Pyelonephritis is a kidney infection, usually from bacteria that have spread from the bladder. The possible causes of the pyelonephritis includes infection in the bladder, use of catheter to drain urine from the bladder, surgery on the urinary tract, condition such as enlarged prostate and renal calculi. The symptoms are inflammation of the kidney and upper urinary tract, fever, chills, burning or frequent urination, aching pain on one or both sides of the lower back or abdomen, cloudy or bloody urine and fatigue. The patient may also have nausea, vomiting and diarrhoea. The flank pain may be extreme. The symptoms of chronic pyelonephritis includes weakness, loss of appetite, hypertention, anaemia, protein and blood in the urine. Feeling of discomfortness during urination. If the pyelonephritis is left untreated or unresolved it can progress to a chronic condition that lasts for months or years, leading to scarring and possible loss of kidney function (Renal Failure).