CASE 1

Longitudinal views of the kidneys from the same patient.

1. Do these kidneys appear normal or abnormal?

2. Which is the right kidney and which is the left?

3. What are the arrows pointing to in the kidneys?

4. What is the normal length for an adult kidney?

CASE 2

Longitudinal and transverse views of the gallbladder.

1. Should the abnormality shown on these images move when the patient rolls?

2. What causes the echogenicity of the bile in this condition?

3. Is surgery indicated?

4. What less common causes are there for this sonographic appearance?

ANSWERS – CASE 1

Normal Kidneys

1. The kidneys shown in this case are normal.

2. The first image is the right kidney and the second image is the left kidney. The only way to tell the difference is to compare the echogenicity of the adjacent liver and spleen. The normal liver is usually similar or slightly more echogenic than the right kidney. The spleen is considerably more echogenic than the left kidney.

3. The arrows are pointing to the renal pyramids.

4. The normal adult kidney is approximately 11 ± 2 cm.

ANSWERS – CASE 2

Gallbladder Sludge

1. Sludge should move to the dependent portion of the gallbladder when the patient changes position.

2. The echogenicity of sludge is due to crystals, especially cholesterol and calcium bilirubinate.

3. Sludge will usually resolve without any complications, so surgery is usually not indicated.

4. Blood and pus can simulate sludge.

Reference

Pazzi P, Gamberini S, Buldrini P, Gullini S: Biliary sludge: the sluggish gallbladder. Dig Liver Dis 2003; 35(Suppl. 3):39–45.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 34–35.

Comment

Gallbladder (GB) sludge consists of viscous bile that contains cholesterol crystals and calcium bilirubinate granules. It appears as echogenic material in the lumen of the GB. Since it is not attached to the GB wall, sludge should be mobile. However, if the bile is very thick and viscous, mobility may be very slow. Usually, sludge will layer into the dependent portion of the GB, and a straight line will form between the sludge and the rest of the bile in the GB. In some patients, sludge will completely fill the lumen of the GB. Sludge is usually homogeneous but occasionally will contain areas of heterogeneity. Blood and pus both can simulate sludge but are much less common. Unlike GB stones, sludge does not shadow. If even slight shadowing is detected within sludge, it indicates the presence of associated stones.

The pathogenesis of sludge is believed to be a combination of impaired gallbladder motility and altered nucleation factors. The most common conditions that provoke sludge formation are pregnancy, prolonged fasting, total parenteral nutrition, rapid weight loss, and critical illnesses. Some medications, including ceftriaxone, cyclosporine, and octreotide, are also associated with sludge formation.

The natural history of sludge is variable. Although good long-term studies are limited, it appears that in approximately 50% it is asymptomatic and resolves spontaneously when the precipitating cause is corrected. In 40% it is cyclic and periodically waxes and wanes. In the remainder it progresses to gallstone formation. Sludge can cause symptoms even in the absence of gallstones. It has been associated with biliary colic, acalculous cholecystitis, and pancreatitis.

CASE 3

Two longitudinal views of the lower pole of the same kidney.

1. What important finding is seen on the second image but not on the first?

2. Why doesn’t the first image show this important finding?

3. Does this lesion require further evaluation?

4. What is the major complication of this lesion?

CASE 4

Transverse and longitudinal views of the liver.

1. What structure is the large arrow pointing to in the first image?

2. What structure are the small arrows pointing to in both images?

3. What embryologic remnant travels in the structures indicated by the arrows?

4. What liver segments are indicated by the numbers 1, 2, and 3 in the first image, and what vessels are indicated by the numbers 4 and 5 in the second image?

ANSWERS – CASE 3

Angiomyolipoma

1. Both images show a hyperechoic mass. The second image shows slight posterior shadowing. These findings are typical of an angiomyolipoma (AML).

2. Because it was taken with a lower frequency transducer (4 versus 8 MHz).

3. This is controversial. Since renal cell carcinoma is occasionally similarly hyperechoic, it is not unreasonable to recommend either a noncontrast CT or MRI to prove that the lesion contains fat or follow-up sonography to prove stability.

4. The major complication of an AML is bleeding.

Reference

Siegel CL, Middleton WD, Teefey SA, McClennan BL: Angiomyolipoma and renal cell carcinoma: Ultrasound differentiation. Radiology 1996;198:789–793.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 127–128.

Comment

AML is a benign renal tumor that contains fat, smooth muscle, and vessels. These occur either sporadically or in association with tuberous sclerosis. Sporadic AMLs typically occur in middle-aged women and are solitary. AMLs in tuberous sclerosis are usually multiple, small, and bilateral and show no gender predilection.

The great majority of AMLs are asymptomatic. Large AMLs (>4 cm) may cause bleeding into the subcapsular or perinephric space. This bleeding may be related in part to the abnormal vessels and microaneurysms that are present in these tumors. Some urologists advocate removal of these large lesions.

The sonographic appearance of an AML is usually very typical. In approximately 80% of cases, an AML appears as a homogeneous hyperechoic mass similar in echogenicity to renal sinus or perinephric fat. A small percentage of AMLs are less echogenic than fat but more echogenic than renal parenchyma.

Although the usual appearance of an AML is very characteristic, it does overlap with the appearance of renal cell cancer (RCC). Approximately 10% of all RCC appears echogenic enough to simulate an AML. This is most common in small RCC. Some features can help in the differentiation of echogenic RCC and AML. If any cystic elements or a hypoechoic halo or calcification are seen, then the mass is much more likely to be RCC. On the other hand, if there is attenuation of the sound so that there is slight posterior acoustic shadowing (other than shadowing caused by calcification), then the mass is much more likely to be an AML than RCC.

ANSWERS – CASE 4

Normal Anatomy of the Liver

1. Large arrow = ligamentum teres.

2. Small arrows = fissure for ligamentum venosum.

3. Umbilical vein > ligamentum teres. Ductus venosus > fissure for ligamentum venosum.

4. 1 = Caudate segment, 2 = Left lateral segment, 3 = Left medial segment, 4 = Left hepatic vein, 5 = Branch of the left portal vein.

Reference

Wilson SR, Withers CE: The liver. In Rumack CM, Wilson SR, Charboneau JW (eds): Diagnostic Ultrasound, 3rd ed. St. Louis, Elsevier/Mosby, 2005, pp 78–82.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 49–51.

Comment

The ductus venosus is the embryologic vessel that provides communication between the umbilical vein and the inferior vena cava. It runs between the umbilical segment of the left portal vein and the most superior aspect of the inferior vena cava. It is embedded in the liver via a deep fissure that can be seen on both longitudinal and transverse images of the left lobe of the liver. This fissure separates the caudate lobe from the lateral segment of the left lobe. Whenever the fissure for the ligamentum venosum is seen, the portion of the liver seen anteriorly must be the lateral segment of the left lobe. Therefore, in the longitudinal view, the portal vein branch and hepatic vein branch that are seen must be branches of the left portal vein and hepatic vein that supply the lateral segment.

The ligamentum teres is the remnant of the umbilical vein. On transverse views such as those shown in this case, it appears as a round, echogenic structure that often produces some posterior shadowing. It attaches to the most anterior aspect of the left portal vein. In the fetus, blood flow from the umbilical vein travels into the liver, through a short segment of the left portal vein, and then into the ductus venosus. The segment of the left portal vein that connects the umbilical vein to the ductus venosus is called the umbilical segment of the left portal vein. The ligamentum teres and the umbilical segment of the left portal vein both separate the medial and lateral segments of the left lobe.

CASE 5

Longitudinal and transverse views of the porta hepatis.

1. Name the numbered normal structures on the longitudinal view.

2. Name the numbered normal structures on the transverse view.

3. Are measurements of the common duct obtained from the inner wall or the outer wall?

4. What segment of the bile duct is usually the largest?

CASE 6

Longitudinal view of the right posterior hemithorax and transverse view of the right upper quadrant obtained in different patients.

1. What is the diagnosis in these two patients?

2. To what is the large arrow pointing?

3. To what are the small arrows pointing?

4. When the abdomen is scanned, is this abnormality easier to detect on the right side or on the left side?

ANSWERS – CASE 5

Normal Anatomy of the Common Bile Duct

1. 1 = Common hepatic duct, 2 = Right hepatic artery, 3 = Portal vein, 4 = Inferior vena cava, 5 = Right renal artery, 6 = Crus of the right diaphragm, 7 = Cystic duct insertion.

2. 1 = Portal vein, 2 = Proper hepatic artery, 3 = Common hepatic duct.

3. Bile duct diameter is measured from inner wall to inner wall. This is done to allow for better correlation with measurements taken during cholangiography.

4. The bile duct diameter is usually greatest in its mid segment (i.e., between the porta hepatis and the pancreatic head).

Reference

Middleton WD: The bile ducts. In Goldberg BB (ed): Diagnostic Ultrasound. Baltimore, Williams & Wilkins, 1993, pp 146–172.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 87–90.

Comment

The left and right hepatic ducts join each other to form the common hepatic duct. The common hepatic duct joins the cystic duct to form the common bile duct. Although it is visualized in this case, the insertion of the cystic duct is usually difficult to visualize. Therefore, it is usually not possible to precisely determine where the junction of the common hepatic duct and the common bile duct is located. For this reason, many ultrasonologists refer to the common hepatic duct and the common bile duct together as the “common duct.”

In most views of the porta hepatis, it is easy to identify the portal vein and to identify tubular structures anterior to the portal vein that represent the hepatic artery and the common duct. The common hepatic artery arises from the celiac axis. Following the takeoff of the gastroduodenal artery, it ascends into the porta hepatis as the proper hepatic artery. Therefore, the proper hepatic artery is usually what is visualized in the porta hepatis.

As shown in the transverse view, the proper hepatic artery is usually more to the left and the common duct to the right. This is easy to remember since the artery arises from the aorta (a left-sided structure) and the bile duct arises from the liver (a right-sided structure). After the proper hepatic artery bifurcates into the right and left hepatic arteries, the right hepatic artery crosses between the portal vein and the common duct. This produces the classic view showing the bile duct in long axis, the right hepatic artery in short axis, and the portal vein in an oblique axis, as shown in the longitudinal image.

ANSWERS – CASE 6

Pleural Effusion

1. Both patients have pleural effusions.

2. The large arrow is pointing to atelectatic lung floating in the pleural fluid.

3. The small arrows are pointing to aerated lung and the associated posterior shadow.

4. Pleural effusions are easier to see on the right side because the liver provides a better window to the costophrenic angle than does the spleen.

Reference

Brant WE: The thorax. In Rumack CM, Wilson SR, Charboneau JW (eds): Diagnostic Ultrasound, 3rd ed. St. Louis, Elsevier/Mosby, 2005, pp 603–609.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 269–271.

Comment

Pleural effusions are frequently seen as incidental findings on abdominal scans. Normally, the aerated lung is closely applied to the diaphragm so that sound cannot penetrate to the posterior structures of the chest. Pleural effusions displace aerated lung enough to provide a window to the posterior surface of the costophrenic sulcus. When the effusion is small, this produces a triangular-shaped collection. When the effusion is larger, there is usually associated compressive atelectasis of the lung, producing a mobile, curvilinear soft tissue structure floating within the fluid. Aerated lung, appearing as hyperechoic tissue with dirty posterior shadowing, is often seen above the atelectatic lung. On longitudinal views, pleural effusions are distinguished from perihepatic ascites by noting the triangular costophrenic sulcus. On transverse views, the bare area of the liver prohibits ascites from extending to the posterior medial aspect of the liver. Pleural effusions typically do extend to the most medial aspect of the liver, near the vena cava.

As shown on the first image, pleural effusions can also be seen by scanning directly over the chest wall in the region of the effusion. This scanning is commonly done when performing ultrasound-guided thoracentesis. The fluid is seen separating the parietal and visceral layers of the pleura. In the longitudinal plane, the ribs are seen as shadowing echogenic structures and the parietal pleura as a smooth, linear reflection deep to the ribs. Pleural effusions that appear simple on sonography may be either transudative or exudative. Complex effusions that contain septations and/or internal floating reflectors are usually exudative.

CASE 7

Two transverse and two longitudinal views of the scrotum.

1. What is the normal echogenic structure (arrow) shown on the first transverse view and the first longitudinal view?

2. What are the normal peritesticular structures labeled 1 and 2 on the second transverse view and the second longitudinal view?

3. What is the normal relative echogenicity of the testis and of the head of the epididymis?

4. What is the normal relative echogenicity of the testis and of the body of the epididymis?

ANSWERS – CASE 7

Normal Scrotal Anatomy

1. The peripheral echogenic structure is the mediastinum of the testis.

2. 1 = Head of the epididymis, 2 = Body of the epididymis.

3. The head of the epididymis is normally isoechoic to the testis.

4. The body of the epididymis is normally hypoechoic to the testis.

Reference

Feld R, Middleton WD: Recent advances in sonography of the testis and scrotum. Radiol Clin North Am 1992; 30:1033–1051.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 152–153.

Comment

The testes are paired ovoid organs residing within the two halves of the scrotum. Six scrotal layers (the skin, dartos, external spermatic fascia, cremasteric muscle, internal spermatic fascia, and the tunica vaginalis) surround them and the testicular capsule called the tunica albuginea. The two scrotal sacs are divided by a midline median raphe.

Each testis is divided into approximately 300 lobules. Each lobule contains up to four extremely convoluted seminiferous tubules. As they converge to exit the testis, the seminiferous tubules join together to form the straight tubules. The straight tubules then join to form a plexus of channels called the rete testis that is located within an infolding of the tunica albuginea called the mediastinum. The mediastinum is the hilum of the testis. The rete testes empty into the head of the epididymis via 10 to 15 efferent ductules. In the head of the epididymis, the efferent ductules join together to form a single convoluted ductus epididymis. The epididymis is a crescent-shaped structure that rests on the surface of the testis near the mediastinum. It is divided into the head superiorly, the tail inferiorly, and the body in between.

The normal testis has a low- to medium-level echogenicity and a homogeneous echotexture. It measures approximately 4 cm in length and 2 cm in width and thickness. The mediastinum is an elongated, echogenic structure at the periphery of the testis that runs from the upper third to the lower third of the testis. In some testes it is very prominent, and in others it is not visible at all. The epididymal head rests on the upper pole of the testis and has an echogenicity similar to that of the testis. Often, a faint posterior refractive shadow arises from the interface between the testis and the epididymal head. This is present on the second longitudinal image. During real-time scanning, the epididymal head can usually be followed into the body of the epididymis, which is slightly less echogenic than the testis. The location of the epididymal body is variable because the testis is somewhat mobile within the scrotal sac. Most often, the epididymal body is seen along the anterior and lateral aspect of the testis, as shown on the second transverse image. In some patients, the epididymal body is located posterior to the testis, as shown on the second longitudinal image.

The tail of the epididymis connects to the vas deferens. The inferior aspect of the vas deferens is very tortuous and can be visualized in some individuals. As the vas ascends in the spermatic cord, it straightens and becomes easier to identify. It is typically a thick-walled structure (total diameter approximately 2 mm) with a tiny lumen. Unlike the other structures in the spermatic cord, the vas is avascular and does not compress.

A small amount of fluid is often seen in the scrotal sac, usually around the epididymal head. Occasionally, the appendix of the testis and/or epididymis can be seen when they are surrounded by fluid. They typically appear as tiny ovoid structures attached to the testis or epididymis.

CASE 8

Transverse and sagittal views of the upper abdomen.

1. Name the normal numbered structures on the transverse scan.

2. Name the normal numbered structures on the sagittal scan.

3. Is the pancreatic body normally round or oval-shaped on sagittal scans?

4. Is the superior mesenteric artery or the superior mesenteric vein closer to the pancreas?

CASE 9

Longitudinal views of different patients with the same abnormality.

1. What is wrong with these kidneys?

2. In what circumstances is this condition a medical emergency?

3. How would you grade the abnormality shown here?

4. In what plane are these images acquired?

ANSWERS – CASE 8

Normal Peripancreatic Anatomy

1. 1 = Left lobe liver, 2 = Pancreas, 3 = Portosplenic confluence, 4 = Aorta, 5 = Inferior vena cava (IVC), 6 = Superior mesenteric artery (SMA), 7 = Common bile duct (CBD), 8 = Gastroduodenal artery.

2. 1 = Left lobe liver, 2 = Pancreas, 3 = Splenic vein, 4 = Aorta, 5 = Celiac axis, 6 = SMA, 7 = Left renal vein, 8 = Gastric antrum.

3. The pancreatic body is oval on sagittal scans.

4. The superior mesenteric vein is immediately adjacent to the head and uncinate process of the pancreas. The SMA is separated from the pancreas by a ring of echogenic fibrofatty tissue.

Reference

Schneck CD, Dabezies MA, Friedman AC: Embryology, histology, gross anatomy, and normal imaging anatomy of the pancreas. In Friedman AC, Dachman AH (eds): Radiology of the Liver, Biliary Tract, and Pancreas. St. Louis, Mosby, 1994, pp 715–742.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 191–194.

Comment

The pancreas is one of the more difficult organs to visualize with ultrasound. Knowledge of the peripancreatic vessels aids greatly in localizing the gland. The most useful landmark is the portosplenic venous confluence. On transverse scans, this appears as a tadpole-shaped hypoechoic to anechoic structure posterior to the body of the pancreas. The head of the pancreas wraps around the right lateral aspect of the portal vein at the level of the portomesenteric confluence, and the uncinate process extends posterior to the superior mesenteric vein. All of the peripancreatic veins are immediately adjacent to the pancreas without any intervening fatty tissue. On the other hand, the peripancreatic arteries are surrounded by echogenic fibrofatty tissue and do not make direct contact with the pancreas. The celiac axis typically arises at the superior aspect of the pancreas. The body of the pancreas can be seen by scanning just below the origin of the common hepatic artery and splenic artery. The SMA arises from the aorta immediately posterior to the pancreas and the portosplenic confluence. A characteristic hyperechoic ring of fibrofatty tissue surrounds the SMA.

The CBD travels in the most posterior aspect of the pancreas. In fact, it often appears immediately anterior to the IVC. The gastroduodenal artery arises from the common hepatic artery and descends along the anterior aspect of the head of the pancreas. These two structures often appear as two small anechoic dots on transverse views of the pancreatic head.

ANSWERS – CASE 9

Hydronephrosis

1. The renal collecting system is dilated.

2. If the kidney is infected and obstructed.

3. This is referred to as grade 2 hydronephrosis.

4. Coronal or semicoronal.

Reference

Ellenbogen PH, Scheible FW, Talner LB, Leopold GR: Sensitivity of gray scale ultrasound in detecting urinary tract obstruction. Am J Roentgenol 1978; 130:731–733.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 106–110.

Comment

Sonographic detection of urinary obstruction depends on identification of a dilated collecting system, which appears as anechoic spaces within the echogenic central renal sinus. In most circumstances, it is easy to document that the cystic spaces communicate with each other and with the renal pelvis. This confirms that the fluid is in the collecting system.

Hydronephrosis is graded into different levels of severity. Grade 0 refers to a normal sonogram. Grade 1 refers to minimal separation of the central echogenic renal sinus. Grade 2 refers to obvious distention of the renal collecting system. Grade 3 refers to marked distention of the renal collecting system with associated cortical thinning.

Whenever hydronephrosis is detected, the next task is to determine the level and cause of obstruction. When the hydronephrosis is bilateral, the obstruction is often at the level of the bladder, and this is usually easy to document sonographically. Prostatic hypertrophy is easy to identify in men, and pelvic tumors are usually easy to identify in women. Primary bladder tumors are often easily identified in both genders. Unilateral obstruction of the ureter at a level above the bladder is more difficult to sort out with ultrasound. Depending on the patient, it may be possible to follow the ureter over its entire course and document the transition point and the cause of obstruction. However, the mid ureter is often not visible, and unless the obstruction is caused by a sizable mass or stone, the source of mid-ureteral obstruction may not be visible sonographically. In such cases, sonography should be followed by further imaging tests, such as noncontrast CT (if a stone is likely) or CT urography (if a mass is likely).

CASE 10

Transverse views of the liver.

1. What is the echogenic structure indicated by the long arrow?

2. What is the linear structure indicated by the short arrow?

3. What is the fluid-filled structure indicated by the number 1?

4. What liver segments are indicated by the numbers 2, 3, and 4?

CASE 11

Longitudinal views of the patellar tendon.

1. Which view shows a normal patellar tendon?

2. What is the differential diagnosis for a hypoechoic tendon?

3. Are nerves more or less echogenic than tendons?

4. Does ultrasound demonstrate the internal fibers of tendons as well as MRI?

ANSWERS – CASE 10

Normal Liver and Gallbladder Anatomy

1. The long arrow is pointing at the ligamentum teres.

2. The short arrow is pointing at the interlobar fissure.

3. The number 1 is identifying the gallbladder.

4. Numbers 2, 3, and 4 are in the left lateral, left medial, and right anterior segments, respectively.

Reference

Middleton WD: The gallbladder. In Goldberg BB (ed): Diagnostic Ultrasound. Baltimore, Williams & Wilkins, 1993, pp 116–142.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 28–29.

Comment

The normal gallbladder (GB) is located along the inferior and posterior aspect of the liver. It rests between the right and left lobes and serves as a valuable landmark to help separate the right and left lobes. In most fasting patients, the GB is readily identified simply by moving the transducer along the right inferior costal margin while visualizing the lower margin of the liver. In cases in which the GB is difficult to find, it is helpful to use hepatic landmarks. Start by finding the ligamentum teres between the medial and lateral segments of the left lobe. It typically appears as a round, echogenic structure, often with some posterior shadowing. Then look to the right for the interlobar fissure. This fissure is a shallow indentation on the posterior–inferior aspect of the liver that appears as an echogenic line extending from the porta hepatis into the liver parenchyma. The interlobar fissure separates the left lobe (medial segment) and right lobe (anterior segment). The GB is located immediately adjacent to the interlobar fissure. In some patients, the interlobar fissure is not visible sonographically. This most often occurs when the GB is well distended. Fortunately, the interlobar fissure is usually easiest to see in those situations in which the GB is contracted and more difficult to see.

The GB is usually well distended in a patient after an overnight fast. The upper limit of normal for GB size, even in a fasting patient, is 4 cm in the transverse plane. The transverse diameter is a better indicator of overdistention than the longitudinal diameter. Nevertheless, most GBs will be less than 10 cm in length. The GB wall thickness should not exceed 3 mm. When the GB is contracted, the wall may seem thick and the muscle layer may become apparent as a hypoechoic layer deep to the mucosa. However, even in the contracted state, it is unusual for the wall to measure more than 3 mm.

ANSWERS – CASE 11

Normal Tendon Anisotropy

1. The patellar tendon is normal in both views. In fact, it is the same tendon imaged once with the long axis parallel to the transducer and again with the long axis at an angle to the transducer.

2. Decreased echogenicity in a tendon may indicate tendinitis or a partial tear, or it may be due to anisotropy.

3. When imaged at 90 degrees, tendons are more echogenic than nerves.

4. Ultrasound displays the internal fibers of tendons better than MRI.

Reference

Martinoli C, Bianchi S, Derchi LE: Tendon and nerve sonography. Radiol Clin North Am 1999;37:691–711.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 278–279.

Comment

Sonography displays the internal architecture of tendons better than any other modality. When imaged so that the sound reflects off the tendon at 90 degrees, the interfaces between tendon collagen and internal endotendineum septa produce strong specular reflections. This results in an appearance of bright, closely spaced, parallel, linear reflections within the substance of the tendon. When tendons are imaged at less than 90 degrees, the internal reflectors no longer act as specular reflectors, and the tendon becomes hypoechoic and the internal fibrillar pattern is no longer seen. This effect (variable echogenicity depending on the relative orientation of the transducer and the tendon) is referred to as anisotropy. Anisotropy is present in many parts of the body but is particularly prominent in tendons.

In most circumstances, tendons should be imaged at 90 degrees so that the internal fibrillar pattern is visible. However, when tendons are surrounded by echogenic tissue such as fat, it may be helpful to purposely angle the transducer so that the tendon appears hypoechoic and the contrast between tendon and peritendinous tissues is increased. In addition, echogenic lesions and abnormal intratendinous interfaces are occasionally best seen when the tendon is purposely made to appear hypoechoic by imaging at less than 90 degrees.

CASE 12

Longitudinal and transverse views of the shoulder.

1. Identify the numbered normal structures in the two figures.

2. The rotator cuff is composed of how many tendons?

3. What structure separates the subscapularis from the supraspinatus?

4. Is the normal rotator cuff compressible?

CASE 13

Longitudinal images of the gallbladder in different patients.

1. Do these patients have anything in common?

2. What is the differential diagnosis?

3. What do you think is the cause of the abnormality in these two patients?

4. Are any measurements useful in detecting this abnormality?

ANSWERS – CASE 12

Normal Anatomy of the Shoulder

1. 1 = Rotator cuff (RC), 2 = Cartilage, 3 = Humeral head, 4 = Anatomic neck, 5 = Greater tuberosity, 6 = Subdeltoid bursa, 7 = Deltoid, 8 = Biceps tendon.

2. The rotator cuff is composed of four tendons and muscles—the subscapularis, the supraspinatus, the infraspinatus, and the teres minor.

3. The intra-articular portion of the biceps tendon separates the subscapularis and the supraspinatus.

4. The normal rotator cuff is not compressible.

Reference

Middleton WD, Teefey SA, Yamaguchi K: Sonography of the shoulder. Semin Musculoskeletal Radiol 1998; 2:211–221.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 280–283.

Comment

The RC is a band of conjoined tendons that covers the humeral head. The anterior tendon (subscapularis) crosses the glenohumeral joint and attaches to the lesser tuberosity. The superior tendon (supraspinatus) attaches to the greater tuberosity just posterior to the biceps tendon groove. The intra-articular portion of the long head of the biceps tendon separates these two tendons. Anatomic studies have shown that the supraspinatus tendon measures approximately 1.5 cm in width. Behind and inferior to the supraspinatus tendon is the infraspinatus tendon, which also inserts on the greater tuberosity. A minor tendon located just inferior to the infraspinatus is the teres minor.

Sonograms of the shoulder display multiple structures in a series of layers. The deepest structure is the humeral head, which appears as a strong, curvilinear reflection. On longitudinal views, the concave anatomic neck separates the humeral head and the greater tuberosity. Immediately on top of the humeral head is a thin layer of anechoic or hypoechoic articular cartilage. The next layer is the RC, which appears as a thick (4–6 mm) band of tissue. In most patients, the RC appears hyperechoic compared to the overlying deltoid muscle. In elderly patients, the RC and the deltoid may appear more similar in echogenicity. Superficial to the RC is a thin, hypoechoic layer that represents the subdeltoid bursa. Superficial to this is a thin, hyperechoic layer that represents peribursal fat. The deltoid muscle is the final layer. Like other muscles, it is hypoechoic.

The outer surface of the normal RC is convex. Conversion to a concave contour is an important sign of a full-thickness RC tear. In addition, the normal RC is not compressible. The ability to compress the RC is another sign of a full-thickness tear.

ANSWERS – CASE 13

Gallbladder Wall Thickening

1. Both patients have thick gallbladder (GB) walls. The first image also shows ascites and a nodular liver consistent with cirrhosis. The second image also shows a completely contracted GB lumen.

2. The causes of a thick GB wall include heart failure, hypoproteinemia, edema-forming states, hepatitis, cirrhosis, portal hypertension, lymphatic obstruction, GB cancer, adenomyomatosis, and cholecystitis.

3. The nodularity of the liver surface in the first image is consistent with cirrhosis, and this is the cause of the GB wall thickening. The lumen of the GB is completely contracted in the second image, and this finding should raise the possibility of hepatitis.

4. The upper limit of normal for GB wall thickness is 3 mm.

Reference

Middleton WD: The gallbladder. In Goldberg BB (ed): Diagnostic Ultrasound. Baltimore, Williams & Wilkins, 1993, pp 116–142.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 43–45.

Comment

A large number of processes can cause thickening of the GB wall. Most of the etiologies are not related to intrinsic GB disease. These nonbiliary causes produce thickening of the GB wall as a result of edema. In general, the most pronounced GB wall thickening is usually due to one of these nonbiliary causes. Acute hepatitis in particular can cause extensive GB wall thickening. Hepatitis may also result in contraction of the GB lumen to the point that the lumen is completely collapsed. As shown in the second image, a collapsed lumen is seen as a linear reflection from the apposed walls of the lumen.

In most cases, marked GB thickening is manifested by irregular or striated intramural sonolucencies, as is seen in these images. When this pattern is noted, it usually means that the thickening is not related to cholecystitis. However, if this pattern is identified in a patient with well-established clinical and sonographic evidence of cholecystitis, then it usually indicates more advanced disease.

CASE 14

Transverse view of the liver in different patients.

1. What are the vascular structures indicated by the numbers 1, 2, and 3?

2. What segments of the liver, indicated by the numbers 4, 5, 6, and 7, do these vessels separate?

3. How can you distinguish the hepatic veins and portal veins on a static gray-scale view of the liver?

4. To what vein does the caudate lobe drain?

CASE 15

Two transverse views of the thyroid.

1. What do the arrowheads at the left side of the images indicate?

2. Which image would you expect to have the higher frame rate?

3. What can you do to improve the frame rate while performing real-time scans?

4. What can you do to improve the resolution while performing real-time scans?

ANSWERS – CASE 14

Normal Hepatic Venous Anatomy

1. The three vessels are the hepatic veins. 1 = Right, 2 = Middle, 3 = Left.

2. The right hepatic vein separates the anterior (5) and posterior (4) segments of the right lobe. The middle hepatic vein separates the anterior segment of the right and the medial segment (6) of the left lobe. The left hepatic vein separates the left lateral (7) and the left medial segments.

3. Unlike the portal veins, the hepatic veins are not surrounded by fibrofatty tissues and therefore have much less echogenic walls. In fact, in most circumstances, the wall of the hepatic vein is not visible sonographically. The exception is when the hepatic vein is viewed with the walls perpendicular to the direction of the sound. In this situation, the wall produces a specular reflection and appears as a thin, echogenic line. This is well demonstrated in the right hepatic vein on the first image.

4. The caudate lobe drains into the vena cava via small veins that are separate from the three main hepatic veins. The caudate veins can function as collaterals in patients with Budd–Chiari syndrome.

Reference

Schneck CD: Embryology, histology, gross anatomy and normal imaging anatomy of the liver. In Friedman AC, Dachman AH (eds): Radiology of the Liver, Biliary Tract, and Pancreas. St. Louis, Mosby, 1994, pp 1–25.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 49–52.

Comment

Three major veins drain hepatic blood flow into the vena cava. The main hepatic veins travel between the segments of the liver and therefore are used as landmarks for identifying the segments. The middle and left hepatic veins usually join together before emptying into the inferior vena cava. In most patients, the right hepatic vein is best imaged from an intercostal approach near the midaxillary line. This not only allows for visualization on gray scale but also provides a good angle for Doppler imaging. The left hepatic vein is best imaged from a midline subxiphoid approach. The middle hepatic vein is best seen from an approach somewhere between the right and left vein.

In addition to the three main hepatic veins, a variable number of smaller dorsal hepatic veins may drain directly into the vena cava from the posterior right lobe and the caudate lobe. These dorsal veins often act as collaterals when the three main veins are obstructed.

ANSWERS – CASE 15

Frame Rate and Resolution

1. The arrowheads indicate the levels at which the image is focused.

2. The second image because the field of view is smaller, and there is only one focal zone.

3. Frame rate can be improved by decreasing the number of focal zones, decreasing the image depth, decreasing sector width, decreasing line density, and turning off Doppler modes.

4. Resolution can be improved by using a higher frequency transducer, increasing the number of focal zones, and increasing line density.

Reference

Kremkau FW: Multiple element transducers. Radiographics 1993;13:1163–1176.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, p 12.

Comment

Each ultrasound image is composed of multiple scan lines. The time required to create one frame of a real-time image is calculated by multiplying the speed of sound times the length of the scan lines times the number of lines per image times 2. Multiplying by 2 is necessary because the sound has to make a round trip from the transducer to the target and back. The longer it takes to generate one frame, the lower the frame rate. Typical frame rates range from 5 to 40 frames per second. Increased frame rates can be obtained by decreasing the length of each scan line (less image depth) or decreasing the number of scan lines (less image width, narrower sector angles, and lower line density).

In many respects, frame rate and image resolution are competing parameters. As shown in this case, each scan line can be electronically focused at a certain depth. To focus at multiple depths requires multiple pulses for each scan line. In the first image shown in this case, pulses focused in the near field created the superficial aspect of the image, which was pasted to two different images obtained separately with mid- and far-field focusing. Therefore, the improved resolution throughout the field of view that comes with multiple focal zones results in a sacrifice in frame rate. It is also possible to improve resolution by moving the scan lines closer together. This is called increasing line density, and it also has an inverse relationship to frame rate.

CASE 16

Transverse and longitudinal views of the thyroid.

1. Name the normal numbered structures on the transverse scan of the right side of the neck.

2. Name the normal numbered structures on the longitudinal scan of the neck.

3. How can the carotid artery be distinguished from the jugular vein on gray-scale scans of the neck?

4. Can the normal parathyroid glands be seen on ultrasonography?

CASE 17

Transverse views of the prostate from a transrectal approach. The second image was obtained slightly superior to the first.

1. What zones of the prostate are indicated by the numbers 1 and 2?

2. What structures are shown in the second image?

3. What zone is the largest, and how does this vary with age?

4. What is the normal value for prostate-specific antigen (PSA)?

ANSWERS – CASE 16

Normal Anatomy of the Thyroid

1. 1 = Right thyroid lobe, 2 = Thyroid isthmus, 3 = Carotid, 4 = Jugular, 5 = Trachea shadow, 6 = Strap muscles, 7 = Sternocleidomastoid muscle, 8 = Longus coli muscle.

2. 1 = Thyroid, 2 = Strap muscles, 3 = Sternocleidomastoid muscle, 4 = Cartilage rings of trachea.

3. The carotid artery is circular, the jugular vein is oval. The carotid is more medial and deep, the jugular is more lateral and superficial. The carotid is noncompressible, the jugular is easily compressible. The diameter of the carotid is constant, the diameter of the jugular varies.

4. The normal parathyroids are too small to be seen on sonography.

Reference

Solbiati L, Livraghi T, Ballarati E, et al: The thyroid. In Solbiati L, Rizzatto G (eds): Ultrasound of Superficial Structures. Edinburgh, Churchill Livingstone, 1995, pp 49–86.

Cross-Reference

Ultrasound: THE REQUISITES, 2nd ed, pp 244–245.

Comment

The normal thyroid gland consists of a left and a right lobe connected by a thin isthmus. It is located in the inferior aspect of the neck on both sides of the trachea. A minority of patients have a thin pyramidal lobe that extends superiorly from the isthmus and can be seen in childhood. In adults, the normal thyroid is 4 to 6 cm long and 13 to 18 mm in anteroposterior diameter. It has a homogeneous medium-level echogenicity. Normally, the thyroid is more echogenic than the overlying strap muscles and the sternocleidomastoid muscles.

The parathyroid glands typically measure 4 × 3 × 1 mm in size, with the long axis oriented in a craniocaudal direction. The two superior glands are usually located behind the mid aspect of the thyroid, and the two inferior glands are located behind or just inferior to the lower pole of the thyroid. Approximately 20% of inferior parathyroid glands are located within 4 cm of the lower pole of the thyroid. A fifth gland, usually associated within the thymus, is present in approximately 13% of patients.

ANSWERS – CASE 17

Normal Prostate

1. Number 1 indicates the peripheral zone. Number 2 indicates the central gland, which includes the central zone and the transitional zone.

2. The second image is taken slightly superior to the first and shows the paired seminal vesicles.

3. In young men the peripheral zone is the largest. Because of the effects of benign prostatic hypertrophy, the central gland is the largest in older men.

4. The normal PSA is less than 4 ng/mL.

Reference

Kaye KW, Richter L: Ultrasonographic anatomy of the normal prostate gland: Reconstruction by computer graphics. Urology 1990;35:12–17.

Cross-Reference

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