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若齢から成犬時に大きないびきがある犬が老齢になると慢性気管支炎になる理由

2017/01/25

以下の文献により、上気道閉塞とそれによる気道内乱流が粘液線毛系の障害を引き起こすと考えられている。そのため過剰な粘稠粘液が気道内に蓄積する可能性がある。いびきは、睡眠時の上気道閉塞が毎日ある証拠である。私の経験では、非短頭種で若齢期にいびきが大きい犬では早ければ7-8歳齢頃から、多くは12歳頃から慢性気管支炎を発症し、執拗な痰産生性咳が続くようになる。10年ほど慢性的かつ間欠的な強い上気道閉塞を繰り返すと、末梢気道系の粘膜上皮にも同様の不可逆性の障害を起こす可能性があり、慢性気管支炎を引き起こすかもしれない。非短頭種ではこの状況からさらに気管支拡張症に発展することがある。短頭種でも同様に慢性上気道閉塞を示し、老齢期に慢性気管支炎がパグによくみられる。ブルドッグは上気道閉塞は重度であり、パグに比べ短命であるので、慢性気管支炎が生じる前に喉頭虚脱や咽頭虚脱などの重度上気道閉塞によって息絶えてしまうのかもしれない。

-Mullins R, McAlinden AB, Goodfellow M. Subtotal epiglottectomy for the management of epiglottic retroversion in a dog. J Small Anim Pract 2014;55:383-385. <From Discussion>

”Interestingly, the dog had a productive cough with mucous demonstrated throughout the bronchial tree on tracheobronchoscopy and evidence of chronic active neutrophilic inflammation on BAL. This was believed to be attributable to mucociliary escalator dysfunction secondary to upper airway obstruction and turbulent airflow (Pink et al. 2006↓). It was considered that addressing the primary problem would lead to cough resolution. This was subsequently deemed plausible with cessation of coughing shortly after relief of the dynamic obstruction.”

 

 

-Pink JJ, Doyle RS, Hughes JM, et al. Laryngeal collapse in seven brachycephalic puppies. J Small Anim Pract 2006;47:131-135. <From Discussion>

Pink2006-Laryngeal Collapse in seven brachycephalic puppies_ページ_5

FIG 3. Cross-section of the trachea of case 5 (A) and a normal dog (B) showing replacement of the normal ciliated epithelium with a thin columnar epithelium and necrosis of a mucus gland. (H&E stain, 400)

 

 

 

 

 

“While five dogs responded favourably to surgical management, two dogs died. The excessive mucus present in the airways of case 5 combined with stage III laryngeal collapse are considered to have been responsible for the respiratory obstruction and subsequent death seen several hours after recovery from anaesthesia. Histopathological examination of the larynx and trachea revealed a loss of the normal ciliated epithelium and dysplasia of the mucus glands with associated inflammation. It is possible that the failure of normal ciliary clearance and abnormal mucus glands were responsible for the large quantities of abnormally tenacious mucus found at surgery. Whether loss of the normal respiratory epithelium and mucus gland dysplasia is found in other BAS cases requires further investigation. Some authors recommend prophylactic temporary tracheostomy when performing brachycephalic airway surgery (Monnet 2003). While temporary tracheostomy in case 5 would have prevented respiratory obstruction due to the laryngeal collapse, the excessive mucus present in the trachea of this case would have increased the risk of tracheostomy tube blockage. Case 3 died seven weeks following discharge from the hospital and a postmortem examination was not performed. While the cause of death cannot be certain, the owner’s description of severe and worsening dyspnoea is suggestive of respiratory obstruction with or without bronchopneumonia.”

 

最終更新日:2017年1月25日