CT of fluid collections associated with pancreatitis

1121 CT of Fluid Associated Stanley S. Siegelman1 Bruce E. Copeland George P. Saba John L. Cameron Roger C. Sanders Elias A. Zerhouni Collections with Pancreatitis Fluid collections are an important component of severe pancreatitis because they may produce a detectable mass and may be responsible for prolongation of fever and pain. Among 59 cases of clinically verified pancreatitis, 32 were shown by CT to be complicated by pancreatic collections, surface diagnosed of the gland Extrapancreatic pararenal space and/or extrapancreatic in 1 6 patients, and were were covered fluid collections (I 5), posterior only fluid typically by a thin were detected pararenal space collections. Pancreatic on the anterior layer fluid or anterolateral of fibrous connective tissue. in the lesser sac (1 9 cases), anterior (six), in or around the left lobe of the liver (five), in the spleen (three), and in the mediastinum (one). The potential undesirable consequences of escape of pancreatic juice are necrosis, abscess formation, or prolonged inflammation of the peripancreatic tissues. Relative preservation of pancreatic integrity as observed by CT was regularly found in patients with large extrapancreatic fluid collections, suggesting that escape of pancreatic juice produces a beneficial decompression of the pancreatic duct system. Pancreatitis may be associated of the pancreas and/or into the peripancreatic with a leakage tissues [1 capsule, of duct collections disruption. of pancreatic If secretions surrounds the the gland, , an exudation of pancreatic 2]. Although of fluid juice with into the interstitium its proteolytic enzymes the pancreas does not have a firm juice may remain as focal masses in the region breech the thin layer of connective tissue that anterior pararenal space and the lesser sac are immediately involved. Although the term pseudocyst has been applied to any collection of fluid seen in or around the pancreas in association with pancreatitis, pancreatic fluid collection’ as the more appropriate designation for we prefer ‘ ‘ ‘ an accumulation of fluid that does not extend beyond the thin connective tissue layer covering the gland, and ‘extrapancreatic fluid collection’ for fluid that has tracked beyonds the bounds of the pancreas into the surrounding tissues. The distinction between pancreatic and extrapancreatic fluid collections is illustrated ‘ infigure The many Received vision January August 30, 20, 1 979; accepted after re 1980. Presented in part at the annual meeting of the American Roentgen Ray Society, Toronto, March 1979, and as a scientific exhibit at the annual meeting of the Radiological Society of North America, Atlanta, November 1979. All authors: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, Baltimore, MD 21205. Address reprint requests to S. S. Siegelman. the the 1. pancreas patients gland and extensive a moderately pancreatitis full recovery inflammation wide is a self-limited within 3-5 and tissue spectrum of response disease days. At the destruction with transient other end of the is life threatening. to insult. In edema of spectrum, Severe acute pancreatitis with ‘pancreatic burn” may result in exudation of up to 30% of the total blood volume into the pancreas and peripancreatic tissues [2]. For such hypotensive patients, massive amounts of intravenous colloid are generally required [3]. In addition to patients at these extremes, there are others with abdominal pain, tenderness, distension, nausea, vomiting, low grade fever, and elevation of serum amylase persisting beyond the usual duration of a mild attack. Proper management for these individuals is currently a source of concern. ‘ Information AJRI34:1121-1132, June 1980 0361 -803x/8o/1 346-1121 $00.00 © American Roentgen Ray Society exhibits acute ‘ is needed on the of pancreatic and peripancreatic CT has the potential to offer natural history of the disease and the significance fluid collections in these patients. information on the incidence and distribution of 1122 SIEGELMAN Extrapancreatic fluid collections El AL. 20 or AJR:134, 50 mA examination Poeterior layer Pancreatic fluid of peritoneum a flavored collections and a slice of the pancreas, 3% examination, methylglucamine solution and thickness of of 5 or patients were diatrizoate 30 an intravenous diatrizoate and June 1980 1 0 mm. For given 240 ml of mm before the injection of 1 00 ml of 60% an additional 240 ml of the oral contrast mixture immediately before Scanning began at the level of the umbilicus the examination. and progressed every 2 cm cephalad until the third part of the duodenum was visualized and then at 1 cm intervals until the entire pancreas had Method been visualized. of Interpretation All examinations Fig. 1 -Pancreatic and fluid collections in lesser space (second commonest are confined by thin layer collections represent focal extrapancreatic fluid collections. Extrapancreatic sac (commonest location) and anterior pararenal collections location). Two large ‘ ‘pancreatic’ ‘ fluid of fibrous connective tissue. Intrapancreatic fluid accumulations of pancreatic juice at site of duct rupture. fluid collections cusses (1) complicating 1 year CT in the diagnosis pancreatitis. of experience of pancreatitis; locate fluid collections collections in and around This at a single (2) how report dis- institution Cl with was used to (3) data on the incidence of fluid the pancreas; and (4) the potential role of CT in the detection of pancreatic no focal areas and no calcification; (2) nation of enlargement and pancreatic of decreased cation edema attenuation; duct, chart mation, than of various before the study 21 2, pancreatic 1 95, pelvic hepatic 1 1 3, abdominal loskeletal 37, adrenal 1 3, and Among the 1 95 patients in 1 91 parts the head or the spine were at the Johns Hopkins Hospital. was classified , of the body performed on 1,026 Each examination by primary interest: thoracic 1 92, renal or retroperitoneal (intraperitoneal) 40, muskucervical 13. whom the pancreas was the area of interest, 60 patients were either clinically diagnosed as having pancreatitis or were being evaluated for possible pancreatitis. plasms with Examinations were done abdominal pain for possible in 1 35 patients. was clinically parenchyma or markedly irregular duct, pancreatic of the in figure varieties pancreatic neo- An occasional suspected patient of having either were evaluated the diagnosis by examination a 6-month If there 1 1 3 hepatic, and interest lay elsewhere cidentally. Method All scanner 40 pancreatitis was the abdominal) in whom but the pancreas was the visualized chief in- of acute (model pancreatitis was considered final discharge diagnosis was acute pancreatitis. The diag- nosis of chronic pancreatitis was considered confirmed if the patients had a history of several clinically documented attacks of acute pancreatitis. Most of the cases were included in a prospective study of the accuracy of Cl versus sonography have an in pancreatic overall accuracy carefully analyzed disease in which Cl was found to of 90% [4]. Among the more 32 cases of complicated pancreatitis, 15 were proven by surgical exploration (cases 2-8, 1 2, 1 7, 18, 20-22, 30, and 32). Three were proven by aspiration of fluid collection which contained a high concentration of amylase (case 9, pleural effusion; cases 1 4 and 28, hepatic collections). not to assess The ary etiology tract drug nificant Since the the accuracy for the disease, the purpose pancreatitis included hyperlipoproteinemia, induced pancreatitis, correlations could and main of this of CT in all cases of the alcoholism, viral disease is of complicated interest. bil- pancreatitis, and familial pancreatitis. be found between the appearance paper of pancreatitis, as studied No sigetiologic by CT. Results were 500) hospital established if the patient had an acute illness with abdominal pain associated with elevation of serum amylase and the agent of Examination examinations of fluid of the but rather to evaluate the role of CT in cases pancreatitis, these patients were of greatest in whom chief consideration; (2) 1 35 patients in whom the pancreas was the focus of attention but the clinical diagnosis was possible neoplasm; and (3) 344 patients (1 91 retroperitoneal, dilated outline; followup consultation was no surgical confir- of patients areas 1. fluid (1 ) 60 of contour; pancreatic pancreatitis or neoplasm, but for this report these patients were given one designation based on the information available prior to CT examination. Thus, there were three groups patients: combi- irregularity manifested by irregular focal (3) Chronic pancreatitis-calcifi- after discharge and the referring physician. with Patients other or con- attenuation, of Diagnosis All patients patients size pancreatitis-some gland, pancreatitis-one illustrated in the of reduced and extrapancreatic Methods examinations or (4) complicated collection acute of the in pancreatic pancreatic Materials Cl by S. S. S. or B. E. C.: of abnormality of the pancreas, Proof In 1 978 interpreted evidence tour fluid collections. and were (i ) normal-no using carried out with a Pfizer/AS&E 125 kV, 5 or 10 sec scan Pancreatitis time, Among the was 60 diagnosed patients in the by CT in 59 patients group in whom (table pancreatitis 1). AJR:1 34, June CT 1980 OF FLUID COLLECTIONS was the clinical diagnosis, 1 2 were found to have a normal pancreas, 20 had acute or chronic pancreatitis, and 28 had complicated pancreatitis. Seven other cases of pancreatitis were detected in the group of patients clinically suspected of pancreatic cancer. In the third group (344 patients), four patients (cases 2, 9, 1 1 and 28) in whom pancreatic disease was not a primary clinical consideration were found to have complicated pancreatitis. In these cases, the CT examination was directed to the retroperitoneum, liver, or abdomen because of the clinical history of possible abdominal mass (case 2), left pleural effusion/rule out subdiaphragmatic abscess (case 9), back pain and fever (case 1 1 ), and defect in liver on radionuclide scan (case 28). Five patients with carcinoma of the pancreas also had evidence of pancreatitis; these cases were not included in this study. The 32 cases with complicated pancreatitis were analyzed in greater detail (table 2). These 32 cases included: (1) acute pancreatitis, 23 patients: 7-i 5 days after onset, 10 30); 1 6-30 days patients (cases 1 4, 6, 1 0, 21 22, 25-27, after onset, seven patients (cases 2, 7, 9, 1 1 1 3, 1 5, 23); 1 -3 months after onset, four patients (cases 3, 8, 1 6, 1 7); date of onset unknown, two patients (cases 1 4, 28); (2) acute pancreatitis superimposed on chronic pancreatitis, seven patients: 7-15 days after onset, six patients (cases 18-20, 24, 29, 31); 40 days after onset, one patient (case 5); (3) chronic pancreatitis, two patients (cases 12, 32). , , , , Observations Pancreas There were 1 6 patients with ‘pancreatic fluid collections” among the group of 32 patients with complicated pancreatitis (table 2). The diagnosis of fluid collections confined to the pancreas was confirmed by surgical exploration in eight patients (cases 4-6, 8, 1 2, 1 7, 21 and 30). Surgery included partial pancreatectomy, cystenterostomy, or 95% pancreatectomy for cases with chronic pancreatitis. The fluid collections were in the head of the pancreas in 1 1 cases, the body in four, and the tail in seven. The fluid collections appear to be within the pancreas (figs. 2-4). At operation the larger lesions are usually not strictly intrapancreatic, but rather blisterlike collections protruding from the anterior surface of the gland covered only with a thin fibrous membrane. There is generally no pancreatic parenchyma anterior to a large so-called pancreatic pseudocyst. Figure 1 illustrates two small focal accumulations of pancreatic juice at the site of duct rupture. Such collections were recognized in only two patients in this study. We attempted to quantify the severity of inflammatory involvement of the pancreas on the basis of CT features (table 2): 1 indicates mild edematous change; 2 indicates moderate pancreatic edema; and 3 indicates severe swelling of the gland with some areas of loss of pancreatic outline. Pancreatic necrosis was diagnosed (and confirmed at surgery) in three patients (cases 1 8, 20, and 21 ) in whom larger segments of the gland were devoid of recognizable pancreatic tissue on the CT scans. ‘ , ‘ ‘‘ WITH PANCREATITIS TABLE 1: PatIents with 1123 Pancreatitis Final Diagnosis Initial CT Category Suspected tis No. Patients Acute Pancre- Chronic Pancre- atitis atitis Acute and Chronic Pancreatitis Complicated Pancreatitis pancreati60 6 10 4 28 Suspected pancreatic neoplasm 135 3 2 2 0 Retroperitoneal, abdominal, liver 344 0 0 0 4 539 9 12 6 32 Total Lesser Sac Fluid collections in the omental bursa were detected by CT in 1 9 patients and confirmed by surgical exploration in seven (cases 3, 4, 6, 7, 1 2, 1 8, and 20). A cross-section of the trunk displaying peripancreatic anatomy is illustrated in figure 5. The lesser sac is located directly anterior to the pancreas and immediately posterior to the body of the stomach. In the CT scan of a normal individual, the lesser sac is a potential space, and the opacified stomach closely approximates the anterior surface of the pancreas. Lesser sac effusions are recognized as collections of water density that separate the stomach from the pancreas and are located anterior to the splenic flexure of the colon. A large effusion that displays the entire extent of the lesser sac is shown in figure 6. Fluid collections may become localized in various parts of the lesser sac. An additional example of filling of the superior recess of the lesser sac is in figure 7. The most common location for a localized fluid collection is in the lesser sac directly between the pancreas and the stomach; 1 5 patients had such pancreaticogastric collections (table 2). Anterior Pararenal Space The second most common site of pancreatic fluid collections was the anterior pararenal space. Anterior pararenal space effusion was diagnosed by CT in 1 5 patients and confirmed by surgical exploration in five (cases 5, 7, 1 8, 20, and 21 The anterior pararenal space is directly posterior to the lesser sac and is bounded posteriorly by the anterior layer of Gerota fascia (fig. 5) [5]. The anterior pararenal space contains the pancreas and the descending colon. A combination of five CT criteria were used to establish the diagnosis of an anterior pararenal fluid collection: (1 ) fluid collections posterior to the pancreas; (2) blurring of the lateral margin of the pancreas; (3) fluid collections posterior to the descending limb of the splenic flexure or descending colon; (4) splenorenal interface obliterated; and (5) thickening of the anterior layer of Gerota fascia. Typical anterior pararenal space collections are shown in figures 8 and 9. Multicompartmental fluid collections are the rule, and 1 1 of 1 5 patients with fluid in the anterior pararenal space also had lesser sac effusions (fig. 1 0). Anterior pararenal space collections are much more frequent on the left ). SIEGELMAN 1124 2: FluId Collections TABLE In Complicated Case Ornental of Fluid 1 Body Tail Cavity + . 2 3 AJR:134, Pancreatico- Superior Anterior pararenal space gastric cess + + re Posterior pararenal space + Liver + + 4 + + + .. 5 + 4- 6 . + + 7 + 8 + + + + + + + + + + 9 10 11 12 13 14 15 16 17 18 + Abscess + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + 20 21 Severity Pancreatitis 2 1 1 2 Calcified 2 3 2 2 2 2 2 1 + 22 + of Other 1980 1 1 1 Necrosis 1 Necrosis Necrosis 2 Findings .#{149}. Intrasplenic Mediastinal collection fluid #{149}.#{149} Juxtasplenic collection ..#{149} .#{149}#{149} #{149}#{149}#{149} Juxtasplenic collection .#{149}#{149} Along psoas into pelvis ... .#{149}#{149} 2 + + 19 June Collection Bursa No. Head AL. Pancreatitis Location Pancreas ET #{149}.. ... ... ..#{149} ... ..#{149} ... Intrasplenic collection Ascites, intrasplenic collection 23 + 24 + + 25.. 26 27 28 29 + + + + + + + + + . + 30 31 + 32 + + + 11 4 7 + Total Note-Data . 1 = mild on 25 men and seven edematous change: 2 side. In only one primarily involved. Posterior Pararenal - instance + + + 1 Calcified 3 2 2 2 1 1 Calcified + 2 19 15 1 years. women aged 26-7 moderate pancreatic edema: (case 1 8) was 8 3 the - severe right 6 15 swelling side Space Fluid collections in the posterior pararenal space were detected in six cases, all of whom also had anterior pararenal space involvement (fig. 1 1 In three patients (cases 5, 7, and 1 8) the effusions were confirmed surgically. The pararenal spaces are in communication inferior to the kidneys. It is presumed that fluid spreads from the anterior pararenal space to the posterior pararenal space. ). Liver Fluid collections with an intimate relation to the left lobe of the liver were found in five patients. All cases were confirmed by surgical exploration (cases 2, 8, and 22) or aspiration (cases 1 4 and 28). In two cases we believe that intrahepatic fluid collections were documented. In the first patient, a 55-year-old man with carcinoma of the larynx of gland with some area ... ... ... .#{149}. ... ..#{149} ... ..#{149} Juxtasplenic collection ..#{149} 5 loss of pancreatic outline. (case 1 4), a technetium sulfur colloid liver scan showed a solitary photon-deficient area in the left lobe of the liver entirely surrounded by liver parenchyma and interpreted as a probable metatasis. CT (fig. 1 2) showed evidence of pancreatitis with fluid collections in the tail of the pancreas and the lesser sac in addition to a water-density collection in the left lobe of the liver. The liver lesion was aspirated under sonographic control and the amylase content was 5,000 Somogyi units/dI. In the second patient (case 28), a similar collection in the left lobe of the liver was shown (fig. 1 3). Sonography also indicated that the lesion was intrahepatic. Aspiration of the lesion yielded a collection of turbid fluid with an amylase content of 2,500 Somogyi units/di. Both of these patients had follow-up sonography 3 weeks after aspiration, and the intrahepatic fluid collections were not seen. No surgical confirmation is available to document that the lesions in figures 1 2 and 1 3 were actually intrahepatic. In two other patients (cases 2 and 1 8), fluid collections were noted in direct contact with the posterolateral surface of the left lobe of the liver (fig. 1 4). A fifth patient with pancreatic ascites AJR:134, June CT 1980 OF FLUID COLLECTIONS Fig. 2.-Fluid collection, body of pancreas. Case 8: 50-year-old man with persistent abdominal pain after cholecystectomy. Water-density 5 cm mass body of pancreas. Cystenterostomy was performed. WITH Fig. 4.-Fluid collections of head, body, and tail of pancreas. Case 12: 51 -year-old man with long history of recurrent pancreatitis. Thin-walled 3 cm extrapancreatic fluid collection (arrows) in pancreaticogastric part of lesser sac. Pancreatectomy (95%) was performed. Fig. space. space. Fig. 3.-Fluid collection, tail of pancreas. Case 16: 29-year-old man with abdominal pain 3 months after attack of acute pancreatitis. Tail of pancreas is expanded by 4.5 cm water-density mass. Thin-walled 2.5 cm extrapancreatic fluid collection (arrows) in pancreaticogastric part of lesser sac. No surgery. (case liver, anterior to the left lobe of the to the ascites. 22) had fluid loculated probably secondary Spleen The spleen forms the lateral boundary of the anterior pararenal space. A loculation of fluid adjacent to the splenic hilus is not an unusual component of anterior pararenal space effusions. Distinct juxtasplenic fluid collections were seen in three patients (cases 5, 9, and 31). Three other 1125 PANCREATITIS 5.-Lesser Pancreas sac, anterior pararenal space, and posterior and splenic flexure of colon are within anterior patients (cases 2, 21, and 22) had actual intrasplenic accumulations (all verified by surgery) (fig. 14). pararenal pararenal fluid Mediastinum In an unusual case pancreatic beneath the diaphragmatic (fig. 15). crura superiorly the mediastinum fluid dissected to enter Retroperitoneum CT scanning directed at the retroperitoneal area was performed on a 30-year-old man with fever and backache. The examination showed fluid collections in the retroperi- 1126 SIEGELMAN El AL. AJR:134, Fig. 6.-Lesser sac effusion. CT 1 week after episode of acute pancreatitis in case 29, 40-year-old male 7 years. No surgery. A. Water-density fluid collection in superior recess of lesser sac which is indenting Extremely delicate margin of fluid collection: no fibrous wall has formed. C, Scan 4.5 cm below B. Pancreas anterior pararenal space. 0, Scan 7.5 cm below C. Inferior recess of lesser sac distended with water-density toneal space. When the examination proceeded to the upper abdomen, evidence was also found of pancreatitis with fluid collections in the anterior and posterior pararenal spaces (fig. 16). alcoholic with recurrent contrast-filled shows only fluid. attacks June 1980 of pancreatitis for stomach. B, Scan 3 cm below mild edematous change; no fluid of pseudocyst exists; four typical definitions are: (1 ) ‘collections of necrotic tissue, old blood, and secretions that have escaped from the pancreas damaged by pancreatitis.” of pancreatic juice, old blood, partially [6]; (2) ‘a collection digested tissue, fat, and occasionally sequestered bits of pancreatic tissue which collect as a consequence of inflam[7]; (3) ‘collections of panmation and duct disruption. creatic juice confined by capsules of fibrous and granulation tissue which do not have an epithelial lining. [8]; and (4) ‘ ‘ Discussion ‘ ‘ Semantics ‘ ‘ ‘ Fluid collection and effusion have been used as descriptive terms in this paper because we believe that pseudocyst is not always an appropriate designation for an extrapancreatic fluid collection. Unfortunately, no precise definition A. in “an accumulation space duct.” of pancreatic as a result of necrosis [9]. Use of the term pseudocyst juice and in the rupture is appropriate retroperitoneal of a pancreatic for describing June AJR:134, CT 1980 OF FLUID COLLECTIONS WITH 1127 PANCREATITIS propriate for the following reasons: (1 most acute extrapancreatic fluid collections distend an already existing anatomic space; (2) the filling of an anatomic space is very much analogous to filling of the pleural space with fluids, yet it would be inappropriate to call a pleural effusion a pseudocyst; (3) most collections in the anterior pararenal space are not cystlike; and (4) the term pseudocyst implies a certain permanence which may be misleading. Bradley et al. [1 0] also commented on the ambiguity created by the use of the all-encompassing term pseudocyst. They chose to distinguish acute pseudocyst (for which structures that are cystlike but are not true epithelium-lined cysts. In this sense, pseudocyst could be an acceptable term for an extrapancreatic accumulation of fluid that has become fixed by a dense fibrous capsule. The use of pseudocyst for an acute extrapancreatic fluid collection is nap- ) ‘ we - prefer the designation fluid collection) from chronic pseudocyst. #{149} .. - ‘- -. - Incidence #{149} . . ‘5 .,‘“ .‘.- #{149} .p. . ..- Fig. 7.-Superior recess of lesser sac. Case 6: 62-year-old cm water-density collection in superior recess of the lesser pancreatitis was induced by medication for malignant lymphoma. lection was surgically drained. A man with 4 sac. Acute Fluid col- of Fluid Collections An appreciable incidence of complicated pancreatitis was found in our study. Among 59 patients with pancreatitis, 32 cases (54%) were classified as complicated pancreatitis; this included 16 (27%) with pancreatic fluid collections and 25 (42%) with extrapancreatic fluid collections. The percentages are high when compared with the 2% estimated incidence of pseudocyst offered by Rosenberg et al. [1 1] and the 3% incidence following acute pancreatitis cited by Trapnell [1 2]. The discrepancy is understandable when one considers that Cl was not performed on all patients with acute pancreatitis during the study period. Patients with milder disease were often managed without CT; those with more severe and more persistent disease were much more apt to be examined with Cl. Fluid collections are much more likely to occur in patients with more severe disease. In a review of 44 patients with acute pancreatitis associated with B Fig. 8.-Fluid collection in left anterior pararenal space. Case 26: 39-year-old man with abdominal pain, temperature of 38.9#{176}C,nausea, and vomiting after onset of attack of acute pancreatitis. No surgery. A, Thickening of anterior layer of Gerota fascia (arrowheads). Fluid collection is posterior to splenic flexure (arrow). B, Scan at slightly higher level. Typical appearance of effusion in left anterior pararenal space. Fluid collection is not cystlike; pseudocyst would be poor descriptive term. 1128 SIEGELMAN Fig. 9.-Anterior pararenal space effusion. Case 10: 26-year-old man with surgery. A, Thickening of anterior layer of Gerota fascia on left side (arrowheads). fluid collection in anterior pararenal space between kidney and spleen. Fig. 1 O.-Multicompartmental fluid collections. Case 1 : 53-year-old man with abdominal pain, palpable abdominal mass, and hypocalcemia. Fluid collections in lesser sac and anterior pararenal space. Gas-filled stomach displaced anteriorly by lesser sac collection. Edematous pancreas visible by virtue of peripancreatic fat. No surgery. more than 6 days of amylase elevation, pancreatic pseudocysts were found in 24 patients (55%) [13]. Better monitoring of patients with CT and sonography will undoubtedly raise our estimate of the incidence of intrapancreatic and peripancreatic fluid collections during acute pancreatitis. Bradley et al. [10] noted fluid collections in the lesser sac in El AL. history of alcoholism hospitalized with abdominal This is clue to pancreatitis. B, Scan at higher Fig. woman 1 1 -Collection with June AJR:134, fever in posterior and abdominal pain, nausea and vomiting. level. Edematous pancreas pararenal pain 1980 after space. Case attack of viral 7: No and 71-year-old pancreatitis. Enlarged pancreas with irregular outline. Posterior pararenal space effusion (arrows). (Nasogastric tube in stomach.) Posterior pararenal space was surgically drained. 52 (56%) of 92 patients with moderately severe acute pancreatitis. Pathophysiology In acute pancreatic of Extrapancreatic Fluid Accumulations pancreatitis, the gland swells and drainage juice via the normal route is compromised of by AJR:134, June CT 1980 Fig. 1 2.-Intrahepatic in region sonographic control, fluid collection Fig. filling lesser of body in left lobe sac. Lesion, amylase fluid of liver. aspirated FLUID COLLECTIONS WITH Case 1 4: 55-year-old man with filling defect in liver (cursor). B, Scan at higher level. Water-density 4.5 concentration of 5,000 Somogyi units/dI. of pancreas yielded 1 3.-Intrahepatic defect collection. OF collection. Also under fluid Case collections sonographic 28: 35-year-old in head control, man of pancreas with and was rich in amylase. compression of the duct system. In severe cases, an intrapancreatic rupture of the duct system occurs with leakage of pancreatic juice into the interstitium of the gland [14]. Initially fluid accumulates within the gland at the site of duct rupture. It is possible to demonstrate duct disruption by means of endoscopic retrograde pancreatography [1 5]. In most patients the absence of a confining capsule leads to escape of pancreatic juice into the surrounding tissues. Although spontaneous escape of juice leads to many undesirable consequences, we would speculate that the drainage of pancreatic fluid may be beneficial by decompressing the inflamed pancreas. In many of our cases with large extrapancreatic fluid collections, the pancreas appeared Fig. 1129 PANCREATITIS noted on radionuclide cm fluid collection 14.-Intrasplenic fluid scan, confirmed in left lobe of liver. collection. Case by sonography. Lesion, 2: A, Fluid aspirated 47-year-old man under with abdominal pain. Enlarged spleen contains irregular low density filling defect. Fluid collection adjacent to left lobe of liver. At surgery, intrasplenic dissection of pancreatic fluid ent to inferior surface collection was documented, as was fluid collection adher- of left lobe of liver. only minimally abnormal. Notable examples of the phenomenon of the apparently spared pancreas are case 2 (fig. 13) and case 29 (fig. 5). Extrapancreatic fluid collections may retain a communication with a pancreatic duct system; an equilibrium may be established with the volume of secretions produced in the pancreas achieving a balance with secretions being continuously absorbed from the collection [1]. The high incidence of persistent pancreaticocutaneous fistula after simple external drainage of extrapancreatic fluid collections is strong indirect evidence for a continued communication with the pancreatic duct system. However, in some patients with decrease in the rate of pancreatic secre- 1130 Fig. SIEGELMAN 1 5.-Mediastinal fluid collection. Case 3: 60-year-old male chronic El alcoholic AL. with AJR:134, abdominal pain and dysphagia. gastrointestinal series showed mass in lower thorax. A, Water-density fluid collection surrounds aorta and distends crura collection was contiguous with fluid in lesser sac. B, At higher level. Fluid collection seen posterior to heart and anterior operation, drainage was moderate initially but gradually decreased over a 3 month period. tion, subsidence of pancreatic edema, and recovery of proper drainage of the duct system, the centrifugal drainage of pancreatic juice may cease. In such cases, extrapancreatic fluid collections should be reabsorbed or, if drained, should not recur. Location The pancreatic secretions contain proteolytic enzymes that facilitate a dissection of the mass of fluid along established tissue planes. Figure 5 is the key to understanding the direction of fluid escape. The anterior pararenal space is filled first if fluid leaks from the posterior part of the gland or from the tail. Anterior perforation of the posterior layer of the parietal peritoneum leads to direct extension of fluid into the lesser sac. Fluid escaping posterolaterally may easily course along the splenic vessels via the hilum of the spleen into the splenic parenchyma [1 6]. Fluid dissecting superiorly and posteriorly may pass between the crura of the diaphragm (as in one case) to enter the mediastinum. The extension of pancreatic secretions into the mediastinum is uncommon but well recognized [1 7]. The body of the pancreas can be very close to the left lobe of the liver, particularly in a thin patient with hepatic enlargement (fig. 5). Fluid in the lesser sac may easily protrude into the space between the stomach and the left lobe of the liver by distending the hepatogastric ligament. We speculate that fluid that initially enters the lesser sac may also proceed between the leaves of the hepatogastric ligament to enter the liver. Pancreatic secretions that follow such a pathway would enter the liver in the left lobe (figs. 12 Chest of diaphragm. to descending radiography June and 1980 upper At inferior level, fluid thoracic aorta. After and 1 3). We predict that intrahepatic fluid collections will be recognized with greater frequency with sonography and computed tomography, and that eventually they may prove to be more common than mediastinal collections. Pancreatic juice in the lesser sac usually does not enter the peritoneal cavity; occasionally (case 22) fluid enters the peritoneum to produce pancreatic ascites either via the foramen of Winslow or by rupturing the parietal peritoneum. CT in Detection of Fluid Collections On the basis of our experience, we conclude that CT will be useful in evaluating patients with pancreatitis. The recognition of acute pancreatitis is made without difficulty by history, physical examination, and serum amylase determinations. However, proper management is not simple, and the information provided by CT on the existence and distribution of pancreatic and peripancreatic fluid collections could be helpful. The current capacities of Cl are as follows: The mass lesion. At a variable period after the onset of acute pancreatitis, a patient may develop an apparent mass in the pancreatic region by physical examination or barium studies. Often such patients have been assumed to have pancreatic pseudocysts and have been subjected to untimely surgical exploration [1 8]. CT can distinguish conditions responsible for such masses: (1 ) phlegmon-a diffusely enlarged edematous pancreas with induration of the peripancreatic tissues; Warshaw [6] suggested the term phlegmon to distinguish the swollen pancreas from other potential pancreatic masses; (2) pancreatic fluid collections; (3) extrapancreatic fluid collections-fluid collections in the I :‘- . I Fig. 1 6.-Retroperitoneal fluid collection. Case 11: 30-year-old man with pain in back and left hip associated with nausea, vomiting, and low grade fever. No surgery. A, Level of iliac crest. Retroperitoneal fluid collection anterolateral to left psoas muscle. B, Level of L4. Fluid collection is loculated. C. Scan 4 cm above B. Lower pole of left kidney and pararenal fat (which appears black) surrounded by fluid collections in anterior pararenal space and posterior pararenal space. D, Scan 5 cm above C. Body and tail of pancreas are slightly enlarged. Fluid in anterior pararenal space. anterior pararenal nite mass effect; space or lesser sac may produce a defior some combination of those three. Prolongation of symptoms. Patients may have some combination of persistent abdominal pain, low grade fever, and leukocytosis at a variable period after an attack of acute pancreatitis with no palpable mass. As in the cases illustrated, fluid collections, even in unusual locations, have a distinctive appearance on CT scan. In our experience fluid collections in the lesser sac, anterior pararenal space, or retroperitoneum are often accompanied by pain, leukocytosis, and low grade fever. The appearance of the pancreas may have returned to normal but the fluid collection establishes that pancreatitis persists. Concern for abscess. The patient under observation 2-3 weeks after an attack of acute pancreatitis may manifest gradual progressive rise in temperature over several days. The concern is for pancreatic abscess, which frequently develops insidiously. The treatment is to remove any ne- crotic pancreatic tissue and drain the area of focal infection. However, even at laparotomy the diagnosis and location of abscess may be difficult [2]. CT may be used to survey the likeliest sites of pancreatic abscess: the pancreas, the lesser sac, and the pararenal spaces. Detection of a fine dispersion of gas bubbles can solve the problem of localization, but in our experience most abscesses have appeared as simple fluid collections (fig. 1 7). Management of Fluid Collections Proper management of the patient with acute pancreatitis remains a formidable challenge because it is an unpredictable illness with an appreciable incidence of severe complications and death. All would agree that uncomplicated pancreatitis is best treated nonoperatively. Since the mortality of untreated pancreatic abscess approaches 100%, even conservative physicians must agree that operation is necessary for pancreatic necrosis and abscess. Key manage- 1132 SIEGELMAN El AL. cations week AJR: 134, June 1980 that require period surgical of watchful drainage, waiting but the intended appears 6 to be a prudent plan of management. However, the policy of watchful waiting has not gained universal acceptance [20]. After greater experience with serial CT for patients with pancreatic accumulations, it may be possible to develop criteria for determining which fluid collections are more likely to be absorbed and which patients are more prone to development of abscess. We are attempting to develop guidelines for the management of complicated pancreatitis based on serial Cl examination. REFERENCES 1 . 2. Anderson MC. : 434-449 Trapnell J. The natural pancreatitis. Fig. 1 7.-Abscess. pancreas; patient anterior pararenal drained numerous of fluid Case 5: 33-year-old woman. Extensively calcified containing inflammatory high amylase, necrotic debris, old blood, and cells. ment questions revolve around the indications for surgery and the timing of operative intervention on patients with intrapancreatic and extrapancreatic fluid collections. Some surgical groups advocate operative intervention as soon as a fluid collection is detected [7, 8]. Two arguments are usually cited: (1 ) risk of abscess-pancreatic juice admixed with blood and bits of necrotic tissue is an ideal site for bacterial proliferation; (2) catastrophic complications-the patient with a fluid collection is at risk for a series of potentially life-threatening complications, including free rupture into the peritoneal cavity and erosion of a major vessel producing massive gastrointestinal hemorrhage. Those who advocate an attitude of watchful waiting for patients with acute fluid collections cite other arguments: (1 ) spontaneous resolution-peripancreatic fluid collections may be totally reabsorbed; (2) fistula formation-patients with simple drainage of fluid collections frequently develop a persistent pancreatic fistula. Any scheme for managing fluid collections should consider the possibility of spontaneous resolution, deal with the risk of abscess, minimize the chances of fistula formation, and attempt to avoid catastrophic complications. Bradley et al. [1 9] recently reported experience in monitoring 54 patients with pancreatic or peripancreatic fluid collections demonstrated by sonography. Of the 54 fluid collections, 24 (44%) resolved spontaneously within 6 weeks. Beyond 6 weeks the incidence precipitously. be monitored 3. Jacobs of further spontaneous resolution ML, of pancreatic history Daggett WM, Surgery and management 1 972;1 Gastroentero/ of factors disease. Civetta JM, influencing of acute :147-166 et al. Acute survival. Ann OF, et al. pancreatitis: 1977;i85: Surg 43-51 4. Hessel SJ, Siegelman 55, Adams ysis of Computed tomography pancreas. Presented at the 5. Society of North Meyers MA, 1972;1 6. 7. effusions: AL. Surg Baker of the November K, Berne anal- the Radiological 1979 A. Radiologic an anatomic Inflammatory C/in RJ. North 8. Atlanta, JP, Peelle Prospective in evaluating ultrasound meeting features approach. Radiology 04:249-257 Warshaw tis. and annual America, Whalen of extraperitoneal North Acute masses following 1974;54:62i Am surgical acute pancreati- -636 diseases of the pancreas. Surg C/in 1972;52:239-256 Am Thomford NA, review of fifty 9. Dorland’s Jesseph cases. JE. Am illustrated 1974 Saunders, Pseudocyst of the pancreas: a 1 969; 1 1 8 : 86-94 dictionary, 25th ed. Philadelphia, J Surg medical Bradley EL Ill, Gonzalez AC, Clements JL Jr. Acute pancreatic pseudocysts: incidence and implications. Ann Surg 1976;1 84: 1 0. 734-737 11 1 2. . Rosenberg pancreatic Trapnell Acta 1 4. 1K, Kahn JA, Walt AJ. Surgical pseudocysts. Am J Surg 1969;i J. creatitis. 1 3. Ebbesen 1 5. 5, WaIt BN, and complications AL, 5, with of acute pan- 49:361-372 amylase and elevation. Nielsen scanning. SAD, Ann TM, Evans by pancreatic unnatural I 975;62 by endoscopic Chesney dissection natural Br J Surg Cyst Schmidt A. The retrograde Surg GW, history of :37-44 diag- pancreatog- 1 977;i 85 : 286-289 McCarthy HF. Intra- pseudocysts. N EngI J Med : 72-75 Kirchner SG, Heller the mediastinum. Shafer The Hancke ultrasonic Warshaw 1 972:287 1 8. AJ. pseudocysts. of pancreatic splenic 1 7. the EngI 1 971 KE, Sch#{228}nebeckJ. Prolonged 1967;i33:6i-65 Anderson raphy 16. of experience 1 7 : 1 1-17 ChirScand Sankaran nosis Management Ann R Co/I Surg pancreatic fell Bradley et al. [1 9] now propose that patients for 6 week periods to determine if surgery is necessary. As they indicate, there is an added benefit to temporary watchful waiting in that the fluid collections that are not absorbed tend to develop a dense fibrous capsule. With a dense capsule, a cyst-enterostomy rather than a simple cyst drainage may be performed, reducing the incidence of fistula formation. Some patients awaiting absorption or maturation of fluid collections will develop compli- C/in analysis has chronic pancreatitis. Loculated fluid collection in left space compresses spleen and left kidney. Abscess was Review 1969;66 RB, Silvis AM, Radiology SE. Smith CW. 1 977;i Pancreatic Pancreatic pseudocyst of 23 : 37-42 pseudo-pseudocysts. Am J Surg 1 974; 1 27 : 320-325 1 9. Bradley EL Ill, Clements history of pancreatic agement. Am J Surg JL 20. Pollak EW, Michas CA, Wolfman management 201 in fifty-four Jr, Gonzalez pseudocysts: a unified 1979;i 37:135-141 patients. AC. EF Jr. Pancreatic Am J Surg The concept natural of man- pseudocyst: 1 978;i 35:199-