An Article By

Dr. Ahmed Esawy

MBBS M.Sc MD

Trauma to the abdomen

accounts for approximately 10% of the

traumatic deaths. Prompt recognition and

management of bleeding from intra-

abdominal organs is essential to

minimize morbidity and mortality from

trauma itself as well as minimizing the

need of surgical interference with

probable its complications.

Classification of Abdominal Trauma:

A. Blunt Abdominal Trauma (BAT):

- Compression or concussive forces (direct blows)

- Deceleration forces

• B. Penetrating Abdominal Trauma (PAT):

- High-velocity injuries (gunshots)

- Low-velocity penetrating injury (stab wounds)

Imaging Techniques:

1- Initial imaging:-

- FAST

- Plain X-ray

2- CT

3-conventional Angiography

4- MRI

5- Isotope Scan

The primary role of CT is to assess

the severity of abdominal injuries

in order to help the trauma

surgeon to decide if emergent

surgery is necessary.

Therefore, if surgery is mandatory

due to the severity of the

abdominal trauma, then CT is

generally avoided.

IN INTERPRETING CT FOR

PATIENTS WITH

ABDOMINAL TRAUMA, WE

HAVE TO SCREEN FOR

1) Pneumothorax and pneumoperitoneum using

lung windows for lower thorax and upper abdominal sections

and soft tissue windows for lower abdominal and pelvic

sections;

(2) left paracolic gutter

and spleen for blood

or laceration

(3) right paracolic

gutter and liver, for

blood or laceration

(4) upper abdominal

survey evaluating

duodenum and pancreas

(5) Retroperitoneal survey of

kidneys, adrenals, IVC and

aorta for evidence of

bleeding, laceration,

hematoma, urinoma

(6) GI tract and

mesentery for

extravasation or

hematoma

(7) muscle survey including

psoas,

iliopsoas,

rectus abdominus

and buttocks for hematoma

(8) bone survey including

ribs,transverse processes, sacrum, and

SI joints

and hips

for fracture

(9) lowest section search for groin

hematoma

BAT

FAST

Positive FAST Negative FAST

Stable Patient Unstable Patient Stable Patient Unstable Patient

CT Laparotomy Repeat FAST after 6 hrs Identify other cause

APPROACH FOR ABDOMINAL

TRAUMA

Abdominal Trauma Protocol

• Blunt injury -deceleration, crush, weapon

(e.g. bat)

– venous phase ~70 secs

– Delayed scan if injury present; ~3-5 mins

• Penetrating injury: knives, gun

– Same as blunt

– Additional scan after rectal contrast material

• The findings to look for in abdominal trauma are the following:

– Hemoperitoneum

– Pneumoperitoneum

– Contrast blush consistent with active extravasation

– Subcapsular hematomas

– Laceration

– Contusions

– Devascularization of organs or parts of organs

Active bleeding

The CT appearance of

intraperitoneal blood

depends on the age

and physical state of

the clot.

IMMEDIATELY AFTER

HEMORRHAGE,

INTRAPERITONEAL BLOOD

HAS THE SAME

ATTENUATION AS

CIRCULATING BLOOD OF

20-30 HU

Active bleeding

However, attenuation values less than 20 HU are

a frequent finding in the acute setting. The

proposed reason for this is that blood, being

a strong peritoneal irritant, causes a local

inflammatory response with transudation of

fluid across the peritoneum. Transudate fluid

mixes with and dilutes the blood before

coagulation begins, decreasing the attenuation.

Active bleeding

Within hours, a clot forms and attenuation increases as hemoglobin concentrates, and values in the range of 50-75 HU are seen. Densely clotted blood may have attenuation values upwards of 100 HU.

Clot lysis begins within 48-72 hours, and attenuation decreases to fluid values.

After a few weeks, most hematomas have attenuation values approaching those of water,

namely, 0-20 HU.

Active bleeding

In reality, hemoperitoneum can have a complex

appearance as a result of recurrent

hemorrhage and irregular resorption. Blood

may exist in many different stages at the time

of imaging if hemorrhage has been intermittent.

Fresh blood

confined to a localized space or that has been

relatively undisturbed may separate,with

plasma layered on top of precipitated red blood

cells causing the hematocrit effect.

Quantification of hemoperitoneum

Huang and associates scoring systems

• Total Score ranging from 0 to 8

• One point was assigned to each anatomic

site in which free fluid was detected during

the FAST scan

• Fluid of more than 2 mm in depth in the

hepatorenal or the splenorenal space was

given 2 points instead of 1

• Floating loops of bowel were given 1 point

• Scores > 3 required exploratory laparotomy

Approximately

• FAST can detect between 100-250ml

0.5 cm in Morison's Pouch = 500ml

1 cm in Morison's Pouch = 1000ml

CT can detect volumes of free fluid as

low as 100ml

Volume

• Detection of fluid in each paracolic

gutter indicates that at least 200 ml of

blood must be present in each gutter.

• CT visualization of blood in the

abdomen and pelvis corresponds with

the amounts of more than 500 ml.

Hemoperitoneum Hyperdense intraperitoneal fluid collection

0–20HU

Preexisting ascites

Bile

Urine

Digestive fluid

Diluted (acute blood) or old blood

30–45HU Free Unclotted intraperitoneal blood

45–70HU Clotted blood/sentinel clot sign hematoma

>100 HU Extravasation of contrast medium

(vascular or urinary)

SENTINEL CLOT SIGN

• Clotted blood adjacent to

the site of injury is of higher

attenuation value than

unclotted blood which

flows away .

• When the source of

intraperitoneal bleed not

evident, the location of

highest attenuating blood

clot is a clue to the most

likely source

Ascites – Radiographic findings

• Obliteration of inferior edge of liver

• Widening of distance b/n flank stripe &asding colon

• AF b/n liver & lateral abd wall may result in visualization of a lucent band –Hellmer’s sign

• Dog ear sign or ‘Mickey mouse ears’ sign(100-

150ml)- fluid density lateral to rectal gas shadows.

• Separation and floating of bowel loops

• Bulging properitoneal flank stripe

• Poor definition of major abd. organs and psoas

• Overall abdominal haziness

Retroperitoneal Hemorrhage

• Retroperitoneal hemorrhage may

arise from injuries to major vascular

structures, hollow viscera, solid

organs, or musculoskeletal

structures or a combination

Small zone I (central)

retroperitoneal hematoma

Large zone I (central)

retroperitoneal hematoma with

active extravasation

Large zone II (lateral)

retroperitoneal hematoma

The CT appearance of intraperitoneal blood depends on the age and physical state of

the clot.

Active bleeding

IMMEDIATELY AFTER HEMORRHAGE,

INTRAPERITONEAL BLOOD HAS THE SAME

ATTENUATION AS CIRCULATING BLOOD OF

20-30 HU

However, attenuation values less than 20 HU

are a frequent finding in the acute setting. The

proposed reason for this is that blood, being

a strong peritoneal irritant, causes a local

inflammatory response with transudation of

fluid across the peritoneum. Transudate fluid

mixes with and dilutes the blood before

coagulation begins, decreasing the

attenuation.

Active bleeding

Within hours, a clot forms and attenuation increases as hemoglobin concentrates, and values in the range of 50-75 HU are seen. Densely clotted blood may have attenuation values upwards of 100 HU.

Clot lysis begins within 48-72 hours, and attenuation decreases to fluid values.

After a few weeks, most hematomas have attenuation values approaching those of water,

namely, 0-20 HU.

Active bleeding

In reality, hemoperitoneum can have a complex appearance as a result of recurrent hemorrhage and irregular resorption. Blood may exist in many different stages at the time of imaging if hemorrhage has been intermittent. Fresh blood

confined to a localized space or that has been relatively undisturbed may separate,with plasma layered on top of precipitated red blood cells causing the hematocrit effect.

Active bleeding

CT findings of shock

• Collapse of inferior vena cava

• Small aorta

• Persistent nephrogram without excretion

• Hypodense spleen, without enhancement and

normal vascular pedicle

• Increased enhancement of the small bowel wall

• Increased enhancement of the adrenal glands

• Sometimes findings of right cardiac insufficiency

with reflux into the hepatic veins

PNEUMOPERITONEUM

• FREE AIR SENSITIVITY OF IMAGING

STUDIES – COMPUTED TOMOGRAPHY- 99%

– AP UPRIGHT CHEST RADIOGRAPH - 76%

– LEFT DECUBITUS ABDOMEN RADIOGRAPH 80 -90%

– SUPINE ABDOMEN RADIOGRAPH - 56%

Signs of a pneumoperitoneum on the supine

radiograph

Right upper quadrant gas

Perihepatic

Subhepatic

Morrison’s pouch

Fissure for the ligamentum teres

Rigler’s (double wall) sign

Ligament visualization

Falciform (ligamentum teres)

Umbilical (inverted V sign) medial and lateral

Urachus

Triangular air

The cupola sign

Football or air dome

Scrotal air (in children)

SOLID ORGAN INJURY

Solid organ injury includes:

- liver, spleen and kidneys.

- Injury of the urinary bladder.

- Bowel and mesenteric injury.

- Pancreatic injury.

-Injury to the abdominal aorta.

- Diaphragmatic rupture.

- Pelvic trauma.

On CT, it is usually seen in a lenticular configuration. Sub-capsular hematomas cause direct compression and deformity of the shape of the underlying solid organs. On non-enhanced CT scans, the solid organs appear hypo-attenuating compared with a sub-capsular hematoma. On enhanced CT scans, a sub-capsular hematoma appears as a low-attenuating lenticular collection between the capsule and the enhancing parenchyma of the injured organ. Unless bleeding recurs, attenuation of the sub-capsular hematoma decreases with time. Sub-capsular hematomas resolve within 6-8 weeks

Subcapsular hematoma

On enhanced CT, laceration appears as a non-enhancing linear or branching structure, usually at periphery. Acute lacerations have a sharp or jagged margin, but with time, lacerations may enlarge, and the margins may develop rolled edges. Multiple parallel lacerations occur as result of compressive forces (bear claw lacerations).

Lacerations:

contusions are perceived as ill-defined

or sometimes sharply marginated

areas of reduced enhancement and

excretion

On enhanced CT, acute hematomas appear as irregular high-attenuation areas,which represent clotted blood, surrounded by low-attenuating unclotted blood. Over time, the attenuation of the hematoma is reduced, and the hematoma eventually forms a well-defined serous fluid collection that may expand slightly. A focal intraparenchymal hyper attenuating area with attenuation of 80-350 HU may represent an

active hemorrhage or pseudo-aneurysm. .

Intra-parenchymal hematomas