Year : 2001 | Volume
: 11 | Issue : 1 | Page : 25--28
Images : Prune belly sydrome : Antenatal ultrasound
S Ganesan, IK Indrajit
Department of Radiodiagnosis & Imaging, INHS, Asvini, Mumbai, India
Department of Radiodiagnosis & Imaging, INHS, Asvini, Mumbai 400 005
|How to cite this article:|
Ganesan S, Indrajit I K. Images : Prune belly sydrome : Antenatal ultrasound.Indian J Radiol Imaging 2001;11:25-28
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Ganesan S, Indrajit I K. Images : Prune belly sydrome : Antenatal ultrasound. Indian J Radiol Imaging [serial online] 2001 [cited 2020 Jul 4 ];11:25-28
Available from: http://www.ijri.org/text.asp?2001/11/1/25/28305
The Prune Belly syndrome (abdominal muscles deficiency syndrome, Eagle Barret syndrome) in its complete form is characterized by deficiency of abdominal wall muscles, undescended testis and dilated urinary tract. This syndrome has derived its name from the wrinkled prune like appearance of the abdominal wall . Sonographic observations in three cases of Prune Belly syndrome, prenatally diagnosed and subsequently confirmed are presented in a pictorial essay.
Prune Belly syndrome (PBS), an uncommon condition, results from failure of the lateral mesoderm to migrate or differentiate into the musculature of the abdominal wall and urinary tract which normally occurs by about the tenth week of fetal life . Even though associated ureteral anomalies like megaloureter, bulbar or penile urethral diverticulum may occur, classically no evidence of any intrinsic urethral obstruction can be demonstrated ,. The posterior urethra narrows abruptly at the pelvic floor but no intrinsic urethral obstruction is demonstrable. The prostate is hypoplastic while associated anomalies of the penis and distal urethra may be present in some cases. Most cases are sporadic, even though occurrences in small families are recorded. Associated anomalies have been reported in two cases, but in most of these cases chromosomal studies are normal, thus ruling out a possible genetic basis.
Abnormalities are consistently seen in the urinary tract. The morphology of the kidney is variable, ranging from a small globular kidney with four to five stubby calyces and a small poorly developed pelvis at one end to a grossly hydronephrotic kidney with distended calyces and a thin shell of cortex peripherally at the other end of the spectrum. The bladder is large with smooth thin walls. The ureters are dilated and tortuous. The ureters are characteristically irregular with segments of gross dilatation and redundancy alternating with segments of relatively normal caliber .
Histologically, the muscles in the wall of the urinary bladder and ureters are patchy and sparse and are replaced by varying amounts of collagen or mature fibrous tissue . On electron microscopy, the myofilaments appear thin and scanty . The lower portions of the recti and oblique muscles are most severely affected in the abdominal wall and are replaced by thin sheets of fibrous tissue. Scattered muscles fibres may be seen in different layers of the abdominal wall . Electron microscopic studies have revealed abnormalities suggesting arrest of normal muscle development .
In the complete syndrome the testes are intra-abdominal, cryptorchidism being attributed to the failure of development of the inguinal canal and gubernaculum . Malrotation of gut, congenital dislocation of hip, spina bifida and anorectal malformations have been reported as associated anomalies. Talipes, congenital dislocation of hips and other lower limb abnormalities are commonly found and are secondary to associated oligohydramnios [Figure 1].
Sonographic observations in PBS primarily reflect the pathological changes and are similar to severe urethral obstruction. Examination of the fetus shows a disproportionately large ballooned-out distended abdomen with overall abdominal diameter several times that of the thoracic diameter. A grossly dilated urinary bladder with or without a dilated upper urinary tract virtually occupies most of the ballooned-out abdomen with the abdominal wall appearing thin and membranous [Figure 2]. Characteristically the bladder wall appears thin, smooth and regular [Figure 2],[Figure 4],[Figure 6]. Careful evaluation of the fetal bladder base fails to demonstrate the presence of a dilated posterior urethra. A dilated posterior urethra appearing as a projection from the bladder base when present, virtually rules out this diagnosis ,. The ureters are also dilated and tortuous. Grossly dilated redundant ureteric segments alternating with ureteric segments of normal caliber are highly suggestive of this condition [Figure 2]b,[Figure 4],[Figure 5],[Figure 6]. The kidneys have a variable appearance depending upon the degree of dilatation of the pelvicalyceal system and the extent of obstructive cystic renal dysplastic features involving the renal parenchyma. The renal findings range from a grossly dilated pelvicalyceal system with a thin shell of renal parenchyma at one end of the spectrum, to a small shrunken kidney with a minimally dilated pelvicalyceal system and highly echogenic dysplastic renal parenchyma at the other end. There may be varying degrees of dilatation and obstructive cystic renal dysplasia in between. Spontaneous decompression of the urinary tract may occur in some patients, and these may manifest as fetal ascites or as perinephric urinoma [Figure 6],[Figure 7],[Figure 8] ,,. Oligohydramnios, often severe, is commonly present and may lead to a spectrum of anomalies secondary to pressure exerted by the uterine wall on the fetus. These include flattened cranium, facies and nose, low set ears and chin along with limb abnormalities like club feet, contractures and hip dislocation. Loss of normal stenting effect of the amniotic fluid results in pulmonary hypoplasia as well [Figure 2],[Figure 4],[Figure 5],[Figure 6],[Figure 7],.
PBS primarily has to be differentiated from similar conditions associated with a dilated bladder along with dilated and variable upper urinary tract findings. Posterior urethral valve is distinguished from PBS by the presence of a "stub" like dilated posterior urethra projecting from the base of the urinary bladder, which is thick-walled often with trabeculations. Urethral atresia with associated cloacal abnormalities may closely resemble PBS. Massive vesicoureteric reflux may be difficult to differentiate. Megacystis-microcolon syndrome may be mistaken for PBS, but the presence of polyhydramnios with a dilated stomach in the former helps in the differential diagnosis .
The overall prognosis in PBS depends upon the severity of the renal dysplasia and the presence of associated anomalies. Oligohydramnios when present is a poor prognostic indicator . The diagnosis of PBS can be made in the presence of the characteristic constellation of findings and by carefully excluding possible differential diagnoses in a given clinical setting.
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