Diagnostic ultrasound ( PDFDrive )

CHAPTER 39 The Fetal Urogenital Tract 1347
nephrology consultation. A VCUG is indicated if there is contralateral
hydronephrosis or a history of UT infection. 75
he natural history of MCDK is toward spontaneous involution.
his has been well documented both before and ater
birth. 70,72 he longer the duration of follow-up, the higher is the
likelihood that the dysplastic kidney will become so small as to
not be evident sonographically. he risk of hypertension associated
FIG. 39.13 Bilateral Multicystic Dysplastic Kidneys. Transvaginal
image in a 16-week fetus demonstrates numerous small bilateral cysts
(arrows) and no normal renal parenchyma. Note anhydramnios due to
nonfunctioning kidneys.
with MCDKs does not appear to be greater than that of the
general population, 76 and the rates of malignant transformation
of MCDK are small. 77 Although there are some proponents for
routine laparoscopic nephrectomy, conservative management
(with clinical and ultrasound surveillance) is favored in most
centers. 78 Most cases of MCDK are sporadic, with a low recurrence
risk. However, some cases have been associated with mutations
in hepatocyte nuclear factor 1β (HNF1β), which carries an
autosomal dominant mode of inheritance with both interfamilial
and intrafamilial variability in the clinical manifestations. 79
Obstructive Cystic Renal Dysplasia
he efect of urinary obstruction on subsequent renal development
depends on the time of onset and severity of the obstruction.
Experimental work in lambs has shown that urinary obstruction
starting in the last half of gestation causes simple hydronephrosis
and, when severe, parenchymal atrophy. 80 However, if the urinary
obstruction starts during the irst half of gestation, renal dysplasia
and sometimes cyst formation will occur 80-82 (Fig. 39.14). he
fetal UT responds diferently to chronic obstruction than the
adult UT. In adults with chronic urethral obstruction, the pelvicalyceal
system is usually greatly dilated; in the fetus there may
be a relative lack of pelvicalyceal dilation and possible development
of macroscopic renal cysts.
Unilateral renal dysplasia can be caused by UPJ obstruction
or ureterovesical junction (UVJ) obstruction. Bilateral disease
is caused by severe bladder outlet obstruction, usually due to
urethral atresia or posterior urethral valves. he severity of renal
dysplasia is related to the timing and severity of obstruction to
A B C
D E F
FIG. 39.14 Urinary Tract Obstruction Produces a Varied Response From the Kidneys. (A) Normal kidney. (B) Pelvicaliectasis, with or
without parenchymal atrophy. (C) Renal cystic dysplasia, with parenchymal cysts. (D) The dysplastic kidney may cease to function (lack of pelvicaliectasis).
(E) and (F) Alternatively, the kidney may show increased echogenicity, with no visible cysts but with pelvicaliectasis (E) or without
pelvicaliectasis (F). In these cases, dysplasia is probably, but not invariably, present.