Diagnostic Imaging Issue in
the ED
Feb 13, 2003
Sarah McPherson
Dr. Bryan Young
Outline


U/S vs CT
U/S in the ED







AAA, blunt abdo trauma, 1st trimester bleed, gall
bladder disease
U/S by ED docs
CT for appendicitis
CT vs IVP for renal colic
Imaging for carotid dissection
Imaging scaphoid injuries
MSK infections in pediatrics
U/S vs CT
U/S
PROS





Noninvasive
No radiation
Portable
Records motion (vascular
pulsation”)
CONS



Poor visualization 2nd to
body habitus and gas
patterns
Required positioning may
be difficult
Does not visualize
retroperitoneum
CT
PROS





Visualizes retroperitoneum
Quick
Not limited by body habitus
or abdominal distension
High accuracy
CONS


Radiation exposure
Patient must leave the ED
Ultrasonography
A 50 yo woman presents with RUQ pain X
4hr after eating her kid’s Happy Meal at
McDonald’s. You’re wondering if you
order an Ultrasound how good is it at
telling you that this patient has acute
cholecystitis??
Imaging the Gallbladder




90-95% of acute cholecystitis will have
stones
U/S is 95% sensitive to see stones
Stones + wall thickening or a + Murphy’s
sign has a PPV of 95 and 92% for acute
cholecystitis
Sensitivity for acalculous chole is 67-92%
EMR vol 17/15, July 22, 1996
Imaging the Aorta
A 70 year old hypertensive man presents
with acute flank pain. He also has a
history of kidney stones 30 years ago And
is unsure if this pain is the same. He is
writhing around in the bed. You think he
may have renal colic but a leaking AAA is
also on the differential. You wonder…how
good is ultrasound at visualizing the
aorta????
Imaging the Aorta with U/S



An U/S is very good at telling you if there is an
aneurysm (dilation >3mm)
It has a sensitivity of 97%
It is NOT sensitive enough at detecting an
intimal flap to rule out a dissection and it cannot
tell you if there is a current leak…for that you
need to go on to CT
EMR vol 17/15, July 22, 1996
Blunt Abdominal Trauma
We’ve covered this before but a review is never
bad….
 DPL vs U/S vs CT
DPL:




Positive = aspiration of > 10cc frank blood, RBC >
100,000/ mm3, WBC > 500/mm3, + gram stain
Pros: patient doesn’t leave department, fast and easy,
cheep, sens = 94-96%, spec = 96-99%
Cons: invasive, technically difficult in obese and preg
pt, misses diaphragmatic and retroparitoneal injuries
Blunt Abdo Trauma

Ultrasound


Pros: fast, portable,
noninvaasive, sens = 80100%, spec = 94-100%
Cons: relies on experience
of technician, sensitivity for
specific organ injury and
retroperitioneal injury low,
obesity, sc emphysema,
and open wounds will
decrease visualization
Blunt abdo trauma
Blunt abdo trauma

CT


Pros: very accurate (97% in detecting injury),
fast, visualizes solid organs and
retroparitoneum
Cons: patient must be transported to scanner,
exposure to radiation and iv contrast
U/S in 1st trimester bleeds

A 23 yr woman G2P1 presents with
vaginal bleeding. She thinks she is about
6 weeks by dates. What do you expect to
see on ultrasound and how do you
interpret the U/S with serum BhcG levels?
U/S in the 1st trimester

Of patients with vag bleed or pelvic
cramping or both ~ 60% will have
pregnancies that develop normally, 10%
will be ectopics,and 30% will end in a
miscarriage
U/S findings and serum BhcG

Transvaginal U/S




Gestational sac seen at 5 wks with BhcG of
1000-1,800
Yolk sac seen at 6 wks with BhcG of 2,500
Fetal pole seen at 7 wks with BhcG of 5,000
Fetal heart rate at serum BhcG of 17,000
(fetal pole at ~ 5mm in length)
Ann Emerg Med. 1999.33/3
How to interpret if there is a fetal
heart beat




It is a live intrauterine gestation
~ 1/30,000 pregancies (without fertility meds)
will have an intra and extra uterine pregnancy
2-4% with a fetal heart beat have spontaneous
abortion
If there is a subchorionic hemorrhage…the
spontaneous abortion rate is 30%
Emerg Med Clin. 1997. 15/4:789-823
How do you know if it is an
abnormal pregnancy???



When there is no fetal pole and the gestational
sac is > 16mm on EVS or > 25mm on TAS this is
likely early fetal demise
A gestational sac > 10mm should have a yolk
sac (but some will still be a normal IUP)
A fetal pole > 5mm should have a fetal heart
beat (the absence is the most reliable finding of
a nonviable IUP)
Ann Emerg Med. 1999: 33/3

In symptomatic patients with echogenic material
and no gest sac, likelihood of IUP is low
Acad Emerg Med. 1999; 6/2: 116-20
How do you know if it is an
ectopic????

~ 39% of ectopics with BhcG < 1,000 can be
identified on U/S
Ann Emerg Med. 1999; 33/3


Definitive for ectopic: echogenic ringlike
structure outside the uterus with a gest sac with
a yolk sac or fetal pole
R/o’d if there is evidence of a definite IUP (gest
sac with yolk sac or fetal pole) or probably r/o’d
if there is evidence of an abnormal IUP (gest sac
>10mm with no yolk sac or > 16 mm & no fetal
pole)
Other signs of an ectopic


Abnormal adnexal mass (solid or cystic separate
from ovary) 70% will be an ectopic
Large anechogenic or echgogenic fluid in the
cul-de-sac 50-80% will be an ectopic
Ann Emerg Med. 1999;33/3

Severe adnexal tenderness with probe pressure
Emerg Med Clin.1997;15/4:789-823

Endometrial stripe
Acad Emerg Med.1999;6/6:602-8
What about ER docs doing U/S??
What are the reasons???
 To improve quality care
 Decrease time to emergency scans
 Lessen the need to send potentially unstable
patients out of the ED
 Improve patient flow
 Increased staff satisfaction
 Improve patient satisfaction
 Decrease stress on ancillary departments
Ann Emerg Med. 1997;29/3:367-74
What is different about us doing
U/S??






obviously we have less training
It is highly focused (usually just looking to
answer 1 question ie Is there an AAA?)
It is interactive (extension of physical exam)
It is brief
May be repeated as clinically warranted
Emphasizes 1 finding, it is NOT comprehensive
(formal techs should do this)
Emerg Med Clin. 1997;15/4:735-43
What is the scope of ED U/S

Emergent Scans:





Urgent Scans:



AAA
Cardiac arrest/tamponade
? Live IUP (1st trimester symptoms & maternal
trauma)
Abdo trauma
? Gallstones
? Obstructive uropathy
To facilitate procedures

Lines, thoracentesis, paracentesis,
pericardiocentesis, FB removal, suprapubic aspiration
Ann Emerg Med. 1997;29/3:367-74
How good are we???

ED MD’s doing U/S in blunt abdo trauma

J of Trauma.1995;38/6:879-85





Prospective, N = 245, U/S vs CT/DPL or lap
Sens = 90%
Spec = 99%
Accuracy = 99%
Ingerman et al.Acad Emerg Med.1996





N = 97, U/S vs DPL/CT or lap
Sens = 75%
Spec = 96%
Accuracy = 91%
There were no FP/FN after 67 scans
At detecting AAA…???


There’s more evidence but alas I didn’t have
time to find it all….
Acad Emerg Med. 1994;12/2;185-9



N = 11
Sens and spec = 100%
Ann Emerg Med. 2000;36/3:219-23


N = 68, prospective, gold standard = Sx, other
imaging, radiologist review of ED U/S
Sens = 100%, spec = 100%
At identifying IUP?

Ann Emerg Med.1997;29/3:348-351





N = 115, EPPS vs rads or obs/gyn
Sens = 94%, spec = 100% for IUP
No adverse outcomes
EPPS had decreased LOS
Ann Emerg Med. 1997;29/3: 338-47


N = 136, if definite IUP d/c with follow up until
definitive dx confirmed, equivicable cases referred to
rad/obs/gyn
Sens = 90%, spec = 88% for making dx of Ectopic
Pregnancy
Does doing transvaginal U/S in the ED
decrease patient wait times?…it appears
so!

Acad Emerg Med.1998;5:802-17





N = 84 (46 in ED), retrospective
Time to discharge ED U/S vs Obs/gyn U/S
164(+/- 13) min vs 235 (+/- 12) min
No EP were missed by ED U/S
Acad Emerg Med. 2000;7:988-93


N = 1419 (277 in ED), retrospective
Of confirmed IUP cases, time in ED was 59 min (4977min) less in ED MD group than rad group; time was
longer (77min CI 55-97) from 6pm-6am
How about detecting pericardial
fluid??

Ann Emerg Med. 2001;38/4:377-82




N = 515 (103 who had effusion)
Prospective, ED MD (5 hrs training in Echo)
Echo then reviewed by cardiolgy, ? Adequate
study and ? Was there fluid
Sens = 96%, spec = 98%
93% of the 515 studies were found to be
technically adequate
On to CT….
A 40 yo female presents to the ED with RLQ pain.
She had diffuse pain initially and is now
localized for the past hour. She is nauseated
and is not anorexic. On physical exam she has
percussion tenderness in the RLQ, a + Rovsig’s
sign and appears uncomfortable with
movement. Her urine BhcG is negative.
Do you call surgery right away, do a CT scan, send
her home with some T3’s…???
CT’s for appy’s

Clinically the rate of normal appy’s with Sx
is 22-30% Am J surg. 1981;141:232-4, J R Coll Surg Edin.1983;28:35-40,
BMJ. 1972;2:9-13

Can this be improved with better
imaging???
CT’s for appys


MANY studies have been done
Clin Rad. 2002;57:741-45




N = 50, prospective
Pre-op CT’s ? Signs of appendicitis
Compared with surgical and histological
findings
Sens = 95%, Spec = 92%, an alternate
diagnosis was found in 10 of 12 CT’s that did
not have evidence of Appendicitis
More evidence on CT for appys

AJR.2002;178:1319-25



N = 650, retrospective, surgical and clinical
records used for follow-up (85% had
adequate follow-up)
Sens = 97%, Spec = 98%
In patients without appendicitis CT revealed
an alternate diagnosis in 62% of cases
Still more evidence

Radiology. 2001;221:747-53



N = 100, prospective all clinically equivocal
(no RLQ peritonism, no fever, no vomiting, no
leukocytosis, observed for > 24 hr in hospital)
30 pos CT, 70 neg CT (2 FP, 2 FN)
Sens = 93%, Spec = 97%
Now some evidence against
imaging

Arch Surg.2002;136:556-62





N = 766, retrospective (only patients who had
appendectomies)
Compared clinical features, pre-op CT & pre-op U/S
with surgical findings
Findings: migratory pain PPV 91%, WBC > 12
PPV 90%, overall clinical accuracy = 75%, CT
accuracy = 75%, U/S accuracy = 43%, negative
appendectomy rate = 16%
But rates of imaging were very low (8% of cases had
CT) so essentially the results are based on clinical
assessment
Time to the OR was longer in imaged group
Imaging in Pregnancy



Radiation teratogenicity mainly a concern from
10-17 wk gestation
Potential for growth retardation, microcephaly,
intellectual deficits, CNS defects from
cummulative dose of 50 mGy (5 rad). Radiation
induced malignancy from 100 mgY (10 rad)
Therefore try to minimize amount of radiation to
fetus
CT in Pregnancy


CT for renal colic or appendicitis with fetal
shielding is ~ 3 mGy/exam
CT for pulmonary embolism = 0.2mGy


VQ = 0.1mGy (with decreased amt
radionucleotide)
Pulm angio = 0.5 mGy
AJR.2002;178:1285-6
Renal Colic

Urology.1998;52/6:982




N = 106, prospective CT vs IVP
Diagnosis defined as “unequivocal evidence
of urolithiasis”
CT: sens = 96%, spec = 100%
IVP: sens = 87%, = 94%
CT vs IVP more evidence

J of Urology.1999;161:534





N = 40, prospective
CT and IVP in all with clinical follow-up
CT: sens = 100%, spec = 92%
IVP: sens = 64%, spec = 92%
Authors noted that sens and spec of CT is
dependant on the training of the MD reading
the films
CT vs U/S for renal colic

J of Urology.2001;165:1082-84





N = 109
CT vs U/S (IVP as gold standard)
CT sens = 100%, spec = 96%
U/S sens = 96%, spec = 90%
Radiology.2000;217:792-7




N = 45, prospective
CT vs U/S, clinical, surgical follow-up data as gold
standard
CT sens = 96%, spec = 100%
U/S sens = 61%, spec = 100%
? An alternate diagnosis??

Katz et al. Urology.2000;56/1



Reviewed 1000 CT for renal colic
557 showed renal calculi, 67 recently passed
stone, 257 normal, 101 an alternate diagnosis
So….. Not only is CT better diagnostically but
it can frequently give an alternate diagnosis
Scaphoid Fractures

Clin J Sports Med.1996;6/2:137





N = 102, clinically had # scaphoid but no
fracture on xray, 4d vs 14d bone scan
4d correctly identified all # seen at 14 day but
there were 7 false positives
Sens = 100%
Spec = 92%
Accuracy = 93% (CI 88-98%)
Scaphoid #

Many more studies




Rolfe et al: N= 99, sens = 100%, spec = 91%
Stordahl et al: N = 30, if bone scan – at 72hr it rules
out #
Tiel-Van Buul et al: bone scan at 72 hr. Rx as # if
positive, f/u at 1 yr for all neg’s none showed physical
disability or radiographic evidence of a missed
fracture
BOTTOM LINE: a bone scan at 3-7 days is very good
at identifying scaphoid fractures, however, you’ll have
false positives.
Scaphoid fractures MRI vs
traditional f/u

AJR. 2001;177:1257-63





Reviewed literature of past 6 yrs
With a neg x-ray the clinical exam will lead to 4/5
people being casted unnecessarily
Bone scan is almost 100% sensitive but lacks
specificity therefore many follow-up appointments are
necessary
MRI is 100% sens and almost 100% spec
BOTTOMLINE: the costs are about the same, MRI is
a better test, but in Canada we’re not going to be
using it for scaphoid fractures because of limited
numbers of MRI’s
Osteomyelitis



Often a difficult diagnosis to make
Earliest sign on plain film is soft itssue
swelling at ~ 3d
Bony changes not seen on plain film until
7-10days
Osteomyelitis

Bone Scans




3 phases: 1st shows increase blood flow, 2nd shows
blood pooling and third (at 4-6 hr) shows
inflammatory component
Osteomyelitis should have all phases + whereas
arthritis, # , or treated osteo show little activity in first
2 phases and lots in delayed phase
Sens for osteo 32-100%
But a normal bone scan rules out osteo 90% of the
time
Osteomyelitis

WBC Scan (Indium labelled leukocytes)




Delayed images taken (ie at 24hr)
Normally the only hot spots are liver, spleen
Area of interest imaged at 24hr for potential
”hot spot”
Variable sens = 60-83%, spec = 78-96%
Osteomyelitits

The role of MRI


Sens = 89-92%, spec = 100%
Good if only 1 area needs visualisation
7% of peds osteo is multifocal

Eur Radiol.1999;9:894-900

Recommendations in kids



Plain films
Then bone scan
Then tagged WBC scan
Then MRI

Curr Probl Pediatric.1996;26:218-37
Imaging the Carotids and
vertebral arteries



Dissection following blunt trauma to H&N
up to 3.5% will have carotid or vertebral
artery dissection
Mortality if unrecognized = 15%,
significant morbidity of 16%
Dissection the cause of stroke in young
people 5-20% of cases
How do you diagnosis it??

Think of it for:






All head and neck blunt trauma
c-spine injury
Lefort II or III
Horner’s syndrome
Skull base fracture
Neuro abnormalities not explained by
intracranial injuries
How do you best diagnosis it??

Multiple modalities…




Angiography = gold standard
CT angio (2 and 3 D recons)
MRI/MRA
U/S
So what’s best???


Initially a lot of excitement with CTA
J of Trauma. 1999;46/3:380-85




Retrospective review over 10 years for CAI
5 yrs pre CTA and 5 yrs post CTA
Incidence pre was 0.06% vs 0.19% post
Time to diagnosis decreased from a mean of
156hr to 5.6hr
More data to muddy the waters

Ann of Surg. 2002;236/3:386-95




N = 216, prospective angio +/- CTA/MRA of all
patients with H&N trauma
Incidence of 3.4% for CAI
Sens CTA = 47% for CAI, 53% for VAI
Sens MRA = 50% for CAI, 47% for VAI