diaphragmatic hernia
description
the development of the diaphragm is completed by the end of the tenth week and involves the fusion of 3 principal components:
- the transverse septum
- the dorsal mesentery
- the pleuroperitoneal folds and .
the transverse septum grows backwards to meet the dorsal mesentery and gives rise to the central portion of the diaphragm.the pleuroperitoneal folds extend posterolaterally to complete the development. delayed fusion of any of these components results in a diaphragmatic hernia.
the incidence is 1 in 2000 births.
posterolateral defects (bochdalek type hernias) are due to incomplete fusion of the pleuroperitoneal membrane while the less common anteromedial defects of morgagni are due to maldevelopment of the transverse septum.
about 75% of defects are left sided.
diagnosis
the presence of a paracardiac or intrathoracic paraspinous sonolucent structure which may demonstrate peristalsis or rugae is diagnostic.
the mass may appear cystic, containing bowel, or solid containing liver and is seen in a true transverse section of the chest at the level of the four chamber view.
diagnosis during the first trimester is unlikely.
the bochdalek form is the much more common type and is usually unilateral with a 5 fold greater preponderance for the left sided variety than for the right.
false positive diagnosis commonly occurs when the stomach appears to be at the level of the heart because of an oblique section through the chest is obtained rather than a true transverse section.
a false negative diagnosis occurs more frequently in association with right sided defects because of the similarity in echogenicity between lung and liver in the fetus.
polyhydramnios will alert the sonographer to the possibility of a structural abnormality and other anomalies must be looked for.
about 50% of cases of diaphragmatic hernias are associated with other malformations. three percent (3%) of these have chromosomal malformations as the primary problem and 4% are associated with fryns syndrome. the association with anomalies is highest (87%) when intrauterine growth restriction is present.
differential diagnosis
establishment of normalcy in the location of the stomach, liver with gall bladder and the heart are of major importance in the exclusion of any lesions that may suggest an intrathoracic mass effect.
- cystic adenomatoid malformation of the lung (caml) is the most common differential and is easily excluded if peristaltic bowel is present in the chest. the paradoxical motion of the abdominal contents seen in diaphragmatic hernia during fetal breathing is absent in caml.
- diaphragmatic eventration can often be confused with diaphragmatic hernia because of the abnormal elevation of the diaphragm into the chest with displacement of the abdominal contents. the finding of a normal abdominal circumference in diaphragmatic eventration may be the only distinguishing feature.
- bronchogenic cyst can be excluded from the differential diagnosis if no normally-located stomach is seen.
sonographic features
- echogenic lung lesion with or without peristalsis.
- paradoxical motion of abdominal contents during fetal inspiration.
- intrathoracic chest mass with bowel seen at the same level as the heart in the four chamber view of the chest.
- the heart is pushed to the right in left sided diaphragmatic hernia.
- mediastinal shift is common in the posterolateral hernias and left sided eventrations but not in anteromedial hernias.
- absent stomach in the upper abdomen.
- abdominal circumference is usually <2 s.d in posterolateral diaphragmatic hernia.
- polyhydramnios is a common feature.
associated syndromes
three percent (3%) of these have chromosomal malformations as the primary problem and 4% are associated with fryns syndrome.
the association with anomalies is highest (87%) when intrauterine growth restriction is present.