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Case Report |
1 Department of Pediatrics, The University of California at San Francisco and
The Cardiovascular Research Institute, San Francisco, CA 94143.
2 Department of Radiology, The University of California at San Francisco, Box
628, San Francisco, CA 94143.
Received May 24, 2002; accepted after revision July 29, 2002.
Address correspondence to C. B. Higgins.
Case Report
The patient was a full-term male delivered by emergent cesarean section because of placental abruption and no fetal heart tones. At birth, the patient had respiratory distress that required intubation. A chest radiograph revealed minimal aeration in the right hemithorax, with a normal-appearing left lung and a normally placed mediastinum (Fig. 1A). Thoracic sonography showed the liver in the right hemithorax; this sonographic finding led to the presumptive diagnosis of congenital diaphragmatic hernia. The patient was transported to our institution for surgical repair.
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We thought that the unusually large amount of liver in the right hemithorax and the lack of mediastinal shift were atypical for congenital diaphragmatic hernia. Primary right lung hypoplasia with an intact diaphragm was considered as an alternative diagnosis. Hepatic pulmonary fusion was also considered but thought less likely because of its rarity. The patient developed progressive hypoxemia and suprasystemic pulmonary hypertension that required treatment with inhaled nitric oxide. These clinical findings were consistent with all the diagnoses being considered, so after the patient's condition had stabilized, MR imaging and MR angiography of the thorax were performed to visualize the pulmonary arteries and to attempt to image the right hemidiaphragm.
MR imaging showed a small hypoplastic right lung (Fig. 1B). The right pulmonary artery was hypoplastic, measuring 0.5 mm, whereas the left pulmonary artery measured 5.0 mm (Figs. 1C and 1D). The diaphragm could not be identified. However, near the dome of the liver, a band of tissue with greater contrast enhancement (gadopentetate dimeglumine) than the liver was visible. This signal intensity pattern was considered characteristic of atelectatic lung. The enhancing tissue conformed to the dome of the liver and was inseparable from the liver (Figs. 1C and 1D). Moreover, several veins could be seen draining from this band of enhancing tissue into the intrahepatic inferior vena cava (Fig. 1E).
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The patient underwent right thoracotomy for repair of congenital diaphragmatic hernia. An anterior rim of diaphragm and most of the liver were found in the hemithorax. Two right lung lobes were evident, and the lower lobe was fused to the liver. This fusion prevented reduction of the liver. The upper lobe was small and was therefore resected. The liver and residual fused lung were reduced into the abdomen. A Surgisis prosthetic patch (Cook Biotech, West Lafayette, IN) was used to close the defect.
The patient was extubated on postoperative day 18 (day of life 26). He was discharged from the hospital on day of life 85; diuretic therapy and supplemental oxygen were continued.
Discussion
The unique finding on MR imaging in this case was tissue with enhancement suggestive of atelectatic lung; however, the shape of the tissue conformed to the liver contour, and the tissue was inseparable from the liver. Moreover, this enhancing tissue had venous drainage to the intrahepatic inferior vena cava, which made the tissue further appear intrahepatic. These findings may be diagnostic of hepatic pulmonary fusion.
Previous reports of this anomaly have described fibrous tissue at the lung—liver interface [1, 2], and a report of a late-presenting left congenital diaphragmatic hernia described "inflammatory" hepatic pulmonary fusion [4]. This MR imaging finding, atelectatic lung that is adherent to the dome of the liver, likely represents a unique feature of hepatic pulmonary fusion.
It is important to consider hepatic pulmonary fusion in the differential diagnosis when congenital diaphragmatic hernia is considered as the cause of respiratory distress in the newborn, because the surgical repair is more complicated than that of congenital diaphragmatic hernia. With hepatic pulmonary fusion, the inability to separate liver and lung tissue makes reduction of the hernia and preservation of the lung difficult [1, 2]. Repair of hepatic pulmonary fusion also carries a high risk of intraoperative and postoperative hemorrhage. If unique MR features are evident preoperatively, surgeons may be able to plan surgery more appropriately.
Hepatic pulmonary fusion should be suspected in a neonate with imaging findings that reveal a large amount of liver in the right hemithorax and a lack of mediastinal shift. Hepatic pulmonary fusion with a right-sided diaphragmatic defect has been described in the literature as a single case report [2] and a series of six cases [1]. As in our case, five of the six cases in the series reported lack of shift of mediastinal structures away from the affected side on the initial chest radiograph. This finding suggests that in patients with hepatic pulmonary fusion, pulmonary hypoplasia predominates over the mass effect from the herniated abdominal viscera. This radiographic feature is similar to those of primary lung hypoplasia with an intact diaphragm (e.g., scimitar syndrome) [3]. In contrast, in patients with congenital diaphragmatic hernia, the mass effect from the viscera causes a mediastinal shift. Further complicating the preoperative diagnosis in this case was the severe pulmonary hypertension experienced by our patient, which is a frequent occurrence in all of the diagnoses under consideration.
The relationship of hepatic pulmonary fusion to congenital diaphragmatic hernia is unclear. Hepatic pulmonary fusion may, in fact, have the same primary abnormality as that of congenital diaphragmatic hernia: a lack of development of the embryonic diaphragm [5]. This failure allows the abdominal viscera to herniate into the thorax during the 10th week of gestation. Subsequent fusion of the liver and lung, resulting in hepatic pulmonary fusion, may occur through an event later in gestation. On the other hand, the primary abnormality in hepatic pulmonary fusion may be the fusion of the liver and lung, both of which are derivatives of the embryonic foregut, and the lack of development of embryonic diaphragmatic structures may be secondary.
In summary, in a neonate with imaging findings showing intrathoracic liver and lack of mediastinal shift, hepatic pulmonary fusion should be suspected, as should primary right lung hypoplasia and the more common cause—congenital diaphragmatic hernia. In these cases, MR imaging may allow the preoperative diagnosis of hepatic pulmonary fusion by the depiction of enhancing tissue within the contour of the liver and with intrathoracic venous drainage to the intrahepatic inferior vena cava.
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