Types of CT Scans | What is a CT Scan

Types of CT Scans

CT Scans

When your doctor wants to get a better look at what is going on inside your body, they will most likely order imaging. Several different technologies exist to diagnose conditions. Depending on the type of imaging and the area of the body, the method used to capture a picture of the inside of the body might be magnetic waves, ionizing radiation, sound waves or radiotracers. Computed tomography (CT) scans use ionizing radiation, or x-rays, to get an image of the inside of the body. Your doctor might order a CT scan if they believe you have a broken bone or if they are trying to detect tumors or other signs of illness in the body.

Learn more about the different kinds of CT scans and what you can expect when you get one.

Intro to CT Scans: What Are They?

Is a CT Scan the Same as a CAT Scan?

CT scans, sometimes called CAT scans, are diagnostic imaging procedures. Your doctor will ask you to get a CT scan if they want to get a better idea of what’s happening inside your body.  CT scans use the same imaging method as x-rays — ionizing radiation — but can capture images x-rays cannot. An x-ray captures a two-dimensional picture of a structure inside the body, such as a person’s bones. A CT scan produces a three-dimensional image. The images captured by a CT scan provide a doctor with a clearer view of a patient’s inner organs, blood vessels and soft tissues than a traditional x-ray.

CT Scan Machine

During a CT scan, a patient lies on a table, which slides into a large tube. The tube contains an x-ray machine that takes photos of the inside of the body. Usually, the entire process takes about 15 minutes and is painless. The pictures taken during the scan get sent to a computer. A technologist can assemble the photos to create a 3D image to give to the doctor. It’s also possible for a physician to evaluate the images separately.

What Are the Different Kinds of CT Scans?

The type of CT scan your doctor orders will depend in large part on the area of the body they want to evaluate. Some kinds of CT scan procedures include the following.

• CT angiography: A  doctor might order a CT angiography, or angiogram, if they want to assess a person’s risk of heart disease. The scan can also help doctors detect damage to the blood vessels, such as aneurysms or blockages. Before the scan, a health professional injects dye into the blood vessels to help make the flow of blood through the body more visible. A CT technologist then takes images of the blood vessels.
• CT abdomen scan: During an abdominal CT scan, a technologist will capture images of the organs of the digestive tract, such as the intestines, colon, liver, spleen and appendix. A doctor might order an abdomen scan to detect abscesses in the area, to discover internal bleeding or to identify and diagnose tumors, such as those in the colon.
• CT bone scan: While an x-ray can detect a fracture or other problem with the bones, health care professionals also sometimes use a CT scan of the bones. Since a CT scan can give more information to a doctor, they might order one if the results of a traditional x-ray are inconclusive. A CT bone scan will also provide a clearer picture of the soft tissues near the bones, such as the tendons and muscles. A CT bone scan might also help diagnose cancer in the bones.
• Head CT: A doctor might order a head CT for a patient who is experiencing unexplained headaches or dizziness. The procedure can also help diagnose brain tumors or strokes. A head CT captures images of the brain and other areas of the head, such as the sinuses. Patients with ongoing sinus issues might benefit from a head CT to determine if there is ongoing inflammation in the area.
• CT scan chest/lungs: A CT scan of the chest can provide a doctor with detailed images of a person’s lungs. Doctors might order the scan if a patient complains of having trouble breathing or of having chest pain. The images can help doctors diagnose conditions such as lung cancer, pneumonia, tuberculosis or excess fluid in the lungs.
• Cardiac CT: A  cardiac CT scan also takes pictures of the chest area. However, the focus is not on the lungs, but on a person’s heart. A doctor might order a cardiac CT to detect problems with the aorta, heart valves and other arteries. In some cases, a doctor might order a cardiac CT scan to follow up on the results of a procedure, such as coronary artery bypass grafting.
• CT neck: A CT scan of the neck typically captures images of the area from the base of the skull to the top of the lungs. The scan can detect and diagnose tumors or masses in the neck, on the tongue, on the vocal cords or in the upper airway. A doctor can also detect growths or abnormalities on the thyroid gland or issues with the carotid artery using a neck CT scan.
• Pelvic CT scan: A pelvic CT will take pictures of the area inside the body between the hipbones. It can help diagnose issues with the male or female reproductive systems or to identify bladder problems, such as bladder stones or tumors.
• CT scan kidneys: A common reason for a CT scan of the kidneys is to detect and confirm the presence of kidney stones. The scan can also help identify tumors, abscesses and signs of kidney disease.
• CT scan of the spine: Spinal CT scans capture images of the bony spinal structure, the discs between the bones and the soft tissue of the spinal column. A CT scan of the spine can help a doctor assess injury to the area, diagnose herniated discs and evaluate the area before surgery. In some cases, a doctor might use a spinal CT to gauge bone loss in the area as a result of osteoporosis. A CT scan of the spine can also be an aid during a biopsy or other procedure.

CT Scan With or Without Contrast

Some types of CT scans require the use of a special chemical called contrast, which helps make soft tissue easier to see on the images. Although you might have heard contrast called a dye, it doesn’t change the color of the organs or soft tissues inside the body. Instead, it works by blocking the x-rays. Contrast looks white on the images, making the organs or other tissues stand out.

Not all types of CT scans require contrast. Your doctor will let you know if yours does before you schedule it. Since some people are allergic to the ingredients commonly used in contrast, such as iodine or barium, it’s crucial to tell your doctor about any known allergies before they schedule the scan.

There are different ways of receiving contrast before a scan. You might get it intravenously, through an injection. Your technologist might also give you something to swallow. If you are going to have contrast before a CT scan, you won’t be able to eat or drink anything starting several hours beforehand.

Schedule Your CT Scan in Denver, Colorado, Today

Health Images takes a patient-centric approach to imaging. Whether you need a CT scan with or without contrast, we’ll take the time to explain the process to you and help you feel relaxed and comfortable throughout. We have multiple facilities in and around Denver, Colorado, for your convenience. Find the location nearest you and reach out today to learn more about opening hours, appointments and what you can do to prepare for your CT scan.

Call To Schedule Your Appointment

Sources:

1. https://www.envrad.com/services/ct-scans/
2. https://www.envrad.com/difference-between-x-ray-ct-scan-and-mri
3. https://blog.radiology.virginia.edu/different-imaging-tests-explained/
4. https://medlineplus.gov/ctscans.html
5. https://www.radiologyinfo.org/en/info.cfm?pg=angioct
6. https://ipmcmed.com/radiology/ct-scan/types-of-ct-scan/
7. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/computed-tomography-ct-or-cat-scan-of-the-abdomen
8. https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=92&contentid=P07649
9. https://www.radiologyinfo.org/en/info.cfm?pg=headct
10. https://www.mayoclinic. org/tests-procedures/ct-scan/about/pac-20393675
11. https://stanfordhealthcare.org/medical-tests/c/ct-scan.html
12. https://www.nhlbi.nih.gov/health-topics/cardiac-ct-scan
13. https://www.nhlbi.nih.gov/health-topics/chest-ct-scan
14. https://www.cedars-sinai.edu/Patients/Programs-and-Services/Imaging-Center/For-Physicians/Neuroradiology/CT-Neck.asp
15. https://medlineplus.gov/ency/article/007362.htm#
16. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/ct-scan-of-the-kidney
17. https://www.radiologyinfo.org/en/info.cfm?pg=spinect
18. https://medicine.yale.edu/diagnosticradiology/patientcare/physicians/er/contrastquestions/
19. https://www.radiologyinfo.org/en/info.cfm?pg=safety-contrast
20. https://www.healthimages.com/locations/

CT Scan (Cat Scan) for Cancer Detection & Treatment

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science.

This page was updated on March 2, 2022.

Your doctor may order a computed tomography (CT) scan, which is also known as a computed axial tomography (CAT) scan and a spiral or helical CT. The different names all mean the same thing.

• A CT scan is an X-ray study that uses a computer to produce 3D cross-sectional images of the body.
• The CT scanner obtains detailed pictures of internal organs, bones and soft tissues—and differs from a medical X-ray image in that it uses a doughnut-shaped machine to emit X-ray beams at different angles.
• Some CT scans require a contrast or dye to be injected to get clearer images. In this case, your doctor will order a CT with contrast.

Can a CT scan detect cancer?

A CT scan, like any imaging tool, cannot detect cancer, though it may be useful in helping to identify a mass and determine its location and size. A CT scan may also offer valuable information, such as its shape and possible makeup (e. g., solid vs. liquid), that suggests the mass may be cancerous, but only a pathology review of tissue under a microscope following a biopsy can definitely determine a cancer diagnosis.

What does a CT scan show?

A CT scan can show whether you have a tumor—and, if you do, where it’s located and how big it is. CT scans can also show the blood vessels that are feeding the tumor. Your care team may use these images to see whether the cancer has spread to other parts of your body, such as the lungs or liver. The images are black and white.

It’s important to note that some cancers may be overlooked on a CT scan. Lesions may be missed for a variety of reasons, including location and human error. Still, CT is more sensitive than a simple X-ray.

A CT scan can find lesions as small as 2-3 mm. However, the location of the tumor may play a role in how big it must grow before it’s visible.

Compared to traditional X-rays, CT scans can provide more information about the size of suspicious nodules and how harmful they may be. They can be especially helpful when performed with an injection of material called contrast. Contrast is used to make certain tissues more visible. Cancer cells take up the contrast, which makes them appear white on the scan. This in turn allows your radiologist to better interpret the images, which is important when making a diagnosis. He or she will also be able to more clearly see tissues surrounding a potentially cancerous lesion, including nearby organs.

A CT scan with contrast may also be used to help determine treatment. For instance, using contrast can help tell whether the cancer can be removed with surgery.

Types of CT scans

3D CT

3D CT pinpoints the location of tumors and can determine whether the cancer has spread to other parts of the body, and assesses the effects of treatment.

Advantages may include:

• Providing more detailed images than those from magnetic resonance imaging (MRI) or ultrasounds 
• Most 3D scans take less than 10 minutes

3D CT angiography

CT angiography (CTA) highlights the blood vessels of tumors and notes other abnormal blood vessels that may be a health concern.

Advantages may include:

• Less invasive evaluation of blood vessels than catheter angiography
• Capturing 3D images of almost every blood vessel in the body, as well as the brain, heart, lungs, pelvis, abdomen and extremities
• The scan itself is quick, about 20 minutes, though the procedure may take a few hours from start to finish.

Large bore CT scanner/radiation therapy (RT) with simulation

This health-care tool produces detailed images of areas inside the body for planning radiation therapy. It uses simulation, fluoroscopy and respiratory gating to plan and deliver radiation.

Advantages may include:

• Locating abnormalities and guiding precision radiation therapy
• Planning for treatment options based on a patient’s breathing patterns
• Allowing for varying patient sizes and positioning
• Spending 15 to 30 minutes for the session, including the time it takes to put you in position and set up the equipment  

Multi-detector CT scanner

This scanner provides multiple image slices in one rotation, allowing radiologists to view high-quality images in micro-level detail and faster. The CT machine’s wide scanning space makes it a more comfortable experience for the patient. Depending on the body part, this scan can be done in 10 to 30 minutes. If you need to be given contrast before your scan, it may take longer to set up.

PET/CT scan

This nuclear imaging technique uses both positron emission tomography (PET) and computerized tomography (CT), providing detailed information about the structure and function of cells and tissues in the body. The patient receives a glucose injection that has a small amount of radiation as a contrast agent. The radiation dose is absorbed by the organs or tissues being examined, making them visible in medical imaging. The radiation exposure from this procedure is minor.

Advantages may include:

• Locating damaged or cancerous cells where the glucose is being abnormally absorbed (cancer cells often use more glucose than normal cells)
• Determining the response to therapy by measuring the rate at which the tumor is using the glucose
• Providing a more detailed image of cancerous tissues than either test is able to do on its own
• Capturing both forms of diagnostic imaging in one scan
• Spending about 20 minutes for the PET/CT scan (still, plan on extra time for prep and discharge) 

How is a CT scan performed?

A patient lies on a table that slides into the CT scanner, where an X-ray tube rotates around the patient. A technologist may inject a contrast material, usually an iodine contrast dye, into a vein in the arm for even more detailed CT images. Many abdominal and pelvic exams also require drinking a liquid to opacify the GI tract. This painless outpatient procedure typically takes about 10 minutes.

What to expect during a CT scan

Before the scan

• Wear comfortable clothing. The technologist may ask you to change into a medical gown.
• Remove metal objects such as jewelry, eyeglasses, dentures and hairpins. If you have piercings, remove them as well.
• If you’re getting contrast, you may be asked to not eat or drink a few hours before the scheduled exam.
• If you’re on medications, ask your doctor whether to take them before the exam.
• If you have allergies, ask if there are medications to reduce the risk of a reaction to the contrast.
• If you have other medical conditions, such as diabetes, heart disease, asthma, kidney disease, thyroid problems, or may be pregnant, tell your care team.

During the scan

• A noninvasive procedure, a CT scan requires nothing to break the skin or enter the body. However, sometimes your doctor orders a CT with contrast dye to highlight specific areas of the body. In that case, the contrast agent may be injected into a vein or given orally or by enema.
• You may be asked to hold your breath, so you don’t move and blur the images. You’re not enclosed like you are in an MRI machine, so it’s unlikely you’ll feel claustrophobic.
• Most CT scans take anywhere from a few minutes to a half-hour and are available in different settings—whether that’s in the radiology department of a hospital or at an outpatient imaging facility.
• CT scans are typically painless and easy, but if you’re given contrast through an intravenous (IV) line, you may experience slight discomfort at the injection site.
• You may be asked to wait a few minutes for the technologist to check that the images are of the quality needed for an accurate interpretation.

Why is a CT scan used for cancer?

CT scans play many different roles in the diagnosis and treatment of cancer.

• Screening: CT is sometimes used to screen for different types of cancer, such as lung and colorectal cancer.
• Diagnosis: Your doctor may order a CT scan to locate and size suspected tumors. It also may help determine whether a tumor has recurred.
• Planning and treatment guide: A CT scan may help your doctor identify and locate the tissue that needs to be biopsied. It may also be used to guide treatments such as cryotherapy, microwave ablation and the implantation of radioactive seeds, or to plan surgery or external-beam radiation.
• Treatment response: Sometimes doctors order a scan to see whether a tumor is responding to treatment.
• Tool for monitoring for other diseases: CT scans may be necessary to look for other conditions that may or may not be related to cancer, including:
  • Abnormal brain function
  • Coronary artery disease
  • Blood vessel aneurysms
  • Blood clots
  • Bone fractures
  • Emphysema or pneumonia
  • Kidney and bladder stones
  • Inflammatory diseases, such as ulcerative colitis and sinusitis
  • Injuries to your head or internal organs

Your treatment and type of cancer will determine how often you need to undergo follow-up with CT. For example, it’s recommended that patients treated with surgery for colorectal cancer have two CT scans within the first three years. If you’re between 55 and 74 years old and have a history of smoking an average of a pack a day for 30 years (even if you quit in the past 15 years), the American Cancer Society recommends you undergo a low-dose CT scan every year to monitor for lung cancer.

Side effects and risks with CT scan

As with any medical procedure, you and your doctor must weigh the risks and benefits.

The information your doctors may get from a CT scan may be critical to diagnosing and treating your cancer. Possible risks include:

Radiation. CT scans use low-level ionizing radiation. While it’s more radiation than emitted from an X-ray, it’s still low. Still, some concerns have been raised over whether even small doses of radiation from imaging may cause cancer. In most cases, the information obtained from the scan far outweighs the minimal risks of the radiation used. While the chance of CT scans causing cancer is small, several medical societies and government agencies have adopted guidelines and programs aimed at reducing this risk. 

Allergic reactions. Though it’s rare, sometimes people have allergic reactions to the contrast agents. You may experience itching or hives. If you have a serious allergic reaction, where you experience shortness of breath and your throat swells, alert the technologist immediately so that you may be treated promptly.

Kidney function. If your kidneys are impaired in any way, the contrast dye may make it worse. About 2 percent of patients who are given dyes develop contrast induced nephropathy (CIN), according to the National Kidney Foundation. CIN may cause fatigue, swelling of the feet and ankles, and dry, itchy skin. CIN also may lead to serious kidney and heart problems.

Contraindications

You may not be a candidate for a CT scan if you:

• Are obese (usually more than 450 pounds)
• Are pregnant 

Benefits of CT scans

• The procedure is fast, simple, painless and accurate.
• CT scans provide a wealth of information: Your doctors may see bone, soft tissue and blood vessels with one scan. They also get very detailed images of your tissues and organs.
• Unlike MRI, CT scans may be performed on patients with implanted medical devices of any kind.
• The information from a CT scan may eliminate the need for surgery or biopsy.
• While it provides some radiation, no radiation remains in the body afterward.
• A CT scan may be used to guide minimally invasive procedures such as needle biopsies and needle aspirations in areas of the body such as the lungs, abdomen and pelvis.

What do the results mean?

A radiologist analyzes your scans and sends a report to the physician who ordered the exam. Your doctor then discusses the results with you.

Depending on what’s found, the radiologist and your doctor may recommend additional or different imaging exams.

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The doctor assesses how successful the operation was and plans further
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CT is indispensable in diagnosis:

Neoplasms – benign, malignant, metastases:

• Brain
• Internal organs: lungs, liver, pancreas, kidneys, spleen
• Bones
• Joints

Injuries – isolated and combined injuries:

• Spine
• Bones of the vault and base of the skull
• Chest
• Belly
• Limbs

Pathologies of the nervous system

• Strokes
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• Tumors
• Hydrocephalus
• Edema and atrophy of the brain
• Brain abscess
• Spinal cord compressions

Heart diseases

• Defects
• Camera extensions
• Scars after a heart attack
• Aneurysm
• Thrombus
• Tumors

Urological pathology

• Kidney and bladder stones
• Tumors of the genitourinary system
• Abnormalities of renal hypoplasia hydronephrosis, ectopic ureters

Vascular diseases

• Thrombosis
• Emboli
• Aneurysm
• Portosystemic shunts
• Development Options

Orthopedic diseases

• Fractures and fractures of bones
• Joint injuries
• Areas of bone destruction and sclerosis
• Herniated and protrusion of the intervertebral discs
• Arthritis and arthrosis

Anomalies of the body

• Malformations of the spine, joints, abdominal organs, urogenital
  systems

You are looking for answers to these questions:

X-ray

• Suitable for primary diagnosis
• Only gross deviations are visible in the images
• Displays an image in one plane
• In the images, the shadows of organs and tissues are superimposed on each other, slight
  changes are not visible.

CT

• Indispensable for a quick definitive diagnosis
• On the tomograms, lesions from 0.6 mm are visible
• Produces dozens of images in various planes and modes – for bones,
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• Duration of the procedure – several minutes
• Radiation exposure reduced by 68%
• Areas of the body not to be examined are covered with special screens
• For sedation during the study, use lower doses of drugs,
  than for operation

• To exclude contraindications, the animal is examined before the procedure
• The doctor constantly monitors the condition – conducts an examination before the procedure,
  administers medications and monitors the animal until waking up
• All manipulations are carried out quickly and accurately

Indications and contraindications

Indications:

• Polytrauma – head, chest, abdomen, spine, limbs,
• Suspicion:
• • hemorrhage
  • “acute abdomen”
  • neoplasm
  • thrombosis and thromboembolism
  • the presence of foreign bodies, including those not visible on radiographs,
• Search for neoplasm metastases
• Bone and joint deformities
• Movement disorder
• Planning for complex bone and joint surgery

Contraindications:

• Conditions where anesthesia is contraindicated
• Renal failure for contrast administration

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pancreas – scientific articles on animal veterinary medicine

VD Alferova veterinary doctor, expert in ultrasound imaging of the ITC MVA.

Translation original articles Elizabeth Huynh DVM, Clifford R. Berry DVM, DACVR, University of Florida “ Abdominal Ultrasonography: The Pancreas” .

The pancreas is a lobed, thin, elongated organ that is divided into three parts: the right lobe, the left lobe and the body. It is one of the most difficult structures to identify in a healthy patient due to the similar echogenicity and echostructure of the pancreas and adjacent mesentery and fat.

Knowledge of anatomical landmarks is key to identifying the normal pancreas and should allow at least visualization of the area where the pancreas should be located if the pancreas cannot be directly visualized. There are anatomical differences between a dog and a cat.

Patients with pancreatitis often have severe epigastric pain and resist the transducer pressure required to visualize the region of interest. Therefore, if necessary, appropriate sedation and analgesia should be used to improve image quality and diagnostic accuracy.

Right lobe

The right lobe is the largest lobe in dogs and is located parallel and caudal to the descending duodenum. This lobe can be examined from the ventral or lateral approach. When using the ventral approach, the transducer is placed to the right, medial to the 13th rib, and tilted dorsally and cranially to obtain a long-axis view of the right kidney. We direct the sensor medially, display the descending duodenum. Moving the probe medially to the descending duodenum allows you to explore the location of the right lobe of the pancreas (FIG. 1).

FIGURE 1. Long axis parasagittal image of the right lobe of the pancreas (calipers) in an 8-year-old dog. The pancreas is slightly hyperechoic (usually iso- or hypoechoic) relative to the surrounding mesentery.

In the dog, the pancreaticoduodenal vein may be an anatomical landmark for visualizing the right lobe of the pancreas adjacent to the duodenum. To obtain a cross-sectional image of the right pancreas, the duodenum is first examined in the long axis, then the transducer is rotated 90 degrees to obtain a cross section of the duodenum, and the right lobe will be visible as a triangular structure directly adjacent to the duodenum (FIG. 2).

FIGURE 2. Cross-sectional CT image at the level of the cranial descending duodenum in a dog (dorsally – at the bottom of the image, right side of the patient in the left image) (A). The right lobe of the pancreas (white arrow) is visualized as a triangular structure along the dorsal surface of the descending duodenum (DD), and the left lobe of the pancreas (#) is to the right of the lesser curvature of the stomach. Transverse ultrasound image at the level of the right kidney (RK) in the same dog as in Figure 1. The descending duodenum (DD) in cross section and the right lobe of the pancreas presenting a slightly hyperechoic triangular structure to the right (medial) of the descending duodenum (B). The pancreatoduodenal vein is seen as a rounded anechoic structure between the duodenum and pancreas. ST – stomach; CA – caudate lobe of the liver.

In cats, the right lobe runs along the descending duodenum and then makes a hooked curve (FIG. 3). The right lobe of the pancreas and descending duodenum are closer to the midline in cats than in dogs.

FIGURE 3. B-mode longitudinal (sagittal) image of the region medial to the descending duodenum in a normal cat. The edge of the right lobe (RP) of the pancreas can be observed to be curved in the cranial direction (white arrow), forming a hook. The pancreas is hypoechoic relative to the surrounding mesentery and is 5 mm thick at its widest point. RK – right kidney.

Left lobe

In dogs, the left lobe is located to the left of the midline, near the cranial pole of the left kidney, rarely reaching the level of the hilum of the spleen. The left lobe is closely connected with the greater curvature of the stomach and is located in the area bounded cranially by the stomach, caudally by the transverse colon, and in the near field by the body of the spleen; closely related to the vessels of the portal system related to the spleen. (FIG. 4).

FIGURE 4. Sagittal reformatted CT scan of the dog’s abdomen (cranially on the left side of the image, dorsally on the bottom of the image) (A). Long axis ultrasound scan of a cat’s abdomen (B). In both images, the portal vein (PV) is located dorsal to the pancreas (white arrow). ST- stomach; GB – gallbladder; CVC – caudal vena cava; LI – liver.

In a cat, the left lobe of the pancreas is larger than the right lobe and ends close to the hilum of the spleen (FIG. 5).

FIGURE 5. Transverse ultrasound scan of the cat’s left epigastrium caudal to the stomach (ST): Long axis representation of the left lobe of the pancreas (LP) along the image. The left lobe of the pancreas is intact, 4 mm thick (white arrows), and hypoechoic relative to the surrounding mesentery; the mesentery is also not changed. The spleen is located out of the scanning plane to the right of the image.

Body

The body of the pancreas is located in the area where the right and left lobes join together; immediately ventral to the portal vein and common bile duct. Sometimes the pancreatic duct is visualized as two thin hyperechoic lines at a distance of 1 mm from each other, which are located in the center of the pancreas.

Unlike dogs, in cats, the body of the pancreas, as well as the pyloroduodenal junction, are located closer to the midline (FIG. 6).

FIGURE 6 . Dorsal CT scan of the abdomen and caudal thorax of a cat with a chylous pleural effusion (PE) (cranial – at the top of the image, patient’s left side – on the right image) (A). The body and left lobe of the pancreas (red arrows) are located ventral to the portal vein (PV). Oblique scan in a cat: long axis image of a hypoechoic left lobe of the pancreas (white arrows), the surrounding mesentery is hyperechoic (B). The pancreas is 6 mm thick and the pancreatic duct (PD) diameter is 1.7 mm, both measurements are considered normal for a cat. ST – stomach; SP – spleen; PV – splenic part of the portal vein dorsal to the left lobe of the pancreas.

Ultrasonographic features in normal

Adequate ultrasound imaging of the pancreas is highly dependent on operator skill and knowledge of regional anatomy. The pancreas is an elongated organ that is identified using various anatomical landmarks: the body is located at the pyloroduodenal junction, immediately ventral to the portal vein; left lobe – caudal to the greater curvature of the stomach; the right lobe is located in the mesoduodenum in the dog (FIG. 7).

FIGURE 7. Dorsal CT scan of the dog’s abdomen showing the body, right and left lobes of the pancreas. The pancreas is a horseshoe-shaped structure, indicated by the white arrow. ST – fundus of the stomach; PY, pyloric antrum; DU – duodenum; TC – transverse colon.

Patient related factors also play a role in ultrasound imaging. Excessive aerophagy and disruption of the starvation diet often result in significant distortion due to the appearance of shadows and reverberation artifacts from the contents of the stomach. These artifacts obscure the region of the left lobe and body of the pancreas, making assessment of these structures difficult or impossible, especially in dogs. Normally, the pancreas, if visualized, is iso- or slightly hypoechoic relative to the surrounding mesentery. The borders of the pancreas are outlined by thin hyperechoic lines.

• In dogs, the pancreas is 6-8 mm thick with a duct diameter of 0.6 mm.
• In cats, the pancreas is 4-6 mm thick, with a duct diameter of 1 mm.

Age related changes

As cats age, pancreatic duct diameter can reach 2.5 mm without evidence of pancreatic disease (FIG. 8).

FIGURE 8. Dilated pancreatic duct (PD) in an elderly cat without clinical or biochemical evidence of pancreatic disease. The pancreas is hypoechoic relative to the surrounding mesentery; the thickness of the pancreas is 7 mm. duct diameter 2.2 mm; measurement is within normal limits in a geriatric cat.

In addition, in older cats, and more rarely in dogs, nodular (focal/nodular) hyperplasia may be observed with focal hypoechoic lesions (3-10 mm) visualized in the pancreatic parenchyma (FIG. 9).

FIGURE 9. Transverse scan of the left epigastrium of an older cat: the left lobe of the pancreas with nodular hyperplasia is depicted in the long axis. Note the indistinct jagged edges of the pancreas and hypoechoic lesions in the parenchyma. Histologically, these are areas of nodular hyperplasia. PD – pancreatic duct; PV – splenic part of the portal vein.

Occasionally, the pancreas may be diffusely hyperechoic but normal in thickness (Figures 1 and 7). Histopathology in dogs with a hyperechoic pancreas revealed normal parenchyma and fibrosis, the appearance of which is probably associated with previous pancreatitis.

Pancreatitis

The most common pathology of the pancreas in cats and dogs is pancreatitis. Pancreatitis can have various ultrasound manifestations depending on the severity, extent and duration of pancreatic and parapancreatic changes. Detection of pancreatitis on ultrasound can be difficult, as the pancreas may appear normal ultrasonographically. A normal appearance of the pancreas does not rule out pancreatitis.

In acute pancreatitis, the pancreas may become enlarged, hypoechoic, and have rounded or irregular edges.

Surrounding mesenteric fat becomes hyperechoic with signal attenuation; in the area of ​​the inflamed pancreas (parapancreatically) (FIG. 10) there is often a small to moderate echogenic effusion that represents peritonitis and/or fat saponification. Saponification of fat (saponification) is also called steatitis.

FIGURE 10. Acute pancreatitis in a dog: a large hypoechoic mass (PA) with irregular, indistinct margins, surrounded by a hyperechoic mesentery (ME) associated with fat saponification and peritonitis (A), is seen in the middle and far fields. Doppler examination revealed no blood flow in the mass, which corresponds to necrosis. Pancreatitis in a cat: the pancreas (PA) is enlarged, anechoic, with uneven fuzzy contours; the mesentery surrounding the pancreas (ME) has increased echogenicity (B). Changes correspond to local peritonitis and steatitis, which is associated with inflammation of the pancreas. In the area caudal to the inflamed pancreas and mesentery, there is attenuation of ultrasonic waves (AT), secondary to acute local steatitis.

Saponification of parapancreatic mesenteric fat results from local release of pancreatic enzymes and can cause multifocal areas of dystrophic mineralization around the pancreas, which are small hyperechoic structures with echoes (FIG. 11).

FIGURE 11. Dystrophic mineralization (white arrows/MI with distal acoustic shading) in areas of prior fat saponification due to pancreatitis in a dog. The lumen of the descending duodenum (DD) is dilated with liquid content – obstruction (ileus) associated with the current attack of pancreatitis. PA – pancreas; PV – portal vein.

The wall of the duodenum and/or stomach may be thickened due to secondary inflammation of this area. There may be local paralytic ileus and corrugation of the walls of the duodenum (FIG. 12). The differentiation of wall layers is reduced, but there is no complete loss of layers, as in neoplastic processes of the stomach and duodenum. Rarely, the colon (ascending or transverse) may be involved.

FIGURE 12. Corrugation of the descending duodenum in a dog with pancreatitis in the right lobe. The duodenum is corrugated due to inflammation of the area around the gland. The mesentery surrounding the duodenum is hyperechoic as a result of focal steatitis and peritonitis.

In some dogs and cats, ultrasound results lag behind clinical signs, and the initial ultrasound may not be abnormal. Conversely, a repeat ultrasound scan may reveal major changes while the patient is clinically well and no longer has anorexia. In addition, pancreatitis can be caused by a pancreatic tumor, so repeat ultrasound 2 weeks after pancreatitis may be useful in older patients to evaluate neoplastic processes.

In cats, pancreatitis is often associated with hepatic lipidosis, inflammatory bowel disease, and cholangiohepatitis. The presence of inflammatory bowel disease, cholangiohepatitis, and pancreatitis at the same time is a common symptom complex of feline triaditis; therefore, the gastrointestinal tract and liver should be carefully examined in cats with pancreatitis.

In cases of necrotizing pancreatitis, hypo- or anechoic areas in the parenchyma may be identified – areas of hemorrhage and necrosis. It is recommended to use color or power Doppler to assess blood flow in affected areas of the pancreas to rule out necrotizing pancreatitis. Motion artifacts often make accurate Doppler examination difficult in patients with epigastric pain.

Possible complications of pancreatitis include pancreatic cysts (retention or pseudocysts) and abscesses. Cystic lesions of the pancreas are rounded, anechoic structures with distal enhancement artifact; however, it is not possible to differentiate between congenital cysts, pseudocysts associated with cavitation from pancreatitis, and retention cysts associated with duct obstruction.

The appearance of a pancreatic abscess is similar to the appearance of other intra-abdominal abscesses. Abscesses are associated with a distal acoustic shadow, in addition, they can have a thick inhomogeneous wall, which is associated with inflammation along the periphery from the pathological focus (sharply hyperechoic fat and effusion), and can also show a reverberation artifact in case of gas release by anaerobes.

Another common consequence of pancreatitis is extrahepatic obstruction of the common bile duct, leading to dilation of the common bile duct, cystic duct, gallbladder, and ultimately the extra- and intrahepatic bile ducts (FIG. 13).

FIGURE 13. Pancreatitis leading to extrahepatic bile duct obstruction in a dog. The bile duct (BD) is abnormally dilated, secondary to inflammation of the pancreas at the level of the bile duct’s entry into the duodenal papilla (not shown in this image). There is a marked increase in the right lobe of the pancreas with a mass effect (MA) relative to the body of the pancreas (PA).

In chronic pancreatitis, the pancreas may be hyperechoic or heterogeneous (hyper- and hypoechoic areas) and thickened with inflammatory changes in the parapancreatic area.

Cats with chronic pancreatitis develop dilatation of the pancreatic duct, although, as mentioned above, dilatation is normal in older cats.

Non-inflammatory pancreatic edema

In dogs and cats with hypoalbuminemia or portal hypertension, pancreatic edema may be present. The accumulation of fluid in the interlobular septa of the pancreas appears ultrasonographically as the presence of anechoic areas that divide the pancreas, leading to the appearance of characteristic “tiger stripes”.

Neoplasia

It may be difficult to differentiate pancreatic neoplasia from abscesses, necrosis, and acute pancreatitis. Pancreatic neoplasia can be exocrine (eg, adenocarcinomas) and endocrine (eg, beta cell tumors or insulinomas). Differentiation between pancreatic neoplasia and nodular hyperplasia is difficult because they have similar ultrasonographic characteristics. However, a single lesion greater than 2 cm in diameter is most likely neoplastic, while nodular hyperplasia usually presents as multiple, small, hypoechoic nodules. Adenocarcinomas may appear as hypoechoic or heterogeneous masses without signs of parapancreatic inflammation. These formations develop inside the body of the pancreas; they can compress the common bile duct, invade adjacent gastrointestinal structures, and often metastasize to the liver (there, the nodes may be target-like, with a hypoechoic periphery and an iso- or hyperechoic center). The mass may have dystrophic mineralization associated with the tumor.

Signs of malignant pancreatic neoplasms include lymphadenopathy and metastases to other abdominal organs, mesentery, and peritoneal surfaces (carcinomatosis). In the case of carcinomatosis, hypoechoic nodules will be observed along the parietal and visceral peritoneal surfaces (FIG. 14).

FIGURE 14. Hypoechoic pancreatic mass (MA), 2 x 4 cm in size in a cat, pancreatic adenocarcinoma was diagnosed by TIB (A). Multiple hypoechoic nodules (No) on the visceral surface of the mesentery (ME) (B). A small amount of peritoneal effusion (EF) is present in this image.

Other tumor types reported in dogs and cats include cystadenoma, metastatic carcinoma, and lymphoma. More rarely, endocrine tumors (eg, insulinoma) occur as hypoechoic nodules or masses in the pancreatic parenchyma. By the time an insulinoma is accurately diagnosed, metastasis has most often already occurred, and in these cases, careful examination of the regional lymph nodes and liver is necessary to detect metastatic lesions. Lymph nodes with metastases will be enlarged and hypoechoic. As with pancreatic carcinoma, insulinoma metastases can form hypoechoic masses or targets in the liver parenchyma (FIG. 15).

FIG. in the long axis) in an older dog (B). TIAB from foci in the pancreas and liver revealed a metastatic neuroendocrine tumor consistent with insulinoma. ST – stomach.

Summary

Systematic examination of the pancreas based on normal anatomy is a routine part of a full abdominal scan.