Radiology and epidemics,
new and old
adiology is the interdisciplinary crossroads for most medical specialities, from traumatology to cardiology. There is one exception: usually, not too many high-technology examinations are requested by the infection wards. Anyhow, if physicians dealing with infectious patients want to refer one of them to radiology there is always trouble and discussion because, in contagious cases, the x-ray room used has to be closed and disinfected after the examination. Usually, these wards have their own mobile x-ray system and only plain x-rays of their patients are made.
In radiology, therefore, there is not much contact with the specialists in infectious diseases, and often limited knowledge about these diseases exists among radiologists. Furthermore, for those practicing medicine in Europe, the worldwide extent of infectious diseases is difficult to imagine.
One hundred years ago, or even as recent as fifty years ago, the situation was different. In 1892, 21% of the German population died of infectious diseases, in 1920 13.6%. The figure dropped to 0.83% twenty years ago, and to 0.78% in 1987.
In the years before World War I, the slums of London and many other big cities all over Europe were characterized by dirt, drunkenness, terrible poverty, and exploitation. One in three infants died before reaching its first birthday. After the introduction of medical examinations at schools, it was reported that nearly 20% of the children were unfit to be taught because they suffered from worms or other infectious diseases.
Resurgence of tuberculosis
Tuberculosis was one of the foremost and most feared killers. In a treatise on climatic health resorts published in the mid-nineteenth century, the author underlined that at least 25% of the customers of pharmacies suffered from phthisis, i.e. tuberculosis . The author recommended moving to Madeira as a possible remedy.
Improved sanitary and living conditions and better medicines – in particular antibiotics – developed after the First and Second World Wars changed this situation. In Europe and parts of North America the incidence of tuberculosis declined steadily from the 1930s until the 1980s.
Cavities in the lungs may form quite early in tuberculosis. Reading chest x-rays, looking for single cavities or diffuse spread, typically constituted a major, albeit rather boring, daily task for a radiologist 30 years ago. Fluoroscopy and x-ray population screening became a household part of radiology between the 1930s and the late 1970s. At this time, finally, tuberculosis was considered almost eradicated in Europe. Although tuberculosis was no longer deemed a threat to mankind, the disease still remains a marker of poverty and social decline.
Today we once again see a rapid increase in tuberculosis, most dramatically in the big cities of the U.S.A. but also in France, Great Britain, Central and Northern Europe. Tuberculosis is primarily seen in immigrants but also connected to HIV infection. In one Northern European country, 5% of the immigrants proved positive for tuberculosis in the late 1970s, but today that number has climbed to 40%. The worldwide situation looks even worse. The tuberculosis bacterium has infected 1.75 billion people; of the 50 million people who die every year all over the world, two to three million die from tuberculosis. It is the leading killer among infectious diseases. In comparison, “only” one million die from malaria.
As with many other contagious diseases, most cases of tuberculosis occur in developing countries, although it is not a tropical or exotic disease as is malaria. Overpopulation, the lack of water and hygiene in many parts of the world, as well as the general absence of or the failure to realize health programs are the cause of the increased incidence of contagious diseases.
Travelling adds to the problem, but the single most important factor behind the resurgence of tuberculosis is the worldwide spread of AIDS, a disease that is often accompanied tuberculosis infection and of which tuberculosis may well be the first sign.
It should not be forgotten, however, that there are many tropical diseases. Among those that are almost unknown to Europeans but are not exclusive to the tropics is amoebiasis. Many radiologists are familiar with the name of the disease, but have you ever seen an amoeboma? When performing a barium enema it can look like a carcinoma constricting the colon.
The World Health Organization (WHO) estimates that some 200 million people, most of whom live in tropical and subtropical countries, are infected with bilharziasis, or schistosomiasis. This infectious water-borne disease is transmitted by snails carrying the parasitic flatworm that causes it. Once bilharziasis is established in an area, it is virtually impossible to eradicate – and the disease is on the rise in many regions of Africa.
At least one quarter (sic!) of the world’s population suffers from ascariasis. The roundworm ascaris is the most common cause of jaundice in children all over South America, Africa, and Asia.
The round dance of tropical diseases continues with echinococcosis, trypanosomiasis, typhoid, leprosy, and, of course, malaria. When I attended a course on tropical diseases as a medical student, the professor pointed out that actually most of these diseases are exotic rather than tropical – because they are exotic to us and extinguished in most of Europe. But malaria was found in Italy, southern Switzerland, even in the Baltic States not so long ago and leprosy was well established all over Europe. Geographical names such as Rosenheim, a town close to Munich, are proof of it – it has nothing to do with roses but rather means “leprosarium”.
Role of radiology
Let’s return to radiology: Although the diagnosis of infectious diseases is not a primary indication of diagnostic imaging in Europe, radiologists are performing increasingly examinations of immigrants and travellers returning from the tropics. Plain x-rays, ultrasound and other basic imaging examinations are helpful in primary diagnosis and follow-up. CT and MR imaging are useful in the diagnosis of a limited number of these diseases, such as cysticercosis, particularly if cerebral or spinal affections are being investigated.
Sometimes, when you read images with changes or lesions inexplicable to you – and without proper medical history on the referral sheet, you should think twice and ask the patient: “Have you been abroad?”
Patients might not mention recent travels to the referring physician because they may not consider it pertinent. With many parasites or infections there is a delay before symptoms of the disease occur, and I have seen a number of cases where the radiologist directed the referring physician towards the diagnosis of a tropical disease.
In spite of this, radiography or other imaging methods are rarely mentioned under the heading of diagnostics in manuals or textbooks on tropical diseases, such as that written by Bell . Physical examinations and laboratory tests remain the backbone of diagnostics. The major exception is again tuberculosis, with chest x-rays in pulmonary tuberculosis, x-rays of the joints and spine when they are affected, and plain abdominal x-rays in urogenital tuberculosis.
Although x-ray and ultrasound allow the visualization of changes, particularly when they are gross, these modalities do not lead to a concrete differential diagnosis, and in some cases the radiologist can offer the referring physician up to 40 choices. The radiological report thus provides only a small piece in the mosaic of the diagnostic workup.
In Europe and North America AIDS has become the single most fashionable infectious disease for sophisticated diagnostic imaging. CT and MR imaging of the central nervous system, thorax and abdomen to detect and monitor systemic manifestations have become commonplace. Because AIDS is such a ghostly threat in the industrialized world, vast amounts of money have been poured into research, including the development of new imaging techniques. Imaging might even contribute to fighting the disease.
But other epidemics such as tuberculosis, the plague, cholera, and yellow fever are also spreading. According to WHO, at least 29 new pathogenic agents have been discovered in recent years, among them the Ebola virus and hepatitis C. They might become a prominent health issue, even in Europe, because it appears that treatment with antibiotics will become more and more difficult, due to the increasing drug-resistance of some strains of bacteria.
Will there also be a role for radiology, especially high-technology radiology, in the diagnosis of these diseases? It seems unlikely. Exceptions might be in monitoring disease with spiral CT or MR imaging, ultrasound or CT-guided biopsies, and interventional radiology, for instance in tuberculosis.
It is always good to know more about the diseases we do not normally see, first, to be able to recognize them in case we happen to come across patients suffering from them, and second, not to be mentally stuck with the ordinary diseases we encounter every day. Just as common European diseases may be regarded as exotic in other parts of the world, those that European call “exotic” are common elsewhere.
1. Schultze R: Die Insel Madeira. Aufenthalt der Kranken und Heilung der Tuberkulose daselbst. Enke Verlag: Stuttgart 1864.
2. Bell DR. Tropical medicine. 4th ed. Blackwell Scientific: Oxford 1995.