The kidneys secrete hormones, reabsorb substances, convert vitamin D to its active form, keep the right amount of bases and acids in the blood and remove wastes. One waste product that must be excreted is urea. Ammonia, from the metabolism of protein, is changed into urea and sent to the kidneys for excretion. In patients with polycystic kidneys, which do not function well, the kidneys may not be able to excrete enough urea, which then will accumulate in the bloodstream and can harm the brain.
Identification
Autosomal dominant polycystic kidney disease is a hereditary disease that affects an estimated 500,000 people in the U.S., with 2,000 people starting dialysis every year, according to Qi Qian, M.D., Assistant Professor at the Mayo Clinic School of Medicine, in "Current Diagnosis & Treatment: Nephrology & Hypertension." Most people with this kidney disease have a mutation in the PKD1 gene or in the PKD2 gene. They will develop multiple cysts in both of their kidneys and might also develop aneurysms, cysts in the liver and pancreas, and various heart abnormalities. An aneurysm is an area in an artery that because of its weakness has become too wide.
Development
The gene mutations result in proteins that do not properly function in the kidneys, as explained in The Merck Manual for Healthcare Professionals, by Drew Cutler, M.D., Associate Professor of Pediatrics at the Loma Linda University School of Medicine. Urine is formed inside structures called tubules, but because of the abnormal proteins, the tubules get too large, fill up with fluid, separate and form cysts. Scientists hypothesize that the abnormal proteins somehow change how the cells that form the lining of the tubules hold together and change how well they can detect how fast fluid flows.
Symptoms
People with the PKD1 gene mutation have a more severe form of the disease, with renal failure at an average age of 54. Those with the PKD2 mutation usually do not have renal failure until approximately age 74. People with both mutations experience pain, high blood pressure and blood in their urine as the cysts develop and the kidneys get larger. The symptoms usually do not start until adulthood. Some patients may also develop nephrolithiasis, or kidney stones, as well as urinary tract infections.
Evaluation
The diagnosis of autosomal dominant polycystic kidney disease may be made when doctors are trying to determine why someone has high blood pressure, a kidney infection or blood in his urine. Many times, the physician will be able to feel the enlarged kidneys. A urinalysis may show white blood cells and red blood cells in the urine. Blood chemistry tests will show that the kidneys are not functioning normally, while an ultrasound, CT scan or X-ray will show the large kidneys.
Recommendations
Qian writes that no treatment can stop the development of this kidney disease or make the cysts go away. But he recommends a diet that is high in fiber and low in cholesterol and sodium, and includes no more than 0.8 grams of protein for each kilogram of body weight every day.
References
- "Current Diagnosis & Treatment: Nephrology & Hypertension"; Edgar Lerma, M.D., Jeffrey Berns, M.D., and Allen Nissenson, M.D.; 2009
- "Smith's General Urology"; Emil Tanagho, M.D., and Jack McAninch, M.D.; 2008
- The Merck Manual for Healthcare Professionals: Autosomal Dominant Polycystic Kidney Disease
