Pyelonephritis is actually a type of urinary tract infection, which can be divided into pyelonephritis and cystitis. If the bacteria are confined to the bladder without other symptoms, it is called cystitis. At this time, anti-infection treatment is needed, and recovery can usually be achieved within about three to seven days. However, if cystitis is not treated in time, causing the bacteria to enter the kidney along the urinary tract, the patient may develop systemic fever, sometimes high fever from 38°C to 39°C, and may also experience kidney percussion pain, back pain, etc. This condition is called acute pyelonephritis, and its anti-infection treatment course requires two weeks. If the treatment course is insufficient, it is very easy to relapse. Currently, for the diet of pyelonephritis, it is important to maintain a low-salt, low-fat, light diet, avoid spicy, stimulating, cold food, drink more water, and urinate frequently.