A kidney (renal) ultrasound is a simple, painless, noninvasive and very accurate exam that gives perfect insight in the very structure of the kidneys helping doctors evaluate potential anatomical abnormalities of the organ and confirm or rule out certain conditions.
Ultrasound of Kidneys
The kidneys are located in the abdomen, in the retroperitoneal area. Their primary role is to excrete waste products, excess of water and electrolytes from the body. The urine synthesized in the kidneys is pushed down the ureters, enters the bladder (the perfect reservoir) and eventually gets excreted with the urethra. The function of the kidneys is affected in many different medical conditions. Some of these cause changes that might be confirmed with available imaging methods (e.g. ultrasound, CT or MRI), while others trigger serious symptoms and can be only confirmed when tissues of the kidney are biopted and microscopically evaluated.
A renal ultrasound is a powerful tool used in case when patients are suspected to suffer from certain conditions or have suffered an injury to the organ. It can also visualize congenital abnormalities, confirm the presence of certain types of kidney stones and assess other types of blockage. A renal ultrasound is also very helpful when it comes to complications of an urinary tract infection or damage associated with cysts and tumors.
Now, as for kidney stones there are several types of these. Ultrasound can be efficient in visualization of clear uric acid stones and obstruction caused by any type of kidney stones. Most scientist agree on the fact that ultrasound simply is not sufficient enough to detect very small stones. However, it remains a very useful first diagnostic step in emergency rooms.
Apart from ultrasound, a standard X-ray of the kidneys may also reveal some kidney stones, calcium kidney stones in particular. This imaging technique is also helpful when it comes to diagnosing cystine crystals. The best diagnostic tool for kidney stones of any type is most certainly helical computed tomography scan.
How is Procedure Done?
Let us return to a kidney ultrasound. As for preparation there is practically none which means that this type of the exam can be easily performed at any time. However, in order for the organ to be visualized with an ease patients should not eat/drink anything several hours before the test.
A renal ultrasound is performed in the radiology department of the local hospital. It is also possible to undergo examination in a radiology center. The clothes from the upper part of the body should be removed because the probe comes into direct contact with the skin. The presence of clothes interferes with the exam. The person lies down on a table, usually on his/her side so that the back remains approachable to the radiologist. The room is supposed to be dark. Reduced light allows better insight in discrepancy between white and black shades on the computer screen.
The inspected area is covered with a clear, warm, water-based gel. The gel does not allow any air to come between the patient's skin and the probe(the transducer). Once the exam starts the probe sends ultrasound waves to the patient's body. These enter the body, some are absorbed, others refracted and return to the probe, are collected and finally form the images on the computer screen. By moving the probe and sending waves from different angles the radiologist obtains clear image of the kidneys and have better insight in their structural changes (if there are any). The entire procedure does not last longer than 30 minutes and is completely painless. The pain is only reported in individuals who have already experience discomfort or pain in the flank area prior to the exam.
Ultrasound is generally highly safe procedure associated with no radiation. Because of that it is indicated in people of all ages, both genders and is even safe for pregnant women. What is more, the exam does not last long so it can be utilized when quick evaluation is necessary which is the case with many emergency conditions.
In case of acute renal colic, when there is a chance the person is suffering from kidney stones doctors take into consideration several factors. The first one is the patient's clinical presentation. The second is urinanalysis and finally, there are imaging techniques, ultrasound being the first procedure of choice.
The exam is supposed to rapidly evaluate the patient and give answers to several questions. For example, the ultrasound may easily confirm/rule out hydronephrosis (swelling of one kidney due to a backup of urine), the presence of fluid around the kidneys, distension of the renal pelvis and the presence of kidney stones which can be identified with ultrasound.
After the initial assessment, patients undergo additional exams such as IVP (intravenous pyelogram) or CT scan. Both of these are highly efficient in confirming the presence of kidney stones when these cannot be adequately evaluated with ultrasound.
All in all, a renal ultrasound is a very useful exam which allows doctors to quickly evaluate the condition of kidneys without exposing patients to radiation or using IV contract. The test can be repeated without any harm. Still, it cannot reveal every type of kidney stones, therefore patients usually require additional exams.