An Unusual Cause of Pleural Effusion

A 36-year-old man presents with a 10-day history of progressive dyspnea anddiscomfort on the left side of his chest.Three weeks earlier, he was dischargedfrom the hospital after a 2-week stayfor acute pancreatitis. He has a historyof long-term alcohol abuse and recurrentpancreatitis.The patient is afebrile. Heart rateis 115 beats per minute; blood pressure,150/85 mm Hg; and respirationrate, 20 breaths per minute. Chest examinationreveals an absence of breathsounds on the left side, with dullnessto percussion.The serum amylase level is 938U/L (normal, 25 to 125 U/L); lipase,605 U/L (normal, 7 to 60 U/L); andalanine aminotransferase, 7 U/L(normal, 10 to 60 U/L). Alkalinephosphatase, aspartate aminotransferase,total bilirubin, and albuminlevels are normal. Analysis of the pleuralfluid after thoracentesis reveals thefollowing values: pH, 10; glucose,39 mg/dL; amylase, 38,192 U/L;lipase, 35,867 U/L; and white bloodcell count, 637/μ L.The chest film reveals a large, leftsidedpleural effusion (Figure 1). ACT scan of the abdomen confirms thisfinding and shows the effusion, witha small amount of peripancreatic fluid,and a small pseudocyst near the headof the pancreas (Figure 2).Conservative management withtotal parenteral nutrition (TPN) andintravenous octreotide is initiated.During the next few days, pleural fluidreaccumulates, and thoracentesis isperformed again.Endoscopic retrograde pancreatography(ERP) reveals a normal biliaryduct, with no stones or strictures. However,the pancreatogram shows a fistuloustract arising from the area ofthe pancreatic head and running uptoward the diaphragm (Figure 3). Becauseof technical difficulties related tothe anatomy of the pancreatic ductin the pancreatic head, stenting of theduct is not achieved, despite repeatedattempts. Recurrent accumulation ofpleural fluid requires another thoracentesis;surgery is planned.A Roux-en-Y cyst-jejunostomy isperformed successfully, and the patient'shospital course is uneventful. Eight daysafter surgery, a chest tube placed duringthe procedure is removed, and he is discharged.Two weeks later, the effusionhas not recurred.PATHOGENESISPleural effusion can develop inthe setting of acute pancreatitis. Theincidence varies from 3% to 17%. The effusions are frequently small andleft-sided and are thought to be lymphaticor sympathetic in origin.¹Pleural effusion associated withchronic pancreatitis and a pseudocystis less common. In this setting, theeffusion results from pancreatic ductdisruption or pancreatic pseudocystextension to the pleural cavity. Pancreatic-pleural fistula secondary tochronic pancreatitis is a rare causeof recurrent pleural effusion.²When the pancreatic duct rupturesduring pancreatitis, the omentumand adjacent structures containthe site of inflammation. However,when less inflammation is present,as in chronic pancreatitis, the fluidfollows the path of least resistance.Anterior rupture results in pancreaticascites (pancreatic-peritoneal fistula),whereas in posterior rupture, thefluid tracks to the mediastinum, usuallythrough the esophageal or aortichiatus. Once in the mediastinum, thepancreatic secretions may breakthrough to one or both of the pleuralspaces to form a chronic pancreaticpleuraleffusion.³DIAGNOSISPancreatic-pleural fistula is reportedmostly in men with chronicalcoholism. Pancreatic pseudocystoccurs in 69% to 77% of patients withpancreatic-pleural fistula.⁴The presentation of pancreaticpleuralfistula is often confusing, becauseof the predominance of pulmonarysymptoms and the relativeabsence of abdominal complaints. Afistula should be considered when anew left-sided effusion develops ina patient with a history of pancreatitisor long-term alcohol abuse. Markedlyelevated amylase and lipase levels inan exudative aspirate suggest thediagnosis. The mildly elevated serumamylase level found in most patientswith a pancreatic-pleural fistula isthought to result from resorption ofamylase from the pleural spaces.⁴The differential diagnosis ofamylase-rich pleural effusion includesacute pancreatitis, lung carcinoma,metastatic carcinoma, pneumonia,esophageal perforation, lymphoma,leukemia, liver cirrhosis, hydronephrosis,and pulmonary tuberculosis.However, in pancreatic-pleural fistula,the pleural fluid amylase is usuallypancreatic isoamylase in origin,which may aid in the diagnosis.CT is recommended in the diagnosisof pancreatic-pleural fistula, becauseit shows pancreatic parenchymalatrophy, in addition to dilatationof the pancreatic ducts, calcifications,and pseudocysts. Moreover, the fistulacan sometimes be revealed.ERP is useful for imaging thepancreatic ductal anatomy, and it candemonstrate a fistulous tract that extendsto the pleural cavity. However,ERP is an invasive procedure that carriesthe risk of infection, pancreatitis,and bleeding. In addition, the pancreatogrammay fail to demonstrate theentire anatomy of the pancreatic-pleuralfistula.Magnetic resonance pancreatographyis a noninvasive imaging methodof assessing pancreatic diseases.The image produced can depict notonly parenchymal and ductal structuralchanges but also extrapancreaticcomplications, including pancreaticpleuralfistula.⁵ Because the contrastmedia is not injected, there is no riskof infection.TREATMENTMedical therapy. Standard medicaltherapy for pancreatic-pleural fistulaconsists of TPN and bowel rest. Repeatedthoracentesis and, sometimes,thoracostomy tube placement havebeen used for large pleural fluid accumulations.The success rate with thisapproach ranges from 40% to 60%.¹Octreotide, a long-acting somatostatinanalog, has been used to treatpancreatic fistulas.⁶ Somatostatinanalogs decrease the volume of fistula output, and they seem to promoteclosure of the fistula. In one study,failure to achieve fistula closure withoctreotide was attributed to pancreaticduct stenosis, pseudocyst, or patientnoncompliance.⁷Complications related to nonoperativetherapy include malnutrition,TPN-associated problems, central venouscatheter infections, and deepvenous thrombosis. A trial of conservativetherapy usually lasts about 3weeks.⁸ For patients who do not respondto such therapy initially, adelay in proceeding to more invasivemeasures increases morbidity andmortality.⁹Stent placement. Internal pancreaticfistulas have been treated successfullywith insertion of a stent inthe pancreatic duct by ERP.¹⁰ Becausethe main pancreatic duct is usuallydisrupted, the stent should be placedto bridge the site of rupture. However,it is probably more important that thestent decrease intraductal pressureby bypassing either the Oddi sphincteror any stricture in the duct.^11,12The response following stentplacement is usually dramatic, and patientscan quickly resume oral intake.The stents are kept in place for 4 to12 weeks. Follow-up intervals haveranged from 9 to 30 months, with norecurrences. Repair of the fistuloustract where it extends to the chest isunnecessary, because removal of theobstruction and disruption of the pancreaticduct prevent further passageof fluid to the chest. Data are currentlylacking on long-term consequencesof pancreatic duct stent placement.Surgery. If the pancreatic-pleuralfistula fails to close with conservativeor endoscopic treatment, surgery isindicated. Distal pancreatectomy isrecommended for fistulas that arisefrom the body and tail of the pancreasand are not associated with ductalstrictures in the head of the gland.If a large pseudocyst not amenableto resection is present, or if a ductalstricture cannot be encompassed bythe resection, then internal drainageof the pseudocyst or the actual fistulamust be performed. Fistulas thatarise from the head of the gland arealso treated, in general, by an internaldrainage procedure, whether or notan associated pseudocyst or ductalstricture is present.Pancreaticoduodenectomy anddistal subtotal pancreatectomy arerarely justified for fistulas, becausethey are associated with high morbidityand mortality. Internal drainageis usually accomplished with a Rouxen-Y pancreaticojejunostomy orcyst-jejunostomy

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