Cholelithiasis and chronic cholangiohepatitis in a mute swan (Cygnus olor)

CHOLELITHIASIS is defined as the formation of solid material in the gall bladder or common bile duct. There may be one large stone or many small stones of variable composition. Rare cases of cholelithiasis have been reported in various domestic animal species, including chickens (Gallus domesticus) (Jones and others 1997). This short communication describes a case of cholelithiasis in a mute swan (Cygnus olor). An adult, female mute swan was found next to a highway and presented to the Royal Society for the Prevention of Cruelty to Animals West Hatch Wildlife Hospital, Somerset, with a deep bite wound to the right of the tail. The swan weighed 5·6 kg (normal range 7·3 to 10·6 kg [Snow and Perrins 1998]), and was weak and unable to stand. The bird was anaemic, with a packed-cell volume (PCV) of 0·11 l/l (normal range 0·31 to 0·48 l/l). Treatment was initiated with intravenous compound sodium lactate (Aqupharm No 11; Animalcare), plasma substitute solution (Haemaccel; Intervet UK) and 10 mg/kg marbofloxacin (Marbocyl SA; Vetoquinol), orally once a day. Additional supportive treatment included 1 mg/kg nandrolone laurate (Laurabolin; Intervet UK) every seven days and 5 ml vitamin B/iron supplementation (Equisup; Vetoquinol) once a day. Blood samples were taken on days 1, 9 and 15 and submitted to Greendale Veterinary Laboratories for haematological and serum biochemical examination. The results of these examinations are shown in Table 1. The samples from day 1 revealed a reduced red blood cell (RBC) count (0·73 x 1012 RBCs/l, reference range 1·9 to 3·0 x 1012 RBCs/l), and an elevated white blood cell (WBC) count (34·1 x 109 WBCs/l, reference range 6·0 to 18·5 x 109 WBCs/l) with heterophilia (23·2 x 109 heterophils/l, reference range 3·3 to 14·6 x 109 heterophils/l) and monocytosis (9·6 x 109 monocytes/l, reference range <1·5 x 109 monocytes/l). On day 2, the PCV had decreased to 0·10 l/l, and it was decided to transfuse 70 ml of heparinised blood from a donor swan intravenously. By day 4, the PCV had risen to 0·24 l/l but the swan’s bodyweight had decreased to 5·25 kg. After nine days of treatment with marbofloxacin, a second blood sample revealed an increase of the RBC count (1·46 x 109 RBCs/l) and a reduced monocyte count (2·0 x 109 monocytes/l) but a further increase in the heterophil count (24·7 x 109 heterophils/l). The marbofloxacin was discontinued, and on day 12 the bird was placed on cephalexin (Ceporex; Schering-Plough Animal Health) at 500 mg orally twice daily, equivalent to 100 mg/kg. A further blood sample taken on day 15 indicated marked deterioration, with a PCV of 0·20 l/l, RBC count of 1·3 x 109 RBCs/l, and a marked further increase in the WBC count (78·8 x 109 WBCs/l) and the heterophilia (64·6 x 109 heterophils/l), and monocytosis (11·0 x 109 monocytes/l). The bird was failing to put on weight (Table 1) and was voiding increased amounts of uniformly green urates, suggestive of primary or secondary hepatic disease. An exploratory laparotomy was performed on day 20 to investigate the suspected liver disorder. Anaesthesia was induced with xylazine (Rompun 2%; Bayer) and ketamine (Narketan; Vetoquinol) (Routh and Painter 1999, Routh 2000). The swan was intubated and anaesthesia was maintained with isoflurane (Isoflo Vet; Schering-Plough Animal Health). A midline incision was made into the coelomic cavity, revealing a firm, pale liver and marked distension of the biliary system by pale green fluid. A 1 cm diameter, laminated, pale tan cholelith was obstructing the lumen of the cysticoenteric duct at its juncture with the duodenum (Fig 1). On the basis of these findings the bird was humanely euthanased. Tissue specimens were collected and fixed in 10 per cent neutral buffered formalin, and submitted to the Department of Pathology and Infectious Diseases of the Royal Veterinary College, University of London, for histological examination. Fixed tissues were processed routinely, embedded in paraffin, and 5 μm thick sections were stained with haematoxylin and eosin. Further sections were stained with Brown and Brenn Gram stain, Perlis’ Prussian blue for ferric iron and Von Kossa stain for minerals. A swab of bile was taken immediately after the swan was euthanased and submitted for aerobic bacterial culture. Additionally, a specimen from the cholelith was sent to the Klinik und Poliklinik fur Urologie, Bonn, Germany, for chemical analysis. Microscopically, the epithelial lining of the cysticoenteric duct was extensively ulcerated with infiltration by numerous epithelioid macrophages and smaller numbers of granulocytes, plasma cells and lymphocytes within small to moderate amounts of reactive fibrous tissue. Several layers Veterinary Record (2006) 158, 166-167