The possible reasons for the foul smell in urine are as follows: first, urinary tract infection, the presence of more bacteria in the urine after the infection, decomposition of some components of the urine and produce ammonia substances, and therefore produce a fishy and smelly smell. If there is a purulent infection, there is more pus in the urine, there can also be an abnormal odor, accompanied by frequent urination, urinary urgency, painful urination, serious patients can also be accompanied by back pain, fever and other symptoms, need to carry out routine urine examination and urine culture test to further identify. Secondly, patients with long-term urinary retention and difficulty in urination, or patients who drink less water and sweat more resulting in over-concentration of urine, can have urine breakdown. When urine stays in the bladder for more than three hours, it will become concentrated to varying degrees and its internal components decompose, which can then appear with an abnormal foul odor, usually not accompanied by obvious urinary frequency, urinary urgency and painful sensation in the urethra, which requires routine urine examination for further identification. Thirdly, in patients with diabetic ketoacidosis, an abnormal odor can appear when urinating, accompanied by an increase in urine sugar level, a large number of ketone bodies in the urine, combined with infection, and an increase in the number of white blood cells.