The present disclosure relates generally to methods and apparatuses for organ diagnostics, and more particularly to methods and apparatuses for kidney diagnostics.
Measurement of kidney functions is an important step in the diagnosis and treatment of kidney diseases. One such measure of kidney function is the Glomerular Filtration Rate (GFR). GFR is defined as the volume of blood (blood plasma) filtered by the kidney within a given time and is typically measured in milliliters per minute (ml/min). The typical clinical method used to measure GFR is the measurement of urine creatinine clearance. Creatinine is a metabolic product of the body. However, the GFR estimated by measuring creatinine level in the urine is only an estimate and not a direct measure of the actual GFR. This is because creatinine is produced by the body constantly and secreted into the urine in addition to filtration. Typical GFR measurements take at least 6 hours to 24 hours to complete. However, GFR measurements may not be possible when serum creatinine levels are not in equilibrium such as during acute renal failure. Typical GFR measurement techniques require collecting urine samples and/or drawing blood samples.
There are many diseases that affect the kidney or functions of the kidney. Proteinuria is a marker of chronic disease. An animal (e.g., a human patient) with proteinuria may develop renal failure, and early detection of proteinuria is beneficial in the treatment of many underlying diseases. The typical diagnostic method for proteinuria is the measurement of the albumin level in the urine. Such measurement is typically done semi-quantitatively using urine dip sticks or by chemically measuring the urinary protein to creatine ratio. Quantitative analysis typically requires a 24-hour urine collection. However, even 24-hour urine collection may result in a delayed diagnosis because of protein removal from the urine by proximal tubule cell reabsorption. For example, proteins may pass through the glomerulus (kidney filtration barrier), enter into the renal filtrate, and be reabsorbed by the renal tubular cells leaving little to no proteins in the urine. This may be of particular concern in diabetic nephropathy when the earliest detection of an altered glomerular permeability to protein is crucial for institution of therapy.
Blood and urine glucose levels are also used as diagnostic measurement. Abnormal blood glucose levels are directly related to diabetes and other diseases. Typical methods used to determine blood and urine glucose levels require the drawing of blood and/or the measurement of glucose content in the urine. These methods are relatively slow and do not allow real time monitoring of blood glucose levels.
Further, in many applications, it is desirable to know the pharmacokinetics of a drug. Typical methods used to measure drug pharmacokinetics require the drawing of blood from an animal (e.g., a human patient) which can be painful and slow. Other methods used to measure drug pharmacokinetics include the use of heavy and expensive medical imaging devices such as MRI.