CT Scan for Kidney Stones: How to Prepare and What to Expect

If you have symptoms that are associated with kidney stones, your doctor might recommend a CT scan (computed tomography) to confirm the diagnosis and determine the stone’s location. This guide explains what to expect during the scan, how to prepare, when to expect your results and potential next steps. 

While this guide provides helpful information about CT scans, your doctor will give the official interpretation of your results during a follow-up appointment or phone call. However, if you’d like early access to your results, PocketHealth offers secure, instant access to your report when it is available. This allows you to review the findings in advance and prepare any questions for your follow-up appointment.

 

 

What is a kidney stone?

Kidney stones form when there’s an imbalance of minerals in the body, such as uric acid or calcium. This leads to stone-like deposits forming in the kidneys. Patients often won’t realize the stones are there until one begins to move from the kidney into a ureter. There are two ureters, one connecting each kidney to the bladder. The stone moves through one of these, ideally reaching the bladder and exiting with the urine.

Some kidney stones are so small that patients may not notice them, around the size of a grain of sand. However, others can grow as large as a golf ball, though this is rare. The typical kidney stone that patients experience is about the size of a pea. Because of this, patients often notice when a kidney stone enters the ureter, as it can be very painful. For some, if the stone is larger, it can block the ureter, causing inflammation in the kidney and ureter, swelling and difficulty urinating.

In most cases, patients can pass the stone through the ureter over time. Drinking plenty of water can help speed up the process, and medications are often prescribed to assist. However, if the stone is too large to pass on its own, procedures or surgery may be required to eliminate the stone. This will be discussed in more detail later in the guide.

What are kidney stone symptoms?

There are several symptoms that patients may experience. If the stone is very small, they may not go through any of these. Otherwise, these are the most common symptoms:

• Side/back pain: Medically termed “renal colic” or “flank pain,” this is when the patient experiences intense, shooting pain in their back or side. It can come and go in waves and may even cause referred pain, such as in the ovaries, abdomen and groin. The pain results from the inflexible ureter spasming in an attempt to dislodge the stone, as well as the pressure from urine backing up into the kidney.
• Nausea and vomiting: These are common symptoms and can be triggered by the pain itself. They may also occur because the gastrointestinal tract and kidneys share nerve connections, which can be disrupted by the stone.
• Urine changes: Urine-related symptoms can include an ammonia-like smell, cloudy or discolored appearance, hematuria (blood in the urine), a frequent urge to urinate or difficulty urinating due to a blocked ureter.
• Fever and chills: This could be caused by a urinary tract infection from the stone and should be reported to your doctor immediately so they can prescribe treatment.
• Pelvic/groin pressure: If your ureter is blocked, it can cause uncomfortable groin pressure, especially when trying to urinate.

 

What is a CT scan?

A CT scan is a medical imaging technique that uses X-ray technology to create detailed images of internal structures. Unlike a standard X-ray, a CT scan produces cross-sectional views, or “slices,” which reveal blood vessels, soft tissues and bones.

CT scans can be used for a wide range of medical diagnoses, but in the case of kidney stones, they are particularly useful for determining the size and location of the stone, as well as checking for inflammation in the kidney and ureter.

CT scan vs ultrasound for kidney stones

An ultrasound is another imaging method, but it does not use X-ray technology. Instead, it uses sonic waves produced by a device called a transducer, which move through the internal structures and organs. The echoes of these waves bounce back and form images on a computer, which can then be captured for study.

While CT scans are considered the standard imaging method for kidney stones, ultrasounds are also commonly used. Though they may not provide as much detail as a CT scan, ultrasounds are nearly as effective for diagnosing larger stones. They can also provide information about the stone’s location, approximate size and whether the kidney is experiencing inflammation.

The main reason to opt for an ultrasound instead of a CT scan is that ultrasounds don’t use radiation. If the patient has had significant radiation exposure in the past, an ultrasound is a good alternative to avoid adding to that. Additionally, ultrasounds tend to be less expensive for the patient than CT scans.

 

How is a CT scan for kidney stones performed?

A CT scanning machine consists of an exam table that moves as needed and a large, doughnut-shaped tunnel. You will lie on the table as directed (typically on your back), and the imaging technician will move the table into the center of the tunnel.

You will be asked to remain still and occasionally hold your breath during the scan, as movement can blur the images. The technician will control the CT machine from an adjoining room.

Once the table positions you inside the scanner, the rotating X-ray tube will move around you and capture image slices of your abdomen and pelvis. If needed, you can communicate with the technician through an intercom, which is also how they will instruct you on when to hold your breath. The entire procedure typically takes 15 to 30 minutes.

You may have heard of a CT scan with contrast (a dye injected during the scan to enhance the images). However, it’s uncommon for patients to receive contrast during a CT for a kidney stone. First, the stone will appear bright white on the images, making it visible without contrast. Second, the contrast agent can be hard on the kidneys, which is something to avoid when dealing with a kidney stone.

 

How to prepare for a CT scan

If you went to the emergency room for your kidney stone, chances are you will have the scan at the hospital and won’t need to make preparations. Otherwise, patients will usually have their scan scheduled by their referring provider. If that is your circumstance, here are some helpful tips to help prepare you for your imaging appointment.

Before the appointment

• Arrange a ride to and from the appointment: Patients experiencing kidney stones often have significant pain, which can make driving unsafe. If you’ve already received pain medication from your doctor, stronger medications may make driving dangerous due to drowsiness or dizziness.
• Examine your requisition form: If you were given a requisition or other instructions, it’s a good idea to re-read them. This ensures that no important details or preparations are overlooked. For example, some doctors recommend you not eat or drink a few hours before your CT scan, whereas others don’t have that requirement. It is helpful to ask in advance for any prerequisites.
• Let your doctor know if you have nausea: Nausea can make medical appointments and other activities challenging. If you’re able, consider asking your doctor for a prescription to help manage the nausea, so you can have the exam without issues. Keep in mind that every patient is different—one anti-nausea medication may work for some but not for others. If the prescribed medication isn’t effective, there are other options that may be more successful, so be sure to ask for alternatives.
• Work out in advance where your scan is: If you’ve never been to the imaging clinic before, try to find out exactly where to check in. This is especially important if the appointment is at a large facility or hospital you’re unfamiliar with. Planning ahead can help prevent getting lost, which can be particularly challenging when you’re not feeling well.
• Let your doctor know if you think you may be pregnant: The general recommendation is to avoid unnecessary CT scans during pregnancy to prevent exposing the fetus to radiation. If this is the case, your doctor can discuss alternative imaging techniques, such as an ultrasound.

The day of the appointment

• Bring your requisition form: If the imaging facility doesn’t have your form on hand, having it with you can save time during check-in. Also, be sure to bring your ID and health card.
• Avoid wearing metal objects: This includes jewelry, bras with metal clasps/underwire, eyeglasses and other metal items.
• Wear easy-to-remove clothing: You may be asked to change into a hospital gown, so it’s best to wear something easy to take off. However, many facilities allow you to stay in your clothes as long as they are appropriate for the scan.

After the appointment you can go back to your day as usual.

 

Getting my results

Understandably, patients frequently want their CT scan results back as soon as possible. This section will cover common questions regarding when to expect your results and who deciphers them.

Who interprets my results?

A medical imaging specialist, called a radiologist, will interpret your CT images. They will communicate any findings or recommendations, at which point your referring physician will receive your report. If your physician has additional insights or diagnostic interpretations based on your medical history, they may add this to your records as well.

When will I get my results?

For most CT scans, results can take up to a week or longer, depending on the schedules of the radiologist and your referring doctor. In many cases, patients receive their results during a follow-up appointment with their doctor. However, kidney stone scans may be expedited due to the painful nature of the condition. Even so, if your doctor is busy or there are delays with the radiologist, it may take longer than expected to hear back.

If you’d like to view your report as soon as possible, PocketHealth provides faster access, allowing you to see the results as soon as they are officially released, often before your follow-up with your doctor. This gives you time to review the findings and prepare for your next medical visit or phone call.

MyCare Navigator is especially helpful for offering personalized insights and identifying any recommended follow-up steps. PocketHealth also generates personalized questions to ask your doctor based on the findings in your report, ensuring you make the most of your consultation.

Understanding my results

Although your doctor will provide an official explanation of your results, accessing your report before your appointment can give you an early glimpse. It’s common to find medical terminology complex and confusing, but PocketHealth Report Reader makes it easier by offering clear, straightforward definitions for medical terms—simply tap or click on any underlined words to reveal their meaning.

Meanwhile, here are some common medical terms you may encounter on your report:

• Unremarkable: This means nothing noteworthy was seen (which is good).
• Renal calculus or nephrolith: This is another term for kidney stone.
• Distal/mid/proximal: You may see a result such as “Right distal ureter 5 mm calculus” or another similar description. These terms refer to the location of the stone. Distal means it is lower in the ureter, proximal means it is near the top and mid means it is located in the middle. This is important because it can help indicate how well the stone is moving through the ureter.
• Urolithiasis: A term that refers to the condition of having stones in the urinary tract, including the kidneys.
• Nephrolithiasis: Sometimes called renal lithiasis, this is similar to urolithiasis, it is the condition of having stones in the kidneys in particular. It is a more specific term, whereas urolithiasis is a broader term for the entire urinary tract.
• Hydronephrosis: This condition occurs when the kidney swells due to a buildup of urine caused by a blockage. It can lead to reduced urine output, pelvic pressure, urinary tract symptoms and other complications. In severe cases, it can cause kidney damage, so it’s important to see a doctor if you experience symptoms of hydronephrosis. Fortunately, most cases are mild to moderate, and most patients recover fully without any lasting kidney damage.

 

How are kidney stones treated?

How a kidney stone is treated depends on its size, the patient’s pain tolerance, and the doctor’s recommendations. Many people who experience kidney stones, especially if they are a recurring condition, try to wait it out at home. Passing a stone can take anywhere from hours to weeks, depending on the patient’s condition and how they feel during this period.

It is recommended to see a doctor if you have symptoms of a kidney stone. Even if you’ve had one before and recognize the symptoms, it’s a good idea to inform your doctor. Typically, they will order imaging, such as a CT scan or ultrasound, to confirm that a stone is causing the symptoms and to estimate its size. The larger the stone, the more likely it is to cause a blockage, so in these cases the doctor will monitor it closely and decide if surgical intervention is necessary.

Here are some of the common steps and treatments doctors recommend for kidney stones:

• At-home pain management: Some things to try at home for discomfort include taking hot baths, using hot pads, taking over-the-counter pain medications, drinking fluids, and trying to move around as much as is feasible while in discomfort. Low-impact movement can help the kidney stone move in the ureter.
• Blood work: Blood testing can determine if there is excess uric acid or calcium in the patient’s blood. This helps monitor their condition and assess kidney function.
• Urine testing: A urinary tract infection is common during a kidney stone episode. Urine testing allows the doctor to check for an infection and prescribe appropriate medications if necessary.
• Drinking water: Unless otherwise instructed, such as in cases of severe hydronephrosis, most patients are encouraged to drink 2 to 3 quarts of water a day to help smaller stones pass.
• IV fluids: Due to how prevalent nausea and vomiting are for kidney stone patients, many may become dehydrated. Doctors may recommend IV fluids to help counter this.
• Medications: Pain relievers are typically recommended or prescribed. Depending on the patient’s condition, the doctor’s preference and the stone’s size, these may be over-the-counter medications or prescriptions, such as morphine. Additionally, an alpha blocker like Flomax is often prescribed to help relax the ureter and make it easier to pass the stone.
• Sound waves: For larger stones that won’t pass on their own, several treatment options are available. One of these is extracorporeal shock wave lithotripsy (ESWL), in which sound waves break the stone into smaller pieces, allowing them to pass harmlessly through the urine. The procedure is typically performed with the patient under light anesthesia or sedation. While some discomfort may occur during recovery, most patients can return to their daily routines within a few days.
• Ureteroscope: For stones that aren’t too large, the doctor may use a lighted, thin tube with a camera (a ureteroscope) to pass through the patient’s urethra, bladder, and into the ureter. From there, the stone can either be removed or broken up so it can exit through the urine. Often, a small stent (tube) is temporarily placed in the ureter to allow urine to pass freely during the healing process. This procedure is typically done under anesthesia or sedation.
• Percutaneous nephrolithotomy: This technique is used to remove larger stones through an incision in the patient’s back. The doctor accesses the kidney through the incision, using specialized instruments to break up the stone and remove the larger fragments. It is performed under general anesthesia, and recovery typically takes 4 to 6 weeks. This method is less commonly needed, as most patients have good success with sound wave and ureteroscopic procedures.

 

How to prevent kidney stones?

The cause of kidney stones can vary by patient. In general, an excess of a particular mineral or substance leads to the formation of these stones. The type of excess substance determines the type of treatment required.

Typically, patients are provided with a strainer to use while urinating during the process of passing the stone. Each time they urinate, they are instructed to use the strainer so that any stones or fragments can be collected and sent to the lab for analysis. Knowing the mineral composition of the stone helps the doctor determine specific treatments to reduce the buildup of these minerals.

If patients are unable to collect the stone (for example, if the particles are too fine), they may be asked to complete a 24-hour urine collection. During this period, urine is collected and sent to a lab for analysis, where it can be tested for high levels of crystals, minerals and other substances that may contribute to stone formation.

Kidney stone types are classified based on the types of crystals they contain. Here are the most common types:

• Struvite stones: These are caused by repeated bacterial infections, which can lead to large kidney stones known as staghorn calculus. Prevention involves methods to reduce bacterial infections.
• Uric acid stones: These are linked to a diet high in animal proteins such as fish, meat and eggs. Prevention typically involves eating fewer of these protein sources.
• Cystine stones: This condition is inherited and causes cysteine and amino acids to bind together, forming stones. Prevention includes drinking more water, reducing sodium intake and possibly taking medications to help dissolve cysteine in the urine.
• Calcium-oxalate or calcium phosphate stones: These are the most common type of kidney stone and are caused by eating low-calcium foods or high-oxalate foods. Doctors will recommend avoiding certain foods and increasing water intake.

Overall, the recommendation is to decrease salt intake (a major factor in stone formation) and increase water intake. Other medical conditions and lifestyle habits can increase the risk of kidney stones. These include:

• Taking too much vitamin C
• Urinary tract conditions and blockages
• A history of intestine or stomach surgery
• Osteoporosis
• Obesity
• Diabetes
• Cystic fibrosis
• Kidney cysts
• Other medical conditions

 

Frequently asked questions

Here is a brief guide to the most frequently asked questions about kidney stones and CT scans.

How long does it take for kidney stones to pass?

This depends on the size of the stone and the patient’s individual characteristics. Everyone is unique, so what is standard for one person may not be for another. In general, the smaller the stone, the more quickly it tends to pass. Some small stones may pass in a matter of hours or a few days, whereas larger stones (over 5mm) may take longer—possibly days or even weeks. There is significant variation in these timeframes. Important factors include:

• Drinking water to help encourage stone movement
• Medications to relax the ureter
• Physical movement (if tolerated)
• Possible medical intervention

It is recommended to inform your doctor if you’re experiencing a kidney stone. You may even be referred to a urologist, a specialist in urinary conditions. If your kidney stone doesn’t seem to be passing, or if it is determined to be large, you may want to ask about potential procedures to have it removed.

What are the first signs of kidney stones?

The initial signs of a kidney stone can vary by patient. However, some common signs include:

• Pelvic pain: Patients may experience tenderness or discomfort in the pelvic region, sometimes mistaking it for the early stages of a urinary tract infection (UTI).
• UTI symptoms: These may include a burning sensation during urination and increased urgency.
• Ovarian pain: In patients with ovaries, the pain from a kidney stone can sometimes be mistaken for ovarian pain, even if the ovaries are not involved.
• Side/back pain: This is the one symptom that nearly all kidney stone patients experience. It can begin as a minor, dull ache or present as intense, sudden pain. Patients who have had stones before are likely to recognize this pain immediately.

Once symptoms begin, patients should consider consulting their doctor to discuss next steps and begin pain relief. There are various methods available to help manage discomfort until the stone is passed or removed.

Are there risks with CT scans?

There is a small amount of radiation exposure during a CT scan, but it is considered low-risk and generally safe for patients. However, because repeated radiation exposure can slightly increase lifetime cancer risks, patients with recurring kidney stones may be offered alternative imaging options, such as an ultrasound. Pregnant patients will also receive different scanning recommendations to avoid exposing the fetus to radiation. The only other potential risk is for individuals with allergies to contrast agents, which are not used in kidney stone CT imaging.

How much do CT scans for kidney stones cost?

The cost of a CT scan for diagnosing kidney stones can vary depending on your region, insurance coverage and the imaging facility, as prices differ between providers. On average, the out-of-pocket cost is around $625 USD, though this can vary significantly and having a CT scan in an emergency room is typically more expensive. If you have insurance, it’s likely that at least part of the cost will be covered.

 

Take control of your health journey

PocketHealth makes it simple to keep track of your CT scans reports and other medical results. All of your vital imaging is in one secure location and can be accessed online anytime. If needed, reports can also be easily shared with other physicians in your care team, such as your urologist. When used in conjunction with your medical provider’s professional advice, it is a powerful tool for organizing and understanding your imaging results and your health.