The role of radiological imaging in the identification of abdominal parasitoses

Full article

https://doi.org/10.53453/ms.2023.11.8

The role of radiological imaging in the identification of abdominal

parasitoses

Milda Sondaitė

, Miglė Viliušytė

, Algidas Basevičius

Lithuanian University of Health Sciences, Faculty of medicine, Kaunas, Lithuania

Lithuanian University of Health Sciences, Department of Radiology, Kaunas, Lithuania

Abstract

Background. Various parasites are found in the human body. Some of them infect the human body and form a

symbiotic relationship with it. Other parasites cause serious and even fatal complications. The most frequent

abdominal parasites include Echinococcus spp., liver flukes, and Entamoeba histolytica.

Aim: to review information on current radiological imaging possibilities to identificate abdominal parasitoses as

reported in the literature.

Methods. Literature sources were selected from PubMed medical database using these keywords: radiological

imaging, abdominal parasitosis, echinococcus granulosus, echinococcus alveolaris, liver flukes, entamoeba

hystolitica.

Results. Ultrasonography, computed tomography, and magnetic resonance imaging (MRI) are the most often

utilized imaging technologies in diagnosis. Furthermore, in the majority of instances, serological testing is

required to confirm the diagnosis.

Conclusions. Parasitic diseases are highly prevalent worldwide and cause severe infections or death. Radiological

diagnostic tests and accessible serological testing are crucial in the identification of parasitic diseases.

Keywords: radiological imaging, abdominal parasitosis, echinococcus granulosus, echinococcus alveolaris, liver

flukes, entamoeba hystolitica.

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

Medical Sciences 2023 Vol. 11 (6), p. 61-73, https://doi.org/10.53453/ms.2023.11.8

1. Introduction

Parasitic diseases are among the most severe and

widespread infections in the world, causing millions

of morbidities and deaths each year. Although

parasitosis can affect practically any organ in the

human body, the majority of infections result in liver

damage. Parasites in the liver cause a wide range of

diseases and mortality by inducing recurrent

cholangitis, cirrhosis, liver failure and cancer. The

most frequent orally transmitted parasites that

invade the liver following mucosal penetration or by

portal-venous blood flow include Echinococcus

spp., liver flukes, and Entamoeba histolytica.

However, the proper identification of a hepatic

parasite is frequently delayed due to clinicians

unfamiliarity with the corresponding organi-

sms [1,2].

The liver has a unique feature of immune status, that

it can promote tolerance rather than immunity. This

function can be used by the parasites to avoid host

immunity [2]. Hepatic immune tolerance is caused

by a unique combination of anatomical and

histological properties of the liver. The liver

receives practically all of its blood supply directly

from the portal system, making it the first organ to

be exposed to gut-derived compounds such as

innocuous bacterial metabolites and nutrients [3].

The liver provides the most scavenger cells in the

body, primarily Kupffer cells (KCs), liver-resident

macrophages, and liver sinusoidal endothelial cells

(LSECs). KCs eliminate larger blood-borne

particles via phagocytosis, whereas LSECs remove

small particles (< 200 μm) and macromolecules via

receptor-mediated endocytosis. Both of these cell

types are essential for the liver's barrier effectiveness

and blood filtering ability. Many of the eliminated

elements are potential inflammatory inducers, but

their removal by liver cells is often not associated

with inflammatory immune responses. Instead,

immunological responses are frequently repressed

by multiple mechanisms, known as immune

tolerance in the liver. Although liver tolerance is

presumably an essential response to its frequent

exposure to a variety of food and microbial antigens,

it is one of the mechanisms that enable parasite

invasion in liver cells [3,4].

2. Methods

The PubMed database was used for the literature

review. Publications were collected in June and July

of 2023. Keywords used: "radiological imaging",

"abdominal parasitosis", "echinococcus

granulosus", "echinococcus alveolaris", "liver

flukes", "entamoeba hystolitica".

3. Results

3.1. Echinococcus spp.

3.1.1 Echinococcus granulosus

Cystic Echinococcosis (CE) or hydatid disease (HD)

is triggered by infestation with metacestodes (larval

phase) of Echinococcus granulosus tapeworm.

Human echinococcosis is a zoonotic secondary

illness [5–10]. E. granulosus is a common parasite

in certain regions of the globe, and it can be found

on every continent except Antarctica. Consequently,

CE impacts a significant number of indivi-

duals [5,10].

When carnivores consume the entrails of

contaminated intermediate hosts, such as pigs or

sheep, they frequently become infected with

Echinococcus granulosus. The gravid proglottids,

which are eventually eliminated in the infected

animal's feces, are released by the parasite once it

has entered the small intestine and adheres rigidly to

the mucosa. Each proglottid contains a number of

eggs that can be consumed by intermediate hosts. As

seen in sheep that become infected after grazing on

grass contaminated with dog excrement containing

the eggs, the eggs develop into cysts and offspring

cysts in these hosts. Handling or eating infected

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

sheep's meat or organs carries no risk of human

infection [5]. Humans are accidental intermediate

hosts who become infected either by direct contact

with a dog contaminated with egg-bearing

excrement or through ingestion of contaminated

water, food, or soil [5]. The asymptomatic

incubation phase, during which ingested eggs

release oncospheres that are capable of penetrating

the human intestinal wall, is the first stage of

infection. These oncospheres can access the liver,

lungs, and other organs by penetrating the portal

venous system. Then the oncospheres start to

develop cysts, which can have a diameter between

one and fifteen centimeters. Cysts are most

commonly found in the liver (70 %) or lungs (20 %),

10 % of cysts, however, can be discovered anywhere

in the body, including the spleen (6 %), heart (2 %),

kidney (2 %), and brain (2 %) [5,7,8,11] - with the

exception of hair, teeth, and fingernails, it can affect

nearly any organ in the body [8].

Hydatid cysts may be unintentionally found during

radiologic workup. Because of the gradual growth

and development of cysts, as well as the immune

system's reaction, CE might go undiagnosed for a

long period of time [5,10], because the majority of

cases are asymptomatic for years [11]. In the early

stages of the disease, patients may either be

completely asymptomatic or exhibit vague signs and

symptoms [13]. The symptoms of cystic

echinococcosis differ depending on where the cyst

is located.

The liver is the most affected organ in the body

because it acts as the first filter for portal venous

blood and obstructs roughly 75 % of ingested

embryonated eggs. While hydatid cysts of the liver

are often asymptomatic and found incidentally on

medical imaging, they might cause symptoms due to

cyst expansion, which can cause hepatomegaly or

the host's inflammatory reactions. Hydatid cyst

infection, biliary duct fistula, and rupture into the

peritoneum or chest are the most common

consequences [10].

Patients with intra-abdominal CE present with

symptoms late in the course of the illness [10].

Depending on their size and location, cysts may

eventually put pressure on surrounding tissues,

causing stomach pain and discomfort [5,9,10].

Despite being a non-malignant ailment, the

manifestation of hydatid disease can result in

elevated morbidity and mortality rates [7]. Cyst

rupture or leakage can cause immunologic

symptoms because it triggers an immunoglobulin

(Ig)E response, which can cause allergic reactions

characterized by hives, flushing, and swelling of the

mucous membranes. Anaphylactic shock can be

lethal if there is a major rupture [5]. As per the

research conducted by the World Health

Organization in 2010, the fatality rate for human

echinococcosis is 4 %, where the majority of deaths

are caused by anaphylactic shock induced by cyst

rupture [7]. Prompt diagnosis and therapy are

required to avoid potentially fatal complications

such as anaphylactic shock or pressure effects on

essential organs [10,11].

Imaging and serologic testing is used to diagnose

CE. Simple serum studies typically have low

sensitivity associated with undetected

immunological responses, making diagnosis

challenging. About 30–40 % of patients have no

antibodies at all, even in those with circulating

parasite antigens. Low sensitivities of serum liver

enzyme assays make them typically unreliable in

determining the underlying severity of the

infection [5]. Complete blood count tests might be

helpful for these patients because they can have

eosinophilia [5,10,12].

The field of medical imaging holds great

significance in both the identification of a hydatid

disease and determining the extent of its progression

[12]. Depending on the cyst's stage, different

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

imaging results are obtained. In up to 30 % of CE

cases, calcification may be seen on radiographs.

During the CE process, calcification can happen at

any point. The pericyst is where calcifications are

typically deposited. Once a cyst has fully calcified,

the pathogen is considered to be dormant or

dead [5].While chest radiography is widely used as

the main diagnostic tool, it is insufficient for

evaluating the complications and progression of

hydatid disease [8].

The detection of CE is now commonly done through

ultrasound. The precision of ultrasound diagnostics

can go up to 90 %, contingent upon the proficiency

and skill of the user. This method is presently the

preferred choice for screening due to the

convenience and availability of the device, even in

small, remote medical centers. Because of its lack of

radiation, exceptional precision for identification,

distinguishing between ailments, categorization, and

screening to evaluate the pervasiveness of hydatid

cysts in the abdomen, ultrasound scanning is the

preferred option [10]. Ultrasound is not only

valuable for diagnosis but also for tracking post-

treatment progress [5,10]. Due to its potential to

provide comprehensive information about the mass,

including a more accurate assessment of its

dimensions, exterior characteristics, the presence of

a secondary cyst, and other pertinent anomalies in

the area, ultrasound is particularly responsive [12].

Inside the hydatid cyst, an ultrasound can clearly

show the hydatid sand, membranes, daughter cysts,

and vesicles. It has 96 % sensitivity and 98 %

specificity in distinguishing hydatid cyst of the liver

from simple liver cysts [10]. Its inability to

differentiate between hydatid disease and other

conditions is one of its weaknesses [12]. While

ultrasound is a superb means of preliminary

diagnosis, sonography can sometimes fall short due

to various factors such as obesity, excessive

intestinal gas, and past surgical procedures [5].

CT has a sensitivity rate close to 94 % and is

essential for detection [5]. Particular signs include

wall calcification, detached inner layer, and

daughter cysts (a defining characteristic). A CT scan

is still a more accurate examination because it can

confirm the size and location of the lesion as well as

any relation or involvement with neighboring tissue.

If surgical intervention is intended to be used to

ascertain the parenchymal involvement of the cyst

within the tissue, this can be especially helpful

during the preoperative planning stage. CT imaging

is important because it allows for a clear view of

cystic lesions and calcification, which might appear

as a thick, unilocular or multilocular heterogeneous

cyst or the presence of low-density daughter cysts

[12]. Calcifications, daughter cysts, and detached

membranes are all uncommon hydatid cyst features

[7,8]. Observations made through imaging in cases

of cystic echinococcosis vary from cystic formations

to formations that seem to be solid. The cyst may

show up as a fluid collection that is clearly defined.

Often, the endocyst may detach from the pericyst,

leading to the appearance of a membrane that

appears to be floating [9].

Although MRI plays a role in identification, the

main limitation of using this technology is its

exorbitant cost, especially when there is a chance of

reaching the diagnosis using less expensive

ultrasound or CT imaging [12]. While it isn't always

necessary, MRI may offer additional information

not visible on CT [5] - it is more effective at

exhibiting the correlation with neighboring flexible

tissues and contents of the cyst and daughter

cysts [8].

Depending on the growth stage, a hydatid cyst can

manifest in various dimensions and configurations,

resembling both benign and malignant tumors,

thereby presenting diagnostic complexities on

certain occasions. When making a differential

diagnosis for any cystic lesion, keep a hydatid cyst

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

in mind [7,8]. Hydatid liver cysts must be

considered as part of the differential diagnosis as

they can mimic a variety of liver lesions, such as

choledochal cysts, Caroli's disease, heman-

gioendotheliomas, mesenchymal hamartomas,

teratomas. The imaging features of hydatid cysts are

different and critical for diagnosis. Hydatid cysts

that are discovered in unexpected places could be

misdiagnosed, leading to ineffective treatment and

potentially fatal complications [11]. Radiological

imaging can thus only be used to differentiate

hydatid cysts from other infected or malignant

tumors. Hydatid cysts are infrequent, although they

might produce unexpected effects and symptoms in

rare cases [7].

Radiology is critical in both getting an accurate

diagnosis and offering assistance during the

treatment planning phase [8,12].

Figure 1. Echinococcus granulosus (Hydatid disease) cystic lesions viewed in ultrasonogram [13].

Figure 2. Contrast-enhanced computed tomography of the abdomen show unenhanced hypodense mass with well-

defined borders and no internal architecture without septa (a). Contrast-enhanced computed tomography of

abdomen (b) shows liver hydatids with multiple daughter cysts (arrows). Contrast-enhanced computed

tomography of the abdomen shows splenic hydatid cysts (c) well-defined lesions with peripheral wall calcification

and membranes appear as lamellated calcification (arrow head). Complex fluid collection with curvilinear

densities (blue arrow), consistent with detachment of the laminated membranes of the endocyst from the pericyst

of a hepatic hydatid cyst (d) [14]. [13]. The CT scan (e) reveals a patient from Kaunas Clinics with echinococcus

granulosus cysts in the liver.

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

3.2 Echinococcus alveolaris

Echinococcus multilocularis life cycle involves two

separate mammalian organisms, the definitive host

and the natural intermediate host. In the life cycle of

E. multilocularis, foxes are the definitive hosts while

rodents serve as intermediate hosts. The fox releases

the eggs that the adult parasite produces into the

environment, and the cycle is then completed when

the intermediate host digests tainted food. Humans

are either unintentional or atypical intermediate

hosts. The invasion of different organs by

metacestodes, primarily the liver and lungs, causes

severe problems. Alveolar echinococcosis is caused

by cestodes of Echinococcus multilocularis. AE is a

manifestation that can only be observed in the

northern hemisphere [15,16]. Echinococcus

multilocularis metacestodes have the ability to infect

multiple organs in people and exhibit neoplastic-like

growth and infiltration patterns. AE is also referred

to as "worm cancer” - it is easily mistaken for cancer

because it can metastasize to distant organs or

invade nearby ones [16]. Furthermore, because the

condition is uncommon, particularly in non-endemic

locations, diagnosing it can be difficult [15,16].

The illness typically progresses with an

asymptomatic incubation period lasting 5-15 years,

followed by a chronic phase. In more than 33 % of

cases, the condition is identified by chance. The

clinical symptoms displayed depend on the

individual organ affected and the amount of the

invasion. Other abdominal organs are damaged by

the direct invasion or metastatic spread. There have

been reports of invasions of the diaphragm, perirenal

region, abdominal lymph nodes, peritoneum,

mesenteric tissues, spleen, pancreas, adrenal glands,

kidneys, gallbladder, retroperitoneum, abdominal

wall, and stomach. Primary organ involvement

outside of the liver is extremely rare. The lungs are

the organs that are most frequently involved in

secondary AE [15].

The larval stage typically manifests in the liver,

inducing infiltrative mass lesions with numerous

vesicles that range in diameter from submillimeter

to 20 cm [16]. The most common symptoms of liver

invasion are jaundice, pain in the upper abdomen,

exhaustion and weight loss. The transition from

healthy tissue to diseased tissue is indistinct, and the

masses are further characterized by diffuse fibrosis,

calcified foci, and necrotic regions, primarily

located in central zones. The infiltration of the

biliary ducts and vessels, combined with tissue death

at the core of the injury, can result in critical issues

such as bile duct inflammation, abscesses in the

liver, portal vein hypertension, Budd-Chiari

syndrome, biliary cirrhosis, or additional infections,

all of which can increase morbidity or mortality. AE

is extremely harmful to the human body, damaging

the liver in 100 % of cases and causing substantial

damage to hepatic functioning. Lung involvement is

typically discovered by chance. The primary

symptoms include hemoptysis, dyspnea, coughing,

and chest pain [15].

AE is a chronic tumor-like condition that, if

untreated or treated insufficiently, can be fatal. More

than 90 % of patients with untreated or insufficiently

treated AE die within 10 to 15 year [15,16]. Death

can result from problems with the hepatobiliary

system and associated infections, secondary biliary

cirrhosis and related complications, issues caused by

vascular structure involvement, and invasion of

distant organs. Primary involvement beyond the

liver is exceedingly uncommon (1 % of cases), with

direct invasion of other intra-abdominal organs or

secondary spread to more distant organs such as the

brain, lungs, or bones via hematogenous or

lymphatic pathways [15,16]. Multi-organ invasion is

observed in 13 % of cases [15].

While radiologic imaging techniques are important,

the diagnosis must be validated by further support of

histopathologic verification or detection of parasite

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

nucleic acid in the clinical sample. For some years,

conventional imaging modalities such as x-ray,

ultrasonography (US), computed tomography (CT),

and magnetic resonance imaging (MRI) have been

used in the diagnosis, follow-up, and therapy of AE.

New investigations on the diagnosis and follow-up

of the condition using contrast-enhanced

ultrasonography (CEUS), diffusion-weighted

imaging (DWI), magnetic resonance spectroscopy

(MRS), and positron emission tomography-

computed tomography (PET-CT) have recently been

published [15].

Ultrasound is often the chosen imaging modality for

diagnosis and follow-up. It is an appropriate and

efficient imaging approach for detecting AE lesions.

When there are irregular contoured mass lesions, a

mixed heterogeneous echogenic pattern, cystic

necrotic areas, and multiple scattered calcific foci,

the liver is involved. A less typical sonographic

appearance is a hailstorm pattern with several

hyperechogenic solid lesions. This look is thought to

represent early AE lesions. Radiologists in endemic

areas must precisely identify this less common

presenting form, which might be confounded with

venous malformations and other lesions of a similar

character [15].

Figure 3. CT scan (a) reveals a single giant echinococcosis cyst in the liver. CT image (b) shows CE of the

detached inner capsule type: the inner capsule is folded into a floating band symbol after being deflated and

separated. CT image (c) reveals multi-daughter cysts are visible inside the big cyst. The CT image (d) acquired

after intravenous contrast shows two hepatic masses with unclear borders and diffuse hyperdense foci of coarse

calcification [13]. The CT scan (e) reveals a patient from Kaunas Clinics with echinococcus alveolaris cysts in

the liver.

The most effective imaging modality for

demonstrating the distinctive morphologic aspects

of AE lesions in intra-abdominal organs is CT. It is

helpful in determining how the hepatic lesions

interact with the bile ducts and vascular systems. It

is also possible to demonstrate involvement of

extrahepatic organs. AE lesions resemble tumors

and have erratic borders, diverse internal structures,

and numerous, dispersed calcific foci. The affected

liver lobe exhibits atrophy and capsular retraction as

a result of vascular and biliary involvement [15].

The best imaging technique for identifying the

different parts of a parasite lesion and showing

invasion of the vascular and biliary structures is

magnetic resonance imaging (MRI). Since MRI is so

helpful in revealing expansion to nearby organs, it

should be used in preoperative imaging. The typical

MRI finding of AE in the liver is a mass lesion with

infiltrative characteristics, uneven boundaries,

internal heterogeneity, and necrotic regions in the

center. The inner edge of the fibrous zone appears as

a slightly hyperdense signal with localized

invagination forming a peninsula sign and internal

necrosis and liquefaction forming a fluid retention

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

cavity. These exhibit hypo- or isointensity on T1-

weighted images and hypo-, iso-, or hyperintense

signal characteristics on T2-weighted images [15].

Particularly in nonendemic areas, AE may be easily

misdiagnosed by inexperienced doctors as a

metastatic malignant tumor [15,16]. The radiologist

must be knowledgeable about the multimodality

imaging findings of this disease. Ultrasonography

can be used for scanning as well as for the initial

imaging process. Additionally, ultrasound can direct

the interventional techniques. The use of CT and

MRI is essential for making sure the right diagnosis

is made, for organizing surgical procedures, and for

monitoring patients with AE. Radiology plays a

crucial role in assisting the clinician in making an

early diagnosis and selecting the best course of

action [15].

3.3 Liver flukes

Fascioliasis is a parasitic infection of the

hepatobiliary system resulting from digenean

flatworms known as liver flukes, Fasciola hepatica

or Fasciola gigantica. Whenever parasites infiltrate

the liver, the bile ducts may become obstructed. F.

gigantica survives in tropical climates, meanwhile

F. hepatica is mostly found in temperate climate

regions. Mature Fasciola hepatica flukes are around

30 mm by 15 mm in size and are visible with the

human eye. Parasites have two suckers, including a

big one on the ventral side known as the acetabulum,

which allows the fluke to attach itself to the bile duct

wall and stay in position, while the smaller anterior

sucker feeds from the fluid inside. Fasciola

gigantica flatworms, as the name implies, can grow

to be 75 mm long but resemble smaller versions [6]

The worldwide count of Fasciola infection is

believed to be between 2.4 and 17 million, with most

cases going unreported and undiagnosed. Fasciola

hepatica is indigenous to Europe and Asia, with

infrequent occurrences appearing in Northern

Africa, Central and South America, and the Middle

East, as well as the United States and the Caribbean.

Domestic livestock in Asia, the Pacific Islands, and

areas of Northern Africa are infected with Fasciola

gigantica [6,17].

The life cycle began when humans and other fish-

eating mammals, the definitive hosts, transferred

eggs into surroundings via their feces. When the

eggs appear in freshwater, the miracidia infect their

first intermediate host, a freshwater snail, and

change into sporocysts, rediae, and cercariae.

Cercariae elude the snail and infect freshwater fish,

the second intermediate host. The cercariae encyst

as metacercariae in the muscles or under the scales

and can infect humans through the consumption of

undercooked or raw cyprinoid fish products. The

metacercariae enter the human small intestine

uninjured and move until they reach the bile ducts,

where they grow into adult worms and deposit eggs

within 4 weeks. The parasites can live in the human

liver for up to 25 years [6].

The migration of metacercariae induces

parenchymal liver damage, triggering a chain

reaction of inflammatory and immunological

responses that results in acute symptoms. Adult

flukes can clog the bile ducts either entirely or

partially, causing fibrosis, hypertrophy, and

eventually dilatation of the proximal biliary system.

The level of liver damage is often positively

associated with parasite load [17].

The fascioliasis infection has two different phases.

The acute (hepatic) stage typically begins 6 to 12

weeks after ingesting metacercariae from polluted

water. The first symptom is frequently a high

temperature, discomfort in the right upper quadrant,

hepatomegaly, and jaundice. The presence of

peripheral eosinophilia can be detected by a

complete blood count (CBC). Myalgias, urticarial

rash, nausea, anorexia, and diarrhea are common

symptoms. The above symptoms are caused by

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

Fasciola flatworms spreading into the liver

parenchyma and triggering inflammatory and

immune system reactions. Most acute signs

disappear after 6 weeks, and the infection expands

to a chronic stage [17]. However, extrahepatic signs

such as reactive eosinophilic pneumonitis,

vasculitis, myocarditis, cerebral vasculitis and

generalised lymphadenopathy may also be present

[17,18]. Once the flukes are located inside the bile

ducts, the chronic (biliary) phase can remain for up

to a decade. This stage is normally asymptomatic,

although it can cause chronic epigastric and right

upper quadrant pain, nausea, vomiting, diarrhea,

hepatomegaly, and jaundice. Chronic common bile

duct obstruction can cause recurrent jaundice,

cholelithiasis, pancreatitis, and, more dangerously,

ascending cholangitis. Chronic biliary cirrhosis,

sclerosing cholangitis, and even cholangio-

carcinoma can arise from long-term infection and/or

a high parasite load [17,18].

Fascioliasis is a pretty rare illness, but it should be

evaluated in any individual who has abdominal pain,

fever, pruritus, skin rashes, dyspepsia, vomiting,

nausea, transaminitis, and significant peripheral

eosinophilia. If a patient has gone to endemic

locations and their food habits include watercress

intake or eating of raw vegetables washed in

possible contaminated water, suspicion must be

raised [19].

Misdiagnosis and late diagnosis are still common

since the disease is rarely observed in nonendemic

locations and has an unclear clinical appearance.

Hepatobiliary fascioliasis in humans is diagnosed

with direct parasitological tests, indirect

immunological tests, and imaging methods like

ultrasound, CT, and MRI. Radiological tests are

useful in differential diagnosis when liver flukes are

suspected, as is the history of recent travel to the

endemic region [19]. On CT imaging, the leading

sign of hepatic fascioliasis is groups of irregular ill-

defined darkish patches, mainly immediately under

the liver surface, which may progress to inner tissue

and areas around the bile duct. Liver parenchyma

can reveal nodular, tiny, branching, and subcapsular

lesions - migrating parasites leave these wounds.

Necrosis may be visible during intravenous contrast

scanning. It may be possible to see subcapsular

hematoma, capsular thickening, or parenchymal

calcifications as well [15,19].

MRI is preferable to CT imaging because it can

detect a greater number of lesions, also it may show

the disease's typical evolutionary pattern,

representing its life cycle during the early

parenchymal phase, even without the use of a

contrast agent. Furthermore, in fascioliasis, MRI can

provide more detailed information regarding the

development of complications such as hemorrhagic

lesions and abscess formation [9,19].

Sonographic findings in hepatic fascioliasis are

frequently nonspecific. During the parenchymal

phase, they include focal hypoechoic or anechoic

liver lesions and diffuse liver involvement

(heterogeneous echotexture). During the ductal

phase of ultrasound, ductal thickening, intrahepatic

or common bile duct dilatation, and tortuousness are

frequently seen due to intraluminal parasites or the

hemorrhage/inflammatory response they cause. It

might even show a mobile fluke in the gallbladder

or dilated bile ducts [19].

During the biliary stage, ultrasound and

cholangiogram can detect mobile, leaf-like flukes in

the biliary ducts or gallbladder, which are frequently

linked with stones. Abnormal common bile duct

wall thickening, hepatomegaly, splenomegaly,

and/or periportal lymphadenopathy are frequently

observed, particularly during the acute stage [19,20].

However, in recent years, serology has emerged as

the quickest and most efficient method of testing for

fascioliasis. Titers against Fasciola antigens become

positive during the early stages of parasite migration

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

and are detectable for 2 to 4 weeks after initial

immune system activation [20].

Identification of Fasciola hepatica tends to be

challenging, especially in areas where it is not

endemic, because clinical and laboratory signs are

non-specific. Cross-sectional imaging is commonly

used to evaluate probable causes of these confusing

findings. On CT/MRI scans, clusters of twisted

subcapsular lesions with exterior contrast

improvement that extends into the deeper

parenchyma and periportal regions are significant

signs that strongly suggest hepatic fascioliasis.

When relevant radiological indicators are

discovered, the potential of hepatic fascioliasis must

always be considered in a proper clinical context

[19].

Figure 4. Contrast-enhanced CT picture (a) with patchy areas of decreased attenuation migrating from the liver

capsule into deeper parenchyma and periportal regions with modest peripheral contrast enhancement (arrows).

Contrast-enhanced CT-image (b) revealing clusters of hypodense lesions extending from the liver capsule into

deeper parenchyma and periportal regions with slight peripheral contrast enhancement (arrows) [21].

3.4 Entamoeba histolytica

The most prevalent cause of liver abscess in tropical

countries is amebic liver abscess (ALA), a parasite

illness caused by the protozoan Entamoeba

histolytica. Amebic liver abscess (ALA) occurs in 3-

9 % of amebiasis patients, with complications

occurring in 20-40 % of cases and a death incidence

of 2-18 % [22]. After malaria and schistosomiasis, it

is the third leading parasite cause of mortality,

killing approximately 100,000 individuals per year

[23]. Although the number of cases has decreased in

recent years, ALAs remain a major public health

concern in endemic areas [24]. Amoebiasis is most

prevalent in tropical countries with poor sanitation

and lower socio-economic status. This parasite has

been detected to infect around 20 % of the Indian

population. Homosexual men, people with acquired

immunodeficiency syndrome or HIV, cirrhotic

patients, and people living in group homes or mental

health facilities are all at high risk of getting

amoebiasis [24]. Malnutrition and alcohol use are

also risk factors. The majority of ALAs appear with

mild to moderate symptoms and respond to

antiamebic medication within three days. However,

reports from endemic areas show that the disease can

be severe in up to 40% of patients and is not

controllable with the medicine alone. These

abscesses frequently appear rapidly with rupture,

organ failure, and abnormal laboratory results -

additional percutaneous drainage is required.

Amebic liver abscesses have a 1% fatality rate [21].

Infection begins with the intake of E. histolytica

cysts found in water or food that is contaminated.

The vast majority of infected people (90 %) are

asymptomatic carriers, meaning the parasite lives

securely inside the lumen of the colon and excretes

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

cysts in feces to complete the entire life cycle. E.

histolytica breaks the intestinal mucosa and invades

the underlying lamina propria, where it contacts

with host immune cells, producing a raging

proinflammatory cytokine response that causes

tissue damage in 10 % of infected individuals

(symptomatic). It is unknown why a high number of

E. histolytica-colonized people do not develop

invasive illness. The complicated pathogenesis is

thought to be driven by a combination of parasite

virulence factors, host genetics, microbiome, and

immunological responses [21].

Amebic liver abscesses are characterized by right

upper quadrant (RUQ) discomfort and fever.

Symptoms commonly appear subacutely. Less than

one-third of patients had diarrhea, while some may

have had dysentery in the previous months. Jaundice

affects less than 10 % of the affected ones. Patients

returning from an endemic location usually get the

condition within 8-20 weeks, with a 12-week

average. Typically, there is a leukocytosis without

eosinophilia and an increased alkaline phosphatase

that is out of proportion to any increase in

aminotransferases [20,21].

Figure 5. CT scan (a) shows the abscess's non-

enhancing and ragged edge in the absence of a

defined wall (arrows). Pay attention to the dilated

intrahepatic biliary ducts (arrowheads) due to the

mass effect. CT image (b) of an abscess showing a

double-target sign with an inner enhancing ring

(white arrowhead) and an outer hypodense ring

(black arrowhead). CT scan (c) of an abscess. Take

note of the abscess's rim-enhancing wall and the

perilesional halo-like hypodensity, as well as the

focal nodularity in the wall (arrow) reflecting

partially resorbed septa. The CT image (d) displays

a well-defined smooth wall (arrow), although there

is no contrast enhancement. The abscess wall is

surrounded by an ill-defined hypodensity (asterisk).

Take note of the huge cavity formed by the fusion of

several abscesses, as well as the intervening wall

that mimics internal septations [20].

The diagnosis of an amebic liver abscess is obtained

using a combination of imaging features and

serologic testing. A cystic intrahepatic cavity is

visible on imaging, which is usually

indistinguishable from other types of liver

abscesses. Most amoebic liver abscesses are single

lesions, however multiple lesions may occur on

occasion, and they are more commonly detected in

the right lobe than the left. On ultrasound, the lesion

shows as a spherical, well-defined hypoechoic mass.

After healing, the margin of the abscess may calcify

and form a round, thin rim [20,21,23].

ALAs have a non-specific CT appearance that has

been described as a round or oval hypodense lesion

with a thick enhancing wall and peripheral edema.

Although these characteristics are considered

classical, they are suggestive of resolving ALAs.

Wall creation and rim enhancement are late results

discovered as the healing process progresses - this

appearance is likely to suggest modest drug-

responsive illness. These characteristics are rarely

seen in acute abscesses - they are clinically

accompanied with significant symptoms or a

distorted test profile. As a result, it is critical to

distinguish aggressive abscesses from ones with

modest manifestations [22].

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

The typical radiographic features are insufficient to

determine a diagnosis and must be evaluated in

conjunction with serological or serum antigenic

evidence. Although the test may be negative in the

first seven days of illness, most of the patients with

amebic liver abscesses will produce detectable

antibodies to E. histolytica. Antibodies are detected

in 92- 97 % of patients with amebic liver abscesses.

The aspiration of amebic liver abscesses is not

required for diagnosis - trophozoites are only found

in a small percentage of aspirates. Furthermore,

when patients arrive with amebic liver abscesses,

stool microscopy for E. histolytica is commonly

negative, demonstrating that stool microscopy

cannot be relied on to make the correct

diagnosis[21,23].

4. Conclusion

The most common parasitosis that affects abdominal

organs are mainly caused by Echinococcus spp.,

liver flukes and Entamoeba histolytica. Orally

transmitted parasitic infections frequently cause

liver damage, due to the liver's role as the primary

organ to filter portal venous blood. Additionally, it

has the potential to spread to other organs like the

lungs, kidneys, and pancreas via blood flow or

mucosal penetration. Parasitic infections are

typically asymptomatic and diagnosis is often made

by chance. However radiological imaging plays a

crucial role in diagnostics - the most frequently used

imaging methods include ultrasonography,

computed tomography, and MRI. Moreover, in the

vast majority of cases, the diagnosis must be

clarified by serological tests.

References

1. Peters L, Burkert S, Grüner B. Parasites of the

liver – epidemiology, diagnosis and clinical

management in the European context. J Hepatol.

2021 Jul 1;75(1):202–18.

2. Deslyper G, Doherty DG, Carolan JC, Holland C

V. The role of the liver in the migration of parasites

of global significance. Parasit Vectors [Internet].

2019 Nov 8 ;12(1).

3. Brandl K, Kumar V, Eckmann L. Gut-liver axis at

the frontier of host-microbial interactions. Am J

Physiol Gastrointest Liver Physiol [Internet]. 2017

May 1 [cited 2023 Sep 6];312(5):G413–9.

4. Gottwick C, Carambia A, Herkel J. Harnessing

the liver to induce antigen-specific immune

tolerance. Seminars in Immunopathology 2022 44:4

[Internet]. 2022 May 5 ;44(4):475–84.

5. Pakala T, Molina M, Wu GY. Hepatic

Echinococcal Cysts: A Review. J Clin Transl

Hepatol [Internet]. 2016;4(1):39–46.

6. Alshoabi SA, Alkalady AH, Almas KM, Magram

AO, Algaberi AK, Alareqi AA, et al. Hydatid

Disease: A Radiological Pictorial Review of a Great

Neoplasms Mimicker. Diagnostics [Internet]. 2023

Mar 1 ;13(6).

7. Şimşek S, Özmen CA. Unusual imaging

characteristics of thoracic hydatid disease. Radiol

Bras [Internet]. 2022;55(2):128–33.

8. Durhan G, Tan AA, Düzgün SA, Akkaya S,

Arıyürek OM. Radiological manifestations of

thoracic hydatid cysts: pulmonary and

extrapulmonary findings. Insights Imaging

[Internet]. 2020 Dec 1;11(1).

9. Good R, Scherbak D. Fascioliasis. StatPearls

[Internet]. 2023 May 1;

10. Bulakçı M, Kartal MG, Yılmaz S, Yılmaz E,

Yılmaz R, Şahin D, et al. Multimodality imaging in

diagnosis and management of alveolar

echinococcosis: an update. Diagn Interv Radiol

[Internet]. 2016 May 1 ;22(3):247–56.

11. Khalili N, Iranpour P, Khalili N, Haseli S.

Hydatid Disease: A Pictorial Review of Uncommon

Locations. Iran J Med Sci [Internet]. 2023 Mar

1;48(2):118–29.

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

12. Hamed Al Taei T, Ali Al Mail S, Hajjaj Al

Thinayyan A, Alsetrawi A. Renal hydatid cyst: A

case report. Radiol Case Rep [Internet]. 2022 Jun

1;17(6):2063–6.

13. Piccoli L, Tamarozzi F, Cattaneo F, Mariconti

M, Filice C, Bruno A, et al. Long-term Sonographic

and Serological Follow-up of Inactive Echinococcal

Cysts of the Liver: Hints for a “Watch-and-Wait”

Approach. PLoS Negl Trop Dis. 2014;8(8).

14. Mehta P, Prakash M, Khandelwal N.

Radiological manifestations of hydatid disease and

its complications. Trop Parasitol [Internet]. 2016 Jul

1;6(2):103.

15. Mas-Coma S. Epidemiology of fascioliasis in

human endemic areas. J Helminthol [Internet]. 2005

Sep;79(3):207–16.

16. Bayhan Gİ, Batur A, Taylan-Özkan A,

Demirören K, Beyhan YE. A pediatric case of

Fascioliasis with eosinophilic pneumonia. Turk J

Pediatr [Internet]. 2016;58(1):109–12.

17. Govindasamy A, Bhattarai PR, John J. Liver

cystic echinococcosis: a parasitic review. Ther Adv

Infect Dis [Internet]. 2023 Jan 1;10.

18. Šimeková K, Rosoľanka R, Szilágyová M,

Antolová D, Nováková E, Novák M, et al. Alveolar

Echinococcosis of the Liver with a Rare Infiltration

of the Adrenal Gland. Helminthologia [Internet].

2021 Feb 10 ;58(1):100.

19. Preza O, Klapa I, Tsiakalos A, Cokkinos DD,

Chatziioannou A. Fascioliasis: A challenging

differential diagnosis for radiologists. J Radiol Case

Rep [Internet]. 2019 Jan 1;13(1):11.

20. Priyadarshi RN, Sherin L, Kumar R, Anand U,

Kumar P. CT of amebic liver abscess: different

morphological types with different clinical features.

Abdom Radiol (NY) [Internet]. 2021 Sep

1;46(9):4148.

21. Usuda D, Tsuge S, Sakurai R, Kawai K,

Matsubara S, Tanaka R, et al. Amebic liver abscess

by Entamoeba histolytica. World J Clin Cases

[Internet]. 2022 Dec 12 ;10(36):13157.

22. Bansal Y, Maurya V, Tak V, Bohra GK, Kumar

D, Goel AD, et al. Clinical and laboratory profile of

patients with amoebic liver abscess. Trop Parasitol

[Internet]. 2022 Jul 1;12(2):113.

23. 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. PLoS One [Internet]. 2019

Apr 1;14(4).

24. Salahshour F, Tajmalzai A. Imaging findings of

human hepatic fascioliasis: a case report and review

of the literature. J Med Case Rep [Internet]. 2021

Dec 1;15(1).

Journal of Medical Sciences. 23 Nov, 2023 - Volume 11 | Issue 6. Electronic - ISSN: 2345-0592

Journal of MEDICAL SCIENCES

"Medicinos mokslai". ISSN: 2345-0592. Email: info@medicsciences.com.

The role of radiological imaging in the identification of abdominal parasitoses