CT Anatomy and Pathology of the CT Anatomy and Pathology of the Urinary System, Adrenal Glands and Urinary System, Adrenal Glands and

Prostate.Prostate.

By Erik Poyourow MS3

First, some basic CT Principles you First, some basic CT Principles you will need for this learning module.will need for this learning module.

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View the image is as if you were looking up from the patient’s feet.

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CT Basics

CT Basics

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Metal Bone Water Fat Air (tissue and blood)

•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.

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+500 to +1000 HU +300 to -500 HU 0 HU 0 to -50 HU -200 to -1000 HU

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 GLANDSADRENAL GLANDS

•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.

Right Hepatic Lobe

IVC

Right Crus Left Crus

Pancreas

Aorta

Right Adrenal

Left Adrenal

Identify the adrenals and associated structures. Left click for answers.

One more look without the arrows…

Pelvis

Minor Calyx

Major Calyx

Ureter

Medulla

Cortex

Capsule

Renal Artery and Vein *usually arise at L2

KidneysIdentify the following…

http://www.adam-rouilly.co.uk/products/Somso/MU3.jpg

IVC

Head of Pancreas

Aorta

Superior Pole of Left Kidney comes into view first…

Now Back to CT Anatomy

The Right Kidney comes into view a little more inferiorly…

Aorta

IVC

Superior Pole of Right Kidney

Right Renal Artery *exiting the aorta

Left Renal Vein *entering the IVC,

Left Renal Artery

Watch the veins enter the IVC… …watch the arteries exit the Aorta.

SMA

Following the vasculature down…

Left Renal Artery

Left Renal Vein (*between SMA and Aorta)

Right Renal Artery

SMA

Following the vasculature down…

Left Renal Artery

Left Renal Vein

Right Renal Vein *coming off IVC

Right Renal Artery

Left Renal Pelvis *dives down wheras vessels run more horizontal

Following the vasculature down…

Left Renal Artery

Left Renal Vein

Right Renal Vein

Right Renal Artery

Following the vasculature down…

Left Renal VeinRight Renal Vein

Posterior Renal Fascia (“Zuckerkandl’s Fascia”)

(Faint line)

Fascial Compartments

Look very closely!

Anterior Renal Fascia (“Gerota’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.

Note: this is the “Paraconal fascia” continuing anteriorly.

Time out for a brief technical point…

Phases of IV ContrastDepending 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 SystemAnatomy of the Collecting System

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Post Contrast Image (Remember, it helps to visualize the Urinary Collecting System.)

Calyces

Pelvis

Structures related to the ureters

Psoas Muscles

Left UreterRight Ureter

IVC

Aorta

Follow the Ureters Down along the Psoas Muscle

Left Ureter

Left Common Iliac Artery

Right Ureter

Common Iliac Veins

Right Common Iliac Artery

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,

Prostate

Strong work! In the next section try to use your understanding of CT anatomy to identify pathology.

And anterior to the rectum?

Search Pattern

• Adrenal Glands – limbs ≤ 1 cm thick, 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

•Always be systematic in how you look at images.

•Look for what is there and what is absent.

•Don’t stop once you have found one thing wrong.

Urinary CT PathologyUrinary CT Pathology

The following slides show common CT findings.

1. Figure out what kind of image, is there contrast and if so where.

2. Identify the abnormality.

3. Then create a short differential in your head.

By the way, what is the abnormality in this CT image?

•Horseshoe Kidney congenital fusion 1-4/1000.

•3-4 x risk of Transitional Cell Carcinoma.

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…

CASE #1

What is the abnormality?

Hint: don’t forget to look at bones.

Does the pubis symphysis look wide to you?

And what’s herniating out between the pubic bones?

Bladder

Pelvic Symphysis Diastasis

•In pelvic fracture or diastasis, look for traumatic disruption of the urethra and bladder.

http://www.swsahs.nsw.gov.au/livtrauma/education/sudden/pics/pelvis1.jpg

Does this person have 2 Gall Bladders?

Where is the abnormality?

Unlikely… so lets keep scanning down the body.

CASE #2

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/RENAL002.jpg

What is the abnormality?

Thickened bladder wall.

Is this lesion involving other structures around it?

Yes, the Right Ureter is dilated.

What do you expect the Right Kidney to look like?Cortical Thinning + dilated renal pelvis = Hydronephrosis

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.]

CASE #3

Transitional Cell Carcinoma

•Typical Hx – Smoker, over 50 years old, with hematuria

•90% in bladder, but can arise all along the collecting system.

http://www.pathology.vcu.edu/education/renal/images/dc.15.jpg

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…

Where is the abnormality?

Left click to magnify the image.

CASE #4

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.

•Brachytherapy uses radioactive seeds placed inside the prostate.

http://www-medlib.med.utah.edu/WebPath/jpeg1/MALE074.jpg

http://encyclopedia.quickseek.com/images/Brachytherapy.jpg

Do you see an abnormality?

How about if we add some IV contrast?

CASE #5

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!

What is your differential? Renal Cell Carcinoma

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? Cortex

Renal Cell Carcinoma (RCC)

http://pathology.catholic.ac.kr/pathology/specimen/kidney/sp-36.jpg

•90% solid kidney tumors

•Arises in the cortex from the Tubules

•Generally enhance 10-25 HU with IV contrast due to hypervascularity.

• 5% cystic (septae, thick walls), especially as they enlarge but still enhance with contrast.

Where is the abnormality?CASE #6

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

• 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.

http://www.meddean.luc.edu/lumen/MedEd/Pathology/images/endo30.jpg

What is abnormal on this slide?

Is this an excretory phase contrast study?

No, there is no contrast in the bladder (or there is bilateral obstruction of the ureters).

Yes, 2 things! Remember don’t stop looking after you find one abnormality. Search all the structures.

CASE #7

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.

What is your differential? Benign Prostatic Hyperplasia (BPH)

So what is the other abnormality?Is it inside or outside the bladder? Outside

Is it homgeneous or heterogeneous? Homogenous

(Follow the bladder wall around)

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

http://www-medlib.med.utah.edu/WebPath/RENAHTML/RENAL005.html

•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.

That’s enough for now!That’s enough for now!

Get on PACS and look at CTs and get Get on PACS and look at CTs and get comfortable using the software. Then read comfortable using the software. Then read the reports to compare what you found.the reports to compare what you found.

Try these web sites for more anatomy and Try these web sites for more anatomy and cases:cases:http://http://www.learningradiology.com

http://uuhsc.utah.edu/rad/medstud/Abdomen.htmhttp://uuhsc.utah.edu/rad/medstud/Abdomen.htm

For Further PracticeFor Further Practice

ReferencesReferences Kocakoc, E et al. “Renal Multidector Row CT.” Kocakoc, E et al. “Renal Multidector Row CT.” Radiol Clin N AmRadiol Clin N Am 43 (2005) 1021 – 1047 43 (2005) 1021 – 1047 Strang JG et al.Strang JG et al. Body CT secrets. Body CT secrets. Philadelphia, PA : Mosby Elsevier, 2007. Philadelphia, PA : Mosby Elsevier, 2007. Webb, WR, et al. Webb, WR, et al. Fundamentals of body CT 3rd ed.Fundamentals of body CT 3rd ed. Philadelphia : Elsevier/Saunders, Philadelphia : Elsevier/Saunders,

2006.2006. Uzelac, A et al. Uzelac, A et al. Blueprints Radiology, 2Blueprints Radiology, 2ndnd Ed. Ed. Baltimore: Lippencott, Williams and Baltimore: Lippencott, Williams and

Wilkens, 2006Wilkens, 2006

CT images were obtained from OHSU PACS with findings reported by OHSU faculty.CT images were obtained from OHSU PACS with findings reported by OHSU faculty.