Echogenic masses and calcifications in the fetal abdomen are observed relatively commonly during fetal sonography. These findings may arise from the liver, gallbladder, kidneys, adrenal glands, gastrointestinal tract, and/or peritoneal cavity. Although some of these findings carry few consequences, others are important for diagnosis of disorders affecting management of pregnancy, delivery, and the neonate.
When an echogenic mass is seen in the fetal abdomen, it is important to assess the location of the mass (is it in the stomach, intimately associated with bowel, or immediately below the diaphragm?), echogenicity (is it as bright as bone, is it heterogenous in echogenicity, or does it appear calcified with shadowing?), and the nature of the arterial and venous supply, if any, to the region of suspected abnormality. Assessing these features will aid in establishing a reasonable differential diagnosis for the sonographic finding, which will aid in planning care of the pregnant patient and her fetus.
ECHOGENICITY IN THE GASTROINTESTINAL TRACT
Gastric pseudo-mass — In the second and third trimesters, debris is commonly visualized in the fetal stomach as a pseudo-mass consisting of discrete echogenic areas 4 to 12 mm in diameter (image 1) . The pseudo-mass is thought to represent swallowed cells (red blood cells, meconium, fetal skin cells) that have aggregated due to relatively poor gastric peristaltic activity early in the second trimester [1,2]. Gastric pseudo-masses resolve over time and are not associated with adverse neonatal outcome.
Echogenic bowel — Echogenic bowel is the most common echogenic mass visualized in the fetal abdomen, with an incidence of 0.5 to 1 percent in the second trimester in a general obstetrical population [3-6].
By definition, the bowel is termed echogenic if on ultrasound examination it is as bright as adjacent bone; the iliac wing is the usual standard for comparison (image 2). Hyperechogenicity can be diffuse or focal, is uniform over a well-defined area that does not shadow, and is located primarily in the lower fetal abdomen and pelvis.