Abstract and Introduction
Renal dysfunction is one of the strongest predictors of outcome in heart failure. Several studies have revealed that both reduced perfusion and increased congestion (and central venous pressure) contribute to worsening renal function in heart failure. This paper proposes a novel factor in the link between cardiac and renal dysfunction: "renal tamponade" or compression of renal structures caused by the limited space for expansion. This space can be limited either by the rigid renal capsule that encloses the renal interstitial tissue or by the layer of fat around the kidneys or by the peritoneal space exerting pressure on the retroperitoneal kidneys. Renal decapsulation in animal models of heart failure and acute renal ischemia has been shown effective in alleviating pressure-related injury within the kidney itself, thus supporting this concept and making it a potentially interesting novel treatment in heart failure.
The kidney plays a central role in heart failure (HF), and several large studies have shown that renal dysfunction is one of the most powerful predictors of outcome in HF.[1,2] Already in 1990 it was demonstrated that the kidney is very sensitive to changes in perfusion. When cardiac index decreases by 25%, renal blood flow decreases by as much as 50%. Later, several groups showed that reduced renal perfusion is among the strongest determinants of glomerular filtration rate (GFR) in HF.[4–6] Further studies in this field revealed that not only reduced renal perfusion but also, importantly, increased central venous pressure contribute to a decrease in renal function.[7,8] Ever since, several studies have investigated the associations between clinical factors and renal congestion. Yet, the area of cardiorenal interplay remains complex.
In the present paper, we discuss the 3 mechanisms that, individually or combined, may lead to renal congestion as a result of intrarenal or extrarenal compression. Another (classic) example of renal injury as a result of compression can be found in the Page kidney: a clinical syndrome of diminished renal function and/or hypertension as a result of external compression on the kidney, most commonly subcapsular hematoma. The fact that the kidney is surrounded by a rigid and nonexpandable capsule plays a crucial role in the Page kidney and in renal compression in HF.[10,11] We will discuss these mechanisms and will coin a novel term for this: the "renal tamponade" hypothesis.
JACC Heart Fail. 2022;10(3):175-183. © 2022 American College of Cardiology Foundation