Sonography of Hepatic Amebic Abscesses

Transcription

1 911 Richard J. Sukov1 Lawrence J. Cohen1 W. Frederick Sample2 Received September 4, 1 979; accepted after revision January 1 5, I Department of Radiology, Centinela Hospital Medical Center, Inglewood, CA and Daniel Freeman Hospital, lnglewood, CA Address reprint requests to R. J. Sukov, 323 N. Prairie Ave., #124, lnglewood, CA Department of Radiology, UCLA Center for the Health Sciences, Los Angeles, CA Dr. Sample is deceased. AJR 134: , May X/80/ $00.00 Sonography of Hepatic Amebic scesses The spectrum of gray scale ultrasonographic patterns are described as seen in 17 hepatic amebic abscesses in eight patients. Of the abscesses 1 6 had a lower gray tone than the adjacent normal liver. In patients with multiple lesions, generally there was a reciprocal relation between abscess size and echogenicity and a direct relation between internal echogenicity and through transmission. The results in these eight patients suggest a role for ultrasound both in the diagnosis and treatment of hepatic ameblc abscesses. Gray scale ultrasound is used with increasing frequency both for the detection and characterization of hepatic mass lesions. Several reports detail the variety of gray scale patterns seen in hepatic neoplastic [1 ], inflammatory [2, 3], and benign cystic disease [4, 5]. However, except for one recent report [6], hepatic amebic abscesses have only been described in detail using older bistable instrumentation [7, 8]. We describe the spectrum of gray scale ultrasound findings seen in 17 hepatic amebic abscesses studied in eight patients. Subjects and Methods Eight patients were evaluated: six men and two women, aged years. All had a discharge diagnosis of hepatic amebic abscess based on clinical findings and the appropriate confirmatory pathoradiologic examinations. These included an indirect hemagglutination titer of 1 :51 2 or greater in seven of the eight patients, and a positive amebic counterimmunoelectrophoresis in three of the four patients examined for this. The one patient who did not show prompt improvement on Metronidazole had an ultrasound-assisted abscess aspiration that confirmed the diagnosis. In each patient, the initial hepatic sonogram and 99mTc sulfur colloid radionuclide liver scan were obtained within 30 hr of each other. In four patients, the sonography preceded the isotope study. Prior to sonography, the working diagnoses had been cholecystitis and/ or cholelithiasis in three of the patients and hepatitis in the fourth. In each patient, sonography was the first diagnostic procedure to elucidate sufficiently the nature of the underlying disease process to suggest the diagnoses of a liver abscess. Two of the patients underwent two sonographic examinations each, and a third patient had six examinations over an 8 month period. Two patients had computed tomography (CT) performed both with and without contrast enhancement on the same day as the initial sonogram. A third patient had a nonenhanced scan 20 days after the initial sonogram and a second study 1 4 weeks later. Gray scale ultrasound examinations were performed on several different commercially

2 912 SUKOV El AL. AJR:134, May 1980 available units. Either a 2.25 or 3.5 MHz transducer was used, depending on the patient s body habitus. Images were recorded on a variety of formats including hard copy and 90 mm and Polaroid films. Initial hepatic sonography was performed in the supine position at 1 cm intervals in both the transverse and longitudinal planes. Oblique and decubitus scans were obtained when indicated. Results A total of 17 abscesses was identified in the eight patients. Five patients had multiple abscesses. One patient had five abscesses; no other patient had more than three. Only one abscess was confined to the left lobe of the liver (fig. 1). -a.- Fig. 1 -Transverse sonogram. Three of five abscesses () and only abscess in series confined to left lobe of liver (Li). Sp = spine. LI sp -.4 Differentiation of this lesion from a fluid-filled stomach or some other extrahepatic left upper quadrant process was accomplished by longitudinal and right decubitus scans. Radionuclide and CT studies subsequently confirmed the initial ultrasound impression. A second abscess was midline and probably involved part of the left lobe. The incidence of multiple abscesses was higher in this small group than is usually reported; however, the marked predilection for the right lobe is consistent with other observations [9-1 1]. The size range of the abscesses was cm. They were generally round and, except for one, well demarcated from the adjacent normal parenchyma (fig. 2). The abscesses had a wide spectrum of sonographic appearances. Sixteen had a lower gray tone than the adjacent normal liver, a feature that has been observed by others [6]. One abscess had a rim, for most of its periphery, that was more echogenic than the adjacent liver (fig. 3A). This rim corresponded to a wide halo of enhancement seen in the same abscess on a postcontrast CT scan (fig. 3B). In the patients with multiple lesions, there was a reciprocal relation between abscess size and echogenicity. Echogenicity decreased as the size of the abscess increased (fig. 4). The degree of sound transmission varied considerably. However, in individuals with multiple lesions, there appeared to be a direct relation between internal echogenicity and through transmission. It is interesting that posterior wall sound transmission generally increased with increasing abscess echogenicity (fig. 5). The abscesses evaluated in the three patients undergoing serial sonographic examinations did not show any characteristic sonographic changes other than a decrease in size (fig. 6). There was excellent correlation between the radionuclide scans and sonograms as to size, number, and location of abscesses in all eight patients. In the three patients undergoing Cl, low density foci : i.-,; -.;TI#{149}w : A B Fig. 2.-A, Transverse sonogram of only abscess () in series not well demarcated from adjacent normal liver (Li) on ultrasound. B, scess more sharply defined on contrast-enhanced CT scan at about same level. SP = spine.

3 AJR:134, May 1980 HEPATIC AMEBIC ABSCESSES 913 Fig. 3.-A, Longitudinal sonogram. Solitary abscess () with rim (r) more echogenic than adjacent normal liver (Li). B, Wide halo (h) of enhancement between arrows on postcontrast CT scan of same abscess. H = head; St = stomach. Fig. 4.-Longitudinal sonogram through widest parts of both abscesses () in liver (Li). Reciprocal relation between abscess size and echogenicity. Several of many echoes in smaller lesion (arrow). H = head; Gb = gallbladder; Rk = right kidney. corresponded with the ultrasound findings. In one of the patients who received intravenous contrast material, a wide enhancing halo was demonstrated. No rim of enhancement was seen in our second patient who received contrast material. The third patient had two nonenhanced scans 1 1 weeks apart (fig. 7). The second scan showed a regression in both the overall size of the liver and the individual lesions. However, residua of the abscesses were still easily identified as prominent relatively low density areas. This time course is not unusual. Although most amebic liver abscesses heal gradually over 2-4 months, occasionally the resolution time may be as long as a year [12].. ** Fig. 5.-Transverse sonogram. Direct relation between abscess () internal echogenicity and through transmission. More echogenic of these two abscesses also has most through transmission (arrow). R = right: Li = liver; Sp = spine. Discussion Amebic liver abscess is caused by the organism E. histolytica. Although it is much less common in the United States than in Latin America and other parts of the world where it is endemic, it is seen here with increasing frequency as a result of international travel and migration. The disease may cause a variety of clinical symptoms and prompt diagnosis is important to initiate therapy and avoid potentially fatal complications [1 3]. Although there is no universal agreement as to what constitutes the most effective therapy, Metronidazole (flagyl) an amoebicidal drug is

4 - 914 SUKOV El AL. AJR:134, May 1980 A Fig. 6.-A, Longitudinal scan. Part of three of five lesions in patients with multiple abscesses. Of abscesses, (A) is more echogenic than (B). B, Longitudinal scan through same plane 6 months later. variable response to treatment. Although lesions have diminished, abscess A is now less echogenic than B. H = head. Fig. 7.-A, Nonenhanced CT scan on same patient shown in fig. 1, 20 days after diagnosis of hepatic amebiasis. Three large abscesses (A). B, 1 1 weeks later, nonenhanced scan at same level. Regression in size of liver (Li) and individual abscesses. B generally used in this country. Usually, aspiration and/or decompression are performed only if there is no response to the amoebicidal drugs, if there is deterioration in the general condition, or if rupture seems imminent. Many of the 1 7 abscesses in our group bore a strong sonographic resemblance to previous descriptions of hepatic neoplastic, inflammatory, and benign cystic disease. No sonographic characteristic of solitary abscesses was identified which could be considered diagnostic of hepatic amebic abscess and enable reliable differentiation from these other processes. However, the patterns seen in patients with multiple abscesses have not previously been associated with other hepatic mass lesions and are sufficiently unusual to warrant further discussion. A recent study demonstrated that the echogenicity of hepatic amebic abscesses is a function of gain setting, and that increased gain setting will result in increased abscess echogenicity [14]. Through transmission is undoubtedly affected in a similar fashion. These findings tend to invalidate attempts to compare the sonographic characteristics of an abscess evaluated in one patient with an abscess scanned in another. However, these observations should not obviate compari-

5 AJR:134, May 1980 HEPATIC AMEBIC ABSCESSES 915 sons among multiple abscesses occurring in one individual. Our findings suggest that in the individual who has multiple abscesses, the smallest abscess will frequently be not only the most echogenic but also have the most through transmission. Although one might have expected the smaller lesion to be the more echogenic, the associated increase in through transmission is somewhat atypical for a partially fluid lesion. The explanation for these findings is not known but probably relates to acoustical changes not only in the fluid content of the abscess but also the abscess wall and adjacent liver. If our observations are substantiated by 0thers, these relations may prove useful in facilitating the diagnosis of hepatic amebic abscess. The capacity of sonography to evaluate large areas in a screening fashion made it superior to organ-specific examinations (cholecystography, barium examinations, or urography) as a diagnostic imaging method in several of the patients who had a vague symptomatology. This capacity suggests a role for sonography in similar patients even if the patterns we observed in patients with multiple abscesses do not emerge as characteristic after more extensive study. Once the liver was identified as the responsible organ, sonography was as sensitive as radionuclide scans for determining the number, size, and location of lesions. It has the added advantage of not using ionizing radiation and provides an excellent means of following abscess size and assessing response to therapy in patients where clinical findings are confusing. In addition, sonography, like radionuclide scanning, accurately demonstates the topographic relation between the abscess and liver margins in both the transverse and longitudinal planes. This capacity is important because extrahepatic extension (chest, pericardium, peritoneal cavity) greatly increases mortality [1 3]. Therefore, some workers preferentially aspirate abscesses adjacent to the margins of the liver (particularly its diaphragmatic surface) in order to avoid spread [1 5, 1 6]. Sonography is efficacious for both localization and percutaneous aspiration [1 7, 18]. ACKNOWLEDGMENTS We thank Irene Noel for manuscript preparation, Mark Mercier and the Centinela Hospital Medical Center Department of Medical Photography for photography, and Dennis Sarti for figure 5. REFERENCES 1. Wooten WB, Green B, Goldstein HM. Ultrasonography of necrotic hepatic metastases. Radiology 1978; 1 28 : Doust BD, Doust VL. Ultrasonic diagnosis of abdominal abscess. Am J Dig Dis 1976;21 : Lawson TL. Hepatic abscess. Ultrasound as an aid to diagnosis. Am J Dig Dis 1977;22: Spiegel RM, King DL, Green WM. Ultrasonography of primary cysts of the liver. AJR 1978;1 31 : Weaver AM Jr, Goldstein HM, Green B, Perkins C. Gray scale ultrasonographic evaluation of hepatic cystic disease. AJR 1978;1 30: RaIls PW, Meyers HI, Lapin SA, Rogers W, Boswell WD, Halls J. Gray scale ultrasonography of hepatic amoebic abscesses. Radiology 1979;1 32: Matthews AW, Gough KR, Davies ER, Ross FGM, Hinchliffe A. The use of combined ultrasonic and isotope scanning in the diagnosis of amoebic liver disease. Gut I 973;1 4 : Monroe LS, Leopold GA, Brown JW, Smith JL. The ultrasonic scan in management of amebic hepatic abscess. Am J Dig Dis : Barbour GL, Juniper K. A clinical comparison of amebic and pyogenic abscess of the liver in sixty-six patients. Am J Med 1 972;53 : Cuaron A, Gordon F. Liver scanning: analysis of 2,500 cases of amebic hepatic abscesses. J NucI Med I 977;1 1 : Rasaretnam A, Wijetilaka SE. Left lobe amoebic liver abscess. Postgrad Med J 1976;52: Sheehy 1W, Parmley LF Jr, Johnston GS, Boyce HW. Resolution time of an amebic liver abscess. Gastroenterology 1 968;55 : Adams EB, MacLeod IN. Invasive amebiasis: amebic liver abscess and its complications. Medicine 1977;56: RaIls PW, Meyers HI, Lapin SA. Spectrum of gray scale ultrasonographic findings in hepatic amoebic abscess. Exhibited at the annual meeting of the Radiological Society of North America, Atlanta, November Crane PS, Lee Yl, Seel OJ. Experience in the treatment of two hundred patients with amebic abscess of the liver in Korea. Am JSurg 1972;123: lbarra-perez C, Selman-Lama M. Diagnosis and treatment of amebic empyema. Report of eighty-eight cases. Am J Surg 1977;1 34: Smith EH, Bartrum RJ. Ultrasonically guided percutaneous aspiration of abscesses. AJR 1974;1 22: Vicary FR, Cusick G, Shirley IM, Blackwell AJ. Ultrasound and amoebic liver abscess. Br J Surg 1 977; 64 :