Fair Game
ANSWERS – CASE 74
Porcelain Gallbladder
Reference
Middleton WD: The gallbladder. In Goldberg BB (ed): Diagnostic Ultrasound. Baltimore, Williams & Wilkins, 1993, pp 116–142.
Comment
A porcelain gallbladder refers to calcification of the gallbladder wall. This occurs as a result of chronic inflammation and is almost always associated with gallstones. Patients with gallbladder wall calcification are at increased risk of gallbladder cancer. Although the exact risk is not uniformly agreed upon, most authorities agree that patients should undergo a prophylactic cholecystectomy unless there are contraindications to surgery.
The sonographic appearance of porcelain gallbladder depends on the distribution and thickness of the calcification. When the calcification is diffuse and thick, the superficial wall of the gallbladder is seen as a bright, curvilinear reflector with an associated shadow. Because of extensive attenuation of the sound pulse, the back wall is not visible when the calcification is thick. If the calcification is thin, enough sound may penetrate the superficial wall in order to image part of or even the entire back wall. Such is the case in this patient. The ability to see the back wall is important because that excludes a gallbladder full of stones from the differential diagnosis.
The other consideration in this case is emphysematous cholecystitis. Both conditions can appear as a bright, curvilinear line with posterior shadowing. In general, gas appears brighter than calcification, and the shadowing from gas appears dirtier than shadowing from calcification. However, in an individual case these differences may be difficult to rely on. Ring-down artifact, which appears as a bright line trailing deep to the gas, is only seen with gas and does not occur with calcification. In addition, if gas is confined to the lumen of the gallbladder, it is mobile. If there is difficulty in distinguishing gas from calcification based on the sonogram, an abdominal radiograph should be obtained. If it remains unclear after the abdominal radiograph, a CT scan should be obtained.
ANSWERS – CASE 75
Calcific Tendinitis of the Rotator Cuff
Reference
Middleton WD, Teefey SA, Yamaguchi K: Sonography of the shoulder. Semin Musculoskeletal Radiol 1998; 2:211–221.
Comment
Patients with chronic rotator cuff tendinitis may develop areas of calcification within the substance of the cuff. When the calcification is dense and well profiled, it can be seen on shoulder radiographs. However, it is much easier to see with sonography. In fact, sonography is the most accurate means of identifying, localizing, and quantifying rotator cuff calcification. In some centers, ultrasound guidance is used to aspirate areas of calcification. MRI is excellent at detecting most soft tissue abnormalities in the shoulder, but, as elsewhere in the body, it is poor at detecting calcification.
The sonographic appearance of calcific tendinitis is easy to understand. Like other forms of calcium deposition, calcium in the rotator cuff produces an area of increased echogenicity and in most cases an associated acoustic shadow. Extensive spur formation from the greater or lesser tuberosity rarely simulates calcium in the rotator cuff. However, with multiple views, it is usually possible to make this distinction. Fracture fragments embedded in the cuff can also rarely simulate calcific tendonitis. However, these are usually associated with extensive changes in the cortical surface of the bone that are readily apparent on sonography.
ANSWERS – CASE 76
Adenomatous Polyps of the Gallbladder
Reference
Middleton WD: The gallbladder. In Goldberg BB (ed): Diagnostic Ultrasound. Baltimore, Williams & Wilkins, 1993, pp 116–142.
Comment
Large polypoid lesions of the gallbladder may be true polyps or intraluminal material that simulates a polyp, such as tumefactive sludge. Sludge can be distinguished from a true polyp by noting mobility of the lesion. Clotted blood and pus behave like sludge and may simulate polyps but are much less common.
True gallbladder polyps, regardless of their histology, are all composed of viable soft tissue. Therefore, they all have internal blood flow. With current-generation scanners, it is often possible to detect this blood flow with color or power Doppler. Demonstration of flow eliminates sludge or clotted blood from the differential diagnosis. Inability to detect blood flow with Doppler does not help much with the differential diagnosis because some polyps may not have enough flow for it to be detectable.
Polypoid gallbladder neoplasms can arise from any of the elements of the gallbladder wall. Of the benign tumors, adenomatous polyps predominate, but leiomyomas, lipomas, neuromas, and fibromas have all been reported. Gallbladder cancer may also appear as an intraluminal polyp, but these lesions are very rarely seen when they are less than 1 cm in size. In general, the larger the size of the polyp, the more likely it is to be malignant. Polyps that are 5 mm or less can be ignored. Polyps between 5 and 10 mm can be followed to ensure stability. It is not clear when the risk of cancer exceeds the risk of cholecystectomy in patients with polyps. However, it is probably reasonable to remove polyps that are larger than 10 mm, unless there are contraindications to surgery. One should realize, however, that an 11-mm polyp is much less likely to be a cancer than is a 30-mm polyp.
ANSWERS – CASE 77
Cholesterol Polyps of the Gallbladder
Reference
Collett JA, Allan RB, Chisholm RJ, et al: Gallbladder polyps: a prospective study. J Ultrasound Med 1998; 17:207–211.
Comment
Nonshadowing, nonmobile, defects adjacent to the wall are typical of gallbladder polyps. The differential diagnosis includes small nonshadowing stones that are adherent to the wall and tumefactive sludge.
The most common gallbladder polyp is a cholesterol polyp. They are not true neoplasms but, rather, enlarged papillary fronds filled with lipid-laden macrophages. Cholesterol polyps represent one form of cholesterolosis of the gallbladder. The more common form is the planar variety, in which there are smaller but more diffuse accumulations of triglycerides, cholesterol precursors, and cholesterol esters in the lamina propria. The planar form is also known as the strawberry gallbladder. It is difficult to appreciate the subtle wall abnormality of planar cholesterolosis on sonography.
Cholesterol polyps are usually 5 mm or less in size and are attached to the gallbladder wall by a narrow stalk. The stalk is almost never seen sonographically. However, the very pedunculated nature of the polyp is often evident and produces the “ball on the wall” sign. Cholesterol polyps can occur in any portion of the gallbladder wall. Cholesterolosis occurs in equal numbers in men and women. Its etiology is unknown, but it is not associated with elevated levels of lipid in the blood. Likewise, it does not appear to be associated with an increased incidence of cholesterol gallstones.
Provided the lesions seen on sonography are pedunculated appearing, nonmobile, and nonshadowing, there is not much of a differential diagnosis. Rarely, metastases to the gallbladder can simulate cholesterol polyps. Melanoma is the tumor with the greatest propensity to metastasize to the gallbladder. In the majority of cases, when melanoma metastasizes to the gallbladder, it is also present elsewhere in the abdomen (liver, bowel, peritoneum, etc.) and the diagnosis is not in doubt.
ANSWERS – CASE 78
Mirror Image Artifact
Reference
Middleton WD, Siegel MJ: Ultrasound artifacts. In Siegel MJ (ed): Pediatric Sonography, 3rd ed. Philadelphia, Lippincott, 2002, pp 21–39.
Comment
Acoustic mirrors can be compared to optical mirrors. With optical mirrors, a smooth, flat surface that reflects a large amount of light causes a visual duplication of structures. Surfaces that reflect more light (e.g., a silvered piece of glass) act as better mirrors than surfaces that reflect less light (e.g., a sheet of metal). Flat surfaces produce a mirror image that is identical in size and shape to the original object, but curved surfaces (e.g., mirrors at a carnival) produce a distorted mirror image.
Since gas reflects almost 100% of the sound that hits it, gas is the best acoustic mirror in the body. This is particularly true where there are large, smooth gas interfaces, such as in the lung. Therefore, mirror images are very common on sonograms that include the interface between lung and adjacent soft tissues.
The base of the right lung serves as a mirror on right upper quadrant scans and produces a number of well-recognized mirror images. Although not always appreciated, the liver is duplicated above the diaphragm, and this accounts for the supradiaphragmatic echogenicity seen on right upper quadrant scans. The diaphragm is also commonly duplicated, and this becomes apparent in areas where the diaphragm is thick enough to be resolved sonographically. Focal hepatic lesions that contrast markedly with the normal liver parenchyma (such as the echogenic mass in the first image) are also frequently duplicated above the diaphragm. The trachea is another structure with a large, smooth gas interface that can act as a mirror. On scans of the neck, the thyroid gland, neck muscles, and cartilage rings of the trachea can all be duplicated, as on the second image.
ANSWERS – CASE 79
Gallbladder Cancer
Reference
Rooholamini SA, Tehrant NS, Razavi MK, et al: Imaging of gallbladder carcinoma. Radiographics 1994;14: 291–306.
Comment
Gallbladder cancer is strongly associated with gallstones and is likely related to chronic inflammation caused by the stones. It is usually extensive at the time of diagnosis, so the prognosis is very poor. Metastases are commonly present in regional lymph nodes, and direct invasion of the liver is also common. Spread to the peritoneum and direct invasion of adjacent bowel may also occur. Because of the association with gallstones, gallbladder cancer is more common in women than in men.
The most common sonographic appearance for gallbladder cancer is a large, soft tissue mass that is centered in the gallbladder fossa. In many cases, the mass completely obliterates the gallbladder so that there is no recognizable normal gallbladder. Because of this obliteration, it can be difficult to determine the origin of the mass. In such cases, identification of engulfed gallstones (as in the second image) is very helpful because their presence makes it much more likely that the mass arose from the gallbladder.
Gallbladder cancer can also appear as diffuse or focal wall thickening. The wall thickening is usually irregular, eccentric, and solid in appearance. It is very unusual for gallbladder cancer to produce concentric, uniform thickening of the gallbladder wall.
The least common form of gallbladder cancer is a polypoid intraluminal mass (as seen in the first image). Polypoid cancers are usually much larger than benign gallbladder polyps and are attached to the wall of the gallbladder by a broad base rather than by a narrow stalk.
ANSWERS – CASE 80
High-Grade Carotid Stenosis
Reference
Grant EG, Benson CB, Moneta GL, et al: Carotid artery stenosis: Grayscale and Doppler ultrasound diagnosis—Society of Radiologists in Ultrasound Consensus Conference. Ultrasound Q 2003;19:190–198.
Comment
Velocities increase when an ICA stenosis reaches a value of approximately 50% diameter narrowing. The degree of stenosis can be estimated based on the velocity. The easiest parameter to use is the peak systolic velocity. The end diastolic velocity is also useful. Both are obtained at the site of the stenosis or in the region of the flow jet just slightly beyond the stenosis. As in this case, when the stenosis is long, the peak velocity may be isolated to a very small segment of the vessel, and it may not be obvious with color Doppler. Without careful pulsed Doppler sampling all along the course of the stenosis, the peak velocity may be missed, and the stenosis may be underestimated.
A theoretical limitation of isolated velocity parameters occurs when baseline velocities are higher or lower than normal. Low baseline velocities may occur in the setting of decreased cardiac output, or if there is a second stenosis in the more proximal vessel or in the aortic valve. In such a situation, even if the velocity at the stenosis is increased compared with the baseline values, the velocity may still underestimate the stenosis. High baseline velocities may occur in the setting of a contralateral internal or CCA occlusion when all of the flow to the head is through a single carotid artery. In such a case, the velocity may overestimate the degree of stenosis.
To account for differences in baseline velocity, one can compare the ICA velocity at the stenotic site to the velocity in a normal segment of the ipsilateral CCA. Doing this establishes the CCA velocity as a baseline for each individual patient. Unfortunately, any velocity measurement has a moderate amount of variability, and when two measurements are combined in a ratio, the variability is multiplied. In addition, the CCA velocity varies along the length of the vessel, resulting in a range of ICA-to-CCA ratios for an individual patient. Therefore, despite the theoretical advantages, there is usually little additional accuracy gained by using the ICA-to-CCA ratio.
ANSWERS – CASE 81
Comparison of Color Doppler with Power Doppler
Reference
Desser TS, Jedrzejewicz T, Haller MI: Color and power Doppler sonography: Techniques, clinical applications, and trade-offs for image optimization. Ultrasound Q 1998;14(3):128–149.
Comment
Power Doppler encodes the Doppler signal based on the power of the signal rather than on the frequency shift. This is advantageous because there is less noise contained in the power information and therefore a better signal-to-noise ratio. This allows for higher gain settings without superimposed noise. Thus, power Doppler is somewhat more sensitive to low-velocity blood flow. In addition, power Doppler is less dependent on the Doppler angle and is therefore slightly better at detecting flow when the vessel is close to perpendicular to the direction of the Doppler sound pulse.
The disadvantage of power Doppler is that it is very sensitive to tissue motion and therefore is prone to flash artifacts. In addition, power Doppler gives no directional information nor velocity information. Finally, aliasing (which is a useful artifact that identifies areas of high flow velocity) does not occur with power Doppler.
ANSWERS – CASE 82
Rectus Sheath Hematoma
Reference
Fakuda T, Sakamoto I, Kohzaki S, et al: Spontaneous rectus sheath hematomas: Clinical and radiologic features. Abdom Imaging 1996;21:58–61.
Comment
In addition to anticoagulation, rectus sheath hematomas can also be caused by blunt or penetrating trauma or severe rectus muscle contraction. The hemorrhage can be either in the muscle or within the rectus sheath, but it is usually limited to one side by the linea alba. When large, rectus sheath hematomas may dissect inferior to the arcuate line, cross the midline, extend into the prevesicle space, and compress the bladder.
The sonographic appearance of a rectus sheath hematoma depends on when it is imaged. Like other hematomas, rectus hematomas are echogenic and solid appearing in the acute phase. This is due to clotted blood in the hematoma. Over a matter of days, the clot begins to lyse, and the hematoma becomes complex, with cystic and solid components. With more time, the hematoma becomes progressively liquefactive and appears as a simple fluid collection. In some cases, a fluid level can be seen owing to a hematocrit effect.
Occasionally, it can be difficult to determine whether a lesion is in the abdominal wall or within the peritoneal cavity. One maneuver that can help is to ask the patient to take deep breaths and observe the movement of the intraperitoneal contents (bowel and fat). Usually, this localizes the depth of the parietal peritoneum and helps to determine whether the lesion is truly superficial to this level.
As with hematomas elsewhere, the differential diagnosis for rectus hematomas includes abscesses. Fortunately, these can usually be distinguished clinically or with simple aspiration. Lymphoma can occasionally infiltrate the abdominal wall and simulate a rectus hematoma. Other solid neoplasms, such as metastases and primary sarcomas, typically will be more mass like and less lenticular than rectus hematomas and are only rarely a differential consideration.
ANSWERS – CASE 83
Comparison of Phased Array and Curved Array Transducers
Comment
Modern transducers consist of multiple small crystal elements arranged in an array at the surface of the probe. By adjusting the timing of activation of the different elements, an ultrasound pulse can be created that is steered in various directions and is focused at various depths. By changing the geometry of the probe, different advantages can be obtained.
Phased array transducers have a small, flat head and create a sound pulse from a composite of multiple pulses generated by all of the elements in the array. Curved array transducers have a broad, curved head and activate only a limited number of adjacent crystal elements to create a sound pulse. Phased arrays steer the beam electronically by adjusting the timing of activation of the different elements. Curved arrays steer the beam based on the shape of the probe. Most manufacturers identify a probe based on its type, frequency, and sometimes size. In the images shown in this case, the phased array is a P4–2. The curved array is a C5–2. Phased arrays can also be identified because the sector-shaped image comes to a pointed apex, whereas the image of a curved array has a curved apex that corresponds to the shape of the probe.
ANSWERS – CASE 84
Normal Relationship of Pancreatic Tail and Spleen
Reference
Paivansalo M, Suramo I: Ultrasonography of the pancreatic tail through the spleen and through the fluid-filled stomach. Eur J Radiol 1986;6:113–115.
Comment
Visualization of the pancreatic tail is a challenge with sonography. The challenge arises from its location high and deep in the left upper quadrant. When the standard anterior approach is used, shadowing from the gas-filled stomach and from the splenic flexure of the colon frequently obscures much, if not all, of the tail. Filling the stomach with fluid can displace the colon out of the left upper quadrant and can provide a suitable window for visualization of the pancreatic tail. However, results with this technique are variable, and in some patients visualization is actually diminished.
An alternative technique is to scan from a superior left lateral approach using the spleen as a window. The tail of the pancreas extends to the splenic hilum and is usually located immediately anterior to the upper pole of the kidney. To find it, start with a coronal, transsplenic view of the left renal upper pole. The transducer should then be angled anteriorly until the kidney is no longer in view. The pancreas then appears as a band of tissue usually oriented directly at the transducer. In the splenic hilum, the splenic vein is located superior to the pancreatic tail and can thus serve as another landmark for identifying the tail. Even in situations in which the tail of the pancreas cannot be seen as a discrete structure, the transsplenic view often allows visualization of abnormalities related to the pancreatic tail, such as pseudocysts and tumors, that could not be seen from an anterior approach.
ANSWERS – CASE 85
Focal Splenic Lesions
Reference
Goerg C, Schwerk WB, Goerg K: Sonography of focal lesions in the spleen. Am J Roentgenol 1991;156: 949–953.
Comment
The sonographic appearance of these splenic lesions indicates that they are not simple cysts, but it is otherwise relatively nonspecific. In situations such as this, it is very important to survey the rest of the abdomen for clues to the correct diagnosis. In some situations, either a primary abdominal tumor or adenopathy may be seen. If the adenopathy is extensive, then lymphoma and metastatic disease are the most likely possibilities. The first patient had extensive adenopathy, and subsequent biopsies showed lymphoma. If minimal adenopathy is seen, sarcoidosis should also be considered. If a primary tumor is identified elsewhere in the abdomen, then metastatic disease almost certainly explains the splenic lesions. In addition, clinical history will usually point in one direction or the other. The second patient had a history of lung cancer, and the splenic lesions were metastases. With the proper clinical history, splenic abscesses and infarcts should also be considered. If no other abnormalities are seen sonographically and the clinical history is not helpful, then CT should be considered for further evaluation.
CASE 86
Images of the scrotum in a patient with right scrotal pain. The two power Doppler images of the right testis (bottom two images) were taken approximately 3 minutes apart.
ANSWERS – CASE 86
Testicular Torsion
References
Cannon ML, Finger MJ, Bulas DI: Case report: Manual testicular detorsion aided by color Doppler ultrasonography. J Ultrasound Med 1995;14:407–409.
Middleton WD, Middleton MA, Dierks M, et al: Sonographic prediction of viability in testicular torsion. J Ultrasound Med 1997;16:23–27.
Middleton WD, Siegel BA, Melson GL, et al: Prospective comparison of color Doppler ultrasonography and testicular scintigraphy in the evaluation of the acute scrotum. Radiology 1990;177:177–181.
Comment
Normally, the testis is anchored to the wall of the scrotum by a broad posterior attachment. This prevents the testis from significant degrees of rotation. The “bell clapper” deformity is a congenital anomaly in which this normal attachment is absent so that the testis is suspended in the scrotal sac via its vascular pedicle, like a clapper in a bell. Patients with a bell clapper deformity are at increased risk for torsion. It is believed that forceful contraction of the cremasteric muscles results in elevation and rotation of the testis and can be the precipitating event in testicular torsion.
Testicular torsion is a condition that most often affects boys in the peripubertal period or men during the young adult years. Patients with persistent torsion requiring medical attention often have had previous episodes of torsion that spontaneously detorse. Typical symptoms include pain and swelling of the scrotum. The pain may radiate into the groin and lower abdomen and is often associated with nausea and vomiting. On physical examination there is often marked tenderness, and the testis may be oriented in a high transverse lie.
With prompt diagnosis and surgical detorsion, there is a good chance that the testis can be salvaged. In fact, if treated within 6 hours of onset, the majority of testes will maintain their viability. If surgery is delayed beyond 24 hours, ischemia causes permanent necrosis of the testis in the large majority of cases. Between 6 and 24 hours after onset, the chance of testicular salvage progressively diminishes.
The diagnosis of torsion is difficult to make based on gray-scale imaging of the testis. In some patients, careful analysis of the inguinal canal will show a twisted spermatic cord. The twisted cord can also be seen as a heterogeneous mass superior to the testis called the torsion knot. It may be difficult to distinguish a torsion knot from an enlarged epididymal head due to epididymitis. In the early stages of torsion, the gray-scale appearance of the testis is normal. In fact, in the setting of torsion, it is possible to predict that the testis is still viable if it has a normal homogeneous echogenicity on gray scale. On the other hand, if the testis appears heterogeneous or hypoechoic on gray scale, then it is almost certainly nonviable. In addition to the changes in the testis, torsion is also frequently associated with a small reactive hydrocele and thickening of the scrotal skin. Unfortunately, all of the gray-scale changes seen in the testis in patients with torsion are nonspecific and can also be seen in patients with orchitis.
The sonographic diagnosis of testicular torsion depends on detecting absent or, in some cases, diminished blood flow to the affected testis with color Doppler. It is important not to mistake color noise with true intratesticular blood flow. Color noise appears as very small, randomly positioned spots of red and blue color assignment that have no pulsed Doppler signal. True vessels appear as larger, better formed areas of color assignment that can usually be elongated by various degrees of transducer rotation. In addition, true vessels should have a detectable pulsed Doppler signal. With prolonged torsion, an inflammatory reaction develops in the scrotal wall, and hyperemia can be detected in the tissues around the testis.
CASE 87
Pulsed Doppler waveforms of the left vertebral artery. Note that both waveforms are inverted, with negative frequency shifts displayed above the baseline.
ANSWERS – CASE 87
Subclavian Steal
Reference
Kliewer MA, Hertzberg BS, Kim DH, et al: Vertebral artery Doppler waveform changes indicating subclavian steal physiology. Am J Roentgenol 2000;174:815–819.
Comment
The left subclavian artery arises in the superior mediastinum and is difficult to visualize with ultrasound. Therefore, abnormalities at its origin are typically diagnosed based on secondary criteria. Since the left vertebral artery arises from the left subclavian artery, the vertebral artery can potentially provide collateral flow to the arm when the subclavian artery is stenosed or occluded at its origin. When this occurs, flow in the left vertebral artery is at least partially directed toward the subclavian artery in a retrograde direction. Since the retrograde flow is being stolen from the internal carotid arteries and the right vertebral artery by crossover at the circle of Willis and the basilar artery, this is referred to as the subclavian steal phenomenon.
In most instances, the diagnosis is readily made by noting that flow in the left vertebral artery is going down toward the arm instead of up toward the head. When the subclavian artery is totally occluded, it makes sense that there is no way to establish effective antegrade vertebral flow, so all the flow that is seen in the vertebral artery is retrograde. In actuality, elastic recoil of the upper extremity arteries may result in some backflow from the arm and into the vertebral artery. This may be detected as a short phase of minimal antegrade diastolic vertebral flow despite the presence of complete subclavian artery occlusion.
When the subclavian artery is patent but stenosed, it is possible to have significant components of antegrade flow in the vertebral artery. Since the arm is a high-resistance vascular bed, diastolic flow to the arm is ordinarily limited. Therefore, diastolic flow may proceed up the vertebral artery in an antegrade fashion, whereas systolic flow in the vertebral is reversed and supplying the arm. With less amounts of steal, antegrade systolic flow in the vertebral artery may be only partially affected. This can produce a dip in the systolic peak without resulting in actual flow reversal. Exercising the arm accentuates changes in the vertebral artery waveform and makes the diagnosis more certain.
ANSWERS – CASE 88
Morton’s Neuroma
Reference
Quinn TJ, Jacobson JA, Craig JG, van Holsbeeck MT: Sonography of Morton’s neuromas. Am J Roentgenol 2000;174:1723–1728.
Comment
Morton’s neuromas are benign masses of the plantar digital nerves of the foot. They are composed of perineural fibrosis and are likely due to repetitive trauma. The strong female predominance (80% occur in women) suggests a relationship with high-heeled shoes. The common symptoms are pain and paresthesias with walking and marked tenderness to direct palpation.
The interdigital nerves course in the space between the metatarsal heads. Under normal conditions, they are too small to be seen sonographically. Neuromas, on the other hand, can be seen with a reported sensitivity of approximately 95%. They appear as hypoechoic masses located in the interspaces of the toes, usually at or just proximal to the metatarsal heads. They may be associated with slight increased through transmission and occasionally are seen connecting to a swollen digital nerve. They occur most commonly in the third interspace and next most commonly in the second interspace. They may be multiple in approximately 25% of patients and bilateral in approximately 10% of patients.
ANSWERS – CASE 89
Partially Calcified Liver Metastases
Reference
Stoupis C, Taylor HM, Paley MR, et al: The rocky liver: Radiologic–pathologic correlation of calcified hepatic masses. Radiographics 1998;18:675–685.
Comment
Hepatic calcifications typically occur in inflammatory and neoplastic lesions. Inflammatory causes include granulomatous diseases, such as histoplasmosis and tuberculosis (small punctate calcifications without a mass) and echinococcus (peripheral curvilinear calcifications), or healed pyogenic or amebic abscesses (coarse calcification).
The most common cause of a calcified liver tumor is metastatic disease. Almost any metastatic tumor can potentially calcify, particularly during treatment. However, colorectal carcinoma is the most common primary to produce calcified liver metastases. Others that are also common are ovarian carcinoma, gastric carcinoma, and renal cell carcinoma. It is very uncommon for hemangioma, hepatocellular carcinoma, adenoma, or focal nodular hyperplasia to contain calcification. Fibrolamellar hepatocellular carcinoma more commonly contains calcification in the central scar.
On sonography, calcification is hyperechoic and is usually associated with shadowing. Gas is also hyperechoic and usually associated with shadowing. Typically, the shadow seen with gas contains medium- or low-level echoes and has fuzzy borders. This is referred to as dirty shadowing. The shadow associated with calcium contains fewer echoes and has sharper borders and is referred to as clean shadowing. Overlap exists between shadowing from calcification and from gas, and it is not always possible to distinguish between the two sonographically. When in doubt, radiographs or CT can help.
Fat attenuates sound more than normal liver parenchyma and can occasionally produce faint shadowing. This is sometimes seen in fat-containing tumors or in focal fatty infiltration.
ANSWERS – CASE 90
Renal Transplant Lymphocele
Reference
Brown ED, Chen MYM, Wolfman NT, et al: Complications of renal transplantation: Evaluation with US and radionuclide imaging. Radiographics 2000;20:607–622.
Comment
Peritransplant fluid collections are common following renal transplantation. In the immediate posttransplant period, hematomas are very common. They typically appear as complex collections adjacent to the transplant or in the abdominal wall. Lymphoceles usually occur 1 or 2 months following transplant and are present in up to 15% of patients. They occur because of disruption of the renal lymphatics. Both hematomas and lymphoceles are usually asymptomatic, although they may produce symptoms when they become large enough to compress the ureter or the renal parenchyma. The latter problem is particularly an issue with subcapsular hematomas. Urinomas are much less common and usually occur at the ureterovesicle anastomosis. They can also occur at other sites of the collecting system owing to ischemia and necrosis. Abscesses can be a primary abnormality, or they can occur due to infection of another preexisting fluid collection.
The sonographic appearances of these various fluid collections overlap so that it is usually necessary to rely on the clinical history, laboratory studies, and other imaging tests, such as radionuclide renography, to distinguish one from the other. In many instances, ultrasound guided aspiration is required to make a final diagnosis.
ANSWERS – CASE 91
Chronic Pancreatitis
Reference
Taylor AJ, Bohorfoush AG (eds): Pancreatic duct in inflammation of the pancreas. In Interpretation of ERCP with Associated Digital Imaging Correlation. Philadelphia, Lippincott-Raven, 1997, pp 231–260.
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