There are times when our noble steed - the liver which carries us to the gates of heaven and the dungeons of hell, standing by our side at all times - is impugned by bruises. I'm not referring to physical bruises (though it is possible if the patient has coagulopathy or is experiencing a hyperacute complication of liver transplant), but metaphorical ones. As we can see on the cover image, which is a contrast-enhanced CT scan of the abdomen, the most remarkable finding is a very large, well-circumscribed hypodense lesion in the liver which exerts significant mass effect in the abdomen, leading to the displacement of adjacent anatomical structures. By reading the entire stack of CT images, the lesion is localised at Segment IV of the liver (Couinaud Classification). Although I described it in such precise, technical terms, one still cannot dispel the primordial impression that it looks like a huge bruise. In this article, I dive deeper in the nature of this 'bruise' and what it means in diagnosis and treatment.
Whenever we look at scans and perceive a round, well-circumscribed lesion encapsulated by a ring of different density, there are two pieces of information we can glean off the finding: (1) there are two distinct layers which are formed from different materials; (2) it is reassuring since the lesion is well-circumscribed and is not likely to spread in size. It can spread in number and it is important thus to screen for similar lesions in the organ (in this case, the liver) and other systems to see if it is a systemic issue. There are several prime suspects since not many pathologies present this way: (a) cancer (respectively primary and metastatic), (b) abscess, (c) cavitary inflammation and (d) radiation necrosis. This list of differentials can be used across all bodily systems. Some systems may feature additional differentials. For instance, in the brain, we might focus on stuff like demyelination (indicative of multiple sclerosis most commonly), contusion and subacute infarct (stroke), as well. For the lungs, there is a debate as to whether such a lesion constitutes to cancer or cavitary pneumonia, or autoimmunity (think of granulomatosis with polyangiitis and rheumatoid nodules, which can feature cavities). In the following, I shall take the liberty to elaborating on cancerous lesions and abscesses, since radiation necrosis is possible if a patient has ever received radiotherapy.
A clinical picture showing the gross pathology of an amoebic liver abscess (extracted from: https://lookformedical.com/img/b/bd/Liver_containing_amebic_abscess_gross_pathology_3MG0042_lores.jpg)
A clinical picture showing an excised liver invaded by multiple abscesses of varying sizes (extracted from: https://media.springernature.com/lw785/springer-static/image/chp%3A10.1007%2F978-4-431-55200-0_23/MediaObjects/311023_1_En_23_Fig3_HTML.jpg)
It is a well-known fact that cancers do form cavities. This occurs due to the high cellular turnover within the tumour. However, all this cellular replication requires immense energy. Even setting aside the fact that tumours don't always get the nutrients they need, the competition for survival is intense. Even in the world of carcinogenesis, survival is only for the fittest. Those who are unable to make it undergo apoptosis. Over time, swathes of tissue undergo necrosis. This draws a line between the living and the deceased and contributes to the formation of a cavity. Taking lung cancer as an example, most cancers that form cavities are of squamous cell type. This is accompanied by large cell carcinomas, and adenocarcinomas. Small cell lung carcinomas (the rapidly progressive subtype which requires systemic radiotherapy and chemotherapy and brain irradiation at the first instance where surgery is never a viable treatment option) rarely cavitate. In a study involving 632 bronchial carcinomas (of primary source), 100 cases of necrosis and cavitation were observed. 82 out of 100 cases were of squamous cell type. [5] There was no data provided by the paper on secondary cancers. We should, however, be aware of them since they are clinically significant. Head and neck cancers are predominantly of squamous cell type and there is a metastasis rate of 4 to 26 per cent. Brain metastases account for less than 1 per cent. [6]
CT plus contrast of the thorax, in which there is a cavitating lesion located over the lower lobe of the left lung. It is a squamous cell carcinoma (extracted from Radiopaedia on URL: https://radiopaedia.org/cases/cavitating-left-lower-lobe-lesion-squamous-cell-lung-cancer-2?lang=gb)
There are clues which can convince us that a lesion is more likely to be an abscess than a cancer. The number and distribution do not necessarily matter, though they are helpful. After all, both microbes and tumour cells have the ability to traverse across the systemic vasculature and invade all sorts of bodily systems. They can also invade multiple sites of the same organ. The key feature, in my opinion, is the regularity in contour. Abscesses are collections of pus surrounded by granulation tissue - an inflammatory reaction walling off the battlefield from the rest of the body to control the infection. They are benign in essence. The contour is usually regular. For cancers, referring to the CT Scan above, we can see that the contours are largely irregular (or jagged, in my view). Drawing this distinction is necessary in diagnosis. Sometimes, it is asserted that in the context of the lungs, thick-walled cavities mean cancer. However, this thinking should not be taken as absolute, since thick-walled cavities accompanied by neighbouring ground-glass opacities may indicate cavitary pneumonia featuring stars such as Klebsiella pneumoniae and Streptococcus pneumonia.
Moreover, abscesses can feature air-fluid levels representative of pus accumulation. On the CT scan, the density of fluid is higher than air. In abscesses, due to the presence of pus, the central density is comparably higher than central necrosis present in cavitating cancers. If in doubt, measure the Hounsfield Units of that particular tissue section.
CT plus contrast of the thorax which shows a cavitary lesion over the left lower lobe. Again, this prompts us to think about cancer. However, we can see that there is adjacent ground-glass opacification which is more diffuse as we scroll up the stack (only one image is shown here). The patient's condition is of moderate severity (CURB-65) and a blood test is performed. Klebsiella pneumoniae is cultured as the predominant microbe. (Extracted from: https://www.radiologyinfo.org/gallery-items/images/ct-cavitary-pneumonia.jpg)
Scan A is a PA-view Chest X-Ray. Scans B and C are contrast-enhanced CT Scans of the thorax (B= axial; C = coronal). They all show an abscess over the right upper lobe with an air-fluid level. (extracted from BMJ Case Reports [7]).
LIVER ISSUES
What about the liver? From the logic above, metastases to the liver (especially from the oropharynx and lungs) can certainly contribute to a cavitary appearance. I can find no literature regarding the formation of cavities in hepatocellular carcinomas. We focus more on the possibility of abscesses in the liver. Even then, abscesses are not common in the general population. The incidence is estimated at 2.3 per 100,000 individuals, with male predominance (3.3 in males vs 1.3 in females, per 100,000 individuals).
Aetiologies - the ones seated on the throne:
There are two types of liver abscesses, defined by the type of microbe underlying their pathophysiology: (1) amoebic, (2) pyogenic. [8] Amoeba is a type of parasite which is found more often in developing countries. It was shown that the most predominant amoebic species found in liver abscesses was Entamoeba histolytica (87.5 per cent of all cases). [9] Another distinct amoebic species identified in microbiology, Entamoeba dispar, does not cause clinically significant conditions. Amoebic liver abscess is also significantly associated with poor personal hygiene (especially not washing hands after handling gardening tools and performing agricultural duties) and clustering. In certain ethnic groups, like the Senoi in Malaysia, other significant risk factors include contact with domesticated animals, eating with hands and raw vegetable consumption. [1, 11] Pyogenic liver abscesses feature bacteria instead and they can come in all shapes and sizes. Examples include Klebsiella pneumoniae, Escherichia coli and Enterococci. However, they are by no means the only ones which are cultured. It ultimately depends on the source of the infection and the method of inoculation. The liver is a sacred temple that is quite hard to reach directly - very different from oral structures like the teeth, gums and tongue in this respect. Identified pathways of liver infection (thus abscess formation) include acute cholangitis, spillover of adjacent inflammation/infection (such as peptic ulcers), penetrating or iatrogenic injury (where the penetrating foreign body carries microbes and they are delivered straight to the threshold of the temple), haematogenous spread (most common, where there is systemic spread of disease; we also have to be wary of intravenous drug users) and portomesenteric spread. Portomesenteric is a difficult word - it is the amalgamation of 'portal' and 'mesenteric', meaning that bacteria in the gut are carried through the portal venous system to the liver. Needless to say, this is very reasonable since the liver, overall, receives most of its blood supply from the portal venous system. [10] There is an interesting case where an elderly man presented with recurrent liver abscesses in which the inciting object was a toothpick - it led to fistula formation between the pyloroduodenal junction of the stomach and the portal vein, leading to hepatic seeding. [3]
It is also not uncommon for liver abscesses to have dual origins - both amoeba and bacteria. In an Indian study, mixed abscesses were reported in 37.3 per cent of all cases. Anaerobic bacteria, ostensibly from the large bowel (a haven for microbes), were the most common in these cases. Fusobacterium and Peptococcus species accounted for 27.9 per cent, while Prevotella species, 26.4 per cent. [9]
Clinical Presentations:
Liver abscesses are also different from hepatocellular carcinomas in terms of clinical presentation. [1]-[3] are all case reports where patients present with a certain constellation of symptoms and signs. The most predominant of which are high fever, right upper quadrant pain (consistent with the anatomical location of the liver, as well as the gallbladder; as elucidated afore, acute cholangitis and Mirizzi Syndrome can be inciting events of liver abscess formation), malaise, profuse sweating (where amoebic liver abscess patients get hit the worst in the afternoon and evening [1]) and chills. Hepatocellular carcinoma presents with constitutional symptoms. In many cases, right upper quadrant pain is absent since pain is only detected once the tumour invades and extravasates from the hepatic capsule. Furthermore, the disease presents frequently with cirrhosis, where stigmata of chronic liver disease are seen, exemplified by Dupuytren's contracture (more associated with alcoholic liver disease), bruises (coauglopathy), caput medusa and leuconychia (hypoalbuminaemia). [12] These stigmata are absent in liver abscesses since most cases have an acute onset and there is no permanent impairment in liver function.
Pathological specimen of a section of the liver containing a hepatocellular carcinoma on the left (whitish, with irregular contours) (extracted from: https://basicmedicalkey.com/wp-content/uploads/2017/04/image02372-2.jpeg)
CT plus contrast (portal venous phase) of the abdomen indicative of hepatocellular carcinoma. You might be wondering where it is since there is no distinct lesion observed. Well, you would be mistaken if you thought there was only one. The entire liver was wrecked. The carcinoma is diffuse, as indicated by the heterogeneity in tissue density throughout the liver parenchyma. The hypodense portions are cancerous tissue due to portal venous washout of the contrast and the cancer is mostly supplied by the hepatic proper artery. (Extracted from Radiopaedia on URL: https://images.radiopaedia.org/images/7000251/2290a6f4f0520219ead55a98ec31b8.jpg)
Diagnostic Tools:
In this section, I would like to focus on the diagnostic modalities we can rely upon when assessing if a hepatic lesion is an abscess. I'm not going into detail regarding the tools we use for hepatocellular carcinomas since they are rather complicated and, upon clinical presentation, they can already be clearly differentiated (unless the patient has some form of recurrent, or chronic liver abscess - possibly secondary to biliary cancer).
When the patient comes in, he or she is likely to be very ill. We have to (1) go for the vital signs first to determine the patient's general health status, and (2) be wary of septic shock, which is especially important in visceral abscesses due to the possible indication that the patient has septicaemia (microbes in blood). As liver abscesses might indicate an extension of neighbouring disease, haematogenous dissemination is not a remote possibility. To serve these aims, we need the following information:
Body Temperature - which is frequently in the 38-40 degrees Celsius zone;
Pulse Oximetry (oxygen saturation);
Reduced urinary output;
Blood pressure (the most concerning feature is not hypertension, but hypotension since it indicates septic shock);
Heart Rate;
Respiratory Rate;
Glasgow Coma Scale (assessment of level of consciousness since the patient might be too ill or fatigued, indicative of poorer prognosis).
When performing physical examination, due to the constellation of symptoms in liver abscesses, it is advised to carry out both general and abdominal examinations. If hypotensive, as mentioned in previous articles, the patient is likely to present with decreased skin turgor, prolonged capillary refill time (longer than 2 seconds) and reduced blood pressure.
Precautions should be carried out to avoid transmission of disease. I know a visceral infection may sound harmless to the person not experiencing it, but healthcare workers have to appreciate that for visceral abscesses to be formed, there is usually a primary source and the microbe have more ways of spreading. This is particularly concerning in the hospital since other patients, especially immunocompromised ones, may be afflicted by it. For example, Klebsiella pneumoniae is spread through person-person contact (not through air though) and gloves should be used when handling the patient's excretions and used products. [13]
In terms of abdominal examination, there are, as mentioned no stigmata of chronic liver disease. However, abdominal tenderness (localised at the RUQ) and referred pain over the ipsilateral shoulder (due to irritation of the phrenic nerve) are common. Hepatomegaly can also be found. Due to the multiple pathophysiological possibilities of liver abscesses, other signs and symptoms may be present. For instance, if the patient also has acute cholangitis, note the Charcot Triad: jaundice, abdominal pain (RUQ) and fever (Reynold's Pentad, indicative of severe disease, includes hypotension and altered mental state).
Basic Blood Tests
In service of the second aim mentioned above, we have to carry out tests in addition to routine blood tests.
Full Blood Count (especially check for signs of anaemia, leucocytosis and thrombocytopenia - we don't want to delay any treatment and be confounded about the patient's diagnosis);
Clotting Profile (impaired clotting function may be related to septic shock and disseminated intravascular coagulation, where the latter is a likely possibility from the former if it is left untreated);
Liver Function Tests (very important - the normal pattern is elevation in both AST and ALT, where the DeRitis Ratio [AST/ALT] remains unchanged; elevated ALP and total bilirubin);
Renal Function Test;
ESR & CRP (both of which are inflammatory markers);
Urea and Electrolytes (where there are increased levels of urea and lactate);
Group & Save and Crossmatching (crucial for any possible transfusion, especially when the patient develops septic shock).
Microbiological Testing
This takes into account the fact that there are two possible types of aetiologies - amoeba and bacteria. Both should be tested since the treatment administered depends on the aetiology of the disease. Blood cultures can be done. Moreover, to test for amoebiasis, anti-amoebic antibody testing is recommended. A new diagnostic method involving the Gal/GalNAc lectin antigen of amoeba (a surface molecule in Entamoeba histolytica) was also reported. [1]
Ultrasound
This is very useful - I know what everyone says about it. Difficult to operate, dirty (the gel is actually worse than you originally think) and difficult to read...However, when it comes to the liver and kidneys, before we go to vast lengths to put contrast in and visualise the abdominal and genitourinary systems with sophisticated CT, ultrasound is recommended since it does not entail the use of any radiation and no contrast is required. Remember that for CT, the contrast medium is iodine-based which can lead to side effects such as hepatotoxicity, acute kidney injury and pulmonary fibrosis (stemming from autoimmune pneumonitis). Moreover, ultrasound and CT do not differ too much in terms of diagnostic accuracy. Figures stand at respectively 85 and 97 per cent. [14] With regard to resource allocation and availability, ultrasound remains the preferred first-line modality.
The key finding is a (yes, usually there is only a single lesion in the liver - 59 per cent of the time as asserted by a study [15]) hypoechoic, well-circumscribed lesion in the liver. The localisation of the abscess remains an interesting issue. The figure of 35 per cent has been suggested as the prevalence of lesions found in the right lobe [1] but ultimately, this depends on the route of transmission. If it is a spillover reaction, due to the proximity between the duodenum (assuming that it's a duodenal ulcer) and the liver, the left lobe is easier to be affected. If the portal vein is used, due to the distribution of blood within the liver, the right lobe is preferentially affected. Hence, it ultimately boils down to the pathway utilised, not luck.
Diagram showing the portal vein and its drainage pattern - note that the portal vein is divided into the left and right portal veins at the porta hepatis, where the former supplies Couinaud segments II, III and IV. The latter supplies segments VIII and X, moving on to VII and VI. This diagram is extracted from Gray's Anatomy via Radiopaedia.
This diagram illustrates the close proximity between the liver and the duodenum, so that any spillover of inflammation is quite likely to affect the former. It is also note a remote possibility that acute cholangitis leads to liver abscess formation, judging by the short distance between the common bile duct and the intrahepatic ducts. This diagram is extracted from: https://childrensgimd.com/wp-content/gallery/digestive-system/liver-gall-bladder-pancreas.jpg).
This is an ultrasound scan showing an elliptic, well-circumscribed, hypoechoic lesion in the liver. This scan is extracted from Radiopaedia.
Computed Tomography
The wonders of the world are usually derived from cross-sectional imaging. Once you master CT and MRI, there is nothing structurally that one cannot detect - selecting the right modality is ultimately a tug-war between diagnostic accuracy, preference (not personal preference; I'm referring to the preference expressed by local guidelines such as NICE) and resource availability. CT is used as a second-line modality in cases of unequivocal results on ultrasound or diagnostic dilemma, where the symptoms and signs are confusing.
According to a study published back in 2006 [16], abscesses ranged from one to fourteen centimetres in diameter, where the mean diameter was found to be at three centimetres. There is central hypodensity, accompanied by a hyperdense rim. Arterial rim enhancement is found to be the most predictive finding of liver abscess which differentiates it from liver metastases. [17] Many studies have also been performed to compare the differences in radiological findings on CT between Klebsiella-induced and non-Klebsiella-induced liver abscesses. One published in 2011 showed that Klebsiella-induced liver abscesses were more likely to be unilobar in involvement and multiloculated (basically meaning the lesion has multiple counterparts divided by granulation tissue). They were also more likely to exist as single entities rather than disseminated and multiple. [18]
CT (plus contrast, portal venous phase) Abdomen showing a large pyogenic liver abscess where there is central hypodensity, surrounded by relatively hyperdense peripheral rim. Due to the presence of multiple locules, Klebsiella pneumoniae is likely to be the causative organism. (Extracted from Wikipedia).
CT Abdomen (contrast-enhanced, portal venous phase) where there are numerous ring-enhancing lesions scattered in the liver parenchyma, consistent with pyogenic liver abscess formation. The microbe cultured is Klebsiella pneumoniae. Moreover, multiple abscess formation is more commonly observed in intravenous drug users, due to haematogenous seeding of bacteria. At the same time, we should be open to more microbial possibilities in these patients, particularly members of the skin flora such as Staphylococcus aureus. (Extracted from Cureus, on URL: https://assets.cureus.com/uploads/figure/file/98395/68f97c804beb11ea94c6cdfc1732a117-Fig-1b.jpg)
CT Scan showing large liver abscess with air-fluid level and pneumoperitoneum (air in the peritoneal cavity). This scan is extracted from: https://www.researchgate.net/figure/Computed-tomography-showing-a-gas-containing-liver-abscess-with-an-air-fluid-level_fig2_23233611.
Treatment Modalities & Prognosis:
Although liver abscesses are traditionally associated with high mortality due to the severe risk of septicaemia and septic shock, the in-hospital mortality rate was found to be 5.7 per cent. [19] It is encouraging since we know that prompt treatment and correct diagnosis are conducive to better outcomes.
In these cases, the most direct form of treatment is antibiotic use. Note the difficulty of antibiotic penetration into abscesses due to the presence of thick walls formed from granulation tissue. However, it all boils down to using the right drugs. For amoebiasis, metronidazole is recommended as the first-line therapy. The recommended duration of therapy is 10 days. But then, things may not be as easy as they seem. This applies especially to elderly patients or those who are immunocompromised (e.g. HIV, Diabetes Mellitus and having received organ transplantation, thus on immunosuppression) since there is a greater risk of complicated infections. Abscess drainage in complicated, refractory cases is recommended. [20] There are mainly two modes of drainage - (a) percutaneous and (b) laparoscopic. The success rate of surgical drainage was found to be 91.5 per cent. [21] For pyogenic liver abscesses, drugs of choice are carbapenem (dealing with ESBL-producing Klebsiella pneumoniae), fluoroquinolones, and third to fourth-generation cephalosporins. Treatment is divided into two phases to ensure high treatment efficacy and optimal penetration of the lesion: (1) intravenous therapy, which can last for 3 weeks, followed by (2) oral therapy which lasts for 1-2 months. It was also found, however, that when the intravenous therapy was shortened to 2-3 weeks, followed by 1-2 weeks of oral therapy, the mortality rate was below 5 per cent. [22]
Concluding Remarks:
Needless to say, when a 'bruise' starts appearing on the liver, we start thinking of certain possibilities. These include hepatocellular carcinoma and liver abscesses. However, this all boils down to the corresponding clinical picture, as well as associated risk factors. If a patient is immunocompromised and indulges in intravenous drug use, liver abscesses are more likely. If a patient indulges in the magic of alcohol (like consuming more than 1 bottle of whisky every day) and his parents are taking anti-Hepatitis B drugs, it is more likely to be hepatocellular carcinoma.
Liver abscesses may be an under-researched area as compared to chronic liver disease, but it doesn't make them less important. In the clinical setting, not raising suspicion of liver abscesses when one ought to can cost lives.
*The cover image is extracted from Radiopaedia on URL: https://radiopaedia.org/cases/amoebic-liver-abscess?lang=gb.
References and Further Reading:
[1] Torre A, Kershenobich D. Amebic Liver Abscess. Annals of Hepatology 2002; 1(1), 45-47.
[2] Chen TC, Chou LT, Huang CC, Lai AB, Wang JH. Isolated tuberculous liver abscess in an immunocompetent adult patient: A case report and literature review. J Microbiol Immunol Infect. 2016;49(3):455-458. doi:10.1016/j.jmii.2013.09.003.
[3] Martin S, Petraszko A, Tandon Y. A case of liver abscesses and porto-enteric fistula caused by an ingested toothpick: A review of the distinctive clinical and imaging features. Radiol Case Rep. 2020;15(3):273-276. doi:10.1016/j.radcr.2019.12.007.
[4] Pentecost G, Kesterson J. Pyogenic liver abscess and endogenous endophthalmitis secondary to Klebsiella pneumoniae. Am J Emerg Med. 2020. doi:10.1016/j.ajem.2020.08.028.
[5] Chaudhuri MR. Primary pulmonary cavitating carcinomas. Thorax. 1973;28(3):354-366. doi:10.1136/thx.28.3.354.
[6] Barrett T, Gill C, Miles B et al. Brain metastasis from squamous cell carcinoma of the head and neck: a review of the literature in the genomic era. Neurosurg Focus. 2018;44(6):E11. doi:10.3171/2018.2.focus17761.
[7] Eira IM, Carvalho R, Carvalho DV, et al. Lung abscess in an immunocompromised patient: clinical presentation and management challenges. BMJ Case Reports CP 2019;12:e230756.
[8] Abbas MT, Khan FY, Muhsin SA, Al-Dehwe B, Abukamar M, Elzouki AN. Epidemiology, Clinical Features and Outcome of Liver Abscess: A single Reference Center Experience in Qatar. Oman Med J. 2014;29(4):260-263. doi:10.5001/omj.2014.69.
[9] Singh A, Banerjee T, Kumar R, Shukla SK. Prevalence of cases of amebic liver abscess in a tertiary care centre in India: A study on risk factors, associated microflora and strain variation of Entamoeba histolytica [published correction appears in PLoS One. 2019 Apr 17;14(4):e0215774]. PLoS One. 2019;14(4):e0214880. Published 2019 Apr 3. doi:10.1371/journal.pone.0214880.
[10] Khim G, Em S, Mo S, Townell N. Liver abscess: diagnostic and management issues found in the low resource setting. Br Med Bull. 2019;132(1):45-52. doi:10.1093/bmb/ldz032.
[11] Shahrul Anuar T, M. Al-Mekhlafi H, Abdul Ghani M et al. Prevalence and Risk Factors Associated with Entamoeba histolytica/dispar/moshkovskii Infection among Three Orang Asli Ethnic Groups in Malaysia. PLoS One. 2012;7(10):e48165. doi:10.1371/journal.pone.0048165.
[12] Forner A, Reig M, Bruix J. Hepatocellular carcinoma. The Lancet. 2018;391(10127):1301-1314. doi:10.1016/s0140-6736(18)30010-2.
[13] Klebsiella pneumoniae in Healthcare Settings | HAI | CDC. CDC. https://www.cdc.gov/hai/organisms/klebsiella/klebsiella.html#:~:text=In%20healthcare%20settings%2C%20Klebsiella%20bacteria,not%20spread%20through%20the%20air. Published 2020. Accessed December 30, 2020.
[14] Bächler P, Baladron M, Menias C et al. Multimodality Imaging of Liver Infections: Differential Diagnosis and Potential Pitfalls. RadioGraphics. 2016;36(4):1001-1023. doi:10.1148/rg.2016150196.
[15] Mohsen A. Liver abscess in adults: ten years experience in a UK centre. QJM. 2002;95(12):797-802. doi:10.1093/qjmed/95.12.797.
[16] Garcia-Eulate R, Hussain N, Heller T et al. CT and MRI of Hepatic Abscess in Patients with Chronic Granulomatous Disease. American Journal of Roentgenology. 2006;187(2):482-490. doi:10.2214/ajr.05.1386.
[17] Oh JG, Choi SY, Lee MH, et al. Differentiation of hepatic abscess from metastasis on contrast-enhanced dynamic computed tomography in patients with a history of extrahepatic malignancy: emphasis on dynamic change of arterial rim enhancement. Abdom Radiol (NY). 2019;44(2):529-538. doi:10.1007/s00261-018-1766-y.
[18] Alsaif H, Venkatesh S, Chan D, Archuleta S. CT Appearance of Pyogenic Liver Abscesses Caused byKlebsiella pneumoniae. Radiology. 2011;260(1):129-138. doi:10.1148/radiol.11101876.
[19] Yoon J, Kim Y, Kim S. Prognosis of liver abscess with no identified organism. BMC Infect Dis. 2019;19(1). doi:10.1186/s12879-019-4131-z.
[20] Kouzu K, Einama T, Nishikawa M et al. Successful surgical drainage with intraoperative ultrasonography for amebic liver abscess refractory to metronidazole and percutaneous drainage: a case report. BMC Surg. 2020;20(1). doi:10.1186/s12893-020-00776-x.
[21] Herman P, Pugliese V, Montagnini AL, et al. Pyogenic liver abscess: the role of surgical treatment. Int Surg. 1997;82(1):98-101.
[22] Lübbert C, Wiegand J, Karlas T. Therapy of Liver Abscesses. Viszeralmedizin. 2014;30(5):334-341. doi:10.1159/000366579.