Download Imaging of the Abdomen: CT, Ultrasound, and MRI

GI2 #15
2/25/04 11am
Dr. Caffrey
K. Stancoven for J. Brace
Page 1 of 7
Imaging of the Abdomen: CT, Ultrasound, and MRI
Dr. Caffrey said that we won’t have to interpret any images on the exam. Since most of the power points in
her lecture were some sort of imaging picture, I would recommend also reading (or looking) at her notes in
the syllabus. She also said looking at her syllabus would be a good idea. For all the slides that follow, I will
note the ones on which she made comments on. Some images she flipped through without looking at them.
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Approach to Patient
o History, Physical Exam
o Pertinent Laboratory Exams
 Blood tests, CBC, etc…
o Most Appropriate Imaging Exam If Needed for Stable Patient
 An unstable patient must be made stable before any imaging
 By using history, physical exam, and lab tests, you should be able to come up
with a differential diagnosis. Use imaging to rule out & confirm diagnoses.
Imaging modalities
o Ultrasound (US)
o Computed Tomography (CT)
o Magnetic Resonance Imaging (MRI)
Ultrasound
o Patient examined at bedside, CCU, ICU, or in Radiology Department
o Hand held transducer -- Real-time images
o No ionizing radiation
 Preferred for women of child bearing age (especially if pregnant) and young
children
o Requires only momentary breatholds by patient
 Good for patients who can’t lie still (kids)
Computed Tomography
o Patient required to stay motionless on the CT table
o Ionizing radiation used
 Try not to use on pregnant women unless absolutely necessary
o Most exams require oral and IV contrast for optimum imaging
 Only the rare CT doesn’t need contrast
Magnetic Resonance Imaging
o Patient required to stay motionless on the MR table
 Can also ask patient for breatholds
o MRI contraindicated for some patients
 Metal devices, pacemakers (more on last slide at end of notes)
o Premedication may be needed for claustrophobic patients
o No ionizing radiation used
 Also not for use in pregnancy unless necessary (especially in 1 st trimester)
o IV contrast needed for some exams
 Uses different contrast than CT contrast
CT Abdomen and Pelvis
o CT is the “workhorse” of abdominal imaging
o Usually done at initial exam
o Radiologist flips through images to make diagnosis
 Start at diaphragm, and then move towards feet
 Have to know anatomy very well
o There are 13 CT images in the next 13 power points, Dr. Caffrey went through each at
talked about the abdominal organs (she just pointed them out)
 The 2nd to last slide shows a male pelvis, the prostate is visible in the midline
(making the patient male)
GI2 #15
2/25/04 11am
Dr. Caffrey
K. Stancoven for J. Brace
Page 2 of 7
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The last slide shows a female pelvis, showing the uterus in the midline
 Dr. Caffrey pointed out that ultrasound is the best imaging modality for
viewing the female pelvis organs
RUQ Pain/Abnormal Liver Function Tests (LFT’s)
o Gallstones
o Biliary ductal obstruction
o Primary or metastatic hepatic mass (cancer)
o Fatty liver
 Usually not painful, just alters LFT’s
o Cirrhosis of the liver
o Hepatic or Subphrenic Abscess
o Liver laceration due to trauma
Gallbladder Ultrasound
o US is best for viewing the gallbladder and gallstones
o Stones may be missed on CT because the stone may not be calcified yet
o The first US image shows a gallstone in the neck of the gallbladder
o The 2nd image shows a gallstone in the lumen of the gallbladder
 Since US is “real-time,” you can see the stone freely moving inside the lumen
while performing US
CT Gallstones
o See stones when they are calcified
o Stones have a rim of calcification with a cholesterol core
Ultrasound Biliary Ducts
o US best to see ductal dilation and easier to see what is causing the obstruction
o The 2nd image: CBD (common bile duct) & PV (portal vein)
 The CBD is better seen on US due to its oblique orientation
CT Biliary Ducts
o You can see dilation of the bile ducts in the liver
o You may or may not see the obstruction that is causing the dilation
Ultrasound Pericholecystic Fluid
o The image shows fluid around the gallbladder – may be due to ruptured gallbladder
CT Gallbladder Rupture
o The bile forms a pocket around the gallbladder
o Patient presents with RUQ pain
 When presenting with RUQ pain, use 1. US 2. CT
MRCP Biliary System
o MRCP – Magnetic Resonance Cholangiopancreatography
o Used when the cause of the biliary obstruction is not seen in US & CT
CT Fatty Liver
o A non-malignant cause of elevated LFTs
o Seen in patients who are obese, use steroids (chronic use of other medications may cause
fatty liver also), alcoholics
Ultrasound Cirrhosis of Liver
o Common finding in patients with abnormal LFTs
o The image shows a nodular liver surface
CT Cirrhosis of Liver
o The image shows ascites around the liver, and the liver has a nodular/irregular surface
o This patient also has splenomegaly (large organ opposite liver)
CT Liver Metastasis
o Need to biopsy masses to determine their etiology – are they primary liver cancer, or
metastasis from another body region?
Ultrasound Liver Metastasis
GI2 #15
2/25/04 11am
Dr. Caffrey
K. Stancoven for J. Brace
Page 3 of 7
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o See multiple masses of varying size in the liver
Liver Abscess
o Liver abscess are seen in patients with inflammation in other parts of their body
(appendicitis, etc…)
o The infectious organisms usually get to the liver via the portal system
o CT is the best imaging modality for viewing abscesses & metastases
 Some abscesses have air-fluid levels which make them easier to detect on CT
o The abscesses may be single or multiple. They may need to be drained if fairly large;
antibiotics may work on small abscesses.
CT Liver Laceration
o May also see other organs in the same vicinity that are damaged
o This image shows a hematoma (arrow) and blood seeping through the liver capsule. You
can also see a rib fracture in this image
Mid Abdominal Pain, Elevated Pancreatic Enzymes
o Pancreatitis
o Pancreatic Cancer/Mass
Ultrasound Pancreas
o The pancreas is only visualized with US in thin patients, and even if the patient is thin, it
is still difficult to visualize the pancreas (need training)
o Have to use anatomical landmarks to find pancreas – splenic vein, mesenteric arteries,
portal veins, etc…
CT Pancreas
o Pancreas is easier to see and diagnose with CT
o You can use a higher resolution and thinner slices when viewing the pancreas
o The most common cause of acute pancreatitis: gallstones
o The most common cause of chronic pancreatitis: alcoholism
Ultrasound Pancreatitis
o Hard to see
CT Pancreatitis
o This image shows diffuse pancreatits
o Any inflammatory process cause ill-defined fat planes
 Caused by the invasion of inflammatory products and cells
Complication of Pancreatitis
o Pseudocyst – Well defined collection of pancreatic enzymes caused by leakage of the
inflamed main pancreatic duct
o This is usually drained because you don’t want the pancreatic enzymes to leak into the
abdominal cavity
CT Pancreatic Cancer
o Pancreatic cancer is difficult to image because the tumor masses may be too small
o Easier to detect when the tumors cause secondary changes to pancreas or other nearby
organs
 The pancreas in this picture has a tumor (t) that is blocking a pancreatic duct
(arrows)
 This is causing the duct to dilate, and the pancreas distal to the tumor to atrophy
MRI Pancreatic Cancer
o Can be used to detect smaller cancer masses
LUQ Pain
o Splenomegaly
 Due to mono, leukemia, lymphoma, HIV/AIDS, portal hypertension
o Splenic Rupture due to Mass or Trauma
 Blunt or perforating trauma
Ultrasound Spleen
GI2 #15
2/25/04 11am
Dr. Caffrey
K. Stancoven for J. Brace
Page 4 of 7
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Done on initial exam
With US, you can see entire length of spleen. Measure the length to determine if it is
enlarged or not
CT Splenic Metastasis
o This image shows a malignant melanoma with a large splenic mass (m)
o With a mass in the spleen, this patient is at risk for splenic rupture
CT Splenic Rupture
o Usually due to blunt force trauma
o See a fractured spleen. May have to remove spleen
o Use CT to evaluate the extent of the injury
Flank Pain/Hematuria
o Urinary Tract Obstruction
 Most commonly due to stones
o Pyelonephritis
o Renal Cell Carcinoma
 Usually causes painless hematuria
o Renal Trauma
 Blunt or penetrating
Nonobstructive Renal Calculus
o Noncontrast CT is best for viewing renal stones
UPJ Obstruction by Calculus
o Image shows mild hydronephrosis (arrow head) and a tiny stone (arrow) at the UPJ
UVJ Obstruction by Calculus
o Shows a dilated renal pelvis and calyces
o No stone is seen in the ureter, so you must image the pelvis to see the stone and the
junction of the ureter and the bladder
Right Hydronephrosis
o Small kidney with dilated renal pelvis & calyces, ureter
Ureteral Obstruction by Malignancy
o Bladder cancer obstructing the distal right ureter
o Women with advanced cervical cancer may present with ureter obstruction
Renal Infection (pyelonephritis)
o CT is better than US to detect a kidney infection
o The infection may be hard to distinguish from a renal mass on imaging
 You may need to biopsy to be sure its an infection and not cancer
 Also look at the patient’s history, physical exam, and presentation to help
determine infection verses cancer
Renal Cell Carcinoma
o 1st image shows renal cell carcinoma on left side. Usually presents with painless
hematuria
o 2nd image shows renal cell carcinoma that has replaced entire kidney and invaded the
renal vein
Renal Laceration
o May also see rib or vertebral fractures, or spleen injuries
o Using contrast CT will help shows small lacerations
RLQ Pain
o Appendicitis
 If patient presents with typical presentation, you may not need imaging to
diagnose. Just send to surgery
o Crohn’s Disease
 May mimic appendicitis, but no surgery is needed
Normal Appendix
GI2 #15
2/25/04 11am
Dr. Caffrey
K. Stancoven for J. Brace
Page 5 of 7
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If the appendix fills with contrast, then it is normal
Appendicitis is due to an obstruction in the appendix, so contrast would not be able to
enter the inflamed appendix
Appendicitis
o Appendix is enlarged with a gray appearance of fat around the appendix
Crohn’s Disease.
o Can involve any part of the digestive tract
o Most common at the junction of the ileum & cecum
o See thick bowel wall & abnormal fat around the bowel
General Abdominal Conditions
o Pain not localized, patient feels bloated, fullness, uncomfortable
o Causes:
 Ascites – fluid in the abdomen and pelvis. Caused by liver cirrhosis or cancer
 Abscess – maybe hard to localize
 Free Air and other Abnormal Air Collections – indicates ruptured bowels
 Lymphadenopathy – due to lymphoma or other cancer
 Bowel Obstruction or Inflammation – Best seen with CT
 Bowel Perforation - Best seen with CT
 Bowel Ischemia - Best seen with CT
 Abnormal Abdominal Vascularity - Best seen with CT
 Colon Polyp/Colon Cancer – There is a new screening for colon cancer/polyps
using CT images
Ultrasound Ascites
o US is ideal for finding fluid
o While using US, you can use a needle to sample or drain fluid
CT Ascites
o Arrows show ascites fluid
Abscess
o Complication of ruptured appendix, may contain air (air-fluid level)
Lymphadenopathy
o See “too many round things on CT”
o Can be massive – may move aorta &/or IVC
o Also can see masses within the bowels
Lymphadenopathy
o US with palpable abdominal mass
o See multiple solid masses anterior to the aorta (a)
Small Bowel Obstruction
o Strictures (adhesions) from previous bowel obstructions or surgeries
o If there is no free air or fluid – probably hasn’t ruptured
o The image shows dilated small intestines in the upper right side of the image (white
mass)
Colon Obstruction
o Image shows dilated large intestines (big empty black areas on left, center, & right in
image)
o Dilated proximal & transverse colon due to obstruction by colon cancer (bottom right of
image)
Ventral Hernia
o Palpable abdominal mass
o Use CT to determine what bowl has herniated and check for obstruction/ischemia
Bowel Ischemia
o Due to low blood flow or obstruction to the blood supply
o Usually get nonspecific CT finding – enlarged, fluid filled bowels. Patient is very ill
GI2 #15
2/25/04 11am
Dr. Caffrey
K. Stancoven for J. Brace
Page 6 of 7
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Bowel Perforation
o See free air in abdominal cavity
CT Colonography
o CT is being developed for screening for colon cancer
o Patient has similar preparation as colonoscopy
o Use CT to look for polyps
Virtual Colonoscopy
o Computer takes CT images and forms a 3-D image of the colon
Ultrasound Collateral Vasculature
o Use color flow Doppler to see vasculature
LLQ Pain
o Diverticulosis – may or may not be painful
o Diverticulitis
Diverticulosis
o Herniation of the mucosa and submucosa through the muscular wall of the colon
o May be due to low fiber diet
o May get inflamed – becomes painful. May eventually rupture
Diverticulitis
o Abnormal surroundings seen on CT
Abdominal Pain with Back Pain
o Need to evaluate these patients with CT
o Causes
 Aortic Aneurysm/dissection
 Bone Metastasis, Inflammation or Fracture
Ultrasound Aorta
o US only good in thin patients to view aorta
CT Aortic Aneurysm
o See enlarged aorta (3 times normal size)
Aortic Rupture (correction from power points)
o See large hematoma from ruptured aorta into abdomen
CT Vertebral Osteomyelitis
o Can be a cause of abdominal pain
o Destruction of bone/disc by infection
Vertebral Metastasis
o You need to find the primary cancer
Ultrasound - Advantages
o Fluid collections
o Gallbladder
o Biliary ducts
o Gallstones
o Vascular flow/vascularity
o Palpable mass
Ultrasound - Limitations
o Bowel gas
o Obese patient
o Surgical dressings
o Large calcification obscuring deeper structures
o Uncooperative patient (motion)
Computed Tomography - Advantages
o Bone/Calcifications
o Fat
GI2 #15
2/25/04 11am
Dr. Caffrey
K. Stancoven for J. Brace
Page 7 of 7
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o Fluid/Blood
o Gas/Ectopic Air
o Bowel
o Inflammation
o Trauma
Computed Tomography - Limitations
o Patient motion
o Ionizing Radiation
o Metal/Residual Barium
o Pregnancy
Magnetic Resonance Imaging - Advantages
o Fat
o Fluid/blood
o Improves discrimination of soft tissues
o Further characterization of mass or fluid seen by CT or ultrasound
Magnetic Resonance Imaging - Limitations
o Calcifications
o Gas
o Bowel
o Metal
o Contraindications: pacemaker, intracranial aneurysm clip and others
o Patient motion
o Pregnancy