megacystis – microcolon intestinal hypoperistalsis syndrome

differential diagnosis

in a male fetus the classic keyhole” sign of posterior urethral valves should be excluded. renal changes due to obstructive uropathy are usually more severe and/or progressive. decreasing amniotic fluid volume in the second trimester or oligohydramnios suggests an obstructive uropathy. in females with urethral obstruction or detrusor hypertrophy, severe oligohydramnios is usually seen. dilated loops of bowel can be seen due to an obstructive lesion intraabdominally or secondary to an abdominal wall defect. care should be taken to rule out a small herniation of bowel which could result in obstruction. in these cases the bladder is usually not distended and bowel peristalsis can often be identified. hydrocolpos can result in a cystic mass in the lower abdomen and can be associated with an enlarged bladder, hydroureter and hydronephrosis with normal fluid volume in a female fetus. identification of the uterus arising from the cystic vagina or evidence of a bulging hymen will identify the source of the mass. an ovarian cyst can sometimes cause compression resulting in bladder enlargement, hydroureter and hydronephrosis in the presence of normal amniotic fluid. the usually round (not tubular) shape of the cyst and its location should differentiate it from dilated bowel. hirschprungís disease and other conditions involving myenteric plexus abnormalities are characterised by lack of ganglia on pathological examination, but prenatal ultrasound findings may include enlarged bowel. ciip (chronic idiopathic intestinal pseudo-obstruction) may display similar but milder symptoms but is not usually diagnosed prenatally because onset is usually in adolescence or young adulthood. “