Diagnosing Accute Renal Failure

Problem: A man arrives at a clinic with complaints of asthenia, malaise, headache, weight gain, and a decrease in urination. A tentative diagnosis of acute renal failure is made.

1. Explain the pathophysiology of acute renal failure. Include prerenal, intrarenal, and postrenal causes.

The kidneys are responsible for multiple jobs that are necessary for the survival of the human body. Some of its functions are filtering wastes from the blood, regulate blood pressure, and regulate salt and water balances in the body. The upper and lower tract of the urinary system is commonly affected by problems such as infection and incontinence. However, in some cases an individual may develop acute renal failure. Its rapid development impairs the kidneys unless the underlying cause of the problem is found immediately and treated properly.

When the cardiovascular system fails to perfuse the kidneys adequately with blood, the result is acute renal failure. In acute renal failure (ARF) the kidneys suddenly loses its ability to excrete wastes, concentrate urine, conserve electrolytes, and maintain fluid balance (Schrier, Wang, Poole & Mitra, 2004). The glomerulus, or the capillary network inside the Bowman’s capsule, is responsible for the entire filtrating system of our kidneys. Blood enters the kidneys through the renal arteries and leaves through the renal veins. The strength of pressure exerted onto the kidneys is what makes the glomerular filtration work. Nevertheless, this pressure depends upon the flow of blood and the resistance between the afferent and efferent arterioles. At any given time when the flow of blood is obstructed, the glomerular filtration rate (GFR) decreases. This pathologic pathway leads to the underlying cause of acute renal failure. It consists of three mechanisms: prerenal, intrarenal, and post renal or obstructive (Workeneh, 2013).

When there is no renal perfusion, the glomerular filtration rate (GFR) is undermined. Fluid leaving the glomerulus and Bowman’s capsule is filtered and enters the convoluted tubules. During prerenal, these tubules and the glomerulus still remain normal. Some of the prerenal causes include hypovolemia, dehydration, medications such as diuretics, and obstruction of the renal artery or vein (MedicineNet, 2013). The result of the prerenal phase is the most common cause of acute renal failure because it eventually leads to hypoperfusion and ischemia. In intrarenal, the kidney is damaged and the glomerulus and tubules are the ones chiefly affected. When there is tubular damage, the afferent arterioles constrict causing the vessels to get narrow and eventually make it difficult for blood to flow.