If the urine is very swollen but the volume of urine is very small, the possible causes are as follows: 1. Urinary tract infection, after infection, the mucosal epithelium of the urinary bladder is congested, edematous and sensitive, when a small amount of urine is stored, it can produce an obvious feeling of holding urine, but the volume of urine is not much when urinating, accompanied by symptoms such as urinary urgency, painful urination and lumbar pain, etc. It is necessary to carry out routine urine examination to clarify whether there is infection. 2. The reason is that stones stimulate the mucous membrane and lead to frequent contractions, so there is a feeling of frequent urination or holding urine, but the amount of urine is not much each time, accompanied by pain in the bladder area or pain in the abdomen, etc. Ultrasound examination of the urinary system is needed to rule out the presence of stones. 3. Excessive contraction of the bladder forceps muscle due to excitement, producing the corresponding symptoms. It is usually not accompanied by any symptoms of urination, and there is no sign of infection when routine urine examination is performed. Urodynamic examination is needed to further confirm the diagnosis.