Ultrasound of the urinary tract involves the use of an

ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...

probe to image parts of the

urinary tract The urinary system, also known as the urinary tract or renal system, consists of the kidneys, ureters, bladder, and the urethra. The purpose of the urinary system is to eliminate waste from the body, regulate blood volume and blood pressure, c ...

. The urinary tract is the path that

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...

follows after it is formed within the

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...

s, and involves a left and right

ureter The ureters are tubes made of smooth muscle that propel urine from the kidneys to the urinary bladder. In a human adult, the ureters are usually long and around in diameter. The ureter is lined by urothelial cells, a type of transitional epit ...

, the

bladder The urinary bladder, or simply bladder, is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine enters ...

, and the

urethra The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra c ...

Procedure

Ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...

involves a probe that is placed near a structure and uses the transmission of ultrasound waves through a structure to produce images, after computer processing. Ultrasound of the urinary tract is performed by a probe placed on the abdominal wall, called a transducer. This occurs while a person is lying down. It is then moved around to better visualise different parts of the urinary tract. Gel is used on the abdominal wall, allowing smooth movement and improve sound conduction. The images are usually taken by a trained ultrasonographer, and then reported by a specialist radiologist. Prior to the test, a medical practitioner will have conducted a medical history to evaluate for symptoms that may relate to the urinary tract. Before the exam, the person will need to drink three glasses of water (about 500 ml) at least one hour before the exam. If the person is on fluid restriction diet (due to heart, liver or kidney problems), then he can ignore the instruction. If there is a

urinary catheter In urinary catheterization a latex, polyurethane, or silicone tube known as a urinary catheter is inserted into the bladder through the urethra to allow urine to drain from the bladder for collection. It may also be used to inject liquids used ...

, the catheter should be clamped immediately after drinking the water. The person should not pass any urine until the scan is over. If the urinary bladder is the subject of interest, a person will be asked to pass urine and the amount of urine left in the bladder may be recorded.

Uses

For imaging of the urinary tract it may involve: * Assessment of the urinary tract for abnormalities such as blockage or narrowing, the presence of

kidney stone Kidney stone disease, also known as nephrolithiasis or urolithiasis, is a crystallopathy where a solid piece of material (kidney stone) develops in the urinary tract. Kidney stones typically form in the kidney and leave the body in the urine s ...

s, or tumours. * Use of

duplex ultrasound Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to perform imaging of the movement of tissues and body fluids (usually blood), and their relative velocity to the probe. By calculating the frequency shift of a ...

to determine if there is backward flow of urine, for example in vesicoureteric reflux. * Determination of how much urine is in the bladder, for example to assess for

urinary retention Urinary retention is an inability to completely empty the bladder. Onset can be sudden or gradual. When of sudden onset, symptoms include an inability to urinate and lower abdominal pain. When of gradual onset, symptoms may include loss of bladd ...

. * To look for evidence and the cause of chronic kidney disease, for example shrunken kidneys. * To assist with an interventional procedure, such as the taking of a biopsy, or draining of an abscess or cyst. * To monitor a kidney transplant. The symptoms that a person may experience that cause the test to be requested may be blood in the urine, abdominal pain, abdominal kidney function tests, and frequent

urinary tract infection A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidne ...

s (of which symptoms may include the need to pass urine frequently, pain on urination, and worsening urinary incontinence).

Risks

Ultrasound is non-invasive and does not involve radiation, unlike some methods of imaging of the urinary tract such as

X-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nbs ...

or CT scans. It is usually painless. It is safe in pregnancy. Risks specific to the scan involve: * Discomfort from the abdominal probe * Distress related to results that are reported * Financial risks related to the scan, especially if it produces an indeterminate result * Risks entailed with treatment or further investigations required following the results. Abdominal obesity, gas within the colon, and barium within the intestines can all impact the accuracy of the test.

Other tests

Other tests are available to image the urinary tract. These include

, CT scans or

MRI scan Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...

References

{{Medical imaging Ultrasound Urologic imaging