GALLBLADDER

functions as a reservoir for bile produced by the liver. It is 7-10 cm long, 3 cm wide at its broadest measure, and has a capacity of 30-50 mL

divided into 3 regions: fundus, body, and neck

bile produced by the left and right portions of the liver travel through the right and left hepatic ducts (1-2 mm in diameter). These two ducts join to form the common hepatic duct

the common hepatic duct lies anterior to the portal vein and to the right of hepatic artery

the common hepatic duct descends roughly 3 cm before the cystic duct (3-4 cm long) from the gallbladder joins it from the right

the common bile duct passes posterior to the first portion of the duodenum. It then descends via a groove on the superolateral portions of the posterior head of the pancreas sometimes traveling through the pancreas head. The four portions of the duodenum are labeled in white.

at the head of the pancreas, the common bile duct meets the pancreatic duct, and they exit into the second part of the duodenum, forming the hepatopancreatic ampulla (ampulla of Vater)

Adenomyomatosis one of the many causes for gallbladder wall

thickening pathologically, it is identified by proliferation of the

gallbladder mucosa with diverticular outpuochings known as Rokitansky-Aschoff sinuses

typically cholesterol deposits are seen within the gallbladder wall and cause a comet tail artifact

Causes of GB wall thickening biliary causes include:

-acute cholecystitis, gall bladder carcinoma, polyps, as well as adenomyomatosis

nonbiliary causes include:-CHF, hepatitis, pancreatitis as well as AIDs

cholangiopathy

Acute Acalculous Cholecystitis represents inflammation of the gallbladder in the

absence of demonstrated calculi

the disease process is distinct from the calculous variety, in which the primary initiating event is believed to be obstruction of the cystic duct

typically occurs as a secondary event in patients who are hospitalized and acutely ill from another cause

Pathophysiology at least 3 mechanisms

a. systemic mediators of inflammation and traumab. biliary stasisc. generalized or localized ischemia

in turn, the mechanisms often result in functional or secondary mechanical obstruction of the cystic duct from inflammation and bile viscosity

Sonographic signs compatible with acalculous cholecystitis

gallbladder wall thickening sonographically localized tenderness over the GB subserosal edema pericholecystic fluid gallbladder distention biliary sludge presence of gas

CT findings

gallbladder wall thickening mucosal irregularity luminal distention increased bile density (biliary sludge) intramural or intraluminal gas intraluminal hemorrhage localized pericholecystic fluid collections inflammatory infiltration of pericholecystic fat indistinctiveness of the liver-gallbladder interface

Acute Cholecystitis sonographic criteria for acute cholecystitis

-a thickened gallbladder wall (normal GB wall- <3 mm)

other sonographic findings-gallstones-positive Murphy’s sign-pericholecystic fluid as well as sonolucencies within

the gallbladder wall (indicates gallbladder wall edema)

Complications empyema gangrene perforation

Epigastric Pain

Chronic Cholecystitis with GB polyps chronic inflammation of the gallbladder results from

recurrent attacks of acute cholecystitis fibrotic reaction usually causes the gallbladder to

become small and contracted

Diffuse Wall Thickening most frequent gallbladder wall abnormality detected

by ultrasound the wall is >3mm thick this appearance is neither sensitive nor specific for

an inflammatory process

Case-patient is a 72-year old woman who presents with nausea and vomiting

Porcelain Gallbladder has been termed calcifying cholecystitis,

cholecystopathia chronic calcaria, or calcified gallbladder

are 5 times more common in women than in men most often considered a sequel of low-grade chronic

inflammation some have postulated that it is secondary to

intramural hemorrhage or an imbalance in calcium metabolism

Cholelithiasis is the pathologic state of stones or calculi within the

gallbladder lumen 75-80% of gallstones are of the cholesterol type 10-25% of gallstones are bilirubinate of either black

or brown pigment in Asia, pigmented stones predominate, although

recent studies have shown an increase in cholesterol stones in the Far East

Complications biliary colic- 56 % acute cholecystitis- 36 % acute pancreatitis- 4 % choledocholithiasis- 3 % gall bladder cancer- 0.3 % cholangitis- 0.2 %

Gall Stones

appear as single or multiple filling defects within the gallbladder and are densely calcified, rim calcified, laminated, or have a central nidus of calcification

stones also may present as a soft-tissue density or a lucent filling defect within the bile. Some stones may contain air

most gallstones have no signal on MRI and present as signal void-filling defects within the gallbladder

on T2-weighted sequences where signal-void stones are contrasted against high-signal bile

on T1 weighted sequences, bile usually shows a homogenous low signal

signal-void stones also may be apparent on T1-weighted images

high signal may be seen occasionally on T2-weighted images within stones that contain bile within clefts

stones with high fatty acid content may demonstrate high signal on T1-weighted images

Porcelain gallbladder along with distention and filled with sludge and calculi

associated with chronic gallbladder inflammation and gall stones in 95 % of cases

it appears as an echogenic arc with dense posterior shadowing

Carcinoma of the Gallbladder the most common primary hepatobiliary carcinoma the fifth most common malignancy of the GI tract predominantly affects older persons with long-

standing cholecystolithiasis GB epithelial tumors tend to behave similarly to

other GI adenocarcinomas GB tumors occur in the fundus in 60 % of patients, in

the body in 30 %, and neck 10 % early lymphatic spread occurs to the retroperitoneal,

right celiac, and pancreaticoduodenal nodes direct invasion of the liver, extrahepatic biliary ducts,

and duodenum, and colon occurs intraperitoneal seeding may occur

Ultrasound findings GB wall thickening single or multiple intraluminal mass extraluminal mass extending to the liver polyps larger than 1 cm in diameter

Extraluminal mass extending to the liver this often is accompanied by a large mass replacing

the GB fossa the mass often is complex with areas of necrosis

visible this is the most common manifestation of GB

carcinoma, accounting for 40-65 % of GB carcinomas

US shows echogenic mass adherent to gallbladder fundus (arrows). CT shows enhancing mass within the gallbladder (arrows) with involvement of the liver (arrow head)

LIVER

unique in having a dual blood supply- 75 % originating from the portal venous system and-25 % arising from the hepatic artery

the hepatic veins are responsible for drainage of filtered blood from the liver into the IVC

3 Functional Lobes right left caudate

the right and left lobes are further divided into 2 segments each:

-the anterior and posterior segments of the right lobe

-the medial and lateral segments of the left lobe

Segments

1-Caudate lobe2-Left superior lateral subsegment3-Left inferior lateral subsegment4a-Left superior medial subsegment4b-Left inferior medial subsegment5-Right inferior anterior subsegment6-Right inferior posterior subsegment7-Right superior posterior subsegment8-Right superior anterior subsegment

Bacterial (Pyogenic) Abscess 80-85 % of all abscesses are bacterial in origin bacteria gain access to liver via the portal or biliary

system. Possible causes are iatrogenic, biliary disease, diverticular disease, trauma, and inflammatory bowel disease

E. coli and anaerobes are the two most common offending agents in pyogenic abscess

most pyogenic abscesses occur in the right lobe

Radiogrpahic Findings (US) heterogenous, rounded masses with irregular,

thickened walls and poor peripheral definition fluid and debris inside the abscess can create

internal echoes gas-containing lesion also has acoustic shadowing

CT

heterogenous lesion with irregular margin (arrowhead) and possible peripheral enhancement

internal septations or papillary projections 20 % contain gas

Amebic Abscess trnasmitted by fecal-oral route

the organism, E. histolytica, first infects the colon, then gains access to the liver via portal venous system

patients generally present with right upper quadrant pain

Radiographic Findings (US & CT) indistinguishable from bacterial abscess. Tends to be

peripheral in location

CT Findings

generally non specific including: a peripherally based, round or oval low density

lesion which often demonstrates a peripheral rim of slightly higher attenuation

the peripheral rim will often enhance with contrast administration

Echinococcal Abscess dogs are the main intermediate hosts of hydatid

disease eggs get ingested, hatch in the stomach and

duodenum, travel to the liver via portal venous drainage, encyst in the liver and grow slowly

the cysts can exert mass effect on the surrounding liver and biliary system. The right lobe of the liver is most frequently involved

the cysts can rupture into the pleural cavity, peritoneal cavity, alimentary canal, or biliary tree, causing profound shock, peritonitis, and anaphylaxis

Radiographic Findings (US)

double-layered cyst, “classic” double-line sign, water lily sign, racemose

Diffuse Hepatic Disease

Cirrhosis

Causes alcohol alpha 1-antitrypsin postnecrotic (hepatitis) metabolic disease: Wilson, hemochromatosis,

glycogen storage disease congestive heart failure

Pathology hepatocyte necrosis fibrosis nodular regeneration

Radiographic Findings

Signs of advanced necrosis liver surface nodularity contracted liver with ascites atrophy of the posterior segments (VI, VII) of the

right lobe enlarged caudate lobe (I) and lateral segments (II, III)

of the left lobe prominent umbilical vein irregular enhancement

US- advanced cirrhotic liver appears to be nodular, irregular, and contracted with relatively enlarged caudate lobe (C) and lateral segment (L) of the left lobe. Fatty infiltration and fibrosis give a coarse echotexture of the liver parenchyma

Contrast CT: areas of fibrosis and regeneration may become isodense to parenchyma. The surface of the liver may be very nodular in cirrhosis

development of collateral vessels in portal hypertension

splenomegaly and the presence of ascites

Diffuse Fatty Infiltration a reversible process in which triglyceride

accumulates diffusely in hepatocytes causing abnormal appearance on imaging

normally, less than 5 % of the liver is composed of fat. In diffuse fatty infiltrated liver, fat can make up to 50 % of the liver tissue

commonly seen in acute or chronic alcohol abuse (most common), obesity, diabetes, cystic fibrosis, tetracycline, steroids, chemotherapy, malnutrition, and hyperalimentation

clinically, patients are asymptomatic. Liver can be enlarged but without splenomegaly

Radiographic Findings (US)

the liver has increased focal or diffuse echogenicity when compared to the surrounding organs such as the kidneys

Noncontrast CT- the liver looks hypodense to the spleen due to fatty infiltration, making the hepatic vasculature more prominent

Hemochromatosis iron overload leads to deposition in the liver. The

liver can be enlarged primary hemochromatosis: an autosomal recessive

disease that has abnormal absorption of iron in the intestine and thus causes iron to be deposited in hepatocytes, spleen, pancreas, and the myocardium

secondary hemochromatosis: caused by multiple transfusions with deposition of iron in the reticuloendothelial cells of the liver and the spleen. However, the pancreas is not usually involved. If the pancreas is involved, the hemochromatosis is usually of the primary type

CT: hyperdense liver (>75 HU). There are similar findings in Wilson’s disease, amiodarone toxicity, and previous thorotrast exposure

T1 and T2 weighted MRI: liver and spleen are hyperintense (very dark liver) compared with adjacent muscles owing to paramagnetic effect. Normally, the signal intensity of the liver

parenchyma is equal to or slightly greater than that of muscle

Simple Cysts the most common liver masses may be solitary or multiple cysts are found in 2-10 % of population, has

increased frequency with age and is more common in females aged 50-70

true hepatic cysts have bile duct origin and cuboidal epithelial lining. They are idiopathic, usually asymptomatic and variable in size. They cannot be distinguished from cysts that arise from prior hematomas or abscesses

they can be associated with other disease processes such as tuberous sclerosis and polycystic kidney disease

40 % of patients with polycystic kidney diseae have liver cysts

60 % of patients with multiple liver cysts have polycystic kidney disease

Radiographic Findings

US (95-99 % accurate) anechoic posterior enhancement (increased transmitted

sound) well-defined or imperceptible walls

Non-contrast CT: density of less than 20 HU, well-defined margins, no perceptible wall (arrow)

Contrast CT: no enhancement after contrast administration

MRI

T1 weighted- homogeneously hypointense (arrowhead)

T2 weighted- homogeneously hyperintense (arrow) due to water property (comparable to the intensity of CSF or gallbladder bile

Differential Diagnosis cystic liver mass with internal echoes, thick

septations, or a perceptible wall noted on US include-hemorrhagic cyst-abscess-echinococcal cyst-biliary cystadenoma-cystic metastasis (e.g. ovarian)-HCC with necrosis

Hemangioma is a benign proliferation of vascular tissue lined with

endothelium which has slow hepatic arterial blood flow

two types are capillary (more common) and cavernous

occurs in the right lobe can easily be confused with metastases or hepatoma the most common cause of a hyperechoic liver mass

on US large hemangioma may appear heterogenous. There

may be thrombosis or a central stellate scar with a giant hemangioma

US: hyperechoic and well-defined

T1 weighted MRI- hypointense to liver (arrows). If gadolinium-diethylenetriamine penta-acetic acid (Gd-DTPA) is used, peripheral enhancement is seen initially with central enhancement within 15-30 minutes. Enhancement is persistent

T2-weighted MRI- hyperinetense to the liver (just like a cyst; arrows). Looks as bright as a light bulb! Intensity is as high as that of pure fluid (CSF or bile)

Focal Nodular Hyperplasia most likely seen in young women (3 %)

Pathology a non-capsulated nodular mass was thought to be a vascular/hamartomatous

malformation is composed of normal hepatocytes, Kupffer cells,

and bile ducts but arranged abnormally is less than 5 cm in diameter, most commonly found

peripherally in the right lobe

classic appearance: solitary, well-circumscibed mass with a central stellate scar of fibrosis even though the central scar is seen in only 20 % of the cases

Non-contrast- the lesion has low attenuation (arrows) compared with the normal liver. The central stellate scar may also show low attenuation

Contrast CT: the lesion shows homogenous enhancement early in arterial phase (arrows) with prompt wash out. The central stellate scar will not enhance.

T1-weighted MRI: The lesion is hypo-isointense to the normal liver. The central scar enhances with Gd-DTPA.

T2-weighted MRI: The lesion is isointense to slightly hyperintense to liver. The central scar is hyperintense to the liver (arrows). (In contrast to hypointense appearance of the central scar in large hemangioma)

Hepatocellular Carcinoma (HCC)

the most common primary hepatic tumor and one of the most common cancers worldwide a primary malignancy of hepatocyte origin

3 Growth Patterns of HCC

Solitary mass – often large Multifocal or Nodular Pattern – multiple nodules Diffuse – multiple, small foci scattered diffusely

throughout liver

US Findings

Small HCCs can be homogenously hyperechoic and can mimic hemangioma. This can result when a large proportion of fat is present in the tumor

Small HCCs can appear hypoehcoic with larger HCCs frequency mixed in echogenicity.

In the Portal Venous Phases

Small lesions may be isodense or hypodense and difficult to see, since the remainder of the liver increases in attenuation.

Larger lesions with necrotic regions remain hypodense.

Contrast CT: dense diffuse non-uniform enhancement in arterial phase; some lesions are hypervascular

MRI

T1-weighted: usually hypointense to normal liver. When fatty change, fibrosis, or copper is present, variable signal can be seen.

With Gd-DTPA, hypervascular lesions enhance early in the arterial phase.

Liver Metastasis

The liver is the most commonly involved organ by metastatic disease, after the lymph nodes.

The most common primary sites are the eye, colon, stomach, pancreas, breast and lung.

In children the most common liver metastases are from a neuroblastoma, Wilm’s tumor or leukemia.

Causes of Echogenic Metastases

Mucinous adenocarcinoma of the colon, Pancreatic carcinoma (usually hypoechoic but possibly becoming echogenic as calcification occurs), Gastric carcinoma (usually hypoechoic), HCC, Neuroblastoma, Cholangiocarcinoma, Treated Breast Carcinoma, Renal cell Carcinoma, Carcinoid,

Choriocarcinoma, Pancreatic Islet Cell tumors, Wilm’s Tumor (usually spread to the lungs), Kaposi sarcoma, Myeloma deposit, Hepatic chloroma

Causes of Hypoechoic Metastases

Lymphoma (especially AIDS related), HCC, Pancreatic carcinoma, Lung (particularly adenocarcinoma), Cervix, Melanoma, Nasopharyngeal carcinoma, Kaposi sarcoma (rare, most are hyperechoic), Myeloma deposits, Cystic liver metastases, Mucinous cystadenocarcinoma colon, Cystadenocarcinoma ovary. Cystadenocarcinoma pancreas, Leiomyosarcoma, Squamous cell carcinoma, Testicular CA, Carcinoid, Graunulosa cell ovarian tumor.

Cystic metastases

Two groups of patients tend to get cystic metastases:

(1) Patients who have a primary neoplasm with a cystic component such as a mucinous cystadenocarcinoma of the colon, stomach, pancreas, or ovary and,

(2) Patients with metastases that are undergoing central necrosis, when low-level echoes and wall irregularity is seen. Squamous cell carcinoma, leiomyosarcoma, melanoma, and testicular carcinoma, have a propensity to undergo extensive central necrosis.

Causes of Bull’s Eye or Target, Metastases

The halo is most probably related to a combination of compressed normal hepatic parenchyma around the mass and a zone of cancer cell proliferation

The presence of a halo usually suggests aggressive behavior

Bronchogenic carcinoma Breast and colon as well as Primary malignant liver neoplasms (eg.

HCC) and Benign liver neoplasms (eg. Adenoma in

glycogen storage disease)

Causes of heterogeneously Echogenic Liver Metastases

Breast, colon and/or rectum, stomach (especially anaplastic lesions) and cervix

Other causes of heterogeneously liver metastases include the ff: HCC (especially when complicated with hemorrhage), carcinoid, melanoma, and bronchogenic carcinoma.

Portal Vein Thrombosis

Five causes of portal vein thrombosis:

1. Pancreatitis2. Cirrhosis3. Hepatic or biliary surgery4. Hepatoma with tumor thrombus5. Hypercoagulable states

CT: example of carcinoma in the hepatic vein

PANCREASAcute Pancreatitis

Common cause of pancreatitis include alcohol abuse, choledolithiasis, hypergylceridemia and hypercalcemia. Acute pancreatitis usually presents as an acute episode of upper abdominal pain, with or without accompanying GI symptoms.

Other symptoms may include fever, hypotension, pulmonary edema or shock. Laboratory values reveal elevated WBC, serum amylase and pancreatic lipase. Initial treatment of pancreatitis includes NPO, NG suction, analgesics, parenteral or jejunal feeding. Prophylactic antibiotics may also be of benefit.

Ranson’s score estimates the life threatening complications or death in patients with acute pancreatitis using several factors at the time of admission and during the first 48 hours thereafter.

Ranson’s Score

Values at Admission First 48 Hours

Age>55

WBC >16,000/ml

Glucose >200mg/dl

LDH>350 U/L

AST > 250 U/L

Hct fall >10%

Ca >8mEq/L

BUN rise > 5mg/dl

PaO2 < 60mmHg

Base defect > 4 mEq/L

Fluid sequestration > 6L

Number of Criteria Mortality

0-2

3-4

5-6

≥7

<5%

15-20%

40%

>99%

Balthazar et al developed a classification system for patients with acute pancreatitis based on radiologic findings

Balthazar et al Radiographic Grading of Acute Pancreatitis

Grade Radiographic Findings Prognosis

Grade A

Normal appearing pancreas

Grade B

Focal or diffuse enlargement of the pancreas

Mild, uncomplicated course

Grade C

Pancreatic gland abnormalities associated with pancreatic fat infiltration

High risk of complications associated with acute pancreatitis

Grade D

Single fluid collection

Grade E

Two or more fluid collections.

Nausea, vomiting with abdominal pain that radiates to the back

Acute Necrotizing Pancreatitis

Pancreatic necrosis is a known complication of acute pancreatitis.

Areas of necrosis are usually multifocal and rarely involve the entire gland.

Necrosis develops earl in severe pancreatitis and is usually established within 96 hours of the onset of clinical symptoms.

Pancreatic Pseudocysts

The most common cystic lesions of the pancreas accounting for 75-80% of such masses

A collection of amylase-rich, lipase-rich, and enterokinase-rich fluid

Most frequently located in the lesser peritoneal sac in proximity to the pancreas

Large pseudocysts can extend to the paracolic gutters; pelvis; mediastinum

Some are loculated

Most Common Etiologies

Chronic pancreatitis Acute pancreatitis and Pancreatic trauma In addition, pseudocysts are associated with

pancreatic ductal obstruction and pancreatic neoplasms

US Findings

An anechoic structures associated with acoustic enhancement

Well defined and round or oval, and they are contained within a smooth wall

During the early phases, the more complex, with varying degrees of internal echoes

Usually, this appearance results from the presence of necrotic pancreatic and peripancreatic debris and is more common in pseudocysts that form as a result of acute necrotizing pancreatitis than in others. The debris is cleared over time.

The pseudocysts can appear more complex in 2 other instances: when hemorrhage occurs in the cyst or when infection of the cyst complicates the clinical course

Color Doppler or duplex scanning should always be performed in cystic lesions to ensure that the lesion in question is not a giant pseudoaneurysm

Abdominal CT is an excellent choice for imaging acute fluid collections and pancreatic pseudocysts

CT characteristics of an acute fluid collection include low attenuation and a homogenous appearance

CT attenuation values may measure greater than 20-30 HU because of the presence of necrotic pancreatic or peripancreatic debris or blood within the confines of the acute fluid collection.

Pancreatic Cancer

The findings of an invasive hypodense mass in the had of the pancreas which involves the SMV and SMA along with enlarged lymph nodes are most suggestive of pancreatic CA

The 5th most common cause of cancer deaths It is approximately twice as common in males

compared to females Patients are usually greater than 50 years old Greater than 90% of pancreatic cancers are

ductal adenocarcinoma and its variants Most of the remaining 5-10% are islet cell

tumors Arises in the head of the pancreas 70% of the

time, in the body 20%, and in the tail 10%. Abdominal pain and weight loss are present in

greater than 75% of patients with pancreatic cancer, and jaundice is present in greater than 80% of patients with pancreatic heat tumors secondary to biliary obstruction

CT

The best modality for imaging the pancreas A mass deforming the size and contour of the

pancreas is the most common finding for ductal cell carcinomas occurring in 96% of the cases

A central zone of decreased attenuation is present in 83% of pancreatic head and 60% of pancreatic body carcinomas

CT can be used for staging purposes with the findings of the retroperitoneal extension, major vascular involvement, invasion of contiguous organs, ascites, LN and distant metastases suggesting unresectability.

Adenocarcinoma

The fourth most common cancer The prognosis of the disease is poor and very few

patients survive longer than one year Major role of imaging once the primary diagnosis has

been made is to “stage” the disease to determine operability

The loss of the fat plane indicates encasement of the artery making the patient uncurable

CT Findings of Pancreatic CA

Alteration in the morphology of the gland with abnormalities of CT attenuation values

Obliteration of peripancreatic fat Loss of sharp margins with surrounding structures Involvement of adjacent vessels and regional lymph

nodes Pancreatic ductal dilatation Pancreatic atrophy and, Obstruction of the common bile duct (CBD)

Mucinous Cystic Neoplasm

Mucinous Cystic Tumors

So called macrocystic cystadenomas or, cystadenocarcinomas.

Predominate in the body and tail of pancreas, have a strong female predilection

Most common of cystic pancreatic tumors, accounting for 45-50% of tumors

Multiloculated tumors with a characteristic smooth glistening surface

Arise from oversecretion of the mucus of the hyperplastic columnar lining of the ducts. The cysts contain thickened viscous material, which can also be hemorrhagic

Nonenhanced CT scans show a well-defined unilocular or multilocular, externally smooth, round-to-ovoid mass with fluid attenuation

The attenuation values of the multilocular cysts vary according to the degree of hemorrhage or protein in the mucoid cysts

Larger cysts may demonstrate small daughter cysts along its internal surface. Typically, they show a well defined, multilocular cystic mass with thick internal mass septae separating the separating the different cystic cavities of varying sizes. The cysts are 2-26cm.

Visualization of the nodule with irregular borders of the septae and calcification which is curvilinear or punctate and confined to the cyst wall or septa

CECT show enhancement of the cyst wall, internal septations, mural nodules, and other intracavitary projections

CT may also allow the identification of solid components associated with cystic elements, which are features of borderline or malignant tumors but

not benign variants. MCN’s develop predominantly in the tail of the pancreas (>90%)

CT more clearly demonstrates enhancement of the cystic walls and septa

US Features

Usually larger than 5cm The walls are composed of thick, fibrous stroma

sometimes containing dystrophic calcification A large cystic mass sometimes with numerous septa

and debris The tumor may be 2-23cm, and they usually have

sharply marginated walls and smooth borders Typically show a multilocular, fluid-containing mass

with good transmission and strong acoustic enhancement

Compared with serous cystic tumors, the cysts in MCNs are larger (>20mm in diameter) and less numerous (usually <6). CT-guided aspiration of the cyst can provide further diagnostic clues and enable their differentiation from other pancreatic cystic masses (eg, pseudocyst, serous cystadenoma, and solid and pseudopapillary neoplasm)

MCN cyst fluid typically has a high viscosity, low amylase levels, and high CEA and carbohydrate antigen (CA) 72-4 levels, and they may show malignant cytology in patients with mucinous cystadenocarcinomas. Periodic Acid-Schiff (PAS) and May Grunwald/Giemsa (MGG) stains are usually positive for extracellular as well as intracellular mucin.

Mucinous Cystic Neoplasm

Intraductal Papillary Mucous Neoplasm

Papillary neoplasm that arises within the MPD or its branches

The tumor hypersecretes mucin, which often leads to duct dilatation and/or chronic obstructive pancreatitis

Are premalignant and may histologically demonstrate areas ranging from hyperplasia to carcinoma within in a single tumor

The tumors generally show intraluminal, longitudinal growth but is usually slow to invade periductal tissues radially and slow to metastasize.

Most commonly localized to the head of the pancreas, but they may occur at any site along the pancreatic ductal system

Ductal dilatation is often impressive any may mimic MCNs on CT scans

Is recognized as predominantly a solid tumor with a central cyst. The cystic variety consists microscopically of cyst like spaces with papillary protrusions.

Intraductal Papillary Mucinous Tumor

In these cases, the findings on ERCP may be diagnostic. Rarely, segmental pancreatic duct dilatation may acquire a cystic appearance, whereas the MPD and the rest of the pancreas appears normal.

Microcystic Adenoma

Cystic mass in the region of the tail of the pancreas.

Hypervascular tumor in the pancreatic tail with sunburst calcification. Note the Swiss-cheese enhancement.

SPLEENAccessory Spleens

Or splenculi, are relatively commonly encountered “normal” anatomic variants

Estimated to be present in approximately 10% of the population

May be single or multiple in occurrence Are most frequently discovered in the vicinity of the

splenic hilum or elsewhere within the gastrosplenic ligament

They may, however, be found along the omentum, or anywhere else within the peritoneal cavity

CT Findings

Attenuation and contrast-enhancement characteristics that are identical to those of normal spleen

Measures approximately 1.0-1.5cm in diameter, but may range in size a few millimeters to several centimeters (2.3)

Resection of all accessory spleens is recommended at the time of the splenectomy, as cases of accessory-splenic hypertrophy have been described subsequent to removal of the “main” spleen

Accessory Spleen (s)

Splenic Cysts

The differential diagnosis of large splenic cysts should include posttraumatic cysts (most common), epidermoid cysts, abscess, pancreatic pseudocyst, echinococcal cysts, lymphoma, infarction or cystic lymphangiomas (less common). Splenic cyst shown below as imaged on US.

An example of calcified splenic cyst shown first on plain radiograph (left) with a coronal CT construction (right). Note the clear demarcation of the calcified cyst capsule.

Metastases: the axial CT images demonstrates multiple hypoenhancing lesions in the spleen consistent with metastatic CLL.

Images of splenic metastasis visualized on US. Careful ultrasound examination can determine if these are cysts with increased through transmission of echoes versus solid metastatic lesions.

Lymphoma

Lymphomas is the most common malignant tumor of the spleen. Typically, lymphatic drainage to the spleen serves as the primary mechanism by which extranodal lymphomas of varying types by which extranodal lymphomas of varying types disseminates to the spleen. Of the two broad types of lymphoma (B vs. T cell), B cell lymphomas Hodgkin’s and non Hodgkin’s disease are often diagnosed from splenic

imaging. Primary splenic lymphoma (PSL) is a rare malignancy with a reported incidence of less than 1% of all lymphomas.

Case

Twenty-three year old woman with non-Hodgkin’s lymphoma.

Splenic Calcifications

Infectiouso Previous granulomatous disease

(tuberculosis, histoplasmosis)o Opportunistic infection in AIDS patients

(Pneumocystis carinii) Traumatic Vascular

o “phleboliths”o Post-ischemic/infarction

The plain film shown demonstrates numerous round calcifications diffusely distributed specifically within the spleen. The likely etiology of the calcified granulomata is Histoplasmosis, which have this characteristic appearance in comparison to microabscess.

Case

33-year old woman with fever of unknown origin. Patient is HIV +.

Pneumocystis carinii infection in the spleen

Important cause of pneumonia in an immunocmporomised host

Common sites of dissemination include lymph nodes, liver, bone marrow, and spleen.

Splenic pneumocystic carninii infections have been described typically as low attenuation lesion which may contain internal calcifications.

Differential diagnosis of cystic lesions

Post traumatic Epidermoid Epithelial and Echinococcal cyst Abscess Lymphoma and Metastatic lesions may also appear as regions of

decreased attenuation in the spleen that may mimic cystic lesions

Splenomegaly

lymphoma leukemia cirrhosis portal hypertension