*2.3.15. Meconium peritonitis*

Ultrasound diagnosis is based on three elements:

266 Congenital Anomalies - From the Embryo to the Neonate

therefore, repeated scans are mandatory.

trimester scan in about 1 in 1500 pregnancies [28].

• oligohydramnios.

*2.3.13. Megacystis*

and urethral stenosis.

*2.3.14. Posterior urethral valves*

and 13, del 2q, and 69 XXY.

• absent fetal bladder.

• bilaterally enlarged kidneys of typical hyperechogenic texture.

The disease can be diagnosed late in pregnancy or may progress gradually during pregnancy;

The prognosis depends on the clinical variety of IPKD, which can vary from mild to severe with intrauterine death. After birth, the most important complications are respiratory, as a consequence of the pulmonary hypoplasia. Death later in life is the result of renal failure.

The management depends on the diagnosis age; if the diagnosis is made before viability, termination of pregnancy should be offered to the parents. Also in cases with severe oligohydramnios and absent bladder, the termination of pregnancy can be offered even in the third trimester.

It represents an enlarged urinary bladder usually due to a bladder outlet obstruction [lower urinary tract obstruction (LUTO)], which may appear also in nonobstructive conditions (megacystis-microcolon-intestinal hypoperistalsis syndrome). It can be detected from the first

Prognosis, management, prediction of resolution, and postnatal outcome depend on the subsequent cause. Fetal lower urinary tract obstruction (LUTO) has an incidence of 2.2/10000 births and it is usually diagnosed during the late first or early second trimester of pregnancy [28, 29]. The most common condition in the LUTO spectrum includes urethral valves, urethral atresia,

It is a condition that causes lower urinary tract obstruction due to a membrane-like structure in the posterior urethra of male fetuses. The disease is usually sporadic, and has a heterogeneous embryologic origin. Young type I syndrome valves seem to result from an exaggerated development of the urethrovaginal folds with an abnormal insertion of the distal end of the Wolffian ducts. Other valves, like in Young type III, develop because of abnormal canalization of the urogenital membrane [30]. Distention of the bladder (megacystis) leads to vesicoure-

Posterior urethral valves can be associated with other anomalies of the urinary tract (sequence) megacystis, megaureter, hydronephrosis, paraureteral diverticula, and dilatation of proximal urethra, cryptorchidism, and hypospadias. There are also extraurinary anomalies that can be associated: tracheal hypoplasia, patent ductus arteriosus, total anomalous pulmonary vein drainage, mitral stenosis, scoliosis, skeletal anomalies in lower extremities, and imperforate anus. The most frequent chromosomal abnormalities that can be associated are: trisomies 18

teral reflux and hydronephrosis and can cause renal dysplasia [30].

Intestinal perforation in fetuses during pregnancy can lead to a sterile, chemical, and localized type of peritonitis. At the site of the perforation, a reactive process of calcification and fibrosis occurs in order to stop the progression. The etiology is in over 50% of cases due to intestinal stenosis, atresia, or meconium ileus. Other cited situations are volvulus or Meckel's diverticulitis. Meconium ileus is associated with cystic fibrosis and results from the blockage of the distal ileum with compacted meconium. The incidence is 1:3000 births.

The diagnosis is suggested by the dilatation of the intestinal loops or the presence of hyperechoic areas situated in the abdomen of the fetus. Over 80% of the fetuses that developed meconium peritonitis also have intra-abdominal calcifications. Ascites is an important sign of intestinal peritonitis. Other ultrasonographic signs suggesting meconium peritonitis include: polyhydramnios, meconial pseudocysts, thickening of the abdominal wall or pleural effusions.

The differential diagnosis of hyperechoic abdominal masses include: intra-amniotic hemorrhage, early ascites, fetal hypoxia, meconium peritonitis, and cystic fibrosis.

Meconium ileus and hyperechoic images of the intestinal loops at 16–18 weeks of gestation can be present in over 75% of cystic fibrosis affected fetuses. The incidence of cystic fibrosis in fetuses diagnosed before birth with intestinal obstruction is approximately 10%, consequently when other causes of intestinal blockage have been excluded, a genetic cystic fibrosis test is recommended.

The prognosis is poor in this case; approximately, 50% of fetuses suffering from meconium peritonitis pass away in the neonatal period.
