Of the various lesions affecting the urinary tract in the adult, chronic pyelonephritis furnishes the greatest problem to the urologist. In a discussion of this disease it should be recognized that the cases should be divided into several definite clinical groups. Acute and subacute forms of pyelonephritis should not be confused with chronic bilateral pyelonephritis, since they are self-limiting and often unilateral.
A common type of chronic urinary infection is characterized by recurring attacks of acute pyelonephritis accompanied by a febrile reaction, which subsides after several days, although frequency may persist for several weeks. When patients are examined in intervals between attacks they are usually free from any evidence of urinary infection, and cystoscopic examination and urine cultures may be negative. Such a negative phase may exist for months, to be followed by a recurrence in the acute form. Following removal of all foci of infection and after the development