Background: Asymptomatic bacteriuria is the presence of bacteria in the properly collected urine of a patient that has no signs or symptoms of a urinary tract infection. Asymptomatic bacteriuria is very common in clinical practice, Sterile pyuria definition: is a type of pyuria in which no bacteria are present in the urine. This could be due to a medical condition, non-detected bacteria, or another germ, such as a virus, The criteria for diagnosing UTI in patients with renal insufficiency are similar to those used in patients with normal renal function. Some clinical characteristics should be addressed. However, in febrile patients, where renal involvement cannot be excluded (pyelitis, pyelonephritis), blood and urine analysis as well as microbiological cultures should be performed first. The treatment strategies of UTI in renal insufficiency are mainly based on the same principals as for patients with normal renal function. UTI should respond rapidly, without recurrence, and no rise of resistant pathogens. Acute and chronic kidney diseases affect glomerular blood flow and filtration, tubular secretion and reabsorption, bioactivation and metabolism of antibiotics. Drug absorption, bioavailability, protein binding, distribution volume, and nonrenal clearance (metabolism) can be altered in CKD especially in hemo- and peritoneal dialysis. Apart from recommendations how dosing of antibiotics should be adapted in CKD and HD patients, drug dosing errors increase the risk of side effects and poor outcome.