Body CT ���for Emergency Physicians

Rathachai Kaewlai, MD Division of Emergency Radiology Department of Radiology, Ramathibodi Hospital, Bangkok, Thailand Annual Conference of Thai Emergency Physicians (ACTEP) 25 Nov 2015 at the Regent Cha-am Beach Resort, Cha-am, Petchaburi, Thailand

Outline

About emergent body CT

Vascular occlusion Aneurysm/pseudoaneurysm Bleeding and active contrast extravasation

Extraluminal air

CT Contrast: Update

Post contrast acute kidney injury (PC-AKI)

Creatinine change in 48 hours after IV contrast Various etiologies: physiologic variation, drugs, CM

Contrast induced nephropathy (CIN)

Subset of PC-AKI Exists but likely rare, unknown prevalence

eGFR more commonly used than serum creatinine

CT Contrast: Update

21346 patients undergone CT, half received IV contrast 1:1 matched on propensity score yielding similar demographics and comorbidities

Radiology December 2014

IV Contrast: When?

Chest: most emergent indications

Abdomen: most emergent indications except ureteric stone, R/O AAA rupture, R/O free air

CTisUS.com

Oral Contrast: When?

Generally not recommended in ER setting except for

Penetrating abdominal trauma Suspected GI fistula, postoperative leakage Suspected esophageal perforation

Take time (1-2 hours) Value questioned even in suspected bowel perforation

Role of “limited” oral contrast?

emrap.org

Rectal Contrast: When?

Generally not recommended in ER setting except for:

Penetrating abdominal trauma Suspected GI fistula, postoperative leakage

May be used in

Suspected appendicitis esp in children

Workflow and job issue

Patient discomfort

oakmed.co.uk

Timing of Acquisition: ���What & Why? NCCT

CTA arterial venous

delayed

ARTERIAL VENOUS

CTA

Scan Coverage: CTA Aorta

Whole aorta

R/O dissection (assess extent) R/O aortic aneurysm w/o prior imaging (potential coexisting aneurysms)

One part OK R/O AAA rupture F/U known aneurysm

Scan Coverage: CTA for PE

With lower extremity (LE) CTV

Older patients No worry on volume of IV contrast (kidneys, CHF)

Without LE CTV Younger patients

Do Doppler (similar accuracy as CTV)

ehumanbiofield.wikispaces.com

Scan Coverage: Abdominal CT

Most ER indications ! whole abdomen Pancreatitis

Colon problems Upper abdomen:

Hepatobiliary problems

Lower abdomen: Appendix KUB: Stone protocol

Scan Coverage: Multiphase CT

Should avoid in young patients (<45 years)

For most ER indications, venous phase is enough Pretty much depending on your radiologists’ level of comfort and experience

Required for Bowel ischemia

Characterization of masses or suspected masses

Scan Coverage: Non-contrast

Do we always need non-contrast before giving IV CM?

No! Most people worries that IV contrast will obscure

blood and Ca2+, it’s partly true BUT we can still diagnose blood and dense Ca2+ on post-contrast CT

We do this if it is multiphase scan

Bowel ischemia Characterization of masses or suspected masses

NCCT Only

eGFR <30 without dialysis unless risk accepted by referring physician and patient

Acute flank pain

R/O AAA rupture May need IV contrast if patient’s conditions allow

R/O free air Looking for lung lesions, bone lesions

Scan Coverage: Trauma CT

Trauma CT is different than other CTs

Coverage: torso coverage in abdominal trauma Arterial phase necessary: active contrast extravasation

No need for non-contrast phase Reduced radiation dose because many trauma victims

are young (higher risk of radiation-induced cancers)

Approach to CT Interpretation

Clinical question first ! look for pathology suspected

Then ! systematic review of images Check blind spots of each exam

(Knowing body anatomy is a prerequisite!)

Critical CT Findings

Vascular occlusion

Bleeding and active contrast extravasation Extraluminal air

VASCULAR OCCLUSION

“Filling defect” and mimics Acute vs. non-acute occlusion

Effects of occlusion

Intravascular Filling Defect

Intraluminal filling defect(s) with sharp interface with intravascular contrast material

Acute pulmonary emboli

SMA/SMV Thrombus

Superior mesenteric artery thrombus

Superior mesenteric vein thrombus with bowel dilatation/thickening, likely

ischemia

Deep Vein Thrombosis

DVT of the left femoral vein

Pseudo-filling Defect

Not sharp

Not that hypodense Outside vessels

Pseudo-filling defect in bilateral femoral veins 2/2 heterogeneous contrast opacification

Interlobar lymph nodes

Acute Filling Defect

Peripheral filling defect acute angled with arterial wall

Partial, central filling defect Polo mint Railway tract

Normal or enlarged vessel diameter Perivascular soft tissue stranding

Changes 2/2 Occlusion

Proximal to site of vascular occlusion – high pressure

At site of vascular occlusion – attempt to reperfuse Distal to site of vascular occlusion – infarction

(proximal/distal = relative to blood flow)

ANEURYSM/PSEUDOANEURYSM

Fusiform vs. saccular Rupture?

Infected?

Aneurysm/pseudoaneurysm: Definitions

Fusiform >1.5X of expected diameter

Any saccular and pseudo-

(1.1x-1.4x = ectasia)

UFHealth.org

Pseudoaneurysm: Aortic Injury

*  *  

Pseudoaneurysm with surrounding hematoma of the proximal descending

thoracic aorta 2/2 blunt trauma

Fusiform Aneurysm: Aorta

Thoraco-abdominal fusiform aneurysm with partial thrombosis and ulcer within

the thrombus

Partially thrombosed AAA

Saccular Aneurysm: Aorta

Saccular aneurysm of the aortic arch with partial thrombosis

“Impending” AAA Rupture

<< Hyperdense crescent

Sensitivity 77%, specificity 93%, PPV 53%

Focal discontinuity of intimal calcification

Tangential calcium sign

Bottom-row images from Radiologyassistant.nl

BLEEDING AND ACTIVE CONTRAST EXTRAVASATION

Blood density on CT Blood in free spaces and confined spaces

Active bleeding

Blood on CT

Shades of gray

Air Fat CSF Water CM Bone Metal -1000 0 15 1000 HU

Description relative to organs where blood is located CT attenuation of blood products depends on location,

mixture (i.e., with CSF), initial hematocrit and time from onset of bleeding

Hematocrit Effect

35-45 HU

Whole blood = cells + plasma

55-65% Plasma

Erythrocytes 35-45%

Leukocytes  And  platelets  

0-10 HU

60-90 HU

Location of Blood

Potential spaces

Pleural, pericardial, peritoneal Confined spaces (organs, structures) Mediastinum, chest wall

Solid organs Hollow viscus

Hemothorax

Mostly from trauma

Hemithorax holds up to 4L – enough for exsanguination

Clotting may occur quickly

Traumatic left hemothorax

*  

Mediastinal Hemorrhage

Trauma

Vascular/cardiac rupture and dissection

Coagulopathy

Traumatic aortic pseudoaneurysm “Traumatic aortic injury”

*  

Hemoperitoneum

Most dependent portions

Abdomen: hepatorenal Pelvis: cul-de-sac

Ruptured ovarian cyst

*  

*  *  

Sentinel Clot

Clots develop at site of bleeding (sentinel)

Higher density (45-80 HU) compared to blood elsewhere (25-45 HU)

Probable site of bleeding

Ruptured GI stromal tumor of stomach

**  

*  

Retroperitoneal Hemorrhage

Around retroperitoneal organs/structures

Ruptured AAA

*  

*  

Active Contrast Extravasation

Jet or focal area of contrast in hematoma

High density mostly >100 HU *  *  

Active Contrast Extravasation

Changing appearance and/or density on delayed images

*   *   *  

*  **  

Active Contrast Extravasation

Significant bleeding

May require IV fluid, blood transfusion, embolization or surgery depending on clinical factors lifesaving surgical or endovascular Rx

EXTRALUMINAL AIR

Air in extraluminal spaces Mimics

Extraluminal Air

“Something bad is going on.”

Mostly indicative of surgical emergency CT best to detect small extraluminal air and may be

able to define the etiology

Pneumothorax

Gas in pleural cavity thru chest wall or lung across visceral pleura

No lung tissues Much lower density

(lower than -1000 HU)

CT most reliable for diagnosis but should not be routine

*  *  

Pneumothorax

Look for signs of possible tension on CT - best on coronal view

Mediastinal shift to contralateral side, flat/inverted diaphragm “Clinical” diagnosis

*  *  

*  

*  

*  *  

Pneumothorax

Supine position – anterior, medial location *  

Pneumomediastinum

Sources:

Airways Esophagus Lungs

Track from neck or abdomen

Presumed alveolar rupture – Macklin effect

Pneumomediastinum

Concerning if:

Fluid in mediastinum Localized around airways or esophagus

Leakage of esophageal contrast

Spontaneous esophageal perforation

*  

*  

Pneumopericardium

Thoracic surgery

Pericardial drainage Trauma Gas-forming infection

Fistula to esophagus/stomach

Image from Polhill et al. J Trauma 2009; 66(4)

*   *  

In the Abdomen:

Perforated duodenal ulcer

Colonic pneumatosis

Look for extraluminal air in lung window

Intraperitoneal vs. Retroperitoneal

52  

*  *  

*  *  

Intraperitoneal air. Smallest amount in the anterior, non-dependent portion, mostly

in RUQ Retroperitoneal air outlining

retroperitoneal organs

Pneumatosis vs. Intraluminal

53  

Pneumatosis intestinalis – colon Air in the wall, dependent portion,

separated from luminal content

Small bowel feces in the lumen of small bowel loops

Portal Venous vs. Biliary Air

54  

Portal venous gas With  pneumatosis,  PVG  is  likely  2/2  necro?c  bowel  

Pneumobilia

Common:  Incompetent  sphincter  of  Oddi,  recent  instrumenta?on:  ERCP,  surgery,  fistula  with  GI  tract  

Rare:  gas-­‐forming  infec?on  

Periphery of liver More branching

Central of liver Few number of branches

Intraperitoneal Air

Perforation Site Amount Location

Stomach/duodenum Abundant Around liver and stomach

Small bowel Small Mesenteric folds, around liver

Appendix Small/absent Around appendix

Large bowel Variable Pelvis, mesenteric folds, retroperitoneal space

Retroperitoneal Air

Perforation of:

Duodenum Colon: asc/descending Rectum

Post retroperitoneal Sx

Pneumatosis Intestinalis Variables1 Odds ratio

Peritoneal signs 9.40

Age >60 years 3.00

Portal venous gas and pneumatosis

2.52

Ascites 1.92

1Hani MB, et al. J Surgical Res 2013;185:581.

!  Utility of CT appearance questioned

!  Mesenteric fat stranding !  Bowel wall thickening

Where Air Is Coming From?

Outside

Trauma Iatrogenic

Produced there

Gas-forming infection Nearby organs/structures Fistula to/from air-containing structures

Extension from contiguous organs/structures

Summary

Tips on ordering body CT in ER discussed

Critical CT findings shown and discussed Vascular occlusion Aneurysm/pseudoaneurysm,

Blood and active contrast extravasation Extraluminal air

THANK YOU FOR YOUR ATTENTION