Fatty Liver

Axial "in-phase" MR image shows increased signal intensity of the liver.

Axial "opposed-phase" MR image shows decreased signal of the entire liver when compared with the same areas on in-phase image. 

Facts

• Triglyceride accumulation within cytoplasm of hepatocytes
• Can be due to alcoholic liver disease, nonalcoholic fatty liver disease, viral hepatitis, drugs
• May progress to steatohepatitis and cirrhosis
• Avoid the use of "fatty infiltration of the liver", which is misleading because fat deposition in Fatty Liver is in hepatocytes - rarely in other cell types
• Sensitivity/specificity for detection:
• Ultrasound = 60-100% / 77-95%
• Non-contrast CT = 43-95% / 90%
• Chemical-shift MRI = 81% / 100%

MR Imaging

• Because protons in water and fatty acid molecules precess in different resonance frequency, proton chemical shift imaging can be utilized to image this difference
• If images are obtained when fat and water protons are "in-phase", their signals are additive (brighter). If they are "out-of-phase", their signals cancel each other (structure becoming darker)
• Amount of hepatic fat can be quantified by assessing the degree of signal loss

Reference

Hamer OW, Aguirre DA, Casola G, et al. Fatty liver: imaging patterns and pitfalls. Radiographics 2006; 26:1637-1653.

Atypical Hepatic Hemangioma - Echoic Border

Ultrasound images of the liver show a round hypoechoic nodule (arrow, calipers) in the right lobe with an echoic border. Background fatty liver is noted. 

Hemangioma with Echoic Border

• Frequent atypical pattern at ultrasound
• Can have either thick echoic rind or thin echoic rim
• Internal echo is at least partially hypoechoic, which is assumed to represent previous hemorrhage, necrosis, scarring or myxomatous change

Reference:

Vilgrain V, et al. Imaging of atypical hemangiomas of the liver with pathologic correlation. Radiographics 2000; 20:379.

Is Plain Radiography Sensitive Enough to Detect Pneumoperitoneum?

An upright chest radiograph shows a large amount of pneumoperitoneum under the right hemidiaphragm of a patient who has peptic ulcer perforation found at surgery.

Facts: Pneumoperitoneum & GI perforation

• Common
• Requires a breach through all layers of hollow viscus that would allow escape of intraluminal content into the peritoneal cavity
• Results in peritonitis, either localized or generalized

Detectability Rate of Imaging

• Plain radiography sensitivity ranges from 50% to 98% depending on the technique (upright chest, upright abdomen, left lateral decubitus, supine abdomen) and additional postural maneuver
• Recent study of 1,723 patients with GI perforation shows that radiography (either upright chest, upright abdomen or both) has positivity rate of almost 90%. 10% of radiographs did not show free air despite patients having GI perforation. Highest positivity rate was seen with gastric and duodenal perforation (94%), but lowest with appendiceal perforation (7%)

Reference:

Bansal J, Jenaw RK, Rao J, et al. Effectiveness of plain radiography in diagnosing hollow viscus perforation: study of 1,723 patients of perforation peritonitis. Emerg Radiol 2011 December.

Hepatic Hemangioma: MR Findings

Axial MR images show a large left hepatic lobe mass that has a very high T2 signal intensity and peripheral nodular contrast enhancement and incomplete delayed fill-in.

Facts:

• Most common benign hepatic tumor
• Female:male ratio = 2:1 to 5:1
• Most are asymptomatic and found incidentally on imaging exams
• US, CT, MRI and nuclear medicine scan may demonstrate hemangioma
• Routine MR protocol for characterizing liver lesions = T1, FSE T2 (with fat suppression), dynamic gadolinium enhancement

MR Imaging Findings

• A mass with T1 hypointensity, strong T2 hyperintensity with a "light bulb" pattern on heavily T2W sequence
• Dynamic enhancement shows peripheral nodular enhancement (the nodules do not contact each other) with progressive centripetal enhancement. The inner ring of the enhancement is undulating.
• Washout phase: persistent homogeneous enhancement without heterogeneous or peripheral washout
• Small lesions may demonstrate homogeneous arterial enhancement but the enhancement will be persistent and homogeneous in washout phase.

Reference:

Lencioni R, Cioni D, Iartolozzi C. Focal liver lesions: detection, characterization, ablation. 2005

AFP-Negative Hepatocellular Carcinoma

An US image of the liver shows a 2 cm solid nodule in a cirrhotic liver.

CT images of the liver in arterial and portovenous phases show arterial contrast enhancement with rapid washout of the nodule.

Facts: Serum AFP & Hepatocellular Carcinoma (HCC)

• First detection of AFP in serum of HCC patients in 1970s
• Currently, it is the only widely used serologic marker for diagnosing HCC. Additional useful markers in use are AFP-L3 and DCP
• Normal range 10-20 ng/mL
• AFP greater than 400 ng/mL generally considered a point of discriminating HCC from other chronic liver disease
• Problem: about 60% of patients with HCC have AFP below 200, up to 20% have normal AFP (AFP-negative HCC; AFP below 20)

Clinical Features of AFP-negative HCC

• Less likely to be hepatitis B positive
• Tend to have a lower level of ratio of serum glutamic oxaloacetic transaminase (AST)/pyruvic transaminase (ALT)

References:

1. Law WY. Hepatocellular Carcinoma, 2007.

2. Nomura F, Ohnishi K, Tanabe Y. Clinical features and prognosis of hepatocellular carcinoma with reference to serum alpha-fetoprotein levels. Analysis of 606 patients. Cancer 1989;64:1700-1707.

Intussusception Reduction

A "scout" radiograph before intussusception reduction procedure shows a soft tissue mass (arrows) in the right upper quadrant representing the intussusception. There is no free air.

Contrast enema for reduction shows the intussusception (arrows) in the right upper quadrant. It was successfully reduced.

Facts

• Image-guided liquid or air reduction of intussusception is the treatment of choice
• Contraindications for image-guided reduction = peritonitis, free intraperitoneal air due to perforation, in shock or sepsis
• Choice between air, liquid, contrast enema reduction of intussusception depends on radiologist experience and local preference/practice. Most radiologists prefer to use air and it is now generally accepted as the technique of choice
• Air pressure: between 80 and 120 mmHg
• Contrast: bag positioned approximately between 3 ft and 6 ft above the patient
• Reduction rate between 80% to 95%

Preparation for Reduction

• Notify the referring physician and surgeon
• Patient must be stable, well-hydrated and has no evidence of peritonitis
• IV line in place
• A large-bore needle at hand (if you use air reduction)

Complications

• Perforation rates with air enema less than 1%
• Recurrence 10% of cases

Reference:

1. Daldrup-Link HE, Gooding CA. Essentials of Pediatric Radiology: A Multimodality Approach, 2010.

2. Hodler J, Von Schulthess GK, Zollikofer CL. Diseases of the Abdomen and Pelvis 2010-2013: Diagnostic Imaging and Interventional Techniques, 2010.

Intussusception: Ultrasound

A longitudinal US image shows a "pseudokidney" sign of intussusception (arrows). Arrowheads point to enlarged mesenteric lymph nodes within the intussusceptum.

A transverse US image shows a "target" sign with a hypoechoic ring of the intussuscepiens surrouning the central echogenic area of intussusceptum. Arrowheads point to enlarged nodes.

Facts

• A segment of bowel (intussusceptum) prolapses into a more distal bowel segment (intussuscepiens)
• Most frequently seen in the first two years of life but can be seen up to 4 years. If older child has intussusception, looks for a lead point such as polyp, Meckel diverticulum, lymphoma, duplication cyst.
• Classic triad: colicky pain, vomiting and bloody (red currant jelly) stools (seen in less than 25% of cases)
• X-ray is positive in only 50% of cases, and is not reliable in diagnosing this condition

Ultrasound Findings

• Modality of choice to diagnose intussusception
• "Target" sign = hypoechoic ring with an echogenic center on transverse US image
• "Pseudokidney" sign = hypoechoic bowell wall extending along a hyperechoic mucosa
• Helpful in searching for a lead point. US can provide a specific diagnosis in one-third of these cases.

Reference:

1. Daldrup-Link HE, Gooding CA. Essentials of Pediatric Radiology: A Multimodality Approach, 2010.

2. Hodler J, Von Schulthess GK, Zollikofer CL. Diseases of the Abdomen and Pelvis 2010-2013: Diagnostic Imaging and Interventional Techniques, 2010.

Ileal Diverticulitis

Axial CT image shows an ileal diverticulum (arrow) with surrounding inflammation (arrowheads). Thin arrow = normal appendix.

Sagittal CT image again confirms the presence of an inflamed ileal diverticulum. Note a normal cecum.

Facts

• Two percents of population have small-bowel diverticula
• These can be congenital or acquired.
• Acquired diverticula are common in jejunum and terminal ileum. They are mucosal herniation along the mesenteric border.
• About 6-10% of patients with small-bowel diverticula develop complications (-itis, hemorrhage, obstruction, intussusception)

Imaging

• CT can show inflammatory change around the diverticulum with mural thickening of the adjacent bowel loops. The appendix and cecum are normal.

Reference:

Gourtsoyiannis NC. Radiologic Imaging of the Small Intestine, 2002.

Acute Sigmoid Diverticulitis

Axial CT image demonstrates left colonic wall thickening, pericolonic fat stranding, fascial thickening (arrowheads) and an inflamed diverticulum (arrow).

Facts: Acute Diverticulitis

• Diverticular disease found in 5-10% of people over the age of 45 years, and 80% by the age of 80
• Diverticulitis is the most common complication of diverticular disease. It is found in 10-25% of people with diverticular disease at some point.
• Most common site of diverticulitis = rectosigmoid colon
• Diagnosis made on a basis of clinical history (pain, fever, diarrhea), examination (abdominal tenderness, palpable mass), lab (elevated inflammatory markers, leucocytosis) and imaging.

Imaging

• CT is considered the best imaging method for diagnosing diverticulitis and characterizing its complications
• CT findings: diverticula, inflamed diverticula, pericolic fat stranding, colonic wall thickening, phlegmon, abscess, extraluminal air
• Differentiating acute diverticulitis from malignancy can be a problem since many findings overlap. Suspicion for malignancy is high if there are pericolonic lymph nodes and the involved segment is short and eccentric.

Reference:

Buckley O, Geoghegan T, O'Riordain DS, et al. Computed tomography in the imaging of colonic diverticulitis. Clin Radiol 2004; 59:977-983.

Gastric Diverticulum

Fig. 1: Axial contrast-enhanced T1W MR image shows a mass (arrows) in the gastrohepatic ligament with internal low signal intensity, incidentally seen on the study performed for other reason in a young male.

Fig. 2: A coronal-reformatted CT image shows that the mass is filled with air and oral contrast material with a narrow communication (arrows) with the gastric lesser curvature.

Facts: Gastric Diverticulum

• Incidence: 0.02% in autopsy studies, 0.04% on upper GI studies
• True diverticula have complete wall, believed to be congenital. False diverticula are either traction or pulsion, and associated with inflammation or other diseases
• True diverticula commonly arises from the posterior wall of the cardia, 2 cm below the EG junction or 3 cm from the lesser curvature.
• Most are asymptomatic but they may cause epigastric pain, dysphagia, belching, bloating and early satiety.
• Rare complications: bleeding, diverticulitis, perforation and cancer

Imaging

• Thin-walled, air-containing outpouching from the stomach. May contain fluid or gastric content
• Size 1-5 cm, mostly less than 4 cm
• If it is filled only with fluid, it can be difficult to differentiate from cystic tumor on cross-sectional imaging.

References:

1. McKay R. Laparoscopic resection of a gastric diverticulum: a case report. JSLS 2005; 9:225-228.

2. Coakley F. Pearls and pitfalls in abdominal imaging: pseudotumors, variants and other difficult diagnoses. Cambridge University Press, 2010.

Infantile Hypertrophic Pyloric Stenosis

Longitudinal scan of the stomach (as labeled) shows a thickened (5 mm) wall of the pylorus and elongation of the pyloric canal. Labe

Facts: Pyloric Stenosis

• Most common surgical etiology for young infant presenting emergently with nonbillous vomiting
• Incidence: 2 to 5 of every 1,000 infants
• Multifactorial etiology: genetic, biochemical and environmental association
• Hypertrophy of the pyloric muscle, leading to gastric outlet obstruction (vomiting, dehydration, poor weight gain and hypochloremic metabolic alkalosis)
• Average age of presentation = 3 weeks old (rare before 1 week, or after 3-4 months)

Imaging

• US is now the imaging modality of choice for diagnosis of this condition. It can directly show the pyloric muscle
• Elongation of the pyloric canal
• Persistent spasm of pyloric canal with little, if any, fluid passing into the duodenum
• Persistent thickening of the circular muscle in the canal
• Pyloric muscle thickness (one wall) greater than 4 mm, or pyloric length greater than 16 mm (cutoff values vary depending on the sensitivity, specificity needed to make the diagnosis)
• Imaging differential diagnosis is pylorospasm. In pylorospasm, there is usually no thickening of the pylorus (can be up to 2-3 mm) and when visualized in real time the pylorus can open
• If ultrasound is negative, UGI series or nuclear medicine to evaluate for reflux may be necessary.

References:

1. Swischuk LE. Imaging of the newborn, infant and young child, 5th edition.

2. Hernanz-Schulman M, Berch BR, Neblett WW. Imaging of infantile hypertrophic pyloric stenosis (IHPS). Evidence-based Imaging in Pediatrics 2010; 5:447-457.

Peritoneal Sarcomatosis

Axial CT image of the abdomen shows soft-tissue implants and omental caking (arrows) with small ascites.

Peritoneal Surface Malignancy

• Carcinomatosis
• Lymphomatosis
• Sarcomatosis
• Mesothelioma
• Desmoplastic small round cell tumor

Peritoneal Sarcomatosis

• Disseminated intraperitoneal spread of sarcoma in the absence of significant extraabdominal sites of disease
• Rare disease.
• Most commonly due to GI stromal tumor (GIST), liposarcoma and leiomyosarcoma

Imaging Findings

• Similar to other peritoneal surface malignancy: soft-tissue implants along peritoneum and omentum
• Often hypervascular, and with variable amount of ascites (differ from other peritoneal surface tumors)

Our case: Sarcomatosis due to GIST. Ascites is believed to be due to treatment with imatinib

Reference:

Oei TN, Jagannathan JP, Ramaiya N, Ros PR. Peritoneal sarcomatosis versus peritoneal carcinomatosis: imaging findings at MDCT. AJR 2010; 195:W229-W235.

Acute Cholecystitis

Coronal CT images show dilated gallbladder (GB), thickened wall, mucosal hyperenhancement with an obstructing cystic duct stone (arrow) in a 57-year-old man who presents with acute abdominal pain.

Facts: Acute Cholecystitis

• It is a difficult clinical diagnosis. Potential clinical signs that can be helpful to rule in the diagnosis are 1) Murphy sign (positive likelihood ratio = 2.8), 2) RUQ tenderness
• Diagnosis requires a combination of clinical, lab and imaging tests.
• No single clinical finding or lab test has sufficient weight to establish or exclude cholecystitis without further testing (eg, imaging)
• Evaluation of patients with abdominal pain suggestive of cholecystitis continues to rely heavily on the clinical gestalt and diagnostic imaging

Facts: Acute Cholecystitis CT Findings

• Gallbladder distention*
• Wall thickening*
• Mucosal hyperenhancement
• Pericholecystic fat stranding or fluid
• Gallstones (with sufficient attenuation difference from bile to be visualized)
• CT rim sign (increased enhancement of hepatic parenchyma in the gallbladder fossa)
• CT is less accurate than ultrasound in establishing or excluding cholecystitis. However, CT is better to show complications of cholecystitis such as emphysema, gangrene, perforation, abscess or hemorrhage.

* In one study (ref #3), distended gallbladder was considered when size greater than 5 x 8 cm, and thickened wall when greater than 4 mm in noncollapsed gallbladder (short axis greater than 2 cm).

References:

1. Trowbridge RL, Rutkowski NK, Shojania KG. Does this patient have acute cholecystitis? JAMA 2003;289:80-86.

2. Shakespear JS, Shaaban AM, Rezvani M. CT findings of acute cholecystitis and its complications. AJR 2010;194:1523-1529.

3. Fidler J, Paulson EK, Layfield L. CT evaluation of acute cholecystitis: findings and usefulness in diagnosis. AJR 1996;166:1085-1088.

Colonic Closed Loop Obstruction

Supine radiographic study of a 41-year-old woman shows a focally dilated loop of large bowel (star) in the right side of the abdomen. There is little gas in the more distal colon.

Axial CT image shows a dilated right colon (star) with a transition point with a 'whirl-like' appearance (shown on contiguous images) in the mid abdomen (arrow). The rest of the colon is not dilated. Findings are most concerning for closed loop obstruction.

Facts: Closed Loop Obstruction of the Colon

• Colonic obstruction is rarely caused by postoperative adhesion (less than 1%). It is most commonly due to tumor
• CT should be the next imaging work-up to look for a mass. Contrast enema should be omitted due to the risk of perforation
• Closed loop obstruction of the colon usually is due to volvulus, which can be sigmoid (80%), cecal (15%) or involving the transverse colon (5%). Long mesocolon can predispose to malrotated cecum and result in a bascule or volvulus
• Signs of closed loop obstruction on imaging include focally dilated bowel loop with little gas distally and proximally, transition point with a whirl-like appearance at the mesenteric root, mesenteric haziness and free fluid

Our case: transverse colonic closed loop obstruction due to extralong colonic mesentery

Reference:

Halpert RD. Gastrointestinal imaging case review series, 2nd ed, 2008.

Pneumoperitoneum: Right Upper Quadrant Features

A scout CT image shows a linear gas in the right upper quadrant running in an inferolateral to superomedial orientation (arrows). There is gas in the left colonic wall (arrowheads).

Facts: Pneumoperitoneum on Upright Radiograph

• As little as 1mm of free gas can be detected on radiography in an upright position with a horizontal x-ray beam
• If the patient cannot stay upright, a lateral decubitus (preferably patient on the left side) can be performed. Free gas will collect between lateral liver margin and abdominal wall
• Best chance of detection of free gas is when the radiograph is taken after the patient remains in an upright (or lateral decubitus) position for 10 minutes

Facts: Pneumoperitoneum on Supine Radiograph

• More difficult to detect
• Large free gas can be seen indirect as gas collect in different locations
• Right upper quadrant features include 1) linear gas collection running in an inferolateral to superomedial orientation (representing gas in subhepatic space, as in our patient), 2) triangular gas collection right to the spine above the kidney shadow (gas in most posterior recess of the Morrison pouch)
• Visualization of the outer wall of intestine (Rigler's sign)
• Visualization of the falciform ligament of the liver

Our case: pneumoperitoneum due to perforated ischemic colitis.

Reference:

1. Eisenberg RL. Gastrointestinal Radiology: a Pattern Approach, 4th edition, 2003.

2. Menuck L, Siemers. Pneumoperitoneum: importance of right upper quadrant features. AJR 1976;127:753-756.

Microcolon with Features of Low Intestinal Obstruction

Barium enema in a 2-day old boy shows diffuse small caliber of the colon (arrows). Retained barium is noted in the stomach from a recent upper GI study (which was normal). Note the presence of air in the rest of the small bowel (tubular lucent areas in the background) indicating that this is a low intestinal obstruction.

Differential Diagnosis: Microcolon with Features of Low Intestinal Obstruction

• Pathology of colon itself: colonic atresia, diffuse Hirschsprung's disease
• Pathology of distal small bowel (no bowel content can pass into colon resulting in small colon caliber): ileal atresia, meconium ileus

Approach: when seen evidence of bowel obstruction in a neonate, one needs to distinguish between high and low intestinal obstruction. High obstruction presents with little amount of gas in the bowel, dilated stomach and/or duodenum. If high obstruction due to midgut volvulus is suspected, upper GI study is the next step. If low obstruction is suspected, barium enema is performed. In this case, we see a lot of bowel gas in the neonate with clinical intestinal obstruction and a barium enema shows diffuse microcolon - the differential diagnoses are either diseases of distal small bowel or of the colon itself.

Our case: distal ileal volvulus with possible meconium ileus producing distal intestinal obstruction and microcolon

Reference:

Davies SG. Chapman & Nakielny's Aids to Radiological Differential Diagnosis, 5th edition, 2009.

Solid Splenic Lesion

Fig.1: Axial T2 with fat saturation MR image shows a slightly T2 hyperintense lesion in the spleen (arrow).
Fig.2: Axial T1 post contrast with fat saturation reveals homogeneous enhancement of this lesion.

Splenic Lesion Approach

• Solid versus cystic (distinguish by T2 signal intensity and enhancement pattern)
• If solid, is it classic for hemangioma? Is there a history of malignancy elsewhere?
• If cystic, usually represent false cyst (post-traumatic), congenital cyst, abscess

Solid Splenic Lesion

• Benign tumors: hemangioma (most common benign tumor of spleen, same character as liver hemangioma), hamartoma
• Malignant tumors: lymphoma, metastasis (history, multiplicity)
• Others: sarcoidosis, langerhans cell histiocytosis

Our case: splenic metastasis from lung cancer [on imaging, this was not a cyst or hemangioma because its T2 signal was not as high as CSF. It enhanced so it definitely was solid. Differential diagnosis with this solitary solid lesion was hamartoma, solitary metastasis and primary malignancy. Lymphoma, sarcoidosis and LCH usually are multiple].

Reference:

1. Davies SG. Chapman & Nakielny's Aids to Radiological Differential Diagnosis, 5th ed, 2009.
2. Elsayes KM, Narra VR, Mukundan G, et al. MR imaging of the spleen: spectrum of abnormalities. Radiographics 2005;25:967-982.

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Nonvisualization of the Gallbladder with HIDA Scan

HIDA (Tc-99m hydroxy iminodiacetic acid) scan shows normal uptake in the liver with excretion into the extrahepatic bile duct (arrow) and in the bowel (arrowheads) at 25-30 minutes after radiotracer injection. Intravenous morphine was administered at 60 minutes. The images obtained up to 2 hours show no activity in the gallbladder.

Facts: HIDA scan

• Also known as hepatobiliary scan
• Liver uptakes HIDA and excretes it into bile that drains into the bowel
• Normal activity should be seen immediately in the liver, at one hour in gallbladder and into the bowel
• The scan can be done to help diagnose acute cholecystitis, postoperative bile leak
• Morphine can be utilized to shorten the examination time for the diagnosis of acute cholecystitis if the gallbladder is not seen at 1 hour but the bile duct and bowel activity is visualized.
• Cholecystokinin or fatty meal can be used to help diagnose chronic cholecystitis.

Findings on HIDA scan

Nonvisualization of gallbladder WITH bowel activity

• Acute cholecystitis
• Previous cholecystectomy
• Non-fasting patient (including IV feeding)
• Severe hepatic disease
• Chronic cholecystitis (usually fills after 1 hour)

Nonvisualization of gallbladder WITHOUT bowel activity

• Biliary obstruction of any cause
• Severe hepatic disease
• Opiates (because of their effect on the sphinctor of Oddi)

Our patient: acute cholecystitis confirmed at surgery

References:

1. Sharp PF, Gemmell HG, Murray AD. Practical nuclear medicine, 3rd edition, 2005.

2. Chapman S, Nakielny R. Aids to radiological differential diagnosis, 4th edition, 2003

Sinistral (Left-sided) Portal Hypertension

Fig. 1: Axial CT image in a 44-year-old woman shows multiple dilated venous collaterals (varices) along the stomach (arrows).
Fig. 2: Axial CT image of the same patient shows a large pancreatic pseudocyst (stars) with absence of the splenic vein, indicating splenic vein thrombosis from chronic pancreatitis.

Sinistral (Left-sided) Portal Hypertension

• Localized form of extrahepatic portal hypertension developed after splenic vein thrombosis/obstruction
• Formation of varices, with potential for massive upper GI bleeding
• Most common cause = chronic pancreatitis
• Incidence: 7% of patients with chronic pancreatitis
• Potentially curable by splenectomy
• Suspected in patients with bleeding esophageal varices, splenomegaly and normal liver function

Splenic Vein Thrombosis/Obstruction as a Cause of Sinistral Portal Hypertension

• In many patients, splenic vein obstruction is silent and undetected
• Likely related to many factors: compression of the veins by chronic inflammation (i.e. pseudocyst), stasis, intimal injury related to recurrent pancreatitis, systemic hypercoagulable state
• Leads to obstruction of splenic venous outflow. Venous blood from spleen returns to the heart via low-pressure collaterals (short gastric/gastroepiploic veins). This can be seen as gastric varices, and in some cases - esophageal varices.

References:

1. Loftus JP, Nagorney DM, Ilstrup D, Kunselman AR. Sinistral portal hypertension splenectomy or expectant management. Ann Surg 1993;217:35-40.

2. Sakorafas GH, Sarr MG, Farley DR, Farnell MB. The significance of sinistral portal hypertension complicating chronic pancreatitis. Am Surgeon 2000;179:129-133.

Autoimmune Pancreatitis

Fig. 1: Axial CT image of a 61-year-old man with abdominal pain shows mild diffuse enlargement of the pancreas, loss of pancreatic lobulation and minimal peripancreatic fat stranding (arrows).

Fig. 2: An ERCP image (injection of pancreatic duct) shows irregular narrowing of the pancreatic duct (arrowheads).

Facts

• Relatively new, rare disease first described in 1995 by Yoshida et al.
• Chronic pancreatitis characterized by autoimmune inflammatory process (lymphocytic infiltrates) with associated fibrosis of pancreas
• Associated with immunologic abnormalities: hypergammaglobulinemia, elevated serum IgG4 levels and autoantibodies against carbonic anhydrase and lactoferrin
• Pathology shows diffusely indurated and firm pancreas, with periductal lymphocytic and plasma cell infiltrates
• Involvement of the gallbladder, bile ducts, kidney, lung and salivary glands has been described

Clinical

• 5-6% of all patients with chronic pancreatitis
• Men > women, most are > 50 years
• Mostly associated with other autoimmune disease e.g. rheumatoid arthritis, Sjogren's syndrome, inflammatory bowel disease
• Responsive to steroid

Imaging

• On CT, diffuse pancreatic enlargement, enhanced peripheral rim of hypoattenuation "halo", low attenuation "mass" in pancreatic head, homogeneous attenuation and loss of lobularity
• Minimal peripancreatic fat stranding
• Involution of pancreatic tail in long-standing disease
• On ERCP, focal, diffuse or segmental pancreatic ductal narrowing, disappearance of right-angled branches

Reference:

Finkelberg DL, Sahani D, Deshpande V, et al. Autoimmune pancreatitis. N Eng J Med 2006;355:2670-2676.