ULTRASOUND OF DIAPHRAGMATIC HERNIA

• 85-95% are left sided.
• 97% are unilateral (1).
• Herniation of abdominal viscera into the thorax usually occurs at about 12 weeks when the intestines return from the physiological hernia in the umbilical cord, but this may be delayed until the second or third trimester (2).
• Echolucent mass, created by the fluid filled stomach, is usually seen adjacent and slightly posterior to the fetal heart.
• Ultrasound diagnosis of an intact diaphragm does not exclude the diagnosis.
• Breathing movements are usually present and normal in fetuses with diaphragmatic hernia in the early stages however may decrease significantly one fixation of the hernial sac occurs.
• Initially these hernias tend to "slide" resulting in a variation in the contents of the hernial sac and rare transient disappearance of the hernia. This tends to occur in the less mature fetus however eventual fixation occurs (from adhesions, increased size of the sac contents both from normal growth, partial occlusion and relative hypoplasia of the abdominal cavity).
• Left-sided congenital diaphragmatic hernias (3,4).
• Cystic mass in the chest (the visualization of peristalsis within the mass is diagnostic).
• Deviation of the heart to the right.
• No fluid filled stomach in the abdomen.
• Polyhydramnios.
• Scaphoid abdomen.

Contents of the hernial sac include bowel, liver (left lobe), spleen and left kidney.

• Right-sided congenital diaphragmatic hernias.
• More difficult to visualize because the echogenicity of the displaced liver is similar to that of the lung (5).
• The hepatic interlobar fissure may mimic the diaphragm in right-sided congenital diaphragmatic hernias (6).

Unilateral right-sided lesions usually contain only the fetal liver, but large defects may also contain portions of the stomach and small bowel.

• Mild polyhydramnios.
• Fetal nuchal translucency may be increased at 10-14 weeks (37% of cases in one series) (7).

REFERENCES

1. Sohaey R, Zwiebel WJ. The fetal thorax: Non cardiac chest anomalies. Semin Ultrasound, CT, and MRI 1996;17(1):34-50.
2. Bronshtein M, Lewit N, Sujov P et.al. Prenatal diagnosis of congenital diaphragmatic hernia: timing of visceral herniation and outcome. Prenat Diagn 1995;15:695-698.
3. Chinn DH, Filly RA, Callen PW et.al. Congenital diaphragmatic hernia diagnosed prenatally by ultrasound. Radiology 1983;148:119-123.
4. Comstock CH. The antenatal diagnosis of diaphragmatic anomalies. J Ultrasound Med 1986;5:391-396.
5. Comstock CH. Normal fetal heart axis and position. Obstet Gynecol 1987;70:255-259.
6. Sherer DM, Abramowicz JS, D'Angio et.al. Hepatic interlobar fissure sonographically mimicking the diaphragm in a fetus with right congenital diaphragmatic hernia. Am J Perinatol 1993;10:319-322.
7. Sebire NJ, Snijders RJM, Davenport M et.al. Fetal nuchal translucency thickness at 10-14 weeks of gestation and congenital diaphragmatic hernia. Obstet Gynecol 1998: in press.