CT Anatomy and Pathology of the
Urinary System, Adrenal Glands and
Prostate.
By Erik Poyourow MS3
First, some basic CT Principles you
will need for this learning module.
http://www.nowhow.nl/nederlands/images/CT-scanner.jpg
CT Basics
http://www.babalublog.com/archives/ToeTag.jpg
View the image is as if you were looking up from the patient’s feet.
CT Basics
>
>
Metal
+500 to +1000 HU
Bone
+300 to -500 HU
>
>
Water
(tissue and blood)
0 HU
Fat
0 to -50 HU
Air
-200 to -1000 HU
•Things appear whiter according to their relative densities.
•This property is called “Attenuation” and it is quantified in Hounsfield
Units (HU), which can be measured on CT viewing software.
ADRENAL GLANDS
Adrenal glands
•Located superior and medial to the kidneys and lateral to the diaphragmatic crura.
•Like the kidneys they are within the Renal fascia and are therefore…
•Surrounded by perirenal fat which appears dark on CT.
•Adrenal glands They look like a “V” or a “Y” on CT.
The Right Adrenal
Gland is behind the IVC and medial to the liver. The Left Adrenal is lateral to
the Aorta or Left Crus and posterior to the splenic vessels.
Identify the adrenals
associated
structures.
Left and
click
for answers.
Aorta
Right Hepatic
Lobe
Pancreas
IVC
Left
Adrenal
Right
Adrenal
Right Crus
Left Crus
One more look without the arrows…
Kidneys
Identify the following…
Renal Artery and Vein
*usually arise at L2
Capsule
Pelvis
Major
Calyx
Cortex
Ureter
Medulla
Minor
Calyx
http://www.adam-rouilly.co.uk/products/Somso/MU3.jpg
Now Back to CT Anatomy
Head of
Pancreas
Aorta
IVC
Superior Pole
of Left Kidney
comes into
view first…
The Right Kidney comes into view a little more inferiorly…
Watch the veins enter the IVC…
…watch the arteries exit the Aorta.
SMA
IVC
Left Renal Vein
*entering the IVC,
Left Renal Artery
Superior Pole of
Right Kidney
Right Renal Artery
*exiting the aorta
Aorta
Following the vasculature down…
SMA
Left Renal Vein
(*between SMA
and Aorta)
Right Renal Artery
Left Renal Artery
Following the vasculature down…
Left Renal Vein
Right Renal Vein
*coming off IVC
Right Renal Artery
Left Renal Pelvis
*dives down
wheras vessels run
more horizontal
Left Renal Artery
Following the vasculature down…
Right Renal Vein
Left Renal Vein
Right Renal Artery
Left Renal Artery
Following the vasculature down…
Right Renal Vein
Left Renal Vein
Fascial Compartments
Anterior
Renal Fascia
Look very closely!
(“Gerota’s fascia”)
Note: this is
the “Paraconal
fascia”
continuing
anteriorly.
Posterior
(Faint line)
Renal Fascia
(“Zuckerkandl’s
Fascia”)
The Renal fascia divides perinephric (around the kidneys) from
paranephric space (around the renal fascia). This becomes
important when edema, pus or blood enters a compartment.
Time out for a brief technical point…
Phases of IV Contrast
Depending on the timing, different structures are
enhanced by IV contrast.
• Pre-contrast Phase = Non-contrast – no
enhancement.
• Arterial Phase (15-25 seconds)
• Angionephric or Venous Phase (30-60
seconds) The Renal cortex appears enhanced.
• Nephrographic Phase (75-100 seconds) Cortex
and Medulla appear enhanced.
• Excretory/Urographic Phase (after 3 minutes -routinely taken at 10 minutes) The collecting
system is enhanced.
OK, now back to Anatomy…
Anatomy of the Collecting System
http://neosavina.ivyro.net/image/anatomy/adam/a
bdomen/aa51_1.gif
Post Contrast Image
(Remember, it helps to visualize the Urinary Collecting System.)
Pelvis
Calyces
Structures related to the ureters
IVC
Aorta
Right Ureter
Left Ureter
Psoas Muscles
Follow the Ureters Down along the Psoas Muscle
Left Ureter
Right Ureter
Left Common
Iliac Artery
Right Common
Iliac Artery
Common Iliac Veins
After crossing over the branch point of the Iliacs, the ureters move
along the lateral pelvic wall within the ureteric fold…
Ureters
On their way to the bladder…
Bladder
Finally the ureters enter the bladder
posterolaterally.
Bladder
*dense contrast settles in
the dependent bladder,
with the urine on top.
Ureters
What gender is this patient?
What’s this below the Bladder,
And anterior to the rectum?
Prostate
Strong work! In the next section try to use your
understanding of CT anatomy to identify pathology.
Search Pattern
•Always be systematic in how you look at images.
•Look for what is there and what is absent.
• Adrenal
limbs
≤ 1 thing
cm thick,
•Don’t stopGlands
once you –
have
found one
wrong. uniform,
homogenous, and without convexities.
• Kidneys – without enlargement, atrophy, distortion,
striation, cysts or masses.
• Fascial Compartments – without swelling, fluid, air or
fat stranding
• Pelvises and ureters – without dilation or obstruction.
• Bladder – distension, wall thickness and contents in the
lumen.
• Prostate – without enlargement or nodules
Urinary CT Pathology
The following slides show common CT findings.
the way,
what kind
is theof image, is
•Horseshoe
Kidney
1. By
Figure
out what
there contrast
and if so where.
abnormality in this CT
congenital fusion 1-4/1000.
2. image?
Identify the abnormality.
•3-4 x risk of Transitional
3. Then create a short differential in
your
head.
Cell
Carcinoma.
CASE #1
What is this?
Foley bulb
catheter in
the bladder.
Why is he catheterized? Left click to scan
inferiorly and see if there is an obvious reason…
What is the abnormality?
Hint: don’t
forget to
look at
bones.
Does the
pubis
symphysis
look wide
to you?
Bladder
And what’s herniating out between
the pubic bones?
Pelvic Symphysis Diastasis
http://www.swsahs.nsw.gov.au/livtrauma/education/sudden/pic
s/pelvis1.jpg
•In pelvic fracture or diastasis, look for
traumatic disruption of the urethra and
bladder.
CASE #2 Where is the abnormality?
Does this person have 2 Gall Bladders?
Unlikely… so lets keep scanning down the body.
Hmmmm… that looks big.
Left Click to keep scanning down…
What structure is involved?
Right Kidney
Based on the signal intensity what is the likely density of this lesion?
Water.
Does it communicate with the vasculature?
No, it is not contrast enhancing.
Give a short differential.
Simple Renal Cyst (water),
Hemorrhagic cyst (blood),
Abscess (pus).
Simple Renal Cyst
•Very common “incidentaloma” in older patients
(>50% in patients over 55 years old).
•Smooth, thin walled cysts, without septae, that
are homogenous near-water density (-10 to +20
HU) and non-enhancing are benign.
•Smaller cysts may show “pseudoenhancement,”
up to +10 HU due to various artifacts.
•Usually asymptomatic and require no treatment.
http://medlib.med.utah.edu/WebPath/jpeg1/RENA
L002.jpg
CASE #3
What is the abnormality?
Is this lesion involving other
What do you expect the Right Kidney to look like?
structures
it? pelvis = Hydronephrosis
Cortical Thinningaround
+ dilated renal
Yes, the Right
Ureter is dilated.
Thickened bladder wall.
What is the differential?
Transitional Cell Carcinoma, Squamous cell carcinoma. [Chronic cystitis, a
trabeculated bladder or a nondistended bladder may show uniform thickening of the
bladder wall.]
Transitional Cell Carcinoma
http://www.pathology.vcu.edu/education/renal/images/dc.15.jpg
•Typical Hx – Smoker, over 50 years old, with hematuria
•90% in bladder, but can arise all along the collecting system.
Time out for a brief technical point…
CT Basics
Artifacts: things that mess up your image.
• Patient Motion
• Volume Averaging – the computer averages
the density of a cubic unit called a “voxel,” and
attributes a brightness to it. So depending on
what is around the structure of interest it can
appear more or less dense on CT.
• Beam Hardening – “streaks” appear because
low energy photons are absorbed by high
density material (metal, bone, etc.).
OK, now back to cases…
CASE #4
Where is the abnormality?
Left click to magnify the image.
Do you see any “beam hardening”?
So, what “attenuation” (density) are these?
Metal
What disease is this person being treated for?
Prostate Cancer. (These are radioactive seeds implanted in
the prostate, “Brachytherapy.”)
Prostate Cancer
•#1 Cancer diagnosis in men.
•Extremely common in older
men.
http://encyclopedia.quickseek.com/imag
es/Brachytherapy.jpg
http://wwwmedlib.med.utah.edu/WebPath/jpeg1/MALE074.jpg
•Brachytherapy
uses radioactive
seeds placed
inside the
prostate.
CASE #5
Do you see an abnormality?
How about if we add some IV contrast?
Can you identify the abnormality now?
Does it enhance with contrast?
Lets look at both images side-by-side.
If you’re not sure just magnify the area of interest.
Is this lesion enhancing or non-enhancing?
Enhancing!
Even if you couldn’t see the contrast in the
lesion, you could check the HU to be sure.
Is this arising in the cortex or medulla?
What is your differential?
Cortex
Renal Cell Carcinoma
Renal Cell Carcinoma (RCC)
•90% solid kidney tumors
•Arises in the cortex from
the Tubules
•Generally enhance 10-25
HU with IV contrast due to
hypervascularity.
http://pathology.catholic.ac.kr/pathology/specimen/kid
ney/sp-36.jpg
• 5% cystic (septae, thick
walls), especially as they
enlarge but still enhance
with contrast.
CASE #6
Where is the abnormality?
What Structure is it involving? Right Adrenal Gland
What density is this lesion?
It’s hard to tell visually, but if you check the HU, it is between
fat and water.
What is your differential?
Adrenal Adenoma,
Functional Adenoma
Adrenal Adenoma
http://www.meddean.luc.edu/lumen/MedEd/Pathology/images/endo30.jpg
• Another common, benign,
asymptomatic “incidentaloma.”
• No history of cancer or Sx
suggesting functional adrenal
tumor (HTN, etc.) supports the
diagnosis
• Low attenuation is due to the
cholesterol content used for
making adrenocorticoid
hormones.
• Fat does not take up contrast
well, so it does not enhance
well and it washes out quickly.
CASE #7
What is abnormal on this slide?
Yes, 2 things!
Remember don’t
stop looking after
you find one
abnormality.
Search all the
structures.
Is this an excretory phase
contrast study?
No, there is no contrast in the
bladder (or there is bilateral
obstruction of the ureters).
So what is this hyperintense opacity? Ureteral Stone.
What will this man present with? LLQ/Flank pain + hematuria.
Are these kidney
stones?
No they are
Phleboliths
(venous
calcifications
common in the
pelvic veins).
They are usually
round, whereas
kidney stones are
not.
So what is the other abnormality?
Is it inside or outside the bladder? Outside
(Follow the bladder
wall around)
Is it homgeneous or heterogeneous? Homogenous
Benign Prostatic Hyperplasia (BPH)
What is your differential?
How could you tell if there is an obstruction?
Look at the ureters and the kidneys.
Do you see any evidence of obstruction?
Yes, there is pelviectasis.
Is this obstruction due to the patient’s ureteral stone or his BPH?
The stone, because the obstruction is unilateral.
Kidney Stones
•Stones < 4 mm almost always pass
spontaneously, those that are 6 mm pass about
50% of the time and stones larger than 8mm rarely
pass spontaneously.
•Acute pressure causes dilatation of the Pelvis
before other collecting structures. Remember the
Law of LaPlace:
•Tension = Pressure x Radius. Therefore the
biggest areas dilate first.
http://www-medlib.med.utah.edu/WebPath/RENAHTML/RENAL005.html
That’s enough for now!
For Further Practice
 Get on PACS and look at CTs and get
comfortable using the software. Then read
the reports to compare what you found.
 Try these web sites for more anatomy and
cases:
http://www.learningradiology.com
http://uuhsc.utah.edu/rad/medstud/Abdomen.htm
References
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Kocakoc, E et al. “Renal Multidector Row CT.” Radiol Clin N Am 43 (2005) 1021 – 1047
Strang JG et al. Body CT secrets. Philadelphia, PA : Mosby Elsevier, 2007.
Webb, WR, et al. Fundamentals of body CT 3rd ed. Philadelphia : Elsevier/Saunders,
2006.
Uzelac, A et al. Blueprints Radiology, 2nd Ed. Baltimore: Lippencott, Williams and
Wilkens, 2006
CT images were obtained from OHSU PACS with findings reported by OHSU faculty.