Back or flank pain is one of the most common symptoms of the spread of pyelonephritis infection to the kidney. Other physical symptoms of kidney infection include a general malaise, vomiting, nausea, fever or chills, and confusion, particularly in elderly patients, as stated by WebMD.
In addition to the physical symptoms, patients with a kidney infection may also have urine that is cloudy, has an unpleasant odor or contains blood. The need to urinate may occur more frequently, and urination may be painful, according to WebMD.
Most of the cases of pyelonephritis that spread to the kidney result from complications of typical bladder infections. Bacteria leave the urethra and bladder, entering the kidneys through the ureters. In most cases, antibiotics cure the infection, notes WebMD.