Radiologic Clinics Of North America Emergency Ultrasound

226 Pages·2004·14.41 MB·english

RadiolClinNAm42(2004)xi
Preface
Emergency ultrasound
VikramDogra,MD
GuestEditor
Ultrasonographyhasundergonemanytechnologic tient care. Most of the articles describe sonography
changesresultinginitspresentstate-of-the-artequip- techniquesandpertinentsonographicanatomytohelp
ment that is capable of high-resolution real-time thosewhoarenewtothefieldofultrasonography.
gray-scale imaging and tissue harmonics, including This issue on emergency ultrasound provides the
color and power Doppler. These advances in ultra- reader with up-to-date information on what is new,
soundtechnologyhaveresultedinimprovedwork-up exciting, and relevant in the practice of ultrasonog-
of patients undergoing evaluation in emergency de- raphyas it pertainsto acutely illpatients.
partmentsbecauseitisthefirstimagingperformedon IwishtoexpressmythankstoJosephMolterfor
almost all patients presenting to an emergency facil- preparing theillustrations, to BonnieHami, MA, for
ity. This easily available imaging modality remains hereditorialassistance,andtoAdrienneJonesforher
the primary workhorse in diagnostic radiology not secretarial assistance. In addition, my sincere thanks
only in day-to-day practice but also in emergency go to Barton Dudlick at Elsevier Science for his
situations. There has been a need for the Radiologic administrative andeditorialassistance.
Clinics of North America to dedicate an issue solely
to the practice of emergency ultrasound and I am VikramDogra, MD
honoredtobetheguesteditorofthisissue.Greatcare Division of Ultrasound
hasbeengiventotheselectionoftopicsforthisissue, Department of Radiology
and pertinent findings have been summarized in the CaseWestern Reserve University
form of tables for easy reference in most of the University Hospitals
articles where problem-solving algorithms are also 11100EuclidAvenue
included. Relevant topics have been included that Cleveland, OH44106, USA
arehelpfultoallcliniciansinvolvedinemergencypa- E-mail address: [email protected]
0033-8389/04/$ – seefrontmatterD2004ElsevierInc.Allrightsreserved.
doi:10.1016/j.rcl.2004.01.004
RadiolClinNAm42(2004)257–278
Hepatobiliary imaging and its pitfalls
Deborah J. Rubens, MD
DepartmentsofRadiologyandSurgery,UniversityofRochesterMedicalCenter,601ElmwoodAvenue,
Rochester,NY14642-8648,USA
Diagnosisof acutecholecystitis Sonographic Murphy’s sign
Acute cholecystitis is the result of obstruction of The sonographic Murphy’s sign is defined as
the gallbladder and accompanying inflammation of specific reproducible point tenderness over the gall-
the gallbladder wall with associated infection and bladderasthetransducerappliespressure.Inaclassic
sometimes necrosis. Ninety percent to 95% of cases article by Dr. Phillip Ralls [4], which included only
of acute cholecystitis are caused by obstruction by patientswithrightupperquadrantpain,fever,andan
gallstonesineitherthegallbladderneckorthecystic elevated white blood cell count, a sonographic Mur-
duct [1]. Acute cholecystitis occurs in only approxi- phy’s sign was 87% specific for the diagnosis of
mately20%ofpatientswhohavegallstones[2].This acute cholecystitis. When a positive sonographic
means that many patients with gallstones have no Murphy’s sign is used in conjunction with the pres-
symptoms, and their right upper quadrant pain may enceofgallstones,ithasapositivepredictivevalueof
becausedbyadifferentetiology[3].Ofpatientswho 92% for diagnosing acute cholecystitis. Persons in
present with right upper quadrant pain, only 20% to whom a sonographic Murphy’s sign may be absent
35%haveacutecholecystitis [1,2].Asthe definition includepersonswhoaremedicated;therefore,careful
of‘‘rightupperquadrantpain’’becomeslessspecific, attention to a patient’s clinical status is important.
especially lacking an accompanying elevated white Denervated gallbladders in patients who have diabe-
bloodcellcountandfever,thepercentageofpatients tesorgangrenouscholecystitismayresultintheloss
who actually have acute cholecystitis given the his- of asonographicMurphy’s sign.
tory of right upper quadrant pain diminishes further.
Specific criteria for the diagnosis of acute cholecys-
titis are important, because many patients have gall-
Gallstone diagnosis and pitfalls
stones but may not have acute cholecystitis. The
primarydiagnosticcriterionisapositivesonographic
Gallstones are diagnosed by the presence of
Murphy’ssigninthepresenceofgallstones.Second-
gravity-dependent,mobileintraluminalechoeswithin
ary signs of acute cholecystitis include gallbladder
the gallbladder, which cast a posterior shadow
wall thickening more than 3 mm, a distended or
(Fig. 1). Although ultrasound (US) has a high accu-
hydropicgallbladder(lossofthenormaltaperedneck
racy (>95%) for the diagnosis of gallstones, some
and development of an elliptical or rounded shape),
stones may be missed [3]. False-negative results
andpericholecystic fluid.
occur because of stones that are too small to cast a
shadow(usuallysmallerthan1mm),softstonesthat
lack strong echoes [1], and gallstones that are im-
pacted in the gallbladder neck or in the cystic duct
and may not be as readily visible (see Fig. 1) [5]. If
thegallbladderisfocallytenderbutnogallstonesare
E-mailaddress:[email protected] appreciated, the patient should be examined from
0033-8389/04/$ – seefrontmatterD2004ElsevierInc.Allrightsreserved.
doi:10.1016/j.rcl.2003.12.004
258 D.J.Rubens/RadiolClinNAm42(2004)257–278
Fig.1.Gallstones.(A,left)Gallstoneinthegallbladderneck(arrow)castsnosignificantshadowandisnearlyinvisible.Gasin
the duodenum (arrowhead) obscures the fundus and casts a strong sharp shadow (asterisk). (Right) With patient in sitting
position,stone(arrow)movesoutoftheneckandcastsaclearshadow(asterisk).Adjacentduodenum(arrowheads)isseparate
fromthegallbladderbutstillcastsastrongshadow,equivalenttothegallstone.(B,left)Multiplegallstones(arrowheads),some
ofwhichcastshadows(arrows)andsomeofwhichdonot.(Right)Normalcalibercommonduct(6mmattheporta)withstones
(arrows)insamepatient.Choledocholithiasismaybedifficulttodetect,especiallyinthedistalduct,ifthestonesdonotshadow
orarenotoutlinedbythedistalfluid.(C,left)LongitudinalUSshowsanormalgallbladder.(Right)Harmonicimagingreveals
multiplesmallstones(arrows).
multiple positions, including prone position or up- Echogenicity of stones may be decreased in soft
right position, to help stretch out the gallbladder pigment stones. These stones are commonly associ-
[3,6]. Decubitus or intercostal scanning also may ated with recurrent pyogenic cholangiohepatitis and
help visualize the neck, which may not be as easily are more often seen in the bile ducts than in the
apparentfrom asubcostal supineapproach. gallbladder. They look more like soft-tissue masses
Resolution of small stones in the gallbladder can than stones and may or may not cast acoustic shad-
beimprovedwithuseofharmonicimaging[7,8].This ows.Theymaybemisinterpretedassludgeordebris
approach uses the higher frequency of the returning andgive afalse-negative diagnosisforgallstones.
sound beam for better resolution and decreases the False-positive results may arise from side lobe
scatteringfromsuperficialstructuresintheabdominal artifacts,whichgiverisetoechoesthatseemtoarise
wall and in the adjacent liver. Harmonic imaging within the gallbladder lumen but are actually gener-
improves the echoes cast by stones and strengthens ated from the wall or outside the wall [1]. Similarly,
their posterior shadows. This improved resolution partialvolumeartifactsfromgasintheadjacentbowel
may permit visualization of stones not seen with may mimic stones with strong echoes and posterior
conventionalgrayscaleUS(seeFig.1). shadowing(seeFig.1A).Acalciumbilesaltprecipi-
Fig.2.Pseudogallbladders.(A)Transverseimageintherightupperquadrantwithstructureidentifiedasthegallbladder(arrows)
containingdebris(asterisk).Notethatthe‘‘gallbladder’’doesnotextendanteriorlyandthattheaorta(A)isimmediatelyadjacent.
(B,left)CTimageofthesameareaasinAshowsafluid-containingstructure(arrows)withsimilarattenuationtobloodinthe
aorta(A).Thiswasahematoma.(Right)Thetruegallbladder(GB)islateraltotheaortaandextendsanteriorly.(C,left)Distended
fluid-anddebris-containingstructurebelievedtorepresentanabnormalgallbladderinthispatientwithrightupperquadrantpain.
(Right)Thetruegallbladder(arrows)iscompressedanddisplacedbytheadjacentmass,apancreaticpseudocyst.(D)CTofthe
pancreaticpseudocyst(P)displacingthegallbladder(arrows).
D.J.Rubens/RadiolClinNAm42(2004)257–278 259
260 D.J.Rubens/RadiolClinNAm42(2004)257–278
tatemayformwiththeuseofCeftriaxoneandmimic associated with complications such as gangrenous
gallstonesonsonographicexamination.Theseprecip- cholecystitis [9]. A striated wall also is nonspecific,
itatesresolveafterthepatientendstherapy. however, and may be seen in all the other causes of
Other fluid-containing structures may mimic the wall thickening,including hepatitis (Fig. 6) [10].
gallbladder, especially if the gallbladder is out of its Similarly, pericholecystic fluid is a nonspecific
normal position or is small and contracted. These finding; it may occur because of ascites or localized
structures include the duodenum, gastric antrum or inflammationfromothercauses,suchaspepticulcer
colon,hematomas,pancreaticpseudocysts(Fig.2),or disease (see Fig. 4) [2]. Teefey et al [10] described
even dilated vascular collaterals. Mistaking these twospecificpatternsofpericholecysticfluid.TypeI,
structures for the gallbladder may result in missed a thin, anechoic, crescent-shaped collection adjacent
pathology in the true gallbladder or a false-positive to the gallbladder wall, is nonspecific (see Fig. 4B).
diagnosis of gallbladder disease (ie, obstructed gall- Type II, a round or irregular shaped collection with
bladderor acalculous cholecystitis). thickwalls,septations,orinternaldebris,isassociated
with gallbladder perforation and abscess formation
(Fig. 7) [10]
Gallbladderwall thickening and pericholecystic
fluid
Gallbladder wall thickening is defined as a wall Acute acalculouscholecystitis
diameter more than 3 mm and is present in 50% of
patients with acute cholecystitis (Fig. 3) [1]. The This is an acute inflammation of the gallbladder
gallbladderwallmaybethickenedbecauseofhepatic that occurs in up to 14% of patients with acute
congestion or edema from liver disease, right heart cholecystitis [11]. It is most frequently seen in post-
failure, orgeneralized edema from hypoproteinemia, trauma and postsurgical patients and other hospital-
whichisoftenassociatedwithrenaldiseaseorhepatic ized patients and occurs because of conditions that
dysfunction [3]. A thickened gallbladder wall also lead to ischemia, hypotension, or sepsis [12]. These
can occur in association with adjacent inflammatory critically ill patients are often medicated with nar-
conditions, including hepatitis, peptic ulcer disease cotics,areonventilators,andreceivehyperalimenta-
(Fig. 4), pancreatitis, perihepatitis (Fitz-Hugh-Curtis tion,whichcontributestobiliarystasisandfunctional
syndrome),andpyelonephritis (Fig. 5). cystic duct obstruction [2,12]. Gallbladder gangrene
A thickened, striated gallbladder wall consists of isassociatedin40%to60%ofcases,withincreased
alternatinghyper-andhypoechoiclayers.Whenseen risk of perforation [2]. Mortality ranges from 6% to
in the setting of acute cholecystitis, it is strongly 44% but can be reduced by early diagnosis and
therapy [12]. In the series by Cornwall et al [12],
only 50% had a sonographic Murphy’s sign. This is
a difficult clinical and ultrasonic diagnosis, because
gallstones are absent and the sonographic Murphy’s
sign may be limited because of other illnesses
and medication. The diagnosis is made by gallblad-
der tenderness (if present) and is associated with
gallbladder distension, intraluminal debris, and gall-
bladder wall thickening that is not caused by other
etiologies, such as hypoalbuminemia, congestive
heart failure,orhepaticcongestion (Fig.8).Because
gallbladderwallthickeningisnonspecific,CTcanbe
used to visualize pericholecystic inflammation to
improve diagnostic specificity [2,13].
Complicated cholecystitis
Fig.3.Acutecholecystitis.Thispatientpresentedwithright
upper quadrant pain and a positive sonographic Murphy’s
sign. Longitudinal US shows stones (arrows) and diffuse Complications of acute cholecystitis include gan-
gallbladderwallthickening(cursors)thatmeasures5mm. grenous cholecystitis, emphysematous cholecystitis,
D.J.Rubens/RadiolClinNAm42(2004)257–278 261
Fig.4.Pepticulcerperforationandthickgallbladderwall.(A)Patientwithrightupperquadrantpain,fever,andelevatedwhite
bloodcellcount.USshowsfocalgallbladderwallthickening(7-mmcursors)andgallstones(asterisks)andcouldbeinterpreted
ascholecystitis.Thefreeairwithreverberationshadows(arrows)thatleadstothecorrectdiagnosiscouldbeoverlookedeasily.
(B) Transverse US shows wall thickening (cursors) and simple pericholecystic fluid (arrow). (C) CT image shows peri-
cholecystic fluid (arrows), free air (arrowheads), and extraluminal accumulated air (paired arrowheads) in perforated duo-
denalulcer.
andgallbladderperforation.Thesecomplicationsoc- Gangrenouscholecystitis
cur in up to 20% of patients [3]. Complications of
acutecholecystitisareimportanttodetectbecausethey Gangrenouscholecystitisisdefinedhistologically
are associated with increased morbidity (10%) and as coagulative necrosis of the mucosa or the entire
mortality (15%) [14] and require emergency surgery wall associated with acute or chronic inflammation
[2]. There is also approximately a 30% conversion [10]. It occurs in up to 20% of patients with acute
for laparoscopic cholecystectomy to an open proce- cholecystitis andhasanincreasedriskofperforation
dureinthesettingofcomplicatedcholecystitis[14]. [3].Unfortunately,USisrelativelynonspecificforthe
262 D.J.Rubens/RadiolClinNAm42(2004)257–278
Fig.5.Pyelonephritiswithgallbladderwallthickening.(A)Gallbladderwallshowsmarked1.3cmthickening(cursors)and
hypoechoic fluid within the wall. (B) Transverse US of the lower pole of the right kidney shows a 3-cm echogenic mass
(arrows). (C) CT through the right lower pole shows the characteristic round, heterogeneous decreased attenuation area of
pyelonephritis(arrows).
diagnosisofgangrenouscholecystitisbecauseasono- ciationwithgangrenouscholecystitis[3].Thefundus
graphic Murphy’s sign is absent in two thirds of isthemostcommonsiteforperforationbecauseithas
patients [15]. A relatively specific finding is intra- the least blood supply. Acute perforation with free
luminal membranes caused by a fibrous exudate or intraperitoneal bile results in peritonitis and is rare.
necrosis and sloughing of the gallbladder mucosa Morecommonly,subacuteperforationoccurs,which
(Fig. 9). This finding is present, however, in only results in pericholecystic abscess formation [2].
5% ofpatients [10]. These abscesses may occur in or adjacent to the
gallbladder wall in the gallbladder fossa, within the
liver, or along the free margin of the gallbladder
withintheperitonealcavity[10].Theyarecharacter-
Gallbladderperforation ized bycomplex fluidcollections with inflammatory
changesintheadjacentfatonUSorCT[2].Patients
Gallbladder perforation occurs in 5% to 10% of with peritoneal or liver abscesses require immediate
patients with acute cholecystitis, most often in asso- surgeryanddrainage,respectively,whereasabscesses
D.J.Rubens/RadiolClinNAm42(2004)257–278 263
in the gallbladder wall and fossa may respond to
conservative management [16].
Pericholecystic fluid adjacent to the gallbladder
wallmaymimicperforation.Uponcarefulinspection,
however,thewallisintactandthefluidanechoic(see
Fig. 4B). Fluid that appears within the walls been
noted to precede perforation in one case [17]; how-
ever,nospecificUSfeaturespredict whichgallblad-
ders will perforate.
Emphysematous cholecystitis
This is a rare complication of acute cholecystitis
(less than 1% of all complicated cases) and is
associated with gas-forming bacteria in the gallblad-
derlumenorinthegallbladderwall.Asmanyas40%
Fig. 6. Hepatitis,withstriatedgallbladderwallthickening.
of patients with emphysematous cholecystitis have
LongitudinalUSofcontractedgallbladderwithathickened
diabetes [2]. The clinical course is rapidly progres-
striatedwall(arrows)withalternatingechogenicandhypo-
sive,with75%incidenceofgallbladdergangreneand
echoic layers. This patient had right upper quadrant pain,
fever, abnormal liver function tests, and a negative sono- 20% incidence of perforation [18]. Emphysematous
graphicMurphy’ssign.ShetestedpositiveforhepatitisBand cholecystitis canberecognizedbytheantidependent
clinicallyhadacutealcoholichepatitis.Thestriatedwallis gasechoeswithinthelumen(Fig.10).Intramuralgas
notspecificforgallbladderdisease. may be more difficult to identify because it may
mimic the calcified wall of a porcelain gallbladder.
Thetypeofshadowing(‘‘clean’’versus‘‘dirty’’)does
not differentiate between calcium and air. The loca-
tion of the echoes does. If the presence of gas is
Fig. 7. Complicated cholecystitis with gallbladder perforation. (A) Longitudinal US of the gallbladder (GB) with adjacent
irregularly marginated pericholecystic intrahepatic fluid (arrows). This patient presented with sepsis 2 weeks after prostate
surgeryandwasfoundtohaveacutecholecystitiswithanadjacentliverabscess.(B)LongitudinalUSofgallbladderwithstones
showsapericholecysticcollection(arrow)thatcontainsdebris.Thecollectionabutsthefreewallofthegallbladderandisnot
contained within the gallbladder wall (double arrow). (C) CT shows an enhancing rim around the fluid (arrows) and
inflammatoryedemaintheadjacentfat(arrowheads).
264 D.J.Rubens/RadiolClinNAm42(2004)257–278
Fig. 9. Gallbladder gangrene/mucosal sloughing. Longitu-
dinal US of patient with acute cholecystitis secondary to
stone (arrow) impacted in the gallbladder neck. Note the
intraluminal membranes (arrowheads), which are associ-
atedwithgallbladdergangrene.
extrinsic masses with biliary duct compression and
obstruction. The diagnosis is made by evaluation of
intra- and extrahepatic ducts, because one or both
Fig.7(continued).
maybedilated,dependingonthelevelofobstruction.
uncertain,eitherCTorplainfilmradiographycanbe
usedtodifferentiatebetween gasandcalcification. Ultrasound diagnosis of ductdilatation
The extrahepatic common duct is measured from
Biliary ducts outerwalltoouterwallatthelevelofthecrossingof
the right hepatic artery. The diameter at this level
Dilatedbiliaryductsintheacutepatientrepresent should not exceed 6 mm [1]. The diameter of the
a relative emergency because sepsis in association common duct is slightly greater distally as it ap-
with dilated ducts requires rapid decompression. proaches the pancreas, sometimes as much as 1 to
Biliary duct dilatation may be the result of multiple 2mm.Thereisstilldebateinliteratureastowhether
causes,includingstones,tumor,stricture,oradjacent thebileductdilateswithageoraftercholecystectomy
[1]. Most laboratories consider a duct smaller than
6 mm normal and a duct 8 mm or larger abnormal
[1,19].Clinically,ifapatienthasdilatedductsbutno
accompanying symptoms—elevated bilirubin, pain,
sepsis, or elevated liver enzymes, including alkaline
phosphatase—the dilated ducts are unlikely to be
clinically relevant. Similar to the presence of gall-
stones, when assessing the ducts for biliary disease,
the clinical scenario is of prime importance. Intra-
hepatic biliary ducts are normal if they are 2 mm or
smaller in the porta or no more than 40% of the
diameter of the accompanying portal vein [1]. With
theadventofnewerequipment,however,itispossi-
bletoseeintrahepaticbiliaryductsinnormalpatients,
especially with the use of harmonic imaging, which
diminishes scatter. Clinical correlation is important,
Fig.8.Acalculouscholecystitis.LongitudinalUSofadebris-
filled (asterisk) gallbladder with a thick, striated wall (ar- because manyyoungandslender patientsmay show
rows).Nostonesarevisualized.Atsurgery,thiswasacute normal ducts with high-frequency transducers
acalculouscholecystitis. (Fig. 11A). In general, intrahepatic biliary duct dila-