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Kidney Ultrasound

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A kidney ultrasound is a medical procedure in which sound waves are used to take images of the kidney, the ureters, and the bladder for diagnosis.

Medically reviewed by

Dr. Raveendran S R

Published At June 23, 2022
Reviewed AtMarch 6, 2023

What Are the Functions of the Kidneys?

Kidneys are bean-shaped organs present in pairs in the lower abdomen.

Functions of the kidneys are-

  • Production of urine by filtering the blood.

  • Removing extra fluid and waste materials from the body.

  • Regulating blood pressure by releasing hormones.

Kidney functions can be impaired by the presence of calculi, cysts or tumors, abscesses, and the presence of infection, which can be detected using ultrasound. Ultrasound is also called sonography or ultrasonography. Ultrasound uses high-frequency sound waves to create images of the internal structures of the body.

What Is a Kidney Ultrasound?

The study of kidneys is called nephrology, and the physician who specializes in the study of the kidneys is a nephrologist. A kidney ultrasound or renal ultrasound is advised by a nephrologist to study and diagnose if any kind of kidney dysfunction is present.

Ultrasound uses high-frequency sound waves, which are sent by a transducer pressed on the skin. The sound waves move through the body, rebound on the organs, and reflect back to the transducer. These sound waves from the ultrasound are used to create images from inside the kidneys and related organs.

Ultrasound is used in nephrology for scientific studies of the kidneys and urinary tract infection and to guide procedures, such as the insertion of catheters and needles in kidney biopsy (a procedure in which a small piece of the kidney tissue is taken out and studied under a microscope for any changes than normal).

Ultrasound of the kidneys is essential in the diagnosis and management of kidney-related diseases. The kidneys can be examined, and the most pathological changes in the kidneys can be found with ultrasound. It is safe as there is no exposure to the radiation, non-invasive as it does not involve any instrumentation to the body, and easily performed as it can be carried out at the bedside or in the office.

When Is a Kidney Ultrasound Required?

Ultrasound images are used to know-

  • The location of the kidneys.

  • The size of kidneys - Kidney length in adults, maybe between 10 to 12 cm, but varies with body size.

  • The shape of the kidneys.

  • Blood flows to the kidneys.

  • The urinary space, the vasculature, and the presence of masses.

A nephrologist may recommend a kidney ultrasound when there is a concern about -

  • A kidney injury.

  • Presence of infection.

  • Kidney abscess.

  • A blockage in the urinary tract.

  • Accumulation of urine inside the kidneys - Hydronephrosis.

  • Cyst or tumor inside the kidney.

  • Kidney stone or renal calculi.

Other reasons include -

  • Serve as a guide to inserting a needle for a tissue or fluid kidney biopsy.

  • To place a tube into the kidney

  • To check for the transplanted kidney.

  • To check for the urinary bladder (the organ that stores urine).

  • To check if there is fluid collection inside the kidneys.

What Is a Sonogram?

Ultrasound, also called sonography, is a method of using sound waves to create images of the structures inside the body. These images formed from the ultrasound are the sonograms. These echos are recorded and converted into video or images of the tissues and organs selected for examination. The sonogram is then read by a radiologist for the results.

What Is the Procedure of a Kidney Ultrasound?

  • The procedure starts with changing the normal outfit into a hospital gown.

  • A gel will be applied on the skin where the examination needs to be done. This gel serves to increase contact between the transducer and the skin, improving sound wave transmission into the body. This gel helps to conduct the sound waves produced by the transducer.

  • The transducer emits sound waves into the body. These waves will reflect off the kidney and other internal structures and are digitally converted into images and videos of the internal organs.

  • The images created by the ultrasound are stored digitally for future reference.

  • Multiple images of your bladder, both before and after urination, will be taken. This helps in interpreting the ultrasound data because of the close working relationship between the kidneys and bladder.

  • These findings are then sent to a radiologist for interpretation and are received by the consulting physician, which may require one to two days.

  • This is a painless procedure that may require 30 minutes to complete.

  • After the ultrasound, there is no special type of care required.

  • Resume normal diet and activities unless your physician has advised you differently.

How Are Kidney Stones Detected?

Kidney and bladder stones are solid substances made from minerals and proteins found in urine. Certain bladder conditions and urinary tract infections can increase the chance of developing stones. Kidney stones can be diagnosed using:

  1. Urine Tests - Urine tests are done to detect the presence of blood and minerals forming kidney stones.
  2. Blood Tests - Blood tests to check elevated levels of uric acid and calcium.
  3. Imaging Tests -

What Do Colors Mean on Ultrasound?

The color on the ultrasound is color Doppler. It detects movement and is used to know the blood flow in arteries and veins. The different colors indicate in which direction the blood flow is going and also verify the intensity or velocity of the flow. The dark color means the velocity is higher.

The color is blue or red depending on whether the blood movement is towards the transducer or away from it. Blue represents that the blood flow is away, and red represents that the blood flow is towards the transducer. Red means flow in one direction, while blue means flow in the opposite direction.

Color improvement is done using Doppler imaging, where tones of red indicate blood flow away from the transducer and tones of blue indicate blood flow towards it. This color-coding is used to check for any blockages present.

When the Doppler imaging is done in the pelvic region, it can help find:

  • Blood flows to the kidneys, ureter, bladder, and pelvic area.

  • Abdominal aortic aneurysm.

  • Blood flows to the baby during pregnancy.

  • This test helps best to diagnose deep vein thrombosis (DVT).

Conclusion:

Ultrasound is a non-invasive and painless procedure and does not require any special instruments other than the ultrasound machine. It is a safe procedure as it does not involve any radiation exposure. Doppler imaging is a precise technique to find any obstruction in the blood flow. Kidney stones can be best detected using ultrasound. A kidney ultrasound includes imaging of the kidneys as well as bladder and ureter so the exact location of the kidney stones can be found. No special care, and no diet changes are required after the ultrasound.

Frequently Asked Questions

1.

What Are the First Signs of Kidney Disease?

Kidney disease can present with the earliest symptoms such as fatigue and dizziness, changes in urination, and swelling or edema. Other signs and symptoms of kidney disease include - nausea and vomiting, loss of appetite, swelling in the feet and ankles, muscle cramps, dry and itchy skin, shortness of breath, trouble sleeping and urinating either too much or too little. High blood pressure and blood and protein in urine can also be seen.

2.

What Are the Signs That Your Kidneys Are Not Working Properly?

Signs that indicate kidney impairment include nausea and vomiting, loss of appetite, swelling in the feet and ankles, muscle cramps, dry and itchy skin, shortness of breath, trouble sleeping, and urinating much or too little, presence of blood in the urine (hematuria), and presence of protein in the urine (proteinuria).

3.

Why Would They Do an Ultrasound on the Kidneys?

A nephrologist recommends a kidney ultrasound to rule out the presence of a kidney injury, the presence of infection, or kidney abscess. It is also used to check for urinary obstruction caused by kidney stones. It also detects the accumulation of urine inside the kidneys (hydronephrosis).

4.

What Would an Ultrasound of the Kidneys Show?

An ultrasound of the kidney can show the location of the kidneys. It can detect the size and shape of the kidneys. It can be used to check blood flow to the kidneys, the urinary space, the vasculature, and the presence of masses.

5.

Can Ultrasound Diagnose a Kidney Disease?

Yes, kidney disease can be diagnosed on ultrasound. Ultrasound can diagnose a kidney injury, presence of infection, or obstruction. It can also detect the presence of kidney stones.

6.

How Long Does a Kidney Ultrasound Take?

A kidney ultrasound is a painless and non-invasive procedure. It can take 30 to 45 minutes for the procedure to complete. No special type of care is required after the ultrasound.

7.

Do I Need to Fast for a Kidney Ultrasound?

If your physician tells you to, you can fast for 8 to 12 hours before your ultrasound. That is because undigested food in the stomach and urine in the bladder can block the sound waves, making it hard to get a clear image.

8.

Can You Eat Before a Kidney Ultrasound?

You can eat or drink before an ultrasound unless restricted by your doctor. You can drink a minimum of 24 ounces of water at least one hour before your appointment. Do not urinate before the procedure.

9.

Can I Drink Coffee Before a Kidney Ultrasound?

Unless told otherwise by your healthcare provider before the ultrasound, you can eat or drink as normal on the day of your test. If your doctor needs a post-void of the bladder, you will have to be required to drink 30 ounces of water an hour before the exam. You cannot urinate until after the ultrasound.

10.

What Happens if You Pee Before an Ultrasound?

Having a full bladder can help in taking better images of the organs. Urinating before the ultrasound can clear the bladder. Thus, it hampers the details of the ultrasound images.
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Dr. Raveendran S R
Dr. Raveendran S R

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