Cystic Fetal Abdominal Masses
Normal fluid filled bowel
Cystic fibrosis/meconium pseudocyst/peritonitis
Dilated loops of bowel due to obstruction
Liver, Pancreas and Spleen
Choledochal cysts Choledochal cyst is a cystic dilatation of the biliary system.
· Omphalomesenteric- Various portions of omphalomesenteric duct may persist, giving rise to Meckel’s diverticulum, intraabdominal omphalomesenteric cyst, anomalies of the umbilicus such as fistulas, polyps or cysts of the umbilical cord, or a combination of these lesions. Cysts of the umbilical cord are usually small, but may be as large as 6 cm in diameter. These cysts are situated close to the abdominal wall. There is usually no blood flow through them.
· Vesicoallantoic abdominal defect- Failure of the allantoic cavity to obliterate results in vesicoallantoic communication between the bladder and umbilicus that may fall into one of four types: (1) patent urachus; (2) vesicourachal diverticulum; (3) umbilical cyst and sinus; (4) alternating urachal sinus. There is a common association with other genitourinary anomalies, urethral obstruction being the most common. Sonographically, continuity of an anterior abdominal wall mass with fetal bladder establishes the diagnosis of a yesicoallantoic cyst prenatally.
Renal cysts Cystic
These are not uncommon. Cysts may be simple or theca lutein cysts. Fetal theca lutein cysts are associated with maternal diabetes mellitus. Cysts may be unilocular or multiseptate. This is the most frequent cause of cystic lower abdominal mass in the female fetus. In utero torsion can occur.
· Wolffian duct cyst- Woifflan duct cysts arise as a result of cystic distension of imperfectly obliterated regions of the duct. They are only seen in female fetuses. Gartner’s duct (the terminal paravaginal portion of the Woiffian duct) is the most common site of cyst formation. The cysts are usually small. Diagnosis has been made antenatally at 33 weeks, when three communicating cysts were demonstrated.
· Cloacal dysgenesis- This is related to incomplete partitioning of the common cloaca and may give rise to septate pelvic mass or multiple thin walled cysts of varying sizes. There is association with other anomalies of the genitourinary tract, respiratory tract, CVS, skeletal system and anencephaly.
· Hydrocolpos/ hydrometrocolpos- A cystic mass arising from the pelvis. Duplication of the vagina and uterus may result in a multiseptate configuration. Associated anomalies include hydronephrosis, bowel obstruction due to extrinsic compression, TOF, esophageal and duodenal atresias and malrotation. May cause PH, but OH may occur with urinary tract obstruction.
Adrenal cyst/ hemorrhage
Retroperitoneal cysts are similar to other abdominal cysts of mesenteric and bowel origin, and frequently cannot be differentiated from these on US. They usually lie in the midabdomen.
Umbilical Vein Masses
Dilated umbilical vein
Umbilical vein varices
vIeconium distended rectum
Meconium in sigmoid colon
Masses Related to Spine/Sacrum