Since the publication of the article “Concept and techniques of presacral cyst excision” in the Chinese Journal of Surgery, we often received telephone inquiries from patients all over the country, which were roughly summarized as follows: “The patient underwent presacral cyst excision in a hospital, and the operator was a relatively experienced local surgeon. Half a month after the anterior drainage tube was removed, cystic effusion appeared again in the presacral area, and the drainage tube had to be placed again, and so on repeatedly. The longest medical history is more than 1 year.” The common question that these callers responded was “Why can’t the drainage tube be removed after anterior sacral cyst surgery?” . The common answer to these questions is also only one, that is, “there is residue in the wall of the presacral cyst”. Why is the wall of the presacral cyst not removed cleanly and there is residue? According to clinical experience and knowledge of the disease, the main points are as follows: 1. The deceptive nature of the presacral cyst. If described by daily life scenarios, then presacral cyst, the disease carries a certain deceptive nature, which can also be described as a trap. The object of deception is the doctor and the trap set for the doctor. Why is this so? Because medicine itself is largely a practical, empirical science, and it is sometimes difficult to achieve a deep understanding if one has not experienced it. Anterior sacral cysts are one such type of disease that, without experience and deep thought, do not have a deep understanding. While cysts in other parts of the abdominal cavity are generally easy to peel or remove, or even do not require treatment, such as liver cysts, kidney cysts, and ovarian cysts, presacral cysts are very different from other cysts. Presacral cysts are a type of cystic mass located below the pelvic peritoneal fold and in the anterior sacral space. Since the imaging of this type of mass (pelvic CTMRI) usually shows a cystic texture, complete envelope, clear boundary, and obvious gap with surrounding tissues, it is no different from other cysts, and it is easy to give the surgeon the illusion that it is easy to be removed completely. 2.Complexity of the surrounding tissues of presacral cysts. Because most of the imaging manifestations of presacral cysts are cyst occupancy with clear boundary and clear gap of surrounding tissues, it is easy to give surgeons a false impression that presacral cysts are like abdominopelvic cysts (e.g. ovarian cysts), with clear boundary and easy to be separated and excised. Clinical practice proves that although the pre-sacral cysts have a cystic form and clear borders on imaging, most of the cyst walls are densely adherent to or fused with the rectal wall, and it is quite difficult to separate them from the rectal wall completely. Some of the fibrous tissue of the cyst wall is infiltrated into the sacrococcygeal ligament. Larger volumes of cysts also have some relationship with the vaginal wall and pelvic wall vessels and are prone to intractable hemorrhage during surgery. The area around the presacral cyst may involve the gynecological system, the urinary system, the digestive system, and the osteo-soft vascular system, and it is also difficult to have an in-depth surgical operation if the operator is not familiar with pelvic anatomy. 3. Pathological characteristics of presacral cyst. Although the cyst wall of presacral cyst adheres to the rectal wall or blood vessels or vaginal wall, the majority of presacral cysts are benign lesions and the scope of resection is limited. 4.The influence of medical inertia thinking and current medical environment on the operator. The clinical inertia thinking is that benign lesions are generally excised only as far as possible, without other tissue damage and affecting other organ functions. Therefore, when an anterior sacral cyst is tightly adherent to the bowel wall or blood vessels or vaginal wall, it is not easy to separate the bowel wall from the cyst wall in the extremely narrow pelvic surgical field, or it may not be separated at all. Under the dominant medical thinking —- that “the disease is benign and the intestinal wall cannot be damaged or removed”, part of the cyst wall may remain in the intestinal wall. Especially in the current situation where the doctor-patient relationship is relatively tense, it aggravates the concept that “the disease is benign and it is better to leave the cystic wall than to damage the intestinal wall”, otherwise medical disputes may arise after surgery. A patient with presacral cyst in the gynecology department was once consulted for surgery, and it was found that the cyst wall adhered closely to the sacrococcygeal and rectal walls and was difficult to be separated. However, one of the patient’s relatives (a county and township health worker) thought that the cyst surgery was simple, that the scope of surgery should not be too large, and that the cyst wall could be left behind. She did not know that it was the knowledge of these specialists that led to “the postoperative drainage tube of the presacral cyst could not be removed”. We also discussed with some experts about the removal of presacral cysts, and some experts thought that the residual wall of presacral cysts was because they were worried about the breakage of intestinal wall separation and medical disputes. The residual cyst wall was given electric burning or anhydrous alcohol palliative treatment during the operation, which was proved to be ineffective in clinical practice. 5.The operator does not have foresight on the possible results of presacral cyst surgery. There are many medical outcomes that are not foreseeable. Therefore, as mentioned earlier, medicine itself is largely a practical, empirical science, and it is sometimes difficult to reach a deep understanding if one has not experienced it. If one has not treated an anterior sacral cyst before, it is difficult to foresee that “if there is residue in the wall of the anterior sacral cyst, the cyst will easily recur and secrete mucus, making it difficult to remove the drainage tube. I think if the operator has foresight on the treatment of the disease before surgery, the wall of the presacral cyst should be cleaned anyway, otherwise, the surgery should be abandoned. The awareness of this disease is because there was once a foreign patient who recurred after the first operation in the local hospital, and the boundary of the cyst was still clear, and still recurred after performing two operations in our hospital, and the patient was in pain, and finally healed after having to expand the scope to remove part of the intestinal wall. By summing up the treatment experience and lessons of this patient and repeatedly thinking about it, I think that if the cyst wall adheres to the rectal wall, the cyst wall must be separated completely, rather than removing part of the intestinal wall and performing colonic preventive fistula, the cyst wall cannot be left behind, otherwise, there will be endless problems. I resected nearly 20 cases of presacral cysts, and none of them recurred. 6.Lack of effective communication with patients. Although the disease is benign, it must be fully communicated with patients and their families to recognize and understand the peculiarities of the disease. If the cyst wall is difficult to be stripped, or if the intestinal canal is ulcerated, colonic prophylactic fistula should be performed, or partial bowel wall resection should be performed if necessary. Patients and their families should be able to accept it after full understanding. I have operated nearly 20 cases of presacral cysts to fully illustrate this point.