CASE REPORT A Chylous Mesenteric Cyst and a Study of Its Contents K.M.W. KEOUGH, PhD, M. HAWCO, BSc, S. ACHARYA, MD, D.A. MALATJALIAN, MD, W. SNEDDEN, PhD, A. KWAN, FRCS(C), and J.A. BARROWMAN, FRCP(C) Chylous mesenteric cysts are rare and little is known about their contents. Although the chyle is presumably derived from intestinal lymph and its contents broadly reflect those of this lymph, it is not part of a free-flowing system but is stagnant and li- able to undergo modification of its composition. Analysis of this fluid may contribute to an under- standing of the pathogenesis of these cysts. CASE REPORT A 44-year-old woman became aware of a painless swelling of the (L) lower abdomen over a year. At the same time urinary dribbling and frequency were noted but there were no other complaints referable to the gen- itourinary or gastrointestinal systems. Eight years pre- viously she underwent hysterectomy and right oophorec- tomy following a ruptured ectopic pregnancy. She suf- fered from rheumatic fever as a child and a hiatal hernia with esophageal reflux was diagnosed several years be- fore the onset of abdominal swelling. Routine hematolog- ical studies, serum electrolytes, blood urea, and liver tests were normal. Other normal examinations included chest x-ray, EKG, and barium enema. At laparotomy, a unilocular chylous cyst, 10 cm in diameter, was excised intact from the mesentery of the small intestine in the re- gion of the mid-jejunum. It contained approximately 700 ml of thick creamy liquid with some clear golden oil drop- lets. Microscopic examination of the cyst wall (Figure 1.) revealed a fibrovascular structure containing a few lym- phocytes. In large areas, the endothelial lining was re- placed by numerous foamy histiocytes. A number of emp- Manuscript received February 23, 1979; revised manuscript received May 24, 1979; accepted May 29, 1979. From the Faculties of Medicine and Science, Memorial Uni- versity of Newfoundland, St. John's, Newfoundland, Canada. Dr. Malatjalian's present address is: Department of Pathology, Victoria General Hospital, and Dalhousie University, Halifax, Nova Scotia, Canada. Address for reprint requests: Dr. J.A. Barrowman, Room 4332, Health Science Complex, St. John's, Newfoundland A1B 3V6 Canada ty thin-walled vascular spaces were present in the wall; these resembled lymphatic channels. Analysis of the Chylous Fluid. Samples were taken for routine bacteriological culture and for M. tuberculosis; these yielded no growth. A cell count on the fluid showed approximately 500 lymphocytes/mm z. Lipid extracts were made of undiluted and 1 : 5 diluted chyle (2). Dry weights of the lipid extracts were obtained by drying small portions to constant weight under vacuum and mea- suring on a Cahn 4100 electrobalance. Lipid phosphorus was determined by the procedure of Bartlett (3). Neutral lipids were separated by thin-layer chromatography on silica gel G using the solvent systems heptane-isopropyl ether-acetic acid (60 : 40 : 4, by volume) (Table 1) and chloroform-acetone-methanol (96 : 4 : 1, by volume), The plates were sprayed with potassium dichromate in sulfuric acid, charred at 110 ~ for 16 hr, and subjected to scanning densitometry. Samples were also incubated at 376 with shaking for periods up to 6 hr and similarly ana- lyzed; no significant changes in the proportions of neutral lipid Constituents occurred. Samples of lipid classes for fatty acid analysis were visualized with ultraviolet light after spraying the plates with 2', 7'-dichlorofluorescein. Fatty acid analysis was carried out as described by Dun- phy et al (4). The fatty acid profiles of triglyceride, choles- terol esters, and free fatty acids are presented in Figure 2. The plant sterols, campesterol, and /3-sitosterol" were sought by high-resolution mass spectrometry of the whole chyle according to the method previously described for muscle tissue (5), but were not detected. However, a pair of molecular ion peaks were observed at masses 416.365 (C2sH4sO2) and 430.381 (C29H~002) which were tentatively assigned to a mixture of a-,/3-, and 3,-tocopherols. Other specimens of the fluid were centrifuged for 30 rain at 100,000g to yield a clear infranatant for protein assay and other biochemical determinations by routine methods (Table 2). Lactic dehydrogenase was further studied by electrophoretic separation of the isoenzymeso All five isoenzyme concentrations were in excess of normal serum levels but fractions 4 and 5 were most prominent, being present in concentrations approximately 20-30 times those of normal serum. To examine the proportions of albumin and globulins in the infranatant, molecular ex- clusion chromatography was carried out and compared with the chromatographic pattern of similarly delipidated Digestive Diseases and Sciences, Vol. 24, No. 10 (October 1979) 0163-2116/79/1000-0797503.00/1 9 1979 Digestive Disease Systems, Inc. 797