Fgure 1

In Figure 1 on page 244 of the article "Laboratory evaluation of kidney disease" in the May 2011 issue, a marker pointing to the distal tubule was incorrectly placed. The corrected figure is shown below. We regret any confusion this error may have caused.

• Glomerulus: Filtration of blood
• Proximal convoluted tubule: Bulk (about 65%) of reabsorption of filtered water and solutes
• Descending thin limb of loop of Henle: Water reabsorption (about 20%) and production of concentrated ultrafiltrate
• Ascending thin limb of loop of Henle: Impermeable to water
• Ascending thick limb of loop of Henle: Reabsorption of sodium, potassium, and chloride; dilution of tubule fluid; generation of medullary hypertonicity
• Juxtaglomerular apparatus: Regulation of systemic blood pressure and GFR
• Distal convoluted tubule: Reabsorption of sodium, chloride, and divalent cations; dilution of tubule fluid
• Cortical collecting duct: Function similar to distal tubule's; regulation of acid-base balance (hydrogen and bicarbonate); regulation of sodium and potassium
• Medullary collecting duct: Final control of urine concentration via antidiuretic hormone; regulation of acid-base balance (hydrogen and bicarbonate)

*References: Verlander JW. Glomerular filtration. In: Cunningham JG, ed. Textbook of veterinary physiology. 3rd ed. Philadelphia, Pa: W.B. Saunders Company, 2002;431; and Guyton AC, Hall JE. Urine formation by the kidneys: I. Glomerular filtration, renal blood flow, and their control. Textbook of medical physiology. 10th ed. Philadelphia, Pa: W.B. Saunders Company, 2000;282.