Hydronephrosis can be categorized into mild and severe. Mild hydronephrosis usually does not cause nausea, while severe hydronephrosis may cause nausea. When patients have mild hydronephrosis, it usually does not cause obvious stimulation to the body, in this case, the possibility of nausea is relatively low, patients may have symptoms such as frequent urination, urgency as well as pain in urination, and usually does not have nausea. Patients with severe hydronephrosis may cause compression of the surrounding tissues, but also secondary urinary tract infection, causing damage to kidney function, which can lead to elevated blood creatinine, when patients may experience nausea, vomiting and other symptoms. Patients with hydronephrosis should go to regular hospitals in time, and follow the doctor’s instructions to choose the appropriate method of treatment, so as to avoid delaying the condition.