Flashcards Renal and Bladder Ultrasound: Cysts, Tumors, and Disorders

Simple renal cyst

The most common renal mass, usually acquired and benign. On ultrasound, it appears as a round or oval, anechoic structure with a thin, smooth wall, posterior acoustic enhancement, and no internal echoes. It is commonly located in the renal cortex.

Complex renal cyst

A cystic structure containing features such as internal echoes, septations, or calcifications. On ultrasound, it may have thick or irregular walls, internal debris, and thick septations. Thicker septations and other suspicious features increase concern for malignancy, but imaging findings alone cannot confirm cancer.

Renal sinus parapelvic cyst

A cyst that originates in or near the renal sinus. On ultrasound, it appears as an anechoic structure near the renal pelvis and may resemble hydronephrosis. Unlike hydronephrosis, parapelvic cysts are separate structures and do not communicate with the collecting system. They are usually asymptomatic.

Von Hippel-Lindau disease

An inherited genetic disorder that causes tumors and cysts to develop in multiple organs throughout the body, including the kidneys. On ultrasound, multiple renal cysts or solid renal masses may be identified.

Tuberous sclerosis

A genetic disorder that causes benign tumors to develop in multiple organs. The kidneys may contain multiple angiomyolipomas and cysts. On ultrasound, angiomyolipomas typically appear as hyperechoic masses.

Acquired cystic kidney disease

A condition that develops in patients with chronic kidney disease, particularly those undergoing long-term dialysis. It is characterized by multiple small renal cysts. On ultrasound, the kidneys may appear small and echogenic with several cysts.

Autosomal-recessive polycystic kidney disease (ARPKD)

An inherited disorder in which the renal collecting ducts become dilated, causing enlarged kidneys and impaired renal function. It commonly presents in infancy or childhood and may be associated with liver disease and portal hypertension. On ultrasound, the kidneys are typically bilaterally enlarged and echogenic, with loss of normal corticomedullary differentiation. The cystic changes may appear as numerous small structures rather than large, distinct cysts.

Autosomal-dominant polycystic kidney disease (ADPKD)

An inherited disorder characterized by the development of numerous renal cysts, commonly presenting in adulthood. It may progress to end-stage renal disease and is associated with an increased risk of certain aneurysms. On ultrasound, both kidneys are typically enlarged and contain multiple cysts of varying sizes throughout the cortex and medulla, creating an irregular appearance.

Multicystic dysplastic kidney (MCDK)

A congenital condition in which abnormal kidney development results in multiple cysts and little or no normally functioning renal tissue. It is commonly unilateral. On ultrasound, the affected kidney contains multiple noncommunicating cysts of varying sizes with little recognizable normal renal parenchyma. The affected kidney may be enlarged in infants and can become small over time.

Medullary cystic kidney disease

A genetic kidney disorder associated with progressive renal dysfunction and tubulointerstitial damage. On ultrasound, the kidneys may be small and echogenic, with reduced corticomedullary differentiation. Medullary cysts may be present but can be too small to visualize.

Renal cell carcinoma (RCC)

A malignant tumor arising from the renal tubular epithelium. It is the most common primary malignant renal tumor in adults and may be associated with smoking and other risk factors. On ultrasound, it usually appears as a solid mass that may be isoechoic, hypoechoic, or hyperechoic, depending on its composition. Larger tumors may have heterogeneous echogenicity, cystic areas, calcifications, or internal vascularity.

Transitional cell carcinoma (urothelial carcinoma)

A malignant tumor arising from the urothelial lining of the renal pelvis, ureters, or bladder. On ultrasound, it may appear as a hypoechoic or solid mass within the collecting system. It can cause urinary obstruction and hydronephrosis.

Squamous cell carcinoma

A rare, aggressive malignancy that may develop in the renal pelvis and is associated with chronic irritation, inflammation, or urinary stones. On ultrasound, it may appear as a solid mass or an infiltrative lesion involving the renal pelvis.

Renal lymphoma

A malignancy involving lymphatic tissue that affects the kidneys, often as a secondary manifestation of systemic lymphoma. On ultrasound, it may appear as multiple hypoechoic masses, diffuse renal enlargement, or bilateral infiltration.

Renal metastases

Secondary malignant tumors that spread to the kidneys from another primary cancer, such as lung or breast cancer. On ultrasound, they may appear as multiple hypoechoic or heterogeneous masses, although their appearance varies.

Nephroblastoma (Wilms tumor)

A malignant renal tumor that primarily affects young children. It typically arises from developing renal tissue and may grow large before detection. On ultrasound, it usually appears as a large, solid, heterogeneous renal mass that may contain cystic areas or calcifications. Renal vein or inferior vena cava tumor thrombus may occur.

Renal angiomyolipoma

A usually benign renal tumor composed of blood vessels, smooth muscle, and fat. It is associated with tuberous sclerosis in some patients. On ultrasound, it typically appears as a well-defined, hyperechoic mass because of its fat content, although its appearance can vary.

Renal adenoma

A benign epithelial tumor of the kidney that is often small and discovered incidentally. On ultrasound, it may appear as a small solid mass with variable echogenicity. Its appearance can overlap with renal cell carcinoma, so ultrasound alone may not reliably distinguish the two.

Oncocytoma

A generally benign renal tumor arising from specialized renal tubular cells. On ultrasound, it often appears as a solid, well-defined mass with variable echogenicity. A central scar may be present, but imaging cannot reliably distinguish it from renal cell carcinoma.

Renal lipoma

A rare benign tumor composed primarily of mature fat cells. On ultrasound, it may appear as a well-defined, hyperechoic mass, although its appearance depends on its size and composition.

Renal atrophy

A reduction in kidney size caused by chronic disease or loss of functioning renal tissue. On ultrasound, the kidney appears small, often with a thin renal cortex and increased parenchymal echogenicity. The renal sinus may appear relatively prominent compared with the remaining parenchyma.

Acute renal disorders

Conditions that cause a sudden decline in renal function. On ultrasound, the kidneys may be normal in size or enlarged, and the parenchymal echogenicity may increase or decrease depending on the underlying condition. Changes in echogenicity and corticomedullary differentiation are nonspecific and must be interpreted with clinical findings.

Acute glomerulonephritis

Inflammation of the glomeruli that impairs the kidneys' ability to filter blood. On ultrasound, the kidneys may be enlarged with increased cortical echogenicity, although the appearance can be normal or nonspecific.

Acute interstitial nephritis

Inflammation of the renal interstitium, often caused by an allergic reaction to medication or an infection. On ultrasound, the kidneys may be enlarged with increased cortical echogenicity, but findings are nonspecific.

Lupus nephritis

Kidney inflammation caused by systemic lupus erythematosus, an autoimmune disease. On ultrasound, the kidneys may appear enlarged during active inflammation or become small and echogenic with chronic damage.

Sickle cell nephropathy

Kidney damage caused by sickle cell disease, which can impair blood flow and damage renal tissue. On ultrasound, the kidneys may be enlarged early in the disease, while chronic damage may cause changes in renal size and echogenicity. Hematuria may also occur.

Hypertensive nephropathy

Chronic kidney damage caused by uncontrolled high blood pressure. On ultrasound, the kidneys may become small with increased cortical echogenicity and thinning of the renal cortex as the disease progresses.

Papillary necrosis

Destruction of the renal papillae caused by reduced blood supply or ischemic injury. It is associated with conditions such as diabetes, sickle cell disease, and certain medications. On ultrasound, findings may include changes in the renal pyramids and collecting system; sloughed papillae can sometimes cause obstruction.

Acute renal failure (acute kidney injury, AKI)

A sudden decline in kidney function that reduces the kidneys' ability to remove waste and maintain fluid and electrolyte balance. Causes are classified as prerenal, intrinsic renal, or postrenal. On ultrasound, the kidneys may be normal in size or enlarged, and echogenicity may be normal or increased. Ultrasound is also used to assess for urinary obstruction.

Acute tubular necrosis (ATN)

A common cause of intrinsic acute kidney injury involving damage to the epithelial cells lining the renal tubules. It is commonly caused by ischemia or nephrotoxic substances. On ultrasound, the kidneys may be normal in size or enlarged, with increased echogenicity of the renal pyramids and sometimes the cortex. Echogenicity may decrease as renal function recovers.

Chronic kidney disease (CKD)

A progressive loss of kidney function that persists over time and may result from diabetes, hypertension, glomerulonephritis, or other disorders. On ultrasound, the kidneys may become small and echogenic, with cortical thinning and reduced corticomedullary differentiation. Some conditions, such as diabetic kidney disease, may cause enlarged kidneys during earlier stages.

Hydronephrosis

Dilation of the renal collecting system caused by urine accumulation, usually due to urinary tract obstruction. On ultrasound, the renal pelvis and calyces appear dilated and anechoic. Increasing severity can lead to calyceal dilation, cortical thinning, and loss of normal renal parenchyma.

Grade 1 hydronephrosis

Mild dilation of the renal pelvis without significant calyceal dilation. The renal pelvis appears slightly expanded, while the calyces retain their normal shape.

Grade 2 hydronephrosis

Dilation of the renal pelvis and some calyces, with the renal papillae still visible and much of the normal architecture preserved.

Grade 3 hydronephrosis

Moderate to severe dilation of the renal pelvis and calyces, with blunting or rounding of the calyces and progressive loss of normal architecture.

Grade 4 hydronephrosis

Severe dilation of the renal pelvis and calyces with substantial thinning of the renal parenchyma and loss of normal corticomedullary differentiation.

Pyelonephritis

A bacterial infection involving the kidney and renal pelvis. On ultrasound, the kidneys may appear enlarged, with altered parenchymal echogenicity or reduced corticomedullary differentiation. Ultrasound may also appear normal in uncomplicated cases.

Renal abscess

A localized collection of pus within the renal tissue caused by infection. On ultrasound, it may appear as a complex cystic or hypoechoic lesion with internal debris and an irregular wall.

Pyonephrosis

An infected, obstructed collecting system containing pus. On ultrasound, hydronephrosis may be present with internal echoes, debris, or fluid levels within the dilated collecting system.

Emphysematous pyelonephritis

A severe kidney infection caused by gas-forming organisms, commonly associated with diabetes. On ultrasound, gas may appear as bright echogenic foci with dirty posterior acoustic shadowing or reverberation artifacts.

Xanthogranulomatous pyelonephritis

A chronic destructive kidney infection associated with obstruction and often renal calculi. On ultrasound, the kidney may be enlarged and heterogeneous, with areas of altered echogenicity and possible stones or fluid collections.

Nephrocalcinosis

Deposition of calcium within the renal parenchyma, commonly involving the renal pyramids or cortex. On ultrasound, the affected areas appear hyperechoic. Medullary nephrocalcinosis produces echogenic renal pyramids, while cortical nephrocalcinosis produces increased cortical echogenicity.

Renal artery stenosis

Narrowing of a renal artery that reduces blood flow to the kidney and may cause hypertension. On grayscale ultrasound, the kidney may appear small if chronic ischemia is present. Color and spectral Doppler can demonstrate increased flow velocity at the narrowed segment and abnormal downstream waveforms.

Renal infarction

Death of renal tissue caused by interruption of its blood supply, often due to a vascular blockage. On ultrasound, an infarct may appear as a wedge-shaped, hypoechoic or heterogeneous region extending from the renal cortex toward the sinus. Color Doppler typically shows reduced or absent blood flow in the affected area.

Urolithiasis (renal calculi)

Formation of stones within the kidneys or urinary tract. On ultrasound, stones usually appear as hyperechoic foci and may produce posterior acoustic shadowing. Color Doppler may demonstrate a twinkling artifact. Small stones may not produce visible shadowing or hydronephrosis.

Bladder diverticulum

An outpouching of the bladder wall that forms a pocket where urine can collect. On ultrasound, it appears as a fluid-filled structure connected to the bladder by a neck. It may retain urine after voiding.

Bladder tumor

An abnormal growth arising from the bladder wall, most commonly urothelial carcinoma in adults. On ultrasound, it may appear as a solid, often hypoechoic mass projecting into the bladder lumen or as focal wall thickening. Color Doppler may demonstrate internal vascularity.