because of low levels of lactase in the small intestine due to either reduced enzyme expression, mucosal injury, or congenital absence.

Lactose intolerance is genetically determined and occurs in 5%-10% of European Caucasians, 60% of Ashkenazi Jews, and 70% of African Americans.

The efficiency of lactose digestion and absorption can be measured by giving 100 g of oral lactose, then measuring the blood glucose concentration at 30-minute intervals over 2 hours. Patients with lactose intolerance exhibit a rise in blood glucose of 20 mg/dL or less.

A lactose-free diet may be deficient in calcium, vitamin D, and riboflavin.

Most people with pyelonephritis do not have complications if appropriately treated with bacteria-fighting medications called antibiotics.

In rare cases, pyelonephritis may cause permanent kidney scars, which can lead to chronic kidney disease, high blood pressure, and kidney failure. These problems usually occur in people with a structural problem in the urinary tract, kidney disease from other causes, or repeated episodes of pyelonephritis.

Infection in the kidneys may spread to the bloodstream—a serious condition called sepsis—though this is also uncommon.