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Retroperitoneum » Pancreas
Acute focal pancreatitis
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Presentation A 30 year old man presented with a history of a one day non-radiating pain in the epigastrium and nausea. He has a history of significant alcohol consumption.
 
 
 
Caption: Transverse sonogram of the pancreas.
Description: Transverse sonogram revealing an enlarged pancreatic head, with decreased echogenicity of the head and proximal body as compared with the rest of the body and tail.
 
 
 
Caption: Sagittal view of the pancreas.
Description: Sagittal view of the pancreas reveals an enlarged pancreatic head [5x4x5 cm], with a heterogeneous echotexture. The patient had focal tenderness in this region.
 
 
 
Caption: Power Doppler study of the pancreas.
Description: Power Doppler view showing vascularity in the hypoechoic pancreatic head.
 
Differential Diagnosis Focal pancreatitis, pancreatic malignancy.
 
Final Diagnosis Acute focal pancreatitis, secondary to alcohol consumption.
 
Discussion In many cases, transabdominal ultrasound is very sensitive in detecting acute pancreatitis. However, technical factors such as obesity or excessive bowel gas may not allow complete and adequate visualization of the pancreatic gland. In such a scenario, a CT scan or an MRI may be necessary; furthermore, endoscopic ultrasound is emerging as a sensitive modality to evaluate the pancreas. Acute pancreatitis has a male predisposition, with alcohol and gallstones being the most common causes. Mild acute pancreatitis sometimes presents with just focal involvement of the gland, especially the head. In such circumstances, differentiation needs to be made from a pancreatic neoplasm.

Acute pancreatitis can be categorized as mild or edematous and severe or necrotizing. In many cases, ultrasound can distinguish these; a contrast enhanced CT scan or MRI may be necessary to assess the complete extent of necrosis and associated complications, including fluid collections, phlegmon and abscesses. Also, ultrasound and CT scan can provide guidance for intervention, if required.

Focal pancreatitis can present as a mass in the pancreatic head, which can mimic a carcinoma. A recent study by Loren, et al reviewed the sonographic indicators that characterize focal pancreatitis including a hypoechoic, homogeneous, localized, non-expansive and diffusely demarcated lesion mostly in the head of pancreas. Occasionally there might be dilatation of the common bile duct, which would show a gradual narrowing versus an abrupt cut off seen in malignancy. Helical and multi-detector row CT scans are very sensitive to focal pancreatic inflammation, particularly when arterial and venous phase imaging is performed. However, there are no defined imaging criteria with CT, US or MRI that reliably distinguish a focal mass due to pancreatitis from a neoplasm.

Ultrasound contrast agents have been increasingly studied in this respect. A recent study by Becker, et al has reported contrast enhanced power Doppler endoscopic ultrasound as a reliable modality to distinguish between focal pancreatitis and pancreatic carcinoma. Hyperperfused lesion was shown to be inflammatory and hypoperfused area a malignant lesion. The sensitivity for differentiation of pancreatic carcinoma versus inflammatory changes was 94% and specificity 100%. Koito et al reported the utility of US contrast for distinguishing masses due to cancer from those due to pancreatitis. However, studies using other modalities have not supported these results. Johnson, et al in a study showed that gadolinium enhanced MRI could not reliably distinguish the two pathologies.

Thus, a mass-forming pancreatitis [either acute or chronic] can mimic a pancreatic cancer and should be kept in mind when considering the possibility of either. Definitive distinction often requires biopsy, which was performed in this case. Another newer entity that has been described is autoimmune pancreatitis, which also could present as a focal hypoechoic mass, but is more commonly seen, in the elderly age group with patients having elevated serum gamma globulins.

According to the current data available, patients with focal acute pancreatitis usually have normal follow up ultrasound scans after a few months.

 
Case References 1.Panzironi G, et al. Role of USG in the study of patients with acute pancreatitis. G Chir. 1997 Jan-Feb; 18(1-2):47-50.
2.Manfredi R, et al. Imaging of acute pancreatitis. Rays. 2001 Apr-Jun; 26(2):135-42.
3.Monzer M, et al. Improved US Visualization of the Pancreatic Tail with Simethicone, Water, and Patient Rotation. From the 1999 RSNA scientific assembly.
4.Loren I, et al. New sonographic imaging observations in focal pancreatitis. Eur Radiol. 1999; 9(5):862-7.
5.Becker D, et al. Echo-enhanced color- and power-Doppler EUS for the discrimination between focal pancreatitis and pancreatic carcinoma. Gastrointest Endosc. 2001 Jun; 53(7):784-9.
6.Wakabayashi T, et al. Clinical and imaging features of autoimmune pancreatitis with focal pancreatic swelling or mass formation: comparison with so-called tumor-forming pancreatitis and pancreatic carcinoma. Am J Gastroenterol. 2003 Dec; 98(12):2679-87.
7.Koito, et al. AJR 1997 Nov; 169(5):1263-7.
 
Follow Up This patient had elevated amylase and lipase levels and underwent a biopsy which showed focal pancreatitis. A follow up ultrasound performed after six weeks showed a normal pancreatic head.
 
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