Gallstones (Cholelithiasis) Workup_ Approach Considerations, Blood Studies, Abdominal Radiography

10/13/2015 Gallstones (Cholelithiasis) Workup: Approach Considerations, Blood Studies, Abdominal Radiography

http://emedicine.medscape.com/article/175667workup 1/6

Gallstones (Cholelithiasis) WorkupAuthor: Douglas M Heuman, MD, FACP, FACG, AGAF; Chief Editor: Julian Katz, MD more...

Updated: Jan 20, 2015

Approach ConsiderationsPatients with uncomplicated cholelithiasis or simple biliary colic typically havenormal laboratory test results. Laboratory testing is generally not necessary unlesscholecystitis is a concern.[10]

Asymptomatic gallstones are often found incidentally on plain radiographs,abdominal sonograms, or CT scan for workup of other processes. Plain radiographshave little role in the diagnosis of gallstones or gallbladder disease. Cholesterol andpigment stones are radiopaque and visible on radiographs in only 1030% ofinstances, depending on their extent of calcification.

Blood StudiesIn patients with suspected gallstone complications, blood tests should include acomplete blood cell (CBC) count with differential, liver function panel, and amylaseand lipase.

Acute cholecystitis is associated with polymorphonuclear leukocytosis. However, upto one third of the patients with cholecystitis may not manifest leukocytosis.

In severe cases, mild elevations of liver enzymes may be caused by inflammatoryinjury of the adjacent liver.

Patients with cholangitis and pancreatitis have abnormal laboratory test values.Importantly, a single abnormal laboratory value does not confirm the diagnosis ofcholedocholithiasis, cholangitis, or pancreatitis; rather, a coherent set of laboratorystudies leads to the correct diagnosis.

Choledocholithiasis with acute common bile duct (CBD) obstruction initiallyproduces an acute increase in the level of liver transaminases (alanine andaspartate aminotransferases), followed within hours by a rising serum bilirubin level.The higher the bilirubin level, the greater the predictive value for CBD obstruction.CBD stones are present in approximately 60% of patients with serum bilirubin levelsgreater than 3 mg/dL.

If obstruction persists, a progressive decline in the level of transaminases with risingalkaline phosphatase and bilirubin levels may be noted over several days.Prothrombin time may be elevated in patients with prolonged CBD obstruction,secondary to depletion of vitamin K (the absorption of which is biledependent).Concurrent obstruction of the pancreatic duct by a stone in the ampullaof Vater may be accompanied by increases in serum lipase and amylase levels.

Repeated testing over hours to days may be useful in evaluating patients withgallstone complications. Improvement of the levels of bilirubin and liver enzymesmay indicate spontaneous passage of an obstructing stone. Conversely, rising levelsof bilirubin and transaminases with progression of leukocytosis in the face ofantibiotic therapy may indicate ascending cholangitis with need for urgentintervention. Blood culture results are positive in 3060% of patients withcholangitis.

Abdominal RadiographyUpright and supine abdominal radiographs are occasionally helpful in establishing adiagnosis of gallstone disease.

Black pigment or mixed gallstones may contain sufficient calcium to appearradiopaque on plain films. The finding of air in the bile ducts on plain films mayindicate development of a choledochoenteric fistula or ascending cholangitis withgasforming organisms. Calcification in the gallbladder wall (the socalled porcelaingallbladder) is indicative of severe chronic cholecystitis.

The main role of plain films in evaluating patients with suspected gallstone diseaseis to exclude other causes of acute abdominal pain, such as intestinal obstruction,visceral perforation, renal stones, or chronic calcific pancreatitis.

Go to Imaging of Cholelithiasis for complete information on this topic.

UltrasonographyUltrasonography is the procedure of choice in suspected gallbladder or biliarydisease; it is the most sensitive, specific, noninvasive, and inexpensive test for thedetection of gallstones. Moreover, it is simple, rapid, and safe in pregnancy, and itdoes not expose the patient to harmful radiation or intravenous contrast. An addedadvantage is that it can be performed by skilled practitioners at the bedside. TheAmerican College of Radiology (ACR) in its Appropriateness Criteria right upperquadrant pain, published in 2010, supports this conclusion.[11]

Sensitivity is variable and dependent upon operator proficiency, but in general, it ishighly sensitive and specific for gallstones greater than 2 mm. It is less so formicrolithiasis or biliary sludge.

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Ultrasonography is very useful for diagnosing uncomplicated acute cholecystitis. Thesonographic features of acute cholecystitis include gallbladder wall thickening (>5mm), pericholecystic fluid, gallbladder distention (>5 cm), and a sonographic Murphysign. The presence of multiple criteria increases its diagnostic accuracy.

Gallstones appear as echogenic foci in the gallbladder. They move freely withpositional changes and cast an acoustic shadow. (See the image below.)

Cholecystitis with small stones in the gallbladder neck. Classic acoustic shadowing is seenbeneath the gallstones. The gallbladder wall is greater than 4 mm. Image courtesy of DTSchwartz.

Ultrasonography is also helpful in cases of suspected acute cholecystitis to excludehepatic abscesses and other liver parenchymal processes.

When the gallbladder is completely filled with gallstones, the stones may not bevisible on ultrasound. However, closely spaced double echogenic lines (one from thegallbladder wall and one from the stones) with acoustic shadowing may be evident.(See the images below.)

The WES (wall echogenic shadow) sign, long axis of the gallbladder. The arrow head points tothe gallbladder wall. The second hyperechoic line represents the edge of the congregatedgallstones. Acoustic shadowing (AS) is readily seen. The common bile duct can be seen justabove the portal vein (PV). Image courtesy of Stephen Menlove.

WES sign, short axis view of the gallbladder. Image courtesy of Stephen Menlove.

Common bile duct (CBD) stones are missed frequently on transabdominalultrasonography (sensitivity, 1540%). The detection of CBD stones is impeded bythe presence of gas in the duodenum, possible reflection and refraction of thesound beam by curvature of the duct, and the location of the duct beyond theoptimal focal point of the transducer.

On the other hand, dilatation of the CBD on ultrasonographic images is an indirectindicator of CBD obstruction. CBD dilatation is identified accurately, with up to 90%accuracy. However, this finding may be absent if the obstruction is of recent onset.The usefulness of ultrasonography findings as a predictor of CBD stones is at best1520%.


Endoscopic ultrasound




Endoscopic ultrasound (EUS) is also an accurate and relatively noninvasivetechnique to identify stones in the distal common bile duct. Sensitivity andspecificity of CBD stone detection are reported in range of 85100%.[12]

Laparoscopic ultrasound

Laparoscopic ultrasound has shown some promise as a primary method for bile ductimaging during laparoscopic cholecystectomy.[13] Yao et al were able to evaluatethe common bile duct with laparoscopic ultrasound during laparoscopiccholecystectomy in 112 of 115 patients (97.4%) with cholelithiasis.

In patients who were categorized preoperatively as having a low probability of bileduct stones, the occurrence rate of stones was found to be 7%; in those who werepreoperatively assessed as having an intermediate probability of such stones, theoccurrence rate was 36.4%; and in those who were rated with the highest probabilityof bile duct stones, the occurrence rate was 78.9%.[13]

The investigators suggested that as experience increases with laparoscopicultrasound, this method may become routine for evaluating the bile duct duringlaparoscopic cholecystectomy. In addition, Yao et al advised mandatory aggressivepreoperative evaluation of the common bile duct in those who are suspected tohave an intermediate or high risk of having choledocholithiasis.[13]

Computed TomographyComputed tomography (CT) scanning is more expensive and less sensitive thanultrasonography for the detection of gallbladder stones. CT scanning is often usedin the workup of abdominal pain, as it provides excellent images of all theabdominal viscera. CT scanning is superior to ultrasonography for the demonstrationof gallstones in the distal common bile duct.

Gallstones are often found incidentally on CT. Findings on CT for acute cholecystitisare similar to those found on sonograms. Although not the initial study of choice inbiliary colic, CT can be used in diagnostic challenges or to further characterizecomplications of gallbladder disease. CT is particularly useful for the detection ofintrahepatic stones or recurrent pyogenic cholangitis.


Magnetic Resonance ImagingMagnetic resonance imaging (MRI) with magnetic resonancecholangiopancreatography (MRCP) has emerged as an excellent imaging study fornoninvasive identification of gallstones anywhere in the biliary tract, including thecommon bile duct (see the image below). Because of its cost and the need forsophisticated equipment and software, it is usually reserved for cases in whichcholedocholithiasis is suspected. The 2010 ACR guidelines recommend MRI as asecondary imaging study if ultrasound images do not result in a clear diagnosis ofacute cholecystitis or gallstones.[11]

Magnetic resonance cholangiopancreatography (MRCP) showing 5 gallstones in the commonbile duct (arrows). In this image, bile in the duct appears white; stones appear as darkfillingdefects. Similar images can be obtained by taking plain radiographs after injection ofradiocontrast material in the common bile duct, either endoscopically (endoscopic retrogradecholangiography) or percutaneously under fluoroscopic guidance (percutaneous transhepaticcholangiography), but these approaches are more invasive.


Scintigraphy

Technetium99m (99m Tc) hepatoiminodiacetic acid (HIDA) scintigraphy isoccasionally useful in the differential diagnosis of acute abdominal pain.Scintigraphy gives little information about nonobstructing cholelithiasis and cannotdetect other pathologic states, but it is highly accurate for the diagnosis of cysticduct obstruction.

HIDA is normally taken up by the liver and excreted into bile, where it fills thegallbladder and can be detected with a gamma camera. Failure of HIDA to fill thegallbladder, while flowing freely into the duodenum, is indicative of cystic ductobstruction. A nonvisualizing gallbladder on a HIDA scan in a patient withabdominal pain supports a diagnosis of acute cholecystitis.

A metaanalysis by Mahid et al found that patients without gallstones who haveright upper quadrant pain and a positive HIDA scan result are more likely toexperience symptom relief if they undergo cholecystectomy than if they are treated





medically.[14]

Endoscopic Retrograde CholangiopancreatographyEndoscopic retrograde cholangiopancreatography (ERCP) permits radiographicimaging of the bile ducts. In this procedure, an endoscope is passed into theduodenum and the papilla of Vater is cannulated. Radiopaque liquid contrast isinjected into the biliary ducts, providing excellent contrast on radiographic images.Stones in bile appear as filling defects in the opacified ducts. Currently, ERCP isusually performed in conjunction with endoscopic retrograde sphincterotomy andgallstone extraction.[15]

Percutaneous Transhepatic CholangiographyPercutaneous transhepatic cholangiography (PTC) may be the modality of choice inpatients in whom ERCP is difficult (eg, those with previous gastric surgery or distalobstructing CBD stone), in the absence of an experienced endoscopist, and inpatients with extensive intrahepatic stone disease and cholangiohepatitis. A longlargebore needle is advanced percutaneously and transhepatically into anintrahepatic duct, and cholangiography is performed. A catheter can be placed inthe biliary tree over a guidewire.

Uncorrected coagulopathy is a contraindication for PTC, and the normal size of theintrahepatic ducts makes the procedure difficult. Prophylactic antibiotics arerecommended to reduce the risk of cholangitis.

Treatment & Management

Contributor Information and DisclosuresAuthorDouglas M Heuman, MD, FACP, FACG, AGAF Chief of Hepatology, Hunter Holmes McGuire Department ofVeterans Affairs Medical Center; Professor, Department of Internal Medicine, Division of Gastroenterology,Virginia Commonwealth University School of Medicine

Douglas M Heuman, MD, FACP, FACG, AGAF is a member of the following medical societies: AmericanAssociation for the Study of Liver Diseases, American College of Physicians, American GastroenterologicalAssociation

Disclosure: Received grant/research funds from Novartis for other; Received grant/research funds from Bayer forother; Received grant/research funds from Otsuka for none; Received grant/research funds from Bristol MyersSquibb for other; Received none from Scynexis for none; Received grant/research funds from Salix for other;Received grant/research funds from MannKind for other.

Coauthor(s)Jeff Allen, MD Assistant Professor, Department of Surgery, University of Louisville

Disclosure: Nothing to disclose.

Anastasios A Mihas, MD, DMSc, FACP, FACG Professor, Department of Medicine, Division ofGastroenterology, Virginia Commonwealth University School of Medicine; Consulting Staff, VirginiaCommonwealth University Hospitals and Clinics; Chief of GI Clinical Research, Director of GI Outpatient Service,Associate Director of Hepatology, Hunter Holmes McGuire Veterans Affairs Medical Center

Anastasios A Mihas, MD, DMSc, FACP, FACG is a member of the following medical societies: AmericanAssociation for the Study of Liver Diseases, American College of Gastroenterology, American College ofPhysicians, American Gastroenterological Association, American Society for Gastrointestinal Endoscopy, SigmaXi, Southern Society for Clinical Investigation, American Federation for Clinical Research, GastroenterologyResearch Group


Chief EditorJulian Katz, MD Clinical Professor of Medicine, Drexel University College of Medicine

Julian Katz, MD is a member of the following medical societies: American College of Gastroenterology,American College of Physicians, American Gastroenterological Association, American Geriatrics Society,American Medical Association, American Society for Gastrointestinal Endoscopy, American Society of Law,Medicine & Ethics, American Trauma Society, Association of American Medical Colleges, Physicians for SocialResponsibility


AcknowledgementsFirass Abiad, MD Head of Division, General and Laparoscopic Surgery, Specialized Medical Center Hospital,Saudi Arabia


BS Anand, MD Professor, Department of Internal Medicine, Division of Gastroenterology, Baylor College ofMedicine

BS Anand, MD is a member of the following medical societies: American Association for the Study of LiverDiseases, American College of Gastroenterology, American Gastroenterological Association, and AmericanSociety for Gastrointestinal Endoscopy


David Eric Bernstein, MD Director of Hepatology, North Shore University Hospital; Professor of ClinicalMedicine, Albert Einstein College of Medicine

David Eric Bernstein, MD is a member of the following medical societies: American Association for the Study ofLiver Diseases, American College of Gastroenterology, American College of Physicians, AmericanGastroenterological Association, and American Society for Gastrointestinal Endoscopy


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Barry E Brenner, MD, PhD, FACEP Professor of Emergency Medicine, Professor of Internal Medicine,Program Director, Emergency Medicine, Case Medical Center, University Hospitals, Case Western ReserveUniversity School of Medicine

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David FM Brown, MD Associate Professor, Division of Emergency Medicine, Harvard Medical School; ViceChair, Department of Emergency Medicine, Massachusetts General Hospital

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William K Chiang, MD Associate Professor, Department of Emergency Medicine, New York University Schoolof Medicine; Chief of Service, Department of Emergency Medicine, Bellevue Hospital Center

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Alfred Cuschieri, MD, ChM, FRSE, FRCS, Head, Professor, Department of Surgery and Molecular Oncology,University of Dundee, UK


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David Greenwald, MD Associate Professor of Clinical Medicine, Fellowship Program Director, Department ofMedicine, Division of Gastroenterology, Montefiore Medical Center, Albert Einstein College of Medicine

David Greenwald, MD is a member of the following medical societies: Alpha Omega Alpha, American College ofGastroenterology, American College of Physicians, American Gastroenterological Association, American Societyfor Gastrointestinal Endoscopy, and New York Society for Gastrointestinal Endoscopy


Eugene Hardin, MD, FAAEM, FACEP Former Chair and Associate Professor, Department of EmergencyMedicine, Charles Drew University of Medicine and Science; Former Chair, Department of Emergency Medicine,Martin Luther King Jr/Drew Medical Center


Faye Maryann Lee, MD Staff Physician, Department of Emergency Medicine, New York University/BellevueHospital Center

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Sally Santen, MD Program Director, Assistant Professor, Department of Emergency Medicine, VanderbiltUniversity

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Assaad M Soweid, MD, FASGE, FACG Associate Professor of Clinical Medicine, Endosonography andAdvanced Therapeutic Endoscopy, Director, EndoscopyBronchoscopy Unit, Division of Gastroenterology,Department of Internal Medicine, American University of Beirut Medical Center, Lebanon

Assaad M Soweid, MD, FASGE, FACG is a member of the following medical societies: American College ofGastroenterology, American College of Physicians, American College of PhysiciansAmerican Society of InternalMedicine, American Gynecological and Obstetrical Society, and American Medical Association


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References

1. Heuman DM, Moore EL, Vlahcevic ZR. Pathogenesis and dissolution of gallstones. Zakim D, Boyer TD,eds. Hepatology: A Textbook of Liver Disease. 3rd ed. Philadelphia, Pa: WB Saunders; 1996. 1996: 376417.

2. Center SA. Diseases of the gallbladder and biliary tree. Vet Clin North Am Small Anim Pract. 2009 May.39(3):54398. [Medline].

3. Portincasa P, Moschetta A, Palasciano G. Cholesterol gallstone disease. Lancet. 2006 Jul 15.368(9531):2309. [Medline].

4. Poupon R, Rosmorduc O, Boëlle PY, Chrétien Y, Corpechot C, Chazouillères O, et al. Genotypephenotype relationships in the lowphospholipid associated cholelithiasis syndrome. A study of 156

http://www.alphaomegaalpha.org/

http://www.aaem.org/

http://www.chestnet.org/

http://www.acep.org/


http://www.americanheart.org/presenter.jhtml?identifier=1200000

http://www.thoracic.org/

http://www.arkmed.org/cgi-bin/cgiwrap/arkmed/start.cgi/dev05/setup.html

http://www.nyam.org/

http://www.nyas.org/

http://www.saem.org/



http://www.clintox.org/

http://www.acmt.net/


http://www.aast.org/

http://www.facs.org/

http://www.ama-assn.org/

http://www.amtrauma.org/

http://www.cmanet.org/

http://www.sccm.org/

http://www.alphaomegaalpha.org/





http://www.nysge.org/

http://www.pbk.org/






http://www.agosonline.org/

http://www.ama-assn.org/

http://reference.medscape.com/medline/abstract/19524793





Medscape Reference © 2011 WebMD, LLC

consecutive patients. Hepatology. 2013 Mar 26. [Medline].

5. Halldestam I, Kullman E, Borch K. Incidence of and potential risk factors for gallstone disease in a generalpopulation sample. Br J Surg. 2009 Nov. 96(11):131522. [Medline].

6. Shaffer EA. Epidemiology and risk factors for gallstone disease: has the paradigm changed in the 21stcentury?. Curr Gastroenterol Rep. 2005 May. 7(2):13240. [Medline].

7. Wang HH, Liu M, Clegg DJ, Portincasa P, Wang DQ. New insights into the molecular mechanismsunderlying effects of estrogen on cholesterol gallstone formation. Biochim Biophys Acta. 2009 Nov.1791(11):103747. [Medline]. [Full Text].

8. Gilani SN, Bass G, Leader F, Walsh TN. Collins' sign: validation of a clinical sign in cholelithiasis. Ir J MedSci. 2009 Aug 14. [Medline].

9. Zaliekas J, Munson JL. Complications of gallstones: the Mirizzi syndrome, gallstone ileus, gallstonepancreatitis, complications of "lost" gallstones. Surg Clin North Am. 2008 Dec. 88(6):134568, x. [Medline].

10. Dauer M, Lammert F. Mandatory and optional function tests for biliary disorders. Best Pract Res ClinGastroenterol. 2009. 23(3):44151. [Medline].

11. [Guideline] Katz DS, Rosen MP, Blake MA, et al; and Expert Panel on Gastrointestinal Imaging. ACRAppropriateness Criteria® right upper quadrant pain. [online publication]. Reston (VA): American College ofRadiology (ACR). [Full Text].

12. Shapiro T, Melzer E, Binder Y, Keter D, Zbar A, Miller R, et al. Selective Utilization of PreOperativeEndoscopic Ultrasound to Exclude Choledocholithiasis Prior to Laparoscopic Cholecystectomy: ARetrospective Study. Hepatogastroenterology. 2013 May 1. 60(123):[Medline].

13. Yao CC, Huang SM, Lin CC, Ho LC, Chang SW, Chen HM, et al. Assessment of common bile duct usinglaparoscopic ultrasound during laparoscopic cholecystectomy. Surg Laparosc Endosc Percutan Tech. 2009Aug. 19(4):31720. [Medline].

14. Mahid SS, Jafri NS, Brangers BC, Minor KS, Hornung CA, Galandiuk S. Metaanalysis of cholecystectomyin symptomatic patients with positive hepatobiliary iminodiacetic acid scan results without gallstones. ArchSurg. 2009 Feb. 144(2):1807. [Medline].

15. [Guideline] NIH stateofthescience statement on endoscopic retrograde cholangiopancreatography(ERCP) for diagnosis and therapy. NIH Consens State Sci Statements. 2002 Jan 1416. 19(1):126.[Medline].

16. Binenbaum SJ, Teixeira JA, Forrester GJ, Harvey EJ, Afthinos J, Kim GJ, et al. Singleincisionlaparoscopic cholecystectomy using a flexible endoscope. Arch Surg. 2009 Aug. 144(8):7348. [Medline].

17. Ghazal AH, Sorour MA, ElRiwini M, ElBahrawy H. Singlestep treatment of gall bladder and bile ductstones: a combined endoscopiclaparoscopic technique. Int J Surg. 2009 Aug. 7(4):33846. [Medline].

18. Schirmer BD, Winters KL, Edlich RF. Cholelithiasis and cholecystitis. J Long Term Eff Med Implants.2005. 15(3):32938. [Medline].

19. [Guideline] Overby DW, Apelgren KN, Richardson W, Fanelli R. SAGES guidelines for the clinicalapplication of laparoscopic biliary tract surgery. Surg Endosc. 2010 Oct. 24(10):236886. [Medline]. [FullText].

20. Dan DV, Harnanan D, Maharaj R, Seetahal S, Singh Y, Naraynsingh V. Laparoscopic cholecystectomy:analysis of 619 consecutive cases in a Caribbean setting. J Natl Med Assoc. 2009 Apr. 101(4):35560.[Medline].

21. Gurusamy K, Sahay SJ, Burroughs AK, Davidson BR. Systematic review and metaanalysis ofintraoperative versus preoperative endoscopic sphincterotomy in patients with gallbladder and suspectedcommon bile duct stones. Br J Surg. 2011 Jul. 98(7):90816. [Medline].

22. Behar J, Corazziari E, Guelrud M, Hogan W, Sherman S, Toouli J. Functional gallbladder and sphincter ofoddi disorders. Gastroenterology. 2006 Apr. 130(5):1498509. [Medline].

23. Anderloni A, Ballarè M, Pagliarulo M, Conte D, Galeazzi M, Orsello M, et al. Prospective evaluation ofearly endoscopic ultrasonography for triage in suspected choledocholithiasis: Results from a large singlecentre series. Dig Liver Dis. 2013 Dec 28. [Medline].

24. Reuters Health. Endoscopic ultrasound a good first step when gallstones are suspected. Medscape MedicalNews. January 10, 2014. Available at http://www.medscape.com/viewarticle/819024. Accessed: January20, 2014.





http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2756670/




http://www.acr.org/~/media/ACR/Documents/AppCriteria/Diagnostic/RightUpperQuadrantPain.pdf









http://www.sages.org/publication/id/06/





http://www.medscape.com/viewarticle/819024