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Journal de radiologie
Vol 80, N° 6  - mai 1999
p. 575
Doi : JR-06-1999-80-6-0221-0363-101019-ART6
CT FINDINGS IN ACUTE CHOLECYSTITIS: VALUE OF PERICHOLECYSTIC FAT STRANDING
 

ORIGINAL ARTICLE

Journal de radiologie1999; 80: 575
© Masson, Paris, 1999

N Aoun(1), , T Smayra(1), , S Haddad-Zebouni(1), , S Slaba(1), , M Ghossain(1), , N Atallah(1)

(1)Service de Radiodiagnostic, Hôtel-Dieu de France, Rue Adib Ishac, Beyrouth, Liban.

SUMMARY

Purpose

To assess the value of pericholecystic fat stranding at CT for diagnosis of acute cholecystitis, and to compare this sign to other CT findings in patients with acute cholecystitis.

Materials and methods

The CT examinations of 14 patients with proven acute cholecystitis were retrospectively reviewed to detect the presence of findings consistent with this diagnosis.

Results

The most common CT finding was stranding of the pericholecystic fat (13 patients), followed by gallbladder distention (11 patients). Pericholecystic or perihepatic fluid was present in 6 patients in association with severe acute cholecystitis (6 patients) and biliary peritonitis (2 patients).

Conclusion

Stranding of the pericholecystic fat was the most common CT finding in patients with acute cholecystitis, followed by gallbladder distention.

Key words : Computed tomography. , Gallbladder, diseases. , Cholecystitis.

RÉSUMÉ

Cholécystite aiguë en tomodensitométrie: utilité de la trabéculation de la graisse périvésiculaire

But

Notre but est d'étudier en tomodensitométrie la trabéculation de la graisse périvésiculaire dans la cholécystite aiguë et de la comparer aux autres signes tomodensitométriques.

Matériels et méthodes

Les examens tomodensitométriques de 14 patients ayant une cholécystite aiguë prouvée ont été revus, avec recherche des signes en faveur de ce diagnostic.

Résultats

Le signe tomodensitométrique le plus fréquemment retrouvé (13 patients) était la trabéculation de la graisse périvésiculaire, suivi de la distension de la vésicule biliaire (11 patients). Du liquide périvésiculaire ou périhépatique était présent chez 6 patients, associé à une cholécystite aiguë sévère (6 patients) et à une péritonite biliaire (2 patients).

Conclusion

La trabéculation de la graisse périvésiculaire était le signe tomodensitométrique le plus fréquent, suivi de la distension vésiculaire.

Mots clés : Tomodensitométrie. , Vésicule biliaire, maladies. , Cholécystite.


INTRODUCTION

CT often is performed in patients presenting with acute non-specific abdominal pain and may be the first imaging study to suggest the possibility of acute cholecystitis (AC). Results at US may be inconclusive and it may sometimes be difficult to differentiate between acute GB inflammation and tumor. In addition, the clinical presentation may be atypical or suggest the presence of an associated pathology. In all such cases, CT may be of value.

CT findings of AC have already been described [1, 2, 3, 4, 5, 6], but only few authors [1, 6] have considered the presence of stranding of the pericholecystic fat.

The purpose of the paper is to review the CT findings consistent with AC and to underscore the value of stranding of the pericholecystic fat.

MATERIALS AND METHODS

Fourteen patients with proven AC underwent CT evaluation between March 1993 and July 1997. AC was proven based on surgery (n=13) or bile aspiration and culture after cholecystostomy (n=1). There were 8 men and 6 women aged between 45 and 88 years. All data were retrospectively reviewed.

The indications for CT included: atypical presentation of AC, typical clinical presentation with normal or inconclusive US, another pathology was suspected.

All patients underwent US (Sonochrome, GE) within 24 hours of CT.

All CT examinations were obtained on a CE 12000 scanner (CGR). Contiguous 10 mm thick axial sections were obtained from the dome of the liver down to the iliac crests following administration of oral contrast and bolus administration of IV (30-45 cc) contrast. Five mm thick images at 8 mm increments were obtained through the GB fossa in 12 patients. The time interval between onset of symptoms and CT scanning was < 48 hours in 10 cases, and between 3-4 days in the remaining 4 cases. Surgery was performed within 24 hours from CT in 11 cases, and between 5-18 days post-CT in the remaining 3 cases.

The CT examinations were reviewed by a radiologist with expertise in abdominal imaging and a radiology resident. Consensus was obtained for the following findings: transverse GB diameter > 4 cm, longitudinal GB diameter > 8 cm, GB wall thickening > 4 mm (away from areas susceptible to partial volume effect), subserosal edema (thin hypodense line), gas in the GB lumen or wall, GB stones, pericholecystic or perihepatic fluid, and stranding of the pericholecystic fat.

Based on the degree of GB wall inflammation at histology, AC was classified as mild or severe. Severe AC was characterized by ulcerations, gangrene, or perforation with or without intra- or pericholecystic abscess or biliary peritonitis.

RESULTS

Results from this study are summarized in table I . AC was classified as severe in 8 cases: gangrene in 4 cases, 2 cases of biliary peritonitis, 1 cases of GB empyema, 1 case of GB perforation with pericholecystic abscess. AC was classified as mild in 5 cases. One patient was treated by cholecystostomy. Stones were noted at surgery in 8 cases. Six patients had acalculous AC.

GB stones were noted at CT in only 5 patients (fig. 1and2) . GB wall thickening was noted in 8 cases (fig. 2) , including 5 patients with stones and 3 with acalculous AC. The GB was distended in 11 cases (5 patients with stones and 6 patients with acalculous AC). GB wall edema was noted in 6 patients (fig. 1a) . No patient had gas in the GB wall or lumen. Stranding of the pericholecystic fat was present in all patients but one (fig. 1 , 2 , and 3) . Isolated pericholecystic or perihepatic fluid (without ascitis) was noted in 6 patients. Two of the se patients had biliary peritonitis, 3 had gangrenous AC, and 1 had perforated AC with pericholecystic abscess. Omental inflammation surrounding the GB was present in 5 cases at surgery. In 14 patients, a diagnosis of AC was prospectively made at CT based on stranding of the pericholecystic fat with or without other associated findings in 13 cases and based on other findings in 1 case table I .

US showed GB stones or other abnormalities in 11 cases (table II) . A diagnosis of AC was made at US in 6 cases based on the presence of GB wall thickening and GB distention. US was normal in 3 cases.

DISCUSSION

Acute cholecystitis often remains a clinical diagnosis confirmed at US or scintigraphy. CT probably is not needed when a diagnosis has already been confirmed. However, CT often is performed in patients with acute abdominal pain or non-specific abdominal pain, especially when results at US are inconclusive. The specificity of US varies between 82-100% with a sensitivity between 67-93% [3]. Hepatobiliary scintigraphy is more accurate, with specificity between 81-100% and sensitivity between 95-100% [3]. The pitfalls of scintigraphy include the fact that it does not allow evaluation of the remainder of the abdomen and that it may not be available in all hospitals. Fidler et al. [6] recently published a retrospective study describing the CT findings in 29 patients with AC. The most common findings at CT included GB distention, stranding of the pericholecystic fat, and GB wall thickening, consistent with our results. As previously reported by Terrier et al. [1], we believe that stranding of the pericholecystic fat is the most useful finding at CT, yet this sign has been poorly evaluated in the radiology literature (fig. 1 , 2and3) . Secondary involvement of the pericholecystic fat by AC is easy to detect at CT when appropriate window settings are used. The presence of GB inflammation often results in increased local blood flow leading to stranding of the pericholecystic fat. This type of pericholecystic inflammatory reaction has already been described by McDonnell et al. [4] at Doppler US (echogenic fat with increased flow corresponding to inflamed omental fat). A similar finding has also been described in the liver parenchyma next to the GB fossa by Yamashita et al. [5] at helical CT: transient increased local enhancement due to increased local blood flow related to inflammation. In our series, stranding of the pericholecystic fat was the most frequent finding at CT (13 of 14 cases) and was the only visible finding in one patient. Stranding was noted in patients with mild and severe AC. The only patient with AC where stranding was not present was very thin and had very little pericholecystic fat. Fidler et al. [6] reported the presence of stranding in 15 of 29 cases. This difference between the results of Fidler and al. and our results may be due to the fact that patients in the study by Fidler and al. were scanned between 1 and 17 days after onset of symptoms, after several patients had been treated with antibiotics, whereas most of our patients were scanned earlier (mean delay = 48 hours). We believe that the longer time delay and treatment with antibiotics have probably decreased the inflammatory reaction, hence decreasing the amount of stranding. However, this difference may also be the result of a selection bias or due to the small number of patients. Terrier et al. [1] did not specify the time interval between onset of symptoms and CT scanning in their patient population of 23 where stranding was present in 14.

Stranding of the pericholecystic fat is not specific for AC and may also occur in patients with inflammatory or malignant lesions of surrounding organs (colon, pancreas, duodenal bulb) but the site of primary pathology often is easily detectable.

GB distention and wall thickening are not specific for AC and may also occur in association with pathologies of other organs. In our series, GB distention was present in all patients with acalculous AC and 5 of 8 patients with GB stone. This is consistent with results from Fidler et al. [6] who also reported that GB distention was more common in patients with acalculous AC. However, Mirvis et al. [3], on a study of acalculous AC, did not report that GB distention was a major feature. GB wall thickening was not the most common finding in our patients, contrary to the reports by Lamki et al. [2] and Fidler et al. [6]. Subserosal edema was present in nearly 50% of our patients, 3 with stone and 3 with acalculous AC. Perihepatic or pericholecystic fluid was present in 6 of 8 patients with severe AC (fig. 1) . In addition, about half of these patients had complications such as biliary peritonitis or GB perforation, similar to what was reported by Lamki et al. [2]. This suggests that the presence of pericholecystic or perihepatic fluid is consistent with severe or complicated AC. However, this finding was present in only about 40% of patients, similar to the series by Fidler et al. [6]. The presence of gas in the GB wall, diagnostic of emphysematous AC, is rarely observed. This finding was seen in none of our patients.

CONCLUSION

CT is very useful for diagnosing AC and may either replace US or confirm diagnosis when US is inconclusive. Stranding of the pericholecystic fat is frequently noted in patients with AC and is highly sensitive. Detection of stranding is easy at CT, except in very thin patients.

 


(Les tableaux sont exclusivement disponibles en format PDF).

Figure 2.
Postcontrast CT image (5 mm thick), showing a gallstone, irregular thickening of the gallbladder wall and pericholecystic fat stranding.
TDM abdominale avec produit de contraste intraveineux, en coupes de 5 mm, montrant un calcul, un épaississement irrégulier de la paroi vésiculaire et une trabéculation de la graisse périvésiculaire.

Figure 3.
Postcontrast CT image (5 mm thick), showing moderate stranding of the pericholecystic fat.
TDM abdominale avec produit de contraste intraveineux, en coupes de 5 mm, montrant une trabéculation modérée de la graisse périvésiculaire.

Table I.
Tableau I.

(Les tableaux sont exclusivement disponibles en format PDF).

Table II.
Tableau II.

(Les tableaux sont exclusivement disponibles en format PDF).



REFERENCE(S)

[1] Terrier F, Becker C, Stoller C, Triller J. Computed tomography in complicated cholecystitis. J Comput Assist Tomogr 1984;8:58-62.

[2] Lamki N, Raval B, St Ville E. Computed tomography of complicated cholecystitis. J Comput Assist Tomogr 1986;10:319-24.

[3] Mirvis S, Vainright J, Nelson A et al. The diagnosis of acute acalculous cholecystitis: a comparison of sonography, scintigraphy, and CT. AJR 1986;147:1171-5.

[4] McDonnell C, Jeffrey R, Vierra M. Inflamed pericholecystic fat: color doppler flow imaging and clinical features. Radiology 1994;193:547-50.

[5] Yamashita K, Jin M, Hirose Y et al. CT finding of transient focal increased attenuation of the liver adjacent to the gallbladder in acute cholecystitis. AJR 1995;164:343-6.

[6] Fidler J, Paulson E, Layfield L. CT evaluation of acute cholecystitis: findings and usefulness in diagnosis. AJR 1996;166:1085-8.


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