Discussion
As reported in the literature, all cases but one have been right sided.
Treatments have included antenatal steroids, fetal pneumonectomy, fetal
thoracoamniotic shunt placement, observation and elective
termination2-6. Only three of the ten reported cases
survived to delivery but none survived past day one of life. One had
undergone fetal thoracoamniotic shunt at 23 weeks GA, was delivered at
25 weeks GA3. Another had a pneumonectomy at 21 weeks
GA and delivered at 24 weeks GA2. The third underwent
fetal pneumonectomy at 26 weeks GA, and was delivered at 32 weeks
GA5.
In all cases, the atretic MSB caused hyperexpansion of the ipsilateral
lung, and compression of the contralateral lung in utero. Although fetal
pneumonectomy theoretically allows the uninvolved lung time to grow and
compensate, this did not occur likely secondary to prematurity. Here,
the right lung distal to the atretic MSB was hyperexpanded but later
collapsed (Figure 1A and 1B), with evidence of retained secretions and a
normal bronchial branching pattern, allowing the left lung to function,
albeit with significant mediastinal shift and consequent hemodynamic
changes. We hypothesize that atresia at the mainstem level initially
caused significant hyperexpansion on the right side, with mediastinal
shift to the left, and a consequent developmental abnormality of the
(short) LPA. At some point, the elevated pressure of lung fluid in the
right bronchial tree presumably resulted in the formation of a fistulous
connection, allowing decompression of the hyperexpanded right lung. The
small fistula would have then collapsed under lower pressure and closed
later in the 3rd trimester when the fetal lungs are not producing high
volumes of fluid, leaving behind a 5 mm long fibrous attachment between
the trachea and MSB. Postnatally, ventilation and expansion of the left
lung further collapsed the right lung with worsening mediastinal shift.
This exacerbated the stretching of the developmentally short LPA, with
consequent narrowing of the stretched vessel and elevation of RVP. Slide
tracheobronchoplasty allowed re-expansion of the right lung with
mediastinal normalization, lessened the stretch and narrowing of the
LPA, lowered the vascular resistance in the newly aerated lungs, with
normalization of the RVP.
Slide tracheobronchoplasty for isolated bronchial pathology is a rare
operation. The absence of bronchial cartilage causing a ball-valve
effect and obstruction of the right MSB is the usual indication. This is
a rare case of MBA successfully treated with slide tracheobronchoplasty
following spontaneous resolution of fetal hydrops. Our management and
surgical approach preserved his entire right lung and maximized the
possibility of a long-term favorable outcome without the complications
associated with pneumonectomy.Acknowledgement
We acknowledge Christine Schuler MD and Stephanie Merhar MD for their
edits of the manuscript.