Final answer:
Pyelonephritis and cystitis differ in terms of location of the infection. Pyelonephritis affects the kidneys, while cystitis affects the bladder.
Step-by-step explanation:
Pyelonephritis and cystitis are both urinary tract infections, but they differ in terms of location of the infection. Pyelonephritis is an infection of one or both of the kidneys, while cystitis is an infection of the bladder. The symptoms of pyelonephritis and cystitis can also differ, with pyelonephritis often causing back pain, fever, and nausea, while cystitis typically causes pain and frequent urination.