Non-invasive markers that are clinically useful for the diagnosis and monitoring of canine chronic enteropathies are scarce. The first aim of this study was to investigate the prevalence of cobalamin deficiency on a cellular level in dogs with chronic gastrointestinal disease by measuring serum methylmalonic acid (MMA) concentrations. Hypocobalaminemia has been associated with a negative outcome in dogs with chronic enteropathies, but the prevalence of cellular cobalamin deficiency is unknown. The second aim of this study was to determine the utility of fecal and urinary concentrations of N-methylhistamine (NMH) as a marker of gastrointestinal inflammation and disease activity in dogs with chronic enteropathies. Serum MMA concentrations were measured in healthy control dogs to establish a reference interval, which was calculated to be 415-1,193 nmol/L. Measurement of MMA concentrations in 555 serum samples from dogs with varying cobalamin concentrations showed a significant increase (p<0.05) in dogs with hypocobalaminemia. In a prospective group of 56 dogs with chronic enteropathies, 36% had decreased serum cobalamin concentrations, five of which (9% of 56 dogs) had increased serum MMA concentrations. We conclude that hypocobalaminemia is commonly seen in dogs with chronic gastrointestinal disease, but does not always appear to be associated with cellular cobalamin deficiency. In 47 dogs with chronic enteropathies, fecal and urinary NMH concentrations were increased in 21% and 27%, respectively, indicating that mast cell degranulation plays a role in a subset of dogs with chronic enteropathies. However fecal and urinary NMH concentrations did not correlate with each other, or with the clinical activity index. Urinary NMH concentrations correlated significantly with serum CRP concentrations, and were also significantly associated with severity of duodenal mucosal inflammation (p=0.008). The lack of correlation with the clinical activity index suggests that degranulation of mast cells only plays a role in some dogs with chronic enteropathies. Also, these results suggest that NMH alone may not be a good marker for clinical disease activity in dogs with chronic enteropathies. Due to its linear association with serum CRP and severity of mucosal inflammation, urinary NMH concentrations may be a better marker of intestinal inflammation than fecal NMH concentrations.

Background: Our innate immunesystem protects us from infections but, since its methods is not all specific for microorganisms, may also induce collateral damage. Severe physical injury often proved deadly throughout evolution. Such injuries may induce massive collateral damage. Nowadays we can initiate advanced critical care for affected patients and save them from imminent trauma-related death. We are therefore faced with the fact that the collateral damage from the immune system may pose a major threat to the patient, the pathophysiology of which is not amenable to direct medical treatment and which leaves us with only passive supportive measures. In this thesis we investigated the role of leucocytes under such circumstances. Our main aim was to understand better the role of leucocytes in the development of increased vascular permeability after burns and trauma. More specifically we investigated the impact of an injury on the function of leucocytes such as the dynamic change of certain cell-surface receptors on the leucocytes and in their numbers and immature forms. We wanted to find out if the increased pulmonary vascular permeability after a burn could be mediated through heparin binding protein (HBP) released from granuloctes, and whether HBP could be used as a biomarker for respiratory failure after trauma. We also wanted to confirm the possible role of histamine as a mediator of the systemic increase in vascular permeability after burns. Methods: The dynamic change of cell-surface receptors was measured by flow-acquired cytometer scanning (FACS) on blood samples taken after burns. The concentrations of HBP after a burn and mechanical trauma were analysed in plasma. Pulmonary vascular permeability after a burn was assessed using transpulmonary thermodilution. The histamine turnover after a burn was assessed with high performance liquid chromatography (HPLC) for concentrations of histamine and methylhistamine in urine. Results: We confirmed earlier investigations showing altered expression of receptors on leucocytes after a burn, receptors intimately associated with leucocyte functions (study I). In a pilot study of 10 patients we measured plasma concentrations of HBP and found them to be increased soon after a burn (study II). This finding was not confirmed in a larger, more extensive and specific study of 20 patients. We did, however, find an association between alterations in the number of leucocytes soon after a burn and pulmonary vascular permeability, indicating that they had a role in this process (study III). In another study of trauma (non burn) we found an association between the concentration of HBP in early plasma-samples after injury and the development of ARDS, indicating that granulocytes and HBP have a role in its aetiology (study IV). We found a small increase in urinary histamine and normal urinary methylhistamine concentrations but had anticipated a distinct increase followed by a decrease after reading the current papers on the subject. This indicates that the role of histamine as a mediator of increased vascular permeability after burns may have been exaggerated (study V). Conclusions: We conclude that leucocytes are affected by burns and trauma, and it is likely that they contribute to the development of respiratory failure and acute respiratory distress syndrome (ARDS). HBP is a candidate biomarker for the early detection of ARDS after trauma, and the white blood count (WBC) is a useful biomarker for the detection of decreased oxygenation soon after a burn.