Humans have two kidneys. They are bean-shaped organs about the size of a man's fist, located on either side of the spine "behind" the abdominal cavity. Normally the kidneys cannot be felt because the are located deep under the rib-cage behind the abdominal organs. The adrenal glands are located on top of each kidneys. At the inner side of the kidney a small tube, the ureter, connects the kidney to the bladder. The urine is squeezed from the kidney towards the bladder (peristalsis) by way of muscle fibers in the wall of the ureters. At the bladder end of the ureter a valve prohibits backflow of urine to kidney.
Function (what do they do?)
The kidneys remove waste products and water from our bodies. The kidneys act as a giant sieve with very small holes allowing only unwanted materials to be removed. Normally, blood cells and bigger molecules like proteins are too big to pass through the holes and will remain in the blood stream. The production of urine goes on day and night, although slower during the night - to ensure that you get your rest (and do not have to leave your bed).
Because the blood flow through each kidney is so huge, the organ is well equipped to monitor blood pressure. If the blood pressure gets too low, the kidney will produce a hormone that signals other parts of the body, like the heart, to increase the pressure to maintain normal blood flow to the kidneys. The adrenal glands produce hormones responsible for the production of, among others, adrenaline, which enables the body to release large amounts of energy, for example in running and fighting.
Diseases, Signs, and Symptoms (what can go wrong?)
Diseases of the kidneys can be subdivided into a few categories:
Malfunctioning of the kidneys
This may be caused by:
Interruption of the blood supply to the kidneys.
Diseases of the kidney itself where the sieve itself is damaged. This can be due to frequent infections, some medicines (like phenacetin, until a few years ago sold as a popular general pain killer) or poisons (like 'heavy metals', Cadmium, etc.)
Diseases concerning the drainage of urine. This problem could be caused by obstruction of one or more of the millions of small tubes inside the tissue of the kidney, or more frequently located somewhere downstream, in the pelvis or the ureter like a stone or blockage from an inborn obstruction or a tumor.
Infections
The tissue of the kidney can get infected by backflow of infected urine from a bladder infection when the natural valve is malfunctioning allowing reflux leading to high fevers and serious sickness. Infection can also reach the kidneys through the bloodstream. Tuberculosis of the kidney was a common finding years ago, and may again be more commonly seen with the advent of Immune-deficiency diseases like AIDS. Tuberculosis normally starts in the lungs, then spreads to the blood and finally infects other organs like the kidneys.
Cancer of the kidney
The tumors tend to be silent for a long time and pain or blood in the urine will generally only occur after they become large and displace other organs. Fortunately, more and more of these tumors are nowadays discovered incidentally, when an ultrasound or CT scan of the abdomen is made for other reasons. Cancer of the pelvis of the kidney or ureter may also cause obstruction of the outlet or bleeding in the urine. It is therefore very important that any discoloration or blood in the urine be immediately evaluated by a doctor to determine the cause.
Examinations (what can we check and how?)
The kidney and its function can be investigated in different ways.
Blood
A complete blood count and sedimentation rate may indicate an infection in the body
Creatinine concentration in the blood can be measured. Creatinine is a waste product of protein and should be eliminated from the blood by the kidneys. If both kidneys do not function as they should, this could result in high creatinine levels.
Uric acid and calcium determinations may be abnormal in stone-formers.
PSA (prostate specific antigen). A relatively recent blood test which if abnormal can show abnormalities of the prostate like infections, BPH or cancer.
Urine
A routine urinalysis uses a chemistry-coated strip to determine the acidity of urine as well as finding sugar, protein, blood and other substances present in abnormal levels. Microscopic examination may show certain crystals, blood cells, abnormal cells and casts which are helpful to the doctor to diagnose certain conditions of the urinary system. A 24-hour collection of urine determines the normal volume and waste product level in the urine.
IVP (Intravenous Pyelogram)
This is performed by injecting an X-ray visible liquid into a vein in the forearm which will be transported by the bloodstream towards the kidneys, recognized as waste and concentrated and excreted into the urine. This liquid makes the urinary system visible in X-ray films.
Ultrasound
The kidneys, bladder, prostate and testicles can be seen very well by way of ultrasonic sound waves because these organs have a high water content.
CT (Computerized Tomography)
Scans the body using X-ray imaging and a computer to recreate a very accurate picture of the body's internal structure.
Cystoscopy and Retrograde Pyelography
A small metal or fiber-optic tube utilizing a light and a fluid source is passed through the urethra (the external urinary canal) to diagnose problems of the lower urinary system. The procedure is usually done using local anesthesia and is well-tolerated as an office procedure.
Other specialized diagnostic and therapeutic techniques using specialized internal telescopes, radioisotopes and MRI scans may be ordered by your urologist as the need arises.
What is Urology?