Regional variations in the incidence of upper urinary tract stones in England and Wales.

Data from the Hospital In-patient Enquiry were used to define the regional patterns of hospital discharge rates for upper urinary tract stones and renal colic in England and Wales. By combining the rates for stones and colic, and by distinguishing emergency from planned admissions, the biases produced by repeated admissions of the same patient and by regional variations in diagnosis and coding may be reduced. There are regional variations in incidence of upper urinary tract stones: Wales and the southern regions of England have a generally higher incidence than northern regions. These variations may be related to regional differences in diet or occupation; or they may partly depend on associations between stone incidence and atmospheric temperature, exposure to ultraviolet irradiation, and hardness of drinking water.