kidneys – microcystic

infantile polycystic kidney disease

sagittal views demonstrate bilateral massively enlarged echogenic kidneys. the renal cortex is hypoechoic relative to the internal hyperechoic medullary area. the transverse view shows the abnormal size of the kidneys as they occupy greater than one third of the abdominal circumference. there is no evidence of bladder filling and oligohydramnios is evident.;

infantile polycystic kidney disease

coronal views of the fetal abdomen reveal large echogenic kidneys. a small bladder is noted along with less than average amniotic fluid implying diminished but not absent renal function at this point in pregnancy. the hypoechoic renal pelvis is clearly seen contrasted by the hyperechoic renal parenchyma.

description

echogenic or microcystic kidneys can be seen as an isolated finding or can be associated with a chromosomal abnormality or other syndrome. renal failure and oligohydramnios can occur as part of a syndrome or secondary to bilateral isolated renal disease. the embryology, aetiology and incidence of this category of renal malformations varies greatly depending upon the syndrome or primary diagnosis. (see infantile polycystic disease, adult polycystic kidney disease)

diagnosis

echodense kidneys may be visualised from the end of the first trimester and throughout pregnancy. microcysts may be identified in the renal parenchyma in the second trimester or later and may increase in size or number as the pregnancy progresses leading to significantly enlarged kidneys by the late second or third trimester. oligohydramnios may also develop. identification of associated findings can be critical to syndrome identification and chromosome abnormalities should be considered.

differential diagnosis

multicystic kidney disease is characterised by large macroscopic cysts of varying sizes in the renal parenchyma and may be unilateral or bilateral. obstructive lesions often involve hydronephrosis, (caliectasis, pyelectasis), hydroureter (dilated ureters), megacystis (enlarged bladder) or dilated/obstructed urethra. renal tumours can present as echodense masses and may replace part or all of the renal parenchyma. haemorrhage, necrosis and cystic degeneration can sometimes give the appearance of cysts. tumours can be unilateral or bilateral and can be associated with polyhydramnios, normal fluid or decreased fluid. (see also wilmsí tumour, mesoblastic nephroma) adrenal or other abdominal tumours can be distinguished by identifying a normal appearing kidney often displaced from its usual location in the lumbar fossa. (see also neuroblastoma)

sonographic features

kidneys appear normal or echogenic

initially normal size but may enlarge later

unilateral or bilateral

discrete cyst(s) may be identified but usually too small

usually normal amniotic fluid volume – if bilateral oligohydramnios may develop later

a 2 vessel cord and other malformations associated

no findings associated with obstruction present

associated syndromes

fryns
jeune asphyxiating thoracic dystrophy
majewski
meckel’s
renal dysplasia retinal aplasia
trisomy 13
trisomy 18
tuberous sclerosis
von hippel lindau
zellweger

references

warkany j in: congenital malformations, notes and comments mosby year book: chicago, p1061-1064
crawfurd md’a in: the genetics of renal tract disorders oxford u press: new york/london, p55
crawfurd md’a in: the genetics of renal tract disorders oxford u press: new york/london, p544
crawfurd md’a in: the genetics of renal tract disorders oxford u press: new york/london, p443
stevenson r, hall t, goodman r in: human malformations and related anomalies, vol ii oxford u press: new york/london, p546,547