兽研1. 引言
犬耳血肿是临床实践中常见的疾病，尽管其确切患病率仍不清楚[1,2,3]。其特征为耳廓凹面皮肤下出现充满血性浆液性渗出液的波动性肿胀[1,2,4]。出血的主要来源尚不明确。有假说认为其起源于位于软骨层内、下方或之间的耳大动脉和静脉分支[1,2,5]。该病由剧烈甩头或抓耳产生的剪切力触发，常与过敏性皮肤病、外耳炎和耳螨感染相关[1,5]。其他假说包括创伤、导致耳廓软骨撕裂的退行性过程，以及损伤软骨的炎症性和免疫介导过程[4,6,7]。使该病理认识复杂化的一种观点认为，犬耳血肿可能并非真正的血肿，而是随时间积累的血性浆液性渗出液[4]。由于确切病理生理机制尚未完全阐明，已尝试多种治疗方法；然而，迄今为止尚未建立明确的金标准治疗方案[3,5,7,8,9,10,11]。耳血肿的治疗目标包括识别并治疗任何潜在疾病以防止复发、建立充分引流、维持组织对合，以及保持耳部正常外观以避免过度增厚或瘢痕形成。
干扰素是具有广泛生物活性的细胞因子，凸显了其作为治疗药物的重大潜力[12,13]。其已记录的体内功能包括免疫调节、抗炎作用和抗肿瘤活性[12,13]。重组猫干扰素-ω（rFeIFN-ω；INTERCAT，Toray Industries, Inc.，东京，日本）于1994年首次开发并上市，作为猫杯状病毒感染的抗病毒药物[14]。迄今为止，rFeIFN-ω不仅对猫病毒感染显示出疗效，还对犬细小病毒感染有效[13,15,16,17,18,19,20]。此外，体外研究报告rFeIFN-ω对某些犬和猫肿瘤细胞具有抗增殖作用[13,21,22,23]。这些发现表明其治疗潜力远超感染性疾病的治疗，有望具有多样化的临床应用。
尽管犬耳血肿的详细病理生理机制仍不清楚，但抗炎治疗被认为有效[5,10,24]。因此，具有抗炎特性的rFeIFN-ω局部给药可能为治疗该病提供新方法，目前日本一些临床机构正在超说明书使用rFeIFN-ω治疗犬耳血肿。该治疗方案包括将rFeIFN-ω局部注射至血肿部位，同时口服泼尼松龙。然而，迄今为止尚无研究探讨rFeIFN-ω对犬耳血肿的治疗疗效。因此，本回顾性研究的目的是描述在一家私人动物医院接受该联合方案治疗的犬耳血肿的临床结局。
2. 病例介绍
2.1. 伦理声明
当确立耳血肿诊断时，在讨论替代方案之前，向宠物主人充分介绍了常规治疗选择，包括手术干预和针吸抽液。随后，详细告知宠物主人rFeIFN-ω局部给药构成对该病的超说明书（未经批准）应用。仅在主人选择该方案并提供明确知情同意后才开始治疗。
2.2. 动物与数据收集
本回顾性研究回顾了2019年1月至2026年1月期间在日本一家私立兽医医院（Takashimadaira Tezuka动物医院）就诊的耳血肿犬。最初，从电子病历系统中提取了共40只诊断为耳血肿的犬。其中，9只接受了替代治疗方案及不一致的治疗方案，被排除在本研究之外。这些替代方案包括：单纯针吸、针吸联合口服泼尼松龙、口服泼尼松龙、rFeIFN-ω（10.0 MU）单药治疗（不使用泼尼松龙）、低剂量rFeIFN-ω（5.0 MU）联合口服泼尼松龙、针吸联合耳部胶带固定，或无积极治疗。其余31只犬开始执行本研究治疗方案。在这31只犬中，5只在初次治疗后失访，随后被排除。因此，本研究最终评估了26只犬的分析队列。对每个病例，收集并评估以下临床数据：发病年龄、性别、品种、是否并发外耳炎、治疗次数总计、治疗成功率、复发及不良反应。排除标准包括治疗过程中失访的病例，以及接受了与下文所述不同的治疗方案的病例。关于临床结局，完全消退定义为通过视诊和触诊评估，患侧耳廓的厚度和外观恢复至与对侧未受累耳廓相当的水平，且无残留可触及的液体。临床改善定义为观察到血肿腔内积液较基线减少，但未达到完全消退。这些临床评估由主治兽医在每周就诊时通过常规体格检查进行；未使用卡尺测量、超声检查或标准化体积评分等客观工具。
2.3. 治疗方案
市售rFeIFN-ω（Intercat；Toray Industries, Inc.，东京，日本；图1）根据说明书用1 mL无菌生理盐水复溶。每只犬患侧耳廓表面用碘和酒精进行无菌准备。在没有任何全身麻醉或镇静的情况下，使用28号Myjector注射器将rFeIFN-ω以1.0 mL（10.0 MU）的剂量局部注射到耳血肿的波动性肿胀处。关键的是，在注射前或注射过程中未抽吸或排空血清血液性血肿液。固定剂量10.0 MU统一应用于所有犬， regardless of body weight, breed, or hematoma size。注射后立即对穿刺部位施加指压数分钟，以防止病灶内液体渗漏。同时，所有犬均口服泼尼松龙，初始剂量为1.0 mg/kg，每日一次。在整个治疗期间以该每日剂量继续口服泼尼松龙，仅在达到完全消退或方案终止后才逐渐减量。研究期间未给予额外的全身或局部药物，如耳用制剂、胃保护剂或其他抗炎药。以1周为间隔重新评估耳血肿的临床状态。如果未达到完全消退，则以上述相同方式进行rFeIFN-ω的重复局部给药。
[图：使用了重组猫干扰素-ω的商业制剂（Intercat；东丽工业株式会社，东京，日本）]
2.4. 数据分析
使用描述性统计对临床数据进行总结。定量变量，包括年龄和治疗次数，酌情以中位数（附范围）或平均值±标准差表示。定性变量，如性别、品种和是否并发外耳炎，以百分比表示。由于本研究的描述性性质及样本量，未进行正式的比较性统计分析或假设检验。精确95%置信区间使用Clopper-Pearson方法计算。所有数据分析使用GraphPad Prism 11.0版（GraphPad Software，圣地亚哥，加利福尼亚州，美国）进行。
2.5. 病例特征
研究期间共有31只犬接受了该治疗方案。其中，5只犬在治疗过程中失访，因此被排除，最终分析队列为26只犬（表S1）。这26只犬的基线人口学和临床特征总结于表1。就诊时的中位年龄为9岁（范围1–14岁）。研究群体包括15只雌性（57.7%；7只未绝育，8只已绝育）和11只雄性（42.3%；6只未去势，5只已去势）。就品种分布而言，最常见的品种为法国斗牛犬（n=5），其次为金毛寻回犬（n=4）和拉布拉多寻回犬（n=4）。其余队列包括以下品种各一只代表（各n=1）：比格犬、魏玛犬、美国可卡犬、威尔士柯基犬、标准贵宾犬、玩具贵宾犬、西高地白梗、柴犬、喜乐蒂牧羊犬、德国牧羊犬、马尔济斯犬、迷你杜宾犬和混种犬。26只犬中，11只犬（42.3%）就诊时并发外耳炎，需要积极的治疗干预。外耳炎的诊断基于病史和临床症状（如耳部瘙痒、摇头或耳道分泌物）结合耳镜检查显示红斑或肿胀而确立。这11只犬在就诊前未接受慢性耳炎的积极治疗；相反，外耳炎是在因耳血肿就诊时同时发现的。关于外耳炎的处理，在初次就诊时于rFeIFN-ω注射前使用无菌生理盐水进行院内耳道冲洗。未开具用于家庭使用的局部耳用药物（如抗菌或抗炎滴耳液）；管理仅依赖于所开具口服泼尼松龙的全身效应。
Table 1. Baseline characteristics of the 26 dogs.
| Parameter | Category/Value | Data |
|---|---|---|
| Total number of dogs | 26 | |
| Age (years) | Median (range) | 9 (1–14) |
| Sex [ n (%)] | Male (Intact/Castrated) | 11 (42.3%) [6/5] |
| Female (Intact/Spayed) | 15 (57.7%) [7/8] | |
| Breed [ n (%)] | French Bulldog | 5 (19.2%) |
| Golden Retriever | 4 (15.4%) | |
| Labrador Retriever | 4 (15.4%) | |
| Other breeds * ( n = 1) | 13 (50.0%) | |
| Otitis externa [ n (%)] | Present | 11 (42.3%) |
2.6. 临床结局
图2（病例9）展示了联合治疗前后病例的代表性临床外观。治疗前后的比较显示耳廓充满液体的肿胀明显减轻，证实成功保留了耳廓的正常物理结构，无严重畸形。
[图：重组猫干扰素联合疗法治疗犬耳血肿的代表性临床反应]
临床结局和治疗相关数据总结于表2。平均治疗次数为2.37±1.14次，范围为1–5次。所有病例均观察到临床改善（26/26，100%；95%CI：86.8–100.0%）。其中，26只犬中有21只在研究期间达到完全初步消退（80.8%；95%CI：60.7–93.5%）。具体而言，3只犬（14.3%）在1次治疗后消退，11只犬（52.4%）在2次后，4只犬（19.0%）在3次后，1只犬（4.8%）在4次后，2只犬（9.5%）需要5次。其余5只显示初步临床改善的犬未达到完全消退，因为主人选择拒绝进一步的每周治疗次数（例如对部分肿胀减轻感到满意或不愿重复临床就诊）。由于治疗方案未完成，这5例的最终长期结局仍不确定。
Table 2. Clinical outcomes following the combination treatment protocol.
| Clinical Parameter | Value/Rate | 95% Confidence Interval (CI) * |
|---|---|---|
| Number of treatment sessions (means ± SD) | 2.37 ± 1.14 | ― |
| Clinical improvement rate [ n / N (%)] | 26/26 (100%) | 86.8–100.0% |
| Complete initial resolution rate [ n / N (%)] | 21/26 (80.8%) | 60.7–93.5% |
| Recurrence rate [ n / N (%)] | 5/21 (23.8%) | 8.2–47.2% |
| Adverse effects | None recorded | ― |
在达到完全初步消退的21只犬中，5例（23.8%；95%CI：8.2–47.2%）记录到复发。这5例各自的复发时间分别为初次发作完全消退后2周、1个月、2个月、6个月和1年。在这5例复发病例中，2只犬使用rFeIFN-ω和口服泼尼松龙联合治疗再次治疗，而其余3只犬的主人拒绝进一步治疗，导致这些病例失去长期随访。值得注意的是，两只再次治疗的犬均达到完全和永久临床缓解，分别需要1次和2次额外治疗。任何病例均未记录到临床相关的全身或局部不良效应。然而，治疗后未进行常规血液学或生化随访评估。
3. 讨论
据我们所知，这是首篇描述病灶内注射rFeIFN-ω联合口服泼尼松龙治疗犬耳血肿后临床结局的报道。在本研究中，26只犬中有26只（100%）实现了临床改善，21只犬（80.8%）成功实现了初始完全消退（表2）。尽管其余5只犬显示出部分临床改善，但由于主人拒绝追加治疗次数，它们在完全消退前中止了方案。虽然这些病例不能被归类为确认的治疗失败，但由于方案不完整，其最终临床结局仍存在不确定性。这些初步临床观察表明，该联合方案可能代表一种可行的犬耳血肿非手术治疗选择。
探讨犬耳血肿特定治疗方式选择的研究仍然有限[3,5]。此前来自英国的一份报告指出，尽管经典推荐手术干预，但针吸抽液是最常实施的初始干预措施[3]。然而，传统手术干预存在已记录的局限性，包括术后耳廓变形、显著的复发率以及全身麻醉或镇静相关的固有风险[3,5,10]。近来，持续真空引流的手术技术已有报道，显示出高治愈率和极佳的美容效果[9]。尽管如此，该方法仍需要全身麻醉并需要专用设备，使其无法成为金标准治疗。相反，作为规避麻醉的非手术选择，已有若干方案被记录，成功率不一，包括口服泼尼松龙单药治疗（80%）、引流联合局部皮质类固醇滴注（43%）以及病灶内注射富血小板血浆（PRP）（100%）[7,10,11,24]。虽然这些非手术方法具有明显的操作优势，但研究设计、样本量、患者群体和结局定义的差异妨碍了跨研究直接比较疗效。在本研究中，我们观察到的初始完全消退率为80.8%，表明病灶内rFeIFN-ω联合口服泼尼松龙的方案代表了另一种可行的非手术选择，可在门诊环境中常规实施，无需麻醉或镇静。
本研究实施的治疗方案在操作简便性方面具有宝贵优势。由于rFeIFN-ω是市售产品，临床实践中易于获取。此外，给药前准备极少，仅需按照制造商的建议复溶产品即可。该操作本身无需麻醉或镇静即可安全实施；只需使用细针头向耳血肿的波动性肿胀处进行局部注射。准备和操作都极其简便，加之避免麻醉或镇静，使该方法成为麻醉风险高的患者的一种有吸引力且可行的替代方案。
在本研究中，联合方案平均需要2.37 ± 1.14次治疗才能实现初始完全消退（表2）。其特征是，该操作在不预先排空血肿液的情况下局部递送rFeIFN-ω。尽管该方法在穿刺部位引起了少量、短暂的病灶内液体渗漏，但注射后即刻未引起耳廓形态性肿胀或结构的明显宏观变化。然而，在有反应的病例中，观察到耳廓肿胀随时间依赖性逐渐消退。重要的是，本研究中观察到的治疗次数——以及 consequently 实现消退所需的总时间——与既往文献报道相当[10,11]。由于单次给药很少能实现完全消退，临床医生必须管理好预期，并在治疗前与客户充分沟通多次干预的必要性。
目前，缺乏确立rFeIFN-ω治疗耳血肿最佳剂量的科学数据。本研究中实施的10.0 MU剂量恰好对应一瓶市售产品，据推测该剂量的选择主要是为了制备操作的便利性。因此，未来非常有必要开展专门的剂量探索研究。然而，由于未进行剂量探索研究，最佳剂量仍属未知，应在未来的前瞻性研究中加以探讨。
关于治疗方案，本研究中所有病例均以1周间隔进行rFeIFN-ω局部给药。迄今为止，尚无确切的科学证据证实1周间隔是该特定病症的最佳给药方案；相反，该方案似乎是基于经验性兽医临床实践而被采用的。可以设想，缩短给药间隔可能会加速治疗反应并促进整体痊愈。因此，除最佳剂量外，未来需要开展时间顺序研究，以严格评估不同给药间隔对治疗效果和临床结局的影响。尽管如此，本研究的临床结局表明，在该队列中，1周治疗间隔是管理犬耳血肿的可行方案。
在本研究中，21例完全消退病例中有5例（23.8%）记录到复发（表2）。其中，2只犬在再次治疗后实现完全消退，而其余3只犬因主人选择不再进一步干预而失访。为有效预防复发，同时管理潜在原发疾病至关重要[5]；然而，在我们队列的5例复发病例中，仅有一只犬合并外耳炎。这提示其他机械性或退行性因素可能影响迟发性事件。值得注意的是，本研究中观察到的复发率高于既往报道的病灶内PRP治疗（0%）[10]，这可能代表本联合方案的潜在局限性或劣势。此外，各病例的复发时间差异很大，从消退后最早2周至最晚1年不等。此外，我们复发评估的一个主要局限性是缺乏标准化的消退后随访方案。由于本医疗记录审查的回顾性性质，实现完全消退的犬未常规安排长期定期复查，除非主人观察到新的临床症状。因此，无法统一确定未复发病例的确切长期随访时长，这可能影响所观察复发率的精确性。这种时间顺序一致性的缺乏，加上具有临床意义的复发率，强调了临床医生在实施该疗法时绝对有必要进行充分的治疗前沟通并向主人提供现实预期。
尽管局部注射rFeIFN-ω联合口服泼尼松龙的联合治疗的确切作用机制仍不清楚，但可推测其疗效涉及抗炎和抗增殖作用的联合。既往研究提示，口服泼尼松龙和局部注射PRP均通过其抗炎途径促进耳血肿愈合[10,11,24]。由于已有报道rFeIFN-ω在犬细小病毒感染犬中发挥抗炎作用，因此本研究观察到的治疗获益可能至少部分由rFeIFN-ω的抗炎特性介导[13,16,17,18]。此外，IFN-ω已被证明对多种肿瘤细胞具有体外抗增殖活性，包括猫纤维肉瘤和乳腺肿瘤细胞，以及犬恶性黑色素瘤和鳞状细胞癌[13,22,23,25]。可以推测，rFeIFN-ω也可能影响局部细胞反应，例如调节参与血肿腔形成的成纤维细胞或血管生成过程。然而，由于本研究未进行细胞学、组织学或分子学评估，这些机制解释仍纯属理论。需要专门的体外和体内研究来严格评估rFeIFN-ω对犬耳组织的抗炎和细胞效应。
在本研究中，接受局部注射rFeIFN-ω联合口服泼尼松龙联合治疗的犬均未表现出临床相关的不良反应。然而，由于本研究的回顾性性质，治疗前后实验室评估（如血液检查）和诊断影像学检查很少进行。为严格评估全身安全性特征，未来前瞻性试验应在治疗前后实施客观的实验室和影像学监测。值得注意的是，一只仅接受局部注射rFeIFN-ω 10.0 MU治疗的排除犬出现了以面部肿胀为特征的过敏反应。这一临床观察提示，同时口服泼尼松龙可能有助于降低rFeIFN-ω诱导的过敏反应风险[26,27]。然而，由于该过敏事件仅发生于单一病例，局部给予rFeIFN-ω继发超敏反应的真实发生率仍不清楚。有必要开展聚焦全身不良反应及确定安全最佳剂量范围的全面研究。
本研究观察到的良好临床结局可能不仅源于rFeIFN-ω的固有特性，还归因于口服泼尼松龙的协同抗炎作用[7,11]。此外，口服泼尼松龙同时对耳外炎和过敏性皮肤病等基础疾病具有高度疗效，而这些疾病常是耳血肿发生的主要病因[3,28,29,30]。鉴于IFN具有多种生理活性，rFeIFN-ω可能增强泼尼松龙对耳血肿的治疗效果。这种协同潜力可能通过增强泼尼松龙疗效而成为其他炎症性疾病的新型治疗策略，但理论上也存在加重皮质类固醇相关不良反应的风险[12]。尽管在本研究队列中未观察到明显的不良事件，但临床医生在使用该联合疗法时应谨慎考虑同时使用泼尼松龙的剂量。
目前缺乏关于犬耳血肿的流行病学研究[1,2]。基于本研究的结果，难以调查耳血肿的品种易感性。这是因为本研究为回顾性研究，且在单一特定的私立动物医院进行，无法进行排除地域偏倚或数量偏倚的评估。尽管法国斗牛犬、拉布拉多寻回犬和金毛寻回犬在本队列中相对常见，但样本量小和单中心回顾性设计使得无法就品种易感性作出任何推断。
解读本研究结果时应考虑若干局限性。首先，本研究中rFeIFN-ω的给药剂量仅限于10 MU，该剂量主要是基于局部给药的操作便利性和市售产品制剂规格而选择的。其次，由于本研究利用病历资料进行回顾性分析，我们无法标准化犬品种的分布或设立对照组。最值得注意的是，缺乏与泼尼松龙单药治疗组的比较，限制了我们明确将观察到的临床成功完全归因于rFeIFN-ω治疗效果的能力。此外，另一个主要局限性是我们临床结局评估的主观性。由于这是对常规病历的回顾性审查，未一致地进行客观定量测量，如卡尺测量耳廓厚度、超声液体量估算或标准化照片评分。因此，临床结局的判定依赖于主治临床医生的定性体格评估，这可能引入观察者主观性。有必要开展前瞻性随机对照试验，以提供关于该联合疗法疗效的更稳健、高质量的数据。第三，rFeIFN-ω对耳血肿发挥治疗作用的具体作用机制仍有待充分阐明。最后，目前仍缺乏rFeIFN-ω在犬患者中前瞻性且详细的安全性特征。尽管rFeIFN-ω已获商业批准用于猫传染病，但针对其在犬中给药的全面安全性研究仍然有限[17,18]。尽管在本研究队列中未记录到明显的全身性不良反应，但仍需进一步研究以确定犬中的精确安全范围和最佳给药方案。
4. 结论
总之，本回顾性研究表明，病灶内注射rFeIFN-ω联合口服泼尼松龙的方案与犬耳血肿良好的初期消退率相关，且无需全身麻醉或镇静。然而，鉴于回顾性设计和缺乏对照组，rFeIFN-ω的独立贡献仍未得到证实。有必要开展进一步的前瞻性和机制性研究，以验证这些临床发现并优化治疗方案。
缩写
本手稿中使用以下缩写：
| rFeIFN-ω | Recombinant feline interferon-omega |
补充材料
以下支持信息可从 https://www.mdpi.com/article/10.3390/vetsci13090937/s1 下载，表S1：病例及医疗详情。
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作者贡献
概念化，T.F.和T.T.（Takashi Tanaka）；方法学，T.F.和T.T.（Takashi Tanaka）；软件，M.N.；验证，T.F.和T.T.（Takashi Tanaka）；形式分析，T.F.、M.N.和T.T.（Takashi Tanaka）；调查，T.F.和T.T.（Takashi Tanaka）；资源，M.T.、T.T.（Tomoyuki Tezuka）和T.T.（Takashi Tanaka）；数据管理，T.F.和T.T.（Takashi Tanaka）；写作——原稿准备，T.F.；写作——审阅与编辑，T.F.、K.S.、M.T.、D.I.和T.T.（Takashi Tanaka）；可视化，T.F.；监督，K.S.、D.I.和T.T.（Tomoyuki Tezuka）；项目管理，T.T.（Takashi Tanaka）；资金获取，T.T.（Takashi Tanaka）。所有作者均已阅读并同意手稿的出版版本。
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1. Introduction
Canine aural hematoma is a frequently encountered condition in clinical practice, although its exact prevalence remains unknown [1,2,3]. It is characterized by a fluctuant swelling filled with serosanguinous exudate beneath the skin on the concave surface of the pinna [1,2,4]. The primary source of hemorrhage remains unclear. It has been hypothesized that it arises from branches of the great auricular artery and vein located within, beneath, or between the cartilage layers [1,2,5]. This condition is triggered by shearing forces generated by violent head shaking or ear scratching and is often associated with hypersensitive skin diseases, otitis externa, and ear mite infestations [1,5]. Other hypotheses include trauma, degenerative processes leading to tearing of the auricular cartilage, and inflammatory, immune-mediated processes that damage the cartilage [4,6,7]. Complicating the understanding of this pathology is the view that aural hematoma in dogs may not be a true hematoma, but rather a serosanguinous exudate that accumulates over time [4]. Because the precise pathophysiology remains incompletely elucidated, various treatments have been attempted; however, no definitive gold standard treatment has been established to date [3,5,7,8,9,10,11]. The therapeutic goals for managing aural hematoma include identifying and treating any underlying disease to prevent recurrence, establishing adequate drainage, maintaining tissue apposition, and preserving the normal appearance of the ear to avoid excessive thickening or scar formation.
Interferons are cytokines that possess a wide range of biological activities, highlighting their significant potential as therapeutic agents [12,13]. Their documented in vivo functions include immunoregulation, anti-inflammatory effects, and antitumor activities [12,13]. Recombinant feline interferon-omega (rFeIFN-ω; INTERCAT, Toray Industries, Inc., Tokyo, Japan) was first developed and marketed in 1994 as an antiviral drug for feline calicivirus infection [14]. To date, rFeIFN-ω has demonstrated efficacy not only against feline viral infection but also against canine parvovirus infection [13,15,16,17,18,19,20]. Furthermore, in vitro studies have reported that rFeIFN-ω exerts antiproliferative effects on certain canine and feline tumor cells [13,21,22,23]. These findings suggest that its therapeutic potential extends well beyond the treatment of infectious diseases, promising diverse clinical applications.
Although the detailed pathophysiology of canine aural hematoma remains unclear, anti-inflammatory therapy is considered effective [5,10,24]. Therefore, the local administration of rFeIFN-ω, which possesses anti-inflammatory properties, may offer a new approach to treating this condition, and rFeIFN-ω is currently being used off-label for the treatment canine aural hematoma in some clinical facilities in Japan. This treatment protocol involves the local injection of rFeIFN-ω into the hematoma site combined with concurrent oral prednisolone. However, to date, no studies have investigated the therapeutic efficacy of rFeIFN-ω for canine aural hematoma. Therefore, the purpose of this retrospective study was to describe clinical outcomes following this combination protocol in dogs with aural hematoma treated at a single private animal hospital.
2. Case Presentation
2.1. Ethics Statement
When a diagnosis of aural hematoma was established, conventional therapeutic options, including surgical intervention and needle aspiration, were fully presented to the owners prior to discussing the alternative regimen. Subsequently, pet owners were thoroughly informed that the local administration of rFeIFN-ω constituted an off-label (non-approved) application for this condition. Treatment was exclusively initiated only after the owners selected this option and provided explicit informed consent.
2.2. Animal and Data Collection
This retrospective study reviewed dogs with aural hematoma at a single private veterinary hospital (Takashimadaira Tezuka Animal Hospital) in Japan between January 2019 and January 2026. Initially, a total of 40 dogs diagnosed with aural hematoma were extracted from the electronic medical record system. Among these, 9 received alternative therapeutic regimens and inconsistent treatment protocol, and were excluded from this study. These alternative regimens included: needle aspiration alone, needle aspiration combined with oral prednisolone, oral prednisolone, rFeIFN-ω (10.0 MU) monotherapy without prednisolone, low-dose rFeIFN-ω (5.0 MU) with oral prednisolone, needle aspiration with ear taping, or no active treatment. The remaining 31 dogs initiated the study treatment protocol. Among these 31 dogs, 5 were lost to follow-up after the initial treatment session and were subsequently excluded. Consequently, a final analytical cohort of 26 dogs was evaluated in this study. For each case, the following clinical data were collected and evaluated: age at onset, sex, breed, presence of concurrent otitis externa, total number of treatment sessions, treatment success rate, recurrence, and adverse effects. The exclusion criteria consisted of cases that were lost to follow-up during the treatment course, and cases in which a treatment protocol different from those described below was administered. Regarding the clinical outcomes, complete resolution was defined as the visual and palpation-based assessment where the thickness and appearance of the affected pinna returned to a level comparable to the contralateral unaffected pinna, with no palpable fluid remaining. Clinical improvement was defined as an observed reduction in fluid accumulation within the hematoma cavity compared to baseline, without achieving complete resolution. These clinical evaluations were performed at each weekly visit through routine physical examination by attending veterinarians; objective tools such as caliper measurements, ultrasonography, or standardized volumetric scoring were not utilized.
2.3. Treatment Protocol
Commercially available rFeIFN-ω (Intercat; Toray Industries, Inc., Tokyo, Japan; Figure 1) was reconstituted in 1 mL of sterile saline according to the package insert. The affected pinnal surface of each dog was aseptically prepared using iodine and alcohol. Without any general anesthesia or sedation, rFeIFN-ω was administered locally into the fluctuant swelling of the aural hematoma at a dose of 1.0 mL (10.0 MU) using a 28-gauge Myjector syringe. Crucially, the serosanguinous hematoma fluid was not aspirated or evacuated prior to or during the injection procedure. The fixed dose of 10.0 MU was applied uniformly across all dogs, regardless of body weight, breed, or hematoma size. Immediately following the injection, digital pressure was applied to the puncture site for several minutes to prevent leakage of the intralesional fluid. Concurrently, all dogs were prescribed oral prednisolone at an initial dose of 1.0 mg/kg once daily. Oral prednisolone was continued at this daily dosage throughout the treatment period and was tapered off only after achieving complete resolution or protocol termination. No additional systemic or topical medications, such as otic preparations, gastroprotective agents, or other anti-inflammatory drugs, were administered during the study period. The clinical status of the aural hematoma was reassessed at 1-week intervals. If complete resolution was not achieved, repeat local administrations of rFeIFN-ω were performed in the same manner described above.
[图：Commercial formulation of recombinant feline interferon-omega (Intercat; Toray Industries, Inc., Tokyo, Japan) utilized ]
2.4. Data Analysis
Descriptive statistics were used to summarize the clinical data. Quantitative variables, including age and the number of treatment sessions, were expressed as median (with ranges) or means ± standard deviations, as appropriate. Qualitative variables, such as sex, breed, and the presence of concurrent otitis externa, were presented as percentages. No formal comparative statistical analysis or hypothesis testing were performed due to the descriptive nature and sample size of this study. Exact 95% confidence intervals were calculated using the Clopper-Pearson method. All data analyses were performed using GraphPad Prism version 11.0 (GraphPad Software, San Diego, CA, USA).
2.5. Case Characteristics
A total of 31 dogs underwent the treatment protocol during the study period. Of these, 5 dogs were lost to follow-up during the treatment course and consequently excluded, resulting in a final analytical cohort of 26 dogs (Table S1). The baseline demographic and clinical characteristics of these 26 dogs are summarized in Table 1. The median age at presentation was 9 years (range, 1–14 years). The study population included 15 females (57.7%; 7 intact and 8 spayed) and 11 males (42.3%; 6 intact and 5 castrated). In terms of breed distribution, the most frequently affected breeds were French Bulldogs (n = 5), followed by Golden Retrievers (n = 4) and Labrador Retrievers (n = 4). The remaining cohort comprised one representative each of the following breeds (n = 1 each): Beagle, Weimaraner, American Cocker Spaniel, Welsh Corgi, Standard Poodle, Toy Poodle, West Highland White Terrier, Shiba Inu, Shetland Sheepdog, German Shepherd, Maltese, Miniature Pinscher, and Mixed-breed. Of the 26 dogs, 11 dogs (42.3%) presented with concurrent otitis externa that required active therapeutic intervention. The diagnosis of otitis externa was established based on history and clinical signs (e.g., aural pruritus, head shaking, or ear discharge) combined with otoscopic examination demonstrating erythema or swelling. These 11 dogs were not under active treatment for chronic otitis prior to presentation; rather, otitis externa was identified concurrently upon presentation for the aural hematoma. Regarding the management of otitis externa, in-clinic ear flushing with sterile saline was performed during the initial visit prior to the rFeIFN-ω injection. No topical otic medications (e.g., antimicrobial or anti-inflammatory ear drops) were prescribed for home use; management relied solely on the systemic effect of the prescribed oral prednisolone.
Table 1. Baseline characteristics of the 26 dogs.
| Parameter | Category/Value | Data |
|---|---|---|
| Total number of dogs | 26 | |
| Age (years) | Median (range) | 9 (1–14) |
| Sex [ n (%)] | Male (Intact/Castrated) | 11 (42.3%) [6/5] |
| Female (Intact/Spayed) | 15 (57.7%) [7/8] | |
| Breed [ n (%)] | French Bulldog | 5 (19.2%) |
| Golden Retriever | 4 (15.4%) | |
| Labrador Retriever | 4 (15.4%) | |
| Other breeds * ( n = 1) | 13 (50.0%) | |
| Otitis externa [ n (%)] | Present | 11 (42.3%) |
2.6. Clinical Outcomes
The representative clinical appearance of a case before and after the combination therapy was illustrated in Figure 2 (Case 9). A comparison between before and after the treatment demonstrated a marked reduction in the fluid-filled swelling of the pinna, confirming the successful preservation of the normal physical structure of the ear flap without severe deformity.
[图：Representative clinical responses of a canine aural hematoma treated with the combination therapy of recombinant feline ]
The clinical outcomes and treatment-related data are summarized in Table 2. The mean number of treatment sessions was 2.37 ± 1.14, with a range of 1–5 sessions. Clinical improvement was recognized in all cases (26/26, 100%; 95% CI: 86.8–100.0%). Among them, complete initial resolution during the study period was achieved in 21 out of the 26 dogs (80.8%; 95% CI, 60.7–93.5%). Specifically, 3 dogs (14.3%) resolved after 1 session, 11 dogs (52.4%) after 2 sessions, 4 dogs (19.0%) after 3 sessions, 1 dog (4.8%) after 4 sessions, and 2 dogs (9.5%) required 5 sessions. The remaining 5 dogs that demonstrated initial clinical improvement did not achieve complete resolution because the owners elected to decline further weekly treatment sessions (e.g., satisfaction with partial swelling reduction or reluctance for repeated clinical visits). Because the treatment protocol was not completed, the ultimate long-term outcomes for these 5 cases remain undetermined.
Table 2. Clinical outcomes following the combination treatment protocol.
| Clinical Parameter | Value/Rate | 95% Confidence Interval (CI) * |
|---|---|---|
| Number of treatment sessions (means ± SD) | 2.37 ± 1.14 | ― |
| Clinical improvement rate [ n / N (%)] | 26/26 (100%) | 86.8–100.0% |
| Complete initial resolution rate [ n / N (%)] | 21/26 (80.8%) | 60.7–93.5% |
| Recurrence rate [ n / N (%)] | 5/21 (23.8%) | 8.2–47.2% |
| Adverse effects | None recorded | ― |
Among the 21 dogs that achieved complete initial resolution, recurrence was documented in 5 cases (23.8%; 95% CI: 8.2–47.2%). The time to recurrence for each of these 5 cases was 2 weeks, 1 month, 2 months, 6 months, and 1 year following the complete resolution of the initial episode, respectively. Out of these 5 recurrent cases, 2 dogs underwent re-treatment using the combination treatment of rFeIFN-ω and oral prednisolone, while the owners of the remaining 3 dogs declined further treatment, resulting in these cases being lost to long-term follow-up. Notably, both of the re-treated dogs achieved complete and permanent clinical remission, requiring 1 and 2 additional treatment sessions, respectively. No clinically relevant systemic or localized adverse effects were recorded in any of the cases. However, routine hematological or biochemical follow-up evaluations were not performed post-treatment.
3. Discussion
To the best of our knowledge, this is the first report describing clinical outcomes following intralesional rFeIFN-ω injection combined with oral prednisolone for canine aural hematoma. In this study, clinical improvement was achieved in 26 out of 26 dogs (100%), and complete initial resolution was successfully achieved in 21 dogs (80.8%) (Table 2). Although the remaining 5 dogs showed partial clinical improvement, they discontinued the protocol prior to complete resolution because the owners declined additional treatment sessions. While these cases cannot be classified as confirmed therapeutic failures, their final clinical outcomes remain undermined due to the incomplete protocol. These preliminary clinical observations suggest that this combination protocol may represent a feasible non-surgical management option for canine aural hematoma.
Studies investigating the specific treatment modalities selected for canine aural hematoma remain limited [3,5]. A previous report from the UK indicated that needle aspiration is the most frequently performed initial intervention, although surgical intervention is classically recommended [3]. However, conventional surgical interventions carry documented limitations, including postoperative pinnal deformity, notable recurrence rates, and inherent risks associated with general anesthesia or sedation [3,5,10]. Recently, the surgical technique of continuous vacuum drainage has been reported, demonstrating a high cure rate with excellent cosmetic outcomes [9]. Nevertheless, this approach still mandates general anesthesia and requires specialized equipment, precluding it from becoming the gold standard treatment. Conversely, as non-surgical options that circumvent anesthesia, several protocols have been documented with varying success rates, including oral prednisolone monotherapy (80%), drainage combined with local corticosteroid instillation (43%), and intra-lesional platelet-rich plasma (PRP) injection (100%) [7,10,11,24]. While these non-surgical approaches offer distinct procedural advantages, direct comparisons of therapeutic efficacy across studies are precluded by differences in study designs, sample size, patient populations, and outcome definitions. In this study, our observed initial complete resolution rate of 80.8% suggests that the combination protocol of intralesional rFeIFN-ω and oral prednisolone represents another feasible non-surgical option that can be routinely performed in an outpatient setting without anesthesia or sedation.
The treatment protocol implemented in this study offers a valuable advantage in terms of its procedural simplicity. Because rFeIFN-ω is a commercially available product, it is easily accessible for clinical practice. Furthermore, the pre-administration preparation is minimal, requiring only the reconstitution of the product according to the manufacturer’s recommendations. The procedure itself can be performed safely without anesthesia or sedation; it simply involves a local injection into the fluctuant swelling of the aural hematoma using a fine-gauge needle. The exceptional simplicity of both the preparation and the procedure, combined with the avoidance of anesthesia or sedation, makes this approach an attractive and viable alternative for patients with high anesthetic risks.
In the present study, the combination protocol required a mean of 2.37 + 1.14 treatment sessions to achieve initial complete resolution (Table 2). Characteristically, this procedure delivers rFeIFN-ω locally without prior evacuation of the hematoma fluid. Although this approach induced a minor, transient leakage of intralesional fluid at the puncture site, it caused no immediate gross changes in the conformational swelling or architecture of the pinna immediately post-injection. In responsive cases, however, a progressive, time-dependent regression of the pinnal swelling was observed. Importantly, the number of treatment sessions—and consequently the overall time required for resolution—observed in the present study was comparable to those reported in previous literature [10,11]. As a single administration rarely yields complete resolution, it is paramount that clinicians manage expectations and ensure thorough pre-treatment communication with clients regarding the necessity of multiple interventions.
Currently, there is a lack of scientific data establishing the optimal dosage of rFeIFN-ω for aural hematoma. The dose of 10.0 MU implemented in the present study corresponds to exactly one vial of the commercially available product, and it is inferred that this dosage was selected primarily for its procedural ease of preparation. Consequently, future dedicated dose-finding studies are highly warranted. However, because no dose-finding study was performed, the optimal dose remains unknown and should be investigated in future prospective studies.
Regarding the treatment schedule, local administration of rFeIFN-ω was performed at 1-week intervals in all cases in this study. To date, there is no definitive scientific evidence validating that a 1-week interval is the optimal dosing schedule for this specific condition; rather, this regimen appears to have been adopted based on empirical veterinary clinical practices. It is conceivable that shortening the dosing interval might accelerate the therapeutic responses and expedite overall resolution. Consequently, along with the optimal dosage, future chronological studies are warranted to rigorously evaluate the impact of different dosing intervals on both therapeutic efficacy and clinical outcomes. Nevertheless, the clinical outcomes of the present study suggest that, in this cohort, a 1-week treatment interval was feasible protocol for the management of canine aural hematoma.
In the present study, recurrence was documented in 5 out of the 21 completely resolved cases (23.8%) (Table 2). Of these, 2 dogs achieved complete resolution following re-treatment, whereas the remaining 3 dogs were lost to follow-up due to the owner’s preference for no further intervention. To effectively prevent recurrence, concurrent management of underlying primary diseases is critical [5]; however, among the 5 recurrent cases in our cohort, only a single dog was affected by concurrent otitis externa. This suggests other mechanical or degenerative factors might influence late-onset events. Notably, the recurrence rate observed in this study is higher than that previously reported for intra-lesional PRP therapy (0%) [10], which could represent a potential limitation or disadvantage of the present combination protocol. Furthermore, the time to recurrence was highly variable among individual cases, ranging from as early as 2 weeks to as late as 1 year post-resolution. In addition, a major limitation regarding our recurrence evaluation is the lack of a standardized post-resolution follow-up protocol. Because of the retrospective nature of this medical record review, dogs that achieved complete resolution were not routinely scheduled for long-term periodic re-examinations unless owners observed new clinical signs. Consequently, exact long-term follow-up durations for non-recurrent cases could not be uniformly established, which may affect the precision of the observed recurrence rate. This lack of chronological uniformity, coupled with the clinically relevant recurrence rate, underscores the absolute necessity for clinicians to provide thorough pre-treatment communication and realistic expectations to owners when implementing this therapy.
Although the exact mechanism of action underlying the combination therapy of local rFeIFN-ω injection and oral prednisolone remains unclear, its efficacy may be hypothesized to involve combined anti-inflammatory and antiproliferative effects. Previous studies have suggested that both oral prednisolone and local PRP injections promote the healing of aural hematomas through their anti-inflammatory pathways [10,11,24]. Because rFeIFN-ω has been reported to exert anti-inflammatory effects in dogs with canine parvovirus infection, it may be possible that the therapeutic benefits observed in this study were mediated, at least in part, by the anti-inflammatory properties of rFeIFN-ω [13,16,17,18]. Furthermore, IFN-ω has been shown to possess in vitro antiproliferative activities against various tumor cells, including feline fibrosarcoma and mammary tumor cells, as well as canine malignant melanoma and squamous carcinoma [13,22,23,25]. It can be speculated that rFeIFN-ω might also influence local cellular responses, such as modulating fibroblasts or angiogenic processes involved in hematoma cavity formation. However, because cytological, histological, or molecular evaluations were not performed in the present study, these mechanistic explanations remain purely theoretical. Dedicated in vitro and in vivo studies are necessary to rigorously evaluate the anti-inflammatory and cellular effects of rFeIFN-ω on canine auricular tissues.
In the present study, no dogs undergoing the combination therapy of local rFeIFN-ω injection and oral prednisolone exhibited clinically relevant adverse effects. However, due to the retrospective nature of this study, pre- and post-treatment laboratory evaluations (e.g., blood tests) and diagnostic imaging were rarely performed. To rigorously evaluate the systemic safety profile, objective laboratory and imaging monitoring before and after therapy should be implemented in future prospective trials. Notably, one excluded dog treated with local rFeIFN-ω 10.0 MU injection alone developed an allergic reaction characterized by facial swelling. This clinical observation suggests that concurrent oral prednisolone administration may play a role in mitigating the risk of rFeIFN-ω-induced allergic reactions [26,27]. Nevertheless, because this allergic event occurred in only a single case, the true incidence of hypersensitivity reactions secondary to local rFeIFN-ω administration remains unclear. Comprehensive investigations focusing on systemic adverse effects and the determination of a safe and optimal dosage range are essential.
The favorable clinical outcomes observed in this study may stem not only from the intrinsic properties of rFeIFN-ω but also from the concurrent anti-inflammatory action of oral prednisolone [7,11]. Furthermore, oral prednisolone is simultaneously highly effective for managing underlying conditions, such as otitis externa and allergic skin diseases, which frequently serve as the primary etiologies for the development of aural hematoma [3,28,29,30]. Given the diverse physiological activities of IFN, rFeIFN-ω may potentiate the therapeutic efficacy of prednisolone against aural hematomas. While this synergistic potential could represent a novel therapeutic strategy for other inflammatory diseases by enhancing prednisolone efficacy, it also carries a theoretical risk of exacerbating corticosteroid-related adverse effects [12]. Although no obvious adverse events were noted in our cohort, clinicians should exercise caution regarding the dosage of concurrent prednisolone when utilizing this combination therapy.
There is a lack of epidemiological studies regarding canine aural hematoma [1,2]. Based on the results of the present study, it is difficult to investigate the breed predisposition to aural hematoma. This is because the present study is retrospective and was conducted at a single, specific private animal hospital, making it impossible to perform an evaluation that excludes regional bias or numerical bias. Although French Bulldogs, Labrador Retrievers, and Golden Retrievers were relatively frequent in this cohort, the small sample size and single-center retrospective design preclude any inference regarding breed predisposition.
Several limitations should be considered when interpreting the findings of this study. First, the doses of rFeIFN-ω administered in this study were limited to either 10 MU, which were selected primarily for procedural ease of local administration and based on the commercially available product formulations. Second, due to the retrospective nature of this study utilizing medical records, we were unable to standardize the distribution of dog breeds or establish a control group. Most notably, the lack of a comparison with a prednisolone monotherapy group limits our ability to definitively attribute the observed clinical success solely to the therapeutic effects of rFeIFN-ω. Furthermore, another major limitation is the subjective nature of our clinical outcome assessment. Because this was a retrospective review of routine medical records, objective quantitative measurements, such as caliper measurements of pinna thickness, ultrasonographic fluid volume estimation, or standardized photographic scoring, were not consistently performed. Consequently, clinical outcome determinations relied on qualitative physical evaluations by attending clinicians, which may introduce observer subjectivity. Prospective randomized controlled trials are warranted to provide more robust, high-quality data regarding the efficacy of this combination therapy. Third, the detailed mechanism of action by which rFeIFN-ω exerts its therapeutic effects on aural hematomas remains to be fully elucidated. Finally, prospective and detailed safety profiles of rFeIFN-ω in canine patients are still lacking. Although rFeIFN-ω is commercially approved for feline infectious diseases, comprehensive safety studies focusing on its administration in dogs remain limited [17,18]. Although no obvious systemic adverse effects were documented in our cohort, further investigation is essential to establish the precise safety margin and optimal dosing regimen in dogs.
4. Conclusions
In conclusion, this retrospective study demonstrates that a combination protocol of intralesional rFeIFN-ω injection and oral prednisolone was associated with favorable initial resolution rates in dogs with aural hematoma, without requiring general anesthesia or sedation. However, given the retrospective design and absence of a control group, the independent contribution of rFeIFN-ω remains unproven. Further prospective and mechanistic studies are warranted to validate these clinical findings and optimize the treatment protocol.
Abbreviation
The following abbreviation is used in this manuscript:
| rFeIFN-ω | Recombinant feline interferon-omega |
Supplementary Materials
The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/vetsci13090937/s1, Table S1: Cases and medical details.
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Author Contributions
Conceptualization, T.F. and T.T. (Takashi Tanaka); methodology, T.F. and T.T. (Takashi Tanaka); software, M.N.; validation, T.F. and T.T. (Takashi Tanaka); formal analysis, T.F., M.N. and T.T. (Takashi Tanaka); investigation, T.F. and T.T. (Takashi Tanaka); resources, M.T., T.T. (Tomoyuki Tezuka) and T.T. (Takashi Tanaka); data curation, T.F. and T.T. (Takashi Tanaka); writing—original draft preparation, T.F.; writing—review and editing, T.F., K.S., M.T., D.I. and T.T. (Takashi Tanaka); visualization, T.F.; supervision, K.S., D.I. and T.T. (Tomoyuki Tezuka); project administration, T.T. (Takashi Tanaka); funding acquisition, T.T. (Takashi Tanaka). All authors have read and agreed to the published version of the manuscript.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Informed consent was obtained from the owners of all subjects involved in the study.
Data Availability Statement
The original contributions presented in this study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.
Conflicts of Interest
The authors declare no conflicts of interest.
Funding Statement
This research received no external funding.
Footnotes
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References
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Associated Data
Supplementary Materials
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Data Availability Statement
The original contributions presented in this study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.