The persisting pneumatoenteric recess and the infracardiac bursa: possible role in the pathogenesis of right hydrothorax complicating peritoneal dialysis.

Hydrothorax, an uncommon complication of peritoneal dialysis (PD), results from the migration of dialysis fluid under pressure from the peritoneal cavity into the pleural space. The exact site of the transdiaphragmatic fluid leak remains obscure, but the right-sided predominance of the hydrothorax points to the presence of abnormalities in the right hemidiaphragm. Such abnormalities have occasionally been described. In a recent case of acute massive right hydrothorax at the start of PD, the autopsy revealed extensive changes of amyloidosis that were comparable in both hemidiaphragms, prompting us to revisit the accepted explanation for right hydrothorax. We propose that an embryonic remnant--namely, the persisting pneumatoenteric recess and the infracardiac bursa--provides a passage connecting the peritoneal cavity to the right pleural space. The potential presence of this mechanism is consistent with the recognized clinical features of right hydrothorax complicating PD. This proposed route for dialysis fluid to form a right hydrothorax during PD can be investigated by currently available high-definition imaging techniques. This novel mechanism may also be involved in the pathogenesis of right hydrothorax observed in other medical conditions with tense ascites (liver cirrhosis, Meigs syndrome).