Whether a 3mm*4mm kidney stone can be removed by itself cannot be generalized. Due to the individual differences of patients, as well as the morphology of the stone and other factors, whether the stone can be discharged on its own should be analyzed on a case-by-case basis. First of all, the self-discharge rate of urinary stones is relatively high, if the stone is ≤4mm, its self-discharge rate is about 80%. Generally speaking, if the stone cannot be eliminated by itself, it can be eliminated by drinking more water. Patients can shorten the average retention time of free crystalline stone particles in the urinary tract by drinking large amounts of water, thus promoting the self-excretion of small stones. The daily water intake standard is more than 2000ml of urine per day, until the urine is bright and colorless. To summarize, if you suffer from kidney stones, you should consult a doctor in time.