In the early morning of one day in June 2008, Ms. Li, who lived in Xuhui District of the city, just got up and suddenly felt the sky spinning, fell to the ground in front of her eyes, and luckily her daughter was at home that day and called for help in a hurry. In the hospital emergency room, doctors quickly resuscitated Ms. Li, and she woke up half an hour later. The doctor performed a series of tests on her, and strangely enough everything else seemed normal, but only found that Ms. Li had severe hypokalemia, with a blood potassium concentration of only 1.2 mmol/L (normal 3.5 or more). However, it was unclear what caused the hypokalemia. Ms. Li is 56 years old. From half a year ago, Ms. Li’s stools started to become diluted, starting with 3-4 times a day, and finally developed into watery diarrhea, with occasional abdominal pain and blood in the stool, and she soon lost weight. The symptoms were further aggravated by general weakness, panic and chest discomfort, and depression. This time after resuscitation out of danger. When looking for the cause, the internal medicine doctor said that the diarrhea led to serious electrolyte disorder, which caused a series of clinical symptoms, and the hospital even issued 2 consecutive critical care orders due to the severity of the clinical symptoms. The internal medicine doctor gave Ms. Li symptomatic rehydration treatment, but the clinical diarrhea and hypokalemia could not be relieved. The doctor also suspected that there was a problem with the patient’s endocrine system, however, all the endocrine indicators were checked to be normal. The family took Ms. Li to two hospitals in Shanghai for medical treatment, one of which gave the patient an anal finger examination and found that a rectal mass could be palpated only 2 cm away from the anal verge, extending upward without being able to feel the edge, with a soft texture. Subsequent colonoscopy of the patient revealed a large mass of 20 cm in diameter starting in the lower rectum and continuing to the sigmoid colon. The clinical diagnosis was considered: rectal villous adenoma with malignancy pending exclusion. However, the experts told them that due to the proximity to the anus and the large size of the tumor, the anus would have to be excavated for surgery, and the current multiple biopsies have turned out to be benign, and excavation of the anus has the potential to cause disputes. Therefore, the doctor asked the patient to go to a notary public before the surgery. People around her have told Ms. Li that if the surgery is performed, she will have to carry an artificial anal pouch for life, which will have a great impact on her daily life in the future, and Ms. Li firmly refused to be admitted to the hospital for treatment. Ms. Li and her family were resigned. The lovers suddenly remembered that their old comrade was now the leader of Xinhua Hospital, so they called for help. The old comrade told him that Xinhua Hospital had introduced a new anorectal surgery specialist, so come to our hospital. The family came to Xinhua Hospital’s Department of Anal Surgery with the examination report. The director of the Department of Anal Surgery, Cui Long, combined the medical history, clinical symptoms and auxiliary examination results and considered that the hypokalemia was caused by a huge rectal choroidal adenoma. It turned out that the patient had persistent hypokalemia because the choroidal adenoma itself could cause constant diarrhea and large amount of potassium excretion; and because hypokalemia could trigger a decrease in heart function and even cardiac arrest, which could be life-threatening, it was no wonder that the hospital issued a critical care notice. After a comprehensive consideration and a surgical plan, Director Cui Long told them that there is a newest surgery called “extreme” anal preservation, which can preserve the anus and is very suitable for Ms. Li’s condition. On July 10, 2008, Director Cui performed an anastomosis surgery on Ms. Li to save the anus and remove the rectal tumor, which had grown to 20 centimeters and had a diameter of one week around the intestinal cavity, and the postoperative pathology confirmed that the rectal giant villous adenoma. After the surgery, Ms. Li’s blood potassium soon returned to normal, and she recovered well in other aspects, and her clinical diarrhea then subsided and gradually returned to normal bowel movements. More than a year has passed, and Ms. Li now has 1-2 bowel movements per day, and the sunshine of her life has returned to a brilliant glow. With the continuous development of surgical techniques, various anal preservation techniques have come into being. Now, on the premise of ensuring the effect of radical treatment, many low rectal tumors that used to be removed from the anus can preserve the anus, which is indeed a blessing for patients. In conclusion, due to the understanding of biological behavior of rectal cancer, the improvement of surgical skills and the improvement of surgical instruments, more and more anus-preserving surgeries are applied in clinical practice, and some patients avoid anus removal, which improves the patients’ quality of life and brings good news to the majority of rectal cancer patients.