In 1895, Parker described the congenital triad of deficient abdominal musculature, cryptorchidism, and urinary tract abnormalities. Subsequently, the term “prune-belly syndrome”
was coined for this condition based on the characteristic wrin- kled appearance of the abdomen. The incidence of the syn- drome is estimated to be 1 in 35,000 to 1 in 50,000 live births.
GENETICS/BASIC DEFECTS
1. Etiologies
a. Questionable genetic inheritance
i. Questionable autosomal dominant inheritance ii. Autosomal recessive inheritance suggested by
some authors
b. Fetal abdominal distension caused by urinary tract obstruction
i. The most common cause of prune-belly syndrome ii. Urethral obstruction causing dilatation of the fetal bladder and upper tracts thereby attenuating the abdominal musculature
iii. Spontaneous relief of the urethral obstruction in some cases prenatally decompresses the abdomen producing the shriveled, prune-like appearance of the baby’s abdomen
iv. Persistent urethral obstruction causing huge distention of the urinary bladder, bilateral hydro- nephrosis and hydroureter complicated by oligo- hydramnios in more severe cases
c. Fetal ascites from whatever cause: abdominal decom- pression during intrauterine life leading to prune belly appearance of the abdomen
d. Prostatic hypoplasia resulting in a functional urethral obstruction leading to development of the prune-belly syndrome
e. Primary mesodermal defect simultaneously affecting the formation of abdominal musculature and abnor- malities in the lower urinary tract
f. Rare association of chromosome abnormalities i. Trisomy 13
ii. Trisomy 18
iii. Turner syndrome with fetal ascites (pathogenetic mechanism thought to involve abdominal disten- tion by ascites rather than by urinary obstruction) iv. Ring X chromosome lacking XIST
v. Cat-eye syndrome vi. Rarely with trisomy 21
vii. Mosaic unbalanced chromosome constitution of chromosome 16
viii. Presence of a small additional chromosome fragment
ix. Interstitial deletion of chromosome 1 [del(1) (q25q32)]
2. Pathogenesis: abdominal wall hypoplasia as a nonspe- cific lesion resulting from fetal abdominal distension of various causes
3. Terminologies
a. Prune belly: a descriptive term for a wrinkled and flaccid abdominal wall secondary to stretched skin, soft tissues, and muscles of the abdomen
b. Prune-belly syndrome generally used to indicate the condition having prune belly, cryptorchidism, and abnormalities of the urinary tract
4. Causes of urine flow impairment/obstruction a. Renal causes
i. Pelvi-ureteric junction anomaly ii. Vesico-ureteric junction anomaly iii. Posterior urethral valves
iv. Duplex systems
v. Ureterocele/ectopic ureter vi. Urethral atresia
vii. Cloacal anomaly viii. Vesico-ureteric reflux
ix. Megaureter
x. Megacystis microcolon xi. Hypoperistalsis syndrome b. Extrarenal causes
i. Sacrococcygeal teratoma ii. Hydrometacolpos iii. Other pelvic masses
CLINICAL FEATURES
1. Broad spectrum in severity
2. Nearly 95% of cases occurring in males 3. Abdomen
a. Partial or complete absence of the abdominal muscu- lature
b. Thin/lax protruding abdominal wall c. Wrinkled abdominal skin
d. Visible intra-abdominal intestinal patterns through thin abdominal wall
4. Genitourinary anomalies
a. Bilateral cryptorchidism in males b. Urethral obstruction
c. Dilated/hypertrophic bladder
d. Dilated urethra, particularly the prostatic urethra e. Dilated/tortuous ureters
f. Renal dysplasia/hypoplasia with cystic changes g. Hydronephrosis
h. Absence or hypoplasia of the prostate i. Ventral body wall defects
i. Cloacal exstrophy ii. Bladder exstrophy iii. Hypo/epispadias
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j. Potter sequence i. Oligohydramnios ii. Potter face
iii. Pulmonary hypoplasia iv. Other deformations 5. Secondary malformations
a. Gastrointestinal obstruction i. Malrotation
ii. Atresia iii. Stenosis
iv. Volvulus v. Splenic torsion vi. Imperforate anus vii. Anorectal agenesis
b. Limb and other skeletal abnormalities believed to be the direct result of oligohydramnios with resultant fetal crowding
i. Talipes equinovarus ii. Metatarsus adductus iii. Vertical talus
iv. Hip dislocation v. Arthrogryposis
vi. Pectus excavatum/carinatum vii. Congenital muscular torticollis viii. Infantile scoliosis
ix. Severe leg maldevelopment a) Generalized hypoplasia b) Complete absence c) Terminal defects c. Cardiac malformations
i. Tetralogy of Fallot ii. Ventriculoseptal defect d. Cleft lip
e. Spina bifida
f. Association with diverse chromosome syndromes i. Trisomy 13
ii. Trisomy 18 iii. Turner syndrome
iv. Cat-eye syndrome v. Trisomy 21 vi. Others 6. Prognosis
a. High mortality although compatible with long-term survival
i. Stillbirth or death by one moth of age in 20% of cases
ii. Death by the second year for additional 30% of cases
b. Causes of death
i. Renal failure secondary to renal dysplasia pres- ent at birth
ii. Pulmonary complications including lung hypoplasia
iii. Infection associated with urinary stasis or opera- tive interventions
DIAGNOSTIC INVESTIGATIONS
1. Renal and bladder ultrasound 2. Contrast voiding cystourethrogram 3. Radiography
a. Hypoplastic lungs with flared lower ribs secondary to the distended abdomen
b. Diffusely distended flanks
c. Dilated/dysplastic calyces of the kidneys d. Markedly dilated/tortuous ureters e. Vertical and trabeculated bladder f. A wide and long posterior urethra g. Cryptorchidism
4. Histology of the abdominal wall
a. Muscle atrophy (degeneration of already formed muscle), not of primitive muscle
b. The finding supports the theory that the abdominal muscle hypoplasia is a nonspecific lesion, resulting from fetal abdominal distension of various causes 5. Chromosome analysis for multiple congenital anomalies
GENETIC COUNSELING
1. Recurrence risk
a. Patient’s sib: not increased unless in autosomal reces- sive inheritance (which is still unclear)
b. Patient’s offspring: not increased 2. Prenatal diagnosis by ultrasonography
a. Signs of fetal abdominal laxity (characteristic abdom- inal appearance) associated with fetal urinary tract abnormalities
i. Amniotic fluid wave produced by fetal movement ii. Sinusoidal undulation of the fetal anterior abdominal wall produced by tapping the mater- nal abdomen
b. A distended bladder (megacystis) and ureters c. Cryptorchidism
d. Oligohydramnios e. Fetal ascites
f. Lung hypoplasia g. Associated anomalies
i. Other renal anomalies (25%) ii. Extra-renal abnormalities (12%)
a) Anorectal anomalies b) VATER syndrome c) Esophageal atresia
d) Pattern compatible to specific chromosomal abnormality
3. Management
a. Orchidopexy for cryptorchidism b. Treatment of vesicoureteral dysfunction
i. Temporary diversion ii. Ureteral reconstruction
c. Treatment of vesicourethral dysfunction i. Reduction cystoplasty
ii. Internal urethrotomy iii. Megalourethra repair d. Abdominal wall reconstruction
e. Vesico-amniotic shunt placement for suspected pre- natal obstructive uropathy: remains controversial
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Fig. 1. A premature male neonate with prune-belly syndrome due to urethral atresia. He lived for 2 hours. There was a massive dilation and hypertrophy of the urinary bladder. Mild hydronephrosis was seen in one kidney but the second kidney was hypoplastic. The anterior abdominal wall showed muscle deficiency. Additional anomalies included imperforate anus with vesicorectal fistula, secundum type atrial septal defect of the heart, mild coarctation of the aorta, and bilat- eral talipes equinovarus.
Fig. 2. A male fetus with prune belly syndrome due to severe urethral stenosis. There were marked dilatation of the proximal urethra, blad- der and bilateral ureters. Mild hydronephrosis and cystic renal dyspla- sia were seen in both kidneys. There were no other anomalies.
Fig. 3. An infant with prune belly syndrome showing thin, flaccid abdominal wall through which intra-abdominal intestinal patterns are visible.
Fig. 4. A postmortem infant with prune belly syndrome showing flac- cid and wrinkling abdominal wall with visible intestinal patterns.
Fig. 5. A neonate with prune belly syndrome showing wrinkling abdominal wall due to multicystic kidneys. The infant also has dupli- cated great toes.
