Kidney Cystic Masses and PKD Overview

Kidney Cystic Masses

• Polycystic kidney disease (PKD) is a breakdown of cystic masses. Different types include ADPKD (Autosomal Dominant Polycystic Kidney Disease), ARPKD (Autosomal Recessive Polycystic Kidney Disease), and Multicystic Dysplastic Kidney (MCDK).

ADPKD

• Inherited (10% spontaneous mutations)
• Usually diagnosed in the 4th decade
• Bilateral renal enlargement due to multiple cysts of varying sizes
• Cysts in other organs including liver (50%), pancreas (10%), and spleen.
• Tissue destruction can lead to renal failure and hypertension.
• Complications include infection, renal calculi (kidney stones), cyst rupture, hemorrhage and urethral obstruction.
• Associated with arterial aneurisms, especially cerebral arterial berry aneurysms.

ARPKD

• Previously known as infantile PKD
• Usually apparent at birth
• Multiple small cysts throughout kidneys from cystic dilation of collecting tubules due to hyperplasia of the interstitial portions of ducts.
• Associated with oligohydramnios (reduced amniotic fluid), pulmonary hypoplasia, hepatic fibrosis, and portal hypertension during development.

MCDK

• Most common cause of abdominal mass in newborns
• A form of renal dysplasia
• Multiple non-communicating cysts with absence of renal parenchyma.
• Results in renal atresia and ureteropelvic junction during development.
• Commonly unilateral but can be bilateral (20%).
• Contralateral kidney shows compensatory hypertrophy.
• May increase in size or undergo spontaneous involution.
• Associated with urinary malformations and non-renal malformations

Medullary Cystic Disease

• Medullary sponge kidney caused by congenital cystic dilatation of the medullary pyramids.
• Ectatic collecting tubules can be seen on excretory urography (imaging of the kidney that uses contrast to evaluate the urinary pathways).
• Urinary stasis followed by calcium deposits in dilated tubules.
• Sonographic findings show bilateral hyperechoic medullary pyramids with or without shadowing.

Simple or Complex Renal Cysts

• Simple renal cysts are common (occurring in close to 50% of people over 50 years of age).
• Most are simple fluid-filled cysts, often arising from the renal cortex.
• Vary in size (from 1 mm to 10 cm).
• Sonography can't differentiate benign cysts from malignant cysts.

Simple Renal Cyst Criteria:

• No internal echoes
• Acoustic enhancement
• Sharply defines thin walls
• Round or oval shapes

Complex Renal Cysts

• These are atypical cysts that lack the characteristics of simple cysts.
• Types include hemorrhagic, infected/inflammatory, septate/multilocular cysts
• Possible septations (thin walls) or minimal calcifications
• May contain internal echoes or have lobulated shapes

Parapelvic/Peripelvic Cysts

• Located in the renal sinus (center) of the kidney
• Often asymptomatic, but can be associated with hematuria or hypertension.
• Anechoic cysts that are solitary, larger, and well-defined with through transmission
• Can be misidentified as renal pelvis dilatation.

Acquired Cystic Disease

• Multiple cysts develop in chronically failed kidneys due to long-term dialysis.
• Possible hemorrhage within the cysts causing pain and hematuria.
• High risk for renal cell carcinoma in patients with renal dialysis.

Von Hippel-Lindau Disease

• Inherited disease.
• Usually diagnosed in the 2nd or 3rd decade.
• Patients experience visual impairment
• Related tumors to watch out for include renal cell carcinoma, pheochromocytomas, islet cell tumors, and renal and pancreatic cysts

Tuberous Sclerosis

• Multi-system genetic disease
• Presents with symptoms like seizures, mental retardation, and facial angiofibromas.
• Increased incidence of renal cysts and angiomyolipomas (primarily in bilateral locations).
• Angiomyolipomas are typically bilateral in individuals with tuberous sclerosis

Solid Renal Masses/Neoplasms

• Benign neoplasms (tumors): Adenoma, oncocytoma, angiomyolipoma (AML)
• Malignant neoplasms (tumors): RCC (Renal cell carcinoma), Wilms tumor, mesoblastic nephroma, urothelial carcinoma
• Metastatic renal tumors: Lymphoma

Renal Oncocytomas

• A type of relatively benign kidney tumor.
• Imaging characteristics overlap with RCC, making differentiation challenging.
• A central scar or spoke wheel pattern of vessels on CT/MRI scans can be suggestive of an oncocytoma.

Angiomyolipoma

• A benign renal tumor composed of varying proportions of mesenchymal cells, fat, and smooth muscle cells.
• Characterized by significant echogenicity greater than or equal to that of the renal sinus.
• A propagation speed artifact causing posterior displacement of structures due to slower acoustic velocity in fatty masses is possible.
• CT confirmation of fat within an echogenic renal mass supports diagnosis

Other Benign Renal Tumors

• Liposarcoma
• Leiomyoma
• Juxtaglomerular (reninoma) tumor
• Hemangioma
• Fibroma
• Multilocular cystic nephroma

Renal Cell Carcinoma (RCC)

• Also known as hypernephroma or adenocarcinoma
• Most common solid renal mass in adults
• Common location is in the kidney.
• Can be encapsulated and often unilateral.
• More common in males.
• Common signs include hematuria, pain and palpable mass.

Wilms Tumor (Nephroblastoma)

• Most common childhood kidney tumor-
• Typically appears as a large, asymptomatic flank mass in children under 3.5 years of age
• Metastasis is possible to lungs, liver, bone, lymph nodes, and retroperitoneum
• Differentiation from adrenal neuroblastoma important, as contour of the kidney can be a helpful characteristic to distinguish these two.

Mesoblastic Nephroma

• Most common renal tumor in newborns and infants
• Diagnosed prenatally using ultrasound
• Early descriptions portrayed as a benign tumor. Later studies propose a spectrum of diseases exists, with a typical less aggressive type and a less common more aggressive type.
• Differentiation from Wilms tumor may be difficult using sonography

Urothelial Carcinoma

• Malignant tumors that line the renal pelvis, calyces, ureter, and bladder.
• Transitional cell carcinoma is the most common form.
• Squamous cell carcinoma accounts for about 10% of urothelial carcinomas.
• Common clinical presentation is hematuria.

Metastatic Renal Tumors

• Renal parenchyma can be a site for secondary tumors from primary organs like lung, breast, and colon
• Malignant cells from leukemia and lymphoma can also metastasize to kidneys.
• Sonographic findings include hypoechoic masses or diffusely enlarged inhomogeneous kidneys

Hydronephrosis

• Dilatation of the renal collecting system (i.e. calices or renal pelvis).
• Can be due to obstructions or problems with the urinary tract
• Causes vary based on whether the obstruction is intrinsic or extrinsic. Intrinsic obstructions can be due to kidney stones (calculi), ureteropelvic junction (UPJ) obstructions, or tumors. Extrinsic causes include tumors, trauma, or problems with the bladder, or pregnancy.
• Grades of hydronephrosis range from mild to severe determined by the severity of the dilation.
• Diagnosis can be made using ultrasonography or renal scan.

Urolithiasis

• Kidney stones in various forms such as calcium, uric acid, struvite or magnesium ammonium phosphate, and cysteine.
• Symptoms include flank pain, urinary blood (hematuria).
• Localized in the kidney often highly reflective, which can make them hard to visualize.

Nephrocalcinosis

• Calcium deposits inside the renal parenchyma, either cortical or medullary.
• Calcium levels are elevated, as this condition is usually related to metabolic abnormalities resulting in hypercalcemia.
• Usually appears bilateral and diffuse with sonographic findings.

Renal Trauma

• Blunt trauma is the most common type of injury (often during sporting events or motor vehicle accidents).
• Penetrating trauma is less common and more serious (often due to gunshot or stab wounds).
• Causes include sports, motor vehicle accidents, and workplace injuries.
• Hematomas, renal contusions or fractures as usual findings.
• Ultrasound and computed tomography (CT) are common diagnostic methods.

Renal Infarction

• Caused by blood supply interruption to the kidney's vascular system.
• Occurs as a result of arterial embolism, occlusion, or stenosis.
• Initial sonographic findings show hypoechoic area of compromised tissue.
• Over time the hypoechoic area becomes echogenic.

Renal Infections

• Acute Pyelonephritis (APN) is inflammation/ infection in renal parenchyma due to bacterial invasion that travels through the lower urinary tract
• Emphysematous Pyelonephritis (EPN)
• Chronic Atrophic Pyelonephritis (CPN)
• Xanthogranulomatous Pyelonephritis (XGP)
• Pyonephrosis
• Fungal Infections
• Schistosomiasis
• Tuberculosis (TB)
• Malakoplakia

Acute Kidney Injury (AKI)

• Characterized by a sudden reduction in kidney function.
• Prerenal (inadequate perfusion)
• Intrinsic (acute tubular necrosis, acute glomerulonephritis, nephrotoxins)
• Postrenal (obstructive nephropathy)
• Diagnostic method includes urine and other bodily fluids. Imaging can be helpful to see if hydronephrosis is present.

Chronic Kidney Disease (CKD)

• Progressive loss of kidney function over months or years
• Many different causes leading to permanent damage. Various conditions result in permanent damage to the nephrons causing reduced glomerular filtration rate (GFR)
• Diagnosis may involve imaging studies

This quiz explores the different types of cystic kidney diseases including ADPKD and ARPKD. It covers their characteristics, complications, and associated conditions. Test your understanding of these kidney disorders and their implications.