Percutaneous Drainage and Alcoholization of Hepatic Abscesses in Five Dogs and a Cat
Hepatic abscesses are rare and difficult to diagnose in dogs and cats. Ultrasonographic examination is essential to thoroughly examine hepatic abnormalities, and it may also help in the localization of hepatic abscesses. In this retrospective study, five dogs and one cat with focal hepatic lesions compatible with a hepatic abscess were treated with percutaneous ultrasound-assisted drainage and alcoholization using 95% ethanol. The procedure was performed rapidly under injectable anesthesia and provided excellent results in all animals. No complications or relapses were noted for 120 days following the procedure. The technique of percutaneous ultrasound-assisted drainage and alcoholization of hepatic abscesses in the dog and cat is also described.
Introduction
A variety of hepatic diseases occur in dogs and cats, although hepatic abscesses are rarely diagnosed.1 Because of the nonspecific clinical signs associated with hepatic abscesses, they are often misdiagnosed as infectious or inflammatory diseases of the liver.2 Ultrasonographic examination allows better identification of hepatic abscesses, which in turn has created the opportunity to attempt different therapies for this condition. In veterinary medicine, it has been reported that hepatic abscesses may be treated by percutaneous ultrasound-guided drainage, a technique that is both effective and minimally invasive.3 In humans, satisfactory results have been reported with drainage and alcoholization of hepatic abscesses, thus avoiding the need for hepatic resection, which is associated with high morbidity.4 Percutaneous drainage and alcoholization reduced hospitalization time, since the abscess was sterilized.4 The purposes of this retrospective study were to describe the technique for ultrasound-assisted percutaneous drainage and alcoholization of hepatic abscesses and to evaluate the success of the procedure in dogs and cats.
Materials and Methods
The clinical records of six animals (five dogs, one cat) treated with percutaneous drainage and alcoholization of hepatic abscesses between January 1999 and September 2001 were reviewed. In all animals, the diagnosis of hepatic abscess was confirmed by cytological evaluation of the drained material. Data evaluated from these cases included signalment, clinical signs, laboratory findings, ultrasonographic results, and results of follow-up examinations.
Ultrasonography/Alcoholization Procedure
All animals were fasted for 12 hours, after which abdominal ultrasonography was performed with the animal in dorsal recumbency. The liver was thoroughly evaluated by sagittal and transverse scans. Hepatic lesions were classified as single or multiple, and the presence of septations was also determined for each lesion. The size of each lesion was determined in sagittal or transverse scans by measuring the longest dimension of the lesion. The outer hypoechoic parenchymal area (when found) was excluded from the measurement. The ultrasonographic appearance of the lesion was described and classified as reported by Schwarz, et al., into three types: anechoic (absence of internal echoes), hypoechoic or poorly echogenic (less echogenic than the surrounding liver), and mixed echogenicity (combination of echo patterns).3 The locations of the abscesses within the liver and the lobe affected were noted. Whether the abscess was deep within the parenchyma or in a peripheral subcapsular position was also recorded.
To perform drainage and alcoholization, all animals were anesthetized with diazepama (0.5 mg/kg intravenously [IV]) and ketamineb (10 mg/kg IV) and were placed in dorsal recumbency.5 The abdominal area was clipped and prepared aseptically. A percutaneous ultrasound-assisted drainage of the abscess was performed using a biopsy needle (20 gauge × 10 cm) with the echo-tipc attached to a 5- to 20-mL syringe and a 50-cm extension line. To avoid an excessive speed of aspiration of the abscess cavity, the amount of exudate to be removed was estimated, and a syringe with a volume twice that amount was chosen. The spinal needle was introduced into the abscess cavity under ultrasonographic guidance.3 When the tip of the needle was in the lesion, the stylet was removed, and the extension line with a sterile syringe of predetermined size was attached to the hub to permit drainage of the abscess contents. Before removing the spinal needle, alcoholization of the cavity was performed by infusing 95% ethanol. The amount of alcohol injected was equivalent to half the amount of the exudate removed. The alcohol-volume to syringe-volume ratio was never >1:2. The ethanol was left in the abscess cavity for 3 minutes and was then gently aspirated through the previously positioned spinal needle.
Follow-up Procedures
Each aspirated sample was submitted for aerobic bacterial culture and cytological evaluation. For bacterial culture, the sample was stored at 4° to 8°C in a sterile container with transport mediad and was sent to the laboratory within 4 hours of collection. Five smears, one for each drained cavity from each case, were prepared for cytological evaluation. All the slides were stained with May-Grünwald-Giemsa stain and were assessed by a single individual (Bonfanti).
The detection of short-term complications associated with drainage and alcoholization of the abscess was based on results of physical examination, complete blood count (CBC), serum liver enzyme activities, and abdominal ultrasonography performed 24 and 48 hours after the procedure. Evaluation of the long-term results was assessed by abdominal ultrasonography repeated at 15, 30, 60, and 120 days after the procedure in all six animals.
Results
Clinical and Laboratory Findings
This retrospective study included five dogs of different breeds and one Siamese cat. The animals ranged in age from 2 to 15 years [see Table]. All animals had nonspecific signs including anorexia (6/6, 100%), cranial abdominal pain (4/6, 66.68%), pyrexia (4/6, 66.68%), vomiting (2/6, 33.34%), and abdominal ascites (1/6, 16.67%). Laboratory findings in all animals included leukocytosis with a left shift and increased concentrations of serum alanine transaminase (ALT) and aspartate transaminase (AST) [see Table].
Ultrasonographic Findings
On ultrasonography, all six animals had a single lesion, which appeared as either a hypoechoic or anechoic area with irregular, hyperechoic margins [Figures 1, 2]. In some cases, there was also reduced echogenicity of the surrounding liver [Figure 1]. Large lesions had less echogenicity, with anechoic to fine hyperechoic contents [see Table]. The anechoic lesions showed variable distal acoustic enhancement in some of the abscesses. No evidence of septation was identified in any of the lesions on ultrasonography. All lesions were located in the right hepatic lobe. Within the lobe, two lesions had a peripheral subcapsular location (case nos. 3, 4), while the others were deep within the parenchyma.
On days 1 and 2 following the alcoholization procedure, all animals were submitted to ultrasound examination, and in all cases, a hyperechoic area proportional in size to the original lesion and surrounded by hypoechoic hepatic tissue was identified. On days 15 and 30, the previously described areas were not as echogenic and the peripheral hypoechoic ring had disappeared. At days 60 and 120 posttherapy, no parenchymal abnormalities were evident on ultrasonography (e.g., cavitated structures or cicatricial areas) in those animals treated for small abscess lesions (<3 cm; case nos. 1, 4, 6). In animals with larger lesions (case nos. 2, 3, 5), the follow-up evaluations showed hyperechoic areas proportional in size to the drained lesions. No evidence of recurrence of the hepatic abscess or complications related to the procedure was detected in any of the animals at the follow-up examinations.
Cytological and Bacteriological Results
Cytological examination was suggestive of abscessation [Figure 3] and revealed necrotic debris in a background of highly degenerated neutrophils (case nos. 1–3, 5, 6) and a small number of rod-shaped bacteria compatible with Enterobacteriaceae (except in case no. 4). No neoplastic cells were found in any of the cytological samples. In case no. 4, the bacterial culture was negative. This dog had received antibiotics (i.e., enrofloxacin) for 72 hours prior to the aspirate, which may have affected the culture results. Culture results of all other animals were positive for Escherichia coli, suggesting a biliary origin from ascending cholangitis as previously described.6–10 All animals were treated with appropriate antibiotics based upon the microbial culture results for 30 days.
Complications and Follow-up
Based on the results of physical examination, CBC, serum biochemical profile, and abdominal ultrasonography performed 24 and 48 hours after the procedure, there was no evidence of any complications related to the technique. Anorexia, abdominal pain, and pyrexia resolved in all six animals within 48 to 72 hours after drainage and alcoholization, and all animals returned to a clinically normal state during the first week following the procedure. No animals were treated with analgesics, nonsteroidal antiin-flammatory drugs, or opioids. Follow-up ultrasound evaluations at 15, 30, 60, and 120 days after drainage and alcoholization showed no evidence of complications and/or relapse of the abscess in any animal.
Discussion
In dogs and cats, ultrasonography facilitates the diagnostic approach to suspected hepatic abscesses. Sagittal and transverse scans permit a more accurate assessment of hepatic size, location, parenchymal echostructure, and vascular anatomy as well as structural features of the biliary tract.2 Since the advent of ultrasonography, the number of the hepatic abscesses identified has increased.3 The differential diagnoses for the hepatic lesions described in the study reported here included hepatic abscess, hematoma, metasta-tic neoplasia, and biliary cystadenoma.2 Biliary cystadenoma can appear as a cystic lesion or as a mass lesion, with increased or mixed echogenicity.2 Hematomas are typically located in the subcapsular area and usually have a thick and moderately hyperechoic wall, hypoechoic contents, and distal acoustic enhancement.2 Hepatic abscesses are often anechoic or hypoechoic, variable in size, and have irregular margins. The contents of hepatic abscesses may be mildly to moderately hyperechoic, and variable distal acoustic enhancement may be noted.2 The parenchyma surrounding hepatic abscesses may appear hypoechoic. Metastatic neoplastic lesions are usually multifocal and may also have a “target” appearance.2 However, a primary hepatic tumor may have an appearance similar to liver abscesses, especially if a necrotic center is present.2 Unlike abscesses, though, a tumor will generally have regular margins.2 The similar ultrasonographic findings for both liver neoplasia and hepatic abscesses require cytological and/or histopathological examination to reach a definitive diagnosis.
The lack of clinical signs and laboratory abnormalities specific for a hepatic abscess does not permit a definitive diagnosis without further investigation and testing. In the present study, anorexia was the most common clinical sign, followed by a hunched posture and pain on abdominal palpation. Laboratory findings showed both leukocytosis and elevations in liver enzyme activities, all of which may occur with other hepatic disorders.111 In this study, ultrasonographic evaluation and ultrasound-guided aspiration with cytological examination of material from the affected area proved to be very valuable in confirming the presence of a hepatic abscess.
Some authors have associated hepatic abscesses with concurrent diseases or certain predisposing factors, such as infectious diseases of the pancreas and/or biliary tract and immunosuppressive disorders (e.g., diabetes mellitus, hyperadrenocorticism).1 Based upon laboratory tests and abdominal ultrasonography, there was no evidence of cholangitis, cholecystitis, pancreatitis, or immunosuppressive diseases in any of the animals in this report. In case no. 4, the peripheral subcapsular location of the abscess, an epigastric reactive inflammatory zone characterized by hyper-echogenicity of the surrounding tissue and a thickened hypoechoic gastric wall, suggested a transparietal infection possibly arising from a penetrating foreign body, even though it could not be identified upon standard radiography. In all of the cases presented here, the abscess occurred within the right liver lobe. According to reports in humans, the higher incidence of abscesses in the right lobe may reflect a biliary origin of the pathology.6–10 Only solitary hepatic abscesses were identified in this study, a finding that was consistent with previous reports in dogs.11
The bacteria isolated from the hepatic lesions in this study were from the Enterobacteriaceae family, further suggesting a biliary origin from ascending cholangitis as previously described.6–10 Anaerobic bacterial cultures were not performed, and this may have limited the identification of etiological agents. In a prior study of dogs with hepatic abscesses, however, anaerobic cultures were all negative.3
Possible complications of percutaneous drainage of hepatic abscesses include rupture of the abscess, leading to circumscribed or generalized peritonitis. These complications are most likely to occur with peripheral subcapsular abscesses, similar to peripheral complicated cysts.12 Abscesses may also rupture when a large amount of ethanol is used and/or if the alcohol is infused at a high rate of speed. Limiting the aspiration speed by keeping the estimated exudate-volume to syringe-volume ratio at 1:2 and injecting a precise amount of ethanol (equivalent to half the amount of the exudate removed) are believed to help prevent this complication. No complications occurred following these precautions in the animals of this report.
In dogs and cats, hepatic abscesses may be diagnosed and treated via laparotomy, laparoscopy, or percutaneous ultrasound-guided techniques.311 The drainage and 95% ethanol alcoholization technique used here was similar to the procedure reported in humans for the treatment of pyogenic liver abscesses.4 The advantages of this technique, when compared to drainage procedures alone, are the absence of complications and relapses, no requirement for maintaining indwelling catheters for continuous drainage, and no need for successive surgical intervention. The ultrasound-assisted drainage procedure reported by Schwarz et al. had a lower mortality rate and more favorable results compared to the temporary drainage technique described by Farrar et al.11 The technique presented here had no mortality, irrespective of the size of the lesion, and was followed by positive clinical results within a short period of time (e.g., absence of abdominal pain within 48 hours). The costs were also significantly lower than those incurred with classical surgical approaches.
Conclusion
The ultrasound-assisted percutaneous drainage and alcoholization technique for hepatic abscess in the dog and cat appeared to be an excellent alternative to surgical treatment. The procedure was rapid, was not accompanied by any complications or morbidity, resulted in complete resolution of the hepatic abscess, and cost less than other therapeutic procedures.
Diazepam 0.5%; Gellini International srl, Aprilia (LT), Italy
Ketavet 100; Gellini International srl, Aprilia (LT), Italy
V-DCHN-20-10.0-ET; Cook, Australia
Sterile Transport Swab; Aptaca, Italy
Citation: Journal of the American Animal Hospital Association 41, 1; 10.5326/0410034
Citation: Journal of the American Animal Hospital Association 41, 1; 10.5326/0410034
Citation: Journal of the American Animal Hospital Association 41, 1; 10.5326/0410034
Anechoic area, 1.8 cm in diameter (line between white marks), located in the right hepatic lobe of a 7-year-old, male, mixed-breed dog (case no. 1). The white arrows indicate the hypoechoic parenchymal area that was excluded from the measurement.
Anechoic area, 8 cm in diameter (line between white marks), with irregular margins characteristic of an abscessed lesion located in the right hepatic lobe of a 6-year-old, female schnauzer (case no. 2).
Cytology of an aspirate of a hepatic abscess (case no. 2) revealing highly degenerate neutrophils (white arrows), necrotic debris (white arrowheads), and rod-shaped bacteria (black arrows) compatible with Enterobacteriaceae (May-Grünwald-Giemsa stain, 40×).
