Diarrhea that lasts for a week may be caused by acute gastroenteritis, or it may be caused by Crohn’s disease, or it may be caused by ulcerative colitis. 1. Acute gastroenteritis: patients with acute gastroenteritis may experience diarrhea lasting a week, which is a disease caused by viral or bacterial infection, and patients may also experience nausea, vomiting, abdominal pain, fever, chills and other symptoms. 2. Crohn’s disease: Crohn’s disease is a chronic inflammatory granulomatous disease, which can also lead to diarrhea for a week, abdominal pain, weight loss, fever, malaise, oral mucosal ulcers, skin erythema nodosum and other symptoms. 3. Ulcerative colitis: ulcerative colitis is a disease associated with intestinal microecological disorders, intestinal immune imbalance, intestinal mucosal barrier damage, the disease can also lead to symptoms of diarrhea lasting a week, the patient may also experience abdominal pain, abdominal distension, abdominal pain, after a heavy, mucus pus and blood. In addition to the above diseases, other factors can also lead to the symptoms of diarrhea lasting for a week, it is recommended to consult a doctor in time to find out the cause, so as not to delay the condition.