Ultrasound Examination of Gallstone - Term Paper Example

LITERATURE REVIEW: ULTRASOUND EXAMINATION OF GALLSTONE Name Student ID Institution Course Literature Review: Ultrasound Examination of Gallstone Introduction Gallstones refer to small stones mainly composed of cholesterol which develop in the gallbladder. The gallbladder refers to a minute, pouch-like structure located below the liver. It is mainly 8cm in length and 4 cm in diameter when full. Its major role is digestion of fats and it is linked to the liver via the bile ducts. In majority of the cases, gallstones are not associated with any symptoms and do not require any form of treatment.3 The complications mainly associated cholelithiasis includes gallbladder inflammation which causes severe pain, jaundice, and fever of up to 38oC.2 In some instances, gallstones migrate to organs such as the pancreas leading to inflammation and irritation.10 This condition is referred to as acute pancreatitis and is associated with abdominal pains which gradually worsen. Reports indicate that gallstones result from lack of balance in the chemical components of bile which in the gallbladder.2 In many of the cases, the concentration of cholesterol gets too high and the surplus cholesterol form stones. From reports, overweight persons, people above 40 and females have a greater risk of developing gallstones compared to the rest of the population.4 Other reports argue that factors which increase the chances of gallstone development include the use of hormone replacement therapy, pregnancy, and rapid weight loss. Treatment of gallstones is only essential if the gallstones cause any symptoms including abdominal pains.1 This paper seeks to discuss gallstones and the ultra sound examination of cholelithiasis. Ultrasound scan refers to a simple test which utilizes sound waves to develop images of organs and structures inside the body. It is the most common test for gallstone examination and utilizes sound waves and it does not cause any harm. Ultrasound is a high frequency sound which cannot be heard but it is released and detected by special machines. For instance, the ultrasound may travel smoothly through the blood but when it comes across a solid region, it echoes back. When ultra sound travels in the gallbladder, it echoes back powerfully when it comes across a solid gallstone. Hence, as ultra sound comes across various structures of varying density inside the body, echoes of distinct powers are sent back. Overview of Anatomy The gallbladder refers to a section of a system of structures which are jointly referred to as the biliary tree which transports bile from the liver to the duodenum for digestion purposes.11 The cystic duct, hepatic ducts, and bile ducts are also part of the biliary tree. A small pear-shaped sac situated beneath the liver, is the gallbladder whose size varies but does not exceed 4cm long in normal instances. 10 It comprises of round fundus, smoothened body, and tightening neck which links to the portal hepatic vein. The cystic duct links with the hepatic duct forming the ordinary bile duct. Many authors suggest the role of the gallbladder is to provide a reservoir that stores and concentrates bile. Bile is secreted by the liver and comprises of a wide range of elements such as mucin, fatty acids, lecithin, and cholesterol.8 The gallbladder is able to store about 50mls of bile and may increase bile’s concentration significantly. Some reports state that the presence of food stimulates the release of bile from the gallbladder. 16However, it is also reported that hormone cholecystokinin also stimulates the contraction of the gallbladder to facilitate release of bile. 17 Abnormalities of the Gallbladder Abnormal reports on the gallbladder may include anatomic inconsistencies and pathogenic conditions. Gallstones (cholelithiasis) are the most common abnormalities of the gallbladder. The primary concern for detection of gallstones is the NHANES 111. The most reliable method for detecting gallstones is the ultrasound examination and it is reported to be over 95% effective. Gallstones originate from variation in concentration of bile components. Changes in the normal concentration of bile components lead to the dissolving of cholesterol in Lecithin and Bile salts which precipitates out and forms stones.2 Other reports argue that various levels of calcium salts and other components may be inclusive during gallstone formation and that stones that compose of pure cholesterol are not common.9 Small gallstones may move into the small intestines through the ducts. Large stones lodge the gallbladder especially at the neck region and the bile duct where they lead to pain in the muscles and my prevent bile from entering the intestines preventing proper digestion and fat storage. As bile is continuously produced by the liver, pressure increases in the occluded canal and bile pigments move to the blood and tissues whey they build up resulting to jaundice which refers to skin yellowing.12 Other reports state that stones may be located at the juncture linking bile and pancreatic duct preventing the movement of bile and pancreatic juice which completely seizes digestion and absorption.15 Cholecystitis refers to an inflammation of the gallbladder which results from stones within the gallbladder or its ducts. Chronic conditions may be fatal and require urgent medical attention. Chronic conditions are demonstrated in a chain of attacks and abdominal pains.1 The gallbladder thickens in both acute and chronic conditions, but this is not used as diagnostic tool for gallstones. Principles of Operations The working principle for ultrasound in gallstone examination is similar from a wide range of sources. Ultrasound for diagnostics utilizes high frequency waves in production of images of organs inside the body.5 The theory behind sonography is the piezoelectric effect which refers to electrical stimulation of a quatz crystal to produce ultrasound waves. The frequencies of these waves are beyond the frequency range of human ear. The sound waves produced by the crystal are transmitted to the tissues, reflection occurs, and a visual image is formed. The image is then utilized to study any abnormalities in the organs. Ultrasound waves are transmitted through a medium since sound must travel through medium. It moves in longitudinal waves which ratify molecules and produce to and fro motion which is moved amid molecules to the path of the wave. The space amid molecules and medium composition are significant to the transmission of sound waves. Some reports state that materials with high density assist in ultrasound transmission while great spaces amid molecules make it difficult for propagation of waves.12 Also, it is reported that the capability of the molecules to undergo compression and ratification determines propagation of ultrasound. Molecules that are not easily compressible are not effective for transmission of ultrasound. Thus, the speed of sound waves depends on the density and whether the medium can be compressed. Velocity is significant as it must be accurately determined for calibration of tools. Wave frequency in turn influences the transmission of the ultrasound. With increase in frequency, the wavelength is reduced significantly. When the frequency is high; it is easy to achieve the he desired resolution. However, the penetration is minimized. On the other hand, while low frequencies lead to poor resolution for images, they have a powerful penetration capacity. Biological tissues are able to cause a reflection of ultrasound within tissue interfaces. 13 The ability to reflect is not constant and depends on density, compressibility, and speed of the beam. Alteration in the impedance of tissues leads to reflection of the ultrasound. The irregularity in impedance enables observation of tissue structures, specifically soft tissues. Ultrasound waves directed to body organs should be transmitted at right angled direction to the surfaces, if not; the waves will be refracted which minimizes the level of reflection.15 At a point referred to as the critical angle, the beam is totally reflected at the interface and no reflected wave is detectable. The piezoelectric crystal is housed by the transducer and it changes electrical energy to sonic energy and returns echoes to electrical energy. Image resolution is achieved by use of a transducer which links the correct frequency with the matching focal zone.12 Before undertaking the examination, the persons are not allowed to eat anything 6 hours prior to the test. During an ultra sound, the patient is made to lie on a couch and a probe is placed on the skin over the abdominal region.5 There are different types of ultrasound transducers. In some cases the probe is similar to an extremely thick pen and lubricating jelly is applied on the skin to ensure proper contact between the probe and the body. The probe is linked to an ultrasound machine and a monitor. Ultrasound frequencies are passed on from the probe to the body, which then echo back. The echoes are displayed as images on the monitor. Abdominal ultrasound is the best test to confirm gallstones. Normal Appearance A normal gallbladder appearance is an oval organ, which do not have any echoes and located beneath the liver. Through a sonographic test, a gallbladder should appear thin-walled and should not form echoes. It is pear shaped and located in the Right Upper Quadrant. The size depends on the amount of bile present. Gallstones are observed in both chronic and acute cholecystitis. Nevertheless, it is also reported that gallstones may also be present in people who do not show any symptoms.6 Various appearances are present. The first appearance is shadowing whereby, a stone within the bile is seen an echogenic object within the liquid. Sound waves cannot pass through them which cause shadowing. A stone which is bigger than 2mm will absorb sound and cause reflection, and shed an auditory shade in the posterior of the stone. The second appearance is stones without shadowing. 14Minute stones may not form acoustic shades. Movement an echogenic focus after moving the ultrasound machine indicates presence of a possible stone. The third appearance is the gravel. If a person has many stones, the stones settle in most dependent regions of the gallbladder. Individual stones may not be determinable; however, while shadowing may not occur, uneven echoes are observed. The next appearance is gallstone filled with stones.12 When the gallbladder is full of stones, all the bile is full of stones and stones are seen as numerous dense echoes. At times, stones may appear at fluid level. Such stones are floating on the bile and are seen as an echogenic streak. The last appearance is the adherent stones which are viewed as echoes within the gallbladder with no shadows. Lack of movement of echoes after moving the Ultrasound machine indicates possibility of adherent stones. Wall thickening during ultrasound examination is identified as a line of reducing echogenicity. The wall of a normal gallbladder is about 3mm.14 The two criterions for ultrasound examination of gallstones is an echogenic region inside the gallbladder and acoustic shadowing which is obtainable in both longitudinal and transverse examination. After meeting this criterion, the largest stone is examined and its length obtained. Both views are obtained and recorded on a VCR tape. If the stones do not form shadows, focal zone adjustment may enhance shadowing. Every stone has a specific pathophysiological effect and various risks which distract the balance and solubility of bile materials.2 Billiary microlithiasis is a condition whereby the stones are too small for detection by the current techniques, mainly less than 2mm. Ultrasound is the most effective method of gallstone detection and the latest technology can only detect stones of not less than 2mm, and it is reported to be 95% efficient. The use of ultrasound is fast and is thought to be harmless.7 Use of contrast enhanced ultra sound has greatly enhanced its efficacy in gallstone detection. The limitation of use of ultrasound examination is that it only identifies around 20% of the stones.13 Also, calcified stones may not be easily detected because they are mainly small in size. It is reported that false negatives are common when minute stones are present in the biliary sludge. Other reports argue that, for persons who are obese and those with abdominal wounds, the gallbladder may not be adequately visualized.4 Conclusion This paper has reviewed literature on ultrasound examination of gallstones. Gallstones may not be associated with any kind of symptom. In majority of the cases, gallstones develop from variation of bile components. It is believed that the concentration of cholesterol gets too high and the surplus cholesterol form stones Ultrasound is the most preferred method for detecting gallstones. Studies should be conducted in the future so as to as to come up with a technique that is able to detect gallstones which are less that 2mm in diameter. References 1. Dragos, D, Tanasescu, MD, Comsa, MO, Minca, A, Olteanu, D. Psychological Features Associated With Gallstone Disease. Romanian Medical Journal. of Endocrinology 2015; 62(1). 2. Portincasa, P, Di Ciaula, A, Bonfrate, L, Wang, DQ. Therapy of gallstone disease: What it was, what it is, what it will be. World journal of gastrointestinal pharmacology and therapeutics. 2012; 3(2), 7. 3. Lavoie, B, Nausch, B, Zane, EA, Leonard, MR, Balemba, OB, Bartoo, AC, Mawe, GM. Disruption of gallbladder smooth muscle function is an early feature in the development of cholesterol gallstone disease. Neurogastroenterol Motil. 2012; 24(7), 313-324. 4. Bonfrate, L, Wang, DQ, Garruti, G, Portincasa, P. Obesity and the risk and prognosis of gallstone disease and pancreatitis. Best Practice & Research Clinical Gastroenterology. 2014; 28(4), 623-635. 5. Gallstones-Exams and Tests. [Internet]. [c2015; Cited June 10, 2015], Available from: http://www.webmd.com/digestive-disorders/tc/gallstones-exams-and-tests 6. Gallstones – Diagnosis; [Internet]. [c2013; cited June 10, 2015],Available from http://www.nhs.uk/Conditions/Gallstones/Pages/Diagnosis.aspx 7. Ultrasound | Preparing for an Ultrasound [internet]. [c2015; Cited June 7, 2015], Available from: http://rhmi.com.au/patients/ultrasound/ 8. Rosen, JC, Nicolay, L, Palmer, JS. Principles of Ultrasound. In Pediatric and Adolescent Urologic Imaging. 2014; (pp. 13-29). Springer New York. 9. Venneman, NG, van Erpecum, KJ. Pathogenesis of gallstones. Gastroenterology clinics of North America. 2010; 39(2), 171-183. 10. Acute cholecystitis: MedlinePlus Medical Encyclopedia; [internet. [c2013; Cited 7 June, 2015], Available from http://www.nlm.nih.gov/medlineplus/ency/article/000264.htm 11. 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