A 12-year-old female shusui koi (Cyprinus carpio) that weighed 10.3 kg (22.7 lb) was examined by the University of Georgia Zoological Medicine Service because of an ulcerated mass located ventral and lateral to the dorsal fin on the left body wall (Figure 1) The mass was first noticed 1 month prior to examination and, during the intervening period, had increased in size and become ulcerated, which resulted in the patient having a decreased appetite and activity level. The fish was maintained with 30 other female koi of similar size in a 114-kL (30,000-gallon) pond with appropriate mechanical and biological filtration, protein skimmers, and UV sterilization. Water-quality variables were checked daily, and no problems were identified (ie, ammonia, nitrite, and nitrate concentrations were undetectable; pH = 7.5; and dissolved oxygen concentration, 10 mg/L). Water temperature was maintained at 18.3°C (65°F) during the winter. The patient had no history of previous medical problems and had not spawned. The patient and its pond mates were fed a commercial pelleted rationa for koi that contained 45% protein during peak season (the warmer months of the year when increased feeding and optimal growth occur) and 36% protein in the spring and fall. No deaths had been reported for the pond population in the months leading up to the patient being examined, aside from a female koi that was euthanized because of an ovarian adenocarcinoma.
For transport to the University of Georgia Veterinary Teaching Hospital, the patient was removed from its home pond with a net and placed into a heavy-duty double bag that contained 50 L of preoxygenated water and was inflated with 100% oxygen. The bag was then placed in an insulated container. The patient was transported for 6 hours by air and van to a local wholesale facilityb for koi in Watkinsville, Ga, where it was allowed to rest and reacclimate for 2 days. The patient was prepared for transport as previously described and transported by van for 30 minutes to the teaching hospital for examination.
To facilitate examination, blood sample collection, and diagnostic imaging, the patient was anesthetized with a 10% eugenol solutionc in water (dose, 50 mg of eugenol/L of water). Anesthesia induction was smooth and uneventful. While the patient was anesthetized, opercular movements were visually monitored and ranged between 25 and 60 opercular movements/min, and heart rate, which was monitored by Doppler probe, ranged from 60 to 63 beats/min. Physical examination revealed an approximately 7 × 5-cm smooth, ulcerated, firm mass that elevated the overlying skin on the left dorsolateral aspect of the body wall ventral to the dorsal fin. On palpation, the mass extended deep to the subcutis and medially toward the dorsal vertebral spinous processes. The remainder of the physical examination was unremarkable.
A blood sample (approximately 3 mL) was obtained from the caudal vein for hematologic and plasma biochemical analyses. Hematologic results revealed moderate leukopenia (WBC count, 10,900 WBCs/μL; reference range, 19,800 to 28,100 WBCs/μL) characterized by mild neutrophilia (neutrophil count, 5,990 neutrophils/μL; reference range, 1,570 to 3,900 neutrophils/μL), marked lymphopenia (lymphocyte count, 3,920 lymphocytes/μL; reference range, 14,700 to 23,500 lymphocytes/μL), and slight monocytosis (monocyte count, 981 monocytes/μL; reference range, 460 to 960 monocytes/μL).1 For a teleost, those results were considered most consistent with a stress leukogram rather than a systemic bacterial infection.2–7 Plasma biochemical results revealed moderate hypercalcemia (calcium concentration, 17.3 mg/dL; reference range, 9.9 to 10.6 mg/dL), hyperphosphatemia (phosphorus concentration, 11.6 mg/dL; reference range, 4.3 to 5.5 mg/dL), and moderate hypercholesterolemia (cholesterol concentration, 319 mg/dL; reference range, 152 to 175 mg/dL).8 In teleosts, high plasma calcium concentrations can be associated with ovarian maturation and reproductive activity, high dietary calcium content, calcium concentration in the water, hemolysis-induced artifact, or handling and stress-induced osmoregulatory and metabolic dysfunction.9–12 Hyperphosphatemia can be caused by high dietary phosphorus content, phosphorus concentration in the water, hemolysis-induced artifact, or handling and stress-induced osmoregulatory and metabolic dysfunction.9,11 Hypercholesterolemia is associated with handling, hypoxic stress, water temperature, seasonal pattern, dietary cholesterol content, and age, sex, and size of the fish.13–15 For this particular patient, the plasma biochemical abnormalities were attributed to stress associated with handling and the long-distance transport. Other differential diagnoses for the plasma biochemical derangements observed included physiologic changes owing to reproductive activity (given the patient's age and sex), dietary influences, and sample handling. None of those differential diagnoses precluded the patient from undergoing anesthesia, advanced diagnostic imaging, or surgery.
Computed tomographic scans were obtained before and after contrast medium administration to better characterize the tissue type and vascularity of the mass, to determine its involvement with underlying structures, and for surgical planning purposes. The patient was positioned in dorsal recumbency and immobilized in a trough covered with damp towels. Owing to the inherent constraints of performing CT scans on a teleost, anesthesia was maintained by regular, manual bathing of the gills with an anesthetic solution (45 to 50 mg eugenol/L of oxygenated water) by use of 60-mL syringes. A whole-body CT scan was performed by use of a 64-slice helical scannerd with the following parameters: spiral pitch, 0.8; kV, 120; mAs, 250; and a matrix of 512 × 512. Images were reconstructed with medium-frequency (soft tissue) and high-frequency (bone) algorithms with a slice thickness of 0.6 mm in transverse, sagittal, and dorsal plane sequences. The postcontrast scans were acquired approximately 10 (arterial phase) and 150 seconds (delay phase) after manual injection of iohexole (1.71 mL/kg [0.77 mL/lb]; 350 mg of iodine/mL) into the caudal vein by use of a 21-gauge butterfly catheter. The duration required for pre- and postcontrast CT image acquisition was 9 minutes, and the total duration of the CT procedure (including setup) was approximately 25 minutes.
Postcontrast CT images revealed that most of the contrast material had extravasated from the caudal vein, to the left of midline. Consequently, there was limited vascular and parenchymal uptake of the contrast material on the arterial and delay-phase images.
At the caudal aspect of the dorsal fin, to the left of midline, dorsal to the vertebral canal, and lateral to the vertebral spines, there was a homogenous fat-opaque mass (5.1 × 3.9 × 7.1 cm) within the muscle. The mass was encased by a uniformly thin, well-defined capsule and contained a central septation (Figure 2) The fat portion of the mass was not contrast enhanced (−95 HU), but there was mild contrast enhancement of the capsule wall (42 to 52 HU). The remaining musculoskeletal and intracoelomic structures were unremarkable on the CT images. The primary differential diagnosis for the mass was lipoma, with liposarcoma being less likely given the relatively homogeneous attenuation and well-defined borders of the mass.
Immediately following completion of the CT procedure, the patient was positioned in sternal recumbency on a recirculating-water anesthesia table for fish. Anesthesia was maintained by use of a water pump and 2 hoses, which were placed in the mouth of the patient to provide active flow of the anesthetic solution (45 mg eugenol/L water) over the gills. Ultrasonographic evaluation of the mass was performed with a 9- to 11-MHz linear transducer.f The mass was diffusely heterogeneous with an echogenicity similar to fat and had a well-defined capsule with internal septation (Figure 3) The mass had poor central and peripheral vascularity on Doppler interrogation. Ultrasound-guided needle biopsyg specimens of the mass were then obtained for histologic and microbiological analyses. The ultrasonographic examination and biopsy procedure required a total of 15 minutes. The patient was placed in clean preoxygenated water to recover from anesthesia after the completion of the diagnostic procedures. Complete anesthetic recovery occurred within 10 minutes, without any complications. The patient was discharged into the care of the local koi wholesaler who provided suitable off-site holding facilities and care until laboratory results became available.
Histologic examination of the biopsy specimens revealed normal adipose tissue without any evidence of an infectious or inflammatory process. On the basis of the presence of normal adipocytes and absence of neoplastic cells, a lipoma was suspected; however, a liposarcoma could not be definitively ruled out owing to the small specimen size. Microbiological evaluation revealed no fungal or bacterial growth.
The patient was brought back to the teaching hospital 1 week later for surgical excision of the suspected lipoma. Anesthesia was induced (50 mg of eugenol/L of water) and maintained (40 mg of eugenol/L of water) with eugenol in water by use of a recirculating anesthesia system as previously described. Cefazolinh (25 mg/kg [11.4 mg/lb], IV in the caudal vein) was administered intraoperatively. Perioperative analgesia was initiated with butorphanol tartratei (0.4 mg/kg [0.18 mg/lb], IM). The fish was positioned in sternal recumbency and draped with wet towels. The surgical site was isolated with sterile hand towels soaked in sterile saline (0.9% NaCl) solution. A sterile cotton-tipped applicator soaked in sterile saline solution was used to wipe along the planned incision site once to remove the surface mucus.
A No. 15 scalpel blade was used to make an approximately 15-cm curvilinear full-thickness incision over the mass, ventral to the ulcerated region. Metzenbaum scissors were used to bluntly dissect the integument from the dorsal and lateral aspects of the mass. Digital dissection was then used to separate the rest of the tumor from the adjacent tissues until it could be removed en bloc (Figure 4) A single blood vessel arising between the dorsal vertebral processes was cauterized by use of a bipolar radiosurgical unit.j The surgical site and tumor cavity were copiously lavaged with sterile saline solution as described.16 No attempt was made to fill or reduce dead space because external water pressure would prevent seroma formation. The thin, superficial muscle and dermis were closed with 2-0 absorbable triclosan-impregnated poliglecaprone 25 suturek in a simple continuous pattern. The skin was then carefully apposed with 2-0 absorbable triclosan-impregnated poliglecaprone 25 suturek in a simple interrupted pattern. As surgery neared completion, the concentration of eugenol used to maintain anesthesia was gradually lowered in a stepwise manner (ie, from 40 to 35 to 30 to 25 mg of eugenol/L of water) before being discontinued. Recovery from anesthesia was uneventful, and there were no anesthetic or intraoperative complications.
Results of histologic evaluation of the mass were most consistent with a lipoma. The unencapsulated expansile mass was composed of sheets of well-differentiated adipocytes, which were round and had abundant cytoplasm with a single clear vacuole (lipid) that displaced and flattened the nucleus. There was mild anisokaryosis and anisocytosis. No mitotic figures were observed. Well-differentiated adipocytes dissected layers of skeletal myocytes within a small portion of adhered muscle tissue. Those adipocytes likely represented normal adipocytes, but an infiltrative lipoma could not be definitively ruled out on the basis of histologic examination. Adipocytes extended to cut borders of the mass (Figure 5)
Postoperative care consisted of placing the fish in water with 0.3% salinity for 3 weeks following surgery to reduce the osmotic stress on the patient and pathogen load at the surgical site.17–21 Because the surgical procedure was performed aseptically, postoperative antimicrobial administration was not indicated. Administration of postoperative analgesics would have been ideal but was considered impractical owing to the limitations of accessibility at the holding facility and concern about causing additional stress to the patient. Immediately after the patient was returned to the holding tank following surgery, improvements in appetite and activity were seen, but no signs of pain or discomfort were noted.
Following surgery, the patient was housed at the wholesaler facility for 5 weeks and then was reevaluated at the teaching hospital. Transport, anesthesia, and the acquisition of noncontrast-enhanced CT images were performed as previously described. The surgical site had healed with no signs of dehiscence and minimal scarring. The CT images indicated that the intramuscular lipoma in the left dorsal body wall was absent, and the regional epaxial muscles were only marginally reduced in size with interrupted fascial planes. The cutaneous tissues were concave with a mildly irregular margin, consistent with the surgical approach. There was no evidence of mass regrowth or regional osteomyelitis (Figure 6) The patient survived for 6 months after surgery with an improved quality of life and without any further health problems. Unfortunately, long-term follow-up was not possible owing to the death of the patient from predation by a wild animal.
No third-party funding or support was received in connection with this study or the writing or publication of the manuscript. The authors declare that there were no conflicts of interest.
The authors thank Vicki Vaughn and Carl Foss of The Koi Store, Watkinsville, Ga, for assistance with fish transportation and boarding between procedures.
Nijikawa premium koi food, EWOS, City of Industry, Calif.
The Koi Store, Watkinsville, Ga.
AQUI-S 20E (10% eugenol solution), AquaTactics Fish Health, Kirkland, Wash.
Siemens Somatom Sensation 64 CT scanner, Erlangen, Germany.
Omnipaque injection, GE Healthcare Inc, Princeton, NJ.
Logiq S8 ultrasound, GE Healthcare Inc, Princeton, NJ.
Tru-Cut 14-gauge biopsy needle, Medline Industries Inc, Mundelein, Ill.
Cefazolin, WG Critical Care LLC, Paramus, NJ.
Torbugesic, Zoetis Inc, Kalamazoo, Mich.
4.0 MHz Surgitron, Ellman International Inc, Hicksville, NY.
Monocryl-Plus Antibacterial Suture, Ethicon US LLC, Blue Ash, Ohio.
Bambir S, Helgason S, Marino F, et al. Some interesting tumours in fish (abstr), in Proceedings. 11th Annu Ljudevit Jurak Int Symp Comp Pathol 2000;33.
Volpatti D, Patarnello P, Novelli A, et al. Lipoma, fibrolipoma, liposarcoma in mormore, Lithognatus mormyrus (L) alleviate (abstr), in Proceedings. Histol Ultrastruct Observ Conf Societa Italiana Pathologia Ittica (SIPI) 1998.
1. Tripathi NK, Latimer KS, Burnley VV. Hematologic reference intervals for koi (Cyprinus carpio), including blood cell morphology, cytochemistry, and ultrastructure. Vet Clin Pathol 2004;33:74–83.
2. Ainsworth AJ, Dexiang C, Waterstrat PR. Changes in peripheral blood leukocyte percentages and function of neutrophils in stressed channel catfish. J Aquat Anim Health 1991;3:41–47.
3. Ellsaesser CF, Clem LW. Haematological and immunological changes in channel catfish stressed by handling and transport. J Fish Biol 1986;28:511–521.
5. McLeay DJ. Effects of cortisol and dexamethasone on the pituitary-interrenal axis and abundance of white blood cell types in juvenile coho salmon, Oncorhynchus kisutch. Gen Comp Endocrinol 1973;21:441–450.
6. Pickering AD, Pottinger TG. Cortisol can increase the susceptibility of brown trout, Salmo trutta L, to disease without reducing the white blood cell count. J Fish Biol 1985;27:611–619.
7. Wojtaszek J, Dziewulska-Szwajkowska D, Łozińska-Gabska M, et al. Hematological effects of high dose of cortisol on the carp (Cyprinus carpio L): cortisol effect on the carp blood. Gen Comp Endocrinol 2002;125:176–183.
8. Tripathi NK, Latimer KS, Lewis TL, et al. Biochemical reference intervals for koi (Cyprinus carpio). Comp Clin Pathol 2003;12:160–165.
9. Mirghaed AT, Ghelichpour M, Hoseini SM, et al. Hemolysis interference in measuring fish plasma biochemical indicators. Fish Physiol Biochem 2017;43:1143–1151.
10. Palmeiro BS, Rosenthal KL, Lewbart GA, et al. Plasma biochemical reference intervals for koi. J Am Vet Med Assoc 2007;230:708–712.
11. Swanson CR, Lewbart GA, Harms CA, et al. Fish health management. Available at: repository.lib.ncsu.edu/bit-stream/handle/1840.2/2520/FishHealthManagement2002.pdf?sequence=1. Accessed Oct 14, 2019.
12. Wedemeyer G. Some physiological consequences of handling stress in the juvenile coho salmon (Oncorhynchus kisutch) and steelhead trout (Salmo gairdneri). J Fish Res Board Can 1972;29:1780–1783.
13. Hille S. A literature review of the blood chemistry of rainbow trout, Salmo gairdneri Rich. J Fish Biol 1982;20:535–569.
14. Jawad LA, Al-Mukhtar MA, Ahmed HK. The relationship between haematocrit and some biological parameters of the Indian shad, Tenualosa ilisha (Family Clupeidae). Biodivers Conserv 2004;27:47–52.
15. Skjervold PO, Fjæra SO, Østby PB, et al. Live-chilling and crowding stress before slaughter of Atlantic salmon (Salmo salar). Aquaculture 2001;192:265–280.
16. Sladky KK, Clarke III EO. Fish surgery: presurgical preparation and common surgical procedures. Vet Clin North Am Exot Anim Pract 2016;19:55–76.
17. Greenwell MG, Sherrill J, Clayton LA. Osmoregulation in fish. Mechanisms and clinical implications. Vet Clin North Am Exot Anim Pract 2003;6:169–189.
18. Haswell MS, Thorpe GJ, Harris LE, et al. Millimolar quantities of sodium salts used as prophylaxis during fish hauling. Progress Fish Cult 1982;44:179–183.
19. Mazik PM, Simco BA, Parker NC. Influence of water hardness and salts on survival and physiological characteristics of striped bass during and after transport. Trans Am Fish Soc 1991;120:121–126.
20. Noga E. Methods for treating fish diseases. In: Fish disease: diagnosis and treatment. St Louis: Mosby-Year Book, 1996;253–300.
21. Wedemeyer GA. Effects of fish cultural procedures. In: Physiology of fish in intensive culture systems. New York: Chapman and Hall, 1996;133–135.
23. Harshbarger JC, Spero PM, Wolcott NM. Neoplasms in wild fish from the marine ecosystem emphasizing environmental interactions. In: Couch JA, Fournie JW, eds. Pathobiology of marine and estuarine organisms. Boca Raton, Fla: CRC Press, 1993;157–176.
24. Grizzle JM, Goodwin AE. Neoplasms and related lesions. In: Leatherland AF, Woo PTK, eds. Fish diseases and disorders. Vol 2: non-infectious disorders. Wallingford, England: CABI Publishing, 1998;37–104.
26. Wellings SR. Neoplasia and primitive vertebrate phylogeny: echinoderms, prevertebrates, and fishes—a review. Natl Cancer Inst Monogr 1969;31:59–128.
27. Hard GC, Williams R, Lee J. Survey of demersal fish in Port Phillip Bay for incidence of neoplasia. Mar Freshw Res 1979;30:73–79.
28. Haddow A, Blake I. Neoplasms in fish: a report of six cases with a summary of the literature. J Pathol Bacteriol 1933; 36:41–47.
29. Rahmati-Holasoo H, Shokrpoor S, Tavakkoli A, et al. Liposarcoma or invasive lipomatosis in flower horn fish, hybrid cichlid: clinical, radiological, ultrasonographical and histopathological study. J Fish Dis 2016;39:309–315.
30. Sharon G, Benharroch D, Kachko L, et al. Liposarcoma in clownfish, Amphiprion ocellaris Cuvier, produced in indoor aquaculture. J Fish Dis 2015;38:575–580.
32. Marino F, Monaco S, Salvaggio A, et al. Lipoma in a farmed northern bluefin tuna, Thunnus thynnus, (L). J Fish Dis 2006;29:697–699.
33. Easa ME, Harshbarger JC, Hetrick FM. Hypodermal lipoma in a striped (grey) mullet (Mugil cephalus). Dis Aquat Organ 1989;6:157–160.
34. Chen HC, Pan IJ, Tu WJ, et al. Neoplastic response in Japanese medaka and channel catfish exposed to N-methyl-N'-nitro-N-nitrosoguanidine. Toxicol Pathol 1996;24:696–706.