Background and Objectives: Anastomotic leakage (AL) is a major complication following sphincter-preserving surgeries for left-sided colorectal cancer. In this study, we aimed to evaluate the association between circular stapler diameter and the risk of AL. As a secondary objective, we investigated whether preoperative serum protein levels were associated with leakage development. Materials and Methods: We conducted a retrospective case–control study including 99 patients who underwent elective colorectal surgery with stapled anastomosis for left-sided colorectal cancer between January 2020 and May 2024. A total of 99 patients were included (60.6% male), with a mean age of 66.1 ± 10.7 years. The patients were categorized into small (≤29 mm) and large (≥30 mm) stapler groups. Demographic, clinical, and laboratory variables were collected. Anastomotic leakage was defined as an International Study Group of Rectal Cancer (ISREC) Grade B or C leak requiring intervention. Univariate analyses and multivariate logistic regression analyses were performed, and results were reported as odds ratios (ORs) with 95% confidence intervals (CIs). A STROBE-compliant flow diagram was prepared. Results: Anastomotic leakage occurred in 10 patients (10.1%), and leakage rates were not significantly different between stapler-size groups (≤29 mm: 10.9% vs. ≥30 mm: 7.5%, p = 0.365). In multivariate analysis, stapler size was not independently associated with leakage (OR 1.68, 95% CI 0.40–6.97, p = 0.480). Lower preoperative serum protein levels were identified as the only independent predictor of leakage (OR 0.28, 95% CI 0.10–0.74, p = 0.011). Postoperative hospital stay was significantly longer for patients with leakage (median 17 vs. 7 days, p < 0.001). Conclusions: We found no significant associations between circular stapler diameter and anastomotic leakage in left-sided colorectal cancer surgery. Conversely, low serum protein levels were independently associated with increased leakage risk, highlighting the importance of preoperative nutritional assessment. Given the retrospective design, small number of leakage cases, and unmeasured confounders, these findings should be interpreted with caution. Further multicenter, prospective studies should be conducted to clarify the influence of stapler size and patient-related factors on anastomotic outcomes.

Objective: The primary objective was to assess the discriminatory performance of admission serum calprotectin for 30-day all-cause mortality. The secondary exploratory objective was to evaluate a composite index calculated by multiplying the Sequential Organ Failure Assessment score, calprotectin, and lactate.Materials and Methods: This single-center prospective study included 76 adults admitted to intensive care between January 2024 and March 2025. Serum calprotectin was measured by enzyme-linked immunosorbent assay within 24 hours of admission. Areas under the receiver operating characteristic curves and 95% confidence intervals were used to quantify discrimination. The index was recomputed from its components for every patient. Five pairwise curve comparisons underwent Holm correction. Uncertainty and threshold stability were examined using 5,000 stratified bootstrap resamples.Results: Eight patients (10.5%) died. Median calprotectin was 16.06 µg/mL in non-survivors versus 8.20 µg/mL in survivors (p=0.005). The area under the curve was 0.804 (95% confidence interval: 0.665–0.944) for calprotectin, 0.903 for lactate, and 0.941 (95% confidence interval: 0.860–1.000) for the corrected index. No superiority of the index over any individual parameter was demonstrated after multiplicity correction. Mean out-of-bag sensitivity and specificity of the index were 73.7% and 87.2%, respectively.Conclusion: Serum calprotectin was associated with 30-day mortality in this small cohort. The composite index’s high apparent discrimination does not establish clinical superiority or a validated clinical threshold. Given the small number of events and the unstable thresholds, these findings are hypothesis-generating; independent validation is required.