兽研1. 引言
腹膜心包膈疝（PPDH）是一种先天性畸形，其特征为腹膜腔与心包囊之间存在持续性交通，由胚胎发育过程中横膈未能与胸腹膜正常融合所致[1]。PPDH是犬和猫最常见的先天性心包异常[2,3]。虽然真实患病率较低——估计占住院犬的0.015%——但该病可能被低估诊断，因为部分患病动物终生无症状[4,5]。
PPDH的临床表现多样，取决于疝入腹腔器官的类型和数量、心肺受压程度以及是否存在嵌顿。最常见的就诊症状包括呼吸系统症状（呼吸困难、呼吸急促、喘气）和胃肠道症状（呕吐、厌食、腹泻），其呼吸系统症状在猫中更为常见，胃肠道症状在犬中更为常见[2,3]。心音减弱或低沉是特征性体格检查发现，由疝入的腹腔器官使心脏移位所致[6,7]。
PPDH的诊断主要通过诊断性影像学实现。胸部X线摄影通常显示心影明显增大、气管向背侧移位以及膈肌边缘模糊[1,2]。腹部超声和超声心动图可直接观察疝入器官并评估心脏结构和功能[7,8]。计算机断层扫描（CT）可详细描述膈肌缺损特征并有助于手术规划[9,10]。
手术治疗是出现归因于PPDH临床症状动物的首选治疗方案[2,4]。一项涉及128只犬的多中心研究报告，97%接受手术治疗的犬出院；87只犬获得了中位1062天的长期随访，未报告任何接受手术治疗的犬出现疝复发[5]。直接对合膈肌边缘的一期闭合是首选技术；然而，占膈肌相当大部分的大型缺损可能无法实现无张力闭合。在此类情况下，可能需要采用替代技术，包括心包瓣重建、腹侧膈肌推进术、肌瓣转位术或生物材料补片植入[11,12]。
小肠黏膜下层（SIS）是一种无细胞细胞外基质生物材料，据报道可促进位点特异性宿主组织重塑和新生血管形成，同时在组织再生期间提供临时机械支撑。猪源SIS（pSIS）和犬源SIS（cSIS）均已用于犬疝修补；然而，pSIS研究更为广泛且已商业化，而cSIS尚未商业化[13,14]。这些移植物类型之间存在重要的理论免疫学差异：pSIS含有贯穿整个支架全层分布的Galα(1,3)Gal（α-Gal）表位，可能在非猪受体中引发异种免疫反应[15]；而cSIS——作为犬患者中的同种异体移植物——本身不带有该抗原负荷[16]。尽管存在这一理论考量，cSIS的临床证据仍仅限于一份关于两只犬会阴疝修补术的报告，术后12个月无排斥或复发迹象[14]。据作者所知，此前尚未有使用cSIS加强犬大型PPDH缺损的报道。本病例报告描述了一例大型先天性PPDH的手术处理，采用一期修复联合cSIS补片加强，术后发生边缘再疝形成，以及随后利用cSIS应用部位形成的假定自体组织成功再修复。
2. 病例介绍
一只2岁未绝育雌性白色迷你雪纳瑞犬，体重6.23 kg，因1个月来散步时喘气、兴奋和运动不耐受被转诊至建国大学兽医教学医院进行评估。主人报告临床症状逐渐加重，并由体力活动诱发或加剧。无外伤史，该犬除此之外健康状况良好，无既往手术或内科疾病。就诊时该犬未服用任何药物。
体格检查时，该犬体温39.1 °C，心率132次/分，呼吸频率48次/分。听诊最显著的发现是心音低沉，尤其在右侧胸腔。体格检查未检测到其他异常。
血液学和血清生化分析均在参考范围内（表1）。未发现提示肝功能障碍、代谢性疾病或其他全身性疾病的异常。
胸部X线摄影（右侧位和腹背位）显示心影大而呈球形，心尖向右移位（图1）。膈肌边缘模糊。这些发现与心脏增大一致，形态学上可疑为PPDH[1,3]。
由单一检查者在患犬背侧卧位下使用7.5 MHz探头进行的腹部超声检查证实肝叶疝入心包囊内（图2A）。彩色多普勒评估证实疝入肝叶内存在血流信号（图2B），在定性层面排除了血管受损或嵌闭；未使用或记录超声造影及定量多普勒参数（如收缩期峰值流速和阻力指数）。
超声心动图显示心包囊内右心旁存在回声性与肝组织一致的结构。未发现疝入肝脏与心包或心脏表面嵌闭或粘连的证据。重要的是，心脏结构和功能正常，未检测到先天性心脏异常或功能缺陷。
为进一步明确膈肌缺损范围并评估是否存在其他先天性异常，在全身麻醉下进行了增强胸部及腹部CT检查。生成了横断面、矢状面和背侧面的多平面重建（MPR）图像以用于手术规划。CT证实心包囊内存在一肝叶，疝入器官的占位效应使心脏向左侧移位（图3）。在矢状面和背侧面MPR图像上评估了疝的头尾范围及膈肌缺损位置。未发现其他先天性异常，包括胸骨异常或额外的腹壁缺损。
患犬术前给予丁丙诺啡（10 μg/kg，IM；Renolphan，Hanlim Pharm，韩国龙仁市）和咪达唑仑（0.3 mg/kg，IV；Vascam，HaNa Pharm，韩国首尔市）。使用丙泊酚（6 mg/kg，IV；Anepol，HaNa Pharm，韩国首尔市）诱导全身麻醉，并以2%异氟烷（Forane，ChoongWae Pharma，韩国果川市）在100%氧气中维持。使用布比卡因（0.5 mg/kg；Bupivacaine 0.5%，HaNa Pharm，韩国首尔市）与丁丙诺啡（10 μg/kg；Renolphan，Hanlim Pharm，韩国龙仁市）的混合液实施硬膜外麻醉。通过从剑突延伸至耻骨的中线开腹术进行手术修复。开腹探查确认左内侧肝叶和方叶经膈肌缺损疝入心包囊内（图4）。将疝入的肝叶小心还纳回腹腔。疝入肝脏与心包或心脏结构之间无粘连。
还纳疝入肝叶后，于膈肌中心腱处确认膈肌缺损。CT上膈肌胸膜面总体尺寸为11 × 11 cm。缺损大小约为4.5 × 5 cm，约占膈肌总面积的21%，约占中心腱面积的70%（图4）。
首先尝试从缺损背侧缘向腹侧缘缝合进行一期修复。仅在缺损背侧缘放置了两针简单间断缝合；由于缺损较大且残余中心腱组织有限，使缝线张力过大，无法进一步对合腹侧部分，因此仅靠一期修复无法完全闭合缺损。结果，原缺损腹侧仍残留缺损；呈三角形，大小超过3 × 3 cm。
因此，为加强未完全闭合的缺损，将一块5 × 5 cm的犬小肠黏膜下层（cSIS）补片对折制成双层（2层）移植物，并缝合覆盖于残余缺损上（图4）。选择2层构型是基于术者术中判断，即两层可提供足够的厚度和强度，既能覆盖残余缺损，又能加强部分完成的一期修复。cSIS按Lee等[17]验证的方法制备。简言之，通过机构犬组织捐赠项目获取空肠段。在获得客户书面知情同意后，从客户拥有的成年犬获取组织，这些犬除潜在神经功能缺陷外无全身性疾病，并因与本无关的医疗原因被安乐死。所有标本均在安乐死后2小时内采集，并用无菌生理盐水彻底冲洗。
通过机械摩擦去除黏膜、肌层和浆膜，剩余黏膜下层在无菌生理盐水和80%乙醇中彻底冲洗以去除细胞降解产物。cSIS在使用前于含抗生素（盐酸林可霉素、盐酸万古霉素和头孢噻肟）的无菌生理盐水中4 °C保存7天[17]。cSIS补片以4-0单股聚乙醇酸酯缝线（Maxon；Covidien，Fridley，MN，USA）采用简单间断缝合模式以2–3 mm间距固定于周围膈肌边缘，每针均全层贯穿膈肌；移植物直接与残余缺损边缘对合，不重叠周围自体膈肌，未放置额外加强（垫片）缝线。皮下组织以4-0 Maxon缝线（Covidien，USA）闭合，皮肤以3-0单股聚酰胺缝线（Dafilon；B. Braun，Melsungen，Germany）闭合。手术历时83分钟，总麻醉时间95分钟；术中失血量估计少于10 mL，未放置胸腔或腹腔引流。
犬从麻醉中顺利苏醒。丁丙诺啡（10 µg/kg，IM）作为镇痛药每8小时给药一次，持续2天，头孢氨苄（22 mg/kg）治疗继续每日两次，持续14天。住院期间使用格拉斯哥复合疼痛量表简表（GCMPS-SF）监测术后疼痛；所有评估时疼痛评分均保持较低水平并持续低于推荐的镇痛干预阈值（6/24），无需补救镇痛。术后住院3天，期间监测犬只呼吸窘迫、气胸及其他术后并发症。未观察到明显术后并发症。术后11天拆除皮肤缝线。
拆线时随访胸部X线摄影显示心影大小正常，先前观察到的球形心脏增大已消退（图5A）。腹部超声检查确认cSIS补片在缺损部位保持良好，无再疝证据（图5B）。
术后42天，体格检查无异常；然而，胸部X线摄影显示心影增大至长轴测量值接近术前值（90.8 mm）（图6A）。腹部超声检查显示一结构与肝叶一致，疝入心包囊内（图6B），超声评估未见疝出组织与心脏之间粘连证据。基于这些影像学发现，诊断为再疝。由于诊断已通过X线摄影和超声检查确立，且重复CT将需要在被认为麻醉风险相对较高的患者中另行实施一次麻醉事件，故未重复CT；而是在手术修复所需的单次麻醉期间通过直接可视化评估复发解剖结构。犬随后经中线开腹行第二次手术。麻醉方案与第一次手术相同；第二次手术历时49分钟，总麻醉时间58分钟，术中失血量估计少于5 mL，未放置引流装置。探查时，在自体膈肌与cSIS应用部位之间的边缘发现缺损；cSIS补片本身完整，似乎已整合入周围膈肌组织，表明再疝发生于补片–宿主组织界面而非补片破裂处（图6C）。通过该边缘缺损，部分肝叶头侧缘和大网膜已疝出。大体检查时，在先前应用cSIS补片部位观察到推测为新形成的自体组织。该组织菲薄但保留足够的缝线把持完整性；其表面大体未见活动性血管化；且与周围自体膈肌连续，以至于两者之间无可辨边界。其细胞组成未经组织学验证。疝出的肝叶和大网膜已复位，边缘缺损利用该推测的自体组织直接缝合闭合修复；与初次手术不同，边缘缺损的闭合无显著张力且未使用额外移植材料。腹壁常规闭合，无并发症。术后疼痛使用同一疼痛量表评估；评分再次低于干预阈值，无需补救镇痛。
第二次手术五个月后，胸部X线摄影显示心脏轮廓正常，无心脏增大证据（图7A）。腹部超声检查证实膈肌完整，无再疝证据（图7B）。体格检查时，犬临床状态正常，既往临床症状（喘息、兴奋或运动不耐受）未复发。在5个月的随访期内，未报告进一步的再疝或临床恶化事件。此外，第二次手术后3年进行的电话随访确认该犬状况良好，无任何临床症状。
3. 讨论
本病例报告描述了一只2岁迷你雪纳瑞犬大型先天性PPDH的外科管理，采用一期修复联合cSIS补片加强，随后发生边缘性再疝，并使用cSIS应用部位形成的推测为自体组织的组织成功再修复。虽然单例发现不能推广，但它们说明了cSIS作为犬大型膈肌缺损加强生物材料的潜在用途和局限性，并可能为未来应用提供参考。
本病例的诊断方法遵循系统性流程。胸部X线摄影基于大片状球形心脏轮廓伴膈肌边界模糊的特征性发现，提供了PPDH的初步怀疑[1,2]。超声检查允许无创确认肝脏疝入，彩色多普勒评估提供了疝入肝脏内血流的定性确认，这对于排除肝嵌闭——PPDH一种可能危及生命的并发症——至关重要[7]；然而，由于本病例未记录定量多普勒参数，该评估仍为定性。超声心动图对于评估心脏结构和功能至关重要，因为PPDH在高达57.1%的患病犬中可伴有先天性异常，最常见的是脐疝、腹壁疝和胸骨异常[3,4]。本病例无心脏异常支持手术修复的可行性。CT提供了对膈肌缺损最全面的评估，确认了疝入器官并排除了额外先天性异常，对手术规划非常有价值[9,10]。然而，在再疝时，第二次手术前未重复CT：复发性肝疝已通过X线摄影和超声检查确认，且仅为诊断性CT而单独进行麻醉事件被判定为在麻醉风险相对较高的患者中增加不必要的麻醉风险。因此，复发的确定性解剖特征——包括缺损的边缘位置——通过在修复所需的单次麻醉下术中直接可视化获得（图6C），这可以说构成了比术前横断面成像更直接的解剖证据，尽管未重复CT妨碍了第一次和第二次手术之间缺损解剖的客观术前比较。
当膈肌缺损足够大以允许边缘对合而无过度张力时，一期闭合是PPDH修复的标准技术[2,4]。然而，在本病例中，涉及约70%中心腱的缺损（4.5×5 cm）过大，无法无张力一期闭合。有限的残余中心腱组织导致缝线张力显著和缺损闭合不完全。这一发现与先前报告一致，表明大型中心腱缺损对一期修复构成特殊挑战，因为中心腱对总膈肌面积的贡献相对较小[11,12]。
当一期闭合不可行时，已描述了几种修复大型膈肌缺损的技术。腹侧膈肌推进技术（VADT）涉及切开膈肌腹侧附着并将其向内侧滑动以实现无张力闭合[11,12]。Hennet等人描述了心包瓣修复术后7个月失败后成功进行VADT，结果极佳[11]。Perez-Bello同样报告VADT提供了有效的临床解决，张力最小且并发症率低[12]。心包瓣重建也已使用，但可能带有晚期失败的风险[10,11]。聚丙烯等合成补片材料已被采用，但带有感染、粘连形成和慢性炎症反应的风险[18,19]。
在本病例中，选择cSIS的主要原因是：SIS作为一种无细胞细胞外基质，在促进宿主细胞迁移、新生血管形成和位点特异性组织重塑的同时，提供临时机械支撑[13]；并且SIS会逐渐被宿主组织替代，可能降低长期异物并发症的风险[13]。另一个考虑因素——严格限于理论层面——是cSIS的同种异体来源。猪SIS含有α-Gal表位，该表位已被证实存在于支架全层，并可结合天然存在的抗Gal抗体[15]；由于犬缺乏α-Gal表位，cSIS在理论上植入犬患者时不受这种异种抗原刺激。Yen等证实，去除α-Gal和Neu5Gc表位可显著降低对猪SIS的炎症反应[16]；Lee等报告，两只接受cSIS治疗的犬未出现排斥迹象或特异性免疫反应[14]，并且与聚丙烯网片相比，植入cSIS的大鼠CD8+ T细胞下降更快[17]。然而必须强调，在本病例中这一免疫学原理完全停留在理论层面：未对修复部位进行任何免疫学、组织学或生物力学评估。cSIS在犬中的临床证据基础仍仅限于一份两只犬会阴疝修补术的报告[14]以及本病例。作为关于替代材料的有限背景——鉴于物种、缺损类型和临床环境的差异，并不暗示任何直接可比性——pSIS已成功用于修复一只幼猫的先天性膈疝[20]，并已在犬会阴疝修补术中进行评估[13,21]。尚未开展cSIS与这些或其他生物材料之间的头对头比较研究，也无法从这一单例病例中得出关于cSIS相对疗效、机械强度或组织整合程度的结论。
本病例术后42天发生的再疝值得仔细考虑。重要的是，cSIS补片本身并未失效或破损；再疝发生在自体膈肌与cSIS应用部位之间的边缘界面处。应当注意，移植物被覆盖在初次闭合不完全后残留的腹侧缺损上——而非覆盖包括背侧主要缝合线在内的整个原始缺损区域——并沿该残留缺损的边缘固定。因此，发生裂开的边缘界面对应于残留缺损边缘处移植物与自体膈肌之间的交界处，该位置与第二次手术中发现的边缘缺损一致（图6C）。这种边缘性失败模式与已知的SIS介导组织修复机制一致，即支架在数周内作为宿主细胞浸润和组织沉积的模板[13]。在术后早期，SIS补片与宿主组织之间的界面可能是修复的最薄弱点，因为完全整合和重塑需要时间。Sandoval等在生长中的犬模型中证实，4层SIS补片与5只存活动物中3只出现变薄、多发缺损和内脏疝相关，而8层补片更耐久，成功率为80%[22]。Freitas和Hoddinott（2024）同样强调，在幼年动物中使用SIS补片时，术后数周至数月移植部位观察到的薄半透明膜表明重塑过程仍在进行，应考虑在未来的腹部手术中重新评估膈肌修复情况[20]。这些发现提示，SIS补片的厚度和层数组成可能影响修复强度，并且补片-宿主组织界面的边缘薄弱是公认的潜在并发症。
从生物学角度而言，移植-宿主交界处在植入后的最初数周内本质上较为脆弱。SIS介导的修复依赖于逐渐的宿主细胞浸润、血管长入和组织沉积，在此过程成熟之前，支架与周围组织之间的界面尚未达到其最终强度[13]；与此一致，既往报告已指出SIS补片的厚度和层数组成影响修复强度和耐久性，并且植入后数周至数月重塑仍在进行[20,23]。在本病例中，这种生物学脆弱性可能因修复的构型而加重：移植物与缺损边缘边对边连接，未重叠到自体膈肌上，也未使用加强支撑缝合，因此交界处几乎全部的拉伸负荷仅由主要缝合线承担。相比之下，重叠构型会将力分散到更宽的界面，并提供第二道机械屏障。相反，缝合间距不太可能是主要因素，因为缝线以简单间断模式按相对较近的2-3 mm间距放置。
该交界处得以愈合的环境也可能起到了作用。与相对静止的筋膜或会阴修复部位不同，膈肌在每次呼吸时都经历持续的周期性运动，每天对补片-宿主交界处施加数千次重复的牵张和剪切负荷；这种周期性应力可能延迟或阻碍早期移植物整合，并可能在修复于静息状态下看似稳定时仍促发边缘裂开。此外，在术后最初几周内，除常规术后护理外，犬的活动并未受到限制，因此不能排除跳跃、兴奋或呕吐等引起的腹腔内压短暂骤升作为未成熟界面急性负荷的来源，尽管实际活动模式并未记录。移植床本身也可能不如其他解剖部位有利：与膈肌的肌肉部分相比，中心腱是相对无血管、致密胶原性的结构，这种有限的局部血供可能延迟了宿主细胞迁移和血管长入，进一步延长了边缘交界处脆弱的早期阶段。综上所述，cSIS补片在42天时保持完整且大体上已整合的观察结果不支持支架原发性失败，并将失败定位在边缘界面——最可能是未成熟整合、边对边固定构型、膈肌周期性力学环境以及中心腱血供床有限共同作用的结果——尽管各因素的相对贡献无法从单个病例中确定。
在第二次手术时，在cSIS应用部位观察到大体上与新生宿主组织一致的组织（此处称为“自体组织”）。尽管该组织较薄，但保留了足够的持缝完整性，并与周围原生膈肌在大体上连续、无明显边界；基于这些术中发现，边缘缺损可在无明显张力下直接缝合关闭，从而有效地将具有挑战性的大缺损修复转化为可处理的边缘缺损闭合。这一大体观察与SIS已知的生物学行为一致，即SIS在4-8周内逐渐降解并被机化的宿主结缔组织替代[22,24]。然而，应当指出，在该组织表面未在大体上识别到活跃的血管化；虽然未见可见血管并不能排除毛细血管水平的血管化，但本病例中无法评估修复部位的新生血管化，仍未得到确认。此外，本病例未进行活检；因此，新生组织的确切细胞性质以及修复部位的宿主细胞重塑和新生血管化无法通过组织病理学验证，本报告中关于这些过程的陈述仍属推断。我们承认，在第二次手术时对该新生组织进行组织学取样本可显著提升本报告的科学价值。
回顾性分析，cSIS补片的双层构型可能导致了边缘性失败。如外科方法中所述，选择双层构型是基于术者的术中判断，即两层可为用作部分闭合缺损上方加强修补而非承重桥接的移植物提供足够的厚度和张力。这一经验表明，对于大缺损的临床PPDH修补，移植物的最佳层数仍未确定，因此在计划cSIS加强修补时应明确考虑移植物的厚度。还应注意到，一层或两层构型在既往报道中已有成功应用：双层SIS片被用于重建幼猫的大型慢性膈缺损，临床功能恢复正常且胸壁发育未受限制[25]；双层SIS补片闭合了大鼠全层胃缺损[26]；单层SIS支持了犬大型（5×5 cm）筋膜缺损的再生，12周时组织类似于正常筋膜[27]；且SIS提供的缝线保持强度被认为足以用于软组织缺损的修复[28]。然而，这些观察并不能确立两层对于临床膈修补是最佳的，且尚无研究直接比较该应用中的层数。值得注意的是，在本病例中，移植物以2-3 mm间隔的简单间断模式直接与膈缺损边缘连接，移植物未超出边缘重叠，也未使用加强缝线；鉴于再疝恰好发生在该补片-宿主界面，在边缘界面使用预防性加强（垫衬）缝线，或使移植物超出缺损边缘重叠，可能降低边缘性再疝的风险。必须承认，这些观察和建议是从事本并发症中得出的回顾性反思，而非预先设计的手术方案的组成部分：在第一次手术时，尚无关于SIS补片用于膈修补时重叠或垫衬加强的既定指南或共识，术者判断以紧密间隔的间断缝线进行边缘对边缘固定可为用作加强修补的移植物提供足够强度。从这个意义上说，正是边缘性失败本身产生了这些建议，它们是作为未来应用的教训而提出的，而非被有意省略的技术。综合考虑这些因素，应为cSIS用于膈修补的未来应用提供参考；在提出具体建议之前，有必要对替代生物材料、层数构型和固定技术进行适当设计的比较研究。
本报告的局限性包括数据收集的回顾性性质、缺乏对修复部位的组织病理学评估，以及院内影像学随访仅限于第二次手术后5个月；然而，第二次手术后3年对主人的电话访谈确认该犬仍未出现临床症状，尽管当时未重复影像学检查。此外，所有超声检查均由同一检查者完成，多普勒评估仅限于定性彩色多普勒确认血流；未获取或记录超声造影及定量血流参数（如收缩期峰值流速和阻力指数），因此无法评估观察者间变异性。第二次手术前也未重复CT检查，以避免对被认为麻醉风险相对较高的患者因诊断性影像而再次经历麻醉事件；因此，复发性疝环的位置和大小未在术前通过横断面影像进行表征，再次疝出的边缘机制解剖学证据依赖于第二次手术中获得的术中所见（图6C），这无法对第一次和第二次手术之间缺损解剖进行客观的术前比较。此外，移植物固定的技术因素可能促成了导致再次疝出的边缘薄弱：尽管手术时认为两层已足够，但移植物放置未超出膈肌边缘进行重叠，也未使用加强缝合，因此不能排除更厚的移植物、移植物超出缺损边缘的重叠或支撑缝合能更好地抵抗边缘裂开的可能性；相应地，讨论中提出的关于移植物重叠和支撑缝合的建议代表基于该结局的回顾性反思，而非预先设计的手术方案的组成部分。由于未获取活检，本报告中关于组织重塑和自体组织形成的描述基于术中大体和超声所见，而非组织学确认；相应地，推测的自体组织薄但可缝合的特性、其与原生膈肌的大体连续性以及无可见活动性血管化——毛细血管水平血管化的可能性仍未评估——仅构成大体评估。我们承认，第二次手术时对该新形成组织进行组织学采样将大幅提升本报告的机制价值。此外，本报告未提供比较数据：未测量修复的机械强度、持缝张力和补片整合程度，也未与pSIS、犬阔筋膜同种异体移植物或合成补片进行比较。相应地，本报告中讨论的cSIS相对于pSIS的免疫学优势应被视为未经检验的理论假设，而非本研究的发现，关于cSIS与其他生物材料相对性能的陈述有待适当设计的比较研究。
4. 结论
在本病例中，cSIS补片加强似乎是对于无法仅用缝线完全闭合的大型PPDH缺损行一期修复的可行辅助手段。在第二次手术中，术中大体所见提示cSIS应用部位有新组织形成，这使得边缘性再次疝出的二次修复得以成功；然而，由于未获取活检，该组织的细胞性质以及潜在的宿主细胞重塑和新生血管化无法经组织病理学确认，本报告中的此类描述仍基于大体和影像学所见。此外，由于这些观察来自单一病例且无比较或生物力学数据，应被视为初步结果，cSIS相对于其他生物材料的理论免疫学优势在此背景下仍未经验证，且无法就cSIS与其他生物材料的相对性能得出结论。cSIS补片与原生膈肌之间的边缘界面可能是术后早期修复的最薄弱点，建议密切术后监测，包括系列胸部X线摄影和超声检查，以早期发现边缘性再次疝出。临床膈肌修复中SIS移植物的最佳层数仍有待确定，边缘重叠技术可能改善未来应用中的结局。需要更大病例数、组织病理学和生物力学评估以及更长随访期的进一步研究，以确立cSIS用于犬膈疝修复的安全性、有效性和最佳应用技术。
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1. Introduction
Peritoneopericardial diaphragmatic hernia (PPDH) is a congenital malformation characterized by persistent communication between the peritoneal cavity and the pericardial sac, resulting from failure of the septum transversum to fuse properly with the pleuroperitoneal membranes during embryonic development [1]. PPDH is the most common congenital pericardial anomaly in dogs and cats [2,3]. While the true prevalence is low—estimated at 0.015% of hospitalized dogs—the condition may be underdiagnosed because some affected animals remain asymptomatic throughout their lives [4,5].
Clinical signs of PPDH are variable and depend on the type and amount of herniated abdominal organs, the degree of cardiopulmonary compression, and the presence of incarceration. The most common presenting signs include respiratory signs (dyspnea, tachypnea, panting) and gastrointestinal signs (vomiting, anorexia, diarrhea), with respiratory signs being more prevalent in cats and gastrointestinal signs in dogs [2,3]. Attenuation or muffling of heart sounds is a characteristic physical examination finding resulting from displacement of the heart by herniated abdominal organs [6,7].
Diagnosis of PPDH is primarily achieved through diagnostic imaging. Thoracic radiography typically reveals a markedly enlarged cardiac silhouette, dorsal displacement of the trachea, and obscuration of the diaphragmatic border [1,2]. Abdominal ultrasonography and echocardiography allow direct visualization of herniated organs and assessment of cardiac structure and function [7,8]. Computed tomography (CT) provides detailed characterization of the diaphragmatic defect and aids in surgical planning [9,10].
Surgical repair is the treatment of choice for animals with clinical signs attributable to PPDH [2,4]. A multi-institutional study of 128 dogs reported that 97% of surgically treated dogs were discharged from the hospital; long-term follow-up was available for 87 dogs at a median of 1062 days, with no hernia recurrence reported in any surgically treated dog [5]. Primary closure by direct apposition of the diaphragmatic margins is the preferred technique; however, large defects that constitute a substantial portion of the diaphragm may preclude tension-free closure. In such cases, alternative techniques including pericardial flap reconstruction, ventral diaphragmatic advancement, muscle flap transposition, or biomaterial patch implantation may be required [11,12].
Small intestinal submucosa (SIS) is an acellular extracellular matrix biomaterial that has been reported to promote site-specific host tissue remodeling and neovascularization while providing temporary mechanical support during tissue regeneration. Both porcine SIS (pSIS) and canine SIS (cSIS) have been used for hernia repair in dogs; however, pSIS has been more extensively studied and is commercially available, whereas cSIS remains non-commercialized [13,14]. An important theoretical immunological distinction exists between these graft types: pSIS contains the Galα(1,3)Gal (α-Gal) epitope distributed transmurally throughout the scaffold, which can potentially elicit a xenogeneic immune response in non-porcine recipients [15], whereas cSIS—as an allogeneic graft in canine patients—is inherently devoid of this antigenic burden [16]. Despite this theoretical consideration, clinical evidence for cSIS remains limited to a single report of perineal herniorrhaphy in two dogs without signs of rejection or recurrence over 12 months [14]. To the authors’ knowledge, the use of cSIS for reinforcement of large PPDH defects in dogs has not been previously reported. This case report describes the surgical management of a large congenital PPDH using primary repair combined with cSIS patch reinforcement, the occurrence of marginal reherniation, and subsequent successful re-repair utilizing presumed self-tissue formed at the cSIS application site.
2. Case Presentation
A 2-year-old intact female White Miniature Schnauzer weighing 6.23 kg was referred to the Konkuk University Veterinary Medical Teaching Hospital for evaluation of a 1-month history of panting, excitement, and exercise intolerance during walks. The owner reported that the clinical signs had been progressively worsening and were triggered or exacerbated by physical activity. There was no history of trauma, and the dog had been otherwise healthy with no previous surgical or medical conditions. The dog was not receiving any medications at the time of presentation.
On physical examination, the dog’s body temperature was 39.1 °C, heart rate was 132 bpm, and respiratory rate was 48 breaths/min. The most notable finding on auscultation was muffled heart sounds, particularly on the right hemithorax. No other abnormalities were detected on physical examination.
Hematological and serum biochemical analyses were within reference ranges (Table 1). No abnormalities suggestive of hepatic dysfunction, metabolic disease, or other systemic illness were identified.
Thoracic radiography (right lateral and ventrodorsal views) revealed a large, globoid cardiac silhouette with rightward displacement of the cardiac apex (Figure 1). The diaphragmatic border was obscured. These findings were consistent with cardiomegaly with a morphology suspicious for PPDH [1,3].
Abdominal ultrasonography, performed by a single examiner with the dog positioned in dorsal recumbency using a 7.5 MHz transducer, confirmed herniation of a liver lobe into the pericardial sac (Figure 2A). Color Doppler evaluation confirmed the presence of blood flow within the herniated liver lobe (Figure 2B), ruling out vascular compromise or incarceration at the qualitative level; contrast-enhanced ultrasonography, and quantitative Doppler parameters (such as peak systolic velocity and resistive index) were not used or recorded.
Echocardiography revealed a structure with echogenicity consistent with hepatic tissue adjacent to the right heart within the pericardial sac. No evidence of incarceration or adhesion of the herniated liver to the pericardium or cardiac surface was identified. Importantly, the cardiac structure and function were normal, with no congenital cardiac anomalies or functional deficits detected.
To further characterize the extent of the diaphragmatic defect and assess for additional congenital abnormalities, contrast-enhanced thoracic and abdominal CT was performed under general anesthesia. Multiplanar reconstruction (MPR) images in transverse, sagittal, and dorsal planes were generated for surgical planning. CT confirmed the presence of a liver lobe within the pericardial sac, with leftward displacement of the heart by the mass effect of the herniated organs (Figure 3). The craniocaudal extent of the hernia and the diaphragmatic defect location were assessed on sagittal and dorsal MPR images. No other congenital abnormalities, including sternal anomalies or additional abdominal wall defects, were identified.
The dog was premedicated with buprenorphine (10 μg/kg, IM; Renolphan, Hanlim Pharm, Yongin city, Republic of Korea) and midazolam (0.3 mg/kg, IV; Vascam, HaNa Pharm, Seoul city, Republic of Korea). General anesthesia was induced with propofol (6 mg/kg, IV; Anepol, HaNa Pharm, Seoul city, Republic of Korea) and maintained with 2% isoflurane (Forane, ChoongWae Pharma, Gwacheon city, Republic of Korea) in 100% oxygen. Epidural anesthesia was administered using a mixture of bupivacaine (0.5 mg/kg; Bupivacaine 0.5%, HaNa Pharm, Seoul city, Republic of Korea) and buprenorphine (10 μg/kg; Renolphan, Hanlim Pharm, Yongin city, Republic of Korea). Surgical repair was performed via a midline celiotomy extending from the xiphoid to the pubis. Upon abdominal exploration, the left medial liver lobe and the quadrate lobe were confirmed to be herniated through the diaphragmatic defect into the pericardial sac (Figure 4). The herniated liver lobes were carefully reduced back into the abdominal cavity. No adhesions between the herniated liver and the pericardium or cardiac structures were present.
Following reduction of the herniated liver lobes, the diaphragmatic defect was identified at the central tendon of the diaphragm. On CT, the overall dimensions of the diaphragm were 11 × 11 cm on the thoracic surface. The defect measured approximately 4.5 × 5 cm, accounting for approximately 21% of the total diaphragmatic area, and constituting approximately 70% of the central tendon area (Figure 4).
Primary repair of the defect was first attempted by suturing from the dorsal to the ventral margin of the defect. Only two simple interrupted sutures could be placed at the dorsal margin of the defect; further apposition of the ventral aspect was not possible because the large size of the defect and the limited amount of residual central tendon tissue placed excessive tension on the sutures, and the defect therefore could not be completely closed with primary repair alone. Consequently, a residual defect remained at the ventral aspect of the original defect; it was triangular in shape and measured more than 3 × 3 cm.
Therefore, to reinforce the incompletely closed defect, a 5 × 5 cm canine small intestinal submucosa (cSIS) patch was folded in half to create a double-layer (2-ply) graft and sutured over the residual defect (Figure 4). The 2-ply configuration was selected based on the surgeon’s intraoperative judgment that two layers would provide sufficient thickness and strength both to span the residual defect and to reinforce the partially completed primary repair. The cSIS was prepared according to the method validated by Lee et al. [17]. Briefly, jejunal segments were retrieved through the institutional canine tissue donation program. Tissues were harvested, with written informed owner consent, from client-owned adult dogs that were free of systemic disease other than underlying neurological deficits and euthanized for medical reasons unrelated to this study. All specimens were collected within 2 h post-euthanasia and thoroughly rinsed with sterile normal saline.
The mucosa, muscularis, and serosa were removed by mechanical abrasion, and the remaining submucosa was thoroughly rinsed in sterile normal saline and 80% ethanol to remove cell degradation products. The cSIS was stored at 4 °C in sterile normal saline containing antibiotics (lincomycin HCl, vancomycin HCl, and cefotaxime) for 7 days prior to use [17]. The cSIS patch was secured to the surrounding diaphragmatic margins with 4-0 monofilament polyglyconate sutures (Maxon; Covidien, Fridley, MN, USA) in a simple interrupted pattern at 2–3 mm intervals, with each suture bite incorporating the full thickness of the diaphragm; the graft was joined directly to the edge of the residual defect, without overlapping the surrounding native diaphragm, and no additional reinforcing (buttress) sutures were placed. The subcutaneous tissue was closed with 4-0 Maxon sutures (Covidien, USA), and the skin was closed with 3-0 monofilament polyamide sutures (Dafilon; B. Braun, Melsungen, Germany). The surgery lasted 83 min, with a total anesthesia time of 95 min; intraoperative blood loss was estimated at less than 10 mL, and neither thoracic nor abdominal drainage was placed.
The dog recovered from anesthesia uneventfully. Buprenorphine (10 µg/kg, IM) was administered as an analgesic every 8 h for 2 days, and treatment with cephalexin (22 mg/kg) was continued twice per day for 14 days. Postoperative pain was monitored during hospitalization using the short form of the Glasgow composite measure pain scale (GCMPS-SF); pain scores remained low and consistently below the recommended analgesic intervention threshold (6/24) at all assessments, and no rescue analgesia was required. Postoperative hospitalization lasted 3 days, during which the dog was monitored for respiratory compromise, pneumothorax, and other postoperative complications. No significant postoperative complications were observed. Skin sutures were removed 11 days after surgery.
Follow-up thoracic radiography at the time of suture removal demonstrated a normal cardiac silhouette size, with resolution of the previously observed globoid cardiomegaly (Figure 5A). Abdominal ultrasonography confirmed that the cSIS patch was well maintained at the defect site, with no evidence of reherniation (Figure 5B).
At 42 days postoperatively, physical examination was unremarkable; however, thoracic radiography revealed an increase in cardiac silhouette size to a long axis measurement similar to the preoperative value (90.8 mm) (Figure 6A). Abdominal ultrasonography demonstrated herniation of a structure consistent with a liver lobe into the pericardial sac (Figure 6B), with no evidence of adhesion between the herniated tissue and the heart on ultrasonographic evaluation. Based on these imaging findings, reherniation was diagnosed. Because the diagnosis had already been established by radiography and ultrasonography, and because repeating CT would have required a separate anesthetic event in a patient considered to be at relatively high anesthetic risk, CT was not repeated; instead, the anatomy of the recurrence was assessed by direct visualization during the single anesthetic episode required for surgical repair. The dog subsequently underwent a second surgery via midline celiotomy. The anesthesia protocol was identical to that of the first surgery; the second surgery lasted 49 min, with a total anesthesia time of 58 min, intraoperative blood loss was estimated at less than 5 mL, and no drainage device was placed. Upon exploration, a defect was identified at the margin between the native diaphragm and the cSIS application site; the cSIS patch itself was intact and appeared to have been incorporated into the surrounding diaphragmatic tissue, indicating that the reherniation occurred at the patch–host tissue interface rather than through patch breakdown (Figure 6C). Through this marginal defect, a portion of the cranial margin of a liver lobe and omentum had herniated. On gross inspection, tissue presumed to be newly formed self-tissue was observed at the site where the cSIS patch had been previously applied. This tissue was thin but retained sufficient suture-holding integrity; no active vascularization was grossly identified on its surface; and it appeared continuous with the surrounding native diaphragm to the extent that no discernible boundary separated the two. Its cellular composition was not verified histologically. The herniated liver lobe and omentum were reduced, and the marginal defect was repaired by direct suture closure utilizing this presumed self-tissue; unlike at the initial surgery, closure of the marginal defect was achieved without significant tension and without the use of additional graft material. The abdominal wall was closed routinely without complications. Postoperative pain was assessed using the same pain scale; scores again remained below the intervention threshold, and no rescue analgesia was required.
Five months after the second surgery, thoracic radiography revealed a normal cardiac silhouette with no evidence of cardiomegaly (Figure 7A). Abdominal ultrasonography confirmed an intact diaphragm with no evidence of reherniation (Figure 7B). On physical examination, the dog was clinically normal with no recurrence of the previous clinical signs (panting, excitement, or exercise intolerance). No further episodes of reherniation or clinical deterioration were reported during the 5-month follow-up period. In addition, a telephone follow-up conducted 3 years after the second surgery confirmed that the dog was doing well without any clinical signs.
3. Discussion
This case report describes the surgical management of a large congenital PPDH in a 2-year-old Miniature Schnauzer using primary repair combined with cSIS patch reinforcement, subsequent marginal reherniation, and successful re-repair using tissue presumed to be self-tissue formed at the cSIS application site. While the findings of a single case cannot be generalized, they illustrate both the potential utility and the limitations of cSIS as a reinforcement biomaterial for large diaphragmatic defects in dogs and may inform future applications.
The diagnostic approach in this case followed a systematic algorithm. Thoracic radiography provided the initial suspicion of PPDH based on the characteristic finding of a large globoid cardiac silhouette with obscured diaphragmatic border [1,2]. Ultrasonography allowed non-invasive confirmation of liver herniation, and color Doppler evaluation provided qualitative confirmation of blood flow within the herniated liver, which was crucial for ruling out hepatic incarceration—a potentially life-threatening complication of PPDH [7]; however, as quantitative Doppler parameters were not recorded in this case, this assessment remained qualitative. Echocardiography was essential for evaluating cardiac structure and function, as PPDH can be associated with concurrent congenital abnormalities in up to 57.1% of affected dogs, most commonly umbilical hernias, abdominal wall hernias, and sternal anomalies [3,4]. The absence of cardiac abnormalities in this case supported the feasibility of surgical repair. CT provided the most comprehensive assessment of the diaphragmatic defect, confirming the herniated organs and ruling out additional congenital abnormalities, and was invaluable for surgical planning [9,10]. At the time of reherniation, however, CT was not repeated before the second surgery: recurrent hepatic herniation had already been confirmed by radiography and ultrasonography, and a separate anesthetic event solely for diagnostic CT was judged to add unnecessary anesthetic risk in a patient considered to be at relatively high anesthetic risk. Consequently, definitive anatomical characterization of the recurrence—including the marginal location of the defect—was obtained by direct intraoperative visualization (Figure 6C) under the single anesthetic episode required for the repair, which arguably constitutes more direct anatomical evidence than preoperative cross-sectional imaging could have provided, although the absence of repeat CT precluded objective preoperative comparison of the defect anatomy between the first and second surgeries.
Primary closure is the standard technique for PPDH repair when the diaphragmatic defect is of sufficient size to allow apposition of the margins without excessive tension [2,4]. In the present case, however, the defect involving approximately 70% of the central tendon (4.5 × 5 cm) was too large for tension-free primary closure. The limited residual central tendon tissue resulted in significant tension on the sutures and incomplete defect closure. This finding is consistent with previous reports indicating that large central tendon defects pose a particular challenge for primary repair due to the relatively small contribution of the central tendon to the total diaphragmatic area [11,12].
Several techniques have been described for repairing large diaphragmatic defects when primary closure is not feasible. The ventral diaphragmatic advancement technique (VADT) involves incising the ventral attachments of the diaphragm and sliding it medially to achieve tension-free closure [11,12]. Hennet et al. described successful VADT after failure of a pericardial flap repair 7 months postoperatively, with an excellent outcome [11]. Perez-Bello similarly reported that VADT provided effective clinical resolution with minimal tension and a low complication rate [12]. Pericardial flap reconstruction has also been used but may carry a risk of late failure [10,11]. Synthetic mesh materials such as polypropylene have been employed but carry risks of infection, adhesion formation, and chronic inflammatory reactions [18,19].
In this case, cSIS was chosen primarily because SIS, as an acellular extracellular matrix, provides temporary mechanical support while promoting host cell migration, neovascularization, and site-specific tissue remodeling [13], and because SIS is gradually replaced by host tissue, potentially reducing the risk of long-term foreign body complications [13]. A further consideration—strictly at the theoretical level—was the allogeneic origin of cSIS. Porcine SIS contains the α-Gal epitope, which has been demonstrated throughout the full thickness of the scaffold and can bind naturally occurring anti-Gal antibodies [15]; because canines lack the α-Gal epitope, cSIS is theoretically free from this xenogeneic antigenic stimulus when implanted in canine patients. Yen et al. confirmed that removal of the α-Gal and Neu5Gc epitopes significantly reduces the inflammatory response to porcine SIS [16], and Lee et al. reported no signs of rejection or specific immune responses in two dogs treated with cSIS [14], as well as a more rapid CD8+ T cell decline in cSIS-implanted rats compared to polypropylene mesh [17]. It must be emphasized, however, that this immunological rationale remained entirely theoretical in the present case: no immunological, histological, or biomechanical evaluation of the repair site was performed. The clinical evidence base for cSIS in dogs remains limited to a single report of perineal herniorrhaphy in two dogs [14] and the present case. As limited context on alternative materials—without implying any direct comparability, given the differences in species, defect type, and clinical setting—pSIS has been used successfully to repair a congenital diaphragmatic hernia in a kitten [20] and has been evaluated for perineal herniorrhaphy in dogs [13,21]. No head-to-head comparative study between cSIS and these or other biomaterials has been performed, and no conclusion regarding the relative efficacy, mechanical strength, or degree of tissue integration of cSIS can be drawn from this single case.
The reherniation that occurred 42 days postoperatively in the present case warrants careful consideration. Importantly, the cSIS patch itself did not fail or break down; rather, the reherniation occurred at the marginal interface between the native diaphragm and the cSIS application site. It should be noted that the graft had been applied over the residual ventral defect that remained after incomplete primary closure—rather than over the entire original defect area including the dorsal primary suture line—and was anchored along the margin of this residual defect. Accordingly, the marginal interface at which dehiscence occurred corresponded to the junction between the graft and the native diaphragm along the edge of the residual defect, a location consistent with the marginal defect identified at the second surgery (Figure 6C). This pattern of marginal failure is consistent with the known mechanism of SIS-mediated tissue repair, in which the scaffold serves as a template for host cell infiltration and tissue deposition over a period of several weeks [13]. In the early postoperative period, the interface between the SIS patch and the host tissue may represent the weakest point of the repair, as complete integration and remodeling require time. Sandoval et al. demonstrated in a growing canine model that 4-ply SIS patches were associated with thinning, multiple defects, and visceral herniation in 3 of 5 surviving animals, whereas 8-ply patches were more durable with an 80% success rate [22]. Freitas and Hoddinott (2024) similarly emphasized that when SIS patches are used in juvenile animals, the thin semitransparent membrane observed at the graft site weeks to months postoperatively indicates that the remodeling process is still ongoing, and reassessment of the diaphragmatic repair should be considered during future abdominal surgeries [20]. These findings suggest that the thickness and layer composition of the SIS patch may influence repair strength and that marginal weakness at the patch–host tissue interface is a recognized potential complication.
Biologically, the graft–host junction is intrinsically vulnerable during the first weeks after implantation. SIS-mediated repair relies on gradual host cell infiltration, vascular ingrowth, and tissue deposition, and until this process matures, the interface between the scaffold and the surrounding tissue has not yet attained its eventual strength [13]; consistent with this, previous reports have noted that the thickness and layer composition of SIS patches influence repair strength and durability, and that remodeling is still ongoing weeks to months after implantation [20,23]. In the present case, this biological vulnerability was likely compounded by the configuration of the repair: the graft was joined edge-to-edge to the defect margin, without overlap onto the native diaphragm and without reinforcing buttress sutures, so that essentially the entire tensile load at the junction was borne by the primary suture line alone. An overlapping configuration, in contrast, would have distributed forces across a wider interface and provided a second mechanical barrier. Suture spacing, by contrast, is unlikely to have been the dominant factor, as the sutures were placed at a relatively close 2–3 mm interval in a simple interrupted pattern.
The environment in which this junction had to heal may also have contributed. Unlike relatively static fascial or perineal repair sites, the diaphragm undergoes continuous cyclical excursion with every breath, imposing repetitive tensile and shear loading on the patch–host junction many thousands of times per day; such cyclic stress could delay or oppose early graft integration and may precipitate marginal dehiscence even when the repair appears stable at rest. In addition, the dog’s activity was not restricted beyond routine postoperative care during the first weeks, so transient surges in intra-abdominal pressure—jumping, excitement, or vomiting—cannot be excluded as sources of acute loading across the immature interface, although the actual activity pattern was not documented. The graft bed itself may also have been less favorable than other anatomical sites: the central tendon is a relatively avascular, densely collagenous structure compared with the muscular portions of the diaphragm, and this limited local blood supply may have delayed host cell migration and vascular ingrowth, further prolonging the vulnerable early period of the marginal junction. Taken together, the observation that the cSIS patch remained intact and grossly incorporated at 42 days argues against primary scaffold failure and localizes the failure to the marginal interface—most likely the combined result of immature integration, the edge-to-edge fixation configuration, the cyclic mechanical environment of the diaphragm, and the modest vascular bed of the central tendon—although the relative contribution of each cannot be determined from a single case.
At the second surgery, tissue grossly consistent with newly formed host tissue (referred to here as “self-tissue”) was observed at the cSIS application site. Although this tissue was thin, it retained sufficient suture-holding integrity and was grossly continuous with the surrounding native diaphragm without a discernible boundary; on the basis of these intraoperative findings, the marginal defect could be closed by direct suturing without significant tension, effectively converting the challenging large defect repair into a manageable marginal defect closure. This gross observation is in line with the known biological behavior of SIS, which is gradually degraded and replaced by organized host connective tissue over a period of 4–8 weeks [22,24]. It should be noted, however, that active vascularization was not grossly identified on the surface of this tissue; while the absence of visible vessels does not exclude capillary-level vascularization, neovascularization at the repair site could not be assessed in this case and remains unconfirmed. Moreover, no biopsy was performed in this case; therefore, the precise cellular nature of the newly formed tissue, as well as host–cell remodeling and neovascularization at the repair site, could not be histopathologically verified, and statements regarding these processes in this report remain inferential. We acknowledge that histological sampling of this newly formed tissue at the second surgery would have substantially enhanced the mechanistic value of this report.
In retrospect, the 2-ply configuration of the cSIS patch may have contributed to the marginal failure. As described in the surgical methods, the 2-ply configuration was selected based on the surgeon’s intraoperative judgment that two layers would provide sufficient thickness and tension for a graft applied as reinforcement over a partially closed defect, rather than as a load-bearing bridge. This experience illustrates that the optimal number of graft layers for clinical PPDH repair remains undetermined for large defects, and that graft thickness should therefore be explicitly considered when planning cSIS reinforcement. It should also be noted that configurations of one or two layers have been used successfully in prior reports: double-layer SIS sheets were used to reconstruct a large chronic diaphragmatic defect in a kitten, with restoration of normal clinical function and no restriction of chest wall development [25]; a double-layer SIS patch closed full-thickness gastric defects in rats [26]; single-layer SIS supported regeneration of large (5 × 5 cm) fascial defects in dogs, with tissue resembling normal fascia at 12 weeks [27]; and SIS provides suture retention strength that has been judged adequate for the repair of soft tissue defects [28]. These observations, however, do not establish that two layers are optimal for clinical diaphragmatic repair, and no study has directly compared layer counts for this application. Notably, in the present case the graft was joined directly to the diaphragmatic defect edge in a simple interrupted pattern at 2–3 mm intervals without graft overlap beyond the margin and without reinforcing sutures; given that the reherniation occurred precisely at this patch–host interface, the use of prophylactic reinforcing (buttress) sutures at the marginal interface, or overlap of the graft beyond the defect margins, might have reduced the risk of marginal reherniation. It must be acknowledged that these observations and suggestions are retrospective reflections drawn from the present complication, not elements of a pre-designed surgical plan: at the time of the first operation, no established guideline or consensus existed regarding overlap or buttress reinforcement for SIS patches applied to diaphragmatic repair, and the surgeon judged that edge-to-edge fixation with closely spaced interrupted sutures would provide adequate strength for a graft serving as reinforcement. In this sense, the marginal failure itself is what generated these recommendations, and they are offered as lessons for future applications rather than as techniques that were knowingly omitted. These considerations, taken together, should inform future applications of cSIS for diaphragmatic repair; appropriately designed comparative studies of alternative biomaterials, layer configurations, and fixation techniques are warranted before specific recommendations can be made.
Limitations of this report include the retrospective nature of data collection, the lack of histopathological evaluation of the repair site, and the fact that in-hospital imaging follow-up was limited to 5 months after the second surgery; however, a telephone interview with the owner 3 years after the second surgery confirmed that the dog remained free of clinical signs, although imaging was not repeated at that time point. In addition, all ultrasonographic examinations were performed by a single examiner, and Doppler assessment was limited to qualitative color Doppler confirmation of blood flow; contrast-enhanced ultrasonography, and quantitative flow parameters (such as peak systolic velocity and resistive index) were not obtained or recorded, so inter-observer variability could not be assessed. CT was also not repeated prior to the second surgery, in order to avoid a separate anesthetic event for diagnostic imaging in a patient considered to be at relatively high anesthetic risk; consequently, the position and size of the recurrent hernia ring were not characterized preoperatively by cross-sectional imaging, and the anatomical evidence for the marginal mechanism of reherniation rests on the intraoperative findings obtained at the second surgery (Figure 6C), which did not allow objective preoperative comparison of the defect anatomy between the first and second surgeries. In addition, technical aspects of the graft fixation may have contributed to the marginal weakness that led to reherniation: although two layers were judged sufficient at the time of surgery, the graft was placed without overlap beyond the diaphragmatic margin and without reinforcing sutures, so the possibility that a thicker graft, graft overlap beyond the defect margin, or buttress sutures would have better withstood marginal dehiscence cannot be excluded; accordingly, the suggestions regarding graft overlap and buttress sutures raised in the Discussion represent retrospective reflections informed by this outcome, not elements of a pre-designed surgical protocol. Because no biopsy was obtained, descriptions of tissue remodeling and self-tissue formation in this report are based on gross intraoperative and ultrasonographic findings rather than histological confirmation; accordingly, the thin but sutureable quality of the presumed self-tissue, its gross continuity with the native diaphragm, and the absence of visible active vascularization—with the possibility of capillary-level vascularization remaining unevaluated—constitute gross assessments only. We acknowledge that histological sampling of this newly formed tissue at the second surgery would have substantially enhanced the mechanistic value of this report. Furthermore, this report provides no comparative data: the mechanical strength, suture-holding tension, and degree of patch integration of the repair were not measured, and no comparison with pSIS, canine fascia lata allograft, or synthetic mesh was performed. Accordingly, the immunological advantage of cSIS over pSIS discussed in this report should be regarded as an untested theoretical hypothesis rather than a finding of this study, and statements about the relative performance of cSIS versus other biomaterials await appropriately designed comparative studies.
4. Conclusions
In this case, cSIS patch reinforcement appeared to serve as a feasible adjunct to primary repair for a large PPDH defect that could not be completely closed with sutures alone. At the second surgery, gross intraoperative findings suggested new tissue formation at the cSIS application site, which enabled successful secondary repair of a marginal reherniation; however, because no biopsy was obtained, the cellular nature of this tissue and the underlying host–cell remodeling and neovascularization could not be histopathologically confirmed, and such descriptions in this report remain based on gross and imaging findings. Moreover, as these observations are drawn from a single case without comparative or biomechanical data, they should be regarded as preliminary, the theoretical immunological advantage of cSIS over alternative biomaterials remains untested in this setting, and no conclusions can be drawn regarding the relative performance of cSIS compared with other biomaterials. The marginal interface between the cSIS patch and the native diaphragm may represent the weakest point of the repair in the early postoperative period, and close postoperative monitoring, including serial thoracic radiography and ultrasonography, is recommended to detect marginal reherniation early. The optimal number of SIS graft layers for clinical diaphragmatic repair remains to be determined, and marginal overlap techniques may improve outcomes in future applications. Further studies with larger case numbers, histopathological and biomechanical evaluation, and longer follow-up periods are needed to establish the safety, efficacy, and optimal application technique of cSIS for diaphragmatic hernia repair in dogs.