Patients with chronic nephritis have decreased urine output, which may be merely a physiological phenomenon due to decreased water intake of the patient, resulting in decreased urine output, or it may be a pathological state, which is divided into two cases. The first one is that patients with chronic nephritis have a large amount of urinary proteins, when there is a large amount of urinary proteins present, plasma albumin decreases, resulting in edema of the body, and a large amount of water enters into the interstitial space of tissues rather than into the kidneys, which leads to a decrease in the production of urine; the second one is that the further aggravation of the condition of chronic nephritis and its continuous deterioration have caused numerous renal tissues to be destroyed, resulting in renal failure, and the kidneys are unable to Effective production of urine, which leads to the situation of low urine production, patients need to do 24-hour urine protein quantification, as well as blood tests of renal function to clarify the cause.