Clinical Radiology (1980) 31, 87-93 0009 9260/80/01460087502.00 © 1980 Royal College of Radiologists

The Plain Abdominal Radiograph in Acute Pancreatitis sTANLEY DAVIS, SANTILAL P. PARBHOO and MICHAEL J. GIBSON*

Department of Radiology and Academic Department of Surgery, Royal Free Hospital, London, and Department of Radiology, Frenchay Hospital, Bristol

The radiographs o f 100 patients with acute pancreatitis were reviewed and compared with 100 controls by two radiologists and a surgeon. Our aim was to assess the frequency and usefulness of the signs described in the literature. Calcification of the pancreas was seen in one case only. Abnormalities of the biliary tree (visible gallbaldder, biliary gas and gallstones) were seen in 10%. The left psoas shadow was more frequently absent in the pancreatitis series. Paucity o f gastrointestinal gas although observed in 12 cases was ascribed to vomiting. A more important sign was the gaseous outline of an adynamic duodenal loop which was seen in half o f the patients examined in the left lateral decubitus position. Dilated jejunum was seen in 31 cases, associated with sentinel loops in 10 and multiple fluid levels in 25 patients. Dilatation of the transverse colon was the most constant colonic sign (18%), but the colon 'cut-off ' sign was not seen. It was concluded that the most promi- nent signs in order of importance are a gaseous distension of the duodenal loop, gas in the duodenal cap, a dilated transverse colon and the sentinel loop. The gasless abdomen is a striking but rare sign and in our series was always associated with severe pancreatitis.

There have been a number of previous reviews on the radiological changes in acute pancreatitis, some in- volving a large number of cases but virtually none systematically assessing each radiograph for the signs described in the literature. Most of these, however, have been undertaken in North America where it is known that, in general, the disease has a different aetiology to that in this country. In the United Kingdom acute pancreatitis is most commonly a sequel to biliary lithiasis, whereas in the United States of America, alcoholism plays a prominent role. A large number of radiological signs have been described and the purpose of this study was to deter- mine the frequency of these Findings on the plain films of the abdomen. Assurance was also sought that the plain radiograph was in fact of assistance in recognising the condition, as well as being a means of excluding other causes o f the acute abdomen.

METHODS

The plain abdominal radiographs and the records of 100 cases o f acute pancreatitis, as defined by the Marseilles Symposium (Sarles, 1963) were reviewed. The diagnosis was based on the clinical presentation of the acute abdomen, associated with a significantly raised serum amylase (> 1000 i.u./litre/> 1000

*Current address: Sir Charles Gairdner Hospital, Nedlands, Western Australia 6009.

Reprint requests to S_P.P., Academic Department of Surgery, Royal Free Hospital, Pond Street, London NW3 2QG.

Somogyi units), the findings at laparotomy or at post mortem. The sex, age and aetiology and basis o f diag- nosis of pancreatitis in our patients are shown in Table 1. There were 10 deaths in the series, six patients had biliary tract disease (average age 77 years), three had alcoholic pancreatitis (average age 51) and one patient ruptured his aortic aneurysm following bouts o f acute pancreatitis. In every case a supine Film was available, in 67 an erect film and in 24 a lateral decubitus film with the right side raised. These films were taken on the day of, or within.24 h of, admission, i.e. during the acute presentation of the illness. Since some of the signs attributed to acute pancreatitis may also be seen in the 'normal ' abdomen, the above series was compared with a simi- lar number of examinations in which pancreatitis was not the cause of the patient's symptoms. For this purpose, use was made of the preliminary films of 100 intravenous pyelograms.

It is appreciated that these controls are not alto- gether satisfactory, since the patients obviously had some symptoms, and would also have had bowel preparation. Another disadvantage was the absence of an erect or decubitus film. A list of the radio- logical signs in the literature was made and to this was added other signs which previous experience had suggested might be of value, giving a total of 35 possible signs (Table 2). All the films were examined by the authors, and the radiological signs were accepted only if there was complete agreement. A large number of signs have been described in the literature, and many of these are self-evident. There is however variation in the literature, with regard to

88 CLINICAL RADIOLOGY

Table 1 - (a) Clinical details. (b) Aetiology of pancreatitis. (c) Basis for Diagnosis

No. Sex Age range Average age Mortalio'

(a) 57 M 19-83 50.4 4 43 F 17-95 59.4 6

(b) Aetiology of panereatitis Biliary tract disease 54 Alcohol 26 Trauma 1 Familial pancreatitis 1 Hyperlipidaemia 3 Contraceptive pill 2 Viral infections 3 Post-operative 1 Unknown 19

(c)

(Two factors, e.g. alcohol and biliary tract disease, contraceptive pill and hyper- lipidaemia were associated in 10 patients.)

Basis for diagnosis Clinical features and raised serum amylase 87 Clinical feaures and raised urinary amylase 2 Operative findings 9 Post-mortem findings 2

certain o f these signs and some clarif icat ion o f these is required.

Sentinel Loop

This te rm was first used by Levitin (1946) who described an isolated, dilated loop o f adynamic bowel visible on the supine film. It was accepted in our series only i f the dilated loop also showed fluid levels

on the erect or decubi tus film (Fig. 1), thereby excluding its diagnosis on the supine series and con t ro l films. Small bowel o f greater than 3 crn diameter was considered to be dilated.

Colon Cut Off Sign

Different versions o f this sign are to be found_ The t e rm was first used by Price ( 1 9 5 6 ) t o indicate gaseous

Fig. 1 - Sentinel loop on erect film. Fig. 2 - Dilated colon.

THE PLAIN ABDOMINAL RADIOGRAPH IN ACUTE PANCREATITIS 89

Table 2 - List of radiological signs

A. Directly related to the Pancreas 1. Enlarged pancreas 2. Gastrocolic separation 3, Gas within the pancreas 4. Calcification in the pancreas 5. Mottling from fat necrosis

The colon varies considerably in calibre under normal circumstances and a precise assessment of calibre is not possible. For the purposes of this study a colon with a diameter of greater than 6 cm was regarded as dilated (Fig. 2).

13.

C.

Gas troin testinal.sign s Paucity of gas Displacement of the stomach Dilated stomach Gas in the duodenal cap Gas in the duodenal loop Dilated duodenal loop

Indentation of duodenum by the gallbladder Gas in the jejunum or ileum Dilated jejunum Sentinel loop

More than three small bowel fluid levels Gas in the hepatic flexure Gas in splenic flexure Dilated hepatic flexure Dilated splenic flexure 'Colon cut off' sign Dilated ascending colon

Dilated transverse colon

Dilated descending colon Indentation of hepatic flexure by gallbladder Gas in the caecum and terminal ileum

Other changes 1. Loss of psoas shadows 2_ Loss of renal outline 3. Elevated diaphragm 4. Gallstones (opaque) 5. Absent preperitoneal fat line 6. Gas in the biliary tract 7. Ascites 8. Gas/fluid levels outside the bowel

Fat Necrosis

Baylin and Weeks in 1944 described areas of faint mottling and increased density representing fat necrosis and saponification. This sign has been con- sidered as pathognomorLic for severe pancreatitis by Berenson e t al. (1971). It is reputed to be best shown on a film taken with a low kilovoltage. The condition may be associated with a precipitous drop in serum calcium and metastatic fat necrosis, and is associated with a high mortality.

Pancreatic Enlargement

A soft tissue shadow in the upper abdomen repre- senting the swollen pancreas has been described but is rare. When there is gas in the stomach and transverse colon this becomes more apparent. This has also been referred to as the 'trumpet sign' (Benson, 1974) in which a wedge-shaped shadow is seen separating stomach and transverse colon.

RESULTS

These are shown in Tables 3-5_

Table 3 - Incidence of extra gastrointestinal tract signs

Control Pancreatitis

distension of the ascending colon and hepatic flexure with sharp limitation of the gas shadow just beyond the flexure. In the same year Stuart described the transverse colon 'cut off' sign as gas-filled hepatic and splenic flexures which appeared to be cut off from the central transverse colon segment. A third version of the 'cut off' sign was reported by Brascho et al. (1962) in which the cut off occurred at the splenic flexure. These descriptions were preceded by that of Baylin and Weeks (1944), who described an area of 'spasm' occurring either in the transverse colon or the splenic flexure. Because of this confusion we specifically noted the gas distribution in the colon and the presence or absence of dilatation was recorded.

Supine Erec t / decubitus

Enlarged pancreas 0 0 1 Pancreatic calcification 0 2 1 Opaque gallstones 1 5 1 Elevated left diaphragm 0 3 0 Elevated right diaphragm 0 0 0 Absent left psoas shadow 6 17 4 Absent right psoas shadow 14 23 5 Absent preperitoneal ratline 2 2 0 Visible gallbladder 0 2 2 Gas in biliary tree 0 3 0 Ascites 0 0 2 Gas within pancreas 0 0 0 Mottling from fat necrosis 0 0 0 Localised gas fluid levels 0 1 1

outside bowel

90 C L I N I C A L R A D I O L O G Y

Table 4 - Incidence of upper gastrointestinal tract signs

Control Pancreatitis

Supine Erect/ decubitus

Paucity of normal gas 7 14 7 shadows

Displacement of stomach 0 0 0 Dilated stomach 0 4 3 Gas-filled duodenal cap 7 26 16 Duodenal loop gas 2 8 14 Dilatation of duodenal loop 0 4 5 Indentation of duodenum 0 0 0

by gallbladder Gas in jejunum or ileum 79 75 36 Dilated jejunum 8 30 9 Sentinal loop 10 Over three bowel fluid - 25

levels

pancreatitis, and Sades et al. (1965) relate it to the intake of alcohol.

Pancreatic Enlargement

Pancreatic enlargement indenting the duodenal loop was seen in one patient only, which is in keeping with Benson's Fmdings. Other authors (Hulten, 1928; Goldman, 1931) place some value on this sign, Gastrocolic separation due to an enlarged pancreas is claimed to be a common sign. Ransom et al. (1974) reported that gastrocolic separation occurred in 15% of cases in their series, while in a recent paper Moren0 and Rivera (1976) claimed that the sign occurred in at least 49% of cases. Unfortunately that latter study is vitiated by the absence o f a control series despite the known marked variation in the posit ion of the gastric air bubble.

Table 5 - Incidence of colonic gas signs

Control Pancreatitis

Supine Erect/ decubitus

Gas in hepatic flexure 22 28 23 Gas in splenic flexure 20 33 26 Dilated hepatic flexure 0 1 0 Dilated splenic flexure 0 1 0 Colon 'cut off' sign 0 0 0 Dilated ascending colon 0 4 1 Dilated descending colon 0 0 0 Dilated transverse colon 2 18 3 Indentation of hepatic 0 1 0

flexure by gallbladder Caecal and terminal ileal gas 0 7 2

DISCUSSION

From the results it is shown that most o f the signs investigated are o f little or no value in the diagnosis of acute pancreatitis. A number of them were not seen in either the control series or in the 'pancreati t is ' series. Others showed a similar incidence in both series and are unhelpful. There were, however, a number of signs which were seen more commonly in the patients with pancreatitis and these, together with the signs most frequently emphasised in the l i terature, are discussed individually.

Pancreatic Calcification

Two patients showed pancreatic calcification. This low incidence is similar to that recorded by Cantwell and Pollock (1959), Ransom et al. (1974) and Benson (1974). There seems to be agreement that calcifi- ca t ion is a manifestation of recurrent or chronic

Psoas S h a d o w

Although Poppel and Bercow (1949) drew atten. t ion to a poorly defined left psoas shadow as being evidence of acute pancreatitis, other authors disagree (Stein et al., 1959; Cantwell and Pollock, 1959; Weens and Walker, 1964). In our series an absent psoas shadow was recorded more frequently in the pancreatitis series than in the control, particularly on the left side. However, the high incidence of this sign in the control group detracts from its value in the individual case.

Paucity o f Normal Gas Shadows

This was found twice as frequently as in the controls. We agree with Felson (1968) tha t vomiting plays a major part in the production o f this sign. All patients who showed paucity of gas on the plain film (Fig. 3) had severe pancreatitis and persistent vomiting as a prominent symptom.

Gas in the Duodenum

The amount of gas in the duodenum will depend on the intensity of the inf lammatory process (Poppet, 1968) and the posit ion of the patient. The presence0f a duodenal ileus allows gas to remain in the duo- denum and the high incidence of duodenal gas is in accordance with Findings reported in other series (Weens and Walker, 1964; Bathazar and Lutzker; 1976). Gas in the duodenal loop was seen in half the cases when the left lateral decubitus film projection was used. In four of these cases the duodenal lo0p was also dilated. On the erect film the gas tends to remain in the duodenal cap. This contrasts with only

T H E P L A I N A B D O M I N A L R A D I O G R A P H IN A C U T E P A N C R E A T I T I S 91

four of 62 cases in which gas was seen in the duo- denal loop in the erect film with no evidence of dila- tation (Fig. 4). Our Findings suggest that the left lateral decubitus projection is the most useful film for demonstrating an inflammatory lesion in the duo- denal loop. This sign is often missed in the supine fdrn (Fig. 5a, b). Since the decubitus projection can be carried out even in the ill patient, it should be included in any radiographic assessment of the acute abdomen-

Pancreatic Abscess

Although an uncommon sign, the presence of gas in the pancreatic substance is regarded as a patho- gnomonic sign of pancreatitis. Felson (1957)repor ted six cases, the pro_gnosis in these patients being very poor. Altemeier and Alexander (1963) found two cases in a series of 32 patients and agreed that the sign was pathognomonic. Stephens (1973) believes that this sign is rarely detected. It was not possible to identify mott led gas within the pancreas in any of our patients, but in one case there was a fluid level in the lesser sac due to abscess. This patient died 4 8 h after admission.

Gas in the Caecum and Terminal Ileum

The spread of inflammation can be widespread, and as pointed out by Meyer and Evans (1973) it may

extend to the caecal region. This then gives rise to an ileus with gaseous distension of the terminal ileum and caecum. It was seen in seven patients (Fig. 6).

Dilated Jejunum and Sentinel Loop

When Levitin (1946) described the 'sentinel loop ' he referred to the changes on a supine film only, and showed that the appearances could be differentiated from mechanical obstruction by taking serial films. Ransom e t al. (1974) found segmental small bowel dilatation in 40% of their cases, and Benson (1974) found it to be the most frequent plain film finding (34%). Stein e t al. (1959) found that 55% of their patients had loops of small bowel measuring over 3 cm in diameter. On the other hand, Weens and Walker (1964) and Stephens (1973) found an inci- dence of less than 10%. In this series a dilated loop of small bowel was seen on the supine film in 30% of the cases (compared with 8% of controls); in all but two of these, an erect or decubitus film was available but in only 10 of these were fluid levels demon- strated. It would seem that the incidence of 'sentinel loop ' in any of these particular series will depend on the way in which the term is defined. It is difficult to evaluate the significance of dilated bowel in the 20 patients who did not show fluid levels, especially as eight patients in the control series were shown to have a dilated small bowel loop. In the absence of

Fig. 3 - Paucity of normal gas shadows.

Fig. 4 - Gas-filled duodenal cap and faint outline of duo- denal loop (erect film).

92 C L I N I C A L R A D I O L O G Y

(a)

Fig. 5 - (a) Supine and left lateral deeubitus projections_ (b) Shows gas-filled duodenal loop not visible on erect film.

(b)

fluid levels or a further film to show persistence of dilatation, caution should be exercised in the inter. pretation of this sign.

Fig. 6 - Gas in t he t e r m i n a l i l eum a n d c a e c u m .

Colon 'Cut Off'

The presence of gas in the hepatic and splenic flexures occurred with similar frequency in the control and survey series. This casts doubt on the value of Stuart's version of the 'cut off' sign (Stuart, 1956). There was no example in this series of the colon 'cut off' sign as described by Price (1956) although dilatation of the ascending colon was seen in four patients. Cantwell and Pollock (1956) and Weens and Walker (1964) found the colon 'cut off" sign in 2% of patients. However in 18 patients, compared with two in the control group, there was dilatation of the transverse colon with relative absence of gas in the descending colon (Fig. 2). Brascho e t al. (1962) described similar appearances in his distal 'cut off' sign which he found in 50% of patients.

THE PLAIN A B D O M I N A L R A D I O G R A P H IN ACUTE PANCREATITIS 93

coNCLUSION The signs which are most likely to be present on

the plain abdominal radiograph in a patient with acute pancreatitis are a gas-filled duodenal loop with or without dilatation, absent (left)psoas shadow,, sentinel loop, dilated jejunum, dilated transverse colon, dilated ascending colon, gas in the terminal ileum and caecum. None of these signs is specific and may be seen in other conditions, e.g. dilatation of the duodenal loop is seen in acute cholecystitis. However, when these signs are present on a plain film examination of the abdomen (which must include a decubitus film with the right side raised) the possi- b~ity of acute pancreatitis should be remembered and the appropriate biochemical tests performed.

Acknowledgements. We thank the clinicians of the Royal Free Hospital and Frenchay Hospital, Bristol, for access to their clinical records and Dr P. M. Bretland oftheWhitt ington f[0spital for additional X-ray material.

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