Kidney disease, often referred to as nephropathy or renal illness, covers a variety of conditions that hinder the functioning of the kidneys. The kidneys play a crucial role in maintaining overall health by removing waste products, excess fluids, and electrolytes from the blood, controlling blood pressure, and releasing hormones that regulate the production of red blood cells and bone health.

Kidney disease is classified into various types based on the causes, progression, and symptoms.

1. Chronic Kidney Disease is a chronic condition characterized by gradually losing kidney function with time. It's usually caused by underlying conditions like diabetes, hypertension (hypertension), and glomerulonephritis (inflammation of the kidney's filtering units). Chronic kidney disease can be divided into five stages according to the estimated rate of glomerular hemofiltration (eGFR), an indicator of kidney functioning. To detect the disease, a CKD diagnosis is necessary.

2. Acute renal injury, also called acute kidney failure: AKI is an abrupt and serious impairment of the kidneys for an extended time. Many causes, such as severe infections, dehydration, specific medicines, or an immediate decrease in blood flow toward the kidneys, cause it. An acute kidney injury could cause an accelerated accumulation of fluid and waste imbalances in the body, necessitating urgent medical treatment.

3. Polycystic Kidney Disease: This inherited condition is characterized by the development of numerous cysts filled with fluid within the kidneys. In time, the cysts may enlarge and cause kidney swelling, reducing kidney function. There are two types of PKD, autosomal dominant PKD and autosomal recessive, the latter being more common and usually diagnosed in adulthood.

4. Glomerular Diseases: Glomeruli are tiny kidney filtering units that eliminate waste from the blood. Different conditions, like nephrotic disorder, glomerulonephritis, and IgA nephropathy, can impact the glomeruli and cause an impairment in kidney function. These disorders typically result in an inflammation of the kidneys or damage to them, which can cause leakage of protein and blood in urine and impaired elimination.

5. Diabetic Nephropathy: This type of kidney disease is a result of diabetes. In time, elevated blood sugar levels can damage the small blood vessels inside the kidneys, affecting their capacity to remove waste effectively. This condition is a major reason for CKD and kidney failure at the end of its stage, especially in those not well-managed with diabetes.

6. Hypertensive Nephropathy: High blood pressure causes damage to the blood vessels found in the kidneys, which reduces their capacity to function efficiently. In time, this may result in CKD. Monitoring blood pressure with medications or lifestyle modifications and controlling the underlying condition is crucial in preventing hypertensive kidney disease.

7. Kidney Stones: Kidney stones are crystals that form inside the kidneys due to the accumulation of salts and minerals. They can cause extreme discomfort and pain when they hinder the ureter. While they're not a chronic kidney problem, Recurrent kidney stones may result in kidney damage if not treated.

In sum, kidney disease is various ailments that impact the proper function of the kidneys. They can be divided into acute and chronic varieties, each with distinct reasons for their onset and characteristics. Kidney diagnosis, effective treatment of the underlying condition, and lifestyle changes are essential in preventing the progression of kidney disease and maintaining the kidneys' overall health.