The heart and kidneys are far more closely connected than we imagine. When one of the two organs begins to work poorly, the other can suffer as well. This is the principle behind cardiorenal syndrome, a complex condition in which heart failure and kidney disease can feed each other. Understanding this relationship means changing perspective on prevention: monitoring blood pressure, heart, kidney function and metabolism as parts of the same system.<\/strong><\/p>\n When we think of the heart, we picture a pump. When we think of the kidneys, we generally regard them as two filters. This is a simple picture and, in part, a correct one. But it does not tell the whole story of what happens in our body.<\/p>\n The heart and the kidneys are in constant dialogue.<\/p>\n The first sends blood to every organ, the kidneys included. The second regulate the amount of fluid, sodium and electrolytes in the body and take part in the complex system that controls blood pressure. How one works therefore affects how the other works.<\/p>\n As long as everything is working properly, we hardly notice this relationship. The problem emerges when one of the two organs runs into difficulty.<\/p>\n A heart that can no longer pump blood adequately can compromise kidney function. At the same time, chronic kidney disease can increase the load on the cardiovascular system and contribute to the onset or worsening of heart problems.<\/p>\n It is within this two-way relationship that cardiorenal syndrome<\/strong> fits.<\/p>\n The American Heart Association describes it as a spectrum of conditions in which acute or chronic dysfunction of the heart can cause acute or chronic dysfunction of the kidneys, and vice versa. It is therefore not simply the presence of two diseases at the same time, but an interaction in which the heart and kidney can influence each other through circulatory, neurohormonal, metabolic and inflammatory mechanisms.<\/p>\n Understanding this relationship is particularly important for people who suffer from hypertension, diabetes, chronic kidney disease or heart failure<\/strong>. These are very common conditions that often do not occur in isolation, but meet in the same patient.<\/p>\n And this is precisely where one of the great transformations of contemporary medicine comes from: no longer looking only at the single organ, but at the person as a whole.<\/p>\n Cardiorenal syndrome<\/strong> is not a single disease with one cause and an identical course for everyone.<\/p>\n It is rather a term used to describe different clinical situations that share one element: the deterioration of one organ contributes to the deterioration of the other.<\/p>\n Consider, for example, a person with heart failure.<\/p>\n When the heart loses part of its ability to pump blood effectively, the amount of blood reaching the organs can change. The kidneys sense this situation and set in motion a series of mechanisms aimed at preserving circulation.<\/p>\n Among other things, the body tends to retain sodium and water.<\/p>\n In the short term, this is a response that arises as a compensation. But if the situation persists, the increase in fluids can contribute to congestion, the appearance of edema and further overload on the heart.<\/p>\n This creates a difficult cycle:<\/p>\n the heart works less effectively, the kidneys react by retaining more fluid and sodium, the buildup of fluid increases the heart’s workload, and the problem can gradually worsen.<\/strong><\/p>\n But the relationship can also run in the opposite direction.<\/p>\n Chronic kidney disease can promote hypertension, disturbances of fluid and electrolyte balance, anemia, and metabolic and inflammatory changes that can have repercussions on the cardiovascular system.<\/p>\n For this reason, people today speak more and more of a true heart-kidney axis<\/strong>.<\/p>\n It is no coincidence that KDIGO, the leading international organization for kidney diseases, is developing its first guideline specifically dedicated to the management of heart failure in chronic kidney disease, underscoring the need for coordinated, multidisciplinary care between nephrologists and cardiologists.<\/p>\n To understand cardiorenal syndrome<\/strong>, we have to let go of the idea that the kidneys simply serve to produce urine.<\/p>\n Every day they receive an enormous amount of blood and carry out a sophisticated job of regulating the body’s internal environment.<\/p>\n They filter waste substances, regulate water and electrolytes, take part in controlling acid-base balance and play a fundamental role in regulating blood pressure.<\/p>\n This means that a reduction in kidney function can have consequences far broader than the simple rise in creatinine seen in blood tests.<\/p>\n When the kidneys gradually lose efficiency, it can become harder to eliminate sodium and water. Blood pressure can become more difficult to control, and changes can appear that increase stress on the cardiovascular system.<\/p>\n That is why a disease that seems to be “of the kidneys” can also turn into a heart problem.<\/p>\n The American Heart Association emphasizes that the interaction between cardiovascular and kidney disease involves not only circulation, but also atherosclerosis, neurohormonal activation, inflammatory processes, anemia and changes related to the progression of chronic kidney disease.<\/p>\n The kidney, in short, is not a mere bystander in cardiovascular health.<\/p>\n It is one of its main players.<\/p>\n The relationship works in reverse too.<\/p>\n The kidneys need to receive adequate blood flow to do their job properly. When the heart is in difficulty, circulatory conditions can change.<\/p>\n For many years, attention focused mainly on the reduction of blood reaching the kidneys. Today we know that the picture is more complex.<\/p>\n In heart failure, venous congestion<\/strong> can also become very important. In simple terms, what matters is not only how much blood the heart manages to push forward, but also what happens “upstream” when the circulatory system is congested.<\/p>\n The increase in venous pressures can also affect the kidneys, changing their filtering capacity.<\/p>\n On top of this comes the activation of hormonal and nervous systems that try to maintain blood pressure and organ perfusion. If this response becomes persistent, however, it can contribute to the progression of the problem.<\/p>\n It is one of the clearest examples of how a mechanism designed to protect us can, when it stays activated too long, become part of the disease.<\/p>\n Among the situations in which the heart-kidney relationship is most evident is heart failure<\/strong>.<\/p>\n Heart failure occurs when the heart cannot adequately meet the body’s needs, or can do so only at the cost of high filling pressures.<\/p>\n It does not necessarily mean that the heart has stopped working. It means that its ability to do its job is compromised.<\/p>\n Symptoms may be subtle at first.<\/p>\n A person may notice being more short of breath climbing stairs, feeling unusually tired, or finding that activities previously done without trouble now require more effort.<\/p>\n As the condition progresses, shortness of breath, reduced exercise tolerance, swelling of the ankles and legs, and weight gain linked to fluid retention<\/strong> may appear.<\/p>\n On NefroCenter we have already explored the early symptoms of heart failure<\/a>, precisely because recognizing certain changes early can encourage a timely evaluation.<\/p>\n In a patient with heart failure, however, monitoring only the heart is not enough.<\/p>\n Kidney function becomes an integral part of the clinical evaluation.<\/p>\n The traditional classification divides cardiorenal syndrome into five types<\/strong>, based on the organ where the problem mainly originates and on whether it is acute or chronic. This classification is useful mainly to specialists and does not mean that the boundaries are always so clear-cut in clinical practice.<\/p>\n In type 1<\/strong>, an acute heart problem, such as acute heart failure, causes a rapid worsening of kidney function.<\/p>\n In type 2<\/strong>, a chronic heart disease gradually contributes to kidney deterioration.<\/p>\n Type 3<\/strong> follows the opposite path: acute kidney injury has consequences for the heart.<\/p>\n In type 4<\/strong>, chronic kidney disease contributes over time to the development or worsening of cardiovascular disease.<\/p>\n Finally there is type 5<\/strong>, in which a systemic disease can affect both organs at the same time.<\/p>\n For the patient, however, the most important thing is not to memorize this classification.<\/p>\n It is to understand its principle: the first organ to become diseased is not necessarily the only one that needs to be monitored<\/strong>.<\/p>\n If we had to identify one of the most important links between cardiovascular and kidney health, we would certainly have to talk about blood pressure<\/strong>.<\/p>\n Hypertension is both a cause and a possible consequence of kidney damage.<\/p>\n Persistently high blood pressure puts stress over time on the small blood vessels in the kidneys. The progressive damage can reduce filtering capacity.<\/p>\n But when kidney function declines, blood pressure control can also become harder.<\/p>\n It is another cycle that can feed itself.<\/p>\n On the cardiovascular side, hypertension forces the heart to work against greater resistance. Over time it can promote structural changes in the heart muscle and contribute to the development of cardiovascular disease.<\/p>\n For this reason, controlling blood pressure means protecting the heart, kidneys, brain and arteries<\/strong> all at once.<\/p>\n We have explored this relationship in the NefroCenter guide on high blood pressure and the kidneys<\/a>. The relationship is particularly important because hypertension can remain without obvious symptoms for a long time while organ damage progresses.<\/p>\n The heart and kidneys cannot be separated from metabolism either.<\/p>\n Diabetes<\/strong> is one of the main examples.<\/p>\n Over time, high blood sugar can damage the small vessels of the kidneys and promote the onset of diabetic kidney disease. At the same time, diabetes is a major cardiovascular risk factor.<\/p>\n It is therefore not surprising that a person may have diabetes, hypertension, chronic kidney disease and cardiovascular disease all at once.<\/p>\n This very overlap has led in recent years to an even broader view.<\/p>\n The American Heart Association speaks of cardiovascular-kidney-metabolic health<\/strong>, emphasizing how metabolic changes, obesity, diabetes, kidney disease and cardiovascular disease are deeply interconnected.<\/p>\n It is not only a change of terminology.<\/p>\n It is a change in the way we think about prevention.<\/p>\n There is no single symptom that can by itself identify cardiorenal syndrome<\/strong>.<\/p>\n And this is precisely what makes diagnosis complex.<\/p>\n Fatigue, shortness of breath, swelling of the legs and ankles, changes in blood pressure and a reduced ability to be physically active can be present in heart failure.<\/p>\n Chronic kidney disease, on the other hand, can remain silent for a long time.<\/p>\n In more advanced stages, fatigue, edema, changes in urine output, nausea or other symptoms may appear, but these are not very specific and are not enough to make a diagnosis.<\/p>\n There is also an interesting problem: the heart and kidneys can produce similar symptoms<\/strong>.<\/p>\n Swelling of the legs, for example, can appear with fluid retention linked to heart failure, but it can also be seen in kidney conditions and in many other diseases.<\/p>\n For this reason, cardiorenal syndrome is not diagnosed on the basis of symptoms reported on the Internet.<\/p>\n The clinical picture has to be reconstructed.<\/p>\n Diagnosis comes from integrating several pieces of information.<\/p>\n To assess the kidneys, one of the best-known tests is serum creatinine<\/strong>. From its value, together with other individual information, the glomerular filtration rate, or eGFR<\/strong>, is estimated, which gives an indication of the kidneys’ filtering capacity.<\/p>\n But creatinine alone does not tell the whole story.<\/p>\n Urinalysis and, when indicated, measurement of albuminuria<\/strong> can reveal kidney damage even in people whose filtration rate does not yet appear severely compromised.<\/p>\n Sodium, potassium and other parameters may also be evaluated depending on the clinical situation and the medications being taken.<\/p>\n The information on the NefroCenter site about kidney function tests<\/a> explains the tests used to study how the kidneys are working.<\/p>\n On the cardiology side, the work-up may include an electrocardiogram, echocardiogram, Holter monitoring, blood tests and other examinations<\/strong> determined by the specialist.<\/p>\n The echocardiogram, in particular, makes it possible to observe the structure and function of the heart, while the electrocardiogram records its electrical activity.<\/p>\n Not everyone needs to have the same tests.<\/p>\n It is the overall picture \u2013 symptoms, age, blood pressure, diabetes, kidney function, cardiovascular history and medications \u2013 that guides the doctor.<\/p>\nCardiorenal syndrome: when the heart and kidneys share the same problem<\/h2>\n
Why are the kidneys so important for the heart too?<\/h2>\n
And why can a diseased heart damage the kidneys?<\/h2>\n
Heart failure and the kidneys: a particularly delicate relationship<\/h2>\n
Cardiorenal syndrome is not just one: there are five forms<\/h2>\n
Hypertension: the bridge between heart and kidneys<\/h2>\n
Diabetes also joins the dialogue between heart and kidneys<\/h2>\n
Cardiorenal syndrome: what are the symptoms?<\/h2>\n
What tests are needed to check the heart and kidneys?<\/h2>\n