Postoperative gastrointestinal dysfunction (POGD), often referred to as postoperative ileus (POI) after colorectal surgery, is characterized by symptoms such as nausea, vomiting, abdominal distension, and delayed bowel movements. The incidence of this issue varies among medical institutions, impacting patient nutrition, prolonging hospital stays, and increasing healthcare costs.

The complex pathogenesis of POGD involves a brief neurogenic phase (within 3 hours) and a more prolonged inflammatory phase (beginning at 3-4 hours and lasting for days). The inflammatory phase is crucial and is recognized as initiated by mast cells and damage-associated molecular patterns that activate macrophages in the intestinal muscle layer. Subsequently, it triggers a series of cascading inflammation reactions through the release of inflammatory factors and recruitment of inflammatory cells, which contributes to the development and exacerbation of POGD. Studies have demonstrated changes in inflammatory cells and factors in the abdominal fluid following abdominal surgery, emphasizing the clinical significance of analyzing drainage fluid to predict postoperative gastrointestinal function.

This study analyzes inflammatory markers in drainage fluid following laparoscopic colorectal cancer surgery. The aim is to enhance the accuracy of predicting gastrointestinal recovery outcomes and contribute to the evolving field of Enhanced Recovery After Surgery (ERAS).

Postoperative gastrointestinal dysfunction (POGD), often referred to as postoperative ileus (POI), is a common gastrointestinal issue that frequently occurs after colorectal surgery. It is characterized by symptoms such as nausea and vomiting, abdominal distension, and delayed defecation and evacuation. The incidence of POI is not clearly defined due to the varying definitions across healthcare institutions, but it is estimated to be approximately 10-30% and is one of the most common complications after colorectal surgery. The occurrence of POI increases the nutritional risk of patients (e.g., malnutrition, myasthenia gravis, malignant morbidity), prolongs the length of hospital stay, increases hospital costs, and significantly adds to the health economic burden.

In 2018, the American Society for Enhanced Recovery and Perioperative Quality Initiative Joint Consensus Statement considered abandoning the traditional definition of POI and proposed a scoring system based on intake, sensation of nausea, vomiting, physical examination, and duration of symptoms (I-FEED). They also introduced a definition of postoperative gastrointestinal dysfunction (POGD) based on scores classifying postoperative gastrointestinal function as normal (0-2), postoperative gastrointestinal intolerance (POGI) (3-5), and postoperative gastrointestinal dysfunction (POGD) (>6).

The complex pathogenesis of POGD involves a brief neurogenic phase (within 3 hours) and a more prolonged inflammatory phase (beginning at 3-4 hours and lasting for days). The inflammatory phase is crucial and is recognized as initiated by mast cells and damage-associated molecular patterns that activate macrophages in the intestinal muscle layer. Subsequently, it triggers a series of cascading inflammation reactions through the release of inflammatory factors and recruitment of inflammatory cells, which contributes to the development and exacerbation of POGD.

Levels of inflammatory cells and factors in the peritoneal fluid are changed following abdominal surgery in both rodents and humans. Many previous studies have confirmed that the use of drainage fluids also reduces the incidence of elevated inflammatory markers, such as CRP, in the presence of unrelated inflammatory stimuli, such as concurrent infections and systemic diseases. For instance, in other diseases like meningitis, blood IL-6 is less specific than IL-6 in the drainage fluid. In addition, abdominal drainage fluid is more effective and efficient than routinely collected blood for detecting anastomotic leakage (AL) following colorectal cancer surgery. However, fewer studies have been conducted to predict the recovery of postoperative gastrointestinal function by analyzing drainage fluid. We believe that analyzing postoperative gastrointestinal drainage fluid is of greater clinical importance in predicting postoperative gastrointestinal function.

In our study, we collected abdominal drainage fluid near the anastomosis on the first and third day after laparoscopic colorectal cancer surgery for biochemical and cytological tests. These tests included lactate dehydrogenase (LDH), adenosine deaminase (ADA) and albumin. We also performed conventional cytological tests for neutrophils, lymphocytes, monocytes, etc. In addition, we calculated inflammatory indices such as neutrophil-lymphocyte ratio (NLR), lymphocyte-monocyte ratio (LMR) and prognostic nutrition index (PNI). We also collected peripheral blood for the same cytological indices and evaluated the outcome of the patients' gastrointestinal function recovery using the I-FEED score. In addition, we analyzed the correlation between the above indices and PODG, and combined the inflammation indices of peritoneal drainage and serum to predict the outcome of gastrointestinal function recovery after laparoscopic colorectal cancer surgery aiming to improve the accuracy and effectiveness of prediction and accelerate patient recovery.

Inclusion Criteria:

• Preoperative diagnosis of colorectal cancer through colonoscopy biopsy.
• Patients aged 18-80 years.
• Underwent laparoscopic radical resection for colorectal cancer with confirmed postoperative pathology.
• No prior radiotherapy, chemotherapy, or immunotherapy before surgery.
• Voluntary participation in the study and signing of a written informed consent form.

Exclusion Criteria:

• Pregnant or lactating women.
• Severe liver dysfunction (Child-Pugh class B or above); severe renal dysfunction (serum creatinine level greater than 177).
• Patients with severe heart failure, chronic obstructive pulmonary disease, and other underlying diseases.
• Patients with pre-existing severe infections (developing sepsis or not improving after antibiotic treatment) before surgery.
• Patients with postoperative fistulas or those requiring a two-stage anastomosis.
• Intraoperative and postoperative intraperitoneal chemotherapy.
• Blood disorders (leukemia, lymphoma, aplastic anemia, etc.).
• Patient or family member withdraws midway.
• Those with serious post-operative infections (e.g., incisional, lung, and urinary tract infections)
• Intraoperative conversion to open laparotomy.

Patients aged 18-80 with preoperative colorectal cancer diagnosis through colonoscopy biopsy underwent laparoscopic radical resection, excluding prior radiotherapy, chemotherapy, or immunotherapy, and voluntarily participated by signing informed consent.