Pedriatic radiology

Genitourinary tract

 

Radiology plays an important role in the evaluation of abnormalities of the genitourinary tract in infants and children. There are a number of modalities, both noninvasive and invasive techniques for evaluating the adrenal glands, kidneys, ureters, bladder, urethra, gonads, and genitalia.

Modalities

Ultrasound
Ultrasound (US) is a particularly useful imaging modality for the pediatric patient as it does not utilize radiation and is diagnostically accurate.

Figure 43. Normal neonatal renal sonography. 7-day-old infant. The renal contours are irregular due to fetal lobulation. The medullary pyramids are hypoechoic and prominent. These normal, triangular pyramids should not be confused with cysts or hydronephrosis.

The renal parenchyma is well demonstrated by US. Dilatation of the renal pelvis is readily apparent. The bladder should be evaluated when distended; a dilated distal ureter is well seen at its entrance into the bladder. US is extremely operator dependent; another drawback is the lack of information regarding renal function. The renal papillae in the neonatal period are prominent and hypoechoic (Fig. 43); their triangular shape differentiates them from cystic disease of the kidney or hydronephrosis.

Excretory urography
Excretory urography (intravenous pyelography) is performed after injecting 2-3 ml/kg body weight of water-soluble contrast media intravenously. Most pediatric radiologists prefer to use non-ionic contrast material; there is less pain with injection and if extravasation occurs, pain and tissue damage are significantly less than with ionic contrast media. A preliminary film is always obtained. A coned-down AP film of the kidneys is obtained approximately 1-2 minutes after injection (Fig. 44 a); a prone P A film is then obtained at 7-10 minutes to show both kidneys and bladder (Fig. 44 b ).Cleansing enema may be needed to improve the quality of the examination. Fasting and fluid restriction should be avoided.

Voiding cystourethrography
Voiding cystourethrography (VCUG) demonstrates the anatomy of the bladder and urethra as well as the presence or absence of vesicoureteral reflux (VUR). The urethra is catheterized and dilute contrast media is instilled into the bladder. Because gonadal radiation dosage is relatively high, fluoroscopy should be brief and intermittent. Spot films are obtained of the bladder with low-volume filling and after complete filling.

a	Figure 44.Normal excretory urogram. a) 1-minute film. There is good visualization of the contours of the renal parenchyma (arrowheads). Some contrast already present in the pelvicalyceal systems. b) 10-minute film. The stomach is distended by carbonated beverage. The kidneys, renal pelves, and proximal ureters are well visualized.
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Both oblique projections visualize the region of the ureterovesical junctions for any reflux or abnormality. During voiding, the male urethra is visualized in the oblique projection whereas the female urethra is visualized in the lateral or oblique projection. The bladder should again be evaluated in the supine position at the end stage of voiding. The absence of vesicoureteral reflux should be documented with spot films of the kidneys at the end of the study. If reflux is present, the level and amount of associated distention should be documented.

Nuclear medicine
Isotope cystography correlates well with conventional VCUG for assessing the presence and degree of vesicoureteral reflux (VUR). The low cost and low radiation dose make it an ideal method for studies in females with urinary tract infection and for follow-up studies in patients with known VUR. Conventional VCUG is still preferred as the initial imaging procedure in males and in females with suspected anatomic abnormalities.

Renal scintigraphy is able to assess a variety of physiologic parameters: differential renal function, renal plasma flow, glomerular filtration and renal clearance. Renal cortical scanning agents are particularly useful in studying renal morphology; they can localize small amounts of renal parenchyma, diagnose acute pyelonephritis, and identify malpositioned kidneys.

CT
CT is most frequently performed after initial investigation of the kidneys by US or excretory urography. Intravenous sedation may be required up to 7 years of age. Intravenous contrast injection is mandatory. CT is particularly helpful in the evaluation of retroperitoneal tumors (Wilms, neuroblastoma, rhabdomyosarcoma) and evaluating patients with renal trauma.

MRI
Since MRI uses no ionizing radiation, it is particularly well suited for pediatric imaging. Images may be obtained in the axial, sagittal, coronal, and other orthogonal planes. Because of sensitivity to any motion, children frequently require intravenous sedation or general anesthesia.
MRI is helpful in evaluating large abdominal masses since the coronal and sagittal planes gives a global view of the abnormality (See Fig. 54). MRI has also been exceedingly valuable in the evaluation of neuroblastoma. The inability of MRI to detect calcification is outweighed by its ability to image in orthogonal planes, assess extradural tumor extension, and determine bone marrow involvement.

Angiography
With the emergence of less invasive imaging modalities, there has been a dramatic change in the indications for pediatric angiography. The most common clinical indication for renal angiography is evaluation of renovascular hypertension. Transluminal angioplasty is able to treat renal artery stenosis.

CT is the initial method of evaluating renal trauma in children. However, renal angiography may be indicated to further evaluate a renal vascular pedicle injury, false aneurysm, or arteriovenous fistula.

Renal abnormalities

Congenital

Renal ectopia and horseshoe kidney
Renal ectopia is an abnormal position of a kidney. It may be due to failure of complete ascent of the kidney from its primitive location at the S1-2 level or to excessive cranial migration beyond its normal location. Crossed renal ectopia is a condition in which the affected kidney is located entirely or primarily on the opposite side of the abdomen. The ectopic kidney lies below the normal contralateral kidney, and the two organs are almost always fused.

Renal fusion is the union of two kidneys. Horseshoe kidney is the most common type of renal fusion. There is fusion of the lower pole of the two kidneys across the midline by an isthmus, which usually lies anterior to the aorta and inferior vena cava. The diagnosis may be made by excretory urography or US. Complications associated with horseshoe kidney include hydronephrosis and renal stones. There is also an increased incidence of Wilms tumor, renovascular hypertension, and adenocarcinoma in patients with horseshoe kidney.

Renal cystic disease
Cystic disease of the kidneys is a complex topic. Classifications are usually based on proposed etiology, pathology, anatomic location, or radiologic features.

Polycystic kidney disease
Infantile polycystic kidney disease (IPCKD) is a spectrum of abnormalities that includes both microcystic and macrocystic renal disease with variable degrees of hepatic fibrosis. IPCKD is inherited as an autosomal recessive trait. Patients present in the first several months of life with palpable kidneys and variable degrees of renal failure. There is renal enlargement with diffuse increased echogenicity of the kidneys by US.
Juvenile polycystic disease of kidney and liver (renal tubular ectasia with congenital hepatic fibrosis) is also inherited as an autosomal recessive trait; patients usually develop symptoms after 10 years of age. There is hepatosplenomegaly and portal hypertension. F ewer than 10% of renal tubules are dilated and hyperplastic; there is gross hepatic fibrosis.

Figure 45. Multicystic dysplastic kidney. Longitudinal sonography demonstrates multiple cysts of varying sizes in the kidney. There is no renal pelvis identified. The multiple cysts do not intercommunicate and there is no identifiable renal parenchyma.

Adult polycystic kidney disease (APCKD) is an autosomal dominant trait with variable penetrance. It is felt to be a separate entity from IPCKD. The cysts are of variable size and involve both renal cortex and medulla; hepatic cysts occur in approximately 1/3 of patients, but there is usually no periportal fibrosis. APCKD usually presents in early adulthood with hypertension, hematuria, or renal failure.

Multicystic dysplastic kidney
Multicystic dysplastic kidney (MCDK) is the second most common abdominal mass in the neonate. The central embryonic event in the formation of MCDK is ureteropelvic atresia during the metanephric stage of intrauterine development.
DS demonstrates multiple cysts of varying size; the largest of these cysts is not central and does not represent a dilated renal pelvis (Fig. 45).
Renal scintigraphy confirms markedly decreased perfusion and absent or markedly decreased renal function. Because many of the cysts decrease in size, MCDK may completely involute; patients are usually treated conservatively. Surgical removal is only indicated if the cysts markedly enlarge or if hypertension develops.

Simple renal cyst
Prior to the use of DS, simple renal cysts were rarely diagnosed in children. A simple renal cyst is unilocular, solitary, and contains a single layer of flattened epithelium with a fibrous wall. There is no communication between the cyst cavity and the renal collecting system. Although percutaneous needle puncture may be performed, sequential DS is

Figure 46. Hydronephrosis due to UPJ obstruction. Excretory urography shows that there is almost complete obstruction at the left ureteropelvic junction. The right kidney and bladder are normal. suggested as the method of choice for follow-up.

Multilocular cyst
A multilocular renal cyst (multilocular cystic nephroma) is a unilateral and solitary benign lesion of the kidney. US shows multiple cysts with intervening thin and linear septa. Foci of nephroblastomatosis or Wilms tumor may be found in the walls of multilocular cysts; such masses usually have thickened as well as irregular septa and should be considered a well-differentiated Wilms tumor of the kidney. The usual treatment for multilocular renal cyst is nephrectomy.

Ureteropelvic junction obstruction
Congenital ureteropelvic junction (UPJ) obstruction is the most common congenital obstruction of the urinary tract. There is an intrinsic narrowing of the UPJ that causes hydronephrosis (Fig.46).

Figure 47.Primary megaureter. Excretory urography demonstrates a dilated right ureter to a level just above the bladder. The right renal pelvis and ureter are markedly dilated.

If the obstruction is mild, intermittent hydronephrosis may only be manifest with diuresis.

Sonography of UPJ obstruction shows a large cystic mass within the kidney. There are multiple hypoechoic cystic spaces, with the largest being medial in location and representing the dilated renal pelvis. The cysts intercommunicate, and one can usually identify infundibulae and calyces as well as surrounding renal parenchyma. There is no evidence of ureteral dilatation; the bladder is normal. All patients with suspected UPJ obstruction should have a voiding cystourethrogram to exclude reflux. Moreover, some patients may have UPJ obstruction associated with reflux.

Excretory urography shows delayed excretion of contrast medium, which is diluted by retained urine within the large renal pelvis. Nuclear scintigraphy with DTPA shows a photon-deficient area due to the dilated renal collecting system; there is central migration of isotope into the renal pelvis on delayed images. If renal function is markedly decreased, scintigraphy will be helpful in identifying the amount of functioning renal parenchyma.

Primary megaureter is a functional obstruction of the distal ureter. It may be isolated (Fig. 47) or associated with reflux and other urinary tract abnormalities.

a	Figure 48.Ectopic ureter. 2-year-old female with urinary tract infection. a) Transverse sonography of the bladder demonstrates a dilated right ureter (arrows). b) Excretory urography. There is a duplex system on the right. The upper pole moiety (arrow) is dilated and poorly functioning. c) Voiding cystourethrography. There is reflux into the dilated ureter (lower arrows) and dilated upper pole moiety (upper arrows).
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Ectopic ureter
Failure of the ureter to separate from the wolfian duct results in the ureteral orifice being carried to some point distal to its normal location. The result is ureteral ectopia, which is 3-4 times more frequent in females than in males. In females, this anomaly is usually present with an associated duplex system, so that the ureter draining the upper pole moiety terminates ectopically. The ectopic orifice in the female empties into the urethra, vestibule, or vagina (Fig. 48 a). Rarely, it may empty in the uterus, cervix, or rectum. In males, ectopic ureters less likely involve duplex systems. Ectopic ureteral openings may be in the posterior urethra, ejaculatory ducts, seminal vesicle, vas deferens, or rectum. A common

Figure 49.Ectopic ureterocele. Excretory urography shows a large ureterocele (arrowheads) in the bladder. There is a duplex collecting system of the left kidney. The right ureter and lower pole moiety of the right kidney are displaced laterally. The upper pole moiety of the right kidney (*) is non-functioning.

clinical presentation in females is urinary incontinence or dribbling; since the ectopic opening lies proximal to the external sphincter in males, there usually is not incontinence.

Excretory urography may suggest the diagnosis by directly visualizing the termination of the ectopic ureter, verifying the presence of a non-functioning upper pole renal moiety, or demonstrating a non-functioning kidney (Fig. 48 b). A cyclic VCUG may be helpful in filling ectopic ureters that drain into the urethra (Fig. 48 c).

Ectopic ureterocele
A ureterocele is a cyst-like protrusion into the bladder lumen of a dilated distal portion of an ectopic ureter. It is almost invariably associated with duplication, obstruction of the ureter, and drainage of the upper pole renal moiety. An ectopic ureterocele is larger and more inferior than a simple ureterocele, is usually unilateral, and is far more common (4: 1) in females than in males.

The sonographic appearance of the ectopic ureterocele is characteristic. There is a dilated upper renal collecting system which connects with a dilated, tortuous ureter. A round thin-walled, intravesical ureterocele is seen within the bladder. Excretory urography shows a mass in the upper pole of the affected kidney due to the dilated, hydronephrotic upper pole moiety as well as a lucent filling defect in the bladder due to the ectopic ureterocele filled with urine within the contrast-filled bladder (Fig. 49).

VCUG may not demonstrate an ectopic ureterocele, as contrast material is highly radiopaque and filling may flatten the ureterocele or even evert it if it is not tense. When VCUG is performed for suspected ectopic ureterocele, it is important to use dilute contrast material in very small amounts. Fluoroscopy should be performed in varying degrees of obliquity.

Urinary tract infection

Urinary tract infection (UTI) is the most common abnormality of the urinary tract in children and the second most common infection in the pediatric age group, exceeded only by upper respiratory tract infection. Not only is UTI exceedingly common in children it is also potentially dangerous. This danger is due to difficulties and delays in diagnosis, high relapse rate following treatment, and potential for renal damage leading to chronic renal disease.

There is increasing evidence that first-time UTI in both males and females should be evaluated. The purpose of this imaging evaluation is to diagnose congenital physiologic abnormalities, identify renal damage, provide a baseline for subsequent evaluation of renal growth, and establish the prognosis.

The traditional imaging approach has been VCUG (Fig. 50) followed by excretory urography. More recently there is a trend toward utilizing nuclear cystograms to replace radiographic VCUG, particularly in females or for follow-up examinations, and US for evaluation of the upper urinary tract.

There is increasing utilization of cortical scintigraphic agents (DM SA, glucoheptonate) to evaluate the kidneys for renal scarring and acute pyelonephritis. These techniques are more sensitive than US or excretory urography for the detection of subtle scars and changes of acute pyelonephritis.

Lower urinary tract abnormalities

Neurogenic bladder
Spinal dysraphism is the most common cause of neurogenic bladder in children. Other causes include trauma, childhood viral diseases, and previous pelvic surgery. The basic pathophysiology of neurogenic bladder is functional abnormality of the sphincter mechanism of the urethra. There is disordered contractility of the detrusor muscle with subsequent

Figure 50.Vesicoureteral reflux. Voiding cystography shows marked left vesicoureteral reflux (Grade III) and moderate (Grade II) right reflux.

inadequate bladder emptying and retention of urine within the bladder.

A neurogenic bladder may be small, normal, or large in volume. Usually, the bladder is small with a thick vesical wall and many cellules, sacules, and even diverticula. There is incompetence of the bladder base at rest and poor relaxation of the external sphincter during attempted voiding. US examination demonstrates a thick-walled bladder and any associated upper urinary tract dilatation.

Posterior urethral valves
Posterior urethral valves are the most common cause of urethral obstruction in the male infant, child, or adolescent. Diagnosis should be made as early as possible in order to prevent renal damage. If the margins of the normal mucosal folds (plicae collicularis) fuse anteriorly, obstructing posterior urethral valves are formed.

US may confirm the presence of bilateral hydronephrosis and ureterectasis. Examination of the pelvis shows dilated ureters and a thick-walled dilated bladder. Careful examination of the posterior urethra using the distended bladder as a window may demonstrate dilatation that is accentuated by manual compression. However, VCUG remains the method of choice for confirming the diagnosis (Fig. 51). The bladder is frequently thickened and markedly trabeculated. There may be vesicoureteral reflux, which is usually unilateral, and even extravasation of contrast material or urine into the peritoneal cavity from the kidney or bladder,

Figure 51. Posterior urethral valves. Newborn male with bilateral hydronephrosis detected on prenatal sonography. Voiding cystourethrography demonstrates rounded obstruction due to posterior urethral valves (arrow), markedly dilated posterior urethra (U), small and thick-walled bladder (B), and reflux into the utricle (*) as well as tortuous ureters.

producing urinary ascites. The urethra should be examined in the steep oblique or lateral projection during voiding. There is frequently secondary thickening of the bladder neck and wall of the bladder. The posterior urethra is dilated with the obstructing posterior urethral valve producing a "spinnaker sail" appearance (Fig. 51).

Exstrophy of the bladder
Exstrophy is a failure of closure of the anterior wall of the bladder. With exstrophy of the bladder, there is widening of the symphysis pubis due to outward rotation of the iliac bones, outward rotation of the pubic bones, and lateral displacement of the iliac bones (Fig. 52). There are usually no malformations of the upper urinary tracts. Initial renal US should be performed as a baseline at 1-2 weeks of age. There is usually slight dilatation of the distal ureters which should not be interpreted as a sign of significant obstruction.

Genitourinary tumors

Wilms tumor
Wilms tumor (nephroblastoma) is a triphasic, embryonic neoplasm that contains epithelial, blastemal, and stromal elements. It is similar in overall incidence to neuroblastoma and accounts for approximately 8 % of all pediatric malignant tumors. Wilms tumor is the most common solid

Figure 52. Exstrophy of bladder. AP view of the pelvis during excretory urography. There is marked widening of the symphysis pubis. The kidneys are normal. Due to surgical reconstruction, the bladder is small in capacity.

abdominal mass as well as the most common renal malignancy of childhood.

The peak incidence of Wilms tumor is between 30 months and 3 years of age; 78 % of all cases are detected between 1 and 5 years of age. The most common clinical presentation is that of an asymptomatic abdominal mass. Other infrequent clinical presentations include abdominal pain, fever, anorexia, hematuria, and hypertension.

Wilms tumor is bulky and replaces most of the involved kidney; the tumor arises in the renal parenchyma and displaces as well as distorts the pelvicalyceal system. The tumor is usually solid with a prominent pseudocapsule that separates it from normal renal parenchyma. Wilms tumor may infiltrate the capsule or invade the renal vein and inferior vena cava; there are frequently local metastases to retroperitoneal lymph nodes. There may be local extension of tumor, venous extension, lymphatic metastases, or urothelial spread. The two major pathological tumor types are favourable histology (no anaplasia, nonsarcomatous) and unfavourable histology (anapiasia, sarcomatous).

The screening modality of choice in pediatric patients with a palpable abdominal mass is US. Wilms tumor is an intrarenal, echogenic mass (Fig. 53 a); tumor echogenicity is usually equal to or slightly greater than that of adjacent liver and more homogeneous than the echogenicity of neuroblastoma. There may be hypoechoic areas within the tumor that

a	Figure 53.Wilms tumor. 1-year-old female with left abdominal mass. a) US. Longitudinal ultrasonography shows a large, echogenic mass (M) within the left kidney. b) CT. Left renal mass (M) distorts the normal kidney (arrow). Low attenuation areas within the tumor mass are due to necrosis. The right kidney and inferior vena cava are normal. e) Abdominal radiograph after CT. There is a large, intrarenal mass (M) that stretches and distorts the calyces. [From Kirks.]
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represent hemorrhage, necrosis, or dilated calyces. It is critical to evaluate the renal vein and inferior vena cava for possible tumor thrombus. CT confirms the presence of an intrarenal mass, determines local extent of Wilms tumor, visualizes vascular structures, identifies nodal involvement, evaluates presence or absence of liver metastases, and images the opposite kidney (Fig. 53 b, c). Calcification is identified by CT in approximately 15 % of eases. Chest CT is also performed, since pulmonary metastases are present in over 10% of patients at the time of initial diagnosis. MRI accurately assesses the renal origin of Wilms tumor as well as its margins and local extension. Orthogonal plane imaging of MRI is useful for detecting spread of tumor to adjacent structures.

Neuroblastoma
Neuroblastoma is the most common extracranial solid malignant tumor in children; it is the third most common pediatric malignancy, surpassed in incidence only by acute leukemia and primary brain tumors. Neuroblastoma is the second most common abdominal malignancy in the older infant and child, occurring with an almost equal frequency as Wilms tumor. Neuroblastoma is a malignant tumor of primitive neuroblasts that may arise anywhere within the sympathetic ganglion chain or adrenal medulla.

Fifty percent of patients are less than 2 years of age, 75% of patients are less than 4 years of age, and fewer than 10% of neuroblastomas are in children over age 10. Neuroblastoma usually remains clinically silent until it invades or compresses adjacent structures, metastasizes, or produces unusual paraneoplastic syndromes. At least 70% of patients will have disseminated disease at the time of diagnosis, and many presenting symptoms and signs are secondary to metastases. Common sites of metastatic disease are skeleton, bone marrow, liver, lymph nodes, and skin.

Neuroblastoma and its more differentiated forms, ganglioneuroblastoma and ganglioneuroma, arise from primitive sympathic neuroblasts of the embryonic neural crest. Microscopically, the tumor consists of small, round cells. Neuroblastoma is composed entirely of undifferentiated sympathoblasts; ganglioneuroblastoma contains undifferentiated neuroblasts and mature ganglion cells; ganglioneuroma is a benign tumor containing mature ganglion cells. Two-thirds of neuroblastomas are located in the abdomen; approximately 2/3 of these abdominal tumors arise in the adrenal gland.

a	Figure 54.Unresectable Stage IV neuroblastoma. 3-year-old male with palpable abdominal mass. a) Us. There is a large, inhomogeneous, echogenic mass (M) above the right kidney. b) Contrast-enhanced CT. The large retroperitoneal mass displaces the right kidney (RK) laterally and inferiorly. Neuroblastoma extends across the midline posterior to the aorta (A). Note that the aorta (A), superior mesenteric artery (a), superior mesenteric vein (v), inferior vena cava (I), right renal artery (arrows), and left renal artery (arrowheads) are completely surrounded and encased by tumor mass. The tumor is not resectable. c) Caranal proton-density MRI. The large neuroblastoma (large arrows) displaces the right kidney (RK) laterally and inferiorly and crosses the midline. The tumor mass surrounds the aorta (A), right renal artery (small arrows), and left renal artery (arrowheads). d) Sagittal proton-density MR/. The large neuroblastoma (arrows) surrounds and encases the aorta (A), celiac axis (c), and superior mesenteric artery (s). L=liver. [From Kirks.]
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During the past decade, CT has become the imaging modality of choice for patients with neuroblastoma. Currently, MRI is playing an increasingly important role in determining the relationship of tumor to vascular structures, detecting bone marrow involvement, diagnosing extradural tumor extension, and improving preoperative staging.

Neuroblastoma can usually be distinguished from Wilms tumor by US because of its extra renal location (Fig. 54 a). Moreover, the echogenicity of neuroblastoma is more inhomogeneous than Wilms tumor due to increased cellularity, hemorrhage, necrosis, or dystrophic calcification. CT is superior to sonography for defining morphologic details of neuroblastoma and precisely assessing extent of disease. Neuroblastoma is commonly suprarenal or paravertebral in location. It is usually inhomogeneous due to tumor necrosis and contains calcification by CT in approximately 85% of patients. Neuroblastoma commonly extends across the midline behind the aorta and surrounds intra-abdominal vessels (Fig. 54 b). The advantages of MR over CT and sonography are as follows: (l) Multiple planes of imaging which is useful for assessing adjacent organ invasion (Fig. 54 c); (2) Exclusion or detection of extradural tumor extension, without requiring intrathecal contrast injection; (3) Identification of bone marrow metastases which is useful for staging; and (4) Better delineation of intra-abdominal vessel displacement or encasement (Fig. 54 d).

Neonatal adrenal hemorrhage
Adrenal hemorrhage is a relatively common abnormality of neonates that may present as an asymptomatic mass. Symptoms and signs may include anemia and jaundice. The etiology of renal hemorrhage is unknown, but birth trauma, stress, anoxia, dehydration, and systemic disease have been implicated. Surgical intervention is usually unnecessary unless there is secondary infection with adrenal abscess formation. On initial US, adrenal hemorrhage may appear as a solid lesion (Fig. 55 a), which subsequently liquefies and then shows the classic anechoic appearance of a hematoma. The mass may again become echogenic as clot and subsequently calcification develop. Sequential US shows a decrease in size of the mass with eventual disappearance or calcification over several months (Fig. 55 b-d).
The primary differential diagnostic considerations in a neonate with a suprarenal mass are adrenal hemorrhage and neuroblastoma. US almost

a	Figure 55. Neonatal adrenal hemorrhage. Newborn with anemia, jaundice, and a questionable right abdominal mass. a) 1 day of age. Longitudinal sonography demonstrates an inhomogeneous, solid mass (arrows) above the right kidney (k). b) 1 week (left) and 2 weeks (right) of age. Sequential sonography demonstrates an adrenal hematoma above the right kidney (k) that becomes smaller and more hypoechoic with time. c) 1 month of age. The adrenal hemorrhage (arrows) above the right kidney (k) is now smaller and anechoic. d) 5 months of age. There is an echogenic focus (H) above the right kidney (k). Plain films demonstrated suprarenal calcification. [From Kirks.]
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always is able to distinguish between neuroblastoma (echogenic and vascular) and neonatal adrenal hemorrhage (anechoic and avascular). Moreover, because congenital adrenal neuroblastoma has an excellent prognosis, serial US is an acceptable way to differentiate the exceedingly rare case in which history, physical examination, and sonography are not diagnostic. If immediate differentiation is imperative, MRI may confirm adrenal hemorrhage.

 

Donald R. Kirks and Sven Laurin