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* From the Department of Cardiothoracic and Vascular Surgery, University of Texas Medical School Houston, Memorial Hermann Heart and Vascular Institute, Houston, TX.
Correspondence to: Anthony L. Estrera, MD, Department of Cardiothoracic and Vascular Surgery, The University of Texas Health Science Center at Houston Medical School, 6410 Fannin St, Suite 450, Houston, TX 77030; e-mail: Anthony.L.Estrera{at}uth.tmc.edu
Abstract
Background: Chylothorax occurring during thoracic aortic surgery is an infrequent but serious complication. The purpose of this study was to analyze our experience with this complication and the resulting outcomes.
Methods: From January 1991 to July 2005, we performed 1,233 descending thoracic and thoracoabdominal aortic surgical procedures. A retrospective review was performed to analyze and identify preoperative and operative risk factors as well as management outcomes of postoperative chylothorax (PCT).
Results: PCT developed in five patients (0.4%). All five cases occurred with descending thoracic aortic aneurysm repair, and 80% (four of five patients) were undergoing aortic reoperation. All patients were managed successfully with no mortality. Risk factors for the development of chylothorax were descending thoracic aortic repair (p = 0.006) and thoracic aortic reoperations (p = 0.0003). Nonoperative management was successful in 60% (three of five patients). Two patients required left thoracotomy with direct ligation. Mean hospital length of stay was 35 days (range, 15 to 60 days). Mean follow-up was 33 months (range, 3 to 69 months) with no recurrence of chylothorax or additional morbidity or mortality.
Conclusions: Chylothorax is more likely to occur with reoperations and repairs involving the descending thoracic aorta. Although PCT is associated with longer hospital length of stay, it is not associated with increased infectious complications. Early identification and prompt treatment may decrease both early and late morbidity and mortality.
Key Words: aortic surgery • chylothorax
Postoperative chylothorax (PCT) remains a rare complication of thoracic aortic surgery. Similar to previous reports,123456789 the complication of PCT generally occurs in 0.5 to 2% of patients, having been described for most thoracic surgical procedures. PCT is suspected when drainage from the chest tubes becomes milky. Late presentation may occur with the development of a new pleural effusion associated with dyspnea. The diagnosis of PCT is confirmed by biochemical and microscopic examination of the pleural fluid showing increased triglyceride and lymphocyte levels. The morbidity and mortality from PCT may be significant and related to malnutrition, dehydration, and immunologic dysfunction. Moreover, large-volume chylothorax may compromise cardiopulmonary, renal, and hepatic function. The mortality rate with PCT may be as high as 50%, especially in chronically debilitated patients.12
PCT complicating thoracic aortic surgery has been described, but management and outcomes have not been clearly delineated.810 The purpose of this study was to review our experience with PCT complicating thoracic aortic surgery and to describe our management strategy and report our outcomes.
Materials and Methods
From January 1991 to July 2005, we performed 1,233 descending thoracic and thoracoabdominal aortic surgical procedures. All repairs were performed using a woven polyester graft with either inclusion or bypass of the necessary arteries (intercostals, renal, and visceral arteries). In 1992, we began using the adjunct (distal aortic perfusion and cerebrospinal drainage) in select repairs. We currently use the adjunct in all elective repairs. The operative techniques have been described in detail previously.11 The incision was tailored to the extent of the aneurysm as noted on the preoperative radiography but was, at times, modified during surgery, as per the requirements of clamp placement. Final determination of aneurysm extent was made intraoperatively based on the amount of aorta replaced. Thoracoabdominal aortic aneurysms (TAAAs) were classified according to the 5-extent modified Crawford classification system, which has been previously described.11 All preoperative, operative, and postoperative data were collected and maintained prospectively. Retrospective review was performed to analyze and identify preoperative and operative risk factors as well as management outcomes.
Chylothorax was suspected when the patient’s chest tube drainage became milky or cloudy. Diagnosis was confirmed by biochemical sampling and microscopic evaluation of the suspected fluid. Triglyceride levels > 100 mg/dL or predominant presence of lymphocytes confirmed the diagnosis. All patients were managed initially by nothing by mouth (NPO), total parenteral nutrition (TPN), and chest drainage. Persistent chylothorax (> 500 mL/d for > 1 week or chylothorax persisting for > 2 weeks) was managed operatively via a left lateral thoracotomy with direct ligation of the leaking thoracic duct tributary. Cream was administered to the patient by mouth 1 h prior to the operation to enhance identification of the chylous fistula.
Data were analyzed by contingency table methods. Common odds ratios were computed except when a zero cell was present, in which case a zero-cell correction was used and the odds ratio was computed by the logit method; p values were computed by Fisher Exact Test. Computations were performed using SAS statistical software (version 8.2; SAS Institute; Cary, NC).
Results
PCT developed in 0.4% (5 of 1,159 patients). Mean age of these patients was 64 years, and three of five patients were women. All five cases occurred with descending thoracic aortic aneurysm (DTAA) repair, and 80% (four of five patients) were undergoing aortic reoperations. Proximal aortic cross-clamp placement was performed distal to the left subclavian artery (LSCA) in all cases (Table 1 ). Mean time to diagnosis of chylothorax was 7.2 days from the date of thoracic aortic repair (range, 2 to 14 days). Chylothorax occurred in the immediate postoperative period in 60% (three of five patients) with chest tubes in place, while in two cases (40%) the diagnosis was made in a delayed fashion when patients presented with a left pleural effusion > 10 days after surgery. The diagnosis was confirmed by biochemical and microscopic examination of the effusion fluid showing increased triglyceride (range, 200 to 730 mg/dL), total protein (range, 2.3 to 3.6 g/dL), and high lymphocyte count (range, 3.5 to 75 x 106/mL). Repeat cultures of the drained chyle were negative for organisms in all patients, and no patient exhibited evidence of septicemia or wound infection.
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Reexploration for surgical control of the chylous leak was necessary in 40% (two of five patients) regardless of prompt initial conservative treatment due to prolonged chylous leak (> 10 days) or persistent large-volume chylous drainage (> 10 mL/kg/d). At the time of surgical reexploration through the same left thoracotomy incision, the location of chylous leak was clearly identified to be arising from the thoracic duct tributaries in the upper third of the left chest at the level of the proximal anastomosis between the descending thoracic aorta and the graft distal to the LSCA. Administration of cream by mouth 1 h before exploration in one patients enabled easier localization of the leak. The main thoracic duct was intact and patent in both cases. Pledgeted suture ligature of the leaking tributaries was performed in both cases. After surgical ligation, chyle leak stopped in within 2 days (1 day for one patient, and 2 days for the other patient).
ICU length of stay (mean, 5 days; range, 2 to 7 days) and hospital length of stay (mean, 35 days; range, 15 to 60 days) were significantly longer compared to those cases of descending thoracic aortic repair not complicated by chylothorax (mean length of stay, 9.3 days) [p < 0.006]. Mean follow-up was 33 months (range, 3 to 69 months) with no recurrence of chylothorax or additional morbidity or mortality. Risk factors derived by univariate analysis for the development of chylothorax during thoracic aortic repair were descending thoracic aortic repair (p = 0.006) and previous distal thoracic aortic surgery (reoperation) [p = 0.0003].
Discussion
With an overall incidence of 0.4%, this report emphasizes the rarity of this complication following thoracic aortic surgery. This is similar to previous reports1810 noting that PCT is rare with thoracic aortic surgery. In this report, we did not include ascending and transverse arch repairs via a median sternotomy for the analysis since no cases of chylothorax were noted during these procedures. For this reason, all analyses were performed on data collected for thoracic aortic repairs via a thoracotomy or thoracoabdominal incision (descending thoracic and thoracoabdominal surgical repairs).
Analysis revealed that the only significant risk factors for PCT after thoracic aortic surgery were thoracic aortic reoperations and descending thoracic repairs (Table 2 ). It is not entirely clear why reoperative aortic surgery was a risk factor, but one possible explanation is that the presence of adhesions and lack of surgical planes may render the thoracic duct tributaries susceptible to injury. In addition, native anatomic location of the thoracic duct may be altered during the primary intervention, leading to increased risk of injury.
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The anatomic course of the thoracic duct has been previously well described.3 It begins in the abdomen as a continuation of the cisterna chyli, which is situated on the front of the body of the second lumbar vertebra to the right side of and behind the aorta to the right crus of the diaphragm. The anatomic course enters the thorax through the aortic hiatus of the diaphragm and ascends through the posterior mediastinal cavity between the aorta and azygos vein. Opposite the fifth thoracic vertebra, it inclines toward the left side, enters the superior mediastinal cavity, and ascends posterior to the aortic arch, then passing behind the origin of the LSCA. It ascends forming an arch that rises approximately 3 to 4 cm above the clavicle to the level of the seventh cervical vertebra behind the carotid sheath crossing anterior to the subclavian artery. It ends by opening into the angle of junction of the left subclavian vein with the left internal jugular vein (Fig 1 ). In addition, the main thoracic duct has many tributaries. It also receives the efferents from the posterior mediastinal lymph glands and from the posterior intercostal lymph glands of the upper six left spaces.3 Based on the finding of this study, it is likely that these are the tributaries that are susceptible to injured during thoracic aortic repair.
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It has been suggested that the presence of PCT associated with thoracic aortic repair may be associated with increased risk of graft infection. We did not observe this in our experience. Cultures of the chylous drainage were sterile, and no increased incidence of infectious complications was noted. Long-term follow-up revealed no increased incidence of graft infection. Timely diagnosis and treatment may have been the reasons that no increased infectious morbidities were noted.
Our diagnostic and treatment strategy for PCT has not differed from what has been described previously.8 Although some have advocated an initial trial of oral intake with restriction to medium-chained fats, we initiated immediate NPO management with insertion of central venous line for TPN. As with other institutions, our indications for surgical exploration with ligation remains prolonged chylous output and large volume of output.10 For the two patients who required open exploration with ligation, we were fortunate to be able to identify and ligate the chylous leak on initial re-exploration. No further re-explorations or en masse thoracic duct ligation via a right thoracotomy were required. Some have suggested less invasive surgical procedures for the treatment of PCT following aortic surgery. In one report,1 three cases of PCT following thoracic aortic aneurysm repair were described; nonoperative management was effective in one of three patients. Two patients were managed by thorascopic ligation via the left chest with surgical clipping of the chylous leak in one case, and application of fibrin glue in the other case.1 Others10 have suggested early (< 7 days from diagnosis of PCT) thorascopic clipping of the main thoracic duct via the right chest in order to prevent aortic graft infection.
It is difficult to derive compelling conclusions from this study due to the small number of cases of PCT. In addition, this study does not account for the cases in which a chylous leak was identified or suspected but repaired or ligated at the initial primary operation. Due to the retrospective nature of this study, the incidence of this circumstance could not be determined. Although PCT remains a rare complication, this report does address some of the issues concerning its management and outcome after thoracic aortic repair.
PCT after thoracic aortic repair remains rare, occurring in patients requiring descending thoracic repair and thoracic aortic reoperations. PCT is associated with longer ICU and hospital length of stay but is not associated with increased infectious complications. Early identification and prompt treatment may decrease both early and late morbidity and mortality.
Acknowledgements
The authors thank Kirk Soodhalter for editorial assistance and Chris Akers for illustrations.
Footnotes
Abbreviations: DTAA = descending thoracic aortic aneurysm; LSCA = left subclavian artery; NPO = nothing by mouth; PCT = postoperative chylothorax; TAAA = thoracoabdominal aortic aneurysm; TPN = total parenteral nutrition
The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
Received for publication November 21, 2005. Accepted for publication March 18, 2006.
References
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