Кт картина калькулезного панкреатита

Plain radiography

Pancreatic calcifications are a common finding in chronic calcific pancreatitis and are considered pathognomonic for alcoholic chronic pancreatitis. Calcification primarily represents intraductal calculi, either in the main pancreatic duct or in the smaller pancreatic ductal radicles. Calcification is punctate or coarse, and it may have a focal, segmental, or diffuse distribution.

See the radiographic images of chronic pancreatitis below.

Chronic pancreatitis. Plain abdominal radiograph shows coarse calcification in the distribution of the pancreas due to chronic calcific pancreatitis.

Chronic pancreatitis. Plain abdominal radiograph shows calcification in the pancreas associated with osteomalacia secondary to malabsorption. Note the pseudofracture in the right 11th rib (arrow).

Chronic pancreatitis. Upper gastrointestinal tract barium study shows a reverse 3 in the duodenum due to chronic pancreatitis. Pancreatic carcinoma can have a similar appearance.

Chronic pancreatitis. Plain abdominal radiograph shows a common bile duct stent in situ and fairly extensive pancreatic calcification.

Upper GI tract barium series

Even in the age of cross-sectional imaging, upper GI tract barium series may provide information that is critical to the treatment of patients with chronic pancreatitis.

Esophageal involvement rarely occurs in chronic pancreatitis, and obstruction is usually the result of mediastinal extension of a pseudocyst. Pancreatic enlargement or a pseudocyst may compress the stomach. Peripancreatic fibrosis may involve the antrum of the stomach or duodenum, resulting in stenosis. The anatomic proximity of the pancreatic head and stomach antrum is constant, and enlargement of the pancreatic head usually causes effacement of the antrum; this has been termed the pad sign. Chronic pancreatitis may cause gastric nodularity and thickening of the mucosal folds; these findings are most prominent on the posterior aspect.

Gastric varices secondary to splenic venous thrombosis may have similar findings. The C loop of the duodenum may be widened because of mass effect from an enlarged pancreatic head, or it may be present as an inverted 3 sign due to traction on the medial wall of the duodenum. In the duodenum, mucosal changes occur, such as spiculation, flattening, or slight nodularity of the mucosal folds of the medial border of the duodenum or concentric narrowing due to periduodenal fibrosis.

Small-bowel changes infrequently occur in chronic pancreatitis. Displacement and stretching may occur as a result of pseudocysts. Small-bowel changes may occur as a result of exudation of pancreatic enzymes during the early stages of chronic pancreatitis, when the pancreatic secretory function is still intact. The enzymes may affect the mesenteric vessels at their roots, causing small-bowel ischemia, fibrotic stricture, and malabsorption pattern. As a result of the close anatomic relationship between the transverse colon and the pancreas, the pancreatic enzymes have direct access to the colon.

Changes in the colon include thickening of the haustral folds due to mucosal edema and luminal narrowing. These changes are usually confined to the inferior haustral row of the transverse colon and the splenic flexure. Rarely, fistula formation may occur. All 3 of these colon findings are best appreciated on barium enema examination.

Endoscopic retrograde cholangiopancreatography

Earliest changes are observed in side branches of the pancreatic duct, including dilatation without stenosis, dilatation with downstream stenosis, intraluminal mucosal irregularity, and intraluminal filling defects due to protein plugs or calculi. The number of opacified side branches may be reduced in a focal or diffuse manner because of ductal occlusion. (See the image below.)

Chronic pancreatitis. Endoscopic retrograde cholangiopancreatogram shows a dilated common bile duct (CBD) associated with a stricture of the lower CBD (not well shown on this image) and a dilated ectatic tortuous pancreatic duct. A stent was subsequently placed across the CBD stricture.

In late stages of the disease, changes in the main pancreatic duct are prominent and are similar to those in the side branches, such as ductal dilatation with or without stenosis, short segmental narrowing or long strictures, and intraluminal filling defects due to protein plugs or calculi.

The pancreatic duct may show beading or a chain-of-lakes or string-of-pearls appearance because of alternating stenosis and dilatation of the pancreatic duct.

Small (1-2 cm), round or oval, irregular or well-delineated pancreatic parenchymal cavities may be observed.

Occasionally, contrast material may fill large pseudocysts via fistulous communications. Prolonged emptying of contrast material may be observed.

Common bile duct changes are common in chronic pancreatitis. The most common finding is a long, smooth narrowing of the duct, with gradual tapering of the distal segment due to periductal fibrosis.

In 25% patients with chronic pancreatitis, alternating stenosis and dilation may cause the common bile duct to have an hourglass appearance.

Degree of confidence

The sensitivity of plain abdominal radiography in the detection of pancreatic calcification is approximately 80%, which is higher than that of sonography but lower than that of CT. When seen, pancreatic calcification is pathognomonic for chronic pancreatitis. Barium study findings can be specific for GI tract changes secondary to chronic pancreatitis in the appropriate clinical setting.

ERCP is the most sensitive and specific technique for chronic pancreatitis, although it is invasive and may cause an acute episode of pancreatitis and ascending cholangitis.

False positives/negatives

On anteroposterior radiographs, the spine may mask small punctate calcifications; therefore, the acquisition of additional oblique or lateral images may be indicated. Bowel contents may obscure pancreatic calcification, and calcification in the pancreas and pancreatic bed is not specific for chronic pancreatitis. Causes of pancreatic calcification include acute pancreatitis, cavernous lymphangioma, hemangioma, cystic fibrosis, pancreatic hematoma/infarction, cystadenoma and/or cystadenocarcinoma, islet tumors, metastasis, pseudocysts, and kwashiorkor. Calcification in a vascular atheroma, an aortic aneurysm, or branches of the aorta can occasionally be confused with pancreatic calcification on plain abdominal radiographs.

Gastric displacement seen on barium examination is not specific for chronic pancreatitis and may be due to pancreatic carcinoma, a variety of peripancreatic masses (including adrenal gland or renal masses), aortic aneurysms, exophytic gastric or duodenal tumors, lymphoma and other retroperitoneal tumors, mesenteric cysts, splenic masses, or enlargement of the left lobe of the liver. In some patients, nodular mucosal changes on the medial border of the duodenum may be prominent and may mimic pancreatic carcinoma. Thickened gastric mucosal folds are not specific for chronic pancreatitis; similar thickening can occur with pancreatic carcinoma, lymphoma, gastric carcinoma, gastric sarcoidosis, and Ménétrier disease.

Widening of the duodenal loop is reported as a normal variant, but a similar abnormality is reported with aortic aneurysm; choledochal cysts; duodenal hematoma; retroperitoneal lymphadenopathy; retroperitoneal tumors; parasitic disease; and neoplasms of the stomach, colon, and kidney.

Small-bowel changes in chronic pancreatitis may mimic other causes of intestinal ischemia, Crohn disease, and malabsorption. Colonic changes may mimic vascular ischemia, Crohn disease, and primary colonic carcinoma.

Although ERCP findings can be specific in patients with chronic pancreatitis, they may be confused with those of pancreatic carcinoma in 10% of patients. Such confusion may arise with focal forms of chronic pancreatitis, pancreatic carcinoma extending through the entire pancreas, and coexisting chronic pancreatitis and pancreatic carcinoma.

Intraductal papillary mucinous neoplasm (IPMN) may have imaging findings identical to those of chronic pancreatitis, such as main duct and side-chain dilatation. ERCP can be used to differentiate main duct IPMN from chronic pancreatitis, because the former often shows mucin bulging from the ampulla.

CT features of chronic pancreatitis that can be visualized on CT scans include dilatation of the main pancreatic duct; calcifications; changes in size, shape, and contour; pseudocysts; and bile duct changes.[13, 14]

See the CT images of chronic pancreatitis below .

Chronic pancreatitis. Nonenhanced axial CT scan through the pancreas shows granular calcification in the pancreas.

Chronic pancreatitis. Enhanced axial CT scan through the pancreas shows a low-attenuating mass at the junction of the head and body of the pancreas due to focal chronic noncalcific pancreatitis.

Chronic pancreatitis. Enhanced axial CT scan through the pancreas (in the same patient as in the previous image) shows a mildly dilated pancreatic duct.

Chronic pancreatitis. Nonenhanced axial CT scan through the pancreas shows granular calcification in the pancreas, associated with a 4-cm pseudocyst to the right of the head of the pancreas.

Chronic pancreatitis. Nonenhanced axial CT scan through the pancreas shows a reverse 3 in the Gastrografin-filled duodenum. Note the patchy attenuation in the head of the pancreas. A contrast-enhanced study was not performed because the patient was allergic to intravenous iodinated contrast material.

Chronic pancreatitis. Nonenhanced axial CT scan through the pancreas shows an enlarged pancreas associated with punctate calcification.

Main pancreatic duct dilatation can be demonstrated, with the width of the main pancreatic duct exceeding 5 mm in the head and 2 mm in the body and tail. CT is the most sensitive and specific modality for depicting pancreatic calcifications, which may be tiny and punctate or larger and coarse. Focal enlargement or atrophy of the pancreas is readily demonstrated on CT scans. Focal enlargement associated with calcification or ductal dilatation in a mass is suggestive of chronic pancreatitis.

Obliteration of the peripancreatic fat, which results in poor definition and an ill-defined pancreatic contour, is usually seen in acute exacerbations of chronic pancreatitis. Obliteration of the fat sleeve around the superior mesenteric artery has been described in both chronic pancreatitis and pancreatic carcinoma.

Obstruction of the common bile duct may be visualized as a gradual tapering of the ductal lumen. By contrast, a pancreatic carcinoma usually results in an abrupt transition of the common bile duct. Vascular complications of chronic pancreatitis are best depicted by contrast-enhanced CT scans. In images of pseudoaneurysms, high-attenuation masses are seen during the arterial phase. Portal and/or splenic vein thrombosis and associated collateral venous channels are better delineated during the portal venous phase of contrast enhancement.

Degree of confidence

Currently, CT is regarded as the imaging modality of choice for the initial evaluation of suggested chronic pancreatitis. The diagnostic features of pancreatic enlargement, pancreatic calcifications, pancreatic ductal dilatation, thickening of the peripancreatic fascia, and bile duct involvement are depicted well on CT scans.

CT is more sensitive than plain radiography and ultrasonography in the depiction of pancreatic calcification. Moreover, CT depicts calcification in the pancreas, and confusion with nonpancreatic calcification is less likely. The accuracy of CT is 59-95%; the wide variation is due to the wide discrepancy in the criteria used for diagnosis and in the quality of CT scanners. CT helps in the diagnosis of atrophy of the pancreas, providing better results than ultrasonography.

Pancreatic pseudocysts and complications associated with pseudocysts, including various organ involvements, infection, hemorrhage with pseudoaneurysm formation, rupture with fistula formation, and gastrointestinal or biliary obstruction, are well depicted on CT. Detection of these complications are important, as they may necessitate prompt intervention or surgery.[13, 15]

False positives/negatives

Chronic pancreatitis and pancreatic carcinoma share many CT features, and occasionally, differentiation may be impossible. Obliteration of the fat sleeve around the superior mesenteric artery has been described in both chronic pancreatitis and pancreatic carcinoma.

Pseudotumoral enlargement around focal pancreatitis with extensive fibrous tissue proliferation usually fails to enhance after the administration of contrast material. This characteristic makes the differential diagnosis of pancreatic carcinoma difficult.

In most patients, a normal pancreatic duct is seen on images obtained with T2-weighted short-tau inversion recovery MRI sequences and magnetic resonance cholangiopancreatography (MRCP). MRCP may depict the characteristic beaded appearance of the pancreatic duct in chronic pancreatitis. Pancreatic duct calculi are depicted as round filling defects. In chronic pancreatitis, fat-suppressed T1-weighted images usually show a loss of signal intensity. This loss is explained by the fact that pancreatic fibrosis decreases the proteinaceous fluid content of the pancreas, resulting in loss of pancreatic signal intensity. Fibrosis is associated with decreased vascularity, which causes decreased pancreatic gadolinium enhancement.

See the magnetic resonance images of chronic pancreatitis below.

Chronic pancreatitis. Transaxial T2-weighted MRI scan through the tail of the pancreas shows a dilated tortuous pancreatic duct (arrow).

Chronic pancreatitis. Magnetic resonance cholangiopancreatogram obtained 24 hours after the placement of a common bile duct stent shows good biliary drainage through the stent. Note the dilated tortuous pancreatic stricture and a downstream stricture in the head of the pancreas (left).

Small punctate pancreatic calcification is difficult to detect by using MRI, but larger calcifications may be seen as foci of a signal void. As a result of its ability to depict fluid, T2-weighted MRI may demonstrate pancreatic and common bile duct irregularities and pseudocysts associated with chronic pancreatitis.

Parenchymal gadolinium enhancement is a useful technique in evaluating focal areas of inflammation. Compared with normal pancreatic segments, inflamed areas have decreased enhancement in the arterial phase and increased enhancement in the equilibrium phase.

Currently, the diagnosis of early chronic pancreatitis is difficult. With future improvement in spatial resolution and with the use of secretin-enhanced pancreatography, the detection of subtle changes of the side branches may allow the earlier noninvasive diagnosis of chronic pancreatitis. Secretin-enhanced pancreatography also has the potential to depict the anatomic relationships of pancreatic ducts and pseudocysts and to aid in the evaluation of pancreatic exocrine function.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.

NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness.

Degree of confidence

Because of the introduction of faster imaging sequences and phased-array coils, the accuracy of MRCP has improved considerably, although some concern remains regarding the resolution of smaller pancreatic ducts.

Secretin-enhanced MRCP improves the detection of diseased pancreatic ducts when no abnormality can be shown in physiologic conditions. It also provides additional functional information regarding pancreatic exocrine function. As experience grows, MRI imaging, particularly MRCP, may be increasingly used in assessing and screening for chronic pancreatitis.

False positives/negatives

Standard good-quality protocols are important with MRCP; otherwise, poor examination technique may create false lesions, which may increase the frequency of unnecessary ERCP examinations.

Ultrasonography may be useful in depicting the anatomy of the pancreas. Primary findings on abdominal ultrasonography include changes in the size, shape contour, and echotexture of the pancreas (see the images below). Irregular pancreatic contour is seen in 45-60% of patients, focal enlargement is detected in 12-32%, and diffuse enlargement occurs in 27-45%. Peripancreatic fascial thickening and blurring of the pancreatic margins are seen in approximately 15% of patients.[16, 17, 18]

Chronic pancreatitis. Transverse sonogram shows an echogenic, enlarged pancreas with multiple small hyperechoic nonshadowing foci in the pancreas.

Chronic pancreatitis. Longitudinal sonogram through the head of the pancreas (in the same patient as in the previous image) shows an echogenic pancreas with multiple, small, hyperechoic, nonshadowing foci.

Chronic pancreatitis. A 52-year-old woman known to have chronic pancreatitis presented with moderate left upper quadrant pain. Transverse sonogram through the pancreas shows a 4.37-cm pseudocyst in the tail of the pancreas (arrow).

Chronic pancreatitis. Longitudinal sonogram (in the same patient as in the previous image) shows a pseudocyst at the splenic hilum. Doppler sonogram (not shown) showed no signal in the splenic vein.

In early dis