Ultasound in Parasitic Infestations - SD

Introduction to Ultrasound in Parasitic Infestations

Hi, I am Dr. Nathan Chobe. I'm a practicing ultrasonologist from India Mumbai.

I'm involved in both private practice as well as institutional practice and I'm going to talk today on ultrasound in parasitic infestations.

Some years back we never thought that we would be seeing parasites on ultrasound, but things are quite different today.

Our interest in this field began several years back when we had this young patient was referred to us for suspected varicose veins, but instead of dilated veins, what we saw is multiple hypoechoic channels and within that we saw these linear structures which were continuously dancing.

We now know that these are dilated lymphatics in the inguinal region and this linear structures are nothing but filarial worms and this is now known as the Filarial dance, and since it's a dance, it's quite apt to give it some music and also some disco lights to make it more interesting.

Of course, around that time we had this another young child who came with acute pain in the right hypochondria.

The child was not able to stand or even lie down on the table, and the reason for all this was this roundworm sitting in his common bile duct and in front of our eyes, this round worm decided to walk into the duodenum and the child had miraculously became all right without any pain and walked out from the clinic.

Those days we did not have good recording facilities and we could not record this movement of the round worm into the duodenum.

So this was our first exposure to parasites and after that we have been seeing parasites all over the body.

In fact, biliary system is one of the commonest areas where we see parasites.

Typically, ascaris can be seen either in the gallbladder or in the biliary system, the common bile duct, or sometimes even in the intrahepatic radicals.

The worms could be dead as in this case in the gallbladder or they could be alive as we see in the common bile duct.

Most of the times they are asymptomatic and they pass out through the common bile duct into the duodenum without any cause, but sometimes they can give obstruction and as you can see here, it's quite difficult to remove this round worms from the common bile duct through the sphincter.

As you can see, the surgeon is trying to remove the round worm, but they're trying to slip out of his forceps, so this can be a very difficult task indeed if they cause obstruction in this child.

The round worms decided to go into the intra hepatic radicals.

As you can see, we have intra radical dilatation as well as ascaris within these radicals.

This child presented with symptoms of cholangitis and jaundice.

In fact, parasites as we know can be divided into two groups, the protozoa and the helminths and as we go on through the lecture, we'll see a lot of examples in both these groups.

Different parasites have affinity for different areas of the body and this also will highlight in the talk.

Ascaris Lumbricoides

Okay, ascaris is technically known as ascaris lumbricoides and it's the largest nematode in the body typically, for example, because of a high resolution machine, we can see details of the round worm.

This is a child and we can see the small intestine, we can see the mucosal folds of the intestine within the lumen of the intestine.

We have our friend, the round worm sitting in the center of the round worm.

We have the intestine of the round worm and if you look very carefully within the intestine of the round worm, we have some food particles moving to and fro, so probably by looking at this food particles, we could guess what this child had for his lunch or dinner.

This just goes to say that the resolution of the present machines is so good that we are able to see details of the parasites.

Ascaris lumbricoides has a lifecycle completed in one host, which is the man, and the mode of infection is ingestion of eggs containing second stage infective larvae in food, drink and raw vegetables.

Most of the times these are asymptomatic but they can cause nasty complications.

For example, very often in children they can cause intestinal obstruction.

Here what we see is what is known as a bolus of round worms.

That is a group of round worms which are stuck into the intestine causing obstruction.

This can be seen on ultrasound as well as a plain x-ray where we have a group of roundworms with intestinal obstruction.

The other complication which can be seen in the intestine is intussusception.

A round worm can be a source of intussusception.

As we saw in this child we have intussusception and at surgery the cause of this intussusception was a round worm.

They can go to some odd places.

For example, this round worm has gone into the appendix and has caused acute appendicitis, but this was the most adventurous of them.

This child had a ventriculoperitoneal shunt for hydrocephalus and he presented with severe headache.

When we looked at his abdomen, what had happened was one of the roundworms has had perforated his intestine and gone through the peritoneal cavity, walked into the ventriculoperitoneal shunt, so much so that he had to be removed by a surgical technique.

So as I said, this was probably one of the most adventurous roundworm we have seen.

Liver Fluke (Fasciola Hepatica)

The other parasite, which is typically seen in the biliary system, is liver fluke, which is also known as fasciola hepatica.

This is a child who came to us again with symptoms of cholangitis.

We can see intra biliary dilatation, we can see gallbladder wall thickening and we can see a dilated common bile duct with echogenic areas within it.

If you magnify the common bile duct, we can see linear areas because of the parasite, which is the liver fluke, and that's the endoscopic picture of the parasites and we can see multiple liver flukes within the common bile duct and this is how the liver fluke actually looks like when you examine it under the microscope.

This is also known as common liver fluke or sheep liver fluke and is a parasitic flatworm which infects liver of various mammals including humans.

The drug of choice in the treatment of fascioliasis is triclabendazole, and this child was put on this drug.

This is a very toxic drug and the child requires careful monitoring during the therapy, but after a gap of one month, we can see that the common bile duct is totally clear and there is nothing seen in the lumen.

The technique which we use to see the common bile duct at this time is the X matrix technology, which is a wonderful tool to see the gallbladder and the common bile duct.

Other Intestinal Parasites

We can see other parasites in the intestines.

Typically we can see enterobius, which is known as pin worm.

This is most commonly seen in the region of the cecum and in the region of the appendix.

The other parasite, which we commonly see in this area is the whipworm, which is also known as trichuris.

Of course on ultrasound it can be very difficult to differentiate the different types of parasites, but the final answer comes through the stool examination where we can see the trophozoites or cysts of the parasites within the stool.

Of course, one patient can have multiple parasites or worms at the same time, and this is very often referred to as poly parasitosis and this can be seen on a colonoscopic examination.

Different parasites require different laboratory tests.

Sometimes we might have to do serological tests, sometimes we might have to do skin reaction tests and sometimes we might have to resort to molecular techniques as well.

Hydatid Cyst (Echinococcus Granulosus)

The other parasite, which is very commonly seen in practice, is the hydatid cyst, which is also known as echinococcus granulosus.

The lifecycle of echinococcus granulosus is completed in two hosts.

There's a definitive host, which is the dog or a wolf and an intermediate host, which is the sheep or the man, and the mode of infection is ingestion of food and water contaminated with echinococcus granulosus eggs.

On ultrasound there are three diagnostic features.

One is the hydatid fluid, which is secreted by the endocyst and hydatid sand, which is typically seen in this slide, which is falling down within the hydatid cyst and daughter cysts, which are tiny cystic areas within the cyst.

This is a very classical example of daughter cyst within a hydatid cyst.

The hydatid cyst has three layers, the pericyst, which is a rigid protective layer, an ectocyst, which is an acellular laminated membrane and an endocyst, which is the inner germinal layer.

There are various ways of classifying hydatid disease.

Two popular ways are the WHO classification where we have CE1, CE2, CE3, CE4 and CE5 and the Gharbi classification where we have type one, which is a pure fluid collection type two where we have fluid collection with a split wall type three where we have fluid collection with septae type four, where we have hydatid with heterogeneous echo pattern and type five where we are hydatid cyst with calcified thick walls.

This is an example of type one cyst, which is sonolucent type two cyst with a membrane type three cyst with multiple septae type four cyst, which is heterogeneous type five, which is highly reflective.

The diagnosis of hydatid comes very often after aspirating the hydatid cyst and pointing out towards the scoleces in the fluid.

ELISA test was a popular test done for hydatid disease, but nowadays we also have PCR diagnosis where we can detect antibody to hydatid.

This is very often known as the Casoni test.

Sometimes we can make a diagnosis of hydatid cyst.

Surprisingly, for example, in this patient there was a cystic lesion in the liver.

After aspirating this cyst, we saw the separation of the germinal layer, which led to a diagnosis of a hydatid cyst.

There are various ways of treating hydatid disease and nowadays one of the popular way is PAIR and through the PAIR you can see some daughter cysts coming out.

Now when you remove the hydatid from the liver, it's very important to get the cyst out of the liver and wrap it up in a plastic bag so that there is no peritoneal spillage into the peritoneal cavity and the entire hydatid along with the plastic bag is then removed out of the body.

We can also treat this conservatively either with alcohol or hypertonic saline injections.

Typically hypertonic saline is most popularly used nowadays there are two techniques of injection.

One is what is known as a PAIR technique where you do a percutaneous aspiration injection and reaspiration or a PI technique where you do a percutaneous aspiration and injection.

Cysts can be seen in lot of places.

Here for example, we have a renal hydatid, which is seen in the upper pole of the kidney and these are the classical daughter cysts in the upper pole of the kidney on ultrasound as well as on the CT scan.

This is an example of a splenic hydatid within the spleen we can see a cyst with daughter cysts and that's the left kidney there.

Sometimes we can have extensive cysts for example, in this patient we have a hydatid cyst in the liver, we have a hydatid cyst in the spleen we have a hydatid in the region of the adrenal as well as in the retroperitoneal area behind the bladder.

Sometimes we can see extensive hydatid disease involving almost the entire abdomen from the sternum to the pelvis and in fact, sometimes we wonder whether this disease can affect everything except maybe the nails and the teeth.

Lung is another area where we very often see hydatid and needless to say that a CT scan is very useful in this situation.

This was an interesting case.

We had an opacity in the left lung which on x-ray could have been anything from tubercular granuloma to metastatic deposit.

We did a CT scan and since this lesion was very close to the anterior chest wall, we decided to put in a needle under ultrasound guidance and to our surprise, when this fluid was examined under the microscope, we saw this scolex of hydatid disease, so this was a surprising diagnosis.

Amoebic Liver Abscess

A very close differential diagnosis of hydatid in the liver is amoebic liver abscess, which is commonly seen in these areas.

The liver abscess does not have a classical hydatid sand, nor does it have classical daughter cysts, but it is very common to see septae within amoebic liver abscesses, amoebic liver abscesses caused by entamoeba histolytica.

The lifecycle is again completed in one host the man and the mode of infection is ingestion of cysts through water and vegetables contaminated with infective trophozoites or a direct transfer from cyst carriers.

Liver abscesses caused by entamoeba histolytica has various stages in the liver and various appearances.

It can be a totally unliquefied abscess, it can be a semi liquefied abscess, it can be a liquefied abscess with posterior acoustic enhancement or it can be an organized abscess with dense echoes and thick walls.

Very often with good treatment this amoebic liver abscesses resolve, but sometimes if they do not resolve or if the patient has more symptoms, we might have to aspirate them under ultrasound guidance.

Sometimes we might have to leave behind a pigtail catheter till the abscess is totally drained.

A patient could have multiple liver abscesses and in fact this is a postmortem picture of a liver showing multiple abscesses from Dr. Balachandran's book on amoebic liver abscesses and he has done extensive work in this subject.

Liver abscesses very often resolve or you have to drain them, but sometimes they can present with multiple complications and one such complication is a rupture.

Here, for example, we have a liver abscess from the left lobe, which is rupturing into the pericardial area, tearing the diaphragm and extending into the pleural cavity so the abscesses can rupture into the perihepatic space.

They could rupture into the peritoneal cavity, they could rupture into the pleura or the lung or they could rupture even into the pericardium.

This is another example of a ruptured liver abscess.

We see a lot of perihepatic fluid and we see fluid within the right thorax.

Sometimes it might be very difficult to differentiate amoebic liver abscess from a solid liver tumor.

This differentiation is very important.

In the earlier days, we used to resort to CT or sometimes maybe an MRI to differentiate between the two, but nowadays we use contrast to differentiate the two.

Typically. On contrast, we see that an abscess does not show any internal enhancement.

We see peripheral enhancement with a relatively quick washout and sometimes we might see peripheral hyperemia in abscesses.

Very often we might see enhancement of the septae within the abscess, so ultrasound contrast is a very good technique, especially to differentiate an unliquefied abscess from a solid tumor.

Liver abscesses, of course, which are of amoebic origin have to be differentiated from those which are of pyogenic origin, typically pyogenic abscesses are multiple, they're scattered and very often again on contrast they show enhancement.

Sometimes it is difficult to differentiate between the two history and sometimes aspiration are helpful to differentiate.

The amoeba can also involve the intestine and typically very often we might see marked thickening of the terminal ileum, the caecum and the ascending colon, indirect haemagglutination tests like the IHA tests are available for the diagnosis of amoebiasis.

One patient could get infested with multiple parasites.

Here for example, we have one patient who has amoebic liver abscess along with roundworms in the intestine.

Filariasis (Wuchereria Bancrofti)

The other parasite, which is very well seen on ultrasound is filariasis or more commonly what we see is the wuchereria bancrofti.

Typically these are seen in dilated lymphatics in the region of the inguinal canal and as we have seen earlier, what we see is a continuous or a nonstop dance.

This can also be recorded on a pulse doppler because of the movement in the initial days just to make sure that we are dealing with the correct diagnosis.

We used to aspirate these lymphatic channels and look at these worms under the microscope.

Lymphatic filariasis is a major cause of morbidity in parts of Asia, Africa and the Western Pacific.

Almost about 120 million people are affected worldwide, but almost about 75 million are asymptomatic and therefore this goes undetected.

The lifecycle is completed in two hosts.

The definitive host is a man and the intermediate host is a mosquito, and the mode of infection is a mosquito bite whereby the third stage of the infective larvae are liberated.

We not only see filaria involving the lymphatics in the inguinal region, but very often we might see the filarial worms even in the epididymis.

A chronic manifestation of filariasis can be in the form of lymphadenopathy in the groin, it can be in the form of lymphedema a bad disease which is known as elephantiasis, hydrocele or chyluria.

Sometimes some of these patients could be referred for a color doppler of the venous system to rule out venous insufficiency or thrombosis, but all we see in this patients on ultrasound is marked thickening of the skin with poor penetration of the sound beam.

We can see this dilated lymphatics not only in the region of the inguinal canal all along the scrotal wall, but sometimes we might also see them in the retroperitoneal area.

For example, in this patient we see dilated lymphatics in the retroperitoneum, in the right iliac fossa, and within these dilated lymphatics we have the filarial worms dancing.

This is a very interesting case.

This patient presented with a linear swelling close to the elbow, which was thought to be a venous malformation and as the patient was referred for a color doppler.

But when we did our ultrasound, we realized that instead of a venous malformation, what we have is multiple linear channels and within these linear channels we have the filarial worm dancing and this was indeed a case of filariasis and not of venous malformation.

Breast is another common site for filariasis and this happens because of the loose adipose tissue.

So very often on mammography you might see a mass, but on ultrasound you realize that this is a sonolucent mass with multiple dancing filaria.

And this is one situation where a patient who presented with a mass or when you see a mass on mammography, you're indeed happy to see such filarial worms because you know that you're not dealing with malignancy.

So sometimes in the breast we might pick up very small lesions and within the small lesions we might see the filarial dance.

So with some or sometimes in the breast we might see multiple dilated lymphatic channels like this.

And within the dilated lymphatic channels we see the filarial worms and again, they can produce artifacts on color doppler simply because of the movements.

This is a very unusual case of a parotid filaria which has been given to me, which one of my friends.

Very often with treatment, the intensity of the dance reduces and whenever there is a healing, what we see is a filarial granuloma, which is quite an echogenic area without any live worms.

Malaria (Plasmodium Vivax and Plasmodium Falciparum)

Within the other parasite which could have some ultrasound features is plasmodium vivax and plasmodium falciparum, which give rise to malaria.

Very often On ultrasound we might just see hepatomegaly splenomegaly.

Malaria, as we all know, is the most important parasitic disease of man described since antiquity and approximately about 5% of the world population is infected.

This is still a major cause of death in the tropical countries.

The lifecycle is completed in two hosts, the man and the female anopheles mosquito, and the mode of infection is a mosquito bite whereby the sporozoites are liberated into the bloodstream.

Malaria has two types.

One is a benign malaria where the patient very often gets fever anemia and settles down, but we can have a malignant malaria where we can have lot of complications including cerebral malaria, et cetera.

This is one complication where ultrasound can be useful.

If a patient of malaria has a acute pain in the abdomen, a possibility is of a splenic rupture, and here we have a patient who has a splenomegaly with a splenic rupture with splenic fluid collection.

The other complication, which is rarely seen in malaria, is a splenic infarct and whenever patients with malaria present with acute pain in the left upper abdomen, you should suspect splenic infarct.

On ultrasound, we typically see them as a wedge shaped hypoechoic area and on color doppler, there is no flow.

Contrast, again is very useful in making a definitive diagnosis of splenic infarct and we can again save this patient from costly investigations.

Differential Diagnosis: Dengue Fever

A very close differential diagnosis of malaria with a similar presentation is dengue fever.

Dengue, however, is not a parasitic infestation.

It is a viral infection, but it has got typical ultrasound features.

Typically what we see is marked thickening of the gallbladder wall and edema.

We might see pleuritis with fluid in the pleural cavity and fluid in the peritoneal cavity.

This is another typical finding of dengue.

Very often we have periadrenal hemorrhages in the adrenal gland and this gives rise to a very bright adrenal.

Dengue, as I said, is a viral fever, which is transmitted from the human to human by mosquito bite and man is a reservoir of virus.

There are two deadly complications of dengue.

One is a dengue hemorrhagic fever and the other is a dengue shock syndrome.

This is a classical case again of a dengue where we have marked gallbladder wall edema.

We have free peritoneal fluid with internal echoes and this is one of the characteristic feature we see fluid typically in the right flank extending above the kidney.

And this fluid typically has dense internal echoes because this is an hemorrhagic fluid.

So these are very classical findings of dengue fever and we can make a diagnosis of dengue based on ultrasound.

Leishmaniasis (Kala-Azar)

The other parasite which gives rise to leishmaniasis is popularly known as kala-azar.

Yeah, we can have a spleen which can extend right from the left hypochondrium to the right iliac fossa.

And when you have a patient with a huge spleen with fever, one has to think of leishmaniasis.

Schistosomiasis

The other parasites which are typical ultrasound features, a cysticer cus and fasciola.

I must admit that I don't see these patients in India and all these cases have been given to me by my friend Dr. Ravi Kumar, who works in UAE and the patients which he sees are typically migrants from the Egyptian area On ultrasound, typically what we see is marked thickening of the urinary bladder wall, sometimes calcification of the urinary bladder wall.

Schistosoma was named after the person who first observed it.

However, the name was changed because of the unique appearance of the male worm, which looks as if it is split longitudinally.

So Schistosoma virtually means a split body where a canal is produced in which the female positions herself.

So now it is typically known as Schistosoma.

We have two common types, one is the Schistosoma mansoni and the other is haematobium.

The lifecycle is completed again in two host, the man and the snail, and the mode of infection is through the skin when man comes in contact with water containing infected snails and thus the final stage larvae.

Here we have another example of schistosomiasis with involvement not only of the bladder, but also involvement of the lower ureter where we see marked thickening of the lower ureter and stricture.

Another common site of infestation is the mesenteric vessels and the portal venous system, and this typically gives rise to periportal fibrosis and therefore very often these patients present with portal hypertension because of periportal fibrosis.

Cysticercosis (Cysticercus Cellulosae)

The other parasite which is typical ultrasound features, is the cysticercus cellulosae typically these are cystic areas within the muscle and within the cystic area we have one bright echo.

The lifecycle is completed in two hosts.

The definitive host is the man and the intermediate host is calf buffalo or pigs, and the mode of infection is eating uncooked beef or pork containing these cysts.

So typically, as I said, within the muscles we have sonolucent areas with one bright echo and very often just to confirm the diagnosis, we might also put in a needle and aspirate the fluid.

So since this are rare, we have cysticerci affecting the scapular area and here we have a cysticercus in the chest wall.

Sometimes of course we can have extensive cysticerci and for this we require help of other imaging modalities like ct and MRI.

Onchocerciasis (Guinea Worm Infection)

Onchocerciasis is another parasite which can be seen on ultrasound.

This is popularly known as Guinea worm infection.

The most common presentation is on X-rays where we very often see linear, bright calcified opacities in the soft tissues.

If you want to do an ultrasound again, we will see a sonolucent area with a linear echo within the center.

The lifecycle is again completed in two hosts.

The definitive host is a man, an intermediate host is a cyclops, and the mode of infection is drinking water containing infective cyclops.

And this is how a typical Guinea worm looks like when it is extracted through the body.

Differential Diagnosis: Actinomycosis and Mycetoma

Something which looks similar to this is actinomycosis.

This is not a parasite, this is a fungal infection, but it has got a similar appearance.

We have hypoechoic tracks and we have linear bright echoes within this.

A very bad form of fungal infection typically seen in India is what is known as mycetoma named after the place.

From where we see this, this can give rise to extensive soft tissue masses and it can give rise to bony destruction as well and it can lead to amputation of the foot as well.

Toxoplasmosis (Toxoplasma Gondii)

The other parasite, which has some ultrasound features typically in the fetus is toxoplasma gondii.

Here again, the lifecycle is completed in two hosts, the trizonic cycle we have a cat, and for the exo cycle we have the man typically in the fetus.

Antenatally, we see calcifications in the periventricular area.

That's a postnatal follow up, or we might see calcifications within the abdomen of the fetus, typically affecting the liver or the adrenal gland.

But whenever we see calcific foci in a fetus, one should also consider the possibility of CMV infection, which again is not a parasitic infestation, but a viral infection, but can present in a similar way.

Conclusion

So to conclude, several parasitic infestations can have direct or indirect ultrasound features.

Ultrasound can be useful in diagnosis, management and follow up of patients.

I have to thank my friend and colleagues who have contributed to this talk.