Background: Patients with locally advanced rectal cancer (LARC) treated with (chemo)-radiotherapy before abdominoperineal resection (APR) are at high risk of developing pelvic organ/space surgical site infection (O/S-SSI). This increases morbidity and prolongs length of stay. Vague symptoms delay diagnosis. In microdialysis, thin catheters are placed in tissue enabling monitoring of metabolism. We hypothesize that local metabolic changes related to O/S-SSI might be detected by microdialysis.

Methods: In a prospective observational study, 38 patients who underwent open APR for LARC were analysed. At the end of surgery microdialysis catheters were placed in remnant tissue of the pelvic floor. Postoperatively, metabolic parameters including lactate, pyruvate, glucose and glycerol were measured, and the lactate-to-pyruvate (L/P) ratio was calculated. Out of 38 patients, 12 (32%) developed O/S-SSI.

Results: O/S-SSI was diagnosed median 9 (range 6-17) days after surgery. On the day of surgery, mean lactate in the O/S-SSI group was 6.0 mmol/L, whereas it was 3.6 mmol/L in the no-O/S-SSI group. ROC analysis (AUC = 0.73), with cut-point lactate 5.7, detected O/S-SSI with 92% sensitivity and 65% specificity. Overall mean lactate was 1.9 mmol/L higher in the O/S-SSI group than in the no-O/S-SSI group (P = 0.002). Overall mean L/P ratio was 34 units higher in the O/S-SSI group (P = 0.001).

Conclusions: In patients developing pelvic O/S-SSI, tissue lactate and L/P ratio measured by microdialysis were significantly higher and evident already from the day of surgery, 9 days prior to diagnosis, with high negative predictive value and moderate positive predictive value. Local monitoring using microdialysis may aid detection of O/S-SSI.

Keywords: Abdominoperineal resection; Chemoradiotherapy; Lactate; Microdialysis; Rectal cancer; Surgical site infection.

© 2025. The Author(s).

背景： 局部晚期直肠癌（LARC）患者在接受腹会阴切除术（APR）前进行放疗或化疗，容易发生盆腔器官/空间手术部位感染（O/S-SSI）。这增加了患者的发病率并延长了住院时间。模糊的症状会导致诊断延迟。微透析技术通过将细导管放置在组织中来监测代谢情况。我们假设通过微透析可以检测到与O/S-SSI相关的局部代谢变化。

方法： 本研究是一项前瞻性观察性研究，分析了38名接受开放APR手术治疗LARC的患者的数据。在手术结束时，在盆底残留组织中放置微透析导管。术后测量乳酸、丙酮酸、葡萄糖和甘油等代谢参数，并计算乳酸与丙酮酸（L/P）比率。在这38名患者中，有12名（占32%）发生了O/S-SSI。

结果： O/S-SSI的诊断时间中位数为手术后9天（范围：6-17天）。在手术当天，发生O/S-SSI患者的乳酸平均值为6.0 mmol/L，而未发生O/S-SSI患者的乳酸平均值为3.6 mmol/L。ROC分析显示（AUC = 0.73），以5.7 mmol/L作为切点时，可以检测到92%的敏感性和65%的特异性。总体而言，与未发生O/S-SSI组相比，发生O/S-SSI组患者的乳酸平均值高出了1.9 mmol/L（P = 0.002）。同时，L/P比率在发生O/S-SSI组中也高出34单位（P = 0.001）。

结论： 对于发生盆腔O/S-SSI的患者来说，通过微透析测量组织乳酸和L/P比率从手术当天开始就显著升高，并且在诊断前9天就能发现这一变化。这种方法具有很高的阴性预测值和中等的阳性预测值。局部监测使用微透析技术可能有助于早期检测O/S-SSI。

关键词： 腹会阴切除术；放化疗；乳酸；微透析；直肠癌；手术部位感染。