Back or side pain, blood in your urine, or an abnormal kidney blood test can all lead to the same next step: a kidney ultrasound, also called a renal ultrasound. The scan itself is easy, but the preparation has a few details that matter. If the instructions are not followed, the images may be harder to read and you could be asked to come back. This guide explains what a kidney ultrasound shows, exactly how to prepare, and how to book one in Toronto at Annex Medical Imaging.

What Does a Kidney Ultrasound Show?

Your kidneys are two bean-shaped organs that filter your blood and make urine. An ultrasound cannot measure how well they work, since that comes from blood and urine tests, but it can show their structure. Depending on your situation, the sonographer and radiologist may look at:

• Size and shape of each kidney, and whether the two look similar
• Cysts, which are fluid-filled sacs that are common and often harmless
• Kidney stones, especially larger ones inside the kidney
• Swelling of the kidney (hydronephrosis), which can happen when urine flow is blocked
• Solid areas that may need further imaging to understand
• The bladder, including how well it fills

Why Would a Doctor Order a Kidney Ultrasound?

The reason is on your requisition, and every situation is different. Typical reasons include:

• Pain in the side or back
• Blood in the urine
• Repeated urinary tract infections
• Abnormal kidney blood test results
• Follow-up of a known kidney stone or cyst
• A finding on a previous scan that your doctor wants to look at more closely

How to Prepare for a Kidney Ultrasound at Annex

The bladder and kidneys are easiest to see when you have not eaten recently and your bladder is comfortably full. Here is the routine from Annex’s exam preparation instructions:

1. Stop eating 6 hours before your appointment time. For example, for a 2:00 pm appointment, your last meal should be at 8:00 am.
2. One hour before your appointment, drink 4 cups of water (about 1 litre). Finish drinking by the one-hour mark.
3. Do not go to the washroom during that hour. A full bladder helps the sonographer see clearly.
4. Bring your requisition and Ontario health card. Wear comfortable, loose clothing.

If the full bladder becomes very uncomfortable, tell the front desk or the technologist. They can advise you on what to do. Ask your doctor or the clinic about your regular medications if you are not sure how they fit with the fasting window.

Check Which Exam Is on Your Requisition

The word on your requisition determines your preparation. A renal (kidney) ultrasound follows the steps above. An abdominal ultrasound, which includes the kidneys along with the liver, gallbladder, spleen, pancreas and aorta, requires fasting for 8 hours instead. A combined pelvic and abdominal ultrasound requires both the 8-hour fast and a full bladder. Our guides to abdominal ultrasound and fasting for an abdominal ultrasound cover those exams in more detail. If you are unsure, call us before the day of your appointment.

What Happens During the Scan

1. You lie on the exam table, usually on your back, and sometimes on your side or stomach so the sonographer can see each kidney from different angles.
2. A warm, water-based gel is spread over your back, side or abdomen.
3. The sonographer moves a handheld probe over the area and may ask you to hold your breath briefly for clearer pictures.
4. In some cases you may be asked to empty your bladder and be scanned again.

Annex notes that ultrasound exams generally take 15 to 45 minutes. The scan is painless, and you can usually return to your normal activities right away.

What a Kidney Ultrasound Can Miss

Ultrasound is a first-line test for good reason: it is quick, widely available and radiation-free. It is not perfect, though. Very small stones, or stones sitting in the thin tube that carries urine to the bladder (the ureter), can be hard to see. If your doctor still suspects a stone or a blockage after your ultrasound, they may order another type of test. That is routine and does not mean the ultrasound was done incorrectly.

Booking a Kidney Ultrasound in Toronto

Annex Medical Imaging is at 800 Bathurst St, Unit 304 (3rd floor), across from Bathurst subway station, open Monday to Friday 9:00 am to 5:00 pm and Saturday 9:00 am to 3:00 pm. Because of the fasting and water-drinking steps, it helps to book a time in advance and plan your day around it. Walk-ins for ultrasound are accepted only when a spot is open, so please call (416) 531-1128 first. Reports usually reach your doctor in 3 to 5 business days, and urgent reports are faxed within 24 hours when your physician requests it.

Related Reading

• Abdominal ultrasound and Preparation
• Pelvic ultrasound
• Prostate ultrasound and preparation
• Walk-In Diagnostic Imaging in Toronto: How It Works at Annex Medical Imaging
• Do You Need a Referral for an X-Ray, Ultrasound, or Mammogram in Toronto?
• Ultrasound Preparation in Toronto: Fasting, Full Bladder and What to Do for Each Exam
• When Will I Get My X-Ray or Ultrasound Results? What Happens After Your Scan

Frequently Asked Questions

Can I drink water while fasting for a kidney ultrasound?

Yes, and you are actually asked to. The 6-hour rule applies to food. In the hour before your appointment you drink 4 cups of water so your bladder is full.

What if I need to use the washroom before my scan?

Try to hold on, since a full bladder improves the images. If you are very uncomfortable, tell the front desk or the technologist and they will advise you.

Is a kidney ultrasound the same as an abdominal ultrasound?

No. A kidney (renal) ultrasound focuses on the kidneys and bladder, with a 6-hour food restriction. An abdominal ultrasound looks at several organs and needs an 8-hour fast. Follow the instructions for the exam named on your requisition.

Does a kidney ultrasound use radiation?

No. Ultrasound uses sound waves, not ionizing radiation.

Do I need a requisition?

Yes. Annex needs a requisition from your doctor or another eligible provider. With a valid health card, most exams are covered by OHIP.

This article is for general information only and is not medical advice. Always follow the preparation instructions given by your doctor and the clinic, and speak with your health care provider about your personal situation.