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Prenatal MR Imaging of Congenital Diaphragmatic Hernia

¹ Department of Radiology and Department of Surgery, University of California San Francisco, 505 Parnassus Ave., San Francisco, CA 94143-0628.
² Present address: Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St., Boston, MA 02115.
³ The Fetal Treatment Center, University of California San Francisco, San Francisco, CA 94143-0628.

Received September 9, 1999; accepted after revision November 1, 1999.

 
Address correspondence to F.V. Coakley.

Introduction

Top Introduction Major MR Imaging Findings... Ancillary MR Imaging Findings... Conclusion References

 
Congenital diaphragmatic hernia is a developmental defect in the posterolateral diaphragm with herniation of abdominal viscera into the thorax. The incidence is 1 in 3000-4000 live births. The overall mortality is 68%. The cause is unknown, but one third of cases are associated with chromosomal or additional anatomic abnormalities. These nonisolated cases have a mortality of 76% [1]. The morbidity and mortality in isolated cases is caused primarily by pulmonary hypoplasia, resulting from mechanical compression of the developing lungs. The prenatal diagnosis of congenital diaphragmatic hernia is usually established by detailed obstetric sonography. Accurate diagnosis is critical for parental counseling, especially with the development of in-utero therapeutic tracheal occlusion (which is believed to promote lung growth by retention of bronchial secretions with increased bronchoalveolar pressure and pulmonary volume) [2]. Sonography is partially limited by poor acoustic contrast between fetal lung and herniated abdominal viscera, a small field of view, beam attenuation in maternal adiposity, operator dependency, and sonographic mimics of congenital diaphragmatic hernias [3]. MR imaging is increasingly used as a supplement to obstetric sonography in complex fetal anomalies. Surface coils and rapid sequences allow high-resolution MR imaging without significant fetal motion artifact. The aim of this pictorial essay is to describe the prenatal MR imaging findings in congenital diaphragmatic hernias, with particular emphasis on how MR imaging can supplement sonography and aid in treatment.

Major MR Imaging Findings in Congenital Diaphragmatic Hernia

Top Introduction Major MR Imaging Findings... Ancillary MR Imaging Findings... Conclusion References

 
Left-Sided Congenital Diaphragmatic Hernia
Approximately 83% of congenital diaphragmatic hernias are left-sided. MR imaging shows stomach and bowel loops in the left hemithorax, above the expected position of the left hemidiaphragm (Fig. 1A,1B). The stomach is seen as a fluid-filled gastric-shaped structure of low T1 and high T2 signal intensities. Bowel loops appear as tubular serpiginous structures of either high or low T1 and T2 signal intensities. The variable signal intensity of the bowel is presumably caused by the presence or absence of meconium. Cardiomediastinal shift to the right and compression of both lungs are best seen on axial images. Fetal lungs are of relatively high T2 signal intensity (Fig. 1B) because they are filled with fluid.

View larger version (125K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A. —Left-sided congenital diaphragmatic hernia at 23 weeks' gestation. Coronal T1-weighted spoiled gradient-echo MR image (TR/TE, 140/4.2; flip angle, 70°) shows stomach (S) and multiple bowel loops (arrow) above expected position of left hemidiaphragm.

View larger version (160K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B. —Left-sided congenital diaphragmatic hernia at 23 weeks' gestation. Corresponding T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) also shows stomach (S) and multiple bowel loops (arrow) above left hemidiaphragm.

In 57% to 86% of left congenital diaphragmatic hernias, the herniated viscera include a portion of liver ("liver-up") [3, 4]. Assessment of liver position is of major clinical importance because isolated "liver-up" and "liver-down" congenital diaphragmatic hernias have a respective mortality of 57% and 7% [1, 4]. Fetal liver is of relatively high T1 and low T2 signal intensities. In "liver-up" congenital diaphragmatic hernias, herniated liver appears in the left hemithorax as tissue that is contiguous with and has the same signal characteristics as nonherniated liver (Fig. 2A,2B). In "liver-down" congenital diaphragmatic hernias, the liver remains inferior to the expected position of the left hemidiaphragm (Fig. 3A,3B). Coronal T1-weighted images are often particularly helpful for liver visualization. The position of the stomach in the chest, as seen on axial images, is an indirect indicator of liver position. As the liver herniates anteriorly, the stomach is displaced posteriorly (Figs. 4,5,6A,6B).

View larger version (139K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A. —Left-sided congenital diaphragmatic hernia at 26 weeks' gestation, with partial upward herniation of liver into left hemithorax ("liver-up" congenital diaphragmatic hernia). Coronal T1-weighted spoiled gradient-echo MR image (TR/TE, 140/4.2; flip angle, 70°) shows upward herniation of left hepatic lobe (arrow).

View larger version (129K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B. —Left-sided congenital diaphragmatic hernia at 26 weeks' gestation, with partial upward herniation of liver into left hemithorax ("liver-up" congenital diaphragmatic hernia). Corresponding T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) also shows upward herniation of left hepatic lobe (arrow). Note liver is more easily seen on T1-weighted images in A because of high T1 signal intensity.

View larger version (113K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A. —Left-sided congenital diaphragmatic hernia at 23 weeks' gestation, with no upward herniation of liver ("liver-down" congenital diaphragmatic hernia). Coronal T1-weighted spoiled gradient-echo MR image (TR/TE, 140/4.2; flip angle, 70°) shows liver (L) in normal position.

View larger version (130K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B. —Left-sided congenital diaphragmatic hernia at 23 weeks' gestation, with no upward herniation of liver ("liver-down" congenital diaphragmatic hernia). Corresponding T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) also shows liver (L) in normal position.

View larger version (147K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4. —Axial T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) shows "liver-up" left-sided congenital diaphragmatic hernia at 24 weeks' gestation. Stomach (S) is displaced posteriorly in left hemithorax because liver (L) herniates anteriorly. Stomach position in left hemithorax is indirect indicator of liver position. Note herniated bowel loops (B) posterior to stomach, Also note heart (asterisk) and right lung (arrow) shifted to right. Left lung is not seen.

View larger version (154K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5. —Axial T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) shows "liver-down" left-sided congenital diaphragmatic hernia at 25 weeks' gestation. Note stomach (S) lying anteriorly in left hemithorax (compare with Figure 4). Also note herniated bowel loops (B), heart (asterisk), and displaced right lung (arrow).

View larger version (133K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6A. —"Liver-up" left-sided congenital diaphragmatic hernia at 28 weeks' gestation. Sagittal T1-weighted spoiled gradient-echo MR image (TR/TE, 140/4.2; flip angle, 70°) of left hemithorax shows upward herniation of liver, confirming diagnosis. Stomach (S) is displaced posteriorly by anteriorly located liver (L).

View larger version (130K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6B. —"Liver-up" left-sided congenital diaphragmatic hernia at 28 weeks' gestation. Sagittal T1-weighted spoiled gradient-echo MR image (140/4.2; flip angle, 70°) of right hemithorax shows liver (L) positioned normally inferior to right lung (asterisk).

Gastric distention is a recognized but unexplained finding in left-sided congenital diaphragmatic hernias (Filly RA, personal communication). On MR imaging, the gastric outlet often appears stretched, and this stretching may contribute to impaired gastric emptying (Fig. 7). Organoaxial volvulus of the herniated stomach has also been described [5] and can be recognized when the greater curvature is superior to the lesser curvature (Fig. 8).

View larger version (155K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7. —Left-sided congenital diaphragmatic hernia at 26 weeks' gestation. Sagittal T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) shows enlarged fluid-filled stomach (S) in left hemithorax. Note stretched and narrowed gastric outlet (arrow).

View larger version (149K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8. —Left-sided congenital diaphragmatic hernia at 33 weeks' gestation. Coronal T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) shows distended stomach (S). Note greater curvature (arrow) is superior to lesser curvature, consistent with organoaxial volvulus.

Right-Sided Congenital Diaphragmatic Hernia
Approximately 12% of all congenital diaphragmatic hernias are right-sided. Liver herniation is present in virtually all cases [3], and the terms "liver-up" and "liver-down" are not appropriate. On MR imaging, a right-sided congenital diaphragmatic hernia is characterized by liver tissue above the expected position of the right hemidiaphragm (Fig. 9A,9B). Herniated bowel is less frequently seen because liver frequently constitutes the entire hernia. A right-sided congenital diaphragmatic hernia has a mortality of 80% [1]. Fetal ascites, hydrothorax, and integumentary edema can be seen (Fig. 10A,10B) without true hydrops. Liver herniation in right-sided congenital diaphragmatic hernias may result in hepatic venous obstruction and ascites by a Budd-Chiari mechanism [6], whereas localized edema of the head and neck may be caused by an obstruction of the superior vena cava [7]. Fluid in the right hemithorax does not strictly constitute a pleural effusion because the diaphragmatic defect allows ascites to track freely into the chest. Ascites facilitates direct identification of the primary defect (Fig. 11A,11B), which otherwise is rarely seen directly.

View larger version (134K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9A. —Right-sided congenital diaphragmatic hernia at 29 weeks' gestation. Coronal T1-weighted spoiled gradient-echo MR image (TR/TE, 140/4.2; flip angle, 70°) shows upward herniation of right hepatic lobe (L). Large area of artifactual signal loss (asterisk) in root of neck is caused by therapeutic tracheal occlusion device.

View larger version (127K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9B. —Right-sided congenital diaphragmatic hernia at 29 weeks' gestation. Corresponding T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) shows right hepatic lobe (L) in chest and nonherniated stomach (S).

View larger version (179K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 10A. —Right-sided congenital diaphragmatic hernia with ascites and hydrothorax at 37 weeks' gestation. Sagittal T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) shows ascites (arrow) and right hydrothorax (asterisk).

View larger version (159K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 10B. —Right-sided congenital diaphragmatic hernia with ascites and hydrothorax at 37 weeks' gestation. Axial T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (infinite/100) shows free fluid (arrow) surrounding herniated right hepatic lobe (L).

View larger version (153K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11A. —Right-sided congenital diaphragmatic hernia at 31 weeks' gestation with diaphragmatic defect directly visualized. Sagittal T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) shows intact left hemidiaphragm (arrows) inferior to left lung (asterisk).

View larger version (151K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11B. —Right-sided congenital diaphragmatic hernia at 31 weeks' gestation with diaphragmatic defect directly visualized. Sagittal T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (infinite/100) shows herniation of liver (L) and bowel loops (B) between defective diaphragmatic ridges (arrows).

Bilateral Congenital Diaphragmatic Hernia
Approximately 5% of congenital diaphragmatic hernias are bilateral (Fig. 12A,12B,12C). Sonographic diagnosis is difficult because little or no mediastinal shift is present and because herniated liver can mimic lung tissue. MR imaging can readily identify herniated liver in both hemithoraces because of the characteristic differences in T1 and T2 signal intensities between lung and liver. A bilateral congenital diaphragmatic hernia is uniformly fatal [1].

View larger version (154K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 12A. —Bilateral congenital diaphragmatic hernia at 22 weeks' gestation. Diagnosis was suggested by sonography and confirmed by MR imaging. Coronal sonogram of fetal chest shows echogenic structures (white arrows) in both hemithoraces. Vascular pattern (black arrow) is atypical for pulmonary vessels and raises the consideration of bilateral congenital diaphragmatic hernia.

View larger version (162K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 12B. —Bilateral congenital diaphragmatic hernia at 22 weeks' gestation. Diagnosis was suggested by sonography and confirmed by MR imaging. Coronal fast spoiled gradient-echo T1-weighted image (TR/TE,140/4.2; flip angle, 70°) shows tissue of liver signal intensity (arrows) in both hemithoraces.

View larger version (176K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 12C. —Bilateral congenital diaphragmatic hernia at 22 weeks' gestation. Diagnosis was suggested by sonography and confirmed by MR imaging. Corresponding T2-weighted single-shot rapid acquisition with relaxation enhancement MR image (TR/effective TE, infinite/100) also shows tissue of liver signal intensity (arrows) in both hemithoraces.

Ancillary MR Imaging Findings in Congenital Diaphragmatic Hernia

Top Introduction Major MR Imaging Findings... Ancillary MR Imaging Findings... Conclusion References

 
Polyhydramnios occurs in 29% to 76% of cases [2], probably because of impaired fetal swallowing of amniotic fluid, and can be seen on MR imaging. However, polyhydramnios is principally diagnosed clinically and sonographically. The suggestion that polyhydramnios is associated with a poor outcome has not been confirmed by recent studies [3]. A wide spectrum of coexistent chromosomal or structural abnormalities may be seen. MR imaging is not an appropriate technique for fetal screening, for these anomalies are primarily revealed by detailed sonography, echocardiography, and amniocentesis. Nonetheless, associated abnormal findings are often apparent, and occasionally MR imaging can be used to confirm an equivocal sonographic finding. A specific but poorly understood association with congenital cystic adenomatoid malformation and extralobar sequestration suggests a common underlying pathophysiology [8].

Conclusion

Top Introduction Major MR Imaging Findings... Ancillary MR Imaging Findings... Conclusion References

 
Prenatal MR imaging can confirm the diagnosis of a congenital diaphragmatic hernia when sonographic findings are equivocal or atypical (Fig. 13A,13B), especially if therapeutic abortion or fetal surgery is being considered. MR imaging can also assess liver position, which can be difficult to evaluate sonographically. Finally, fetal lung volume can be directly measured by MR imaging planimetry, allowing confirmation and quantification of pulmonary hypoplasia (Coakley et al., presented at the annual meeting of the Radiological Society of North America, Chicago, November 1999). Lung volumetry may ultimately supplant sonographic assessment of pulmonary hypoplasia, which suffers from measurement variability and lack of predictive power in the middle range of values [4] and may also contribute to assessment of prognosis and treatment response after inutero intervention.

View larger version (99K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 13A. —Left-sided congenital diaphragmatic hernia at 21 weeks' gestation. Sonographic findings were equivocal, and MR imaging was used to establish diagnosis. Coronal sonogram through fetal chest shows echogenic structure (asterisk) in left hemithorax, raising possibility of "liver-up" left-sided congenital diaphragmatic hernia. However, stomach (arrow) is not in left hemithorax, as would typically be expected.

View larger version (120K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 13B. —Left-sided congenital diaphragmatic hernia at 21 weeks' gestation. Sonographic findings were equivocal, and MR imaging was used to establish diagnosis. Coronal fast spoiled gradient-echo T1-weighted image (TR/TE, 140/4.2; flip angle, 70°) shows herniated left hepatic lobe (L) in left hemothorax. Stomach (S) shows only partial upward displacement.

References

Top Introduction Major MR Imaging Findings... Ancillary MR Imaging Findings... Conclusion References

 

1. Adzick SN, Harrison MR, Glick PL, Nakayama DK, Manning FA, deLorimier AA. Diaphragmatic hernia in the fetus: prenatal diagnosis and outcome in 94 cases. J Pediatr Surg 1985;20:357 -361[Medline]
2. Harrison MR, Mychaliska GB, Albanese CT, et al. Correction of congenital diaphragmatic hernia in utero IX: fetuses with poor prognosis (liver herniation and low lung-to-heade ratio) can be saved by temporary tracheal occlusion. J Pediatr Surg 1998;33:1017 -1023[Medline]
3. Guibaud L, Filiatrault D, Garel L, et al. Fetal congenital diaphragmatic hernia: accuracy of sonography in the diagnosis and prediction of the outcome after birth. AJR 1996;166:1195 -1202[Abstract/Free Full Text]
4. Metkus AP, Filly RA, Stringer MD, Harrison MR, Adzick NS. Sonographic predictors of survival in fetal diaphragmatic hemia. J Pediatr Surg 1996;31:148 -152[Medline]
5. Beckmann KR, Nozicka CA. Congenital diaphragmatic hernia with gastric volvulus presenting as an acute tension gastrothorax. Am J Emerg Med 1999;17:35 -37[Medline]
6. Gilsanz V, Emons D, Hansmann M, et al. Hydrothorax, ascites, and right diaphragmatic hernia. Radiology 1986;158:243 -246[Abstract/Free Full Text]
7. Giacoia GP. Right-sided diaphragmatic hernia associated with superior vena cava syndrome. Am J Perinatol 1994;11:129 -131[Medline]
8. Ryan CA, Finer NN, Etches PC, Tierney AJ, Peliowski A. Congenital diaphragmatic hernia: associated malformations—cystic adenomatoid malformation, extralobar sequestration, and laryngotracheoesophageal cleft: two case reports. J Pediatr Surg 1995;30:883 -885[Medline]

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