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RENAL DILATATION DIAGNOSTIC RADIOLOGY
Category: Diagnostic Radiology
Abstract : Renal dilatation Hydronephrosis is frequently detected antenatally, although
the cause may be difficult to demonstrate. Dilatation is due either to
obstructive uropathy, for example vesico- or pelviureteric junction obstruction,
posterior urethral valves or obstructed upper moiety of a duplex kidney, or it
may be nonobstructive, for example due to reflux. Postnatal ultrasound scans
sh
Renal dilatation
Hydronephrosis is frequently detected antenatally, although
the cause may be difficult to demonstrate. Dilatation is due either to
obstructive uropathy, for example vesico- or pelviureteric junction obstruction,
posterior urethral valves or obstructed upper moiety of a duplex kidney, or it
may be nonobstructive, for example due to reflux.
Postnatal ultrasound scans
should be performed when the infant is more than 4 days old, because there is
commonly a period of dehydration immediately after birth. This may cause an
obstructed or otherwise dilated kidney to appear normal for the first few days
of life. If normal a follow-up scan is generally recommended at about the age of
6 weeks.
The presence of any calyceal dilatation or ureteric dilatation,
as opposed to dilatation confined to the renal pelvis, is an important factor to
note, indicating a greater degree of severity. A measurement of the
anteroposterior diameter of the dilated intrarenal pelvis is a useful baseline
from which to compare subsequent follow-up scans. It should be noted that slight
separation of the renal pelvis is a normal finding in the newborn: an
anteroposterior renal pelvis of 5 mm is the upper limit of normal.
The
presence of a baggy, extrarenal pelvis, less than 10 mm, without pelvicalyceal
system (PCS) dilatation is usually managed conservatively using ultrasound
monitoring to demonstrate any increasing dilatation. PCS dilatation with a renal
pelvic diameter of between 10 and 20 mm is more serious and likely to require an
assessment of renal function with a MAG3 renogram. Conservative treatment is
possible, but surgery may be required for very poor function.
The dilated
renal tract is predisposed to infection due to ascending infection in reflux or
haematogenous infection in an obstructed system, where a pyonephrosis requiring
percutaneous nephrostomy may develop. As a consequence antibiotic prophylaxis is
frequently advised in the neonate with significant renal tract
dilatation.
Bilateral renal tract dilatation in boys may be due to
posterior urethral valves with secondary dilatation of the upper tracts due to
the urethral obstruction. The diagnosis is confirmed by fluoroscopic micturating
cystography. This diagnosis may be suspected sonographically by the association
of bilateral hydronephrosis with a distended and thick-walled bladder.
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