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Congenital Diaphragmatic Hernia


Left Diaphragmatic Hernia
Right Diaphragmatic Hernia

Findings:

Transverse axial plane of sections demonstrate a left diaphragmatic hernia with stomach, liver and bowel within the left chest and the heart deviated to the right and in the second case on the right, a right diaphragmatic hernia with the liver and gallbladder (arrow) identified within the right chest. In both cases the amniotic fluid volume was normal and no other morphologic abnormalites were identified.

Discussion:

Congenital diaphragmatic hernia (CDH) is said to occur between 1 in 2000 to 1 in 5000 births. It results from failure of the pleuroperitoneal membrane to grow or fuse in the first trimester which causes a defect in the diaphragm and thus communication between the thoracic and abdominal cavity. In most series, left diaphragmatic hernia is 5 - 10 times more common than right CDH. As with all congenital malformations, the coexistence of associated abnormalities is high, between 29 - 53%. Abnormalites of virtually every organ system have been described, although congenital cardiac malformations are the most common and devastating. Likewise, the incidence of chromosomal abnormalities is high, varying between 5 - 16%. Most cases of aneuploidy are due to Trisomy 18. In the past several years it has been recognized that mosaicism for isochrosome 12p, Pallister-Killian syndrome is associated with CDH.This condition which is associated with hypotonia and mental retardation, may be missed if only fetal blood sampling is performed. Skin biopsy or fibroblasts from amniocentesis appear to be more accurate than blood lymphocytes in confirming the diagnosis.

The mortality for fetuses and neonates diagnosed with this condition is high ranging between 40 - 100%. (The nature of the patient population ie prenatal, neonatal, referral, screened, those terminated or with chromosomal or other morphologic abnormalities needs to be considered to accurately compare outcomes) Recent reports of populations of antenatally diagnosed isolated diaphragmatic hernia have shown survival rates of 50% - 60%. The dismal prognosis exists despite recent advances in postnatal management including improved methods of: ventilation, pharmacology, surgical repair as well as extracorporeal membrane oxygenation. The mortality in CDH is related to either to the presence of other associated congenital malformations or the development of pulmonary hypoplasia or persistent pulmonary hypertension. Patients with a large diaphragmatic hernia usually have a lung weight between 15% to 40% of expected weight.

Sonography is highly accurate in establishing the diagnosis. The hallmark of the diagnosis of left CDH is the absence of the stomach in the abdomen in the left upper quadrant in addition to the presence of stomach, bowel and liver in the left thorax associated with mediastinal shift. Right diaphragmatic hernia is diagnosed by evidence of hepatic vascualture or the gallbladder in the right hemithorax. There may be associated ascites, pleural effusion and mediastinal shift. Few false positive diagnoses of this condition are made, the most common from a transverse axial plane of section which is angled obliquely so that the stomach and heart appear to both reside within the thorax. False negative diagnoses result from: right CDH where the gallbladder is not identified, a small or reducible lesion, poor visibility due to oligohydramnios or maternal obesity or misinterpretation of another diagnostic abnormality (see below). High frequency transducers, color doppler flow imaging, intra-amniotic or intra-peritoneal saline as a contrast agent and computed tomography or magnetic resonance imaging have all been helpful in achieving an accurate diagnosis.

In the past several years, corrective in utero surgery has become available as another management option for patients with a diagnosis of CDH. In light of the potential for corrective surgery or the option of termination of pregnancy, numerous attempts have been made to accurately assess prognosis in these patients. A variety of findings have been described which have been said to be associated with a poor prognosis; these include: coexisting malformations, particularly cardiac anomalies, the diagnosis of this condition prior to 25 weeks, polyhydramnios, the presence of liver or stomach in the thorax and underdevelopment of the cardiac ventricular chambers.

The presence of liver in the thorax is common in patients with CDH. It is most accurately diagnosed by virtue of either identifying the gallbladder in the thorax, visualizing portal vessels crossing the region of the hemi-diaphragm or deviation and leftward bowing of the umbilical portion of the left portal vein. While the presence of liver in the thorax may not necessarily mean the prognosis is grave, its absence is a more reassuring sign. Neither polyhydramnios nor the presence of the stomach in the thorax has proven to be reliable in assessing prognosis. As these patients often succumb to pulmonary hypoplasia more recent efforts have centered upon assessing prognosis by virtue of the amount of identifiable pulmonary parenchyma on the contralateral side (usually right lung). While numerous techniques have been utilized, two more recently reported techniques appear both easy to perform and reasonably accurate. The first technique involves measuring the right lung area to head circumference ratio. The right lung area is measured at the level of the atria on a transverse axial scan of the fetal thorax. The area was calculated using a two-dimensional perpendicular linear measurement in millimeters. The area equaled the product of the longest two perpendicular linear measurements and this was expressed as a ratio to the head circumference. In this authors series, all fetuses with a ratio less than 0.6 died. Survival was 100% when the ratio was greater than 1.35. The other technique involves comparing the subjective assessment of right lung area to the right hemithorax area. Lung area was determined on a transverse axial plane of section at the level obtained to visualize the four cardiac chambers. Hemithorax area was obtained by drawing an antero-posterior line tangential to the border of the vertebral body on the same side of the quantified lung area. Fetuses with a ratio of lung area to hemithorax greater than 50% had a 86% survival whereas those with a ratio less than 50% had a 25% survival. Recently, Sbragia, Paek, Filly et al evaluated the prognosis of patients with congenital diaphgragmatic hernia when the liver had not herniated into the thorax. Their study was an attempt to determine the ability of the lung-to-head ratio to predict survival and need for extracorporeal membrane oxygenation support in fetuses with left congenital diaphragmatic hernia without herniation of the liver into the chest. The perinatal records of 20 fetuses with isolated left congenital diaphragmatic hernia without herniation of the left lobe of the liver into the chest were reviewed. Fetuses were stratified into two groups depending on lung-to-head ratio: those with a ratio of less than 1.4 (historically a poor prognosis group) and those with a ratio of greater than 1.4. The outcome of both groups was compared with chi-square analysis. Eight of 11 fetuses with a lung-to-head ratio greater than 1.4 survived, whereas 8 of 9 fetuses with a ratio of less than 1.4 survived. No differences were noted in the need for extracorporeal membrane oxygenation support or survival between the two groups. Their conclusion was that fetuses with a prenatally diagnosed left congenital diaphragmatic hernia without herniation of liver into the chest have a favorable prognosis even in the presence of a low lung-to-head ratio. While no technique is perfect, these methods and others like them allow the patient to better understand the prognosis and therapeutic options.

Rt. Lung Area Measurements

Hepatic + Portal Vein into Thorax

Deviation of Portal Vein

Chromosomal Abnormalities and Survival

During the past year a number of investigators have reported the utility of employing sonographically detected increased nuchal translucency thickness as part of screening programs to detect both chromosomal and morphologic abnormalities. A recent report by Sebire et al assessed the nuchal translucency in the first trimester in the evaluation of the patient with congenital diaphragmatic hernia. At the 10-14 week scan, the fetal nuchal translucency was above the 95 centile for crown-rump length in seven (37%) of 19 cases of CDH, including 5 of 6 (83%) of those resulting in neonatal death. Thus neonatal death occurred in five (71%) of seven cases with increased nuchal translucency compared with one of eight cases (13%) with normal nuchal translucency.

The authors conclusion based upon their results is that the prevalance of congenital diaphragmatic hernia in chromosomally normal fetuses is about one in 4000, nearly 40% of affected fetuses have increased nuchal translucency at 10-14 weeks and that increased nuchal translucency is a marker of intrathoracic compression-related pulmonary hypoplasia. While the explanation for the association of increased nuchal translucency and pulmonary hypoplasia is not known with certainty, it is postulated that large hernias with lung and mediastinal compression may result in impedance of venous return with congestion of blood vessels in the head and neck. Thus those patients without increased nuchal translucency may either have less severe diaphragmatic hernias or not develop them until the late second and third trimesters. The impact of this finding on the management of these patients will have to be assessed by more and continuing studies. A recent meta-analysis by Geary et al reported the incidence of chromosomal abnormalities and survival in centers reporting 25 or more cases.

Published Studies of Congenital Diaphragmatic Hernia; Comparing Incidence of Chromosomal Abnormalities and Survival

Authors
Number
Chr. Abnl (n)
Chr. Abnl (%)
% Survival - Overall
% Survival < 24 weeks
% Survival >24 weeks
% Survival - Isolated Cases

Thorpe-Beeston et al (1989)

36
11
31
25
Not Assessed
Not Assessed
60

Adzick et al (1989)

38
6
16
24
0
38*
38

Sharland et al (1992)

55
2
4
27
26
40
28

Manni et al (1994)

28
3
11
14
0
100**
30

Bollman et al (1995)

33
6
18
18
Not Assessed
Not Assessed
44

Dommergues et al (1996)

135
14
10
19
Not Assessed
Not Assessed
30

Howe et al (1996)

48
13
34
27
24
30
50

Geary et al (1998)

34
5
15
18
31
33
38
Total
407
60
15
22
16
48
40
*Cases diagnosed at > 25 weeks gestation, ** - cases diagnosed at > 32 weeks gestation

From: Geary MP, Chitty LS, Morrison JJ, Wright V, Pierro A, Rodeck CH. Perinatal outcome and progostic factors in prenatally diagnosed congenital diaphragmatic hernia. Ultrasound Obstet Gynecol 12:107-111, 1998

Differential Diagnosis:

Any abnormality resulting in either a solid mass or cyst within the fetal thorax can be confused with a CDH. Cystic adenomatoid malformation (all of its Types), pulmonary sequestration, bronchogenic cysts and teratomas may all simulate a CDH. Likewise CDH may simulate these lesions. It should be remembered that these lesions may often coexist, making accurate diagnosis often quite difficult.

CDH Simulating CCAM
CDH + Sequestration

Systemic Flow to Sequestration

 

References:

Cannon C, Dildy GA, Ward R, Varner MW and Dudley DJ. A population -based study of congenital diaphragmatic hernia in Utah: 1988-1994 Obstet Gynecol 87:959-963, 1996

Metkus AP, Filly RA, Stringer MD, Harrison MR and Adzick NS. Sonographic predictors of survival in fetal diaphragmatic hernia.

Bootstaylor BS, Filly RA, Harrsion MA et al. Prenatal sonographic predictors of liver herniation in congenital diaphragmatic hernia J Ultrasound Med (in press)

Guibaud L, Filatrault D, Garel L, Grignon A et al. Fetal congenital diaphragmatic hernia: Accuracy of sonography i the diagnosis and prediction of the outcome after birth. Amer J Roentgenol 166:1195-1202, 1996

Donnenfeld AE, Campbell TJ, Byers J, Librizzi RJ and Weiner S. Tissue-specific mosacism among fetuses with prenatally diagnosed diaphragmatic hernia. Am J Obstet Gynecol 169:1017-21, 1993

Wenston KD, Weiner CP and Hanson JW. A five-year statewide experience with congenital diaphragmatic hernia. Am J Obstet Gynecol 165:838-842, 1991

Sebire NJ, Snijers RJM, Davenport M, Greenough A, Nicolaides KH. Fetal Nuchal Translucency Thickness at 10-14 Weeks' Gestation and Congenital Diaphragmatic Hernia Obstet Gynecol 90:943-6, 1997

Geary MP, Chitty LS, Morrison JJ, Wright V, Pierro A, Rodeck CH. Perinatal outcome and progostic factors in prenatally diagnosed congenital diaphragmatic hernia. Ultrasound Obstet Gynecol 12:107-111, 1998

Sbragia L, Paek BW, Filly RA, Harrison MR et al Congenital Diaphragmatic Hernia Without Herniation of the Liver: Does the Lung-to-Head Ratio Predict Survival? J Ultrasound Med 19:845-848, 2000

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Peter W. Callen, M.D.
Professor of Radiology, Obstetrics, Gynecology and Reproductive Science
University of California Medical Center, San Francisco, California