Sonography of the Gallbladder
DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER TWO Sonography of the Gallbladder CRT04210 · Ultrasound Imaging START READING NOTES Study Sonography of the Gallbladder using the sections below. Use the topic navigation to continue through Ultrasound Imaging. Contents of This Topic SONOGRAPHY OF THE GALLBLADDER GALLBLADDER MEASUREMENTS NON-DISTENDED GALLBLADDER INADEQUATE FAST NON-FASTING GALLBLADDER ANATOMY OF THE GALLBLADDER GALLBLADDER FOLDS GALLBLADDER SEPTATIONS ANATOMIC VARIANT: THE PHRYGIAN CAP THE GALLBLADDER NECK CYSTIC DUCT CYSTIC DUCT AND BILE DUCT GALLSTONES SMALL CALCULI FALSE GALLSTONES CALCULI OR GAS? CHECK THE CYSTIC DUCT Summary word slide SHADOW PRODUCTION EXPERIMENT WITH GALLSTONE AND FOCAL ZONE SHADOWS NEAR GALLBLADDER CRITICAL ANGLE SHADOWS FROM THE GALLBLADDER SHADOWS NEAR THE GALLBLADDER NON-VISUALIZATION OF THE GALLBLADDER NON-VISUALIZATION OF GB FINDING THE NON-VIZ GALLBLADDER DOUBLE ARC SHADOW SIGN FINDING THE NON-VIZUALIZED GALLBLADDER BOWEL GAS NEAR THE GALLBLADDER SHADOWS NON-SHADOWING ECHOGENIC FOCI IN GB GALLBLADDER POLYPS CHOLESTEROL POLYPS GALLBLADDER MASS SLUDGE SLUDGE AND OBSTRUCTING STONE HEPATIZATION OF THE GALLBLADDER SLUDGE OR LIVER MASS? TUMEFACTIVE SLUDGE GB WALL THICKNESS THICKENENED GALLBLADDER WALL DIFFUSE GB WALL THICKENING GALLBLADDER AND ASCITES IMPACTED GALLSTONE ACUTE CHOLECYSTITIS COMPLICATIONS OF ACUTE CHOLECYSTITIS GANGRENOUS CHOLECYSTITIS PERICHOLECYSTIC COLLECTIONS EMPHYSEMATOUS CHOLECYSTITIS Gallbladders affected by emphysematous cholecystitis are five times more likely to perforate. PORCELAIN GALLBLADDER ACALCULOUS CHOLECYSTITIS HYPERPLASTIC CHOLECYSTOSES ADENOMYOMATOSIS “COMET TAIL” ARTIFACT SCLEROSING CHOLANGITIS GALLBLADDER CARCINOMA SLUDGE AND GALLSTONES DOPPLER FINDINGS IN GALLBLADDER CARCINOMA GB CARCINOMA GALLBLADDER METASTASES SONOGRAPHY OF THE GALLBLADDER SONOGRAPHY OF THE GALLBLADDER Since ultrasound is the primary imaging modality in the evaluation of the gallbladder, it is a “bread and butter” type of study. In patients with right upper quadrant symptoms, ultrasound not only evaluates the gallbladder, but adjacent structures such as liver, bile ducts, pancreas, right kidney and great vessels. SONOGRAPHY OF THE GALLBLADDER The gallbladder is an excellent organ to image by sonography, because it is a fluid-filled structure with no internal echoes. It is visualized as an anechoic pear-shaped structure outlined by a smooth thin wall. Any abnormality within the gallbladder becomes outlined by the bile and is easily seen. SONOGRAPHY OF THE GALLBLADDER As with any structure imaged by ultrasound, it must be examined in two perpendicular (orthogonal) planes in order to be able to reconstruct a proper 3-dimensional mental picture of the object and to avoid artifacts SONOGRAPHY OF THE GALLBLADDER This is a transverse section of the gallbladder. Based on its purely fluid content, the gallbladder is used as a standard of reference for fluid-containing structures in the right upper quadrant. Cysts in the liver and right kidney can be compared to the gallbladder, as long as they are at similar depths. SONOGRAPHY OF THE GALLBLADDER If the echogenicity of their contents is the same as that of the gallbladder, then they are simple cysts. If their contents is more echogenic, then the cysts contain true echoes and are not simple cysts. One should be mindful of the fact that it is possible to have a congenital duplication of the gallbladder, which is rare. Also there are structures that can mimic the gallbladder. These include omental cysts, enteric duplication cysts, choledochal cysts, aneurysms, abscesses. GALLBLADDER MEASUREMENTS The size of the gallbladder is quite variable, so that it is not a very useful indicator of disease. In general the normal gallbladder is < 5cm transversely, and < 10cm longitudinally. A gallbladder larger than this is usually abnormally enlarged, such as a Courvoisier gallbladder, which enlarges on the basis of distal extrahepatic biliary duct obstruction. NON-DISTENDED GALLBLADDER A post-prandial gallbladder cannot be differentiated from an abnormal diseased, contracted gallbladder. An empty gallbladder is difficult to scan and results are unreliable. The gallbladder should always be examined in the fasting state, when it is maximally distended. NON-DISTENDED GALLBLADDER This is accomplished by an overnight fast, usually starting by midnight before the scan. The ultrasound is usually performed in the morning, when the bowel is quiet and abdominal gas is at a minimum. If the patient has not had a proper overnight fast, fasting for approximately 8 hours is considered adequate. INADEQUATE FAST An inadequate fast may result in slight gallbladder wall contraction and mild wall thickening, which in turn may lead to incorrect diagnosis. NON-FASTING GALLBLADDER One should avoid the temptation of scanning the gallbladder without a proper fast. Even if gallstones are visualized, the complete diagnosis may be compromised because of suboptimal visualization, as in this case of a non-fasting patient with right upper quadrant pain. NON-FASTING GALLBLADDER Two gallstones are seen in the fundus (short arrows), but the potentially obstructing stone (long arrow) in the gallbladder neck was not seen until the patient underwent a proper fast. In retrospect the stone was present on the original image shown here (long arrow). ANATOMY OF THE GALLBLADDER The fundus is the rounded curved end of the gallbladder. The body is the central portion, while the neck is the tapered part. The gallbladder is connected to the biliary system by the cystic duct, which contains numerous folds called valves of Heister. Stones are easily trapped within these folds. ANATOMY OF THE GALLBLADDER After the cystic duct joins the common hepatic duct, the extrahepatic bile duct is called the common bile duct. GB TECHNIQUE GALLBLADDER FOLDS Folds within the gallbladders are non-pathologic. A particular fold, called the junctional fold, normally occurs in the mid to proximal end of the gallbladder, closer to the gallbladder neck (arrow). This fold may cause an acoustical shadow due to an artifact and should not be mistaken for a stone or calcification. GALLBLADDER SEPTATIONS Rarely gallbladders contain true septations. These are congenital in origin and are of no clinical significance. A gallbladder folded back upon itself may simulate septations. In fact, sometimes during different degrees of inspiration and expiration, one can observe the gallbladder folding and unfolding. This is of no known clinical consequence. ANATOMIC VARIANT: THE PHRYGIAN CAP When the fundus of the gallbladder folds over on itself, it creates the appearance of a cap, called the “phrygian cap” (arrow). Occurring in 4% of the population, this