Complete Endoscopic Submucosal Dissection of a Giant Rectal Villous Adenocarcinoma with Electrolyte Depletion Syndrome

An 81-year-old female consulted a local physician due to diarrhea. Since general fatigue and body weight loss were observed, she was admitted for detailed examination and treatment. Colonoscopy revealed a circumferential giant tumor with a maximum diameter of 10 cm in the rectum, and biopsy findings indicated villous adenoma. The tumor secreted a large amount of mucus, and a diagnosis of electrolyte depletion syndrome causing electrolyte disorders was made. We performed endoscopic submucosal dissection (ESD) as a less invasive procedure. The tumor was so big that the procedure had to be completed in two separate steps and it took 1,381 min in total. The tumor was histologically diagnosed as well-differentiated adenocarcinoma in high-grade adenoma located in the lower to upper rectum, invading into the mucosa without lymphatic or venous invasion. The stump of the resected specimen was negative for adenocarcinoma, however the horizontal stump was positive for adenoma. We administered steroid suppositories to prevent stenosis. After ESD, general fatigue and diarrhea disappeared and electrolyte disorders resolved. The patient had good clinical outcome without recurrence or stenosis.