renal pathology

Acute renal failure (ARF)

• a sudden decrease in renal function

• Marked by an increase in serum creatinine or blood urea nitrogen

What is the most common cause of ARF?

Tubular necrosis

sonographic findings of ARF:

the kidneys may appear normal in the early stages of disease or the cortex may appear hyperechoic

chronic renal failure (CRF)

• a gradual decrease in renal function and leads to end stage renal disease

• pts are typically placed on dialysis or a donor kidney may be needed

what is the most common cause of CRF?

diabetes mellitus

sonographic findings of CRF:

the kidneys will appear small, echogenic, may contain cysts and there may be loss of normal corticomedullary differentiation

hydronephrosis (pyelocaliectasis)

dilation of the renal collecting system secondary to the obstruction of normal urine flow

causes of hydronephrosis:

• urolithiasis

• neoplasm

• ureteropelvic junction obstruction

• retroperitoneal fibrosis

• pregnancy

• reflux

mild hydronephrosis

notes as distention of the renal pelvis

moderate hydronephrosis

further progression of distention into the calyces and medullary pyramids

severe hydronephrosis

extends into the cortex and causes severe thinning of the parenchyma

sonographic findings of hydronephrosis:

will appear as anechoic fluid filling all or part of the renal collecting system

urolithiasis

• kidney stones located anywhere within the urinary tract

• stones can form in the kidney or bladder

• can pass into the collecting system or ureter and cause obstruction

in urolithiasis, what are the stones often made of?

calcium oxalate and are more frequently found in males

clinical findings of urolithiasis:

• hematuria

• renal colic

• oliguria

• may lead to UTI

what are the 3 common areas of obstruction by a stone?

• ureterovesical junction (most common)

• ureteropelvic junction

• pelvic brim where the ureter crosses the iliac vessels

staghorn calculus

a stone that completely fills and takes on the shape of the renal pelvis

sonographic findings of urolithiasis:

• stone is echogenic and produces posterior acoustic shadowing

• “twinkle sign/artifact” will be noted with color doppler signal posterior to stone

• hydronephrosis and dilatation of the ureter may be present

simple renal cyst

• most common renal mass

• occurs in 50% of ppl over the age of 50

• most are simple cortical cysts

sonographic findings of simple renal cysts:

anechoic mass that is spherical, has smooth walls, posterior acoustic enhancement and no internal echoes

clinical symptoms of simple renal cysts:

typically asymptomatic and clinically insignificant

parapelvic cyst

originates in the renal parenchyma and protrudes into the renal sinus

peripelvic cyst

originates within the renal sinus and has a lymphatic origin

small cortical cyst

located within the cortex

complex renal cyst

the cyst will have septations, internal debris, mural nodules, papillary projection or irregular borders and are more worrisome for malignancy

autosomal dominant polycystic kidney disease (ADPKD)/adult polycystic kidney disease (APKD)

• pt will develop bilateral renal enlargement due to the development of numerous cortical cysts of varying sizes

• latent for years, not manifesting in clinical symptoms until the pt is older

clinical symptoms of ADPKD:

• HTN

• decreased renal function

• UTI

• renal calculi

• flank pain

• hematuria

sonographic findings of ADPKD:

the kidneys will appear enlarged and contain numerous renal cysts with possible cysts identified in the pancreas, liver and/or spleen

autosomal recessive polycystic kidney disease (ARPKD)/infantile polycystic kidney disease

may be detected in utero with oligoydramnios

sonographic findings of ARPKD:

bilateral, enlarged, echogenic kidneys with a loss or corticomedullary differentiation

acquired renal cystic disease

• development of multiple cysts is often the result of long-term hemodialysis

• associated with an increased incidence of renal cell carcinoma

sonographic findings of acquired renal cystic disease:

the kidneys will appear small with the development of some small cysts

glomerulonephritis

• an inflammatory response resulting in glomerular damage caused by an autoimmune reaction, infection and exposure to toxins

• can lead to ESRD

clinical symptoms of glomerulonephritis:

• fever

• proteinuria

• hematuria

• HTN

sonographic findings of glomerulonephritis:

appears as a decrease in renal size and an increase in the cortical echogenicity

acute pyelonephritis

• inflammation of the kidneys

• may be focal (multifocal) or diffuse

most renal infections occur via:

an ascending route from the bladder and they are usually caused by E. coli

sonographic findings of acute pyelonephritis:

• pt may not have any sonographic abnormalities

• renal enlargement

• hypoechoic parenchyma

• absence of sinus echoes

complications of acute pyelonephritis:

• renal abscess

• pyonephrosis

• emphysematous pyelonephritis

• chronic pyelonephritis

pyonephrosis

purulent material (pus) in the dilated collection system of the kidney associated with an infection secondary to renal obstruction

sonographic findings of pyonephrosis:

hyperechoic debris in a dilated renal collecting system

nephrocalcinosis

an accumulation of calcium within the renal parenchyma

what are the 2 forms of nephrocalcinosis?

• medullary nephrocalcinosis (most common)

• cortical nephrocalcinosis

medullary nephrocalcinosis

• may be caused by hypercalcemia

• most common cause is a congenital defect known as medullary sponge kidney

medullary sponge kidney

the accumulation of calcium within abnormally dilated collecting ducts located within the medulla

sonographic findings of medullary nephrocalcinosis:

echogenic renal medulla

sonographic findings of cortical nephrocalcinosis:

echogenic foci within the cortex

renal artery stenosis

a decrease in the diameter of the renal arteries

what is a common cause of renal artery stenosis in older patients?

atherosclerosis

clinical symptoms of renal artery stenosis:

• sudden onset of HTN

• uncontrollable HTN

• fibromuscular disease account for 2/3 of renal artery stenosis cases in young pts

angiomyolipoma

• the most common benign renal tumor that consists of a network of blood vessels, muscle and fat

• unilateral and asymptomatic

• 80% involve the R kidney

sonographic findings of an angiomyolipoma:

solid, echogenic mass

oncocytoma

• usually occur in middle to old age

• range from 0.3-26 cm in diameter

sonographic findings of an oncocytoma:

well-defined, smooth and homogeneous (similar to RCC)

renal cell carcinoma (RCC)

• AKA hypernephroma or adenocarcinoma of the kidney

• the most common primary malignant tumor of the kidney

• typically it is unilateral

clinical symptoms of RCC:

• painless hematuria (most common)

• flank pain

• palpable mass

sonographic findings of RCC:

• hyperechoic relative to the normal adjacent renal parenchyma and may be isoechoic to normal renal tissue

• renal vein thrombosis or tumor extension into the renal veins and IVC