Impact of visceral obesity on postoperative complications and oncological outcomes in elderly patients with colorectal cancer

Abstract

BACKGROUND

Elderly patients with colorectal cancer (CRC) can judge the risk of postoperative complications and oncological outcomes due to visceral obesity, which can provide data reference for the early prediction of prognosis.

AIM

To explore the effect of visceral obesity on postoperative complications and oncological outcomes in elderly patients with CRC.

METHODS

A total of 150 elderly patients who underwent radical surgery for CRC at Inner Mongolia Medical University and Inner Mongolia Autonomous Region People’s Hospital from January 2021 to June 2024 were retrospectively analyzed. Patients were divided into the abdominal [visceral fat area (VFA) ≥ 100.00 cm², n = 80] and non-abdominal (VFA < 100.00 cm², n = 70) obesity groups according to the VFA measured by preoperative computed tomography. The two groups showed no significant differences in age, sex, tumor location, tumor-node-metastasis stage, and underlying disease (P > 0.05). All patients underwent standardized laparoscopic assisted surgery and received unified perioperative management. Complications, nutritional status, changes in biochemical indicators, and tumor recurrence and metastasis were evaluated postoperatively.

RESULTS

The overall incidence of postoperative complications was significantly higher in the abdominal obesity group than in the non-abdominal obesity group (P < 0.05). The pulmonary infection on postoperative day (POD) 3 (P = 0.038), anastomotic leakage on POD 7 (P = 0.042), and moderate-to-severe complications (Clavien-Dindo class III, P = 0.03) were significantly different. With respect to biochemical indicators, the white blood cell count, neutrophil percentage, and C-reactive protein level in the abdominal obesity group continuously increased after surgery (P < 0.05); the albumin level on POD 1 was even lower (P = 0.024). Regarding tumor markers, carcinoembryonic antigen (P = 0.039) and carbohydrate antigen 19-9 (P = 0.048) levels were significantly higher in the abdominal obesity group at 3 months after surgery, and local recurrence rates were higher than those in the non-abdominal obesity group at 30 days and 3 months after surgery (P < 0.05). Abdominal obesity was an independent risk factor for postoperative complications (odds ratio: 3.843, P = 0.001), overall survival [hazard ratio (HR): 1.937, P = 0.011], and disease-free survival (HR: 1.769, P = 0.018).

CONCLUSION

Visceral obesity significantly increases the risk of postoperative complications in elderly patients with CRC and may adversely affect short-term tumor prognosis. Preoperative risk identification and interventions for abdominal obesity should be strengthened to improve perioperative safety and postoperative rehabilitation quality.

Key Words: Visceral obesity; Elderly colorectal cancer; Postoperative complications; Oncological outcomes; Disease-free survival; Inflammatory biomarkers

Core Tip: This study highlights the critical impact of visceral obesity on postoperative complications and short-term oncological outcomes in elderly patients undergoing colorectal cancer surgery. Patients with elevated visceral fat area showed higher risks of infection, anastomotic leakage, inflammatory response, and tumor recurrence. Visceral obesity was also identified as an independent predictor of overall and disease-free survival. These findings underscore the importance of preoperative risk stratification and targeted perioperative interventions for improving outcomes in this high-risk population.

INTRODUCTION

Colorectal cancer (CRC) is the third most common malignant tumor globally and the second leading cause of cancer-related mortality, particularly in the elderly population[1]. In China, aging demographics and changing lifestyles have contributed to the rising incidence of CRC among older adults.

With advancements in medical technology and the expansion of screening coverage, an increasing number of elderly patients can now undergo radical surgeries. However, the high incidence of postoperative complications and the heterogeneity of the long-term prognosis of tumors remain the main constraints on the effectiveness of clinical treatment[2]. At the same time, as a metabolic abnormal phenotype, visceral obesity has attracted extensive attention in recent years for its role in tumor prognosis[3].

Compared to the traditional body mass index (BMI), visceral obesity can reflect the deposition state of visceral fat more accurately. As an active endocrine organ, the latter can secrete a variety of pro-inflammatory factors, including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), adipokines, leptin, adiponectin and chemokines, and is involved in the proliferation of tumor cells, angiogenesis, immune escape and microenvironment remodeling[4,5]. Visceral obesity in elderly CRC patients with CRC may exacerbate perioperative risks through multiple mechanisms. Abundant visceral fat makes abdominal surgery more difficult, prolongs the operation time, and increases the risk of hemorrhage and complications related to anastomosis[6]. By contrast, adipose tissue-mediated chronic low-grade inflammation inhibits the immune system, delays postoperative recovery, and promotes micrometastasis, leading to an increased risk of tumor recurrence and metastasis[7]. Multiple cohort studies have shown that the incidence of postoperative complications is significantly increased and the 5-year overall survival (OS) and disease-free survival (DFS) rates are significantly decreased in CRC patients with a high visceral fat area (VFA), suggesting that visceral obesity is an important predictor of tumor outcomes[8]. Although some studies have explored the relationship between obesity and the prognosis of CRC, they have mostly focused on the overall population and lack special analysis of elderly patients. However, this population exhibited significant differences in metabolic function, body reserve capacity, and surgical tolerance. Therefore, focusing on the clinical impact of visceral obesity in elderly patients with CRC not only supplements the current research gap but is also expected to provide a basis for perioperative risk assessment, individualized nutrition intervention, and rehabilitation path optimization.

MATERIALS AND METHODS

General data

A total of 150 elderly patients with CRC at the Inner Mongolia Medical University and Inner Mongolia Autonomous Region People’s Hospital (a tertiary care center) from January 2021 to June 2024 were retrospectively analyzed in this study. All patients were confirmed to have colorectal adenocarcinomas based on postoperative pathology. Patients were divided into the abdominal (VFA ≥ 100.00 cm², n = 80) and non-abdominal (VFA < 100.00 cm², n = 70) obesity groups according to the intra-abdominal VFA measured by preoperative computed tomography (CT). The inclusion criteria were as follows: (1) Aged ≥ 65 years; (2) Had primary colorectal adenocarcinoma, as confirmed by postoperative pathology; (3) Underwent standard radical surgery (D3 dissection or total mesorectal excision); (4) Completed abdominal computed tomography (CT) examination within 3 months preoperatively; (5) Had measurable VFA; and (6) Had complete records of postoperative complications, with a follow-up duration of ≥ 12 months. The exclusion criteria were as follows: (1) Patients who received chemoradiotherapy before surgery (n = 12); (2) Patients with severe underlying diseases, such as cardiac dysfunction with New York Heart Association grade ≥ III, Child-Pugh C cirrhosis, and end-stage renal disease (n = 15); (3) Patients with other malignant tumors or history of cancer recurrence (n = 8); and (4) Patients who switched to palliative surgery intraoperatively or died within 30 days after surgery (n = 5). Differences in sex, age, tumor location, tumor-node-metastasis stage, and major underlying diseases between the two groups were not statistically significant (P > 0.05), indicating that they were comparable (Table 1).

Table 1 Comparison of general data between the two groups, n (%).

Factor	Abdominal obesity group (n = 80)	Non-abdominal obesity group (n = 70)	χ2/t	P value
Age (years)	72.63 ± 5.32	71.91 ± 5.58	0.788	0.432
Male	52 (65.00)	45 (64.29)	0.005	0.943
Tumor site
Carcinoma of colon	45 (56.25)	38 (54.29)	0.057	0.811
Rectal cancer	35 (43.75)	32 (45.71)
TNM stage I-II	34 (42.50)	29 (41.43)	0.018	0.893
TNM stage III	46 (57.50)	41 (58.57)
Combined hypertension	38 (47.50)	32 (45.71)	0.038	0.845
Combined diabetes	22 (27.50)	18 (25.71)	0.05	0.824

P < 0.05 indicated significant difference. TNM: Tumor-node-metastasis.

This study was approved by the Ethics Committee of the Inner Mongolia Autonomous Region People’s Hospital. Retrospective data usage complied with the institutional guidelines, and the requirement for informed consent was waived owing to the anonymized nature of the data analysis.

Methods

Therapeutic methods: Both groups of patients underwent standardized radical surgery for CRC performed by the same medical team to ensure operational consistency. Surgery included total mesorectal excision and D3 lymph node dissection, both of which were performed laparoscopically. The surgical equipment used was the Einstein Vision 3D laparoscopic system manufactured by Aesculap GmbH, Germany, which has high-definition stereoscopic vision to help accurately identify tumor boundaries and lymph node structures during surgery, thereby improving the precision and safety of the operation. Intraoperatively, the GEN11 ultrasonic high-frequency surgical integrated system (Johnson & Johnson) was used for vascular closure and tissue cutting, thus effectively reducing bleeding and thermal injury. All patients underwent intestinal tract preparation before surgery. Sterile conditions were maintained intraoperatively. An abdominal drainage tube was placed after surgery. The timing of extraction was determined based on the drainage volume and nature within 3-5 days after surgery. After surgery, all patients received the same perioperative management, including the following: (1) Prophylactic use of antibiotics: Intravenous cefminox sodium (Hailing, 2.0 g) was injected 30 minutes before surgery, and the drug was continued for 2 times/day, for a total of 3 days after surgery; (2) Nutrition support treatment: Parenteral nutrition support was started on the first day after operation, and medium-/Long-chain fat emulsion injection (C8-24) (Kelun, 300 mL) and compound amino acid injection (l8AA-II) (Fresenius-kabi-sspc, 500 mL) per day were used for 5 days; (3) Anticoagulant prevention: Hemocoagulase agkistrodon (Konruns, 2U) was injected subcutaneously once daily at 12 hours after surgery to prevent deep vein thrombosis. The treatment lasted for 5-7 days; and (4) Analgesia and rehabilitation management: Flurbiprofen axetil injection (Tide, 50 mg/time, q12h) was routinely used after surgery, together with early ambulation and respiratory function exercises.

Detection methods: (1) VFA: GE Revolution CT was used to scan the horizontal axis of the navel (layer thickness, 1.25 mm). The fat area in the peritoneum was delineated using the Mimics Innovation Suite software (Version 21.0, Materialize). The HU value was set in the range of -190 to -30, and the VFA (cm²) was automatically calculated. Independent measurements by two radiologists took the mean; if the difference was > 10%, it was reviewed by a physician with a senior title. Visceral obesity was defined as VFA ≥ 100 cm², based on the Japanese Obesity Society criteria for metabolic risk stratification; (2) Monitoring of postoperative complications: Assessment of postoperative complications followed the Clavien-Dindo classification criteria. All patients were independently evaluated by two attending physicians on postoperative days (PODs) 1, 2, 3, and 6 and before discharge, and the occurrence of pulmonary infection, incision infection, urinary system infection, intestinal obstruction, anastomotic leakage, postoperative hemorrhage, and deep vein thrombosis were recorded; (3) Detection of biochemical indicators: 5.00 mL of venous blood was collected at 1 day before surgery and PODs 1, 3, and 7. Blood was analyzed using a BS-800M automatic biochemical analyzer (Shenzhen Meirui Biological Medical Electronics Co., Ltd.), which mainly monitors the white blood cell (WBC) count, neutrophil percentage (NEUT%), C-reactive protein (CRP), albumin (ALB), total protein (TP), and other indicators. The detection limit of CRP was 1.00 mg/L using nephelometry, and the linear range of ALB detection was 10.00-60.00 g/L; (4) Detection of tumor markers: Carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) were detected at 1 day before surgery, on POD 7, and during reexamination at 3 months after surgery. Venous blood (5.00 mL) was collected and analyzed using a Roche Cobas e411 automatic electrochemical luminescence analyzer. The reagents were obtained from the original kits. The CEA and CA19-9 reference ranges were 0-5.00 ng/mL and 0-37.00 U/mL, respectively. The frequency of detection was once every three months after surgery and lasted for one year; (5) Imaging detection: Abdominal contrast-enhanced CT and pelvic magnetic resonance imaging (MRI) examinations were performed within 1 month after surgery and every 3 months during follow-up to monitor recurrence and metastasis after surgery. CT examination was performed using a GE Revolution CT with a layer thickness of 1.25 mm, voltage of 120 kV, and automatic current regulation. MRI was performed using a Philips Ingenia 1.5T mr system, which consisted of sequences of T1WI, T2WI, and DWI, and the contrast agent injected at the time of the contrast enhancement scan was iohexol (GE Healthcare, 300 mgI/mL, body weight calculated at 1.50 mL/kg, and a single maximum of 150.00 mL) (Figure 1); and (6) Postoperative nutrition and recovery assessment: The patient’s intake, body weight change, abdominal distension, and flatus and defecation were assessed every day after operation, and the nutritional status was assessed using the Patient-Generated Subject Global Assessment (PG-SGA) scale once a Wuxi Weighing instrument RGZ - 120 - RT body weight scale with an error controlled within ± 0.10 kg.

Figure 1 Imaging test of typical case. A: Shows the image detection of the operation area of the abdominal obesity group on the 30^th postoperative day (POD). The imaging performance of the abdominal operation area of the patient with abdominal obesity on POD 30 showed that the tissue structure in the operation area was clear and there was no abnormal density shadow or effusion. The wound healed well; B: Shows the imaging findings of local recurrence in the abdominal obesity group three months after surgery. Reexamination of the patient with abdominal obesity at 3 months after surgery showed an irregular soft tissue density shadow (arrow) at the edge of the original operation area, and the boundary was fuzzy, indicating local recurrence; C: Shows the image detection of the operation area of the non-abdominal obesity group on the 30^th POD. The imaging performance of the patient with non-abdominal obesity in the operation area on POD 30 showed that the anatomical level of the operation area was clear, and no obvious exudation, hematoma, or recurrence was found; D: Shows the imaging detection of local recurrence at 3 months after surgery in the non-abdominal obesity group. The imaging detection figure of the non-abdominal obesity patient three months after operation shows that nodular abnormal signal shadow with a diameter of about 1.2 cm (arrow) appears in the adjacent area of the operation area, and the enhanced scan is uneven and intensive, suggesting local recurrence.

All test results were recorded by a specially assigned person and crosschecked by two people. The data were uniformly entered into an electronic database. All operations were performed in strict compliance with the Clinical Laboratory Regulations (CLSI Standards) and hospital operating procedures to ensure objectivity and traceability of the data.

Outcome indicators: (1) Monitoring of postoperative complications: Complications were assessed according to the Clavien-Dindo classification, which was divided into grades I and V. The observation time points were 1, 2, 3, and 6 days after surgery, and before hospital discharge, which were cross-checked and evaluated by two senior attending physicians. Monitoring contents included pulmonary infection (body temperature > 38.0 °C and WBC count > 10.00 × 10⁹/L according to chest radiography and hemogram changes), incision infection (swelling, exudation and needing intervention), urinary system infection (routine urine WBC count > 10/HP), intestinal obstruction (no exhaust and defecation accompanied by weakening of borborygmus > 72 hours after surgery), anastomotic leakage (CT or angiography showed leakage), postoperative hemorrhage (Hb drop ≥ 20 g/L), and deep vein thrombosis (confirmed by color Dopplar ultrasound); (2) Detection of biochemical indicators: 5.00 mL venous blood was collected at 1 day preoperatively and on the 1^st, 3^rd and 7^th PODs. WBC count, NEUT%, CRP, ALB, and TP levels were measured using a Mindray BS-800M automatic biochemical analyzer. The normal value for CRP was < 8.00 mg/L, and the reference ranges for ALB, WBC count, and NEUT% were 35.00-50.00 g/L, (4.00-10.00) × 10⁹/L, and 40%-75%, respectively; (3) Tumor marker detection: The detection time was 1 day before surgery, POD 7, and 3 months after surgery. The parameters included CEA and CA19-9. A Roche Cobas e411 automatic electrochemical luminescence instrument was used for detection. The normal CEA values were 0-5.00 ng/mL and CA19-9 were 0-37.00 U/mL, and the results were used to assess the risk of early postoperative recurrence or metastasis; (4) Follow-up imaging evaluation: Abdominal contrast-enhanced CT and pelvic MRI were performed on the 30^th day and every three months after surgery. GE Revolution CT (layer thickness 1.25 mm, voltage 120 kV) was used for contrast-enhanced CT, and Philips Ingenia 1.5T was used for MRI, together with iohexol injection (370 mgI/mL, 1.50 mL/kg, maximum 120.00 mL) when necessary. It is used to detect local recurrence, distant metastases, and recovery of the surgical area; and (5) Nutrition and recovery indicators: Dietary intake, body weight changes, and gastrointestinal function (such as exhaust and defecation time) were monitored daily after surgery, and nutritional status was assessed using the PG-SGA scale once a week, for four weeks. Body weights were monitored with an accuracy of ± 0.10 kg using an Omron HBF-701 body fat scale. PG-SGA ≥ 9 points indicated the need of nutrition intervention.

Statistical analysis

Statistical analysis was performed using IBM SPSS Statistics for Windows, version 26.0. Measurement data were expressed as mean ± SD, enumeration data were expressed as n (%), and intra-group comparisons were performed using t-test and χ² test. An independent sample t test or analysis of variance was used for comparisons between groups. Non-normally distributed data were expressed as medians (quartiles) [M (P25, P75)], and inter-group comparisons were made using the Mann-Whitney U test. The Kaplan-Meier survival curve was constructed using the time of the first occurrence of postoperative complications as the endpoint variable, and the difference in the cumulative incidence of postoperative complications between the abdominal and non-abdominal obesity groups was compared using the log-rank test. Multivariate logistic regression analysis was used to analyze the independent factors influencing the postoperative complications of abdominal obesity. Whether there were complications after operation (0 = no, 1 = yes) was taken as the dependent variable, and possible relevant clinical factors such as sex, age, BMI, abdominal obesity (waist circumference ≥ 90.00 cm for men and ≥ 85.00 cm for women) and combined basic diseases were included as the independent variables to screen the factors with statistical significance. At the same time, the Cox proportional hazard regression model was used to assess the impact of abdominal obesity on the OS and DFS of patients. With the follow-up time as the time variable and death or tumor recurrence as the endpoint event, the covariates of abdominal obesity, surgery, pathological stage, and whether or not to receive adjuvant treatment were included, and the hazard ratio (HR) and its 95% confidence interval were calculated. All statistical tests were performed bilaterally, and P < 0.05 indicated that the difference was statistically significant.

RESULTS

Monitoring of postoperative complications

The overall incidence of postoperative complications was significantly higher in the abdominal obesity group than in the non-abdominal obesity group. The pulmonary infection on POD 3 (P = 0.038), anastomotic leakage on POD 7 (P = 0.042), and moderate-to-severe complications (Clavien-Dindo class III, P = 0.03) were significantly different (Table 2).

Table 2 Monitoring of postoperative complications, n (%).

Complications	Time point	Abdominal obesity group (n = 80)	Non-abdominal obesity group (n = 70)	χ2/t	P value
Pulmonary infection	Day 1	10 (12.50)	4 (5.71)	2.031	0.154
	Day 3	16 (20.00)	6 (8.57)	4.319	0.038
Incision infection	Day 3	7 (8.75)	3 (4.29)	1.132	0.287
Urinary system infection	Day 3	6 (7.50)	2 (2.86)	1.392	0.238
Intestinal obstruction	Day 7	7 (8.75)	3 (4.29)	1.132	0.287
Anastomotic leakage	Day 7	8 (10.00)	2 (2.86)	4.121	0.042
Postoperative haemorrhage	Before discharge	5 (6.25)	1 (1.43)	2.143	0.143
Deep vein thrombosis	Before discharge	4 (5.00)	0 (0.00)	3.677	0.055
Clavien-Dindo class ≥ III	Before discharge	15 (18.75)	5 (7.14)	4.726	0.03

P < 0.05 indicated significant difference.

Detection of biochemical indicators

The WBC count (1 day before surgery, P = 0.034; POD 1, P = 0.015; POD 3, P = 0.03; POD 7, P = 0.01), NEUT% (1 day before surgery, P = 0.031; POD 1, P = 0.037; POD 3, P = 0.013; POD 7, P = 0.018), and CRP level (1 day before surgery, P = 0.048; POD 1, P = 0.015; POD 3, P = 0.022; POD 7, P = 0.016) in the abdominal obesity group continuously increased after surgery. The ALB level on POD 1 was even lower (P = 0.024). The two groups exhibited no significant difference in TP level at any time point (P > 0.05) (Table 3).

Table 3 Detection of biochemical indicators, mean ± SD.

Time point	Abdominal obesity group (n = 80)	Non-abdominal obesity group (n = 70)	χ2/t	P value
WBC count (× 109/L)
1 day before surgery	7.45 ± 1.25	6.80 ± 1.10	2.136	0.034
Day 1	10.24 ± 2.43	9.02 ± 1.98	2.463	0.015
Day 3	9.90 ± 2.10	8.60 ± 1.85	2.184	0.03
Day 7	9.05 ± 1.85	7.80 ± 1.50	2.632	0.01
NEUT%
1 day before surgery	63.50 ± 8.40	60.75 ± 7.90	2.182	0.031
Day 1	72.45 ± 9.50	68.60 ± 8.30	2.104	0.037
Day 3	69.80 ± 8.30	65.30 ± 7.00	2.545	0.013
Day 7	68.20 ± 7.80	64.10 ± 6.90	2.391	0.018
CRP (mg/L)
1 day before surgery	5.35 ± 1.85	4.90 ± 1.20	1.983	0.048
Day 1	21.50 ± 8.75	18.80 ± 7.60	2.465	0.015
Day 3	16.75 ± 6.10	14.90 ± 5.30	2.305	0.022
Day 7	11.25 ± 4.90	9.80 ± 4.20	2.438	0.016
ALB (g/L)
1 day before surgery	38.75 ± 5.40	40.00 ± 4.20	1.621	0.107
Day 1	31.50 ± 5.30	33.20 ± 4.70	2.264	0.024
Day 3	34.00 ± 4.80	35.20 ± 4.30	1.847	0.067
Day 7	36.50 ± 4.00	37.30 ± 3.80	1.472	0.142
TP (g/L)
1 day before surgery	60.00 ± 5.10	61.30 ± 4.60	1.174	0.242
Day 1	57.20 ± 5.80	58.10 ± 5.30	1.132	0.258
Day 3	58.00 ± 6.00	59.50 ± 5.80	1.059	0.291
Day 7	59.20 ± 5.60	60.00 ± 5.40	1.312	0.191

P < 0.05 indicated significant difference. WBC: White blood cell; NEUT%: Neutrophil percentage; CRP: C-reactive protein; ALB: Albumin; TP: Total protein.

Detection of tumor markers

The levels of CEA (3 months after surgery, P = 0.039) and CA19-9 (1 day before surgery, P = 0.034; 3 months after surgery, P = 0.048) were significantly higher in the abdominal obesity group (Table 4).

Table 4 Detection of tumor markers, mean ± SD.

Time point	Abdominal obesity group (n = 80)	Non-abdominal obesity group (n = 70)	χ2/t	P value
CEA (ng/mL)
1 day before surgery	3.90 ± 1.15	3.70 ± 1.00	1.001	0.318
Day 7	5.80 ± 2.30	5.20 ± 2.00	1.402	0.162
Month 3	6.10 ± 2.40	5.30 ± 2.10	2.092	0.039
CA19-9 (U/mL)
1 day before surgery	32.50 ± 5.80	30.20 ± 4.50	2.136	0.034
Day 7	35.00 ± 6.20	33.10 ± 5.70	1.21	0.227
Month 3	37.00 ± 6.80	34.60 ± 5.40	1.983	0.048

P < 0.05 indicated significant difference. CEA: Carcinoembryonic antigen; CA19-9: Carbohydrate antigen 19-9.

Imaging follow-up evaluation

The local recurrence rates were higher than those in the non-abdominal obesity group 30 days (P = 0.046) and three months (P = 0.037) after surgery (P < 0.05). There was no significant difference between the two groups in terms of distant metastasis or recovery of the operative area (P > 0.05; Table 5).

Table 5 Imaging follow-up evaluation, n (%).

Time point	Abdominal obesity group (n = 80)	Non-abdominal obesity group (n = 70)	χ2/t	P value
Postoperative day 30	Local recurrence: 15 (18.75)	Local recurrence: 7 (10.00)	3.984	0.046
	Distant metastasis: 6 (7.50)	Distant metastasis: 4 (5.71)	1.123	0.29
	Poor recovery in the operation area: 4 (5.00)	Poor recovery in the operation area: 3 (4.29)	0.978	0.323
	Good recovery was achieved in the operation area: 55 (68.75)	Good recovery was achieved in the operation area: 56 (80.00)	2.586	0.108
3 months after surgery	Local recurrence: 18 (22.50)	Local recurrence: 9 (12.86)	4.351	0.037
	Distant metastasis: 7 (8.75)	Distant metastasis: 5 (7.14)	0.743	0.389
	Poor recovery in the operation area: 5 (6.25)	Poor recovery in the operation area: 3 (4.29)	1.169	0.28
	Good recovery was achieved in the operation area: 50 (62.50)	Good recovery was achieved in the operation area: 53 (75.71)	2.833	0.092

P < 0.05 indicated significant difference.

Nutrition and recovery indicators

Dietary intake (day 7, P = 0.043) and body weight change (P = 0.029) in the abdominal obesity group were significantly lower than in the non-abdominal obesity group. Regarding the recovery of gastrointestinal function, patients in the abdominal obesity group had longer defecation times (day 3, P = 0.038; day 7, P = 0.042). The PG-SGA showed that the nutritional status of the abdominal obesity group was poor (week 1, P = 0.032; week 4, P = 0.021) (Table 6).

Table 6 Status of nutrition and recovery indicators, mean ± SD.

Time point	Abdominal obesity group (n = 80)	Non-abdominal obesity group (n = 70)	χ2/t	P value
Dietary intake and body weight change (kcal)
Day 1	1200.00 ± 150.00	1300.00 ± 180.00	1.607	0.115
Day 7	1300.00 ± 160.00	1400.00 ± 170.00	2.026	0.043
Body weight change (kg)	-2.80 ± 0.90	-2.20 ± 0.80	2.213	0.029
Gastrointestinal function recovery (exhaust and defecation time) (hour)
Day 3	48.00 ± 12.00	42.00 ± 10.00	2.078	0.038
Day 7	72.00 ± 14.00	65.00 ± 13.00	2.075	0.042
PG-SGA scale
Week 1	8.30 ± 2.10	7.20 ± 1.90	2.136	0.032
Week 4	9.10 ± 2.30	7.80 ± 2.10	2.369	0.021

P < 0.05 indicated significant difference. PG-SGA: Patient-Generated Subject Global Assessment.

Analysis of survival curve

The survival curve of the abdominal obesity group showed a significantly steeper decline over the 24-month follow-up period than the non-abdominal obesity group, indicating that the time to the first postoperative complication was shorter in patients with abdominal obesity. The abdominal obesity group demonstrated a notably higher risk of complications within the first 3-6 months, and a sustained elevated risk up to 18 months postoperatively. The log-rank test indicated a significant difference in the cumulative incidence of postoperative complications between the abdominal obesity group and the non-abdominal obesity group (χ² = 5.817, P = 0.016; Figure 2).

Figure 2  Survival curve.

Logistic regression analysis

Logistic regression analysis showed that abdominal obesity (OR: 3.843, P = 0.001) and increased BMI (OR: 1.093, P = 0.013) were independent risk factors for postoperative complications and that the combination of basic diseases was nearly significant (P = 0.055; Table 7 and Figure 3).

Figure 3 Forest plot results of logistic regression analysis. BMI: Body mass index; 95%CI: 95% confidence interval.

Table 7 Results of logistic regression analysis.

Factor	β	SE	Wald χ2	P value	OR	95%CI
Constant term	-0.564	0.245	5.178	0.023	0.569	0.332-0.979
Abdominal obesity (yes)	1.345	0.412	10.512	0.001	3.843	1.750-8.451
Age (1 year for each additional)	0.032	0.021	2.227	0.136	1.033	0.991-1.077
BMI (per 1 kg/m2 increase)	0.089	0.036	6.165	0.013	1.093	1.018-1.174
Combined basic disease (yes)	0.512	0.265	3.693	0.055	1.668	0.986-2.808

P < 0.05 indicated significant difference. BMI: Body mass index; OR: Odds ratio; 95%CI: 95% confidence interval.

Cox risk regression analysis

The results of the Cox regression analysis showed that abdominal obesity was an independent risk factor for OS (HR: 1.937, P = 0.011) and DFS (HR: 1.769, P = 0.018). Pathological staging and adjuvant treatment also significantly affected prognosis (Table 8).

Table 8 Cox risk regression analysis results.

Factor	β	P value	HR	95%CI
OS
Constant term	-1.14	0.004	0.32	-
Abdominal obesity (yes)	0.661	0.011	1.937	1.158-3.243
Pathological staging (III)	1.079	0.001	2.941	1.606-5.388
Adjuvant treatment (no)	0.794	0.007	2.212	1.237-3.954
DFS
Constant term	-0.921	0.012	0.398	-
Abdominal obesity (yes)	0.57	0.018	1.769	1.102-2.842
Pathological staging (III)	1.147	< 0.001	3.15	1.778-5.582

P < 0.05 indicated significant difference. OS: Overall survival; DFS: Disease-free survival; HR: Hazard ratio; 95%CI: 95% confidence interval.

DISCUSSION

In this study, visceral obesity was taken as the breakthrough point to explore its impact on postoperative complications and the long-term prognosis of tumors in elderly patients with CRC. The results showed that the abdominal obesity group had adverse trends in the incidence of postoperative complications, biochemical inflammation, deterioration of immune nutritional status, and a continuous increase in tumor markers, further confirming the adverse effects of visceral obesity as a potentially high-risk metabolic phenotype in elderly patients with CRC. The incidence of postoperative complications, such as pulmonary infection, incision infection, and anastomotic leakage, was significantly higher in the abdominal obesity group than in the non-abdominal obesity group. This condition is closely related to factors such as a narrow field of vision during abdominal surgery, poor blood supply to adipose tissues, and a persistent inflammatory state caused by visceral obesity[9]. Consistent with previous studies, the more visceral fat accumulated, the more difficult the operation and the higher the risk of anastomosis tension and ischemia, thus increasing the probability of fistula formation and infection[10]. The high-definition laparoscopy and energy platform adopted in this study improved the accuracy during surgery; however, it was still difficult to completely offset the structural and anatomical challenges posed by abdominal obesity[11]. In terms of inflammation and the immune response, the postoperative CRP and NEUT% values in the abdominal obesity group were consistently higher than those in the non-abdominal obesity group, indicating that the patients were in a more intense and persistent systemic inflammatory state. It has been pointed out that visceral fat, as an active endocrine organ, can continuously release pro-inflammatory factors such as IL-6 and TNF-α, activate the NF-κB pathway, and induce systemic inflammatory response[12]. Chronic low-grade inflammation not only weakens postoperative tissue repair but may also aggravate postoperative infections by affecting the function of the intestinal mucosal barrier[13]. The findings of this study are consistent with those of previous studies. Peak postoperative CRP level was positively correlated with abdominal obesity and linearly correlated with the risk of complications[14]. From the perspective of nutritional and immune statuses, ALB and TP levels decreased more significantly in the abdominal obesity group after surgery, suggesting vulnerability to nutritional reserve and inflammatory depletion. The traditional view holds that the obese are “overnourished”, but in fact, the patients with abdominal obesity are often accompanied by “latent malnutrition”, which is more common especially in the elderly[15]. Inflammation-induced ALB leakage, increased intestinal permeability, and limited postoperative food intake exacerbate postoperative nutritional failure and delay recovery[16]. More importantly, the tumor markers CEA and CA19-9 decreased more slowly in the abdominal obesity group than in the non-abdominal obesity group at follow-up visits at seven days and three months after surgery, and the indicators even rebounded in some patients. This suggests that abdominal obesity not only affects short-term perioperative recovery but also promotes the growth of residual cancer cells and enhances the invasive ability of tumor cells through fat-related signaling pathways, thereby affecting long-term prognosis[17]. Previous studies have pointed out that patients with high VFA values have a significantly increased recurrence rate within one year after surgery, which is consistent with the preliminary follow-up results of this study[18]. Although there was no statistically significant difference between the two groups in basic diseases such as hypertension and diabetes, visceral obesity, as the central manifestation of “metabolic syndrome”, may work together with these subclinical metabolic abnormalities, enhance the inflammatory response, and accelerate vascular endothelial damage, thereby creating a biological environment that is extremely unfavorable for counter-surgery and tumor treatment.

This study clearly demonstrates that visceral obesity significantly increases the risk of perioperative complications. The main reason is that a large amount of visceral fat deposition not only blocks the anatomical signs and increases the difficulty and operation time of the operation, but also affects the visibility of blood vessels and intestinal tubes, thus reducing the degree of surgical refinement and increasing the tension of the anastomosis, thereby improving the risk of anastomotic leakage[19]. Simultaneously, patients with visceral obesity usually have high intra-abdominal pressure and difficulty in maintaining pneumoperitoneum during surgery, further increasing the risk of bleeding and postoperative recovery time. Visceral adipose tissues are prone to mechanical damage during surgery, releasing a large amount of adipocyte debris and inflammatory factors, resulting in the aggravation of postoperative abdominal inflammation[20]. From the perspective of immune inflammation, the inflammatory indicators of patients with visceral obesity after surgery are significantly increased, and recovery is slow, revealing the existence of a “chronic inflammatory background”. Studies have shown that visceral adipose tissue is an active endocrine organ that can continuously secrete pro-inflammatory factors (such as TNF-α and IL-6), chemokines (such as monocyte chemoattractant protein-1) and adipokines (such as leptin and resistin) to form a “low-grade chronic inflammation”[21]. In this state, the acute inflammatory reaction caused by postoperative trauma cannot be stopped quickly, but may present a magnification effect owing to the high load of basic inflammation, leading to more common complications of postoperative infection and poor healing of patients. Leptin can promote angiogenesis and tumor cell proliferation, whereas adiponectin is decreased in obesity, resulting in impaired anti-inflammatory and antiproliferative effects. Collectively, these factors promote the growth and recurrence of postoperative micrometastases. In terms of tumor biological mechanisms, a key pathway by which visceral obesity affects tumor outcomes is the “metabolism-immunity-inflammation axis”[22]. Studies have shown that visceral fat activates tumor cell metabolism and enhances the anti-apoptotic ability through the PI3K/Akt/mTOR pathway. HIF-1α signal can promote the expression of hypoxia-inducible factor and accelerate angiogenesis. The JAK/STAT pathway activates the pro-inflammatory pathway and interferes with T cell-mediated immune surveillance[23]. In this study, we also observed that the CEA and CA19-9 decreased slowly in patients with visceral obesity after surgery, suggesting that the residual lesions had a stronger resistance to immune clearance, or there was “hidden survival” of tumor cells. In recent years, many transcriptome and metabolome studies have revealed that visceral obesity can promote the transformation of colorectal tumors into more aggressive molecular subtypes by altering the metabolite spectrum and immune cell infiltration patterns in the microenvironment of colorectal tumors. Compared with previous studies focusing on BMI or simple obesity, this study used VFA to measure the intra-abdominal fat area, which can more accurately assess the impact of visceral obesity on patients with tumors. The traditional BMI cannot distinguish between muscles and fat. Particularly in the elderly, the “hidden obesity” with normal BMI but actual existence of muscle deficiency and visceral fat accumulation cannot be ignored. The results of this study support that “VFA ≥ 100 cm²” is the cutoff value for the determination of visceral obesity, and this indicator shows good sensitivity and specificity in multiple prediction models. In the elderly population, the effect of visceral obesity is complex. On the one hand, the basal metabolic rate of the elderly is decreased, and adipose tissues are more inclined to visceral deposition; on the other hand, coinfection of immune aging and chronic diseases (such as diabetes and hypertension) further weakens its anti-tumor ability, thus amplifying the negative effects of visceral obesity[24]. This also indicates that visceral obesity should be considered as a core consideration in the construction of a more refined risk assessment model for elderly patients with CRC. Beyond inflammatory pathways (IL-6, TNF-α), visceral obesity may promote CRC metastasis through adipokine-mediated epithelial-mesenchymal transition (EMT) and gut microbiome dysbiosis. Adipose-derived leptin activates STAT3 signaling to induce EMT[21], whereas dysbiosis impairs intestinal barrier function and facilitates bacterial translocation[22]. Collectively, these mechanisms create a tumor-permissive microenvironment.

In this study, we quantified the impact of visceral obesity (with VFA as the index) on postoperative complications and long-term prognosis of CRC in the elderly and identified it as an important independent risk factor with significant clinical value. These findings contribute to preoperative risk stratification and guide individualized perioperative management and rehabilitation strategies, which are of practical significance, especially in the elderly population. The innovation of this study lies in the fact that abdominal CT is used to measure VFA instead of traditional BMI, which accurately reflects the visceral fat load. For the first time, we systematically analyzed the dynamic relationship between VFA and inflammatory, immune, and tumor markers.

The limitation lies in its single-center retrospective design with a limited sample size. Covariates such as myopathy were not included, and future studies should adopt multicenter prospective designs to explore the molecular mechanisms through metabolomics and immunohistochemistry. Additionally, an investigation into the potential of fat-reduction interventions to improve postoperative outcomes is warranted.

CONCLUSION

In summary, this study has clearly pointed out that visceral obesity is an independent factor contributing to the increase in postoperative complications and poor long-term prognosis of elderly patients with CRC. Therefore, implementing prehabilitation programs targeting visceral fat reduction - such as 12-week preoperative regimens combining high-protein nutrition support (1.5 g/kg/day) and moderate-intensity aerobic exercise (150 minutes/week) - may improve surgical outcomes. It systematically affects tumor treatment outcomes through multiple mechanisms, including increased technical difficulty in surgery, postoperative inflammation amplification, activation of tumor pathways by metabolic abnormalities, and immune escape. Therefore, in clinical practice, visceral obesity should be considered an important index for preoperative evaluation. Targeted nutrition, exercise intervention, and perioperative management are expected to improve the overall treatment benefit for elderly patients with CRC. Future economic evaluations should assess the cost-effectiveness of routine VFA measurements using computed tomography. Preliminary modeling suggests that this approach may reduce costs when targeting high-risk populations by reducing complication-related expenditures.