Extremely Large Fetal Urinary Bladder (Megacystis)
·Posterior urethral valves- Urethral obstruction is most commonly due to posterior urethral valves (PUV). Sonography reveals persistent dilatation of the bladder +/— proximal urethra, bladder wall thickening (>2 mm), dilatation of renal collecting system. Rupture of the calyces resulting in urinomas and urinary ascites may occur. OH in the presence of massive bladder dilatation usually indicates a poor prognosis.
·Urethral atresia/absence of urethra- The kidneys may be hydronephrotic or dysplastic and echogenic. There is massive dilatation of the bladder, which occupies most of the fetal abdomen. OH is always associated.
·Megacystitis-microcolon-intestinal hypoperistalisis syndrome- MMIHS is a rare congenital anomaly. The syndrome consists of intestinal malrotation, functional intestinal obstruction, microcolon and large non-obstructed urinary bladder. The la&t is a striking and constant finding on prenatal ultrasonography. OH may be observed in the second and early third trimester. The fetal megacystis is usually accompanied by upper renal tract dilatation. In later pregnancy dilated loops of bowel may be demonstrated.
·Prune belly syndrome- This syndrome is characterized by severe deficiency of the abdominal wall musculature associated with gross dilatation of the bladder and ureters. This may follow resolution of urinary ascites.
·Caudal regression syndrome- This is a rare syndrome characterized by vertebral agenesis of varying degree and a wide variety of associated anomalies. The vertebral agenesis can vary from partial agenesis to total agenesis of the lumbosacral spine. The syndrome is strongly associated with maternal insulin dependent diabetes. The incidence is 200 times higher in diabetic than non-diabetic pregnancies. There is a constellation of CVS, GIT, CNS, genitourinary and musculoskeletal defects.