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Compendium December 2011 (Vol 33, Issue 12)

Clinical Snapshot: Colitis in a Paint Gelding

by Sarah D. Cramer, DVM, Brenda Love, DVM, PhD, DACVM, Jerry W. Ritchey, DVM, PhD, DACVP, Heidi Banse, DVM

    Case Presentation

    A 7-year-old Paint gelding presented to the Oklahoma State University Teaching Hospital with a 2-day history of mild colic. On presentation, the gelding was depressed. On physical examination, the gelding had tachycardia (60 to 68 bpm; reference range: 28 to 44 bpm) and a fever (101.5°F; reference range: 99°F to 101°F). A complete blood count showed neutropenia (neutrophils: 612 cells/µL; reference range: 2700 to 6700 cells/µL) with a left shift (band neutrophils: 1122 cells/µL; reference range: <100 cells/µL) and lymphopenia (lymphocytes: 1292 cells/µL; reference range: 1500 to 5500 cells/µL). A biochemistry screen revealed a mild hyperbilirubinemia (bilirubin: 5.1 mg/dL; reference range: <2.5 mg/dL). Nasogastric intubation yielded no net reflux. Rectal examination revealed no significant abnormalities. Abdominocentesis produced abdominal fluid with a very high number of white blood cells, including degenerate neutrophils. Abdominal ultrasonography revealed a thickened small intestine and large colon. The colon was filled with fluid, but diarrhea was not present. Therapy was initiated, including intravenous fluids (dose unavailable), potassium penicillin (22,000 IU/kg IV q6h), metronidazole (20 mg/kg PO q8h), gentamicin (6.6 mg/kg IV), heparin (40 IU IV q8h), dimethyl sulfoxide (dose unavailable), and flunixin meglumine (1.1 mg/kg IV). Overnight, the gelding had an elevated heart rate (64 to 72 bpm; reference range: 28 to 44 bpm) and was frequently recumbent. The following day, the patient collapsed, had a seizure, and died.

    On gross examination, the serosal surfaces of the large colon and cecum were ecchymotic  (FIGURE A) . The walls of the cecum and colon were markedly thickened and edematous, and the colonic and cecal lumens contained abundant, watery material. Most of the mucosal surface of the cecum and colon was ulcerated, with thick fibrin aggregates adhered to the ulcerated areas (FIGURE B) . Petechiae and ecchymoses were present over the serosal surfaces of the diaphragm, liver, epicardium, endocardium, and oral mucous membranes.

    1. What is your morphologic diagnosis?

    2. List three likely infectious etiologies of this lesion.

    3. What is the treatment protocol for each etiology?

    Answers and Explanations

    1. The gross morphologic diagnosis was severe, multifocal, acute, fibrinonecrotizing typhlocolitis. Histologic examination confirmed that the mucosal surface of the colon and cecum were variably ulcerated and necrotic. The submucosa was markedly expanded by hemorrhage, fibrin, edema fluid, and a large number of neutrophils.

    2. Likely etiologies include salmonellosis, Potomac horse fever, or clostridial enteritis.1 The bacteria isolated from the lesion were identified as Citrobacter amalonaticus.2 Citrobacter spp are closely related to Salmonella spp and are not a recognized cause of typhlocolitis in horses. Therefore, the 16S ribosomal DNA of the organism was amplified by polymerase chain reaction and sequenced, which showed that the bacteria had a 98% sequence homology with C. amalonaticus and Salmonella spp. Because the bacteria were isolated from necrotizing typhlocolitis, they were thought to most likely be Salmonella spp rather than Citrobacter spp. Bacterial speciation was not performed.

    3. Treatment of typhlocolitis focuses on supportive care and must address fluid loss, electrolyte imbalances, gastrointestinal inflammation, endotoxemia, and potential sepsis.1 The treatment regimens for these etiologies differ markedly. Treatment of salmonellosis using antimicrobials may be ill advised, as disruption in the patient’s natural flora may promote the development of disease. However, Potomac horse fever is most commonly treated with intravenous oxytetracycline. The treatment of clostridial disease varies according to clinical signs, but metronidazole is often used.1

                                                    *           *           *

    This case is a reminder that bacterial isolation, identification, and sequencing are not always definitive. The clinical history must be considered when bacteriology results are interpreted.

    1. Feary DJ, Hassel DM. Enteritis and colitis in horses. Vet Clin North Am Equine Pract 2006;22(2):437-479, ix.

    2. Gilchrist M. Enterobacteriaceae: opportunistic pathogens and other genera. In: Murray P, Baron E, Pfaller M, et al, eds. Manual of Clinical Microbiology. 6th ed. Washington, DC: American Society for Microbiology; 1995:457-464.

    References »

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