Radiology of the Abdomen
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Transcript of Radiology of the Abdomen
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Radiology of the Abdomen and Pelvis
And
Cross-Sectional Anatomy
MBS 208
Introduction to Basic and Clinical Anatomy
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Overview Common imaging modalities for the
abdomen and pelvis How to read an abdominal plain film Visualizing anatomy through imaging
Spaces in the abdomen and pelvis The 4 abdominal quadrants Vascular anatomy in the abdomen and pelvis The colon, with attention to the right lower
quadrant The pelvis
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Imaging Modalities for the Abdomen and Pelvis
Commonly Utilized Modalities
Ultrasound CT (computed
tomography) Radiography
Abdominal plain film Fluoroscopy
Hysterosalpingography
Other Modalities MRI
Magnetic resonance imaging
Nuclear medicine Gallium scan
Positron Emission Tomography (PET)
Jeffrey B. Mendel, M.D. 2007
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X-ray Basics
The detector (film or digital) captures the xThe detector (film or digital) captures the x--rays that rays that penetrate the target and an image is createdpenetrate the target and an image is created
PA (anterior-posterior) view X-rays enter through back of chest and exit out front where they are detected
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X-ray BasicsAttenuation of the x-ray
beam is affected by:
Tissue density
Tissue thickness
X-ray energy (kV)
Structural elements that attenuate the beam to a greater extent than air (black) or are less attenuating than bone (white) show radiographically in various shades of gray
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Air
Soft Tissue
Fat
Bone
X - RAY --- FOUR BASIC DENSITIES
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The spine, ribs, scapulae, and ribs attenuate the beam and are white
The heart and soft tissues are gray
The lungs and trachea are filled with air and are black
Why is there an air-fluid level in the stomach beneath the left hemidiaphragm?
What is black, white, and gray?
Answer: the patient was imaged in the upright position
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Approach to plain film interpretation
1) What is the normal and variant anatomy? Is something absent? Is there an additional finding?
2) Check for clues in the skin and soft tissues 3) Then evaluate the bones
position/alignment, cortex, density, internal architecture, focal lesions
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Cervical rib
Bilateral cervical ribs Polydactyly
Additional Findings:
That extra stuff
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Whats wrong with this radiograph?
The heart and aortic arch are also on the right side (normally left-sided structures). This is known as situsinversus, a congenital variant.
Also note the absence of both clavicles.
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Ultrasonography (ultrasound)
Uses sound waves of frequencies 2 to 17 MHz. (Audible sound is in the range of 20 Hz to 20 kHz.)
Like SONAR, images result from the propagation of sound waves through the body and their reflection from interfaces within the body
The time it takes for the sound waves to return to the transducer provides information on the position of the tissue in the body
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Ultrasound
No ionizing radiation Uses sound waves to visualize structures
Very operator dependent Can not penetrate bone
Mainstay of diagnosis for: Ob-gyn (strong foothold' in Ob) Screening for vascular, abdominal & renal pathology Palpable lesions: Breast and MusculoskeletalMusculoskeletal Thyroid/neck pathology Pediatric / Young women
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Gray scale = anatomy
Colour Doppler = velocity and direction
Gallstones
Fetus in utero
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CT computed tomography Cross-sectional modality with capabilities for multiplanarreconstruction and dynamic imaging to assess vascularity
Tube rotates around the body and a circle of stationary detectors detects the penetrating x-rays forming an image
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CT Computed Tomography
X-ray tube and a semicircle of detectors rotate around the body
Computer collects the data from the detectors and reconstructs a cross-sectional image (back-projection)
Tube and detectors spin continuously allowing for rapid imaging (helical CT) as with CT angiography
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CT - Limitations
Ionizing radiation Requires contrast: IV and oral
Oral contrast requires prep time (1-2 hours) Iodinated contrast is nephrotoxic Iodinated contrast has fatality rate 1:50,000
even with low osmolar contrast
Patient must be supine (prone) $$$
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MRI -Magnetic Resonance Imaging Uses a high-field magnet
to image the body Rapidly switching
magnetic field gradients align the precession of the H protons (water and fat)
When the gradients are turned off, a faint radiofrequency signal is produced
Image is reconstructed using Fourier transforms
Multiplanar and vascular assessment possible
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External Magnetic Field Be
High B
Low B
Create a gradient in the magnetic field within the scanner so that it is high in one corner, lowest in the opposite corner.
Protons in the high-field region produces highest frequency signal
Be
Spin flips
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Magnetic Resonance Imaging
Magnetic nuclei are abundant in the human body (H,C,Na,P,K) and spin randomly Since most of the body is H2O, the Hydrogen nucleus is especially prevalent
Patient is placed in a static magnetic field Magnetized protons (spinning H nuclei) in the patient align in this field like compass needles Radio frequency (RF) pulses then bombard the magnetized nuclei causing them to flip around
The nuclei absorb the RF energy and enter an excited state When the magnet is turned off, excited nuclei return to normal state & give off RF energy
The energy given off reflect the number of protons in a slice of tissue Different tissues absorb & give off different amounts of RF energy (different resonances) The RF energy given off is picked up by the receiver coil & transformed into images MRI offers the greatest contrast in tissue imaging technology (knee, ankle diagnosis) cost: about $1450 - $2000 time: 30 minutes - 2 hours, depending on the type of study being done
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MRI: Cadillac of soft tissue imaging
Mainstay of diagnosis for Neurologic imaging Musculoskeletal imaging (after plain film) Magnetic Resonance Angiography
Angiography without iodinated contrast*
Expanding applications in chest, abdominal, Expanding applications in chest, abdominal, breast, and pelvic imagingbreast, and pelvic imaging
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Visualizing Anatomy: Brain MRI
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MRI of torn ACL MRI of moderately torn rotator cuff
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MRI - Advantages True multiplanar imaging Intravenous contrast not usually required No ionizing radiation required Newer scanners and well-trained technologists
minimize problems with claustrophobia
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MRI - Limitations Ferromagnetic objects
cause artifacts that limit imaging
Contraindicated for patients with Implantable devices:
cochlear implants, pacemakers*
Metal shavings in orbits Severe renal failure
Still requires more cooperation and longer time than CT
$$$$
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Each image from CT, MR, PET, US or NM provides a 2D image
Stack enough thin sections together and you obtain a 3D volume matrix
If the width of the slices is similar to the size of the elements in the 2D matrix you can reconstruct images in any plane you choose or make 3D models of high resolution
How do you obtain 3D images from 2D slices?
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Coronary Coronary CT Angiography may eventually replace invasive angiography -No arterial puncture = no risk of vascular damage3D view of the arteries and the adjacent organs
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The Axial(horizontal) Section
An An axialaxial section is section is horizontal and horizontal and represents the plane represents the plane in which most CT is in which most CT is acquiredacquired
liverRight hemidiaphragm
LA
Ao root
LV
Ao
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The Sagittal Section
A A sagittalsagittal section is in a plane section is in a plane running longitudinally frontrunning longitudinally front--toto--backback
The The midmid--sagittalsagittal section section divides the body into two divides the body into two symmetric halvessymmetric halves
spine
LA
PAAo
Bladder
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The Coronal Section
Coronal sections are Coronal sections are in planes running in planes running sideside--toto--side side
A A coronalcoronal section is section is vertical perpendicular vertical perpendicular to the sagittal sectionto the sagittal section
RV LV
liverstomach
Ao PA
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Fluoroscopy Dynamic radiography
Permits real-time evaluation of the gastrointestinal tract
Barium Swallow (esophagus) Upper GI Series (stomach) Small Bowel Follow-through Barium Enema (colon)
Barium (& air) is introduced by enema or swallowing
Barium appears white on the images (high density attenuates the x-ray beam)
Can assess both intrinsic (mucosal) and some extrinsic
(mass-effect) abnormalities
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Nuclear Medicine - GI Bleeding Scan Evaluates bleeding, particularly from the lower GI tract
Radiopharmaceutical = Tc99m invitro labelled RBCs
Sequential 5 minute images acquired over an hour
Looking for progressive accumulation of tracer
Where is the bleeding on this scan ? Answer: Cecum
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Injected Gallium-67 binds to transferrin & enters the extracellular space of tumor cells via permeable capillaries
9/03
Gallium Scan Used for lymphoma
staging & response
Baseline imaging determines whether the tumor is gallium-avid
Serial scans assess response to treatment and can distinguish scar from residual tumor
Baseline
11/03
Response to Rx
7/04
Lymphoma recurs
PET/CT Initial Scan 6 Month Follow up
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Introduction The primary imaging modalities for the abdomen
and pelvis are plain film, ultrasound, and CT Most common indications for imaging include
pain, trauma, distention, nausea, vomiting, and/or change in bowel habits
Choice of modality depends upon clinical symptoms, patient age & gender, and findings on physical exam
Mastery of the anatomy within each quadrant can help explain particular symptoms, clinical presentations, and/or imaging findings
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Reading the Abdominal Plain Film
Also known as the KUB (kidney, ureter, & bladder)
Use a systematic approach to interpretation Lung bases & diaphragms Bones Soft tissues
Abnormal calcifications Organs Bowel
Plain film in 3 year old patient with pain
Stomach
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Reading the Abdominal Plain Film
Also known as the KUB (kidney, ureter, & bladder)
Use a systematic approach to interpretation Lung bases & diaphragms Bones Soft tissues
Abnormal calcifications Organs Bowel
Plain film in 3 year old patient with pain
Stomach
Colon
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AP SUPINE ABDOMEN X-RAYGAS PATTERN
COLON
STOMACH
SM. BOWEL
Normal abdominal gas pattern with air in the stomach and scattered non-distended loops of large bowel and little small bowel gas present.
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Small intestine-jejeunum & ileum
Transverse colon
Ascending colon
Descending colon
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Small vs. Large Intestine
Horton KM et al, Radiographics. 2000
Colon has sacculations called haustra as teniae coli are shorter than the colonic wall
Colon is relatively peripheral but can be very mobile
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Small bowel had plica circulares & is positioned centrally
>3 cm diameter and air/fluid levels on the upright suggests small bowel obstruction
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Small bowel has plicae circulares,mucosal folds that extend across the entire diameter of the bowel
The colonic haustra indent the margin but do not extend acrossthe bowel
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Liver
Gall bladder
stomachspleen
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Plain Film Soft tissues : Liver, Spleen, & Kidney
St
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Soft Tissue Structures: Subtle on KUB
Stom
ach
Stomach
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Always check the lung bases for an infiltrate
Look for free air on the upright film: commonly beneath the right hemidiaphragm
Liver edge
diaphragm
Free air under right hemidiaphragm due to perforated duodenal ulcer
Whats Up on an Abdominal Film?
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No gastric air bubble in left upper quadrant
Air/fluid level superimposed on heart
More Misplaced Air
HIATAL HERNIA
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UPPER GI ORAL BARIUM CONTRAST
BARIUM ENEMA - RECTAL BARIUM CONTRAST
STOMACH
COLON
WITHOUT CONTRAST
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NORMALESOPHAGUS
DIAPHRAGM
HIATAL HERNIA
DIAPHRAGM
*Note distended distal esophagus with herniation of gastric fundus into chest through esophageal hiatus.
This allows for reflux of gastric contents into esophagus.
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Surgical clips in RUQ from prior cholecystectomy Appendicolith on plain film
rectum
Calcifications, Metallic Surgical and Foreign Bodies
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Clinical-Anatomic Approach
Divide and conquer !!! Median and
transumbilical planes divide the abdomen and pelvis into 4 quadrants
Each quadrant has its own particular symptoms, clinical presentations, and/or imaging findings
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The Right Upper Quadrant
What lives in the right upper quadrant?
Liver
Gallbladder
Hepatic Flexure of Colon Right kidney and adrenal gland
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Clinically Important Hepatic Anatomy
Falciform ligament defines right from left lobe
Blood supply: 70% via portal vein 30% via hepatic artery
Left, middle, and right hepatic veins converge with IVC
Each of 8 liver segments have portal vein, hepatic artery, and bile duct (portal triad)
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Normal Liver Normal Liver on contrast on contrast
CTCT
Lt lobe
Rt lobe
IVC
Sto
SpLK
APortal Vein
Gall bladder
P
Falciform Lig. Serves as ananatomical marker
between liver lobes
CrusCrus of diaphragmof diaphragm
Sto
CBD
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PORTAL VEIN
Coronal and Axial imagesCT
US
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Metastatic disease
Liver is the most common metastatic site after regional lymph nodes
Metastases from colon, stomach, pancreas, breast and lung primaries
Lower attenuation foci within the liver during portal venous phase
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Hepatic duct
Common hepatic artery
Portal vein
Porta Hepatis Portal Triad
Splenic artery
Cystic artery
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Clinically Important Biliary Anatomy Hepatic cells secrete bile into
caniculi Drain into interlobular bile
ducts Ducts merge into progressively
larger ducts, eventually R and L hepatic ducts
Merge in Porta Hepatis to form common hepatic duct
Joins with cystic duct to form common bile duct
Pass through pancreatic head to empty into duodenum via sphincter of Oddi
Common bile duct
Gallbladder
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Gallstone is compressing the common bile duct blocking the flow of bile from the liver.
Blocked Biliary System
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GALLSTONES15-30% calcify
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Cirrhosis: End-stage Liver Disease
The left lobe & caudate lobe hypertrophy
Portal venous pressure rises causing Reversed portal venous flow (hepatofugal) Splenomegaly Varices Ascites
Bowel loops are positioned centrally due to the presence of ascites
Spleen
Varices
Liver
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The Left Upper Quadrant
What lives in the left upper quadrant?
Spleen
Left lobe of liver
Splenic flexure Left kidney and adrenal gland
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spleen
gall bladder
duodenum
stomach
liver
PylorusL2
L1
T12
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Splenic rupture due to MVA
Blunt trauma The left package spleen, left kidney
The right package liver, right kidney
Midline left lobe liver, pancreas
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HEPATIC / SPLENIC
LACERATION
Note rib fractures on x-ray
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ENLARGED PALPABLE SPLEEN
Enlarged spleen raises issue of lymphoproliferative diseases or infection.
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Midline Anatomy
What lives in the midline of the abdomen?
Pancreas
Stomach
Colon and small intestine Aorta and IVC
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Pancreatitis = Inflammation of the pancreas
Normal pancreas on CT
Pancreas
liver
liver
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Midline: Rectus abdominis muscle
with linea alba at midlineAnterolateral(Outer to Inner Layers):
External oblique muscle with aponeurosis joining anterior layer of the rectus sheath
Internal oblique muscle with rectus abdominismuscle
Transversis abdominismuscle
Transversalis fascia Peritoneum
Ventral HerniaAbdominal Wall
Hematoma in the Rectus Abdominis
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Key arterial anatomy of the GI tract
Celiac artery (axis)- arises form the ventral surface of the aorta, just below the diaphragm, at the level of the lower half of T12
Superior mesenteric artery (SMA)- arises form the ventral surface of the aorta approximately 1 cm below the origin of the celiac at the level of the upper half of L1
Inferior mesenteric artery (IMA)- arises from the ventral surface of the aorta at the level of L3, approximately 3 cm above the aortic bifurcation
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Abdominal Aortic Aneurysm (AAA)
Aorta dilates causing loss of laminar flow and intraluminalthrombus (non-enhancing region)
Aneurysms > 5cm in diameter are at high risk for rupture
Normal caliber aorta
Images of AAA courtesy of A. Davidoff MD
Infrarenal AAA with intraluminal thrombus
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Right pelvic renal transplant as seen on MRA
MR Angiography
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Celiac Artery (Axis)
In most Individuals (~65%) the celiac axis divides into three majorbranches
1. Left gastric2. Splenic3. Hepatic
Diagnostic Angiography, Kadir, 1986.
Ashley Davidoff, MD
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SMAsmall bowel, right and transverse colonIMAleft colon, sigmoid colon and part of rectum
GI Vasculature:GI Vasculature:Demand andDemand and
SupplySupply
Clinically OrientedAnatomy, Mooreet al., 1999
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SMA & IMA
IMALt colic
Marginal art of colon
Sigmoid and superior rectal art
Middle colic
splenic
renal
SMAIMA
GDA
cHA
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CT Mesenteric Angiography
This has virtually replaced diagnostic angiographyThis has virtually replaced diagnostic angiography
No arterial puncture = no risk of vascular damageNo arterial puncture = no risk of vascular damage3D view of the arteries and the adjacent organs3D view of the arteries and the adjacent organs
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Extravasation of contrast marking site of bleeding
Jejunal
Ileocolic
Right colic
SMA
Lower Intestinal Bleed
Bleeding scan first, if positive:
Arteriogram with possible embolization of bleeding vessel
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Spaces in the Abdomen and Pelvis
Potential spaces in the abdomen and pelvis include: Intraperitoneal Spaces
Greater and lesser omentum
Retroperitoneal Extraperitoneal
Potential spaces are difficult to appreciate on dissection
Best seen on imaging, especially when filled with air or fluid
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Peritoneal vs. Retroperitoneal Spaces
ANT
Intra-peritoneal organs are covered in a layer of peritoneum, a double layer of which (mesentery) connects them to the abdominal wall
Liver, stomach, spleen, gallbladder, small bowel & colon (cecum, transverse, sigmoid)
Retroperitoneal organs lie behind the posterior peritoneum
Kidneys, adrenal glands, aorta & IVC, duodenum, ascending and descending colon, pancreas,
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Fluid in the peritoneal cavity
Scott Tsai, MD Fluid in lesser sac
Omentectomyclips
S
Panc
Liver
Greater and lessersacs communicate via the epiploicforamen
Greater sac Not all fluid is free flowing
Loculated ascites is common in later stage
ovarian carcinoma
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Fluid in peritoneal cavity def: space
between visceral and parietal peritoneum
Fluid accumulates in dependent areas
MorrisonMorrisons pouchs pouch (the peritoneal reflection separating the liver from the retroperitoneal kidney) is the most dependent location while supine
The left and right paracolic paracolic guttersgutters are also dependent and commonly accumulate fluid
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l. Paracolic gutterr. Paracolic gutter
Hepatorenalrecess (pouch of Morison)
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The Lower Quadrants
Right: Cecum, ileocecal region, and appendix; ovary (if female)
Left: descending colon and ovary
Most common clinical entities in the lower quadrants are:
Right Appendicitis, inflammatory bowel disease (Crohns), colonic malignancy
Left Diverticulitis
Both Pelvic abnormalities
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Appendicitis
Obstruction of appendiceal lumen leads to inflammation and/or rupture
Typically present with fever, nausea/vomiting, and periumbilical/right lower quadrant pain
Presence of calcified appendicolith (7-15%) and abdominal pain = 90% probability of acute appendicitis
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Appendicitis
AppendicolithAppendicolith seen on bone windowseen on bone window
Normal
Inflamed
Inflamed appendix
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Diverticulosis
Herniation of mucosa and submucosa through muscular layers
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The Pelvis
What lives in the pelvis?
Female: Uterus and ovaries
Bladder
Male: Bladder
Prostate and seminal vesicles
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CALYX
PELVIS
URETER
BLADDER
Urinary System
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The right kidney appears swollen with stranding in the perinephric fat and a dilated collecting system (hydronephrosis)
A stone in the mid right ureter accounts for obstruction of the collecting system
Perirenal Peril
Hydronephrosis Nephrolithiasis
Non-obstructing stone
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Perirenal space outlined
Extravasated Extravasated urine in the urine in the right right perirenal perirenal space due to space due to obstructive obstructive kidney stonekidney stone
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Bladder stones or calculi with obstruction of the
collecting system
Bladder
Kidneys
Stones
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Imaging of the Female Pelvis
Ultrasound is the most common modality used to image the uterus and ovaries
Hysterosalpingography is exclusively used to assess tubal patency (infertility evaluation)
Pelvic MR is used selectively to evaluate the uterus, ovaries and fetus
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SacrumSacro-iliac
jointSacro- iliac
joint
Femoral headGreater
trochanter
Lesser trochanter
Superiorpubic ramus
Symphysis pubisInferior pubic ramus
Acetabulum
AP PELVIS
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PELVIC VASCULAR TREE
4
5
6
1. ABDOMINAL AORTA
2. INTERNAL ILIAC ARTERY
3. EXTERNAL ILIAC ARTERY
4. LUMBAR ARTERY
5. COMMON FEMORAL ARTERY
6. COMMON ILIAC
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Psoas major m.
Iliacus m.
diaphragm
Quadratuslumborum
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Pelvic Viscera - Malebladder
prostate
rectum
Descending, sigmoid colon
Ascending colon
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NOTE OBSTRUCTION
PROSTATE
Benign Prostatic Hyperplasia
This can obstruct the ureters entering the bladder leading to hydronephrosis and renal failure.
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Pelvic Viscera - Female
uterus
bladder
uterus
rectum
Descending colon
Ascending colon
Rectouterinepouch
ovary
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Uterine (Fallopian) tube
ovary
fundus
body
cervix
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Normal Uterus on Sagittal MR
Image: St. Pauls HospitalVancouver, BC
extracted from their website:http://www1.stpaulshosp.bc.ca/
Myometrium:(homogeneous, moderate
to low signal)
Endometrium: homogeneous intense signal
B
V
A
R
P
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UterusUterus Hysterosalpingography
Lower Uterine Segment
Uterine cavity
Ampullary segment
Isthmic Segment
Catheter
FimbriatedEnd
Normal
Infundibulary Segment
Contrast has been injected through a canula placed into the cervical os. Iodinated contrast flows retrograde with injection filling the uterine cavity with reflux into the fallopian tubes.
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Imaging of the Fetus
US is the primary modality for imaging during pregnancy Gestational sac yolk sac fetal pole cardiac activity at
5.5-6 weeks gestation Full fetal survey typically performed at 16-18 weeks
MR used to evaluate specific developmental anomalies
9 week pregnancy
US
30 week pregnancy
MRI
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Conclusions The primary imaging modalities for the abdomen
and pelvis are plain film, ultrasound, and CT Most common indications for imaging include
pain, trauma, distention, nausea, vomiting, and/or change in bowel habits
Choice of modality depends upon clinical symptoms, patient age & gender, and findings on physical exam
Mastery of the anatomy within each quadrant can help explain particular symptoms, clinical presentations, and/or imaging findings