Pediatric Renal Sonography Lecture Review

A set of vocabulary flashcards covering pediatric renal and adrenal sonography, including pathologies like ARPKD, ADPKD, PUV, and Wilms tumor.

Renal pyramids (medulla, pediatric)

Hypoechoic triangular or rectangular structures commonly mistaken for renal cysts by sonographers unfamiliar with children.

Renal lobulation

Irregular renal outline seen in infants that lessens with age, disappears at ~$6$ months, and should not be evident by ~$1$ year.

Dilation

The process of a structure getting bigger.

Dilatation

The state of already being dilated.

Resistive index (RI) formula

(PSV - EDV)  PSV

Normal renal RI

A value less than $0.7$ (low resistance).

Oligohydramnios

Decreased amniotic fluid; commonly associated with bilateral renal agenesis.

Potter syndrome

Condition associated with renal agenesis, identifiable facial/physical features, and pulmonary hypoplasia.

Potter facies

Features including wrinkly skin, low-set ears, flat nose and chin, and widely separated eyes with epicanthal folds.

Epicanthal folds

Folds in the inner corners of the eyes.

Hydronephrosis

Dilatation of the collecting system of the urinary tract, including renal calyces, renal pelvis, and ureters.

UPJ (ureteropelvic junction)

The most frequent site of obstruction in infants.

Ureterocele

Ballooning of the anterior wall of the ureter into the bladder lumen where the ureter is obstructed at its entry to the bladder.

Duplication of the collecting system

The third most common cause of hydronephrosis; recognized by dilatation of the upper pole calyx and a separate dilated ureter.

Posterior urethral valves (PUV)

Obstructive mucosal flaps or folds of urethral tissue developing in the urethra close to the bladder.

Hypoplasia (renal)

A small but otherwise normal kidney, usually from atrophy secondary to infection or vascular occlusion with infarction.

Dysplasia (renal)

An anatomically abnormal kidney (large or small) associated with urinary tract malformations in $90\%$ of cases.

Pyelectasis

Dilation of the renal pelvis, often seen centrally in unilateral renal dysplasia.

ARPKD

Autosomal recessive polycystic kidney disease, also known as infantile polycystic kidney disease.

ADPKD

Autosomal dominant polycystic kidney disease, also known as adult polycystic kidney disease.

Wilms tumor (nephroblastoma)

The most common malignant renal tumor in the pediatric population.

Neuroblastoma

The most common adrenal tumor of childhood.

Nephrocalcinosis

Deposits of calcium in the kidney, associated with increased urine calcium.

Hydroureteronephrosis

Dilatation of both the ureter and the renal collecting system; a classic finding in posterior urethral valves.

Malaise

A general feeling of discomfort or unwellness; a nonspecific symptom of Wilms tumor.

Prognosis

The expected outcome for the patient moving forward.

Preferred pediatric imaging modality

Sonography, due to no ionizing radiation, no contrast reaction risk, portability, and no sedation needed.

Pediatric renal ultrasound preparation

None required, though hydration is preferred; the patient does not need to be NPO.

Recommended pediatric renal scan planes

Prone longitudinal or transverse, supine, or coronal.

Best transducer for pediatric kidneys

$10\,MHz$ for the best resolution.

Normal newborn renal pyramids

Hypoechoic, triangular or rectangular in appearance.

Obstructed renal pyramids

May be compressed and poorly visualized.

Cortical-sinus echogenic line

A normal finding that separates the superior and inferior poles of the kidney.

Pediatric renal cortex vs. medulla

Pediatric cortex is thin compared to the medulla.

Infant renal sinus

Less fat-filled compared to adults, containing the renal pelvis during infancy.

Distinguishing renal vein from collecting system

Achieved using color and pulsed Doppler.

Normal renal artery waveform

Sharp systolic peak with continuous forward diastolic flow (low resistance).

Abnormal RI of $1.0$

Indicates high resistance in a segmental artery.

Bilateral renal agenesis association

Oligohydramnios and Potter syndrome.

Adrenal glands in renal agenesis

Can be up to $3\,cm$ and lie in the renal fossa where they may be mistaken for kidneys.

Most common infant renal mass

Congenital hydronephrosis, frequently diagnosed in utero.

Second most common cause of hydronephrosis

Distal ureteral obstruction.

Bilateral hydronephrosis obstruction site

Distally, located in the bladder or urethra.

Causes of non-obstructive hydronephrosis

Reflux, which accounts for up to $14\%$ of cases.

Onen Grade 1

Renal pelvic dilation alone; AP diameter is not important.

Onen Grade 2

Pelvis and caliceal dilation with normal renal parenchyma ($>7\,mm$).

Onen Grade 3

Pelvis and caliceal dilation where the medulla is short and thin, but cortex and differentiation are normal.

Onen Grade 4

Pelvis and caliceal dilation with total loss of medulla, thin cortex, and no corticomedullary differentiation.

AP diameter in Onen grading

Not important in any of the grades.

PUV prevalence in hydronephrosis

Responsible for $10\%$ of hydronephrosis cases.

Most common cause of urethral obstruction in boys

Posterior urethral valves.

Incidence of PUV

$1$ in up to $8,000$ boys.

Sonographic appearance of PUV

Bilateral hydroureteronephrosis with parenchymal thinning.

Renal dysplasia malformation association

Occurs in $90\%$ of cases, usually involving obstruction.

Unilateral renal dysplasia secondary to PUJ obstruction

Echogenic kidney with small peripheral renal cysts and central pyelectasis.

ARPKD presentation at birth

Symmetrically enlarged bilateral kidneys.

Echogenic pyramids in ARPKD

The result of multiple bright echoes from microscopic tubular dilatation of cysts.

Renal enlargement in ARPKD

Affects the medullary portion, stretching the calyces and renal pelvis.

ADPKD cyst size in neonates

$0.1$ to $5\,mm$, making them difficult to visualize.

Primary neonate sonographic finding of ADPKD

Renal enlargement.

ADPKD family history frequency

There is a $75\%$ chance other family members have the disease.

ARPKD lateralization

Bilateral and symmetric.

ADPKD lateralization

May affect one or both kidneys.

Most common solid abdominal tumor in children

Wilms tumor, followed by neuroblastoma.

Clinical presentation of Wilms tumor

Palpable mass, pain, fever, malaise, weight loss, hematuria, or hypertension.

Peak age for Wilms tumor

$3$ to $4$ years.

Wilms tumor vascular extension

Invades the renal vein and IVC; may extend into the heart.

Wilms tumor metastasis

Commonly spreads to the liver and lung.

Sonographic appearance of nephrocalcinosis

Focal echogenicity of renal pyramids with or without shadowing and loss of corticomedullary junction.

Right adrenal imaging success rate

$97\%$ in children.

Left adrenal imaging success rate

$83\%$ in children.

Ease of imagine pediatric adrenals

Due to relatively larger glands, decreased perirenal fat, and proximity to the skin.

Adrenal vs. renal mass differentiation

Presence of an interface or demarcation between the mass and kidney indicates an adrenal mass.

Neuroblastoma onset (first year)

$50\%$ of cases appear in the first year of life.

Sonographic appearance of neuroblastoma

Predominantly echogenic with poorly defined borders; not as "clean" as Wilms tumor.