Imaging Techniques To Detect Bladder Cancer
Imaging techniques, which include ultrasound, computed tomography (or CT) scanning, magnetic resonance imaging (or MRI) and x-ray approaches, provide an important means of assessing the urinary tract, including the kidneys, and play an important role in the detection, diagnosis, and monitoring of bladder cancer.
Imaging is used in both an exploratory setting when another test suggests an anomaly, or to help confirm a diagnosis. The use of a specific imaging procedure linked to bladder cancer is dependent on a number of factors including other irregular test results, local access and availability, pre-existing medical conditions, the characteristics of a suspected tumour or unusual growth (e.g. size, location), and possible side effects of the procedure.
Irregularities in the upper urinary tract are often assessed with imaging given its accuracy in this setting and an inability to access the region via cystoscopy. In contrast, imaging techniques are less useful for diagnosing tumours in the lower urinary tract. Small and flattened bladder tumours may also be difficult to visualise with imaging.
It’s important to note that imaging is generally used in combination with other bladder cancer diagnostic tests to reach a diagnosis. Cxbladder, a genomic urine test, for example, can be used with imaging to increase overall detection accuracy, and to rule out bladder cancer in low risk patients without the need for further invasive procedures.
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Detecting bladder cancer with ultrasound
An ultrasound (which may also be referred to as a sonogram) uses high frequency sound waves to produce images of internal organs. Echoes, which are created as sound waves bounce off organs and tissues, produce computer images that provide information on the structure and movement of organs and the blood flow through vessels. An ultrasound does not use radiation or contrast dyes.
How do ultrasounds help detect and monitor bladder cancer?
An ultrasound of the urinary tract can help assess the size of a bladder tumour and whether a bladder cancer has spread. Ultrasound is able to differentiate between fluid-filled cysts and solid tumours, however, it cannot determine if a tumour is cancerous. Ultrasound can also be used to guide a biopsy needle to sample a suspected cancer.
Ultrasound scan showing a tumour on the back wall of the bladder.
Can an ultrasound miss bladder cancer?
While bladder tumours may be visualised using ultrasound, a negative test does not exclude the presence of bladder cancer. An ultrasound may also not have sufficient sensitivity to detect small tumours and is unable to detect tumours in some parts of the urinary tract (for example, the ureters).
What to expect with bladder ultrasounds?
Ultrasounds are typically outpatient procedures and usually take 20–30 minutes to complete.
Preparation is often not required ahead of an ultrasound, however, in some instances the patient will be asked to take a laxative, use an enema, or not to eat before the test. Some patients having an abdominal ultrasound may be required to drink a large amount of water so that the bladder is filled, which will improve the quality of the images.
During a bladder ultrasound, the individual is often lying down while the probe is passed over the skin’s surface. A lubricating gel is administered to the skin which helps the sound waves conduct.
Notably, ultrasound is a safe procedure with a low risk of side effects.
Detecting bladder cancer with CT scans
A CT scan uses x-rays to obtain cross-sectional images of the body. Compared to a general x-ray test, which directs a broad x-ray beam from a single angle, the CT scan uses a number of thin beams to produce a series of images from different angles. These images are then digitally reconstructed to create a single image representing a slice of a particular region in the body.
A CT scan of the kidneys, ureters and bladder is referred to as a CT urogram.
How do CT scans help detect and monitor bladder cancer?
A CT urogram can:
- Determine if urinary tract abnormalities are present or if there are enlarged lymph nodes that may contain cancer
- Assess the shape, size, and location of a tumour
- Help to determine the stage of disease
- Be used to guide a biopsy needle to take samples where a bladder cancer is suspected to have spread (which is referred to as CT-guided biopsy)
Computed tomography (CT) scan of the bladder showing bladder cancer (arrow).
Can a CT scan miss bladder cancer?
CT scans can provide important information about the urinary tract and bladder tumours. However, while some bladder tumours may be seen on a CT scan, others may not be apparent, such as smaller or flatter tumours.
What to expect when having a CT scan
A CT scan is a painless procedure that is typically performed on an outpatient basis, taking about 10–30 minutes to complete.
The patient may be told not to eat or drink before the test, and a laxative or enema may be used to clear the bowels so the images are clearer. Some CT scans may be performed using special contrast dyes, which may be swallowed as a liquid, delivered intravenously, or administered with an enema. These contrast agents can help improve the quality of the CT image.
For the test, the individual lies on a flat table that slides through the middle of the scanner. Buzzing and clicking noises may be heard within the scanner. During the test, the patient may have to stay still for several minutes or to briefly hold his/her breath.
Possible side effects of a CT scan
Sensitivity or allergic reaction to the contrast dye can occur in some patients, which may manifest as rash, nausea, wheezing, shortness of breath, or itching or swelling of the face. (Be sure to inform your medical team of any known sensitivities to contrast dyes, seafood, or iodine.) Symptoms are usually mild and clear on their own. Uncommon but more severe manifestations are low blood pressure and breathing difficulties.
Of additional note, while the amount of radiation used in CT scans can vary in clinical practice, CT scans deliver considerably more radiation than a typical x-ray. Therefore, CT scans can carry risks associated with increased radiation exposure, such as radiation-induced future cancer.
Other imaging approaches to detect or monitor bladder cancer
An MRI scan uses radio waves and magnets to produce more detailed pictures of soft tissues. MRI scans can show whether bladder cancer has spread to other tissues or to the lymph nodes. To improve the quality of the images it’s sometimes necessary to administer an intravenous dye.
A type of MRI referred to as an MRI urogram can be used to visualise the urinary tract and may have comparable accuracy to a CT urogram for detecting cancers of the upper urinary tract but with the advantage of not exposing the individual to radiation. As with CT scans, MRIs may not be able to visualise small or flattened tumours in the lower urinary tract.
In an intravenous pyelogram (IVP; also referred to as intravenous urogram or IVU), the patient is given an intravenous (IV) dye. As the dye passes through the kidneys, ureter and bladder, x-rays are used to produce images of the urinary tract organs. IVP may be used to visualise potential bladder or upper urinary tract tumours, which may appear as a blockage or irregular outline on the bladder wall or ureter.
In a retrograde pyelogram, a catheter is inserted through the urethra into either the bladder or ureter. A dye, which is administered through the catheter, helps to visualise the bladder lining, ureters, and kidneys for x-ray imaging. Instead of x-ray, ultrasound imaging may be used (particularly in patients who cannot be exposed to x-rays). Retrograde pyelograms are usually performed in conjunction with a cystoscopy and may provide greater detail of the upper urinary tract in some individuals compared with other approaches.
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Last Updated: 18 Jan 2023 02:39 pm
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