1999-05-11-16 Prune-belly syndrome © Silva www.thefetus.net/
Updated 2006-01-18 by Juliana Leite, MD
Original text 1999-05-07 Philippe Jeanty, MD, PhD & Sandra R Silva, MD
Synonym: Eagle-Barrett syndrome.
Definition: Prune-belly syndrome is a rare congenital disorder, more common in males, consisting of deficiency of abdominal wall muscles (absent or hypoplastic), cryptorchidism, and genitourinary malformations.
Etiology: Many theories have been proposed to explain the pathogenesis of this anomaly. The first one proposes that occurs an abnormal mesodermal development. The developmental arrest of the mesodermal elements would lead to severe abdominal laxity and defective development of the urinary tract. The second one is the urethral obstruction malformation complex. It proposes that pressure atrophy of the abdominal wall muscles occurs when urethral obstruction leads to massive distention of the bladder and ureters. Bladder distention would also interfere with descent of the testes and thus be responsible for the bilateral cryptorchidism. The mechanism responsible for the urinary tract dilatation and distention is a flap valve mechanism that results from a hypoplasia of the stromal and epithelial elements of the prostatic urethral. The hypoplasia of these elements leads to an underlying weakness and subsequent sacculation of the prostatic urethra. The last theory is the genetic defect that is suspected because of the predominance in males and few familial cases.
Incidence: 0.25 to 0.3:10,000 live births, almost exclusively in males (M20:F1). The higher incidence of this syndrome in males has been explained on the basis of the more complex morphogenesis of the male urethra, possibly resulting in obstructive anomalies at several levels.
Diagnosis: The diagnosis should be suspected in fetuses with very large abdominal masses. These are, most typically, bladder obstruction caused by urethral valves, urethral agenesis, but also other abdominal masses such as ovarian cyst. Possible results are oligohydramnios with consequent pulmonary hypoplasia and urinary ascites. The oligohydramnios, usually, makes impossible the detection of cryptorchidism. Other findings could be: Potter face, pulmonary hypoplasia, gastric dilatation, short bowel, micro ileum, microcolon, malrotation of the intestines imperforate anus, arthrogryposis and clubfoot. Additional information can be gained by addition three-dimensional ultrasonography scanning and could be useful for more-efficient counseling and therapeutic planning.
Figure 1: A massively distended bladder as in this case of urethral agenesis is the main cause of Prune-belly syndrome.
Differential diagnosis: Urinary tract anomalies such as megacystis megaureter, urethral obstruction, and primary vesicourethral reflux are differential diagnoses. Neurogenic bladder and megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) may also be considered, although the latter presents with normal amniotic fluid.
Prognosis: The prognosis depends on the degree of renal function compromise. Outcome is typically good in cases of Prune-Belly syndrome with normal amniotic fluid volume. The early urinary obstruction, present in the majority of cases, leads to renal failure, pulmonary hypoplasia, and death in the neonatal period. More than 60% o f infants died in the first week of life. Early decompression of severe bladder obstruction improves the prognosis. Fetuses that develop mild urinary tract distention have better prognosis. Mild hydronephrosis and megalourethra may be the only manifestations in these cases.
Recurrence risk: Unknown, but low. A familial occurrence has been seen in some affected patients, suggestive of an X-linked inheritance 6. A multifactorial, or polygenic, inheritance has also been proposed.
Managment: Sonographic monitoring of the urinary tract and amniotic fluid volume is required throughout the pregnancy. When early and/or severe distention of the urinary tract is observed, a vesicoamniotic shunts with vesical decompression and correction of the amniotic fluid levels has been proposed to improve renal and pulmonary function. Anatomic abnormalities that warrant consideration of correction are those that interfere with critical fetal organ development. Experimental evidence suggests that fetal urinary tract obstruction, whether intermittent or persistent, can lead to renal dysplasia, which is often irreversible, even if the obstruction is relieved immediately after birth. The percutaneous placement of an indwelling catheter for urinary diversion is one possible therapy. Urinary tract decompression in the early second trimester is desirable to reduce the potential for ongoing damage to the developing kidneys. The benefits of such therapy remain controversial and are yet to be evaluated in a prospective, randomized fashion. As such, urinary diversion should be considered on a case-by-case basis. Additionally, correction of severe oligohydramnios as early as possible should reduce the possibility of pulmonary hypoplasia. Abdominal wall reconstruction for both aesthetics and function is often necessary. Because 75% of individuals with Prune-Belly syndrome have extra urinary anomalies, a thorough evaluation, especially cardiac, should be performed.
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