Could You Fill 'Er Up, Please?

The prevalence of kidney disease is increasing in the HIV population, which is good news and bad. The good news is that patients are living longer, but the bad news is that as HIVers age, they're at increased risk for declining kidney function just as the general population is. Unfortunately, there's additional bad news; the risk factors for kidney disease are more prevalent among HIVers. Hypertension and diabetes account for about 85% of the kidney disease in the general population. Depending on the study cited, hypertension is found in 10% to 20% of HIV patients and diabetes in 2.5% to 14%. Another risk factor for kidney damage is elevated lipid levels, a problem well-known by people with HIV. Even higher risk is found in HIVers with low CD4 counts, high viral loads, hepatitis C coinfection, or cardiac or vascular disease. It is also more common in people with a family history of kidney disease and in people of African descent. Nephropathy, the leading cause of end-stage renal disease among HIVers, requires dialysis, and 88% of patients who have it are black. But since this disease is the result of HIV's attack on the kidneys, the introduction of combination therapy in 1996 has reduced the incidence of end-stage renal disease. The initial screen for kidney disease is relatively simple: a standard urinalysis and a basic blood test. If no protein is found in the urine and the calculation of kidney function, called a glomerular filtration rate, is normal (based on a formula using the serum creatinine), then no further testing is needed. These measurements should be repeated annually, especially in patients with the higher risk factors mentioned above. If urine protein is present or the GFR is low, further quantification of urinary protein loss, renal ultrasound, and a possible nephrology consult for kidney biopsy would be the next steps. If kidney disease is found, it is important to control blood sugars and lipids. Blood pressure should be treated to maintain readings below 125/85, preferably with either of two standard classes of antihypertensive medications, called angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. Quitting smoking helps too. Anti-HIV medications might not need much adjusting. Generally, nonnukes and protease inhibitors can remain unchanged, since they are large molecules, tightly protein-bound, and primarily liver-metabolized. Nukes, though, are excreted through the kidneys, so adjustments need to be made, especially for drugs with significant dose-dependent toxicities such as d4T and ddI. Viread (tenofovir) is a nucleotide that can cause kidney damage if it accumulates in the kidney tubules. Since tenofovir is kidney-excreted, declining kidney function can lead to higher tenofovir levels. Therefore, it is important to monitor kidney function regularly in patients on tenofovir. To date, all randomized double-blind studies with tenofovir show similar kidney safety compared to other compounds. As the awareness and importance of monitoring for declining kidney function leads to more diagnosis, we may see a rise in the incidence of kidney disease in HIV patients. But with early screening comes early treatment and the prevention of end-stage renal disease. This scenario may be similar to the late 1990s when lipid levels began to rise after the introduction of combination therapy and then an increase in cardiovascular events was noted. Once aggressive lipid control became the standard of care, the incidence of cardiovascular events stabilized. So I see lots of hydration in your future. 'Could you give me a urine sample, please?' Bowers is board-certified in family practice and is a senior partner with Pacific Oaks Medical Group, one of the largest U.S. practices devoted to HIV care. E-mail him at dan@hivplusmag.com.