Association between quantitative bacterial culture of bronchoalveolar lavage fluid and antibiotic requirement in dogs with lower respiratory tract signs.

BACKGROUND: Historically, positive bacterial cultures from the lower respiratory tract (LRT) have been considered clinically relevant when quantitative bacterial cultures of bronchoalveolar lavage fluid (BALF) were >1700 colony forming units (cfu)/mL. However, this threshold might not accurately predict a requirement for antibiotics. OBJECTIVES: To study whether quantitative BALF bacterial culture results were predictive of antibiotic requirement in dogs with LRT signs. ANIMALS: Thirty-three client-owned dogs. METHODS: Cross-sectional study. Dogs with positive quantitative bacterial culture of BALF were included. Dogs were divided into 2 groups, depending on whether they had a LRT infection requiring antibiotics (LRTI-RA) or LRT disease not requiring antibiotics (LRTD-NRA), based on thoracic imaging features, presence of intracellular bacteria on BALF cytology, and response to treatment. Predictive effect of cfu/mL and BALF total nucleated cell count (TNCC) on antibiotic requirement, adjusting for ongoing or prior antibiotic therapy and age, were studied using logistic regression. RESULTS: Twenty-two and 11 dogs were included in the LRTI-RA and LRTD-NRA groups, respectively. The cfu/mL was not significantly predictive of antibiotic requirement, independent of ongoing or prior antibiotic treatment and age (LRTI-RA: median, 10 000 cfu/mL; range, 10-3 × 108 ; LRTD-NRA: median, 10  000 cfu/mL; range, 250-1.3 × 109 ; P = .27). The TNCC was not significantly predictive of antibiotic requirement when only dogs with bronchial disease were considered (LRTI-RA: median, 470 cells/µL; range, 240-2260; LRTD-NRA: median, 455 cells/µL; range, 80-4990; P = .57). CONCLUSION AND CLINICAL IMPORTANCE: The cfu/mL is an inappropriate measure for determining whether antibiotics are of benefit in dogs with LRT signs.

Diagnostic performance of predicted ionized calcium in dogs with total hypercalcemia and total hypocalcemia.

BACKGROUND: Abnormal total calcium (tCa) values do not necessarily imply dysregulated ionized calcium. OBJECTIVES: We aimed to evaluate the diagnostic performance of predicted ionized calcium (piCa) regarding true calcium status in dogs with abnormal tCa. METHODS: This was a cross-sectional multicenter study. piCa and its prediction interval (PI) were calculated in 114 dogs, from three different hospitals, with either increased (62) or decreased tCa (52), All dogs also had ionized calcium and a biochemical profile available. The sensitivity, specificity, predictive values, and diagnostic discordance of piCa to confirm ionized hypercalcemia (iHyperCa) and ionized hypocalcemia (iHypoCa) were calculated using logistic regression analysis. RESULTS: iHyperCa was found in 28% and 66% of hyperphosphatemic and non-hyperphosphatemic dogs with tCa above the reference interval upper limit, respectively. The piCa correctly classified dogs with iHyperCa in 72.2% of those with hyperphosphatemia and 93.2% of those without hyperphosphatemia. Comparatively, elevating the tCa threshold to 12 mg/dL properly classified dogs 50% and 75% of the time in hyperphosphatemic and non-hyperphosphatemic dogs, respectively. iHypoCa was found in only 31/52 (60%) dogs with decreased tCa. The piCa correctly classified 55.2 to 100% of dogs with iHypoCa depending on the hospital. The PI demonstrated high sensitivity for iHyperCa (100%) and high specificity for both iHyperCa (100%) and iHypoCa (100%). CONCLUSIONS: Evaluating tCa alone does not reliably determine ionized calcium status. Even with hyperphosphatemia, piCa and its PI represent a reliable alternative to interpret abnormal tCa values when ionized calcium measurements are not available. However, if the tCa reference interval is notably different from 7.6 to 11.4 mg/dL, piCa values might be under/overestimated.

Evaluation of bronchial narrowing in coughing dogs with heart murmurs using computed tomography.

BACKGROUND: The origin of cough in dogs with heart murmurs is controversial, because the cough could be primary cardiac (eg, pulmonary edema, bronchi compression by left-sided cardiomegaly) or respiratory (eg, bronchomalacia, other bronchial or bronchiolar disease, interstitial lung disease) in origin. HYPOTHESIS/OBJECTIVES: To study the association between left atrium (LA) dilatation and cardiomegaly and bronchial narrowing in coughing dogs with heart murmurs using computed tomography (CT). ANIMALS: Twenty-one client-owned coughing dogs with heart murmurs and 14 historical control dogs. METHODS: Dogs with cough and murmur were prospectively recruited over 4 months. Cervical and thoracic radiography, echocardiography, and thoracic CT were performed in enrolled dogs. Control dogs, with no disease on thoracic CT and no records of heart murmur and coughing, were gathered from the institution's computerized database. Degree of bronchial narrowing was assessed using the bronchial-to-aorta (Ao) ratio, measured by 3 radiologists blinded to the clinical findings. After identifying bronchi that were significantly narrowed in dogs with murmur compared to controls, the relationship between degree of narrowing and LA/Ao ratio (measured echocardiographically) and vertebral heart scale (VHS) measured radiographically was studied in dogs with murmur using mixed-effects regression. RESULT: Significant narrowing was identified for all left-sided bronchi and the right principal, middle, and caudal bronchi in the coughing dogs, compared with controls. Increasing LA size and VHS were significantly inversely associated with diameter for all left-sided and right-sided bronchi indicated above. CONCLUSION AND CLINICAL IMPORTANCE: Results indicate an association between LA enlargement and cardiomegaly and bronchial narrowing and support heart size-associated exacerbation of cough in dogs with murmurs.