Pyelonephritis can affect the body in several different ways, depending on the severity of the case. Bacterial infection in the kidneys can irritate the urinary tract and may cause the ureters to spasm. This extremely painful condition is known as renal colic.
Pyelonephritis may also cause one or both kidneys to swell and become painful. Infection impairs the kidneys' ability to filter waste products out of the blood, and a build up of toxins in the blood will lead to fever, vomiting, and nausea. Infected kidneys may also deposit bacteria back into the blood, resulting in a form of blood poisoning known as sepsis. Over time, pyelonephritis can cause permanent damage to the kidneys and may result in chronic infection. If repeated infections arise as a result of kidney stones, it could lead to a form of chronic pyelonephritis that causes painful scarring and abscesses in the kidneys.
Pregnancy places additional strain on the urinary tract and increases a woman's risk of contracting pyelonephritis. A serious kidney infection raises the risk giving birth to an underweight baby.