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Review
, 8 (1), 101-125

Unexpected Hosts: Imaging Parasitic Diseases

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Review

Unexpected Hosts: Imaging Parasitic Diseases

Pablo Rodríguez Carnero et al. Insights Imaging.

Abstract

Radiologists seldom encounter parasitic diseases in their daily practice in most of Europe, although the incidence of these diseases is increasing due to migration and tourism from/to endemic areas. Moreover, some parasitic diseases are still endemic in certain European regions, and immunocompromised individuals also pose a higher risk of developing these conditions. This article reviews and summarises the imaging findings of some of the most important and frequent human parasitic diseases, including information about the parasite's life cycle, pathophysiology, clinical findings, diagnosis, and treatment. We include malaria, amoebiasis, toxoplasmosis, trypanosomiasis, leishmaniasis, echinococcosis, cysticercosis, clonorchiasis, schistosomiasis, fascioliasis, ascariasis, anisakiasis, dracunculiasis, and strongyloidiasis. The aim of this review is to help radiologists when dealing with these diseases or in cases where they are suspected. Teaching Points • Incidence of parasitic diseases is increasing due to migratory movements and travelling. • Some parasitic diseases are still endemic in certain regions in Europe. • Parasitic diseases can have complex life cycles often involving different hosts. • Prompt diagnosis and treatment is essential for patient management in parasitic diseases. • Radiologists should be able to recognise and suspect the most relevant parasitic diseases.

Keywords: Magnetic resonance imaging; Multidetector computed tomography; Parasitic diseases; Radiology; Ultrasound.

Figures

Fig. 1
Fig. 1
32-year-old patient, recently travelling from Cameroon and with previous history of malaria, presenting with fever, chills, generalised abdominal pain, and myalgia. The image of an abdominal US scan depicts splenomegaly of 17 cm. Plasmodium falciparum was detected in blood exams (the parasite was seen in thick blood smears, and antigens were also positive)
Fig. 2
Fig. 2
Amoebic liver abscess. a Axial US image shows a rounded, well-defined hypoechoic lesion with thick walls, located in the right hepatic lobe (arrows). Note the posterior acoustic enhancement that prompts a partially cystic nature. b Axial image of a contrast-enhanced CT from the same patient as in figure a, showing a large cystic mass with solid walls in the right hepatic lobe. Note the enhanced thickened wall of the lesion and perilesional oedema (arrows). The patient had positive serology for E. histolytica (IgG antibodies), and amoebic cysts were found in the faeces. The patient was treated successfully with amoebicidal drugs with complete resolution of the liver abscess
Fig. 3
Fig. 3
Intracranial toxoplasmosis in a 45-year-old patient with AIDS. a. Contrast-enhanced CT displays a hypoattenuating lesion with ring-enhancement in the right hemisphere of the cerebellum (arrow). b and c Axial fluid-attenuated inversion recovery MR images showing multiple brain lesions predominantly located in the grey-white matter junction, with mild mass-effect and some of them with surrounding oedema (arrows). d Gadolinium-enhanced axial T1-weighted MR image, the lesions (arrows) show ring-enhancement and a small eccentric nodule inside, the “asymmetric target sign,” which is suggestive of toxoplasmosis
Fig. 4
Fig. 4
a Barium enema images of a 42-year-old patient native to Bolivia, it shows megacolon fundamentally at the expense of sigmoid colon (s). Chagas disease was confirmed by serologic testing. b and c Cardiac chronic Chagas disease. 50-year-old male from Bolivia. Cardiac MR delayed contrast-enhanced sequence with four-chamber view (b) and two-chamber short axis view (c); some areas of delayed transmural enhancement can be appreciated in the left ventricle (arrows) with a non-coronary territory distribution, indicating myocardial fibrosis or necrosis. Note the basal inferolateral and apical locations, the most frequently affected areas in cardiac chronic Chagas affection
Fig. 5
Fig. 5
Visceral leishmaniasis. 52-year-old patient native to Peru, presenting with fever, weight loss, and pancytopenia. Serological exams confirmed leishmaniasis. a Sagittal US image shows splenomegaly. b Contrast-enhanced CT image shows hepatosplenomegaly
Fig. 6
Fig. 6
Hepatic echinococcal cysts. a Type I cyst (WHO CE 1). Contrast-enhanced CT image of a unilocular echinococcal cyst in the right hepatic lobe, note the thicker anterior wall (asterisk). b Type II cyst (WHO CE 2). Contrast-enhanced CT image of a multilocular echinococcal cyst in the right hepatic lobe containing multiple daughter cysts in the periphery and mimicking a “rosette” (arrows). c. Type II cyst with contained ruptured (WHO CE 3). Axial US image shows floating membranes (“water-lily sign”) inside a cyst, consistent with rupture of the endocyst or daughter cysts. d Type III cyst (WHO CE 5). Fragment of an abdominal radiograph that incidentally showed a calcified hepatic hydatid cyst (arrow)
Fig. 7
Fig. 7
Echinococcosis. a Chest radiograph. There is a cystic lesion in the right lower lobe (arrow) with an air-fluid level corresponding to a pulmonary hydatid cyst communicated with the airway. The patient had expectoration of cyst components. b CT image of the same patient as in figure a, showing the hydatid cyst communicating with a subsegmental bronchus (arrow). c Contrast-enhanced CT image showing a complex lesion in the left kidney (arrows) containing dense material and membranes, and having a partially calcified wall, it proved to be a renal hydatid cyst surgically and histopathologically. d Multiple cystic lesions in the liver and peritoneum, some with partially calcified walls, which also proved to be hydatid disease surgically and histopathologically (arrowheads). e T2-weighted double inversion recovery MR image of the heart. It shows a hyperintense intramyocardial lesion in the posterobasal segment of the left ventricle that proved to be a hydatid cyst surgically and histopathologically (white arrow) f Gadolinium-enhanced fat-saturated T1-weighted double inversion recovery MR image of the heart, from the same patient as in e. It shows subtle peripheral enhancement of the lesion intramyocardial lesion (arrow), and pericardial effusion (asterisk) with pericardial enhancement (arrowheads) indicating pericarditis
Fig. 8
Fig. 8
Neurocysticercosis. a Vesicular stage. Gadolinium-enhanced axial T1-weighted MR image. Cystic lesion in the right ventricular atrium (arrow) whose content similar to the CSF; inside there is an eccentric dot with high signal intensity representing the protoscolex (“cyst with dot” sign). There is no enhancement as there is no or scant host reaction in this stage. b Colloidal vesicular stage. Axial fluid-attenuated inversion recovery MR image. There are several lesions located in the subarachnoid space and corticomedullary junction and one in the left thalamus, they have a content, which is denser than the CSF (is has a higher signal intensity) and are surrounded by marked oedema. c Colloidal vesicular stage. Gadolinium-enhanced axial T1-weighted MR image of the same patient as in c. The lesions show ring enhancement. d Calcified nodular phase. CT image showing multiple calcified lesions dispersed in the brain parenchyma mostly in the corticomedullary junction and subarachnoid space, and some of them in the right basal ganglia. They represent calcified granulomata in dead neurocysticercosis
Fig. 9
Fig. 9
Spinal neurocysticercosis. a Axial T2-weighted MR image, showing a cystic lesion in the subarachnoid space of the dural sac in the sacrum. There is a dot with lower signal intensity inside the cyst representing the protoscolex (“cyst with dot” sign) in a vesicular stage. b Coronal T2-weighted MR image of the same patient as in a. The intradural cyst (arrows) has a signal intensity similar to the CSF, note also the thin walls and the high signal intensity protoscolex inside the cyst, these are typical findings of a vesicular stage neurocysticercosis
Fig. 10
Fig. 10
Clonorchiasis in a 50-year-old woman native to China. a. Axial US image shows mild choledocal dilatation with a non-obstructive bile stone. b. Contrast-enhanced CT image shows dilatation of intrahepatic bile ducts in the right lobe, with periductal enhancement and intraluminal solid contents (debris, parasites), including bile stones and casts (arrows). Note the hyperaemia of the surrounding hepatic parenchyma (asterisk), secondary to acute inflammatory changes
Fig. 11
Fig. 11
Intestinal schistosomiasis. a. US-Doppler axial image from a Filipino patient with chronic infection by S. japonicum. Note also the stigmata of chronic liver disease (caudate and left lobes hypertrophy, heterogeneous parenchyma and irregular surface). Periportal fibrosis appears as echogenic cuffing around portal vessels (arrows), note left portal vein (asterisk). Characteristic fibrotic septa are seen perpendicular to the surface (arrowheads). b. Unenhanced CT image with iodinated oral contrast from the same patient as in figure a. It shows fibrosis with calcified septa (“turtle back” appearance) in the right liver lobe (arrows). Note also the imaging findings consistent with chronic liver disease (atrophy of the right liver lobe with hypertrophy of the left and caudate lobes). c. A month later the patient from figures a and b came to the ER with acute abdominal pain; unenhanced CT with iodinated oral contrast was performed, showing a perforated duodenal ulcer with oral contrast leakage (arrowhead), microbiological and pathological exams probed that it was a duodenal ulcer caused by S. japonicum. d. Gadolinium-enhanced axial T1-weighted MR image with fat suppression of a patient from Guinea-Conakry with chronic S. mansoni infection, it shows almost complete atrophy of the left portal vein and periportal fibrosis, seen as a hypointense periportal cuffing (arrow)
Fig. 12
Fig. 12
Genitourinary schitosomiasis. a. Pelvis radiograph of a patient born in Ivory Coast, showing a complete calcification of the urinary bladder walls (arrows), pathognomonic of chronic urinary schistosomiasis. b. Pelvis radiograph from an iv urography in a patient born in Mali; there is wall calcification of both distal ureters (white arrows) and anterior urinary bladder wall (black arrow), and also calcification of the seminal vesicles (arrowheads), consistent with chronic schistosomiasis. Cystoscopy was performed in both patients revealing characteristic urothelial lesions. Biopsies showed schistosoma eggs
Fig. 13
Fig. 13
Fascioliasis. 42-year-old woman with history of long-term fever. a-b Axial and coronal images of contrast enhanced-CT shows multiple subcapsular and confluent lesions in right hepatic lobe (arrows). Some of the lesions have a tubular shape. c. Contrast enhanced-CT image of the same patient 3 weeks later; the lesions have converged forming a greater ill-defined lesion with central areas compatible with necrosis/abscess (arrows). The patient presented with eosinophilia and positive serology for fasciola and was treated with antiparasitic drugs. d. Axial T1-weighted MR image without contrast a month later, demonstrating improvement of the hepatic affection, only residual tubular and pseudonodular lesions of low signal intensity remain (arrows)
Fig. 14
Fig. 14
Ascariasis. a. Barium fluoroscopic study of a 24-year-old woman from Ecuador with previous history of ascariasis and presenting with abdominal pain, diarrhoea, and anaemia. The study shows a worm inside a jejunal loop (arrows). The faeces examination revealed ascaris eggs and the patient was successfully treated with mebendazole. Note that the head (blunt) of the worm points proximally (arrowhead), as is usual in this parasite b. Barium fluoroscopic study of a 37-year-old male from Ecuador presenting with intermittent episodes of right lower quadrant pain, mild vomiting, diarrhoea, and fever. Stool parasitic study revealed ascaris eggs. The barium examination shows intestinal worms compatible with ascaris, note that the shown worm has swallowed barium contrast (arrows). c and d. 29-year-old woman from Ecuador with previous surgery of cholecystectomy, presenting with biliary vomiting, right upper quadrant pain, and elevated liver and cholestatic enzymes. The US examination in C displayed a long echogenic filling defect without acoustic shadowing inside the common bile duct (CBD) (arrows), with other adjacent smaller filling defects compatible with gallstones and/or debris. The ERCP in B shows a worm inside the common bile duct whose head is introduced in the right hepatic duct (arrows). The living worm was extracted with ERCP and proved to be an ascaris lumbricoides
Fig. 15
Fig. 15
Strongyloidiasis. a. Chest CT image of an inmunocompromised 45-year-old patient presenting with a severe hyperinfection syndrome. The scan shows bilateral widespread pulmonary infiltrates and pleural effusion (asterisks). b. Contrast-enhanced CT image from the same patient as in a. The patient’s condition worsened after a week and the CT scan showed wall oedema in several bowel loops (arrowheads). Strongyolides larvae were found in the faeces and in bronchial aspirate
Fig. 16
Fig. 16
Dracunculiasis. a and b Plain radiographs of the left knee and leg of a patient coming from Mali shows “worm-like” calcifications in the soft tissues caused by dead calcified worms. c. CT image of the left leg of the same patient as in a and b, confirms the dead calcified worms in the subcutaneous tissue and muscles of the left lower limb
Fig. 17
Fig. 17
Anisakiasis. 44-year-old woman presenting with severe abdominal pain four days after having eaten raw fish. a. US scan axial image, concentric wall thickening in several jejunal and ileal loops and ascites (arrow) were seen. Note the irregularity of the lumen surface due to oedema of Kerckring’s folds (“the corn” sign) (arrowheads). b. Contrast-enhanced CT of the same patient as in a shows diffuse concentric wall thickening of a jejunal loop (arrows) and ascites (asterisk). The patient had positive test results for specific IgE anti-anisakidae antibodies

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