerations on (b) butotherwise well-perfused

kidneys. The subcapsular

hematoma had reabsorbed

Fig. 112.6 Axial delayed-phase CECT with contrast layering

between the parenchyma and the posterior renal capsule on the

left – grade 4

Fig. 112.7 Shattered kidney on CECT after fall from 10 m onto

the back. Grade 5 old version, grade 4 as pedicle intact on revised

AAST grading

1786 J. Richenberg

renovascular injury. Patients undergoing nephrectomy

tend to be more severely injured. Patients with minor

or moderate kidney injuries treated with exploration of

the kidney are more likely to develop local complica-

tions than those treated without exploration (Starnes

et al. 2010).

Interventional radiology outcomes tend, not

surprisingly to be better in trauma centers.

A retrospective analysis has been conducted of 186

adults with blunt renal trauma seen in a level 1 trauma

center, showing the benefit of interventional radiology

as an alternative to, or an adjunct to, open surgery, even

in patients with grade 4 and 5 injury. In 2009, success

rate for embolization in blunt renal trauma grade 4 and

5 was reported as over 94% (Chow et al. 2009). In

short, even management of grade 5 renal injuries with

percutaneous embolization is safe and is not associated

with intermediate-term adverse events (Stewart et al.

2010). A corollary of this is that Europe should strive

to establish a network of trauma centers with appropri-

ate IR equipment and expertise, and this as part of

a larger team (Hotaling et al. 2011b; Shoobridge

et al. 2011; van der Vlies et al. 2011; Ball et al. 2010)

(Figs. 112.9 and 112.10, Table 112.6).

Follow-up Imaging

For grade 3–5 injuries, a follow up CT at 48–72 hours

is often justified. A registry study from the West Coast

of America of 121 renal injuries in adults looked at

grade 4 and 5 renal trauma (Bukur et al. 2011). Almost

one third of the high-grade trauma had at least one

follow-up CT and for penetrating trauma this was

�40%. The imaging was prompted in all cases by

symptoms. While high-grade penetrating injuries

treated surgically should carry the highest degree of

vigilance and a readiness for repeat imaging, it seems

safe to adopt the motto: “No clinical indication, no

justification for routine follow-up imaging.” This is

true even more pertinently for higher-grade injuries

under conservative management. Routine reimaging in

patients with renal trauma outside the initial 48–72 h

window in the absence of a clear clinical indication

alters treatment in less than 1% (Davis et al. 2010).

The clinical warning signs include fever, hematoma,

and flank pain (Shirazi et al. 2010). See Table 112.7

for common complications following renal trauma.

The Preexisting Renal Abnormality

It is not uncommon for renal trauma and the subsequent

presentation to suggest an abnormality in the kidney(s)

that has led to disproportionate injury for described

mechanism. Of course, patients with known preexisting

congenital or acquired renal conditions may be injured

and suffer worse renal damage than “normal.”

a bFig. 112.8 Arterial-phase CT

17 days post blow to right

kidney, showing

a pseudoaneurysm. The

kidney and ureter had been

previously stented from below

(retrograde) for urine leak.

The arterial injury had not

been fully appreciated on the

initial CT assessment (a) andthe patient became troubled

with persistent clot colic and

macroscopic hematuria. This

prompted the follow-up CT

and subsequent angiography

and embolization (b)

Table 112.5 Warning signs on CT that conservative manage-

ment may need to be changed to include interventional percuta-

neous therapy including embolization or antegrade nephrostomy

and/or ureteric stent (After Simmons et al. (2010); Dugi et al.

(2010))

Pedicle injury Perirenal hematoma >3.5 cm

Artery thrombosis Intravascular contrast extravasation

Extravasation of urine Medial laceration >1 cm

Kidney Trauma 1787

When clinical symptoms or signs are out of keeping

with the assumed degree of trauma, it is worthwhile to

consider the following:

• Mechanism – Is this unequivocal? The energy

of the impact may be higher than initially

assumed. Reconsider the event, and perform

more rather than less CT phases. Moreover,

minor injury can cause major injury to the kidney

because of preexisting morbidity (congenital,

space-occupying lesion especially) (Vieira Abib

et al. 2011).

• Preexisting renal lesions including congenital

abnormalities and stones have been reported in up

to 16% of patients with blunt trauma to the kidneys

(El-Atat et al. 2011). Congenital conditions include

horseshoe kidney and ectopic kidneys.

• The association between renal tumors and trauma

should be suspected when renal trauma hemorrhage

on abdominal CT scan does not match the low-

energy mechanism of blunt abdominal trauma.

The key for a successful diagnosis of renal tumor

or congenital malformations is the high index

of suspicion for these conditions (Vieira Abib

et al. 2011) and thoughtful follow-up including

microbubble ultrasound looking for septal enhance-

ment or mural soft tissue, which may be very diffi-

cult to appreciate in a dense (posthemorrhage)

lesion on CT (Figs. 112.11 and 112.12)

Transplant Kidney

Injury to the transplant kidney is managed by the same

principles, but the following points are worth

emphasizing:

• Solitary functioning kidney, so emphasis on neph-

ron-sparing treatment all the more relevant.

• More susceptible than native kidneys to direct

trauma, so lower threshold for CT.

• Hematoma and other trauma complications more

likely to be complicated by infection because of

immunosuppression.

• Despite medic-alert bracelets, the presence of

a transplant kidney may be overlooked in the

polytrauma setting initially; CT should alert man-

aging team.

• More likely to have undergone biopsy, raising pos-

sibility of iatrogenic injury (Fig. 112.13).

Iatrogenic Trauma

This is usually penetrating trauma – biopsy or percu-

taneous access – and the complication is bleeding.

Bleeding may be periprocedure, delayed with hema-

toma formation and/or clot colic, or delayed onset with

shock/hematoma (pseudoaneurysm). CT angiography

is the initial preferred investigation, and any bleeding

a b c

Fig. 112.9 Selective left upper (a) and lower (b) renal angio-gram and (c) post embolization images from a dynamic inter-

ventional radiology run, acquired in a 42 year old following a

high speed car collision. The CT showed in this unstable patient

active bleeding from the lower half of the left kidney. The patient

went straight to angiography suite and the final image shows

control of the bleeding 10 min post embolization. The patient’s

condition improved markedly within minutes of deployment of

the last coil

1788 J. Richenberg

13000

11700

10400

9100

7800

6500

5200

3900

2600

1300

00

Minutes

Left Kidney

MAG3 Renogram (F@18 MIN AFTER START)

97

81

Left

73

89

Right KidneyLeft Uptake RegionRight Uptake RegionAortaBladder

Act

ivity

(co

unts

)

4 8

Left

Pea

k

Aor

tic P

eak

Left

T1/

2

Las1

x In

ject

Left

T1/

2 La

six

Rig

ht P

eak

12 16 20 24 28 32

a d

b

c

Fig. 112.10 Thirty-two-year-old female passenger in high-

speed car crash, struck from the left side (a). CT shows

devascularized right kidney with dissection and thrombus in

mid-part right renal artery. Angiography (delayed as patient

needed transfer to a specialist trauma center) confirmed

a short dissection and arterial stenosis, treated with balloon

dilation and stent (b and c). Note multiple infarcts of the

parenchyma on the post-stent angiogram (c). Unfortunately,

a MAG-3 renogram 4 weeks later showed an infarcted right

kidney despite the intervention; the poor outcome might have

been avoided had angiography and stenting occurred sooner

after the MVA

Table 112.6 Available interventional techniques in renal

trauma (left column) and the requirements for these to be avail-

able in the right column

IR techniques available for

renal tract injury Resource implications

Embolizing Integrated IR suite; CT in

emergency department

Stenting vessels Personnel

Stenting ureter Mind set

Draining collections Trauma center

Table 112.7 Complications following renal trauma (Santucci

et al. 2004)

Urine leak, which usually resolves spontaneously

Infected urine leak – this needs percutaneous drainage

Late hemorrhage – pseudoaneurysm, typically presenting

8–12 days post injury. Embolize

Hypertension secondary to compression of kidney by perirenal

hematoma (leading to rennin secretion) or following renal artery

stenosis in vascular injury (same rennin-based mechanism)

Potential for reduced renal function – suggest follow-up for

1 year; most deterioration is noted within 3–4 months

Kidney Trauma 1789

point is considered for percutaneous embolization,

especially pseudoaneurysm.

The other main iatrogenic renal trauma is due to

endourology, with urothelial disruption. In these cases,

the interventional radiologist often saves the day with

nephrostomy placement and/or antegrade ureteric stent

placement! (Fig. 112.14)

Isolated vascular injury at renal angioplasty is

a recognized complication of this procedure and

should be consented for and identified immediately.

Treatment is by balloon occlusion, then stenting and, if

necessary, surgery.

Pediatric Renal Trauma

The philosophy for pediatric trauma is no different to

that described above (Fitzgerald et al. 2011). The

absence of hematuria does not exclude significant

injury and the decision to image must be based on

clinical history and examination, including velocity

of trauma, injury pattern, and the need to bear in

mind the possibility of congenital abnormality

predisposing to more severe injury.

Abdominal CT scanning is the most accurate

screening test for high-grade injuries in children (He

et al. 2011; Nerli et al. 2011). In serious pediatric

renal injuries, early detection and staging based on

clinical presentation and computerized tomography

are critical for determining operative vs. nonoperative

management (Buckley and McAninch 2004, 2006).

Likewise, conservative management is the first

choice for all grades of hemodynamically stable chil-

dren with blunt renal trauma, even those with grade 4

and grade 5 injuries (Nerli et al. 2011), and nephrec-

tomy rates can and should be kept under 2% (Buckley

and McAninch 2004, 2006; Rogers et al. 2004).

Grade 5 injuries, not surprisingly, do worst, and sur-

gical intervention including nephrectomy is limited

more or less to this subgroup (Mohamed et al. 2010).

In due course, as pediatric interventional radiology

comes of age, it is hoped that renal preservation will

be even more prevalent among the pediatric renal

injuries.

a b

c d

Fig. 112.11 Thirty-two-

year-old presented 2 days after

fall from stool with severe

right flank pain and bruising

and fever. CT done for the

fever and bruising shows thick

walled soft tissue mass arising

from the right kidney (a) with

aberrant vessel on posterior

inferior wall (bright density,b).There was however no

enhancement on arterial or

delayed phase images (not

shown). In view of the fever, a

percutaneous drain was sited

under US guidance in the

interventional radiology suite

(c), in case fresh bleeding

necessitating embolization

was provoked. A couple of

100mls of old blood drained.

On follow up CT, the soft

tissue mass remained,

unchanged in size, but no

longer with opacification of

mural vessel (d). Working

diagnosis bleed in to an

infarcted tumour

1790 J. Richenberg

There are, nevertheless, some differences between

the adult and pediatric populations relating to renal

injury:

• Renal injuries caused by blunt abdominal trauma

are common in children.

• Major kidney insult can occur after a minimal blunt

trauma localized to the flank or upper abdomen

(Rathaus et al. 2004).

• Although no evidence on short-term follow-up, it

seems sensible to follow up children with grades 4

a b c

Fig. 112.12 Fifty-eight-year-old woman knocked over by an

enthusiastic dog, becoming quickly shocked and collapsing with

left pain an hour later. A pretrauma MRI (a) shows a large leftanterior renal angiomyolipoma (AML). A CT on admission 4 h

after being knocked over (not shown) confirmed a large and

active bleed into the AML; as the patient was actively bleeding

and hypotensive, she was transferred to IR. Angiography iden-

tified active bleeding point (b), which was successfully coiled.

Further coils were placed in a second inferior pole AML as

a precautionary measure in the same procedure (c)

a b

c

Fig. 112.13 Ultrasound (B mode and color Doppler) of a transplant kidney. There is a post-biopsy upper pole AV fistula with

intense and chaotic color flow

Kidney Trauma 1791

or 5 injuries, and especially when surgery or radiol-

ogy intervention has been necessary, for renal func-

tion and blood pressure for up to 5 years postinjury.

The ESPR uroradiology task force and ESUR pedi-

atric working group have published guidance based

on children with major and children with mild to mod-

erate urinary tract imaging. CT is recommended as

the best investigation for renal trauma, but US is

given more prominence than in adult renal trauma

(Riccabona et al. 2011).

Conclusions

Renal damage may be part of multiple injuries

(polytrauma) and, in these cases, is rarely the most

immediately life-threatening problem. Computed

tomography, with multiple phases, allows the renal

injury to be graded which in turn can help determine

management and prognosis. Most injuries can be man-

aged conservatively and follow-up imaging arranged

only when there are clinical signs of a complication.

When there is high-grade injury and specifically active

arterial bleeding, angiography and embolization

should be considered in preference to open surgery.

Congenital abnormalities or mass lesions (previously

discovered or not) can mean that low-impact trauma can

lead to serious renal injury. Interventional radiology is

emerging as promising treatment in these cases too.

The modern world is a dangerous place, becoming

decade by decade faster, more crowded, and more

violent. Medics need to press for dedicated trauma

services and the establishment of trauma centers across

Europe where teams including skilled diagnostic and

a b c

d e

Fig. 112.14 Disruption of the right pelviureteric junction at the

time of attempted endourological retrieval of stones. The proce-

dure was very difficult because of a tortuous ureter previously

reimplanted into a neobladder/ileal conduit. The patient

complained of immediate and severe pain (PUJ disruption

in (a) and (b), by ureteroscope). Percutaneous nephrostomy

placed (c) in interventional radiology, and the pain settled. In

the process of stenting the ureter, the stone was dislodged into

the conduit. Post-stent CT shows (d and e) nephrostomy, stent

with adjacent periureteric resolving collection secondary to the

PUJ trauma, and the conduit containing stone debris and a Foley

catheter

1792 J. Richenberg

interventional radiologists can improve outcomes fol-

lowing trauma in such a frantic world.

New Paradigm

• CT in A&E – Resuscitation algorithm: A,B, CT

• Sequences: Arterial phase, delayed phase if urologi-

cal trauma suspected. Proper coverage – neck as

standard

• Access to read in multiple sites but better still at

high-quality monitors with senior clinicians

• IR – As part of polytrauma. Percutaneously embolize

or open up/stent vessels in cases of dislocation or

stent if dissection

• Follow-up imaging: later complications – Drainage

of collections, managing ARDS; DVT and PE.

Reintervention

• Follow-up imaging when there is concern about

pretrauma pathology (brought to light because of

injury)

References

Alexandrescu R, O’Brien SJ, Lecky FE. A review of injury

epidemiology in the UK and Europe: some methodological

considerations in constructing rates. BMC Public Health.

2009;9:226. doi:10.1186/1471-2458-9-226.

Ball CG, Feliciano DV, Mattox KL. Combined splenectomy and

nephrectomy for trauma: morbidity, mortality, and outcomes

over 30 years. J Trauma. 2010;68(3):519–21. doi:10.1097/

TA.0b013e3181cda28d.

Baverstock R, Simons R, McLoughlin M. Severe blunt renal

trauma: a 7-year retrospective review from a provincial

trauma centre. Can J Urol. 2001;8(5):1372–6.

British Medical Association. Injury prevention. London: British

Medical Association; 2001.

Buckley JC, McAninch JW. Pediatric renal injuries: manage-

ment guidelines from a 25-year experience. J Urol. 2004;

172(2):687–90. doi:10.1097/01.ju.0000129316.42953.76.

discussion 690.

Buckley JC, McAninch JW. The diagnosis, management, and

outcomes of pediatric renal injuries. Urol Clin North Am.

2006;33(1):33–40. doi:10.1016/j.ucl.2005.11.001. vi.

Buckley JC, McAninch JW. Revision of current American Asso-

ciation for the surgery of trauma renal injury grading system.

J Trauma. 2011;70(1):35–7. doi:10.1097/TA.0b013e318207

ad5a.

Bukur M, Inaba K, Barmparas G, et al. Routine follow-up imag-

ing of kidney injuries may not be justified. J Trauma.

2011;70(5):1229–33. doi:10.1097/TA.0b013e3181e5bb8e.

Charbit J, Manzanera J, Millet I, et al. What are the specific

computed tomography scan criteria that can predict or

exclude the need for renal angioembolization after

high-grade renal trauma in a conservative management

strategy? J Trauma. 2011;70(5):1219–27. doi:10.1097/

TA.0b013e31821180b1. discussion 1227–1218.

Chow SJ, Thompson KJ, Hartman JF, Wright ML. A 10-year

review of blunt renal artery injuries at an urban level

I trauma centre. Injury. 2009;40(8):844–50. doi:10.1016/j.

injury.2008.11.022.

Davis P, Bultitude MF, Koukounaras J, Royce PL, Corcoran

NM. Assessing the usefulness of delayed imaging in routine

followup for renal trauma. J Urol. 2010;184(3):973–7.

doi:10.1016/j.juro.2010.04.070.

de Vieira Abib SC, Leite MT, Ribeiro RC, et al. Renal tumor and

trauma: a pitfall for conversative management. Int Braz

J Urol. 2011;37(4):514–8.

Dugi 3rd DD,Morey AF, Gupta A, Nuss GR, Sheu GL, Pruitt JH.

American Association for the surgery of trauma grade 4 renal

injury substratification into grades 4a (low risk) and 4b (high

risk). J Urol. 2010;183(2):592–7. doi:10.1016/j.

juro.2009.10.015.

El-Atat R, Derouiche A, Slama MR, Chebil M. Kidney trauma

with underlying renal pathology: is conservative manage-

ment sufficient? Saudi J Kidney Dis Transpl.

2011;22(6):1175–80.

Elliott SP, Olweny EO, McAninch JW. Renal arterial injuries:

a single center analysis of management strategies and out-

comes. J Urol. 2007;178(6):2451–5. doi:10.1016/j.

juro.2007.08.002.

Fitzgerald CL, Tran P, Burnell J, Broghammer JA, Santucci R.

Instituting a conservative management protocol for pediatric

blunt renal trauma: evaluation of a prospectively maintained

patient registry. J Urol. 2011;185(3):1058–64. doi:10.1016/j.

juro.2010.10.045.

Grill R, Maskova V, Ryantova V, Urban M. Low-grade renal

trauma (part I): diagnostic validity of haematuria. Acta Chir

Orthop Traumatol Cech. 2010a;77(1):43–5.

Grill R, Baca V, Otcenasek M, Zatura F. Low grade renal trauma

(Part II): diagnostic validity of ultrasonography. Acta Chir

Orthop Traumatol Cech. 2010b;77(2):140–2.

Hallmann B, Schulze H, Ruttloff J, Beuthan J. Uniform theory

on the pathomechanism of closed renal stalk injuries–-

subpelvic ureteral ruptures and kidney vascular stalk lesions.

Z Urol Nephrol. 1985;78(8):409–17.

Hamilton JD, Kumaravel M, Censullo ML, Cohen AM, Kievlan

DS, West OC. Multidetector CT evaluation of active extrav-

asation in blunt abdominal and pelvic trauma patients. Radio-

graphics. 2008;28(6):1603–16. doi:10.1148/rg.286085522.

He B, Lin T, Wei G, He D, Li X. Management of blunt renal

trauma: an experience in 84 children. Int Urol Nephrol.

2011;43(4):937–42. doi:10.1007/s11255-011-9965-2.

Heyns CF. Renal trauma: indications for imaging and surgical

exploration. BJU Int. 2004;93(8):1165–70. doi:10.1111/

j.1464-410X.2004.04868.x.

Hotaling JM, Sorensen MD, Smith 3rd TG, Rivara FP, Wessells

H, Voelzke BB. Analysis of diagnostic angiography and

angioembolization in the acute management of renal trauma

using a national data set. J Urol. 2011a;185(4):1316–20.

doi:10.1016/j.juro.2010.12.003.

Hotaling JM, Wang J, Sorensen MD, et al. A national study of

trauma level designation and renal trauma outcomes. J Urol.

2011b. doi:10.1016/j.juro.2011.09.155.

Kidney Trauma 1793

Kent AL, Jeans P, Ewards JR, Byrne PD. Ten year review of

thoracic and abdominal penetrating trauma management.

Aust N Z J Surg. 1993;63(10):772–9.

Khan JS, Iqbal N, Gardezi JR. Pattern of visceral injuries fol-

lowing blunt abdominal trauma in motor vehicular accidents.

J Coll Physicians Surg Pak. 2006;16(10):645–7. doi:10.2006/

JCPSP.645647.

Kuan JK, Wright JL, Nathens AB, Rivara FP, Wessells H.

American Association for the surgery of trauma organ injury

scale for kidney injuries predicts nephrectomy, dialysis, and

death in patients with blunt injury and nephrectomy

for penetrating injuries. J Trauma. 2006;60(2):351–6.

doi:10.1097/01.ta.0000202509.32188.72.

Lee YJ, Oh SN, Rha SE, Byun JY. Renal trauma. Radiol

Clin North Am. 2007;45(3):581–92, ix doi: 10.1016/j.

rcl.2007.04.004.

Lynch TH, Martinez-Pineiro L, Plas E, et al. EAU guidelines on

urological trauma. Eur Urol. 2005;47(1):1–15. doi:10.1016/j.

eururo.2004.07.028.

Mohamed AZ, Morsi HA, Ziada AM, et al. Management

of major blunt pediatric renal trauma: single-center experi-

ence. J Pediatr Urol. 2010;6(3):301–5. doi:10.1016/j.

jpurol.2009.09.009.

Murray CJ, Lopez AD. Alternative projections of mortality and

disability by cause 1990–2020: global burden of disease

study. Lancet. 1997;349(9064):1498–504. doi:10.1016/

S0140-6736(96)07492-2.

Nerli RB, Metgud T, Patil S, et al. Severe renal injuries in

children following blunt abdominal trauma: selective man-

agement and outcome. Pediatr Surg Int. 2011;27(11):

1213–6. doi:10.1007/s00383-011-2908-2.

Nguyen MM, Das S. Pediatric renal trauma. Urology.

2002;59(5):762–6. discussion 766–767.

Perez-Brayfield MR, Gatti JM, Smith EA, et al. Blunt traumatic

hematuria in children. Is a simplified algorithm justified?

J Urol. 2002;167(6):2543–6. discussion 2546–2547.

Rathaus V, Pomeranz A, Shapiro-Feinberg M, Zissin R. Isolated

severe renal injuries after minimal blunt trauma to the upper

abdomen and flank: CT findings. Emerg Radiol. 2004;

10(4):190–2. doi:10.1007/s10140-003-0308-1.

Riccabona M, Lobo ML, Papadopoulou F, et al. ESPR

uroradiology task force and ESUR paediatric working

group: imaging recommendations in paediatric uroradiology,

part IV: Minutes of the ESPR uroradiology task force mini-

symposium on imaging in childhood renal hypertension and

imaging of renal trauma in children. Pediatr Radiol.

2011;41(7):939–44. doi:10.1007/s00247-011-2089-0.

Rogers CG, Knight V, MacUra KJ, Ziegfeld S, Paidas CN,

Mathews RI. High-grade renal injuries in children–is conser-

vative management possible? Urology. 2004;64(3):574–9.

doi:10.1016/j.urology.2004.04.069.

Santucci R. Editorial comment. J Trauma. 2011;70(5):1227–8.

Santucci RA, Wessells H, Bartsch G, et al. Evaluation and

management of renal injuries: consensus statement of the

renal trauma subcommittee. BJU Int. 2004;93(7):937–54.

doi:10.1111/j.1464-4096.2004.04820.x.

Saunders HS, Dyer RB, Shifrin RY, Scharling ES, Bechtold RE,

Zagoria RJ. The CT nephrogram: implications for evaluation

of urinary tract disease. Radiographics. 1995;15(5):1069–85.

discussion 1086–1068.

Shirazi M, Sefidbakht S, Jahanabadi Z, Asadolahpour A,

Afrasiabi MA. Is early reimaging CT scan necessary in

patients with grades III and IV renal trauma under conserva-

tive treatment? J Trauma. 2010;68(1):9–12. doi:10.1097/

TA.0b013e3181ad5835.

Shoobridge JJ, Corcoran NM, Martin KA, Koukounaras J,

Royce PL, Bultitude MF. Contemporary management of

renal trauma. Rev Urol. 2011;13(2):65–72.

Simmons JD, Haraway AN, Schmieg Jr RE, Duchesne JD. Blunt

renal trauma and the predictors of failure of non-operative

management. J Miss State Med Assoc. 2010;51(5):131–3.

Smith J, Caldwell E, D’Amours S, Jalaludin B, Sugrue M.

Abdominal trauma: a disease in evolution. ANZ J Surg.

2005;75(9):790–4. doi:10.1111/j.1445-2197.2005.03524.x.

Starnes M, Demetriades D, Hadjizacharia P, Inaba K, Best C,

Chan L. Complications following renal trauma. Arch Surg.

2010;145(4):377–81. doi:10.1001/archsurg.2010.30. discus-

sion 381–372.

Stewart AF, Brewer Jr ME, Daley BJ, Klein FA, Kim ED.

Intermediate-term follow-up of patients treated with

percutaneous embolization for grade 5 blunt renal

trauma. J Trauma. 2010;69(2):468–70. doi:10.1097/

TA.0b013e3181e5407a.

Tasian GE, Aaronson DS, McAninch JW. Evaluation of renal

function after major renal injury: correlation with the Amer-

ican Association for the surgery of trauma injury scale.

J Urol. 2010;183(1):196–200. doi:10.1016/j.juro.2009.08.

149.

van der Vlies CH, Olthof DC, van Delden OM, et al. Manage-

ment of blunt renal injury in a level 1 trauma centre in view of

the European guidelines. Injury. 2011. doi:10.1016/j.

injury.2011.06.034.

1794 J. Richenberg