RISK FACTORS AND THEIR IMPACT ON THE STATE OF COLORECTAL ANASTOMOSIS

The aim of the work was to evaluate the effect of risk factors on the development of leakage of mechanical colorectal anastomosis after surgeries for rectal cancer. Materials and methods. The study involved 129 patients who underwent anterior and low anterior resection of the rectum with simultaneous formation of colorectal anastomosis with a circular stapler in the period from 2005 to 2017. The patients’ age was 33 to 84 years. Adenocarcinoma of varying differentiation degrees was diagnosed in all cases, but the most common was moderately differentiated tumour – 112 patients (86.8%). Results. The overall incidence of anastomotic leak in resection of the rectum was 6.2%, and all cases required active surgical approach. The risk of failure of colorectal anastomosis significantly increased in the presence of adverse factors in the patients: tumour size ≥4–5 cm; constrictive nature of the tumour growth; depth of the malignant invasion in the rectal wall; anastomosis localisation in the subperitoneal pelvic segment (low anterior resection); male gender of the patients. Additional strengthening of the mechanical anastomosis defect area with interrupted sutures helped prevent the risk of severe complications. Formation of preventive stomas is indicated after low anterior resection of the rectum in the presence of risk factors. Conclusions. The obtained results suggest that adequate preparation of the segmented intestine, precision mobilisation of the rectum and mesorectum, prevention of the suture line tensioning, compliance with mechanical anastomosis technique, monitoring its tightness, and risk management enables formation of a safe suture and are an important component in the prevention of anastomotic leak.


INTRODUCTION.
Radical surgery is the main stage of combined treatment for colorectal cancer. The main aim of this intervention is not only to follow all the principles of oncologic treatment but also to perform a functionally beneficial sphincter-sparing procedure [1; 2]. Anterior resection of the rectum was proposed and developed by Dixon in the 1930s. In Russia, the first anterior resection was performed by Petrov in 1937 [3]. In the past decades, this surgery became widespread in all the specialized clinics. Despite the accumulated experience of rectal surgery in the world practice, the rate of postoperative septic complications remains high (6-25%) [4; 5]. The main reason for the unsatisfactory outcome is the development of colorectal anastomotic dehiscence (AD) that is observed in 2.5-21% of cases according to different authors [6; 7]. On the one hand, the development and implementation of preventive measures targeted to cope with the specified complications, the use of circumferential staplers, and the formation of preventive intestinal stomas allowed surgeons to improve direct results and functional part of surgical treatment. On the other hand, the study of risk factors and the evaluation of their influence on the outcome of the surgery in each case is an integral part of the scientific search for the solution of the problem of colorectal AD after anterior and low anterior resection of the rectum [8; 9]. Despite the vast possibilities of modern surgical techniques that allow for a significant reduction of the rate and severity of postoperative complications, anastomotic dehiscence (AD) can still lead to fatal complications [10]. The fact that it is impossible to predict the development of AD before the surgery and its diagnostics in the early postoperative period decreases the effectiveness of preventive measures and leads to late treatment of the developed complications. In the present study, the authors analyzed the clinical material on this problem and the risk factors that influence the direct outcome of the treatment in patients that underwent resection of the rectum with simultaneous formation of colorectal anastomosis.
The study was aimed to evaluate the influence of the risk factors on the development of mechanical colorectal AD after the surgery for colorectal cancer.

MATERIALS AND METHODS.
The authors performed a retrospective analysis of 129 patients that underwent anterior and low anterior resection of the rectum with simultaneous formation of colorectal anastomosis with a circumferential stapler in 2005-2017.
The study protocol followed guidelines for experimental investigation with human subjects in accordance with the Declaration of Helsinki and was approved by the ethics committee. Written informed consent was obtained from each patient (or an official representative) before the study.
The characteristic of patients by sex and age depending on the volume of surgical intervention is presented in Table 1. The patients' age varied from 33 to 84 years old. There were more women in the study. For the evaluation of the level of the formation of colorectal anastomosis on its dehiscence, the patients were divided by this criterion. In all the cases, adenocarcinoma of different degrees of differentiation was diagnosed. In the majority of cases (112 patients, 86.8%), moderately differentiated tumor was revealed. The localization of the tumor in the rectum is presented in Table 2. The characteristic of the tumor by the degree of invasion into the intestinal wall by the group of patients is presented in Table 3. Comorbid diseases were revealed in all the patients in different degrees of compensation (Table 4). The mean body mass index (MBI) was 24.2±3.4 kg/m 2 and was within the range from 16.4 to 33.4 kg/m 2 . In 8 patients with obesity, lower anterior resection of the rectum was performed. In 7 cases, the anastomosis was localized 10 cm superior to linea anocutanea.
The results of the laboratory parameters revealed anemia in 83 patients (64.3%), the level of hemoglobin varied from 72 to 118 g/L. Patients with anemia of the 2nd-3rd degree (12 patients, 14.4%) needed blood transfusion in the postoperative period. Taking into account the fact that the level of albumin in blood influences the healing of anastomosis, the authors controlled this parameter. In the postoperative period, 23 patients had hypoalbuminemia, i.e. the content of protein was less than 28 g/L, which required profound correction in the postoperative period.
The anastomosis was classified as low when it was located from 10 cm and inferior to the dentate line [7]. The lower pole of the tumor in patients from the studied groups was located 6.0-15.5 cm from the anorectal line. The distal edge of the resection was 2 cm caudal to the lower border of the tumor. Patients with low anterior resection of the rectum underwent total mesorectal excision with precision isolation of the interfascial layer.
In 104 patients (80.6%), the rectal stump was formed with the apparatus "Contour" (Ethicon, USA), in the rest cases, the sutures were made manually. The colorectal anastomosis was formed end-to-end with a circumferential stapler of the required diameter (29.31 mm). After the formation of anastomosis, air testing of the sealed sutures was performed. The mean duration of the surgery was 165.2±32.1 (124-360 minutes). The longest duration of surgery was in patients with low anterior resection. However, there was no significant difference in the duration depending on the level of anastomosis location (p=0.625).
In After the surgery, 80 patients (62%) underwent pelvic peritoneum repair. In all the cases, the pelvic cavity was drained via the contraincision in the anterior abdominal wall.

RESULTS.
In 8 cases (6.2%), AD was diagnosed on Days 3 to 7. Patients developed clinical signs of peritonitis. The intestinal discharge was observed in the drainage. In 5 cases (7.9%), AD developed after lower anterior resection of the rectum, in 3 cases (4.5%)after anterior resection. The rate of AD was significantly higher in patients after low anterior resection of the rectum (p=0.324).
The analysis of the AD causes showed that it primarily occurred in men (5 patients) and patients aged 61-80 years old (4 patients). In 2 patients with AD, the volume of intraoperative loss was more than 700 ml, which required donor blood and plasma transfusion. The multifactor analysis revealed that the volume of blood loss and intraoperative blood transfusion did not influence significantly the occurrence of AD (p=0.633). At the same time, male sex was an independent significant risk factor (p=0.344).
The tumor size (more than 4-5 cm), circular growth, and the degree of its ingrowth into the According to the available published data, one of the risk factors for AD is the period of drainage of pelvic organs [5; 11]. In the present study, the drainage tubes were removed after the first defecation on Days 3-6 provided there was no pathological discharge.
The lethal outcome was registered in 3 cases. In 2 cases, it was caused by AD after anterior resection with further complications that required multiple relaparotomy interventions and led to the development of multi-organ failure. In 1 case, it was caused by pulmonary artery thromboembolism in spite of the performed preventive measure before and after the surgery.
The results of the present study showed an increase in the occurrence rate of AD after low anterior resection of the rectum. In patients with several risk factors and prognosis for the possible occurrence of AD, a preventive stoma should be exteriorized. The authors did not reveal any significant differences in the rate of colorectal AD depending on the method of rectal stump sealing: manual sutures or with a stapler. There was no significant difference either in the influence of the duration of the surgery, the volume of the blood loss, and intraoperative blood transfusion. A retrospective analysis and the obtained results of the study showed that adequate preparation of the segmented intestine, a precision technique of the rectum and mesorectum mobilization, prevention of the suture tensioning, following the protocol of the mechanical anastomosis formation, control of its sealing, and consideration of the risk factors provide a reliable suture and an important part of the prevention of AD. The period of drainage of pelvic organs should last not less than 2-3 days after the patient's first defecation.

CONCLUSIONS.
1. The occurrence rate of AD in patients with the resection of the rectum was 6.2% and required active surgical tactics in all the cases.
2. The risk of AD development significantly increased in patients with unfavorable factors: tumor size ≥4-5 cm; obstructive tumor growth, depth of the tumor ingrowth into the rectal walls, localization of the anastomosis in the subperitoneal area of the pelvis (low anterior resection), and male sex.
3. Additional enforcement if the defected area of the mechanical anastomosis with interrupted node sutures prevents the development of severe complications. The formation of the preventive stomas is necessary after low anterior resection of the rectum in patients that are exposed to risk factors. The stoma itself does not increase the risk of the development of AD.

FINANCIAL SUPPORT AND SPONSORSHIP
Nil.