The CDC warns that 15% of US adults are estimated to have chronic kidney disease (CKD). Even worse, half of the people with low kidney function who are not on dialysis do not know they have CKD. 1 in 3 American adults are at risk for CKD.

What do the kidneys do?

The kidneys are important in the removal of toxins from the body, as well as regulation of waste products such as creatinine, urea, and uric acid. They also play a role in regulating the amount of fluid outside of the cells in our body, amongst other things. The kidneys can also be impacted by medications. Diabetes, high blood pressure, infections, and kidney stones all affect the function of the kidneys. Because the kidneys filter the blood in our body, if they are impaired drug potency can be increased 

How do we test kidney function?

Testing kidney function generally revolves around assessing the glomerular filtration rate (GFR) or to check for proteinuria (abnormally high protein in urine). GFR is measured in milliliters per minute and measures the clearance of substances from the blood. 

What can creatinine and urea nitrogen, and what can they teach us about the kidneys?

Creatinine is a waste product that has a higher concentration in the blood when the kidneys filtration rate is diminished. Urea nitrogen is another waste product in the blood that your body produces. It is a result of the breakdown of protein, either from diet or metabolism, and has elevated levels during decreased kidney function. 

What are some common drugs prescribed to kidney patients?

Anti-hypertensive medication

These medications lower blood pressure. High blood pressure can damage the kidneys, heart, and blood vessels. Some of the most common blood pressure medications are Atenolol, Doxazosin, Irbesartan, and Ramipril. 

Diuretics

Diuretics are medicines which encourage the kidneys to produce more urine. Decreased urine output is correlated with swelling, difficulty breathing, and high blood pressure. 

Erythropoietin

Erythropoietin is the hormone that the kidney produces that causes bone marrow to make red blood cells. Those with kidney damage may be anemic (lack of red blood cells) and feel tired or weak. 

How do drugs interact with the kidneys?

Clinical Pharmacokinetics lists 5 ways that drugs interact with the kidneys:

1. Increased drug excretion via increased glomerular filtration rate
2. Decreased drug excretion due to “competition at tubular secretion site”
3. Increased drug excretion due to competition at the tubular reabsorption site.
4. increased/decreased drug excretion due to change in pH of urine. Change in the flow of urine can also increase or decrease drug excretion
5. Inhibition of renal drug metabolism

What causes kidney damage?

Two of the most common causes of Chronic Kidney Disease (CKD) are diabetes and hypertension. CKD develops over a long period of time, compared to Acute Kidney Injury (AKI) which is a sudden development of kidney failure within hours or days. The National Kidney Foundation lists decreased blood flow, direct damage to the kidneys, and blockage of the urinary tract as the 3 main causes of AKI. The kidneys are excellent at adapting to the loss of function, so people may not show or notice any symptoms until the kidneys have exceeded the capacity to cope with damage.

What are the symptoms of kidney damage?      

Decreased urine output                                           

Irregular heartbeat                                                       

Nausea

Chest pain/pressure

Fatigue

Swelling of legs, feet, or ankles 

How does kidney damage change how drugs are processed?

The ability for the kidneys to excrete a drug are dependent on these factors; blood flow through the kidney, condition of the kidneys, and urine flow. Most drugs follow a pathway of elimination that involves the kidneys. Most things that are excreted in the urine, which means that drug dosing depends on kidney function. If the kidneys are damaged, then a lower dose of a drug may be necessary.

What now?

In conclusion, the kidneys are an extremely important organ, and CKD remains one of the most underdiagnosed and misrepresented diseases in the United States. If those who are at risk of developing chronic kidney disease took proactive measures for prevention, then much heartache and financial expense could be spared.