BOCHDALEK HERNIA

• Diagnosis may be made as early as 18 weeks menstrual age (1), but in about 50% of cases the hernia may not be evident prior to 24 weeks.
• Comprises >90% of all diaphragmatic abnormalities.
• Occurs posterolaterally through open pleuroperitoneal reflections (thought to be due to failure of the pleuroperitoneal canal to close due to an early insult at 9-10 weeks of gestation).
• 80% are on the left, 15% are on the right and 5% are bilateral (1,2). Male:Female ratio is 2:1.
• Prevalence (including stillborn fetuses) – 1:2200 births (9).
• Usually sporadic (however maternal ingestion of doxylamine-pyridoxine, thalidomide, quinine and anti-epileptic drugs have been reported in association) with no recurrence risks, however rare familial cases have been described (10).
• Pattern of inheritance is thought to be multifactorial.

Review Articles on anomalies and prognosis of diaphragmatic hernia.

ASSOCIATED ANOMALIES

Link to Anomalies associated with Bochdalek hernias

ULTRASOUND

• Increased nuchal translucency in the first trimester may be the first indirect sign that a diaphragmatic hernia is present.
• Solid or multicystic complex chest mass.
• Contents of the hernia.
• Bowel (especially with left sided lesions). Peristalsis of bowel within the fetal chest confirms the diagnosis, however this finding is not always present.

• Left sided hernias contain small intestine (88%), stomach (60%), colon (56%), liver (51%), gallbladder, spleen (45%), kidney (22%), pancreas (24%) or omental fat less commonly (2-4).

• Right sided hernias usually contain liver or gallbladder.
• Mediastinal shift due to the herniated viscera, however the heart usually retains its normal axis despite being shifted to the contralateral side.

• Identification of an intact diaphragmatic outline does not exclude the diagnosis.

• Fetal stomach at the level of the heart.

	Note the stomach, represented by a large gas lucency in the left chest cavity. Although it looks anteriorly situated on the lateral film the defect was situated posteriorly at surgery. There is marked mediastinal shift present.

• “Paradoxical motion” of the diaphragm – descent of the diaphragm on the normal side with ascent of abdominal contents on the abnormal side. This sign only occurs at the level of the hernia i.e. if you scanned anterior to the defect you would see normal diaphragmatic motion. Normally both diaphragms descent during inspiration, however, increased intra-abdominal pressure during inspiration forces intra-abdominal contents into the chest through the defect. The normal side descends at the same time resulting in a “rocking motion”. This sign may also be demonstrated in diaphragmatic eventration.
• Color and power doppler should be used to localize the umbilical hepatic and portal veins to localize the position of the liver. Power doppler may also localize the position of the superior mesenteric artery to localize the position of the bowel loops. Whenever the stomach is in the posterior or mid thorax, a careful search should be made to assess whether there is liver in the chest.

• Indirect signs.
• Non visualization of the stomach or gallbladder within the abdomen.
• Abnormal position of the stomach, gallbladder, hepatic or umbilical veins within the abdomen (fetal stomach at the level of the heart).
• Scaphoid shape of the abdomen due to the herniation of abdominal viscera into the chest.
• Paradoxical motion of the abdominal contents into the ipsilateral hemithorax during fetal respiratory motion, with concomitant descent of non-herniated contralateral abdominal contents.
• Polyhydramnios (usually develops during the third trimester) (5,6). This is thought to be due to either kinking of the stomach, extrinsic compression of the esophagus or reduced absorption of fluid by the hypoplastic lungs.
• CT amniography (swallowed fetal intestinal contrast in the chest) confirms the diagnosis.

Bochdalek Hernia (on the left side) Stomach bubble in the chest cavity at the level of the heart. Dextraposition of the heart into right chest cavity. Mesocardia (axis alteration of heart).

Video clip of Bochdalek Hernia

 PROGNOSIS

• Poor prognostic factors include:
• Diagnosis prior to 25 weeks of gestation.
• Liver herniation (7).
• Right lung-head ratio (LHR) in left sided diaphragmatic defects represents a two dimensional area of the right lung taken at the four chamber view of the heart divided by the head circumference. This ratio provides an index of the relative amount of contralateral lung in left sided diaphragmatic defects which is independent of gestational age. A low healthy lung-to-head ratio if it is a left sided lesion (8) has been shown to be a reliable predictor of outcome (11):
• Length multiplied by width of the right lung (healthy lung) = right lung area.
• Divide the right lung area by the value of the head perimeter.
• If the ratio is 1 or less the prognosis is extremely poor (despite the patient receiving ECHMO post birth).
• Ratios of 1.0 to 1.4 is associated with a 38% survival, however the majority require ECHMO.
• A ratio of above 1.4 is associated with a better prognosis.
• Overall survivors have a ratio of 1.4 +/- 0.33 and non-survivors 1.05 +/- 0.3

Right lung area = 22X13 = 286 mm Head circumference = 279 mm Lung-to-head ratio = 286/279 = 1.03. Fetal demise despite ECMO.
Right lung area = 31X20 = 620mm Head circumference = 288 mm Lung to head ratio = 620/280 = 2.2 Survival with good outcome.

REFERENCES

1. Benacerraf BR, Greene MF. Congenital diaphragmatic hernia: US diagnosis prior to 22 weeks gestation. Radiology 1986;158:809-810.
2. Adzick NS, Harrison MR, Glick PL et.al. Diaphragmatic hernia in the fetus: prenatal diagnosis and outcome in 94 cases. J Pediatr Surg 1985;20:357-361.
3. Cullen ML, Klein MD, Philippart AI. Congenital diaphragmatic hernia. Surg Clin N Am 1985;65:1115-1138.
4. Abrahim-Zadeh R, Coleman B. The role of color doppler ultrasonography in obstetrics. Semin Roentgenol 1998;34(4):351-359.
5. Comstock CH. Normal fetal heart axis and position. Obstet Gynecol 1987;70:255-259.
6. Chinn DH, Filly RA, Callen PW et.al. Congenital diaphragmatic hernia diagnosed prenatally by ultrasound. Radiology 1983;148:119-123.
7. Albanese CT, Lopoo J, Goldstein RB et.al. Fetal liver position and perinatal outcome for congenital diaphragmatic hernia. Prenat Diagn 1998;18(11):1138-1142.
8. Lipshitz GS, Albanese CT, Feldstein VA et.al. Prospective analysis of lung-to-head ratio predicts survival for patients with prenatally diagnosed congenital diaphragmatic hernia. J Pediatr Surg 1997;32(11):1634-1636.
9. Harrison MR, deLorimier AA. Congenital diaphragmatic hernia. Surg Clin North Am 1981;23:1114-1116.
10. Crane JP. Familial congenital diaphragmatic hernia: prenatal diagnostic approach and analysis of twelve families. Clin Genet 1979;16:244-248.
11. Metkus AP, Filly RA, Stringer MD et.al. Sonographic predictors of survival in fetal diaphragmatic hernia. J Pediatr Surg 1996;31:148-151.