Printer Friendly

A Man with Recurrent Ascites after Laparoscopic Cholecystectomy.

CASE DESCRIPTION

A 32-year-old man presented with severe abdominal pain and ascites. His medical history included diagnosis of Sandifer syndrome, scoliosis requiring 3 spinal surgeries, microgastria, and hiatal hernia repair, and most recently, laparoscopic cholecystectomy (7 weeks prior). Postprocedural abdominal pain led to a computed tomography (CT) [3] scan which confirmed ascites. The possibility of a postcholecystectomy common bile duct leak prompted an endoscopic retrograde cholangiopancreatography (ERCP) with stent placement. Unfortunately, this did not prevent peritoneal fluid from reaccumulating and the patient was transferred to our institution for further evaluation and management. The patient was afebrile and vital signs were normal. The abdominal examination revealed mild diffuse nonspecific tenderness. CT scan of abdomen was performed revealing increased peritoneal fluid. The radiologist noted that the findings were likely iatrogenic and could represent a bile, lymph, or pancreatic leak. CT guided paracentesis aspirated 280 mL of fluid accumulated near the right hepatic lobe and paracolic gutter. Aspirate was described as watery opaque and white with a pink tinge. Results of body fluid laboratory analyses are described in Table 1.

DISCUSSION

Fluid accumulation after abdominal surgery could be the result of several etiologies. Definitive identification of the fluid source is critical to guide medical treatment. In this case, the increased amylase concentration in the fluid suggested pancreatic origin (1,2). However, the aspiration of milky turbid fluid following paracentesis that contains a high concentration of triglycerides, as measured by a nonglycerol blanked assay, may lead the physician to include chylous ascites in the differential diagnoses. Chylous effusions are characterized by the presence of chyle in fluid accumulations in the pleural or peritoneal space following lymphatic obstruction or disruption (3). Chyle is composed of lymph and lipids suspended in chylomicrons, which are the largest lipid-carrying lipoprotein particles that carry mainly exogenous triglycerides (4). While some cases of chylous effusions are idiopathic, most are caused by thoracic duct damage due to nontraumatic (e.g., malignancy, primarily lymphoma) or traumatic (e.g., surgical procedures or penetrating injuries) events (3).

Most chylous effusions resolve spontaneously or upon treatment of the underlying cause (3). Paracentesis can be used to provide relief from the pressure exerted by accumulated fluid. The loss of fluids should be compensated for by administering fluid, electrolytes, and in some cases, albumin. Depending on the clinical need, strategies to reduce chyle production can involve a low-fat, high-protein diet, supplemented with medium-chain fatty acids or, if the former fails, total parental nutrition. Additionally, somatostatin analogs have been shown to control chylous effusions and may be effective in cases of persistent chylous ascites (3, 5). If ascites reaccumulation persists for several weeks, surgical thoracic duct ligation and pleurodesis may be required.

Although pure chyle is white and opaque in appearance, it has been reported that 50% of chylous effusions do not have a milky/cloudy appearance upon gross examination, (4). Similarly, in the cohort of body fluid samples submitted for lipid analysis at our institution, we find approximately 20% of samples do not have a cloudy appearance. Therefore, visual inspection provides poor sensitivity for detection of chyle. Laboratory lipid analysis of the fluid can provide the distinction between chylous and nonchylous ascites. Given that chylomicrons are not found in body fluid specimens from nonchyle sources, the presence of chylomicrons in a body fluid is used to identify a chylous effusion. The detection of chylomicrons can be indirect via measurement of triglycerides by automated chemistry or direct via lipoprotein electrophoresis. When used as a surrogate for chylomicron detection in pleural fluids, a triglyceride concentration of >110 mg/dL is supportive of the presence of a chylous effusion. However, not all chylous samples abide by this cutoff, and reports of cutoffs in other fluids, including ascites, are limited (6). Therefore, definitive identification of chylomicrons in the fluid involves body fluid analysis using lipoprotein electrophoresis, a method infrequently performed at local hospitals. This method involves separation of lipoproteins in the fluid by agarose gel electrophoresis and staining the gel for lipids (e.g., with Sudan black) to allow for visualization of the migrating lipoprotein components. Lipoproteins separate on the gel according to size and isoelectric charge, with HDL traveling the farthest from the point of sample application and chylomicrons traveling the least distance or not at all (7). For chyle detection, the stained gel is examined qualitatively for the presence of chylomicrons as indicated by an appearance of a stained band at the point of specimen application (7, 8).

The above approach will correctly classify most body fluids as either containing or devoid of chylomicrons. However, we have noticed that in approximately 2.5% of lipoprotein electrophoresis tests conducted in our laboratory, nonchylomicron species (most likely cellular fragments or other lipid-containing debris) can give rise to a positive signal at the application point in body fluid samples devoid of chylomicrons. To isolate the specific signal for chylomicrons from other contaminants that may cause false-positive identification of a chylous effusion, lipid analysis can be performed on fractions of the body fluid after ultracentrifugation that separates the more dense HDL/LDL fraction (the HL fraction, density > 1.006 g/L) from the less dense VLDL/chylomicron fraction (VL fraction, density <1.006 g/L) (7). After ultracentrifugation, any cellular fragments or other debris will form a pellet while the lipoproteins will fractionate according to heir densities. Based on internal validation data, chylomicrons fractionate in the VL layer of body fluids similarly to the fractionation profile observed in serum. In our practice, triglycerides are measured in the whole fluid, the HL fraction, and the VL fraction and compared qualitatively, and all 3 fractions are subjected to lipoprotein electrophoresis to detect chylomicrons (Fig. 1A).

In the present case, the patient developed pancreatic ascites likely due to trauma to the pancreatic duct during laparoscopic cholecystectomy. The differential diagnosis included pancreatic ascites, chylous ascites, and a bile leak. Amylase concentration in ascites several fold greater than serum was consistent with a pancreatic leak. The appearance of the fluid combined with the triglyceride concentration of 332 mg/dL was suggestive of a chylous effusion (Table 1 and Fig. 1B). Also supportive of this diagnosis was the lipoprotein electrophoresis result on the unfractionated ascites fluid where staining at the application point was observed (Fig. 1C).

However, several findings led the laboratory to report that the sample did not contain significant accumulation of chylomicrons and therefore, the fluid was not consistent with a chylous effusion. First, the HL fraction was found to contain most of the triglycerides; this indicated that the triglycerides did not originate from chylomicrons which are exclusively found in the VL fraction (Fig. 1C). Second, further biochemical analysis demonstrated that an abnormal accumulation of free glycerol was causing a false-increase in measured triglycerides. Clinical methods for triglycerides (a.k.a. triacylglycerol) measurement begin with a hydrolysis step to separate fatty acids from their glycerol backbone and subsequently measure the concentration of released glycerol. Thus, assays for triglycerides that do not account for free glycerol will report falsely increased results when high concentrations of glycerol are present in the sample. Conversely, glycerol-corrected triglyceride methods enzymatically eliminate free glycerol before the hydrolysis step, and in the present case identified a triglyceride concentration of only 52 mg/dL (Fig. 1C) (9). At our institution, the assay for glycerol-blanked triglycerides is only used when the results from the nonblanked triglycerides assay are inconsistent with the rest of the laboratory analysis of the fluid.

In the present case, after thorough review of the case and discussions with the care team, the source of the glycerol remains undetermined. Third, lipoprotein electrophoresis of the HL and VL fractions revealed that chylomicrons were not present in the sample, as the chylomicron-like band at the application point of the whole fluid was found in the HL fraction and not the VL fraction (Fig. 1C).

The patient was treated conservatively with ascites drainage as required and given a prescription for pancreatic enzyme supplements. The patient's ascites resolved with these measures. Had the patient been identified as having chylous ascites, management would have included paracentesis, low-fat/higher--protein-carbohydrate diet, and potentially supplementation with medium-chain fatty acids. If chylous ascites had persisted despite these measures, then consideration would have been given to use of total parenteral nutrition and/or somatostatin analogs. In summary, although requiring substantially more labor and resources, the additional ultracentrifugation step before lipoprotein electrophoresis enables definitive identification of chyle in body fluid samples. This type of workup played an important role in the diagnosis and care of a patient with a complex presentation as it allowed the exclusion of the contribution of a chylous effusion to his condition. Although lipoprotein electrophoresis is considered the gold standard method for detection of chylous effusions and its specificity in unfractionated body fluids is high, the study presented here highlights that cases of rare false-positive results may be reconciled when sample fractionation is performed.

Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.

Authors' Disclosures or Potential Conflicts of Interest: No authors declared any potential conflicts of interest.

QUESTIONS TO CONSIDER

1. What is the utility of body fluid lipid analysis in the differential analysis of a body fluid specimen?

2. How is definitive diagnosis of a chyle leak achieved?

3. What is the potential benefit of lipoprotein electrophoresis analysis on fractions of an ultracentrifuged body fluid as compared to the whole fluid?

4. What is the concern with using a triglyceride assay that does not blank for endogenous glycerol?

POINTS TO REMEMBER

* Triglyceride concentration in body fluids, especially when measured using an assay that does not account for free glycerol, cannot be used to definitively discriminate between chylous and nonchylous effusions.

* Lipoprotein electrophoresis provides definitive diagnosis for a chylous effusion as it allows positive identification of chylomicrons.

* Non-chylomicron-containing lipid species that may cause false-positive chylomicron detection on lipoprotein analysis can be identified with additional fractionation of the body fluid by ultracentrifugation.

References

(1.) Block DR, Algeciras-Schimnich A. Body fluid analysis: clinical utility and applicability of published studies to guide interpretation of today's laboratory testing in serous fluids. Crit Rev Clin Lab Sci 2013;50:107-24.

(2.) Runyon BA. Amylase levels in ascitic fluid. J Clin Gastroenterol 1987;9:1724.

(3.) Laterre PF, Dugernier T, Reynaert MS. Chylous ascites: diagnosis, causes and treatment. Acta Gastroenterol Belg 2000;63:260-3.

(4.) Staats BA, Ellefson RD, Budahn LL, Dines DE, Prakash UB, Offord K. The lipoprotein profile of chylous and nonchylous pleural effusions. Mayo Clin Proc 1980;55:7004.

(5.) Shapiro AM, Bain VG, Sigalet DL, Kneteman NM. Rapid resolution of chylous ascites after liver transplantation using somatostatin analog and total parenteral nutrition. Transplantation 1996;61:1410-1.

(6.) Thaler MA, Bietenbeck A, Schulz C, Luppa PB. Establishment of triglyceride cut-off values to detect chylous ascites and pleural effusions. Clin Biochem 2017;50:134-8.

(7.) Burtis CA, Ashwood ER, Bruns DE, Tietz NW. Tietz textbook of clinical chemistry and molecular diagnostics. 5th ed. St. Louis: Elsevier/Saunders; 2012.1 online resource (xviii, 2238 p).

(8.) Noble RP. Electrophoretic separation of plasma lipoproteins in agarose gel. J Lipid Res 1968;9:693-700.

(9.) Klotzsch SG, McNamara JR. Triglyceride measurements: a review of methods and interferences. Clin Chem 1990;36:1605-13.

Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT.

Lusia Sepiashvili, [1] Ashley R. Dahl, [2] Jeffrey W. Meeusen, [1] Conor G. Loftus, [2] and Leslie J. Donato [1] *

[1] Department of Laboratory Medicine and Pathology, [2] Department of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN.

* Address correspondence to this author at: Department of Laboratory Medicine and Pathology, Mayo Clinic, Hilton 3-10B 200 First St. SW, Rochester, MN, 55905. Fax 507266-4088; e-mail donato.leslie@mayo.edu.

Received July 11,2016; accepted September 23,2016.

DOI: 10.1373/clinchem.2016.263756

[3] Nonstandard abbreviations: CT, computed tomography; ERCP, endoscopic retrograde cholangiopancreatography.

Caption: Fig. 1. Lipoprotein electrophoresis on peritoneal fluid lipoprotein fractions. (A), A schematic diagram of the procedure involving body fluid fractionation by ultracentrifugation and downstream analyses. An example of a fluid containing chylomicrons is shown on the gel. The chylomicrons (black arrows) appear as a band at the point of application in the whole fluid (WF) and VL fraction following lipoprotein electrophoresis and gel staining. (B), The gross appearance of the patient's peritoneal fluid and resulting fractions. (C), Body fluid lipid analysis results for the patient. Note the absence of a chylomicron band in the VL fraction indicating that there is no significant accumulation of chylomicrons. * Glycerol is reported in triglyceride equivalent units. To convert triglycerides or triglyceride equivalents from mg/dL to mmol/L, multiply by 0.01129.
Table 1. Body fluid testing laboratory results.

Analyte                   Result            Reference value

Bilirubin               0.26 mg/dL              NA (a)
                     (4 [micro]mol/L)
Amylase                  6265 U/L                 NA
Triglycerides     332 mg/dL (3.75 mmol/L)         NA
Cultures                 Negative              Negative
Malignant cells            None                  None
Nucleated cells        930/[micro]L              <500
Neutrophils                 1%                   <25%
Lymphocytes                 9%                   <75%
Monocytes/                  26%                  <70%
  macrophages
Eosinophils                 3%                    NA

(a) NA, notapplicable.
COPYRIGHT 2017 American Association for Clinical Chemistry, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2017 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Clinical Case Study
Author:Sepiashvili, Lusia; Dahl, Ashley R.; Meeusen, Jeffrey W.; Loftus, Conor G.; Donato, Leslie J.
Publication:Clinical Chemistry
Article Type:Clinical report
Date:Jul 1, 2017
Words:2201
Previous Article:American Liver Guidelines and Cutoffs for "Normal" ALT: A Potential for Overdiagnosis.
Next Article:Commentary.
Topics:

Terms of use | Privacy policy | Copyright © 2021 Farlex, Inc. | Feedback | For webmasters |