Postgrad Med J: first published as 10.1136/pgmj.63.741.525 on 1 July 1987. Downloaded from Postgraduate Medical Journal (1987) 63, 525-532 Review Article Pitfalls in the ultrasonographic diagnosis ofgallbladder diseases E.J. Fitzgerald' and A. Toi2* 'Department ofDiagnostic Radiology, University Hospital of Wales, Heath Park, CardifCF4 3XW, UK, and 'McMaster University Medical Centre, Hamilton, Ontario, Canada. Summary: Ultrasonography is rapidly replacing radiological techniques of gallbladder investigation. While ultrasonography is highly accurate, there are technical, anatomical and diagnostic pitfalls which will trap the unwary. This presentation highlights the pitfalls which we have encountered, reviews the literature in this area and suggests techniques whereby these pitfalls may be avoided. Introduction Table I Pitfalls in the ultrasonographic diagnosis of gall- bladder disease Ultrasonography is now considered by many to be the Technical: method ofchoice of screening for gallbladder disease. 1. Mis-identification: bowel for gall stone copyright. The accuracy of this technique is claimed to exceed ligamentum teres 90%.',2,3, However, high false positive rates of 7% and hepatic granulomas false negative rates of 15% are still reported in some aorta series.4'5 Since the diagnosis of gallstones by ultrason- migrating masses (dermoid) ography is often followed by cholecystectomy without 2. Wrong technique: transducer, gain further confirmatory studies, the avoidance, especially patient not moved offalse positive diagnosis is important. Iffalse positive 3. Pseudosludge and calculi due to side lobe artefact. gallbladder diagnosis were to occur at the 4. Communication: typographical and documentation 1.5% rate errors reported by Allen-Mersh,5 then about 2,000 unneces- http://pmj.bmj.com/ sary cholecystectomies could occur in England and Anatomicalandphysiological variants Wales alone, and 7,000 in the United States. 1. Gallbladder folds junctional fold We have not been able to find any article listing the valves ofHeister myriad of problems encountered at ultrasonographic narrow gallbladder folded on itself investigation of the gallbladder and as a result we 2. Gallbladder fold mimics dilated bile duct. present the pitfalls and problems which we have 3. Sludge filled gallbladder looks like liver tissue. experienced over the past eight years at our institu- 4. Agenesis. tions and 5. Duct stones with agenesis on October 6, 2021 by guest. Protected found quoted in other publications, and 6. Gallbladder ectopia suggest methods to overcome these problems. 7. After cholecystoenterostomy, food and gas mimic stones. 8. Fundal and Hartmann stones not noticed. Discussion Diagnostic errors: 1. Bouveret's syndrome called stone filled gallbladder. The types of problems may be broken down roughly 2. Cholecystoses (adenomyosis and cholesterolosis). into three major groups: technical, anatomical and 3. Intramural gas called stones or cholecystosis. diagnostic. Technical problems relate to choice and 4. Porcelain gallbladder. 5. Milk ofcalcium bile. 6. Sludge called tumour, polyp or stone and vice versa. Correspondence: E.J. Fitzgerald, M.B., M.R.C.P.I., 7. Gallbladder thickening called cholecystitis. F.R.C.R. 8. Post-cholecystectomy scar and clips called disease. *Present address: Toronto General Hospital, 200 Elizabeth 9. Food and gas called stones after cholecystoenterostomy. Street, Toronto, Ontario, Canada M5G 2C4 10. Asymptomatic gallstones taken as cause ofsymptoms. Accepted: 16 December 1986 11. Cancer not recognized or considered. © The Fellowship of Postgraduate Medicine, 1987 526 E.J. FITZGERALD & A. TOI Postgrad Med J: first published as 10.1136/pgmj.63.741.525 on 1 July 1987. Downloaded from use of equipment and performance of the ultrason- ographic examination. Anatomical problems relate to normal anatomical variants as well as physiological changes .in the gallbladder and bile which may be misinterpreted as disease. Diagnostic problems relate to errors of interpretation of ultrasonographic appearances. Technical problems For elective studies, the patient should be fasted for 12 hours to allow adequate gallbladder distension to aid the examination and to prevent mistaking as abnor- mal, the normally thickened wall of the physio- logically contracted gallbladder.6 Incorrect identification of another organ (bowel, stomach, duodenum, aorta, ligamentus teres)7 as the gallbladder will cause errors. Only the meticulous identification of landmarks such as the right portal vein and following the main lobar fissure to the gallbladder can avoid such errors. We have encoun- Figure 1 Stones and polyp (arrow) in the gallbladder. tered a case of an ovarian dermoid on a long pedicle Note the clear shadowing behind the calculi and the migrating to the subhepatic fossa adjacent to the absence of shadow behind the polyp. gallbladder. Torsion of the pedicle led to pain and tenderness typical of gallbladder disease. Ultrason- ographically, this mass mimicked cholecystitis, with associated with intestinal gas.'2"3 We have found this 'stones' and debris which shadowed and moved with to be a difficult sign to employ with confidence. copyright. alteration of patient position. Failure to move the patient during the examination Once the gallbladder has been located, the examiner is another source of error. Gallstones are diagnosed must choose transducers with a suitable focal range. most confidently if they can be shown to move during The common transducers used for abdominal examin- the examination by having the patient assume a ation (3.5 MHz long focus) often give poor, noise filled decubitus or erect position.'0 We have all too frequen- images of the gallbladder which may lie only 2-3 cm tly seen stones for the first time when they moved as from the skin. Such gallbladders are adequately the patient changed position (Figures 2a and b). examined only with smaller crystal transducers of Artifactual side lobe echoes from adjacent struc- higher frequency (e.g. 5 MHz) having a focal zone at tures are frequently written into the gallbladder lumen http://pmj.bmj.com/ the gallbladder depth. We do not hesitate to employ where they can be mistaken for sludge or calculi.'4 high frequency linear array scanners ifthe gallbladder Such spurious echoes are not constant as the trans- is very superficial and obscured in the main beam noise ducer or patient are moved. The operator needs to be zone of the sector equipment. Alternatively with such familiar with the artifactual echoes peculiar to his/her superficial gallbladders, a standoff device may be used equipment. or the liver itself may be employed as a standoff to There are some patients whose habitus will defeat place the gallbladder within the focal zone of the the most skilled examiner. In such cases we recom- on October 6, 2021 by guest. Protected transducer. mend further gallbladder evaluation with alternative The absence of a distal acoustic shadow reduces the imaging techniques. probability ofan echo being a gallstone from 100% to 61 %.'° All gallstones should cast shadows irrespective Anatomical and physiological variants of size or composition." The demonstration of such shadows is entirely dependent on an appropriately Several normal anatomical structures and variants in, narrow beam profile, as determined by transducer and about, the gallbladder have been mistaken for selection and machine settings. Ifthe calculus can stop disease. Similarly, varying normal physiological states enough of the beam to prevent sound transmission may create problems. beyond it, shadowing will occur (Figure 1). Folds are frequently present in the gallbladder. The characteristics of the 'shadow' have also been They cause confusing echoes and they may cast utilized. A calculus' shadow is said to be 'clean' and shadows.'5 The junctional fold at the junction of the sharply defined. This is contrasted to the indistinctly body and infundibulum of the gallbladder and the marginated and reverberation echo filled 'shadow' folds of the valves of Heister are a common source of ULTRASOUND AND GALLBLADDER DISEASE 527 Postgrad Med J: first published as 10.1136/pgmj.63.741.525 on 1 July 1987. Downloaded from Figure 3 A kink in the hepatic artery near the neck ofthe gallbladder creates a strong specular echo and shadow which mimic a calculus in the gallbladder neck. Views in other directions and Doppler assessment revealed its true identity. Note also that the adjacent gallbladder is filled with sludge and virtually isoechoic with the liver. It is recognized only through identification of the subtle gallbladder-liver interface line (arrows). copyright. or folded neck of gallbladder may mimic a dilated common bile duct.'9 Failure to demonstrate a physiologically distended gallbladder in a fasting patient is reported to indicate a diseased gallbladder.'0"2 In our experience, it is very rare not to be able to locate an even minute, contrac- ted, diseased gallbladder if correct transducers and techniques are employed. We have, however, encoun- http://pmj.bmj.com/ tered gallbladders which are distended with echogenic bile that is iso-echoic with liver. This renders the Figure 2 (a) The multiple gallstones layered on the gallbladder invisible until the specular echo of its wall dependent gallbladder wall are difficult to detect as machine gains are too high and transducer focus is too becomes visible or a small pocket of non-echogenic deep. (b) the calculi become easily visible when the patient bile is identified (Figure 3). Gallbladder