兽研引言
猫和犬的输尿管梗阻在小动物临床中日益受到重视，可导致肾积水、肾盂肾炎、进行性肾功能丧失，最终发展为慢性肾病。常见的潜在病因包括尿石症、输尿管狭窄、炎症性疾病和肿瘤。严重梗阻可导致氮质血症和梗阻性急性肾损伤。因此，早期诊断和及时干预对于解除梗阻、保护肾功能和改善临床结局至关重要。
过去几十年来，输尿管梗阻的管理已从以保守或临时措施为主（可能伴随较高的并发症发生率）转向微创介入技术。其中，输尿管支架置入和皮下输尿管旁路系统（SIDUS）已成为猫和犬输尿管梗阻的重要治疗选择。SIDUS具有较高的临床成功率和改善或稳定肾功能的效果，尤其在难治性或多发性输尿管梗阻患者中（Ahmed, 2021; Berent & Weisse, 2011; Deprey, 2021）。
尽管具有临床获益，但在尿路内植入生物材料可能促进细菌黏附、定植和生物膜形成。然而，近期证据表明，尿培养阳性结果并不一定提示活动性感染，因为亚临床细菌定植较为常见。因此，临床发现应结合实验室和微生物学结果进行解读（Deprey, 2021; Epstein, 2021; Weese et al., 2019）。
在此背景下，本研究旨在评估接受SIDUS植入的猫和犬在长达90天随访期内的临床、实验室和微生物学结局。具体而言，本研究旨在描述肾功能的变化特征并评估植入后尿路感染的发生情况。
材料与方法
伦理方面
本研究经Universidade Positivo机构动物护理与使用委员会（CEUA/UP）批准，方案编号为32/2024。
研究设计与患者选择
本研究为回顾性队列研究，基于对2021年1月至2024年6月期间在巴西库里蒂巴一家私立兽医医院接受治疗的猫和犬的医疗记录进行回顾。接受SIDUS植入并由肾脏病科随访90天的动物符合纳入条件。
纳入要求术前及术后30、60和90天具备尿液分析和尿培养及抗菌药物敏感性试验结果。上述时间点还需具备全血细胞计数、血清肌酐、尿素、磷、静脉血气分析及电解质测定和腹部超声检查结果。排除标准包括：接受急诊手术且术前无尿培养、在医院外进行实验室或影像学检查、未由同一肾脏病团队随访，或未遵守既定装置维护方案的动物。
数据收集
数据从电子医疗记录中回顾性提取，包括人口学特征（物种、年龄、性别、绝育状态和体重）、实验室检测结果和影像学发现。记录术前、术后即刻及后续随访评估的尿培养及相应抗菌药物敏感性试验结果。回顾腹部超声报告，记录与输尿管梗阻相关的发现，包括肾盂扩张、输尿管壁增厚、输尿管结石及外压性压迫证据。
手术技术与术后管理
术前禁食8-12小时，并根据临床需要给予静脉输液以维持体液平衡和纠正液体及电解质异常。使用丙泊酚和芬太尼诱导麻醉，以异氟烷在氧气中维持麻醉。术中监测包括脉搏血氧饱和度、二氧化碳描记、心电图和有创血压测量。
手术过程包括腹中线开腹、在透视引导下放置输尿管导管、肾脏固定、膀胱造口以放置膀胱导管，并使用“X”形连接器连接各组件。皮下端口固定于腹筋膜，在透视引导下输注无菌生理盐水评估系统通畅性。随后按解剖层次关闭腹腔。
术后对患者进行密切监测，并在有临床指征时给予多模式镇痛和抗菌治疗，抗菌药物选择依据尿培养结果。分别在术后24小时、7天和30天使用肝素化生理盐水冲洗SIDUS，此后每3个月冲洗一次。随访评估包括实验室检测、腹部超声、尿液分析和尿培养。
统计分析
数据录入电子表格并使用GraphPad Prism进行分析。连续变量的正态性采用Shapiro-Wilk检验评估。连续变量以中位数和四分位距（IQR）汇总。两个相关时间点之间的比较采用Wilcoxon符号秩检验。双侧p < 0.05被认为具有统计学意义。
结果
本研究共纳入17只接受SIDUS植入的动物，包括10只犬（58.8%）和7只猫（41.2%）。研究群体包括8只雌性（47.1%）和9只雄性（52.9%）。大多数动物年龄小于10岁（15/17；88.2%），10只动物（58.8%）已绝育。
术前血清肌酐浓度明显升高，中位数为10.0 mg/dL。SIDUS植入后24小时，中位浓度显著下降（p < 0.001）至6.0 mg/dL。第30天观察到进一步降低，中位浓度达到2.0 mg/dL。第60天和第90天中位肌酐浓度均稳定在1.8 mg/dL，表明输尿管减压后肾功能持续改善（图1）。
[图：在90天随访期内血清肌酐浓度的变化。]
尿素和磷浓度呈现相似的模式，SIDUS植入后显著降低。白细胞计数在术后出现轻度波动，但未检测到统计学显著差异（p > 0.05）。随访期间未观察到核左移。因此，观察到的白细胞变化被解释为与手术操作和设备植入相关的炎症反应。
整个随访期间尿培养主要为阴性。阳性培养偶发出现，且未伴随报告的临床症状或实验室指标恶化。
讨论
本研究表明，SIDUS植入后肾脏生化指标迅速改善，血清肌酐浓度在术后24小时内显著下降，并在60天和90天随访期间持续保持显著较低水平。尿素和磷浓度也观察到类似趋势，支持输尿管减压对肾功能生化标志物的有益作用。这些发现与既往报道一致（Ahmed, 2021; Butty, 2023; Deprey, 2021）。
术前发现的代谢异常与该群体梗阻性急性肾损伤的严重程度一致。低钾血症是主要的钾异常，发生于76%的动物，而高钾血症见于24%。低钾血症占优势可能反映多种因素，包括既往液体治疗以及梗阻后阶段相关的改变，如近期研究所描述（Hecht, 2024）。
微生物学发现为SIDUS植入后尿路并发症提供了额外见解。随访期间大多数尿培养保持阴性，提示SIDUS植入在结合适当的设备维护和监测时，不一定与临床相关尿路感染发生率增加相关。这些发现强调了根据ISCAID指南结合临床发现和实验室异常解读尿培养结果的重要性（Epstein, 2021; Weese et al., 2019）。
本研究的局限性包括样本量小和90天随访时间有限，无法就设备矿化和机械故障等迟发性并发症得出结论。需要涉及更大群体和更长随访期的多中心研究来解决这些局限性并更好地描述长期结局。
结论
SIDUS是治疗猫和犬输尿管梗阻的有效方法，在植入后前90天内使肾功能生化标志物出现统计学显著且持续的改善。这些发现支持在结合适当随访和设备维护的情况下临床使用SIDUS。
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Introduction
Ureteral obstruction in cats and dogs is an increasingly recognized challenge in small animal practice and may lead to hydronephrosis, pyelonephritis, progressive loss of renal function, and, ultimately, chronic kidney disease. Common underlying causes include urolithiasis, ureteral strictures, inflammatory conditions, and neoplasia. Severe obstruction can result in azotemia and obstructive acute kidney injury. Therefore, early diagnosis and timely intervention are critical for relieving obstruction, preserving renal function, and improving clinical outcomes.
Over the past several decades, the management of ureteral obstruction has evolved from predominantly conservative or temporary measures, which may be associated with substantial complication rates, toward minimally invasive interventional techniques. Among these, ureteral stenting and the subcutaneous ureteral bypass system (SIDUS) have become important treatment options for cats and dogs with ureteral obstruction. SIDUS has been associated with high clinical success rates and improvement or stabilization of renal function, particularly in patients with refractory or multiple ureteral obstructions (Ahmed, 2021; Berent & Weisse, 2011; Deprey, 2021).
Despite its clinical benefits, implantation of biomaterials within the urinary tract may facilitate bacterial adhesion, colonization, and biofilm formation. However, recent evidence suggests that positive urine culture results do not necessarily indicate active infection, as subclinical bacterial colonization is common. Therefore, clinical findings should be interpreted in conjunction with laboratory and microbiological results (Deprey, 2021; Epstein, 2021; Weese et al., 2019).
In this context, the present study aimed to evaluate the clinical, laboratory, and microbiological outcomes of cats and dogs undergoing SIDUS implantation during a follow-up period of up to 90 days. Specifically, the study sought to characterize changes in renal function and assess the occurrence of urinary tract infection following implantation.
Materials and methods
Ethical aspects
This study was approved by the Institutional Animal Care and Use Committee of Universidade Positivo (CEUA/UP), under protocol number 32/2024.
Study design and patient selection
A retrospective cohort study was conducted based on a review of the medical records of cats and dogs treated at a private veterinary hospital in Curitiba, Brazil, between January 2021 and June 2024. Animals that underwent SIDUS implantation and were monitored by the nephrology service for 90 days were eligible for inclusion.
Inclusion required the availability of urinalysis and urine culture with antimicrobial susceptibility testing during the preoperative period and at 30, 60, and 90 days postoperatively. Complete blood count, serum creatinine, urea, phosphorus, venous blood gas analysis with electrolyte measurements, and abdominal ultrasonography were also required at these time points. Animals that underwent emergency surgery without a preoperative urine culture, had laboratory or imaging examinations performed outside the hospital, were not followed by the same nephrology team, or did not adhere to the established device-maintenance protocol were excluded.
Data collection
Data were retrospectively extracted from electronic medical records and included demographic characteristics (species, age, sex, reproductive status, and body weight), laboratory test results, and imaging findings. Urine culture and corresponding antimicrobial susceptibility testing results were recorded for the preoperative period, immediate postoperative period, and subsequent follow-up evaluations. Abdominal ultrasonography reports were reviewed for findings associated with ureteral obstruction, including renal pelvic dilation, ureteral wall thickening, ureteroliths, and evidence of extrinsic compression.
Surgical technique and postoperative management
Before surgery, patients were fasted for 8-12 h and received intravenous fluid therapy for maintenance and correction of fluid and electrolyte abnormalities as clinically indicated. Anesthesia was induced with propofol and fentanyl and maintained with isoflurane in oxygen. Intraoperative monitoring included pulse oximetry, capnography, electrocardiography, and invasive blood pressure measurement.
The surgical procedure consisted of a ventral midline celiotomy, placement of ureteral catheters under fluoroscopic guidance, renal fixation, cystostomy for placement of the bladder catheter, and connection of the components using an “X” connector. The subcutaneous port was secured to the abdominal fascia, and system patency was assessed by infusion of sterile saline under fluoroscopic guidance. The abdomen was subsequently closed in anatomical layers.
Postoperatively, patients underwent intensive monitoring and received multimodal analgesia and antimicrobial therapy when clinically indicated, with antimicrobial selection guided by urine culture results. SIDUS was flushed with heparinized saline at 24 h, 7 days, and 30 days after surgery and subsequently at 3-month intervals. Follow-up evaluations included laboratory testing, abdominal ultrasonography, urinalysis, and urine culture.
Statistical analysis
Data were entered into electronic spreadsheets and analyzed using GraphPad Prism. The normality of continuous variables was assessed using the Shapiro-Wilk test. Continuous variables were summarized as medians and interquartile ranges (IQRs). Comparisons between two related time points were performed using the Wilcoxon signed-rank test. A two-sided p < 0.05 was considered statistically significant.
Results
Seventeen animals that underwent SIDUS implantation were included in the study, comprising 10 dogs (58.8%) and 7 cats (41.2%). The study population included eight females (47.1%) and nine males (52.9%). Most animals were younger than 10 years (15/17; 88.2%), and 10 animals (58.8%) were neutered.
Serum creatinine concentrations were markedly increased preoperatively, with a median of 10.0 mg/dL. At 24 h after SIDUS implantation, the median concentration decreased significantly (p < 0.001) to 6.0 mg/dL. A further reduction was observed at 30 days, when the median concentration reached 2.0 mg/dL. Median creatinine concentrations remained stable at 1.8 mg/dL at both 60 and 90 days, indicating sustained improvement in renal function following ureteral decompression (Figure 1).
[图：Evolution of serum creatinine concentrations over the 90-day follow-up period.]
Urea and phosphorus concentrations showed a similar pattern, with significant reductions after SIDUS implantation. Leukocyte counts exhibited mild postoperative variation, but no statistically significant differences were detected (p > 0.05). No left shift was observed during follow-up. Therefore, the observed leukocyte changes were interpreted as an inflammatory response associated with surgical manipulation and implantation of the device.
Urine cultures were predominantly negative throughout the follow-up period. Positive cultures occurred sporadically and were not accompanied by reported clinical signs or deterioration of laboratory parameters.
Discussion
The present study demonstrated rapid improvement in renal biochemical parameters following SIDUS implantation, with serum creatinine concentrations decreasing significantly within 24 h after surgery and remaining substantially lower throughout the 60- and 90-day follow-up periods. Similar trends were observed for urea and phosphorus concentrations, supporting the beneficial effect of ureteral decompression on biochemical markers of renal function. These findings are consistent with previous reports (Ahmed, 2021; Butty, 2023; Deprey, 2021).
The metabolic abnormalities identified before surgery were consistent with the severity of obstructive acute kidney injury in this population. Hypokalemia was the predominant potassium abnormality, occurring in 76% of animals, whereas hyperkalemia was identified in 24%. The predominance of hypokalemia may reflect several factors, including prior fluid administration and alterations associated with the post-obstructive phase, as described in recent studies (Hecht, 2024).
The microbiological findings provide additional insight into urinary tract complications following SIDUS implantation. Most urine cultures remained negative during follow-up, suggesting that SIDUS implantation, when combined with appropriate device maintenance and monitoring, was not necessarily associated with an increased incidence of clinically relevant urinary tract infection. These findings highlight the importance of interpreting urine culture results in conjunction with clinical findings and laboratory abnormalities, in accordance with ISCAID guidelines (Epstein, 2021; Weese et al., 2019).
The study limitations include the small sample size and limited 90-day follow-up, which preclude conclusions regarding late-onset complications such as device mineralization and mechanical failure. Multicenter studies involving larger populations and longer follow-up periods are warranted to address these limitations and better characterize long-term outcomes.
Conclusions
SIDUS was an effective treatment for ureteral obstruction in cats and dogs, resulting in statistically significant and sustained improvements in biochemical markers of renal function during the first 90 days after implantation. These findings support the clinical use of SIDUS when combined with appropriate follow-up and device maintenance.