Diagnostic ultrasound ( PDFDrive )

CHAPTER 52 The Pediatric Urinary Tract and Adrenal Glands 1815
of the intracranial vessels and aorta and aortic dissection are
additional associations. 181
Multicystic Renal Dysplasia
Multicystic dysplastic kidney (MCDK) is a congenital malformation,
with an incidence of about 1 per 4000 live births. 182
Histologically, multiple noncommunicating cysts are separated
by dysplastic parenchyma. he etiology of MCDK is uncertain,
although various theories have been proposed. he “ureteric bud
theory” of Mackie and Stephens hypothesizes that MCDK may
result from a ureteric bud that is atretic or connects abnormally
with the metanephric mesenchyme and the developing bladder,
resulting in obstruction. 183 Work by Batourina and colleagues 184
and Viana and colleagues 185 suggests that an abnormal interaction
between the developing bladder trigone and the distal ureter
may result in dysfunction at the ureterovesical junction and
subsequent obstruction. Bilateral MCDK disease is usually lethal
shortly ater birth, owing to associated pulmonary hypoplasia
secondary to prolonged oligohydramnios in utero. With unilateral
MCDK, renal function is usually maintained by the contralateral
kidney. 186 Although MCDK can be an isolated inding, it frequently
occurs in association with other anomalies of the urinary tract,
most commonly VUR, UPJO, and UVJO. 186 It is also a common
or characteristic inding in multisystemic genetic disorders
such as branchio-oto-renal syndrome and renal-coloboma
syndrome. 183
MCDK is usually diagnosed by prenatal sonography (Fig.
52.57, Video 52.7), or if unilateral may be found as an abdominal
mass at birth. he common pelvoinfundibular form of MCDK
manifests as numerous, randomly distributed noncommunicating
cysts of varying size. here is no renal pelvis or renal sinus, and
renal parenchyma is absent or dysplastic. he less common
hydronephrotic form of MCDK consists of multiple small,
peripheral cysts and a larger central cyst, with some connections
between the peripheral cysts and the central cyst. he entire
kidney is usually involved and may be small, normal in size, or
enlarged. here is no or minimal functional renal tissue. 187 he
contralateral kidney usually demonstrates compensatory hypertrophy.
Segmental involvement may occur, most oten in the
upper-pole moiety of a duplex kidney. 188 In patients with no
other urologic abnormalities, MCDK is managed nonoperatively,
as the risk of associated malignancy is low. Most afected kidneys
will undergo partial or complete involution. 189
FIG. 52.55 Autosomal Dominant Polycystic Kidney Disease
(ADPKD). Longitudinal gray-scale image of 33-week gestational age
fetus of a mother with ADPKD reveals a small, round cyst in the upper
pole of the right kidney consistent with ADPKD (arrow). Renal parenchymal
echogenicity is slightly increased and the medullary pyramids are
hypoechoic. Both right and left kidneys were mildly enlarged for gestational
age.
Nephronophthisis and Medullary
Cystic Disease
Nephronophthisis (NPHP) is an autosomal recessive tubulointerstitial
disorder, and one of the most common causes of inherited
end-stage kidney disease in children and young adults. 190 To
date, 19 causative genes have been identiied, although the
causative genes are still unknown in approximately 70% of afected
patients. 164 At presentation children usually are 4 to 6 years of
A
B
FIG. 52.56 Autosomal Dominant Polycystic Kidney Disease (ADPKD). (A) and (B) Longitudinal prone gray-scale images in a 17-year-old girl
demonstrate enlarged right and left kidneys, respectively, containing multiple cysts of varying size. Scattered linear and punctate echogenic foci
may represent mural calciications and/or stones (arrows).