A kidney infection, also known as pyelonephritis, is when bacteria or viruses cause problems in one or both of the kidneys. It is a type of urinary tract infection (UTI). They can be sudden or chronic, are often painful, and can be life-threatening if not treated promptly. Symptoms of kidney infection usually appear two days after infection and may vary, depending on age. Common symptoms include: pain in the abdomen, back, groin, or side; nausea or vomiting; frequent urination or the feeling that you have to urinate; burning or pain while urinating; pus or blood in your urine; bad-smelling or cloudy urine; chills; and/or a fever. Women are most commonly affected by kidney infection, as are pregnant mothers, children under 2 years of age, and individuals aged over 60 years. If you would like to find out more and receive a second opinion regarding your diagnosis and treatment, please contact us at secondopinions.com.