Abdomen and Pelvic Hybrid Imaging: Anatomy, Variants, Urgent

Abdomen and Pelvic Hybrid

Imaging: Anatomy, Variants,

Urgent Findings David M Schuster, MD with special thanks to

Deb Baumgarten, MD and Courtney Moreno, MD

You are reading a PET-CT for lung

cancer and see this…

Or this…

Is it abnormal?

And what is it?

First review:

Slice by Slice

Correlative Anatomy

Esophagus Aorta

Liver

Esophagus

Esophagus Aorta

Latissimus dorsi

Serratus anterior

Spleen

Stomach

Liver EG junction

colon: splenic flexure

7

8

4a 2

7=posterior, right

(right hepatic vein)

8=anterior, right

(middle hepatic vein)

4a=medial, left

(left hepatic vein)

2=lateral, left

Aorta

Stomach Colon

Spleen Splenic vessels

Fissure for ligamentum venosum Caudate lobe

Pancreas

6

5

4b 3

6=posterior, right

(approximate)

5=anterior, right

(gallbladder)

4b=medial, left

(falciform fissure)

3=lateral, left

Fissure for

ligamentum teres

Adrenals

Hepatic Segments

Aorta IVC Portal vein

Splenic artery

and vein

GB Adrenals

Pancreas

Celiac axis

Colon

Superior

kidneys

Crura of diaphragm

Aorta SMA

origin

Duodenum

Left renal vein crossing

over aorta, not

duodenum

IVC

SMA SMV

Kidneys at hila Right renal vein

Aorta

Colon

Latissimus Serratus posterior

Psoas muscles

Colon

Colon

Small bowel loops (jejunum)

IVC Aorta

a

Inferior

kidneys

Aorta

Small

bowel

loops

3rd portion of duodenum

Colon

Aorta IVC

External oblique Internal oblique

Transverse

abdominus

Rectus abdominis

Ureters

Psoas muscles

Small bowel

loops

Aorta IVC

Colon

Aortic bifuraction

Psoas muscles

Small

bowel

loops

Small bowel

loops

Colon

IVC

bifurcation

Psoas muscles

Ileocecal valve

Common iliac vessels

Small bowel

loops

Psoas muscles

Small bowel loops

Colon

Iliacus muscle

Psoas muscles

Small bowel

loops

Colon Appendix

Ilium Sacrum

Small bowel

loops

Iliacus muscle

External iliac

vessels

Internal iliac

vessels

Gluteus maximus

Gluteus medius

Gluteus minimus

Focal

ureteral

activity

Iliopsoas

muscle

Small bowel

loops

Small bowel

loops

Colon

Sigmoid

colon

Small bowel

loops

Piriformis

Rectum

Ureters inserting into

trigones

Bladder

Seminal

vessicles

Ischium

Obturator

internus

Prostate

Pectineus Obturator

externus Obturator internus

Pectineus Obturator

externus Obturator internus

Pectineus Obturator

externus Obturator internus

Ischial

tuberosity

Anus Penile crura

Testicles

Abdominal Misregistration

Colon projected into liver

Normal Uptake and Variants-

GI Tract

• Widely variable – Must distinguish from pathology

– Usually contiguous but may also be focal

• can also be polyp, cancer

– IBD can also cause false positive uptake

• PET-CT invaluable

• GE junction common – Probably related to LES

GI Tract

• Stomach – Usually mild, diffuse

– More common and intense at fundus

– Can be focal, especially if contracted

– Hiatal hernia

– Intense and focal or distal evaluate

– CT abnormality evaluate

GI Tract

• Small Bowel and Large Bowel – Usually lower intensity and contiguous

– Can be focal

• Especially right colon – Smooth muscle

– Active mucosa

– Lymphoid tissue

– Secretions and microbe flora

Colon and Small Bowel

• Focal or segmental – More intense than liver

• Worry about tumor

– Most will be benign

• CT correlation can be helpful

• IBD/diverticulitis/inflammation

• Colitis – Post-chemotherapy

Prabhakar et al. Radiographics 2007;27:145

Normal Uptake and Variants -

Esophageal

EG

junction

Normal Uptake and Variants -

Esophageal

Hiatal hernia

Normal

stomach

Normal Uptake and Variants - Stomach

Normal Uptake and Variants – Small Bowel

Small bowel

uptake but no

colon

Small bowel

uptake

Normal Uptake and Variants - Colon

Colon Polyp

Liver • Liver

– Normal heterogeneity

– Respiratory artifact

Normal Uptake and Variants – GB

• Physiologic accumulation infrequent normal variant – Murata et al. Nucl Med Biol 2007;34:961

• But uptake in wall – Cholecystitis

– Possibly tumor, especially focal

Adrenal

• No uptake or less than liver is good

• Watch out for necrosis

• Combine appearance on PET with CT

• Intense uptake malignant

Adrenal

• Bilateral adrenal

masses

• Right: low

density

adenoma

• Left adrenal

cancer

Mild uptake left adrenal

low density nodule or

hyperplasia with SUV

of 1.7 and HU of 1.4,

stable on f/u CT 6

months later

Normal Uptake and Variants - Adrenals

72 year old male

lung cancer

MIBG SPECT/CT: Pheochromocytoma

Solid right

adrenal mass

seen well on

CT and

intense on

MIBG

Normal Uptake and Variants – Renal

• Renal excretion of FDG. – Unlike glucose, FDG not well reabsorbed by

tubular cells of the kidney

– Well hydration to wash out renal excretion

– Some advocate lasix

– Patient supine so radiotracer pools in upper collecting system

– Also look for diverticula, communicating cysts, redundant and duplicated ureters

Renal Cyst

Simple cysts should be photopenic

Normal Uptake and Variants – Urinary

• Ureter usually linear, easily identifiable

• Focal ureter activity may look like lymph node but CT fusion helps

• Bladder usually intense but doesn’t obscure with iterative reconstruction

• Look for diverticula, nodules, TURP

• Some advocate foley

• Vesselle HJ. Miraldi FD. FDG PET of the retroperitoneum: normal

anatomy, variants, pathologic conditions, and strategies to avoid diagnostic pitfalls. Radiographics. 18(4):805-24; 1998 Jul-Aug.

Duplicated Right Ureter

Bifid ureter, not adjacent

lymph node

Normal Uptake and Variants – Renal

Use other imaging planes...

Normal Uptake and Variants – Renal

Duplex system on the right

Normal Uptake and Variants – Renal

Focal ureter crossing over iliac vessels, no lymph node

Normal Uptake and Variants – Bladder

Bladder

Even with iterative

reconstruction,

may still cause

some artifact

Normal Uptake and Variants

Bladder Diverticulum

Normal Uptake and Variants – Brown Fat

Brown fat may

be around

diaphragm

and even peri-

renal

Normal Uptake and Variants – Uterine

• Low level uptake is common, but can increase with menses.

• Lerman H, et al. Normal and abnormal 18F-FDG endometrial and ovarian uptake in pre- and postmenopausal patients: assessment by PET/CT. Journal of Nuclear Medicine. 45(2):266-71, 2004 Feb.

– CONCLUSION: In premenopausal patients, normal endometrial uptake of (18)F-FDG changes cyclically, increasing during the ovulatory and menstrual phases. Increased uptake in the endometrium adjacent to a cervical tumor does not necessarily reflect endometrial tumor invasion. Increased ovarian uptake in postmenopausal patients is associated with malignancy, whereas increased ovarian uptake may be functional in premenopausal patients.

Normal Uptake and Variants – Uterine

Uterus with slightly hotter stripe at endometrium Mild ovarian

uptake

Bladder

Young female with benign mediastinal mass

Normal Uptake and Variants – Uterine

Uptake in vagina is not cancer but tampon.

Premenopausal uptake in fibroid

may be intense

Normal Uptake and Variants – Ovarian • Increased unilateral uptake with ovulation (may be bilateral)

• Also look at morphology of ovaries. May need followup.

• Fenchel S, et al. Asymptomatic adnexal masses: correlation of FDG

PET and histopathologic findings. Radiology. 223(3):780-8, 2002 Jun.

– PET positive with 7/12 malignant tumors

– Uptake, even intense, with benign disease at times

• Corpus luteum cysts

• Other benign tumors and inflammation

Normal mild uptake in ovaries

Gastric Cancer

Krukenberg

tumors: Bilateral

uptake, post-

menopausal,

complex appearing

ovaries

Normal Uptake and Variants – Testes

• Normal and decreases with aging – Kosuda S, et al. Uptake of 2-deoxy-2-[18F]fluoro-D-

glucose in the normal testis: retrospective PET study and animal experiment. Annals of Nuclear Medicine. 11(3):195-9, 1997 Aug.

• If see unilateral or very intense, investigate further

Normal Uptake and Variants – Testes

Remember: CT Adds Other Information

• Kamel, et al. Incremental Value of CT in Combined

PET/CT for the Evaluation of Patients with Colorectal

Carcinoma: Initial Experience. Radiology 225 (p):424

– 59 cases

– In 10 patients, CT provided important information which

impacted interpretation

– Also found 15 incidental findings such as renal and

gallstones, etc.

6cm AAA and horseshoe kidney

Pick up the phone…

and you see this…

Ruptured AAA Normal

Aortic Dissection

Pneumoperitoneum

Free air anterior to liver

Small foci of air outside bowel lumen

Pneumoperitoneum

Use Lung Windows to Help

Pneumoperitoneum: Use Other Planes

Pneumatosis and Pneumobilia

Small Bowel Obstruction Due

to Ventral Hernia

Persistent Abdominal Pain in Post-Colon Cancer

Despite Treatment for Recent “UTI”

Appendicitis on Surgery

Acute Appendicitis Normal

Crohn Disease

(DDX infection, inflammation,

ischemia)

Normal

Diverticulitis

Cholecystitis

Ruptured Diaphragm: GB Points Up

Emphysematous

Cholecystitis Normal

Emphysematous Cystitis

Pancreatitis Normal

Pancreatitis

Ascites

Ascites on Liver/Spleen Scan

But Remember This Appearance:

Omental Caking

New Mild Hydronephrosis

New Mild Hydronephrosis

Stone in ureter

Right ureterovesical

junction stone

Left ureteral

stone

Don’t Confuse Pelvic Kidney with Tumor

Knowing CT is Important:

Not All Cancer is Hot

Mucinous

Adenocarcinoma

Recurrence

The End….

Stay tuned for MSK…