Ultrasound Flashcards
Cholelithiasis
Cholelithiasis is the presence of a gallbladder stone or stones, without associated inflammation.
The classic clinical presentation of symptomatic cholelithiasis is colicky pain after eating a fatty meal, but it is common to see gallstones incidentally in asymptomatic patients.
Risk factors for developing gallstones include female sex, obesity, pregnancy, middle age, and diabetes.
The ultrasound diagnosis of gallstones is usually straightforward. Stones are echogenic with posterior acoustic shadowing are are often mobile. It is often helpful to reposition the patient (typically in the left lateral decubitus position) while scanning to assess whether the stones layer dependently to differentiate stones from polyps or other masses.
A gallbladder completely filled with stones can be more challenging to identify. The wall-echo-shadow (WES) signn describes the appearance of a gallbladder full of multiple stones (or one giant stone).
Two parallel echogenic arcs represent the gallbladder wall and leading edge of the stone, with an intervening thin layer of hypoechoic bile. The gallstone typically casts a prominent shadow.
The differential diagnosis of echogenic material within the gallbladder includes:
Gallstones (mobile shadowing)
Gallbladder sludge (mobile, non-shadowing)
Gallbladder polyp (non-mobile, non-shadowing, often attached to the gallbladder wall via a stalk, may be vascular).
Hyperplastic cholecytoses (non-mobile, multiple polyps).
Acute calculous cholecystitis
Acute cholecystitis is inflammation of the gallbladder, usually due to a gallstone impacting the cystic duct. Ultrasound is the first-line evaluation of suspected acute cholecystitis.
Acute cholecystitsi clinicaly presents with right upper quadrant (RUQ) pain and fever.
There is no 100% specific ultrasound finding for acute cholecystitis. However, gallstones are seen >90% of the time and a postivie sonographic Murphy’s sign (RUQ pain with pressure from the transducer) also has a high positive predictive value. Other findings include: Gallbladder wall thickening >3 mm. Distended gallbladder >4 cm in diameter. Pericholecystic fluid. Color Doppler showing hyperemic gallbladder wall. Hyperechoic fat in the gallbladder fossa (ultrasound correlate to CT finding of fat stranding).
Complications of acute cholecystitis are rare but serious. Emphysematous cholecystitis is gas in the gallbladder wall and has a high risk of gallbladder perforation. Gangrenous cholecystitis is necrosis of the gallbladder wall. Sonographic findings include layering echogenic material in the gallbladder lumen representing hemorrhage and sloughed membranes. Gallbladder perforation appears as focal discontinuity of the gallbladder wall. Perihepatic ascites containing dirty echoes is often present.
Surgical treatment of uncomplicated acute calculous cholecystitis is cholecystectomy. In patients who are not good surgical candidates, a temporizing percutaneous cholecystostomy tube can be placed prior to definitive surgical cholecystectomy.
Acalculous cholecystitis
Acalculous cholecystitis is cholecystitis without gallstones, typically seen in very sick patients. Risk factors include sepsis, prolonged total parenteral nutrtion, and trauma.
The ultrasound appearance is similar to acute cholecystitis but without stones. Since many patients are ventilated or obtunded, it’s often not possible to evaluate for sonographic Murphy’s sign.
Treatment of acalculous cholecystitis is typically interventional radiology percutaneous cholecystostomy. Unlike the treatment of calculous cholecystitis, cholecystostomy is often the definitive therapy.
Emphysematous cholecystitis
Emphysematous cholecystitis is a rapidly progressive form of acute cholecystitis characterized by gas in the gallbladder wall. Emphysematous cholecystitis is associated with gallbladder ischemia causing bacterial translocation. Treatment is urgent surgery.
On ultrasound, gas is usually present in both the gallbladder lumen and wall, which appears as echogenic lines and foci with posterior dirty shadowing.
Porcelain gallbladder
A porcelain gallbladder is a calcified gallbladder wall due to either chronic irritation from supersaturated bile or repeated bouts of gallbladder obstruction.
Porcelain gallbladder is associated with an increased risk of gallbladder cancer, but the incidence is controversial. In general, prophylactic choleycystectomy is the standard of care.
On ultrasound, the wall of the gallbladder is echogenic, and there are almost always associated gallstones.
The differential diagnosis of an echogenic gallbladder wall includes a porcelain gallbladder, a gallbladder packed full of stones (which will feature the wall-echo-shadow sign), or emphysematous choleycystitis (intramural gas will have dirty shadowing).
Courvoisier gallbladder
The Courvoisier gallbladder refers to a markedly dilated gallbladder (originally described as being so large as to be directly palpable) from malignant obstruction of the common bile duct.
A markedly distended gallbladder implies chronic obstruction of either the cystic duct (when seen in isolation) or the common bile duct (when seen in combination with dilation of the common bile duct and intrahepatic biliary dilation).
Overview of hyperplastic cholecytoses
The hyperplastic cholecytoses are a spectrum of non-neoplastic proliferative disorders caused by deposition of cholesterol-laden macrophages within the wall of the gallbladder. The cholecystoses range from abnormalities of the gallbladdr wall (adenomyomatosis and strawberry gallbladder) to gallbladder polyps extending into the lumen.
Adenomyomatosis
Adenomyomatosis is cholesterol deposition in mural Rokitansky-Aschoff sinuses. It is important not to confuse with adenomyosis of the uterus: It may be helpful to remember that there are three L’s in gallbladder, and adenomyomatosis is a longer word than adenomyosis.
The ultrasound hallmark of adenomyomatosis is the comet-tail artifact due to reflections off of tiny crystals seen in a focally thickened and echogenic gallbladder wall.
Strawberry gallbladder (cholesterolosis of the gallbladder)
Strawberry gallbladder is a pathologic diagnosis that is not apparent by imaging. It is characterized by tiny mural cholesterol depsosits likened to strawberry seeds.
Gallbladder polyps
Most gallbladder polyps are benign cholesterol polyps that are part of the hyperplastic cholecytosis spectrum. Rarely (<5%), polyps may be premalignant adenomas.
Clinically, gallbladder polyps may cause right upper quadrant pain or even cholecystitis if the cystic duct is obstructed.
The following characteristics, known as the six S’s, increase the risk for a polyp being malignant: Size >10 mm or rapid growth. As a caveat, ultrasound has limited sensitivity and specificity in detecting small polyps (<10 mm), especially in the presence of gallstones. Single: A solitary polyp is more suspicious for malignancy. In contrast, benign cholesterol polyps tend to be multiple. Sessile (broad-based): Sessile morphology is suspicious. A polyp is more likely benign if pedunculated. Stones: The presence of stones may induce chronic inflammation, which can predispose towards malignancy. Primary Sclerosing cholangitis increases risk of malignancy. Sixty (age) or greater.
In patients with several of these high-risk features, cholecystectomy should be considered in the presence of a polyp greater than 6 mm in size.
The typical ultrasound appearance of a polyp is a non-mobile, non-shadowing polypoid lesion extending from the wall into the lumen of the gallbladder. There may be vascular flow in the stalk.
The main differential consideration is adherent sludge, which will not have any vascular flow.
Primary gallbladder carcinoma
Gallbladder cancer is a rare malignancy with a poor prognosis. A typical clinical presentation may include right upper quadrant pain, weight loss, and jaundice.
Risk factors for development of gallbladder cancer include: Gallstones and chronic cholecystitis. Porcelain gallbladder (somewhat controversial). Primary sclerosing cholangitis. Inflammatory bowel disease (ulcerative colitis more frequently than Crohn disease). Adenomatous polyp >10 mm or >6 mm with multiple risk factors, as described above.
Ultrasound shows a polypoid mass with increased vascularity in the gallbladder. There is often direct invasion into the liver. Regional adenopathy occurs early. Bile duct obstruction may be present.
Gallbladder metastases
Metastases to the gallbladder are uncommon.
Hepatocellular carcinoma can spread directly to the gallbladder through the bile ducts.
Melanoma can spread hematogenously to the gallbladder mucosa.
Diffuse gallbladder wall thickening >3 mm (most common causes)
Fluid-overload/edematous states: Cirrhosis - Hypoalbuminemia leads to diffuse gallbladder wall thickening. Congestive heart failure. Protein-wasting nephropathy.
Inflammatory/infectious: Cholecystitis, usually with associated cholelithiasis. Hepatitis. Pancreatitis. Diverticultitis.
Infiltrative neoplastic disease: Gallbladder carcinoma. Metastases to gallbladder (rare).
Post-prandial state.
Focal Gallbladder wall thickening (common causes)
Hyperplastic cholecystoses: Adenomyomatosis and cholesterol polyp.
Vascular: Varices.
Neoplastic disease: Adenomatous polyp. Gallbladder carcinoma. Adjacent hepatic tumor.
Non-shadowing “mass” in the gallbladder lumen
Tumefactive sludge (mobile).
Blood/pus (mobile).
Gallbladder polyp (immobile).
Gallbladder carcinoma (immobile).
Echogenic gallbladder wall
Porcelain gallbladder
Gallbladder full of stones (signified by the wall-echo-shadow sign).
Emphysematous cholecystitis.
Choledocholithiasis
Choledocholithiasis is a stone in the common bile duct, generally treated with ERCP.
Mirizzi syndrome
Mirizzi syndrome is seen when a stone in the cystic duct causes inflammation and external compression of the adjacent common hepatic duct (CHD).
Essential for the surgeon to know about preoperatively because the CHD may be mistakenly ligated instead of the cystic duct. Additionally, inflammation can cause the gallstone to erode into the CHD and cause a cysto-choledochal fistula and biliary obstruction.
On ultrasound, a stone is typically impacted in the distal cystic duct, and the CHD is dilated. The cystic duct tends to run in parallel with the CHD.
Pneumobilia
Pneumobilia is air in the biliary tree. It is commonly seen after biliary interventions, but may be due to cholecystoenteric fistula or rarely emphysematous cholecystitis.
On ultrasound, small echogenic gas bubbles are seen centrally in the liver with posterior dirty shadowing.
In contrast to pneumobilia, portal venous gas (which implies bowel ischemia until proven otherwise) is peripheral and causes a spiky appearance of the portal vein spectral Doppler waveform.
Cholangiocarcinoma
Cholangiocarcinom is cancer of the bile ducts. It classically presents with painless jaundice. Most cases of cholangiocarcinoma are sporadic, although key risk factors include chronic biliary disease (in the US) and liver fluke infection (in the Far East).
The hilum is the most common location of cholangiocarcinoma. A hilar cholangiocarcinoma is known as a Klatskin tumor. Intrahepatic cholangiocarcinoma occurs uncommonly (10%).
Ultrasound plays a role in the initial evaluation of adjacent adenopathy and vascular structures. Local nodes include porta hepatis and hepatoduodenal ligament nodes. If more distal nodal disease is present, then the tumor is generally considered unresectable.
Hepatic Steatosis
Hepatic steatosis is the accumulation of excess fat within hepatocytes due to a metabolic derangement (obesity or diabetes), hepatotoxins (EtOH), or prolonged fasting.
Ultrasound shows a diffuse increase in hepatic echogenicity. Normally, the liver and kidney should have the same echogenicity. With fatty infiltration, the liver appears more echogenic than the kidney. Hepatic steatosis also causes increased sound attenuation, leading to poor visualization of deeper structures.
Focal fat sparing is a geographic area of hypoechogenicity in an otherwise fatty liver. A characteristic location of focal fat sparring is the gallbladder fossa.
Cirrhosis
Cirrhosis is the replacement of functioning hepatocytes with dysfunctional fibrotic tissue, due to long-standing repeated cycles of hepatocyte injury and repair.
Micronodular cirrhosis causes cirrhotic nodules less than 3 mm in size and is most commonly associated with alcoholism.
Macronodular cirrhosis features larger nodules (>3 mm) separated by wide scars and fibrous septae. Macronodular cirrhosis is caused by fulminant viral hepatitis which does not uniformly affect the liver.
The typical utrasound appearance of cirrhosis is a coarse, heterogeneously increased liver echotexture with a nodular external contour. In early cirrhosis, the superficial nodularity is best appreciated with a high frequency linear probe. The caudate lobe is often spared and hypertrophies in response to increased demand (the caudate has direct venous drainage into the IVC and therefore can bypass the hypertensive portal system). End-stage cirrhosis is characterized by a shrunken, nodular liver.
Signs of portal hypertension are often present, including an enlarged portal veins, splenomegaly, varices, portosystemic shunts, and a patent umbilical vein. Imaging of portal hypertension is discussed in detail in the liver Doppler section.
Viral hepatitis
Viral hepatitis is infection of the liver by a hepatotropic virus. Hepatitis B and C cause chronic disease.
The most common ultrasound finding is a normal liver. Occasionally periportal edema produces the characteristic starry sky pattern of increased portal triad echogenicity.
Acute hepatitis is often associated with diffuse severe gallbladder wall thickening.
Pyogenic abscess
Pyogenic abscess is caused by pus-forming organisms and is usually due to spread from intestinal or biliary infection (most commonly E. coli)
Infection starts as an ill-defined area of altered echogenicity (phlegmon stage) that evolves into a well-defined hypoechoic structure with internal echoes (mature abscess).
Amebic abscess
Amebic abscess is caused by Entamoeba histolytica. A near-universal presenting symptom is pain, seen in 99% of patients. The most common location is near the dome of the right lobe.
On ultrasound, an amebic abscess is indistinguishable from a pyogenic abscess and appears as a hypoechoic structure with low-level internal echoes.
Antimicrobial therapy is usually sufficient treatment, and drainage is rarely necessary.
Echinococcal cyst (hydatid disease)
Echinococcal cyst is caused by larvae of Echinococcus granulosus, most commonly found in endemic areas in the middle east, Mediterranean, and South America.
There is risk of anaphylaxis with peritoneal spillage of cyst fluid, although these are often biopsied and drained uneventfully. Medical treatment is albendazole or mebendazole.
Classic ultrasound appearance is a large liver cyst with numerous peripheral daughter cysts. A highly suggestive finding is the change in position of daughter cysts as the patient is repositioned.
The water-lily sign is an undulating membrane within the hydatid cyst.
Hydatid sand is a fine sediment caused by seperation of the membranes from the endocyst.
Candidiasis
Hepatic candidiasis is a rare infection in the immunocompromised due to Candida albicans or Candida glabrata.
On imaging, there are multiple tiny targetoid lesions. The presence of concurrent similar-appearing lesions in the spleen is highly suggestive of hepatosplenic candidiasis.
Hepatic Pneumocystis jiroveci
Hepatic Pneumocystis jiroveci is seen in disseminated disease in the severly immunocompromised. Hepatic infection is classically secondary to the use of inhaled pentamidine to treat Pneumocystis pneumonia, as pentamidine is not absorbed systemically and thus would not prevent hepatic infection.
Ultrasound shows multiple punctate echogenic calcifications in the liver and often spleen.
Cavernous hemangioma
Hepatic cavernous hemangioma is the most common benign hepatic neoplasm.
The classic ultrasound appearance of hemangioma is a solitary, circumscribed, homogenously echogenic mass with no flow on color Doppler. Posterior acoustic enhancement is nonspecific but may be present. When see, posterior acoustic enhancement is thought to correlate with hypervascularity. A hypoechoic halo should never be seen - this finding suggests malignancy.
Hepatic hemangioma can rarely have an atypica hypoechoic appearance when seen in a fatty liver.
If a solitary classic-appearing hemangioma is seen and the patient hasj an otherwise normal-appearing liver, normal LFTs, no known malignancy, and is asymptomatic, then no further workup is required.
Any hererogeneity or atypical ultrasound findings should prompt consideration of an alternative diagnosis. The differential of a hyperechoic hepatic mass includes hyperechoic hepatocellular carcinoma or metastatic disease (even in the absence of a halo). In a patient with cirrhosis or any known primary malignancy, further workup (MRI or CT) is usually warranted if the mass is new, even if classic appearing.
Focal Nodular Hyperplasia (FNH)
Focal nodular hyperplasia (FNH) is a benign hyperplastic hepatic mass with a central non-fibrotic stellate scar consisting of biliary ductules and venules.
Ultrasound findings are nonspecific. The central scar is rarely seen on ultrasound, and even when it is, this finding can be seen in other lesions, including hepatocellular carcinoma, giant hemangioma, or adenoma.
FNH is often difficult ot detect on sonography. It may be nearly isoechoic to normal liver and manifest on imaging as a subtle displacement of the hepatic contour.
Doppler findings of FHN include a spoke-wheel configuration of arterial vessels.
MRI or Tc-99m sulfur colloid scintigraphy can confirm (classically, FNH has increased uptake of sulfur colloid). MRI is by far the more useful test.
Hepatic Adenoma
Hepatic adenoma is a benign liver tumor associated with oral contraceptives, anabolic steroids, and type I glycogen storage disease (von Gierke’s disease - in which case adenomas will be multiple).
Due to high incidence of hemorrhage, adenomas are usually resected.
There are no specific ultrasound features to distinguish an adenoma from other hepatic masses. An adenoma may be hyperechoic, isoechoic, or hypoechoic relative to normal liver.
Adenoma is usually photopenic on Tc-99m sulfur colloid scintigraphy (in contrast to FNH).
Hepatic lipoma
Hepatic lipoma is a benign neoplasm composed of fat that appears as a well-defined hyperechoic mass. It may appear identical to hemagioma or hyperechoic hepatocellular carcinoma.
When multiple, may be associated with tuberous sclerosis and renal angiomyolipomas.
Biliary cystadenoma
Biliary cystadenoma is a benign cystic mass lined with biliary-type epithelium.
Although benign, most are surgically resected since malignant transformation may occur.
Biliary cystadenoma appears as a multiseptated cystic mass on all imaging modalities. Mural nodules should be regarded with suspicion. The presence of mural nodularity suggests malignant transformation to cystadenocarcinoma.
Hepatic metastases
Metastatic disease to the liver is far more common than primary hepatocellular carcinoma.
Metastases can have a variable ultrasound appearacne, although the classic finding is a hypoechoic rim producing a target sign.
Hypoechoic hepatic metastases include: Breast (can be either hypoechoic or hyperechoic). Pancreas. Lung. Lymphoma.
Hyperechoic hepatic metastases include: Colon cancer is hyperechoic in greater than 50% of cases. A hyperechoic appearance may suggest a better prognosis. Renal cell carcinoma. Breast (can be either hyperechoic or hypoechoic). Carcinoid. Choriocarcinoma.
Calcified hepatic metastases (hyperechoic with acoustic shadowing) include: Colon cancer (especially mucinous type). Gastric adenocarcinoma. Osteosarcoma (very rare).
Cystic hepatic metasteses include: Ovarian cystadenocarcinoma. Gastrointestinal sarcoma.
Infiltrative metastases include: Lung. Breast. In particular, treated breast cancer may cause a pseudo-cirrhosis appearance. Prostate.
Hepatocellular carcinoma (HCC)
Hepatocellular carcinoma (HCC) is a hepatic malignancy arising in teh setting of chronic inflammation.
Patients with cirrhosis or chronic viral hepatitis are regularly screened for HCC with serum alpha-fetoprotein levels and ultrasound. Ultrasound is not very sensitive to detect small HCC in end-stage cirrhotic livers.
HCC has a variety of ultrasound appearances - therefore, a mass in a cirrhotic liver is considered HCC until proven otherwise. High Doppler flow may be present, especially at the periphery of the mass, due to arteriovenous shunting.
HCC has a propensity for venous invasion. The portal veins should always be carefully evaluated in the presence of a hepatic mass. Internal Doppler flow within a venous clot suggests a tumor thrombus.
Fibrolamellar carcinoma
Fibrolamellar carcinoma is a variant of HCC seen in young adults without cirrhosis and is not associated with elevated alpha-fetoprotein.
Fibrolamellar carcinoma has a much better prognosis compared to typical HCC.
Hepatic lymphoma
Primary hepatic lymphoma may present as a single mass or multiple masses.
Lymphoma tends to be hypoechoic and may demonstrate the target sign typical of metastases.
Post-transplant lymphoproliferative disorder (PTLD)
Post-transplant lymphoproliferative disorder (PTLD) is a type of lymphoma caused by Epstein-Barr virus that arises after solid organ or bone marrow transplant. Patients with renal transplants are at particular risk for development of PTLD. PTLD may occur anywhere, regardless of which organ was transplanted.
Treatment is reduction/withdrawal of immunosuppression.
PTLD appears as a mass with a variable and nonspecific ultrasound appearance. Therefore, it is important to mention PTLD if a liver mass is seen in a transplant patient.
Multicystic liver
Multiple simple cysts.
Caroli disease (saccular dilation of the intrahepatic bile ducts).
Autosomal dominant polycystic kidney disease (ADPKD): Liver cysts seen in >50% of patients.
Liver cyst with internal echoes
Simple cyst with internal hemorrhage.
Liver abscess
Hematoma.
Necrotic or cystic metastasis (ovarian cystadenocarcinoma or gastrointestinal sarcoma).
Multiple echogenic liver lesions
Prior granulomatous exposure.
Disseminated pneumocystis in AIDS. Classic history is treatment with inhaled pentamidine, which does not have systemic absorption.
Portal hypertension
Portal hypertension is increased pressure of the portal venous system. It can be classified in relation to the hepatic capillary bed as pre-sinusoidal, sinusoidal, or post-sinusoidal: Pre-sinusoidal: Insult is proximal to the hepatic parenchyma, such as portal vein thrombosis. Sinsusoidal: Insult is hepatic in origin, such as cirrhosis. Post-sinusoidal: Insult is beyond the liver, such as Budd-Chiari (heptic vein thrombosis) or IVC thrombosis.
Normally, the portal veins and hepatic arteries flow in the same direction, toward the liver. This direction is called hepatopedal flow (-petal =toward). The normal portal venous waveform is above the baseline (hepatopetal) and gently undulating.
A pulsatile portal venous waveform is abnormal. The differential diagnosis for a pulsatile portal venous waveform includes tricuspid regurgitation and right-sided CHF. The differential diagnosis for hepatic vein pulsatility is similar, and is discussed in the following section.
Portal pressure is defined as a direct portal venous pressure of >5 mm Hg, although the portal venous pressure is not measured directly.
Ultimately, when portal venous pressure is higher than forward pressure, the portal venous flow will reverse, which is diagnostic for portal hypertension. Reversal of portal venous flow is called hepatofugal flow (-fugal = away, same Latin root as fugitive).
In addition to flow reversal, there are several secondary findings of portal hypertension: Low portal venous velocity (<16 cm/sec) Dilated portal vein (13 mm is the maximal normal diameter in quiet respiration). Splenomegaly. Varices. Portosystemic shunts are often present, most commonly gastro-esophageal, paraumbilical, or splenorenal. Note that an isolated portosystemic shunt may not be caused by portal hypertension. For instance, isolated obstruction of the splenic vein from pancreatitis or neoplasm may lead to a shunt. A recanalized umbilical vein is a portosystemic shunt that is diagnostic of portal hypertension.
Transjugular intrahepatic portosystemic shunt (TIPS)
Portal hypertension (and reversal of portal flow) can be treated with a transjugular intrahepatic portosystemic shunt (TIPS), which connects a branch of the portal vein to a systemic hepatic vein.
Ultrasound is used for surveillance of TIPS patency, starting with a post-procedure baseline. Routine follow-up is performed according to the following schedule: In 1 month, every 3 months for the first year, and then every 6-12 months.
Flow in a patent TIPS will be towards the hepatic veins, and flow in the portal veins will be towards the TIPS. Therefore, flow in the main portal vein will be hepatopetal and flow in the right and left portal vein will be hepatofugal (highlighted below with yellow circles).
If the TIPS becomes occluded, the right and left portal veins will “re-reverse” and become hepatopetal.
Portal vein thrombosis
Thrombosis of the portal vein can be bland (simple thrombosis) or may be due to tumor invasion.
Bland portal vein thrombosis can be caused by general hypercoagulable state or may be due to local inflammation from pancreatitis or hepatitis. In infants, omphalitis may also lead to portal vein thrombosis.
Tumor thrombus is most commonly caused by hepatocellular carcinoma.
Ultrasound of portal vein thrombosis shows lack of portal venous flow, often with echogenic thrombus within the portal vein. Expansion of the portal vein can be seen with either bland or tumor thrombus. On color Doppler, flow within the thrombus suggests tumor thrombus.
One potential pitfall to be aware of is slow (<16 cm/sec) or stagnant portal venous flow in the presence of portal hypertension which may mimic portal vein thrombosis.
Long-standing portal vein thrombosis leads to cavernous transformation of the portal vein, characterized by formation of multiple small periportal collaterals.
Portal venous gas
Portal venous gas is due to abdominal catastrophe (ischemia and infarction) until proven otherwise. If the cause of the portal venous gas is unkown, CT should be performed emergently.
Grayscale ultrasound shows peripheral patchy branching foci of hyperechogenicity that are often transient. Spectral Doppler of the portal vein features numerous characteristic spikes.
In contrast to protal venous gas, pneumobilia tends to be more central.
Normal hepatic vein waveform
The hepatic veins feed into the IVC and the right side of the heart. The spectral Doppler waveform of the hepatic veins is therefore affected by the cardiac cycle.
The normal hepatic venous waveform has three distinct components: The A, S, and D waves. Note that antegrade flow is defined as forward flow in the normal expected direction.
Increased hepatic vein pulsatility: Accentuated A-wave
Increased hepatic vein pulsatility is caused by a right-sided cardiac abnormality, either right-sided heart failure or tricuspid regurgitation. Both conditions are characterized by accentuation of the A-wave due to increased retrograde flow during atrial systole.
Normally, the tricuspid valve closes at the beginning of ventricular systole (the beginning of the S-wave).
In tricuspid regurgitation, there is some degree of blood flow from the right ventricle into the right atrium during ventricular systole, allowing less blood to return to the right atrium from the hepatic veins and IVC during ventricular systole. This results in a decreased or even retrograde S-wave.
In right-sided heart failure, the tall A-wave is due to increased right atrial pressure; however, in contrast to tricuspid regurgitation, the S-wave is normal since the tricuspid valve remains competent.
Decreased hepatic vein pulsatility
Decreased hepatic vein pulsatility is seen in cirrhosis, Budd-Chiari (hepatic vein thrombosis), and hepatic veno-occlusive disease.
Pancreatitis
Pancreatitis is inflammation of the pancreatic parenchyma, most often caused by alcohol or gallstones.
Ultrasound is useful in the initial evaluation of pancreatitis to evaluate for gallstones or biliary obstruction.
Usually, the pancreas appears normal in acute pancreatitis. The pancreas may be diffusely enlarged and relatively hypoechoic due to edema. More severe inflammation may cause the normally hypoechoic pancreas to become isoechoic to liver.
Ultrasound has limited utility in evaluating complications of pancreatitis such as pancreatic necrosis or peripancreatic fluid collections.
Complications of acute pancreatitis may be inflammatory, infectious, or vascular: A pancreatic pseudocyst is usually detectable by ultrasound, although the full extent of large pseudocysts can be difficult ot determine by ultrasound alone.
Infectious compications of acute pancreatitis include peripancreatic abscess, infected pseudocyst, and infected pancreatic necrosis.
The two most important vascular complications of pancreatitis are splenic vein thrombosis and splenic artery pseudoaneurysm, both of which can be characterized by Doppler ultrasound.
Chronic pancreatitis
Chronic pancreatitis is caused by repeated bouts of acute pancreatitis (most commonly alcoholic).
The classic ultrasound appearance of chronic pancreatitis is an atrophied gland, with diffuse calcifications and dilated and beaded distal pancreatic duct.
Calculi within the pancreatic duct may also be seen.
Pancreatic adenocarcinoma
Pancreatic adenocarcinoma is the most common pancreatic tumor, and is typically seen in older males.
Small tumors are hypoechoic, while larger masses may be more heterogenous. It can be difficult to identify the tumor extent on ultrasound because of infiltrative margins and invasion of the tumor into pancreatic parenchyma and adjacent structures.
The most common locationfor a tumor to arise is the pancreatic head, where the mass often presents with ductal obstruction. The double duct sign represents dilation of both the pancreatic and common bile ducts caused by malignant obstruction.
Cystic pancreatic neoplasms
Cystic pancreatic neoplasms are a diverse group of unrelated pancreatic tumors that may appear similar by ultrasound.
Serous cystadenoma is a benign tumor seen in older females, consisting of multipe tiny cysts. A characteristic calcified scar is not often seen, but is very specific when present.
Mucinous cystic neoplasm has malignant potential, and is usually seen in middle-aged females. Compared to serous cystadenoma, the cysts are larger in size. The mucin can generate numerous fine echoes.
Intraductal papillary mucinous neoplasm (IPMN) is a neoplasm of variable and controversial natural history that communicates with either the main pancreatic duct or branch ducts. Demonstration of the ductal communication can be difficult by ultrasound.
Pancreatic endocrine tumors
Tumors arising from the neuroendocrine cells of the pancreas may be either functioning or nonfunctioning.
Functioning tumors are usually symptomatic, small at diagnosis, and identified through biochemical testing. In contrast, nonfunctioning tumors may be asymptomatic, and hence, large at the time of diagnosis.
Intraoperative ultrasound continues to gain ground and is helpful in identifying small tumors at surgery.
Insulinomas are the most common pancreatic tumors. Preoperative ultrasound detection is difficult and is successful less than 60% of the time. When seen, insulinomas are hypoechoic, encapsulated pancreatic nodules.
Gastrinomas are the second most common pancreatic endocrine tumors. Liver metastases are present at the time of diagnosis in 60% of patients.
Pancreatic lymphoma
B-cell lymphoma is the most common subtype of lymphoma to affect the pancreas, and is almost always associated with adenopathy, and multi-organ involvement by the time the pancreas is involved.
The typical ultrasound appearance of pancreatic lymphoma is diffusely enlarged, hypoechoic gland.
Splenic calcifications
Granulomatous disease: Calcifications may be scattered or diffuse.
Splenic infarct.
Hematoma.
Calcified splenic artery aneurysm.
Cystic splenic lesion: Color Doppler should always be used to exclude a vascular etiology
Splenic artery aneurysm or pseudoaneurysm.
Hematoma.
Abscess.
Pancreatic pseudocyst.
Echogenic splenic lesion
Hemangioma (can also be hypoechoic).
Hamartoma.
Lymphangioma.
Hypoechoic splenic lesion
Laceration (in the setting of trauma)
Abscess.
Lymphoma.
Sarcoidosis.
Metastasis.
Infarct (tends to be peripheral).
Extramedullary hematopoiesis.
Splenomegaly (defined as >14 cm in sagittal plane)
Mild to moderate splenomegaly: Portal hypertension (most common). Infection. AIDS.
Moderate to marked splenomegaly: Leukemia/lymphoma. Infectious mononucleosis.
Massive splenomegaly: Myelofibrosis.
Evaluation of kidney stones
Ultrasound is an excellent modality for evaluation of nephrolithiasis, which may cause renal obstruction and resultant hydronephrosis.
An echogenic shadowing focus in the kidney, ureter, or bladder, is suspicious for a stone.
After diagnosing a renal or ureteral calculus, one should always evaluate for the presence of hydronephosis and perinephric fluid.
Approach to hydronephrosis
The most common cause of hydronephrosis is an obstructing calculus.
Although hydronephrosis is usually due to ureteral obstruction, it is possible tohave hydronephrosis without obstruction. For instance, vesicoureteral reflux or pregnancy may cause a dilated ureter without obstruction. Pregnancy preferentially affects the right side.
Likewise, obstruction without hydronephrosis may also be seen in: Very acute obstruction. Obstruction with dehydration, where there is insufficient urine production to create a pressure backup. Obstruction with ruptured fornix. Increased pressure from obstruction may cause a fornix to rupture, which could decompress the renal pelvis and spill fluid into the perinephric space.
Pitfalls in diagnosing hydronephrosis
It can sometimes be difficult to distinguish between hydronephrosis and multiple renal sinus cysts. Renal sinus cysts are subsequently discussedand include peripelvic and parapelvic cysts. On imaging, renal sinus cysts will show a single or mulitple discrete cystic lesions that do not communicate with each other.
In true hydronephrosis, all the dilated fluid-filled spaces are contiguous.
Resistive index (RI) may be helpful in diagnosing obstruction
The renal resistive index (RI) may be elevated in acute obstruction, thought to be due to cytokine-mediated renal artery vasoconstriction.
The resitive index is calculated with pulse-width Dopper of the renal segmental or arcuate arteries. RI = (PSV - EDV)/PSV. PSV = peak systolic velocity. EDV = end diastolic velocity. Higher resistive indices. With no diastolic flow PSV/PSV = 1. Reversal of diastolic flow technically causes RI > 1, although in such cases RI is not measured.
A RI of >0.7 on the affected side, or a difference of >0.1 between kidneys suggests acute obstruction. Bilateral elevated RIs (>0.7) are nonspecific and can be due to any number of medical renal processes.
The resistive index is not used to diagnose chronic obstruction.
Ureteral jets may be helpful but are controversial
A ureteral jet is flow of urine into the bladder as seen by color Doppler.
Flow from the kidney to the bladder would be completely eliminated in complete obstruction, so theoretically the presence of a utereral jet rules out a complete obstruction. However, ureteral jets are very commonly seen even with stones, and jets are often absent in normal patients.
Angiomyolipoma (AML)
An angiomyolipoma is a benign hamartoma made up of blood vessels (angio), smooth muscle (myo), and fat (lipoma).
Although benign, there is an increased risk of hemorrhage if >4 cm in size. The hemorrhage may be caused by microaneurysm rupture within the vascular elements of the AML.
On ultrasound, AML is echogenic due to the fat component. There is considerable overlap between the ultrasound appearance of AML and renal cell carcinoma. About one third of AML demonstrate shadowing, which is a specific finding for AML. Multiple AML are seen in tuberous sclerosis.
Oncocytoma
Oncocytoma is a benign renal tumor arising from tubular cells.
On ultrasound, oncocytoma is indistinguishable from renal cell carcinoma (RCC). It may be hypoechoic, isoechoic, or hyperechoic. A spoke-wheel vascular pattern is sometimes seen on color Doppler.
Due to imaging overlap with RCC, oncocytomas are treated surgically, even if the typical stellate or spoke-wheel vessels are seen.
Renal cell carcinoma (RCC)
Renal cell carcinoma (RCC) is the most common solid renal mass.
The staging of RCC uses the Robson system, which is discussed in the genitourinary section.
RCC is most often isoechoic to renal cortex, but can occasionally be hypoechoic or even hyperechoic (mimicking AML). A hypoechoic rim and intratumoral cystic changes are typically seen only in RCC, which may help distinguish it from AML.
In the presence of a renal mass, the renal veins must be carefully evaluated as RCC has a propensity for venous invasion. Venous invasion is Robson stage IIIA, and the presence of venous invasion has important implications for surgical approach.
Color and spectral Dopller are helpful in differentiating bland renal vein thrombus (which would not be stage IIIA) from tumor thrombus. Tumor thrombus will have color Doppler flow with an artrial waveform.
Renal lymphoma
Renal lymphoma (most commonly high-grade B-cell) may disseminate hematogenously or spread directly from the retroperitoneum to the kidney. Primary renal lymphoma is very rare and of uncertain origin as there is no native lymphoid tissue within the kidney.
The most common imaging presentation of renal lymphoma is multiple hypoechoic renal masses. Retroperitoneal adenopathy is usually present. A solitary mass is an uncommon presentation. Diffuse lymphomatous infiltration producing nephromegaly is rare.
Potential pitfalls in diagnosing a cystic lesion
Renal scanning should be performed with multiple angles of insonation to differentiate hydronephrosis from a renal sinus cyst (parapelvic or peripelvic cyst). In hydronephrosis, the dilated spaces will all connect.
Color Doppler should always be utilized, as a renal artery aneurysm may mimic a cyst in grayscale.
Simple cortical cyst
A simple renal cyst should have the sonographic hallmarks of a simple cyst, featuring an imperceptibly thin wall, anechoic internal contents, and posterior through transmission.
Harmonic imaging can be helpful in confirming the diagnosis of simple renal cyst by eliminating artifactual low-level internal echoes.
Renal sinus cyst
A cyst in the renal sinus may be a peripelvic or parapelvic cyst. Peripelvic cysts are secondary to lymphatic obstruction and are often multiple. In contrast, a parapelvic cyst is a renal parenchymal cyst that herniates into the renal sinus and is usually solitary.
When multiple renal sinus cysts are present (most commonly peripelvic cysts), the appearance may mimic hydronephrosis. In contrast to hydronephrosis, renal sinus cysts will not be contiguous with each other.
Renal abscess
Renal infection, discussed below, may appear as a complex cystic renal mass.
Cystic renal cell carcinoma
Although most cases of RCC present as a solid renal mass, a significant minority may present as a complex cystic lesion. Worrisome ultrasound findings of a complex cystic mass include thick septa, irregular wall thickening, and a mural nodule.
The Bosniak classification of complex renal masses is based on CT appearance and depends on the enhancement. The Bosniak classification is described in the genitourinary imaging section.
Acute diffuse pyelonephritis
Pyelonephritis is infection of the renal parenchyma, usually by gram-negative urinary tract organisms that ascend from the lower genitourinary tract.
The most common ultrasound appearance of pyelonephritis is a normal kidney. Occasionally generalized renal edema and engorgement can be seen.
Focal pyelonephritis
Focal pyelonephritis is a focal or multifocal infection of the renal parenchyma.
The classic ultrasound appearance is a hypoechoic mass (or masses) with low-amplitude echoes that disrupts the corticomedullary junction. A distinct wall is lacking.
Renal abscess
A renal abscess is a focal necrotic parenchymal infection with a defined wall. Urinalysis may be negative up to 30% of the time if the infection does not involved the collecting system.
Small abscesses (<3 cm) often undergo a trial of conservative medical therapy, while larger abscesses are typically drained.
Ultrasound shows a fluid-filled renal mass with a distinct wall, which may be multiloculated.
Emphysematous pyelonephritis
Emphyesematous pyelonephritis is a complication of acute pyelonephritis characterized by replacement of renal parenchyma by gas. It is caused by gas-forming organisms, most commonly E. coli. Emphysematous pyelonephritis is almost exclusively seen in diabetic or immunocompromised individuals.
Emphysematous pyelonephritis is a surgical emergency requiring broad-spectrum antibiotics and emergent nephrectomy. Mortality can reach 40%.
Ultrasound shows high-amplitude echoes in the renal parenchyma representing gas locules with posterior dirty acoustic shadowing.
Tuberculous pyelonephritis
Tuberculosis pyelonephritis, caused by hematogenous spread of M. tuberculosis, is characterized by focal cavitary renal lesions with calcification.
Putty kidney is an atrophic, calcified kidney seen in end-stage renal tuberculosis.
Xanthogranulomatous pyelonephritis
Xanthogranulomatous pyelonephritis results from repeated cyscles of chronic low-grade infection caused by an obstructing calculus that leads to fibrofatty replacement of renal parenchyma.
On ultrasound, the kidneys are enlarged with areas of mixed echogenicity. A central stone is nearly universally present, which may be staghorn in morphology.
Pyonephrosis
Pyonephrosis is infection of an obstructed collecting system and is a surgical emergency. Treatment is emergent relief of obstruction, either with percutaneous nephrostomy or ureteral stent.
Ultrasound features echoes within a dilated collecting system. A fluid level may be present.
HIV associated nephropathy
The HIV virus may directly infect the renal parenchyma to produce HIV nephropathy, most commonly resulting in focal segmental glomerulosclerosis (FSGS). HIV nephropathy clinically presents with nephritic renal failure.
The kidneys are characteristically echogenic. Enlarged echogenic kidneys are specific for HIV nephropathy, although the kidneys are enlarged only about 20% of the time.
Autosomal dominant polycystic kidney disease (ADPKD)
Autosomal dominant polycystic kidney disease (ADPKD) is the most common cause of multiple renal cysts in adults. ADPKD is associated with cysts in the liver and other visceral organs.
15% of patients have saccular cerebral aneurysms.
The natural history of ADPKD is renal failure by middle age.
ADPKD does not confer an increased risk of renal cell carcinoma; however, complex cysts with internal hemorrhage are difficult to distinguish from renal cell carcinoma.
Imaging of ADPKD shows markedly enlarged kidneys with innumerable cysts of varying size and echogenicity.
Autosomal recessive polycystic kidney disease (ARPKD)
Autosomal recessive polycystic kidney disease (ARPKD) is a diagnosis of infancy. Prognosis is poor. If the child survives infancy, hepatic fibrosis usually develops.
ARPKD presents in utero as enlarged echogenic kidneys since the cysts are too small too be individually resolved by ultrasound.
Acquired renal cystic disease
Patients on long-term dialysis often develop many small renal cysts superimposed upon atrophic kidneys. Acquired cystic disease does not confer an increased risk of renal cell carcinoma, in contrast to ADPKD.
Approach to renal transplant
The goal of ultrasound evaluation after renal transplant is to determine whetehr there is treatable surgical or vascular complication. Ultrasound is not useful for differentiating among the various kinds of parenchymal rejection.
The transplanted kidney is implanted in the right or left iliac fossa (right more commonly), and is often very well imaged due to its superficial location.
An elevated RI (>0.7) suggests renal dysfunction, but this finding is nonspecific.
Surgical complications following renal transplant
Ureteral obstruction is apparent on ultrasound as hydronephrosis.
Fluid collection (blood, pus, urine) is highly dependent on timing: Immediately postoperative: Hematoma; 1-2 weeks postoperative: Urinoma; 3-4 weeks postoperative: Abscess; 2nd month and beyond: Lymphocele.
Vascular complications following renal transplant
Renal vein thrombosis: The renal artery Doppler may show reversal of diastolic flow.
Renal artery stenosis: Elevated flow velocities are seen at the site of stenosis, with a parvus et tardus waveform distal to the stenosis. Usually takes several weeks to months to develop.
Pseudoaneurysm is usually due to renal biopsy.
Medical complications
Medical complications generally cannot be differentiated on ultrasound. Biopsy is necessary for diagnosis, although the time elapsed since the transplant may be a helpful clue.
Hyperacute rejection: Occurs in first few hours after transplant. Hyperacute rejection is very rare, and is due to ABO blood type incompatibility.
Acute tubular necrosis (ATN): Occurs in the immediate flow postoperative days. ATN is usually a sequela of pre-impantation ischemia.
Acute rejection: Occurs within three months of transplant.
Chronic rejection: Occurs after three months of transplant.
Drug toxicity may be caused by cyclosporine, which is nephrotoxic.
Post-transplant lymphoproliferative disorder (PTLD)
Post-transplant lymphoproliferative disorder (PTLD) is a type of lymphoma that is thought to be due to immune suppression and Epstein-Barr virus proliferation.
PTLD can arise anywhere in the body. Any new mass in any organ in a transplant patient should raise concern for potential PTLD.
Ultrasound of renal PTLD will show an amorphous hypoechoic mass that may simulate a fluid collection on grayscale images. Unlike fluid, PTLD will demonstrate Doppler flow.
Medullary nephrocalcinosis
Any cause of hypercalcemia and hypercalciuria can cause medullary calcification.
Hyperparathyroidism is the most common cause of medullary nephrocalcinosis.
Renal tubular acidosis (distal type).
Medullary sponge kidney is caused by ectatic tubules in the medullary pyramids leading to stasis and stone formation.
Papillary necrosis.
In a child, treatment with furosemide can lead to medullary nephrocalcinosis.
Cortical nephrocalcinosis
Much more rare than medullary nephrocalcinosis, cortical nephrocalcinosis is due to diffuse cortical injury.
Acute cortical necrosis.
Hyperoxaluria (rare).
Alport syndome.
Autosomal recessive polycystic kidney disease.
Echogenic kidneys
Echogenic kidneys are most commonly due to medical renal disease, such as diabetic nephropathy, glomerulosclerosis, acute tubular necrosis, etc.
HIV nephropathy causes enlarged and echogenic kidneys.
Echogenic renal mass
Angiomyolipoma (AML). A shadowing echogenic renal mass is relatively specific for AML.
Malignant neoplasm (atypical appearance).
Renal calculus.
Intrarenal gas.
Milk of calcium, caused by cystals precipitating out of supersaturated solution.
Sloughed papilla, secondary to papillary necrosis, may appear as an echogenic mass in the collecting system.
Scrotal Anatomy
Epididymis: The epididymis carries sperm away from the testical to the vas deferens. The epididymis is composed of head, body, and tail. The head may measure up to 10 mm. The epididymis is normally hypoechoic and has less blood flow compared to the testicle. Relatively increased epididymal blood flow can be seen in epididymitis.
Mediastinum testis: The mediastinum testis is fibrous tissue in the hilum of the testicle, from which fibrous septa radiate towards the testicular periphery. It provides structural support to the rete testis.
Rete testis: The rete testis is a network of tubules that carries sperm from the seminiferous tubules to teh vas deferens. It functions to concentrate sperm.
Approach to a testicular mass
Intratesticular masses are usually malignant (90-95%). Conversely, most extratesticular masses are benign in an adult, although a pediatric mass in this location may be malignant.
The retroperitoneum should always be evaluated if an intratesticular mass is seen. Likewise, if retroperitoneal adenopathy is seen in a reproductive-age male, the testicles should always be examined.
Most scrotal masses are hypoechoic relative to normal testicular parenchyma.
On Doppler, most masses will have increased vascularity with high diastolic flow, producing a low resistance waveform.
Malignant germ cell tumor (GCT): Seminoma
Seminoma is the most common testicular malignancy. It has a favorable prognosis. Seminoma typically occurs in middle-aged men. Uncommonly, hCG may be elevated.
The spermatocytic subtype of seminoma occurs in slightly older men (mid 50s) and has excellent prognosis with orchiectomy only. Tumor markers are not elevated.
Malignant germ cell tumors: Nonseminomatous germ cell tumors (NSGCT)
Nonseminomatous germ cell tumors (NSGCT) include embryonal carcinoma, teratoma, yolk sac tumor, choriocarcinoma, and mixed subtypes. Mixed germ cell tumor is the most common NSGCT, and is the second most commo primary testicular malignancy after seminoma. The most common components of mixed NSGCT are embryonal carcioma and teratoma. Embryonal cell carcinoma in its pure form is rare and in adults is typically seen as a component of mixed germ cell tumors. The infantile form, called endodermal sinus tumor or yolk sac tumor, the most common testicular tumor of infancy. AFP is elevated. Teratoma is rare in its pure form in adults, but is seen in 50% of mixed NSGCT. Teratoma is classified as mature, immature, and malignant. In adults, teratomas are usually malignant. In children, teratomas, are usually benign, with the mature subtype most commonly seen. Choriocarcinoma is the most aggressive and rare NSGCT. Choriocarcinoma metastasizes early, especially to brain and lung. Metastasis tend to be hemorrhagic. hCG is always elevated and gynecomastia may result from elevated chorionic gonadotropins.
NSGCT generally occur in younger pateitns compared to seminomas, typically in young men in their 20s and 30s. NSGCT tend to be more aggressive than seminomas. Local invasion into the tunica albuginea and visceral metastases are common.
A heterogenous testicular mass that contains solid and cystic components and coarse calcificiation is a typical appearance for a NSGCT. It is not possible to distinguish the various subtypes of NSGCT on sonography.
Burnt-out germ cell tumor
Burnt-out germ cell tumor is a primary testicular neoplasm that is no longer viable in the testicle even though there is often viable metastatic disease, especialy retroperitoneal.
In the testicle, focal calcification with shadowing is characteristic. A mass may or may not be present.
Treatment is orchiectomy in addition to systemic chemotherapy.
Testicular microlithiasis
Testicular microlithiasis is multiple punctate testicular calcifications.
There is controversial association between microlithiasis and testicular neoplasm. While the overall absolute risk for developing testicular cancer remains very small inthe presence of microlithiasis, the relative risk may be increased.
Current guidelines do not support screening by ultrasound or tumor markers, but patients with microlithiasis may perform self-examinations and be seen in follow-up as needed.
At least five microcalcifications must be present per image to be called microlithiasis. If there are fewer than five microcalcifications the term limited microlithiasis isused.
Microlithiasis can produce a starry sky appearance is calcifications are numerous. In the liver, hepatitis can cause a starry sky appearance due to increased echogenicityof the portal triads.
Testicular metastases
The most common metastases to the testicles are leukemia and lymphoma, as the relevant chemotherapeutic agents do not cross the blood-testis barrier.
Hematologic malignancies typically present in older patients, tend to be bilateral, and may be infiltrative with diffuse testicular enlargement.
Benign testicular tumors
An epidermoid is a keratin-filled cyst with a distinctive onion-ring appearance of concentric alternating rings of hypo- and hyperechogenicity. If suspected, local excision is performed instead of the standard orchiectomy typically performed for presumed malignant masses.
Sex-cord stromal tumors are 90% benign but are sonographically indistinguishable from malignant tumors. Orchiectomy is therefore the standard treatment. Leydig cell tumor can present with gynecomastia due to estrogen secretion. Sertoli cell tumor is associated with Peutz-Jeghers and Klinefelter syndromes.
Sarcoidosis
Sarcoidosis may involve either the testis, the epididymis, or both. Scrotal involvement is rare, but presents clinically as painless scrotal enlargement.
The ultrasound appearance of testicular sarcoid is indistinguishable from a solid malignant mass. If sarcoidosis is suggested by clinical history, the testicular mass must be biopsied to exclude malignancy. Without tissue pathology, a mass cannot be assumed to be sarcoid.
Benign testicular tumor mimics
Congenital adrenal rests are embryologic remnants of adrenal tissue trapped within the testis. These are typically seen in newborns with congenital adrenal hyperplasia. Adrenal rests appear as bilateral hypoechoic masses and classically enlarge with ACTH exposure.
Polyorchidism/supernumerary testis: An extra testicle has an identical imaging appearance to normal testicular parenchyma. Extranumerary testes carry a slightly increased risk of torsion and testicular cancer.
Extra-testicular masses
In contrast to intratesticular masses, extratesticular masses are usually benign. Up to 16% of extratesticular masses may be malignant, however, and ultrasound cannot reliably differentiate benign from malignant masses.
Spermatic cord lipoma is the most common extratesticular neoplasm ovverall.
Benign adenomatoid tumor of the tunica albuginea is the most common epididymal neoplasm.
Hydrocele
A hydrocele is excess fluid in the scrotum surrouding the testicle. Most are asymptomatic.
A hydrocele may be congenital (due to patent processus vaginalis in utero or infancy), idiopathic, or post-inflammatory. Regardless of etiology, there is never fluid at the bare are where the testicle is attached to the tunica vaginalis.
Hematocele
A hematocele is blood in the scrotum due to trauma or torsion.
Varicocele
A varicocele is a dilated venous pampiniform plexus in the scrotum. A primary varicocele is due to incompetent valves of the internal spermatic vein. A secondary varicocele is due to inceased venous pressure caused by an obstructing lesion.
Varicocele is a common cause of infertility, seen in up to 40% of males presenting to an infertility clinic.
Varicoceles are much more common on the left as the left testicular vein drains into the left renal vein and the superior messenteric artery can compress the left renal vein. In contrast, the right testicular vein drains directly into the infrarenal IVC.
85% of varicoceles are left-sided and 15% are bilateral. An isolated right-sided varcocele should prompt a search for a right-sided retroperitoneal mass.
On ultrasound, varicoceles appear as multiple tubular and serpentine anechoic structures >2 mm in diameter in the region of the upper pole of the testis and epididymal head. The varicoceles follow the spermatic cord into the inguinal canal and can be compressed by the transducer. Careful optimization of Doppler paremeters shows the slow venous flow within the varicocele.
Epididymal cysts and spermatocele
An epididymal cyst is an anechoic fluid-containing cyst that can occur anywhere in the epididymis.
A spermatocele is cystic dilation of the epididymis filled with spermatozoa, usually occuring in the epididymal head. Classic ultrasound appearance is an epididymal cyst with internal low-level mobile echoes.
A simple epididymal cyst and a spermatocele cannot always be reliably distinguished by ultrasound.
Carotid stenosis
Scanning Orientation Pelvis
The sagittal scan plane is rotated 90 degrees between transabdominal and endovaginal orientation. The patient typically empties her bladder prior to endovaginal scanning.
Overview of uterine malformation
Uterine malformations are due to abnormal development of the paired Mullerian ducts, which normally fuse during embryogenesis.
Complete failure of fusion -> didephlys uterus
Partial failure of fusion -> bicornuate uterus
Failure of resorption of inner-Mullerian septa -> septate uterus (by far most common uterine anomaly).
Congenital uterine abnormalities may be associated with urinary tract abnormalities such as renal ectopica or agenesis. The kidneys should be evaluated if a uterine malformation is seen.
Uterine anomalies increase the risk of reproductive problems since the uterine cavity (or cavities) are abnormally small and/or abnormal in contour.
The American Fertility Society (now known as the American Society of Reproductive Medicine) classifies Mullerian duct anomalies. Class I is uterine agensesis/hypoplasia, class II is a unicornuate uterus, and class III through VII represent the anomalies discussed below.
NEJM Fetal Viability
Overview of ectopic pregnancy
Ectopic pregnancy is defined as a pregnancy outside of the endometrial cavity. Hemorrhage and resultant hypovolemic shock may be life-threatening to the mother.
The classic clinical presentation of ectopic pregnancy is a positive pregnancy test, vaginal bleeding, pelvic pain, and tender adnexal mass. This presentation is seen in less than 50% of patients.
Ectopic locations
Most (~95%) ectopic pregnancies occur in the fallopian tube, with the ampullary segment being the most common iste.
It is rare for an ectopic pregnancy to be in the ovary (< 1% of all ectopics).
An especially dangerous location for an ectopic pregnancy is the interstitial portion of the fallopian tube. An interstitial ectopic carries an especially high risk of catastrophic hemorrhage due to its propensity for delayed rupture and proximity to the ovarian vessels. Ultrasound of an interstitial ectopic shows absent myometrium along the lateral edge. The interstitial line sign represents a thin, echogenic line extending from the endometrial canal to the center of the interstitial ectopic mass. This echogenic line is thought to represent the nondistended, empty endometrial canal.
A heterotopic pregnancy is a simultaneous IUP and ectopic pregnancy. Patients undergoing assistive reproductive techniques are at increased risk for heterotopic pregnancy. Prior to the popularity of these fertilization procedures, heterotopic pregnancies were extremely rare. Given the increased prevalence of assistive reproductive techniques, however, the adnexae must be carefully evaluated even in the presence of an IUP.
Ectopic pregnancy may also occur (rarely) in a prior Cesarean section scar, in the cervix, or in the abdomen. When in the abdomen, the ectopic prenancy can become large before causing symptoms.
