Acute kidney injury (AKI) refers to an abrupt decrease in kidney function, resulting in the retention of fluid and waste products in the body. This is a condition in which the kidneys suddenly can't filter waste from the blood. Acute renal failure develops rapidly over a few hours or days. It may be fatal. It is most common in those who are critically ill and already hospitalised. The causes for this disease include dehydration, drugs, infections, and stones. The symptoms include sudden drop in urine output and swelling of the body and high blood pressure, nausea, fatigue and shortness of breath. Sometimes symptoms may be subtle or may not appear at all. With timely diagnosis and treatment, the disease is completely curable. In addition to addressing the underlying cause, treatments include fluids, medication and dialysis.

When a kidney has been damaged for three or more months, the patient is said to be suffering from Chronic Kidney Disease. A kidney is said to be damaged when there are structural or functional abnormalities in the kidney. This disease evolves over months. The causes are diabetes, hypertension (high blood pressure), renal stones, pain killers(NSAIDS), obstruction of the urinary tract, cystic kidney disease and glomerulonephritis. In earlier stages, CKD is asymptomatic but patients may notice swelling of legs on prolonged travel or increased frequency of urination at night. Symptoms gradually increase as the kidney function deteriorates. The disease is divided into 5 stages based on glomerular filtration rate(GFR) which is usually derived from the serum creatinine value. The treatment of first four stages includes dietary measures, avoiding nephrotoxic agents, exercise, and controlling the underlying cause of kidney disease. Despite these measures some patient progress to the last stage i.e., stage 5. Stage 5 of CKD is referred to as End Stage Renal Disease (ESRD), also called Kidney Failure. Once the patient reaches this stage, the kidney function has declined to a stage that the kidney cannot function properly any more. At this stage, symptoms include headache, vomiting, nausea, fatigue, constipation, swelling of the body, itching, cramps, difficulty in focusing, altered sensorium and seizures. The management of ESRD includes initiation of Renal Replacement Therapy (RRT) and modifications in diet and medicines.

Nephrotic Syndrome occurs due to damage in the glomeruli (filters) of the kidney. Patient will notice swelling of the entire body, red coloured urine, and drop in urine output. Nephrotic syndrome is usually common in children, but adults are also affected. Diagnosis requires urine and blood examination. Some children may require kidney biopsy. Treatment is based on steroids and other immunity suppressing medicines. With regular follow up and treatment, these patients do well in the long run without significant kidney damage.

Kidney disease that develops and progresses over days to weeks is called Rapidly Progressive Renal Failure (RPRF). The causes are multiple involving various compartments of the kidney. Assessment by a nephrologist and kidney biopsy help in early diagnosis of the disease. Time is a valuable factor in the management of RPRF. If it is not detected or treated early, there is a high likelihood that these patients progress to Chronic Kidney Disease or End Stage Renal Disease.