Specialty Exams

Radiographs of the fetlock revealed soft-tissue swelling but no apparent damage to any 
bones. Localized infection of the joint is responsible for the increased opacity due to the 
large number of mononuclear cells that have migrated to the site.

Abnormalities on the clinical pathology report included decreased hematocrit and 
hemoglobin values, an abnormally high platelet count, a large number of mononuclear 
cells and a good result for mucin. The first two findings (hematocrit and hemoglobin) 
cannot be supported by any other clinical findings; given their closeness to the reference 
interval, one can assume that the reported values are within the norm for this patient. The 
last three findings should be considered clinically significant for this case because they 
support the radiographic findings of localized infection. The high platelet count reflects 
increased platelet production to support the bodyÕs effort to wall off the localized 
infection. The mononuclear cells are chemotactically drawn to the joint to phagocytize 
bacteria and associated debris. The mucin and the elevated protein level further support 
the diagnosis that the infection is in its early stages because the mucin clot is good and 
the protein level is below 4 g/dl.

Additionally, the joint fluid analysis showed pure positive growth of Klebsiella 
pneumoniae with sensitivity to amikacin, gentamicin, ceftiofur, chloramphenicol and 
enrofloxacin. In 50 percent of infectious arthritis cases, the culture and sensitivity are 
negative. Because this patient has a pure growth positive culture, we can conclude that 
this patient has infectious arthritis in the right hind fetlock.