Epigastric Pain

Epigastric Pain

Joyce Grube and Kathryn Kuntz

Initial sonographic evaluation of a patient with epigastric pain may reveal a broad spectrum of findings. If the pancreas appears normal, the clinician must include inflammation of the pancreas and other pathology not related to the pancreas among the differential diagnoses. Diagnoses not specific to the pancreas may include gastric or duodenal ulcer disease, gastric reflux disease or esophagitis, diverticulitis of the transverse colon, biliary disease, liver abscess, heart disease, or aortic dissection. Diseases that cause epigastric pain specific to the pancreas are discussed in this chapter.

Although computed tomography (CT) plays a primary role in evaluation of the pancreas for disease, sonography is more readily available, is more cost-effective, and offers a nonradiation alternative for the evaluation of epigastric pain. The pancreas is often thought of as the most difficult organ in the abdomen to image. Sonographers may improve visualization of the pancreas by employing (1) a complete understanding of the surrounding anatomy and gastrointestinal structures, (2) persistence while scanning, (3) image optimization, and (4) oral contrast agents.

Nonetheless, sonography plays a significant role in the evaluation of patients with jaundice, serial examination of inflammatory processes, and needle guidance for interventional procedures of the pancreas.


Normal Sonographic Anatomy

The pancreas is a retroperitoneal organ that lies in the anterior pararenal space of the epigastrium. The entire pancreas is contained between the C-loop of the duodenum and the splenic hilum. The parts of the pancreas include the head, uncinate process, neck, body, and tail (Fig. 4-2). A normal adult pancreas is approximately 12 to 15 cm in length. A normal pancreatic duct may be visualized at a measurement of 2 mm or less.

The echogenicity of the pancreas is isoechoic to hyperechoic compared with the liver and may increase with age and obesity because of fatty infiltration. In children, the pancreas may appear proportionally larger and more hypoechoic to isoechoic compared with the liver because of less fat composition.

The lie of the pancreas in the epigastrium is transverse yet slightly oblique, with the head located more inferior than the tail. The pancreas is a nonencapsulated organ, so the borders are indistinct on sonography. The sonographer must have a thorough understanding of the surrounding vasculature to aid in the detection of the pancreatic boundaries (Fig. 4-3).

The sonographer must also appreciate the portions of the gastrointestinal tract that surround the pancreas and make visualization difficult. The fundus of the stomach lies superior to the pancreatic tail. The body of the stomach lies anterior to the pancreatic tail. The pylorus lies anterior to the pancreatic body and neck. The superior duodenum (first portion) lies anterior to the pancreatic neck and superior to the head of the pancreas. The descending duodenum (second portion) lies lateral to the head. The horizontal duodenum (third portion) lies inferior to the pancreatic head. The ascending duodenum (fourth portion) lies inferior to the body of the pancreas. The transverse colon lies anterior and inferior to the entire length of the pancreas (Fig. 4-4). Identification of the various portions of the gastrointestinal tract during scanning allows the sonographer to change the patient position to move obscuring bowel away from the pancreas.

Harmonics may enable the sonographer to optimize visualization of the pancreas, especially in technically difficult cases. Harmonic imaging is based on the concept that an ultrasound pulse interacts with tissue, and echoes are created at the original or fundamental frequency along with echoes at multiples of the original frequency (i.e., a 2-MHz pulse generates echoes at 2 MHz, 4 MHz [second harmonic], 6 MHz,

, 8 MHz
). Conventional ultrasound listens to the fundamental frequency and ignores the harmonic frequencies. Tissue harmonic imaging typically uses the second harmonic frequency for improved image clarity. Harmonic imaging in the abdomen may also reduce image artifacts, haze, and clutter, and significantly improve contrast resolution (Fig. 4-5).

If the pancreatic tail is the primary area of interest, the sonographer or physician may elect to use an oral contrast agent to complement the study. A cellulose suspension should remain in the stomach for an adequate period to provide an acoustic window for better visualization of the pancreatic tail. Alternatively, distilled water can be used to enhance visualization (Fig. 4-6). Although oral contrast agents are not yet used consistently in day-to-day practice, the use of intravenous ultrasound contrast agents shows significant potential.


Acute Pancreatitis

Acute pancreatitis is characterized by the escape of toxic pancreatic juices into the parenchymal tissues of the gland. These digestive enzymes cause destruction of the acini, ducts, small blood vessels, and fat and may extend beyond the gland to peripancreatic tissues. Acute inflammation of the pancreas is generally caused by one of two factors: biliary disease and alcoholism. Other sources of inflammation may include trauma, pregnancy, peptic ulcer disease, medications, hereditary factors, systemic infections, posttransplant complications, and iatrogenic causes (e.g., endoscopic retrograde cholangiopancreatogram [ERCP] endoscopy). Patients with acute pancreatitis have a sudden onset of persistent midepigastric pain that may be moderate to severe and often radiates to the midback. Fever and leukocytosis accompany the attack. Classically, serum amylase levels increase within 24 hours of onset, and lipase levels increase within 72 hours.

Sonographic Findings

The pancreas may appear normal in the early stage of acute pancreatitis, with no noticeable change in the size or echogenicity of the gland. Once changes become evident, acute pancreatitis may have a diffuse or focal appearance on sonographic examination. The pancreatic duct may be enlarged in either presentation. Diffuse disease causes an increase in size and a decrease in echogenicity from swelling and congestion (Fig. 4-7). The borders of the pancreas may appear irregular. Focal inflammation may be seen as enlargement and a hypoechoic appearance to a specific region of the gland. If focal pancreatitis is present in the pancreatic head, biliary dilation and a Courvoisier’s gallbladder may also be appreciated. The sonographer must carefully evaluate the pancreatic head for adenocarcinoma and the biliary tree for the presence of cholelithiasis and choledocholithiasis as possible causes of pancreatitis.

Chronic Pancreatitis

Chronic pancreatitis is defined as recurrent attacks of acute inflammation of the pancreas. Further destruction of the pancreatic parenchyma results in atrophy, fibrosis, scarring, and calcification of the gland. Stone formation within the pancreatic duct is common, and pancreatic pseudocysts develop in 25% to 40% of patients.1,2 Patients generally have progressing epigastric pain. Jaundice may also be seen in patients with a distal biliary duct obstruction.

Sonographic Findings

On sonography, the pancreas generally appears smaller than normal and hyperechoic because of scarring and fibrosis. Diffuse calcifications are the classic sonographic feature of chronic pancreatitis and are usually noted throughout the parenchyma, causing a coarse echotexture (Fig. 4-8, A). Stones may also be visualized within a dilated pancreatic duct (Fig. 4-8, B and C). Associated findings include pseudocyst formation, cholelithiasis, choledocholithiasis, and portal-splenic thrombosis.

Aug 27, 2016 | Posted by in ULTRASONOGRAPHY | Comments Off on Epigastric Pain
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