Overview of Chronic Kidney Disease

Peter L. Salgo, MD: Hello, everybody. We’re going to be discussing the link between chronic kidney disease [CKD] and anemia. We’re going to take a look at some of the commonly held beliefs about this, including some misconceptions in the clinical community, and we’re going to discuss the opportunities for emerging agents to join the current treatment armamentarium. Frankly, only doctors say armamentarium.

I’m Dr Peter Salgo. I’m a professor of medicine and anesthesiology at Columbia University [Vagelos College of Physicians and Surgeons]. I’m joined by distinguished faculty. What I’d like you guys to do is introduce yourselves. Dan, do you want to start? Tell us who you are.

Daniel W. Coyne, MD: I’m Dr Daniel Coyne. I’m at [the] Washington University [School of Medicine] in St. Louis. I’m a professor of medicine here, and I’m the director in the renal division of our academic dialysis unit and our renal outpatient offices, including our infusion center.

Peter L. Salgo, MD: OK. Now we’ve got Dr Provenzano. Robert?

Robert Provenzano, MD, FACP, FASN: Hi, I’m Bob Provenzano from Detroit: the Wayne State University School of Medicine and Ascension Health. My focus in my career has been on anemia and ESRD [end-stage renal disease] as well as CKD.

Peter L. Salgo, MD: All right. We have Dr Crittenden. You’re joining us from the left coast. Tell us a bit about yourself.

Stanley Crittenden, MD: Good morning. I’m Dr Stanley Crittenden from Los Angeles. I’m with Anthem Blue Cross Blue Shield’s diversified business group. I specifically run CareMore’s end-stage renal disease chronic special needs plans.

Peter L. Salgo, MD: Thank you all for joining us. It’s going to be interesting. I know it’s going to be interesting, because look at our faculty. It’s going to be terrific. Why don’t we start with some of the basics. Let’s talk about chronic kidney disease. Who wants to set the groundwork here? What is it? How common is it? Is it something that even non-nephrologists have to deal with on a daily basis? Who wants to start?

Daniel W. Coyne, MD: I’ll start. It’s pretty darn common. Chronic kidney disease is the presence of a decrease in kidney function for 90 days or more. It’s usually accompanied by some protein or blood in the urine. If you look at the CDC [Centers for Disease Control and Prevention] review of this, they estimate that about 1 of 7 adults has chronic kidney disease.

Peter L. Salgo, MD: Wait, can you stop there for a minute, because that number is astoundingly big.

Daniel W. Coyne, MD: Yes.

Peter L. Salgo, MD: I’ve been in the business for a long time, and I was not aware that it’s one-seventh of the American population. That’s enormous.

Daniel W. Coyne, MD: They think that 37 million Americans have chronic kidney disease. When you take the adult population, and it overwhelmingly is that population, that comes out to 1 of 7. Some of these are diabetics who have proteinuria and retain kidney function. On a blood test, they would not typically be classified as having chronic kidney disease because their creatinine is still normal, but it’s a huge problem. The most interesting thing about the CDC data is that they estimate, based on publications, that 9 of 10 Americans don’t know they have chronic kidney disease.

Peter L. Salgo, MD: Nine of 10 of those 1 of 7?

Daniel W. Coyne, MD: Yes.

Peter L. Salgo, MD: All right. That being said, is there a common pathway here? What is the pathophysiology of chronic kidney disease? If so many people have it, what’s going on? Why?

Robert Provenzano, MD, FACP, FASN: Let me start off and build on what Dan has said. Part of the reason for these increased numbers, as many primary care doctors know, is the increased prevalence of hypertension, diabetes, and obesity. When we talk about the pathophysiology of chronic kidney disease, it’s important to focus on how we categorize it. For both clinical and research purposes, chronic kidney disease is classified into 5 stages. Stage I is when your renal function is still greater than about 90%, but there’s evidence of kidney disease—to Dan’s point, either blood or protein in the urine. The stages then increase until you get to stage V, which is less than 15% renal function.

There are problems associated with the physiology here: its comorbid conditions that occur. In other words, as your renal function decreases, the more likely you are to have diabetes. You develop metabolic bone disease because of the inability to excrete phosphorus. You get hypertension, you retain fluid, and those comorbidities result in a lot of the problems we see with chronic kidney disease. To Dan’s point, when it’s asymptomatic early on, it’s often impossible to identify unless a primary care doctor is keeping a close eye on you.

Peter L. Salgo, MD: When you’re talking about this progression to chronic kidney disease and eventual dialysis, is there a common timeline? Do we know how long it takes from the development of proteinuria all the way to dialysis?

Robert Provenzano, MD, FACP, FASN: I’m going to ask Dan to chime in too. The problem with that is that it depends on the management. We know that, once you hit certain stages, the probability of advancing is greater. For example, if you’re in stage III or late stage III, the probability that you will progress is very high. How you progress is predicated on identifying that you have chronic kidney disease, treating the comorbid factors, keeping your blood sugar and your blood pressure tightly controlled, staying on the proper diet, etc. For a nephrologist, once you hit that stage, we begin to start addressing the therapies aggressively. Dan, I don’t know if you want to add to that.

Daniel W. Coyne, MD: I would add 1 more issue about the high incidence of CKD, and that’s age. It’s clear now that once you get over the age of 40 years, we start to lose GFR [glomerular filtration rate]. Given the very high population of patients in their 80s and higher, we see people with CKD simply because they’re old. For a long time, we waved our hands at that and said it’s not that big of an issue, but it looks as if it’s an accelerator for all these other comorbidities, such as having cardiovascular disease and being more prone to getting heart failure and things like that.

Peter L. Salgo, MD: I was looking at the numbers. The fastest-growing segment of the American population is over 40 years old. Of that cohort, the fastest growing is over 80 years old. We’re almost a victim of our own success here.

Daniel W. Coyne, MD: We’re dealing with this a lot. To answer your question about progression and what the unifying factor is, whether it’s diabetes damaging the glomeruli, some tubulointerstitial diseases, or all of this is inflammation within the kidney, it sets up this kind of chronic progression, which our treatments, as Bob mentioned, help slow down. However, it’s disease specific how quickly people go down.