Solid Abdominal Masses in the Fetus
· Normal bowel- This appears hyperechoic before 20 weeks.
· Bowel masses- Causes include hyperechoic meconium (normal variant) meconium
ileus, bowel obstruction with inspissated contents and meconium filled rectum (a
pseudomass). Cystic fibrosis should be considered. Echogenic
bowel also described in trisomy 21 and IUGR.
· Renal masses- Infantile (autosomal recessive) polycystic kidney disease, Wilms’ tumor, dysplastic kidney, hamartoma, mesoblastic nephroma, ectopic kidney.
· Noramla adrenal gland- The fetal adrenal glands are relatively large in the third trimester and at birth are 20 times larger than in adult relative to body size. They are readily visualized in pregnancy as a bilaminar structure. The adrenal gland may be confused with a kidney in renal aplasia, particularly before 24 weeks.
· Sacrococcygeal- These often protrude outwards from the fetal surface. An intrapelvic extension is common. They may be cystic or solid, the risk of malignancy being greater in solid lesions.
· Hepatic masses- These include hepatoblastoma, hepatoma, hamartoma, hemangioma, metastases, hemangioendothelioma and heptomegaly of any etiology.
· Neuroblastoma- Neuroblastomas may occur anywhere along the sympathetic chain but the most common site is the adrenal gland. They may be solid or cystic.
· Splenomegaly- Fetal splenomegaly is a common finding in rhesus isoimmunization and transpiacental infections .
· Chordoma- Arising from remnants of the primitive notocord, these are rare tumors found in the sacrococcygeal and suboccipital regions of the spine; they are solid tumors.
· Cystic mass with solid appearance on US- These are masses with internal hemorrhage or debris within them. Abdominal cystic hygroma can on rare occasions have a solid appearance on US.
· Ovarian masses- Functional cysts are by far the most common ovarian masses in the fetus. Other ovarian masses which may occur in the ovary and may be solid are teratomas/ dermoids.
· Meningocele- Anterior meningocele is rare in the lower spine but may occur in the presacral region and is usually cystic. Solid elements within the cyst may represent glial tissue or lipoma.
· Pulmonary sequestration- Extrathoracic pulmonary sequestration is reported to occur below the diaphragm. This has been reported in utero as a cause of solid upper abdominal masses.