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1 Department of Radiology, Kurobe City Hospital, 1108-1 Mikkaichi, Kurobe
938-0031, Japan.
2 Present address: Department of Radiology, Toyama City Hospital, 2-1
Imaizumihokubu, Toyama 939-8511, Japan.
3 Department of Radiology, Kanazawa University School of Medicine, 13-1
Takaramachi, Kanazawa 920-8641, Japan.
4 Department of Gastro-Enterology, Kurobe City Hospital, Kurobe 938-0031,
Japan.
Received October 8, 2002;
accepted after revision December 6, 2002.
Address correspondence to K. Arai.
Abstract
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MATERIALS AND METHODS. Inhomogeneous enhancement of hepatic parenchyma was retrospectively evaluated on dynamic CT in 406 consecutive patients without irregular fatty liver or multiple hepatic tumors. Dynamic CT scans were obtained 30 sec (early phase) and 90 sec (late phase) after starting the contrast material injection. Thirteen patients were diagnosed as having acute cholangitis (cholangitis group), and the remaining 393 patients were classified as the control group. The frequency of inhomogeneous enhancement was compared between these two groups. In nine of the 13 patients in the cholangitis group, we also evaluated changes in inhomogeneous enhancement on follow-up dynamic CT scans obtained after the patients had undergone treatment for acute cholangitis.
RESULTS. In the cholangitis group, 11 (85%) of 13 patients showed nodular, patchy, wedge-shaped, or geographic inhomogeneous enhancement throughout the liver in the early phase on dynamic CT. In the control group, 19 (5%) of 393 patients also showed inhomogeneous enhancement in the early phase on dynamic CT. The frequency of inhomogeneous enhancement was significantly higher in the cholangitis group than in the control group (p < 0.001). Follow-up dynamic CT performed after treatment for acute cholangitis showed decreased inhomogeneous enhancement or no inhomogeneous enhancement in seven (78%) of nine patients in the cholangitis group.
CONCLUSION. Inhomogeneous enhancement in the early phase on dynamic CT is frequently seen in patients with acute cholangitis; this finding usually disappears after treatment.
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Recent advances in CT technology allow the whole liver to be evaluated on dynamic studies without difficulty. On dynamic CT, inhomogeneous enhancement of nontumorous hepatic parenchyma is occasionally seen in patients with various conditions [3–12]; however, to our knowledge, no reports about the dynamic CT findings of acute cholangitis have been published.
Recently, we noticed that inhomogeneous hepatic enhancement in the early phase on dynamic CT is frequently seen in patients with acute cholangitis, so we retrospectively analyzed this finding.
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Thirteen of the 406 patients were diagnosed with acute cholangitis and classified as the cholangitis group. The cholangitis group comprised eight men and five women, ranging in age from 50 to 88 years (mean, 73 years). Acute cholangitis was diagnosed if there was clinical evidence of infection (fever, chills, or leukocytosis), abdominal pain or tenderness, jaundice or hyperbilirubinemia (bilirubin value, ≥ 2.5 mg/dL), abnormal findings on liver function tests (especially an increased level of alkaline phosphatase), and no clinical features indicating other infectious diseases. In the cholangitis group, bile cultures alone were available for three patients, blood cultures alone were available for two patients, and both were available for two patients. Culture findings for five of the seven patients were positive.
The remaining 393 patients were classified as the control group. This group was composed of 233 men and 160 women, ranging in age from 27 to 94 years (mean, 64 years).
The possible causes of acute cholangitis were as follows for the 13 patients in the cholangitis group: common bile duct stones (n = 3), pancreatic cancer treated with biliary stents (n = 2), gallbladder cancer (n = 2), bile duct cancer (n = 2), previous choledochojejunostomy (n = 1), gallstone with or without duodenal diverticulum (n = 2), and unknown (n = 1).
After unenhanced CT scans were obtained, dynamic CT was performed using multidetector CT (Somatom Volume Zoom, Siemens, Erlangen, Germany). With the use of a power injector, 100 mL of nonionic contrast material (300 mg I/mL) was IV administered at a rate of 2.5 mL/sec. Dynamic CT (2.5-mm collimation, a pitch of 5, a table speed of 12.5 mm per rotation, and a 0.5-sec gantry rotation period) was initiated 30 sec (early phase) and 90 sec (late phase) after starting contrast material injection.
The degree of inhomogeneous enhancement of nontumorous hepatic parenchyma was classified as grade 0, 1, or 2 by visual assessment of its extent and distribution rather than intensity. The grades was defined as follows (Figs. 1A, 1B, 1C, 2A, 2B, 2C, 3A, 3B, 3C): grade 0, no inhomogeneous enhancement of hepatic parenchyma; grade 1, intermediate enhancement (between grades 0 and 2); and grade 2, marked inhomogeneous enhancement throughout the liver.
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The frequency of inhomogeneous enhancement in the cholangitis group was compared with that in the control group. Fisher's exact test was used for statistical analysis.
In the cholangitis group, follow-up CT was performed after treatment in nine patients who showed inhomogeneous enhancement before treatment, and the grade of inhomogeneous enhancement was reevaluated. Of these nine patients, five underwent bile duct drainage combined with antibiotic therapy, and four underwent antibiotic therapy alone.
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Follow-up CT was performed in nine patients. Before undergoing treatment, four of these nine patients had grade 2 inhomogeneous enhancement and five had grade 1. On follow-up dynamic CT, a decrease in inhomogeneous enhancement was seen in seven (78%) of the nine patients, six of whom had grade 0 inhomogeneous enhancement.
In the control group, five (1.3%) of 393 patients showed grade 2 enhancement, 14 (3.6%) showed grade 1 enhancement, and 374 (95.2%) showed grade 0 enhancement in the early phase on dynamic CT. In the late phase, all but one showed grade 0 enhancement.
The difference in the frequency of inhomogeneous enhancement in the early phase on dynamic CT between the cholangitis group and control group was statistically significant (p < 0.001, Fisher's exact test).
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Inhomogeneous enhancement in the early phase on dynamic CT or transient hepatic attenuation differences on dynamic CT are seen in various hepatic diseases such as liver cirrhosis, Budd-Chiari syndrome, hepatic congestion, cavernous transformation of the portal vein, acute cholecystitis, hepatic tumor, or abscess [3–12]. These areas of abnormal enhancement are seen as subcapsular, focal nodular, wedge-shaped, segmental, lobar, or diffuse in shape and distribution. The mechanisms of abnormal enhancement are arterioportal shunt [11], portal vein compression or obstruction [3, 4], hepatic vein outflow obstruction [6], local hyperemic change [8, 10], aberrant blood supply [13], steal phenomenon [3], and unknown cause [5]. In patients with acute cholangitis, inhomogeneous enhancement was seen as nodular, patchy, wedge-shaped, or geographic throughout the liver only in the early phase on dynamic CT, and this finding was considered to be reversible.
The liver has a dual blood supply from the portal vein and hepatic artery. The peribiliary plexus plays an important role for the connection between the two vessels [14]. In patients with acute cholangitis, an inflammatory process may occur in the portal tracts, the peribiliary plexus may be dilated, and hepatic arterial blood flow may be increased via the dilated peribiliary plexus. Increased blood flow may be a cause of inhomogeneous enhancement when these inflammatory reactions occur inhomogeneously.
In patients with a hepatic abscess, segmental hepatic enhancement is frequently seen in the early phase on dynamic CT, and this finding is reversible [12]. Gabata et al. [12] reported that the portal tracts of the hepatic parenchyma surrounding a hepatic abscess showed marked inflammatory cell infiltration and stenosis of portal venules, which may result in reduced portal flow and a compensatory increase in arterial flow. In acute cholangitis, this phenomenon may be seen in portal tracts inhomogeneously and may be a cause of inhomogeneous enhancement.
The diagnosis of acute cholangitis is mainly based on symptoms, physical findings, and laboratory data. Imaging studies are required for the evaluation of the presence, degree, and cause of biliary obstruction and the severity of disease. However, when the diagnosis of acute cholangitis is questionable, dynamic CT may add information useful for the diagnosis. Because acute cholangitis occasionally results from the obstruction of bile ducts by a malignant tumor [1, 2], nodular enhancement may be confused with hepatic metastases. Therefore, it is important to understand that inhomogeneous enhancement seen only in the early phase on dynamic CT is a typical finding in patients with acute cholangitis.
In conclusion, inhomogeneous enhancement of the liver is frequently seen in patients with acute cholangitis in the early phase on dynamic CT, and this finding is no longer present after treatment. Early inhomogenous enhancement may be a useful complementary finding for the diagnosis of acute cholangitis.
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