Abdominal Imaging 9 topics in 90 min - UCSF CME€¦ · Infection: diagnosed by the presence of gas (in the absence of GI tract fistula) Pancreatic collections 25 Abdominal Imaging

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10/12/20151

Abdominal Imaging9 topics in 90 min

10/12/2015

Antonio C. Westphalen, MD PhDDepartments of Radiology and Biomedical Imaging, and Urology

Outline

Brief description of the problem

Imaging options

• advantages and disadvantages

• main imaging findings

Additional imaging

• further characterization

• follow-up

Focus on most common problems faced by the hospitalist

10/12/2015Abdominal Imaging - 9 Topics in 90 min2

Liver Biliary tree Gallbladder Pancreas Kidneys Small bowel Colon Abscess? Tubes and lines


10/12/20152

Liver

Obese patient

Elevated liver enzymes

RUQ pain

Non-alcoholic steatohepatitis? / cirrhosis?

Non-alcoholic fatty liver disease

10/12/20153 Abdominal Imaging - 9 Topics in 90 min

Liver Biliary tree Gallbladder Pancreas Adrenals Kidneys Small bowel Colon Abscess?

NALFD vs cirrhosis

Ultrasound

Computed tomography

Magnetic resonance imaging

Steatosis may be diffuse or focal; and it is a heterogeneous process.

Non-alcoholic steatohepatitis cannot be diagnosed with imaging.

Cirrhosis: morphologic changes and evidence of portal hypertension.

Imaging options




10/12/20153

Imaging options

Usually the first option when NAFLD is suspected

Inexpensive, safe, readily available on the bed side, and highly accurate

Full assessment of the parenchyma may be limited in severe cases.

Hepatomegaly

echogenicity / smooth vs nodular (split image of spleen – use same setup)

Poor visualization of deep parts of the liver

Ultrasound



Imaging options

Usually best in advanced disease with suspected cirrhosis

Non-contrast CT for steatosis, contrast-enhanced for cirrhosis (GFR>45)

Radiation exposure

Low density compared with spleen on non-contrast CT (difference > 10 HU)

Cirrhosis: nodular contour, widened gallbladder fossa, large caudate

Portal hypertension: large PV (> 12-15mm), collaterals, splenomegaly, ascites

Classical HCC are hypervascular lesions that washout on the delayed phase.

Computed tomography




10/12/20154

Imaging options

Option to CT when suspect cirrhosis

Best to characterize atypical/focal steatosis or indeterminate liver nodules

In general, more sensitive than US and CT to detect fat

Longer scan, breath holds, susceptible to artifacts (e.g. motion of ascites)

In- and out-of-phase imaging

If suspect cirrhosis, better to use gadolinium (contraindicated if GRF<30)




Biliary tree

Patient with cholestasis

Elevated bilirubin, direct > indirect

Elevated alkaline phosphatase

Borderline elevated AST and ALT

Intra- or extrahepatic obstruction?

Cause?

Biliary obstruction




10/12/20155

Intra- or extrahepatic obstruction? Cause?

Ultrasound

Computed tomography


Extrahepatic obstruction is suggested by the presence of dilated ducts

Normal ducts do not exclude acute/new or intermittent obstruction.

Double duct sign (biliary and pancreatic ducts): pancreas, ampulla, scarring

Imaging options



Imaging options

Always the first option for the assessment of bile ducts and gallbladder


May not detect the specific cause and level of obstruction. Bowel gas may obscure visualization of the CBD. Limited in markedly obese individuals.

Try to always use the liver as a window to visualize the entire biliary tree

Change decubitus/position to move air away from the area of interest

Sometimes water PO helps

Ultrasound




10/12/20156

Imaging options

Better than US to determine the specific cause and level of obstruction.

Visualizes the liver parenchyma more consistently than US.

Very limited for CBD stones – most are radiolucent. Radiation (40-50 years old). More expensive than US.

Good option when a tumor is suspected

IV contrast helps to determine the cause (late arterial & portal venous phases)

Planning of percutaneous drainage

Computed tomography



Imaging options

MRI for parenchyma / MRCP for ducts

MRCP – noninvasive and sensitive to detect stones, strictures, or dilatations.

Requires good breath holds, fluid in the duodenum or ascites usually cause artifacts and limit visualization of ducts with MRCP.

Good option when a CBD stone is suspected, but not visualized with US

Option when tumor is suspected & iodinated contrast contraindicated (allergy)

Best option when tumor is suspected & IV contrast contraindicated (low GFR)

Magnetic resonance imaging + MR cholangiopancreatography




10/12/20157

Additional imaging

Diagnostic and therapeutic modality

Imaging and sampling / removal of stones, stents, drains, & sphincterotomy

Limited visualization of bile ducts proximal to the obstruction. Complications (10% risk overall, most commonly pancreatitis)

Standard of reference (high accuracy and excellent spatial resolution)

Best for obstruction at or distal to the confluence of right and left ducts

Consider EUS (+/- FNA) if distal CBD tumor is suspected but not seen by other methods

Endoscopic retrograde cholangiopancreatography (ERCP)



Remember!

Mild central intrahepatic and CBD dilatation in older patients …

… and after cholecystectomy

Biliary ductal dilatation of no clinical significance




10/12/20158

Gallbladder

Biliary colic / acute RUQ pain / Murphy sign

Nausea / vomiting

+/- fever

Leukocytosis / mild cholestasis

Confirm diagnosis and determine cause

Complications?

Acute cholecystitis



Acute cholecystitis? Cause? Complications?

Ultrasound

Computed tomography

Distension of the gallbladder, gallbladder wall thickening, pericholecystic fluid, and gallstones suggest the diagnosis.

Biliary sludge and gallbladder wall thickening without distension and pericholecystic fluid are commonly seen with chronic illnesses.

Ascitic fluid versus pericholecystic fluid

Imaging options




10/12/20159

Imaging options

Always the first option for the assessment of bile ducts and gallbladder


Ultrasonographic Murphy sign

Thick GB walls or pericholecystic fluid? Turn Doppler on and look for vessels!

Are GS mobile? Change decubitus. An impacted stone increases the probability of acute cholecystitis.

Ultrasound



Imaging options

Best option for assessment of complications

May identify extrabiliary causes of acute cholecystitis

Use of IV contrast is recommended

Perforation: decompressed GB, pericholecystic fluid, hyperemia liver tissue

Pancreatitis

Abscess

Computed tomography




10/12/201510

Additional imaging

Equivocal US results or acalculus cholecystitis

Opacification of the gallbladder excludes the diagnosis

Failure to fill the gallbladder suggests acute cholecystitis

FP results: TPN or prolonged NPO, severe liver disease, sphincterotomy

Cannot assess most complications

Cannot assess alternative diagnoses

HIDA cholescintigraphy, or HIDA scan



Pancreas

Acutely ill, hypotensive / tachycardic

Upper / epigastric pain radiating to back

Nausea / vomiting

Elevated amylase & lipase / leukocytosis

Diagnosis?

Stage? Complications?

Cause? (uncommonly)

Pancreatitis




10/12/201511

Diagnosis? Stage? Complications? Cause?

Computed tomography


Usually not indicated if no signs of severe pancreatitis or rapid improvement.

The ideal time to assess complications is 72 hours after onset of symptoms.

To exclude cancer in patients > 40 yo with first episode of pancreatitis without identifiable cause

Imaging options



Imaging options

Primary imaging tool to assess patients with pancreatitis

Part of the revised Atlanta classification as a diagnostic criteria

Also useful to guide percutaneous drainages or other interventions

IV contrast is required – pancreatic protocol (noncon, arterial, portal venous)

Interstitial edematous pancreatitis versus necrotizing pancreatitits

Pancreatic and peripancreatic collections

Computed tomography




10/12/201512

Interstitial edematous versus necrotizing pancreatitits

Localized or diffuse enlargement

Normal homogeneous or slightly heterogeneous enhancement (edema)

Normal or mild inflammation of the peripancreatic tissues

Marked heterogeneous enhancement within the first 5-7 days of onset could be IEP or ill-defined necrosis. CT performed after 5–7 days permits definitive characterization.

Interstitial edematous pancreatitis



Interstitial edematous versus necrotizing pancreatitits

Parenchymal necrosis alone: < 5%

Peripancreatic necrosis alone: ≅ 20%

Parenchymal and peripancreatic necrosis: ≅ 75-80%

Lack of enhancement on contrast-enhanced CT a week after onset

Less than 30% and greater than 30%

Heterogeneous areas with lack of enhancement that contain nonliquefiedcomponents

Necrotizing pancreatitis




10/12/201513

Pancreatic and peripancreatic fluid collections

Acute necrotic collection 4 weeks walled-off necrosis

Acute peripancreatic fluid collection 4 weeks pseudocyst

Sterile or infected

Acute: conform to the anatomic boundaries and have no discernable wall

Chronic: round or oval surrounded by a well-defined enhancing wall

Infection: diagnosed by the presence of gas (in the absence of GI tract fistula)

Pancreatic collections



Imaging options

Suspected choledocholithiasis not yet visualized

Characterize collections - nonliquefied material may mimic fluid of CT

CT is contraindicated (eg, allergy to iodinated contrast or pregnancy)

Cost and availability

Accuracy MRI = CT

CT is used to guide procedures





10/12/201514

Additional imaging

Gallstones and/or choledocholithiasis

Guide drainage of collections

Vascular assessment (venous thrombosis / pseudoaneurysms)

Ultrasound



Chronic pancreatitits

Parenchymal atrophy, PD dilatation and calcifications (CT only)

Acute on chronic? Peripancreatic fluid/necrosis > parenchymal findings!

Pancreatic cancer?

Stenosis of the duct?

Computed tomography and magnetic resonance imaging




10/12/201515

Adrenals

Incidental findings

Associate with endocrine symptoms

Subclinical with hormonal imbalances

Known primary cancer

Diagnosis?

Nest step?

Adrenal nodules



Diagnosis? Next step?

Computed tomography


The goal of imaging is to characterize and adenoma versus a nonadenoma

Dx of adenomas: intracytoplasmatic lipid and/or enhancement characteristics

1/3 of adenomas are lipid-poor

Imaging options




10/12/201516

Imaging options

Primary imaging tool to diagnose adenomas

Adrenal protocol: unenhanced CT plus/minus PV & delayed phases (≅12 min)

Imaging guided biopsy

Low density (< 10-15 HU) on unenhanced CT: very high specificity and PPV

Contrast washout characteristics (40% to 60% on delayed phase)

Computed tomography



Imaging options

Generally used to characterize indeterminate lesions on CT

Detection of microscopic lipid

Breath holding, not useful if unenhanced CT density > 30 HU

Relative signal loss from in-phase to out-of-phase images

Virtually diagnostic of adenoma





10/12/201517

Additional imaging

Reserved for patients with known primary cancer to exclude metastasis

Indicated to investigate of masses > 4 cm, in lieu of biopsy

Meta-analysis (patients with known primary cancer):

Sensitivity = 97% / Specificity = 91%

⊕ LR = 11.1 / ⊖ LR = 0.04

PET-CT



Beware!

Metastases of renal cell carcinoma may have washout equivalent to adenomas

Metastases of hepatocellular carcinoma may have microscopic fat




Computed tomography


10/12/201518

Kidneys

Flank pain / renal colic

Hematuria

History of urolithiasis

Diagnosis

Obstruction? Probability stone passage?

Complications?

Urolithiasis



Urolithiasis

Ultrasound

Computed tomography

KUB

Consider history of urolithiasis and characteristics of symptoms

Consider patient’s age (radiation exposure)

Consider pre-test probability of alternative diagnosis

Imaging options




10/12/201519

Imaging options

Possibly the first option if known urolithiasis and classical symptoms

Inexpensive, safe, readily available on the bed side

Limited assessment of midureter due to gas in the GI tract

Hydronephrosis

Scan pelvis with bladder slightly full to better visualize distal ureter and UVJ

Change patient decubitus to move gas / slow and continue pressure

Ultrasound



Imaging options

First option if nonclassical symptoms and need to exclude other causes of pain

Visualizes virtually all stones, sensitivity ≅ 90%

Radiation exposure – young patients with repeated episodes of renal colic

Noncontrast CT suffices in the vast majority of cases / IV if no urolithiasis

Scan prone to more completely assess UVJ stones

6 mm threshold (axial plane) for spontaneous passage

Computed tomography




10/12/201520

Ultrasound or computed tomography?


Westphalen AC. Acad. Emerg. Med. 2011 Jul;18(7):699-707




Westphalen AC. Acad. Emerg. Med. 2011 Jul;18(7):699-707



10/12/201521



Smith-Bindman R. N Engl J Med 2014; 371:1100-1110


Imaging options

Option to assess passage of stones after treatment (PNL of staghorn calculus)

Easy to obtain in the bed side, little radiation

Limited for the initial assessment of suspected urolithiasis

• overlap of bowel content and bones

KUB




10/12/201522

Additional imaging

Rarely used nowadays

Intravenous pyelography



Complications

Calyceal rupture is a minor complication, usually treated with stenting

Contrast-enhanced CT (delayed/excretory phase)

Pyonephrosis is a medical emergency and requires immediate drainage

Limited renal ultrasound

Interventional radiology

Calyceal rupture and pyonephrosis




10/12/201523

Small bowel

Abdominal distension / pain

Nausea / vomiting

History of abdominal surgery

Diagnosis?

If SBO, cause?

Management?

SBO versus ileus



SBO vs ileus

Computed tomography

KUB

Initial assessment = computed tomography

KUB may be an option for follow-up

Imaging options




10/12/201524

Imaging options

Better first option for initial assessment of suspected SBO

Fast, more sensitive than KUB, identifies a cause in ~ 80% of cases

IV contrast (nonadhesive causes), PO contrast (transition point)

SBO = proximal dilated loops of SB (> 3 cm), decompressed distally (RLQ)

Ileus = diffuse distention, often borderline, normal stool/air in colon

SBO in developed countries = adhesions (> 2/3 of cases)

SBO in developing countries = incarcerated hernias (up to 80% of cases)

Computed tomography



Imaging options

May be used for follow-up of patients with SBO

50-60% sensitive for SBO, does not identifies cause of SBO

Abdominal series (at least one standing or left lateral decubitus)

SBO = air fluid levels at various heights, central predominance, with paucity of gas distally and in colon

SBO = gasless abdomen if dilated and fluid filled SB, or after vomiting

Ileus = borderline dilatation with air found throughout SB and in colon

KUB




10/12/201525

Additional imaging

Not for diagnostic use

Predict the need of surgery and (?) shortens the course of partial SBO

Usually done 48 hours after unsuccessful conservative therapy

Contrast reaches the colon in 4-6 hours = conservative treatment

Contrast does not reach the colon in 12 hours = surgery

KUB with PO Gastrografin (Diatrizoate Meglumine)



Closed loop obstruction

25% risk of strangulation and infarction

Marked segmental distension of bowel, often C or U shape

"beak sign": tapering bowel loops at the point of obstruction

”whirl": tightly twisted mesentery

Contrast enhanced CT, due to high risk of ischemia and infarction

Computed tomography




10/12/201526

Bowel ischemia

Imaging appearance similar independent of cause

Unenhanced, late arterial phase, and portal venous phase of enhancement

Contrast enhanced CT due to high risk of ischemia and infarction

Wall thickening and free fluid

Hyperemia or decreased enhancement of wall

Pneumatosis intestinalis, pneumoperitoneum, pneumatosis portalis

Computed tomography



Colon

Diarrhea, fever, abdominal pain

Abdominal distension

Leukocytosis

Broad-spectrum antibiotic use

Diagnosis?

C. difficile colitis? Or another cause?

Complications?

Pseudomembranous colitis




10/12/201527

Diagnosis? Complications?

Computed tomography

KUB

Colonic distension

(Diffuse) marked wall thickening, “thumbprinting”

Toxic megacolon (perforation)

Imaging options



Imaging options

More sensitive option for the diagnosis of colitis and its complications

Etiology is suggested, but not necessarily definitively established

Sensitivity and specificity approximately 85% and 48% (colonic abnormalities)

IV contrast, no PO contrast

(Diffuse) marked wall thickening, “thumbprinting”

Paucity of pericolonic inflammation may help differentiate from other colitides

Computed tomography




10/12/201528

Imaging options

Easy and quick exam, but normal early in the disease

Useful for follow-up (q 12-24h); may identify development of toxic megacolon

Bowel dilatation, mural thickening and thumbprinting on more advanced cases

Underestimate the severity of disease

Limited for detection of small pneumoperitoneum

Abdominal series preferable to KUB

KUB



Additional imaging

Limited role in the diagnosis

Contraindicated in patients with severe (perforation)

Barium enema




10/12/201529

Toxic megacolon

Nonobstructive colonic dilatation plus systemic toxicity

Marked distension > 6 cm transverse segment

Loss of hautral markings, pseudopolyps, and air-fluid levels

Risk of perforation high if cecum > 12 cm

Ischemia

Pneumoperitoneum

KUB or CT



Remember!

Must consider the clinical setting

Interpretation of scans is improved with adequate history

Imaging findings often not specific for a particular etiology


Song KS. Yonsei Med J. 1992 33(2):168-72.



10/12/201530

Abscess

Post operative/trauma/infection/inflammation

1 to 3 weeks to develop

Fever, abdominal pain, anorexia

Nausea, ileus, weight loss

Leukocytosis

Diagnosis

Treatment planning



Diagnosis? Treatment planning?

Computed tomography

Ultrasound

Walled-off collection

Amenability to percutaneous drainage

Exclude associated complications, e.g. venous thrombosis

Imaging options




10/12/201531

Imaging options

Primary imaging modality (diagnosis and drainage)

IV (diagnosis) and oral contrast (drainage) are helpful

Collection with enhancing walls and mass effect

(Complex) fluid attenuation

Presence of gas is the most specific finding

Adjacent inflammatory findings (fat stranding/fluid)

Computed tomography



Imaging options

Easy, fast, and cheap to perform in the bedside

Better for superficial, rather than deep abscesses

Operator dependent

Collection with thick walls and flow on color Doppler

Complex fluid (floating echos)

Gas is the most specific finding (echogenic and mobile foci with dirty shadow)

Turn on color Doppler to find vessels prior to any percutaneous interventions

Ultrasound




10/12/201532

Additional imaging

Equivocal US and CT results

Elaborate procedure, requires strict patient collaboration

½ of abscesses are identified by 4 h after injection, more than 90% by 24 h

FP results: interpretation must refer to CT findings

FN results: chronic abscess (> 3 weeks); lymphocytic mediated infection, e.g. TB or other granulomatous processes; abscess in or adjacent to liver or spleen

111In-leukocyte scintigraphy ?



Thank You!

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Documents

Abdominal Imaging 9 topics in 90 min - UCSF CME€¦ · Infection: diagnosed by the presence of gas (in the absence of GI tract fistula) Pancreatic collections 25 Abdominal Imaging