Abdominal surgery is one of the most common procedures in general surgery. Intra-abdominal hemorrhage after abdominal surgery refers to cases in which there is postoperative drainage of hemorrhagic fluid in the abdominal drainage tube or imaging evidence indicating intra-abdominal hemorrhage with abdominal distension and a decrease in hemoglobin, which can also be confirmed by reoperative exploration, imaging examination, or endoscopy (1). If not timely detected, postoperative hemorrhage will lead to increased complications and severe consequences even if the surgery performed was minimally invasive. This makes postoperative hemorrhage one of the leading causes of death after abdominal surgery (2). Furthermore, heavy secondary postoperative bleeding is often ignored, which can result in a high incidence of complications as well as a prolonged hospital stay. When compared with primary bleeding, secondary bleeding is more likely to cause hemorrhagic shock, disseminated intravascular coagulation, and multiple organ failure, eventually leading to increased mortality.

In this study, patients with postoperative abdominal hemorrhage admitted to a large public hospital were selected as research participants. The clinical history of the patients was determined and a clinical analysis was conducted to identify options that can be recommended for the prevention and treatment of postoperative hemorrhage.

Postoperative abdominal hemorrhage is a common complication, with a majority of patients requiring surgical, endoscopic, or embolic intervention. Some of the patients with this condition even require more than one procedure. Similarly to the secondary bleeding observed following hypertensive intracerebral hemorrhage, as proposed by Brott (3), secondary bleeding may also occur after abdominal surgery. Such bleeding occurs in other parts of the abdominal cavity after stabilization of the first bleeding incident requiring hemostasis measures, and is known as secondary bleeding. In this study, the location of the secondary bleeding differed from that of the primary bleeding incident in all 32 patients in whom multiple bleeding events occurred. If the primary bleeding is not stopped, the severe consequences of rebleeding could lead to life-threatening outcomes, thereby significantly increasing the mortality rate. In this study, among the 22 patients who died, 13 died of hemorrhagic shock and 6 died of hemorrhagic shock combined with infectious shock, accounting for 86.4% of the total deaths. This shows that severe postoperative hemorrhage has a major negative impact on prognosis. Unsuccessful hemostasis can lead to severe consequences, such as disseminated intravascular coagulation, multiple organ failure, and even death.

In this study, the significant predictors of secondary hemorrhage were duration of operation >5 h and intervention time >5 h; these were independent risk factors. The effect of longer operation time can be attributed not only to the difficulty of the operation but also to hesitation on the part of the surgeon or excessive dissection of vessels. Difficult and complicated operations generally require more blood vessels to be ligated, more anatomical parts to be anastomosed and removed, and more wounds to be exposed. A prolonged operation time also increases the possibility of damage to the blood vessels and insufficient hemostasis, thereby significantly elevating the risk of repeated bleeding. In addition, acidic metabolites in the body can accumulate over time, leading to metabolic acidosis and resulting in an increase in oxygen free radicals and mitochondrial damage. This ultimately increases the incidence of secondary hemorrhage. Some surgeons prefer surgery over other options for treatment; however, excessive vascularization could lead to unnecessary complications, such as repeated postoperative bleeding. Liu et al. (4) believe that vascular skeletonization and lymph node dissection could facilitate corrosion of the exposed blood vessels by the digestive fluids and infectious factors exuding from the anastomosis, which can lead to rupture and bleeding of the blood vessels.

In this study, intervention time refers to the time between the detection of bleeding and the initiation of hemostatic treatment. Several factors can lead to a prolonged intervention time. (1) First, most sentinel hemorrhages will first lead to a small amount of bleeding in the abdominal drainage tube or nasogastric tube, and then the bleeding will stop for a short period; these events are often ignored by clinicians. At this time, if relevant examinations and effective hemostasis measures are not carried out, this may lead to massive hemorrhage at timescales up to a few hours or a few days later, with incidence rates of 33.3% to 71.0% (5, 6). Statistics indicate that the mortality rate of patients with sentinel hemorrhage is significantly higher than that of those without sentinel hemorrhage (up to 57%)(1, 7). Therefore, ward clinicians should closely observe the quantity and properties of the drainage fluid in the drainage tube and gastric tube, dynamically perform routine blood tests, analyze coagulation function and arterial blood gas, and monitor real-time changes in the vital signs of their patients. Patients should be under observation for sentinel hemorrhage, and if suspected, effective intervention measures must be immediately taken. (2) Some patients do not show obvious clinical symptoms, and the vital initial signs of postoperative bleeding remain temporarily stable. This might easily be ignored by doctors, thereby prolonging the interval before treatment is initiated. (3) Intraperitoneal hemorrhage in some patients who first undergo non-surgical intervention, such as interventional hemostasis or endoscopy, can be left incompletely cured, leading to extension of the treatment time and an increase in the difficulty of establishing hemostasis. (4) Finally, it cannot be ruled out that the doctor on duty may not take the condition seriously when hemorrhage occurs during their night shift break. Usually, the night shift nurse would report conditions such as a decrease in hemoglobin levels or a change in the vital signs to the resident physicians. However, clinicians may not only fail to understand the serious nature of these conditions, but also fail to report them to their superiors in time. Ultimately, no therapeutic clinical decision is made in such cases, and secondary bleeding continues.

Figure 1 shows the management of postoperative bleeding in this study, which determined the exclusion and inclusion criteria. Surgical hemostasis clearly demonstrated the highest success rate (84.4%) when compared with interventional embolization (26.7%) and endoscopic treatment (50%). For a very long time, secondary surgery has been considered the preferred treatment for postoperative abdominal bleeding. Despite the rise in the popularity of interventional embolization (8–10) and endoscopic therapy (11), the importance of surgery remains undiminished. In this study, 15 patients were administered endovascular treatment (EVT), including 10 patients with visceral arterial hemorrhage. Theoretically, the bleeding site of the superior mesenteric artery and the three major branches of the celiac trunk can be accurately located and embolized to establish “intravascular hemostasis”. However, if the amount of bleeding is large, with a decrease in the blood pressure, vasospasm contraction, blood clot blockage, etc., his may lead to false negative angiography results. If EVT is incomplete, a surgical approach is still the most beneficial option (12). Similarly, electronic endoscopy can identify specific bleeding sites, and isolated bleeding sites can be clamped with vascular clips or electrocoagulation in order to achieve hemostasis (11). However, when hemorrhage is difficult to control, and also in case of a blurred visual field, an informed decision on the second operation should be made (5). Although the surgical approach seems to be difficult and risky due to postoperative adhesions, and is dependent on whether the condition of the patient is critical, it has the advantages of clear vision and complete hemostasis. The key to treatment of active bleeding is early surgical hemostasis. Generally, surgery is the only treatment option for a patient in a critical condition. The principles of surgical treatment are first to stop the bleeding, then to repair the affected part, and finally to perform a third excision of the damaged part. The treatment should be simple, effective, fast, and safe. It is important to note that if hemostasis is not reliably established, bleeding may start again.

According to the 2007 ISGPS consensus (13), the timing of bleeding events can be divided into “early” and “late,” with “early” denoting bleeds occurring less than 24 h postoperatively and “late” denoting those occurring more than 24 h postoperatively. Early hemorrhage is mainly associated with surgical techniques, such as incomplete arterial ligation, vascular clip detachment, anastomotic bleeding, and oozing of blood from abdominal wounds; in contrast, late hemorrhage is mostly attributable to vascular corrosion, usually associated with pancreatic fistula and abdominal infection (1, 14). Previous studies have reported that the mortality rate after secondary surgery in hemodynamically unstable patients with delayed bleeding is as high as 64% (15). Delayed bleeding after abdominal surgery is associated with an increased risk of secondary bleeding and a significant increase in patient mortality following ­secondary bleeding (16, 17).

During abdominal surgery, if multiple organs are removed or additional surgical operations are performed, the patient can experience major trauma and is subjected to a higher risk of vascular and wound hemorrhage. Intra-abdominal infection observed after abdominal surgery is often caused by pancreatic fistula, biliary fistula, intestinal fistula, etc. The underlying mechanisms may involve the activation of digestive enzymes due to local infections and abscesses in the abdominal cavity, which then erode important blood vessels and lead to anastomotic leaks, thereby causing poor patient prognosis (18). When intra-abdominal bleeding fails to drain, it can cause local stasis and blockage to the extent that some bacteria and inflammatory substances will take the opportunity to breed, promoting intra-abdominal infection. Loos (19) et al. found that Pseudomonas aeruginosa and Enterococcus faecium in the peritoneal drainage fluid may have the ability to activate pancreatic enzymes, which can trigger tissue necrosis and vascular erosion, causing abdominal infection (20). This risk can be managed during the operation by removing the accumulated blood completely, eliminating the risk factors for subsequent infection (21). However, this cannot be achieved by conservative treatment or invasive interventional hemostasis measures.

There are certain limitations to the present study. First, as this was a retrospective study, it is susceptible to potential bias and selection bias. Second, retrospective studies like the present one cannot establish causal relationships, but only associations. Despite these limitations, this is the first study to describe and report secondary hemorrhage after abdominal surgery, which has not often been reported on in previous studies. Second, this was a large-scale study with an emphasis on human factors. Third, survival curves were established to illustrate the outcomes of primary bleeding and secondary bleeding, directly reflecting the poor prognosis associated with secondary hemorrhage. Fourth, this study reviewed current practices and outcomes to identify confirmed cases in order to make a valid estimation of multiple relevant risk factors. Fifth, this study examined the timing of hemorrhage and its association with mortality and intervention type. The selection bias in this study was minimized by adjusting all cases using appropriate and rigorous statistical methods.

The analysis of the underlying causes of secondary bleeding in each of the two groups demonstrated the critical role played by subjective human factors. Skilled and careful surgery and strict perioperative treatment and management are the major factors that can help clinicians to largely avoid secondary hemorrhage. Prevention of postoperative hemorrhage requires greater responsibility on the part of surgeons. The occurrence of postoperative hemorrhage in abdominal surgery is not only related to the condition of the patient, but is also closely related to the surgical techniques employed and the proficiency of the chief surgeon (22). During the operation, the surgeon should avoid blind skeletonization of the blood vessels and cover the wound surface with natural omentum or biological agents to the greatest extent possible. In addition, ligatures should be moderately tightened to avoid avulsion of the artery due to the application of excessive force. The placement of the abdominal drainage tube is highly critical in providing key evidence of postoperative hemorrhage. A suitable abdominal drainage tube can not only allow smooth drainage but also provide early warning of intra-abdominal bleeding. In some patients with early bleeding, no significant changes are observed in their vital signs or abdominal signs. Therefore, performing a CT scan even in patients with active bleeding could help the surgeon to localize the bleeding site. Once a hemorrhage occurs, timely identification of the bleeding site and proper selection of an appropriate hemostasis program are the keys to successful treatment. An analysis of specific risk factors for bleeding is important to improve the prognosis of patients with abdominal postoperative hemorrhage.

Briefly, this study effectively evaluated the risk predictors of secondary hemorrhage and demonstrated that longer operation time and extended intervention time are independent risk predictors. The success rate of surgical hemostasis is higher than those of interventional embolism and endoscopy, indicating that surgical hemostasis is the best option to manage bleeding after abdominal surgery. We conclude that secondary bleeding is positively associated with postoperative mortality. Therefore, efforts by surgeons to improve their operative techniques and ensure proper postoperative management will substantially help in reducing the incidence of postoperative hemorrhage and in gradually preventing morbidity and mortality.