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Friday, June 27, 2014

Schistosomiasis in Tanzania--a prologue

I am in the African Republic of Tanzania. This year I have again accompanied a group of medical students from University of California at Irvine who will be teaching bedside ultrasound to clinical officer students at a medical school in Mwanza, the second largest city in this East African country. We will also be looking at the utility of ultrasound in diagnosing schistosomiasis, a parasitic disease which is endemic here.

Mwanza is on the coast of Lake Victoria, a huge body of water also bordered by Kenya and Uganda. Much of the commerce here has to do with the lake, both relating to tourism and fishing. Schistosomiasis is a water borne disease caused by a fluke that lives in the lake, harbored by snails. The snails are infected by the schistosomiasis miracidia and shed cercaria capable of infecting humans into the beautiful blue water where they penetrate the skin of mammals that swim in the lake. The flukes move through the lymphatic system, penetrate the blood vessels of the lungs and end up in the left heart and thence the blood vessels. They attach themselves to our blood vessel walls, nourish themselves on our blood, copulate constantly and produce eggs which are intensely irritating to our various internal organs. We eliminate eggs in our urine and bowels which go back into the water system to mature and complete the cycle.

Infection with Schistosoma mansoni and S. haematobium which are the predominant species here in Tanzania can cause fibrosis of the portal veins of the liver with chronic liver disease, scarring of the intestines and bladder with resulting kidney failure, malnutrition and anemia and chronic ulcerations of the lower genital tract. Less common and even more nightmare inspiring complications, including spinal cord and brain infection also occur. Most people in this community are infected, though only a relatively small proportion have noticeable symptoms. The most heavily exposed people are the most severely infected, including fishermen and car washers, but also include school aged children who are weakened and perform more poorly at school. Women with schistosomiasis genital lesions may be at higher risk for contracting HIV. Patients with associated bladder or liver disease are at higher risk of developing cancer of those organs.

Schistosomiasis is one of the "neglected tropical diseases" which are neglected because they occur primarily in very poor areas and to very poor people. In the case of schistosomiasis, neglect is enhanced because it is debilitating and chronic but not usually fatal. Nutrition and genetics affect how sick a person gets after being infected. Tourists sometimes return with schistosomiasis, but rarely to any great harm. The treatment is simple, a big dose of an anti-parasitic medication called praziquantel given once. It will clear the fluke from the blood stream and the body can heal any damage that is not advanced enough to be irreversible. In many patients, though, treatment is delayed until long after the point of no return.

The best way to cure schistosomiasis is to completely prevent infection, and since contact with   water is life to many people who live on the shores of rivers or lakes, the solution involves getting rid of the fluke. Some countries, most notably Japan, have entirely eradicated the disease using various approaches. Ideas that can work include biological control of snails, introducing predators or competing snails or infecting bacteria. Poisoning them doesn't work very well because other mollusks and fish also die. The very successful fishing industry in Mwanza, based on introduced Nile Perch which have decimated the omnivorous cichlid species that ate, among other things, snails, has worsened the snail problem. Dams and irrigation projects move snails to previously unaffected areas increasing the numbers of people exposed to the disease. Reducing certain plant growth along shores of ditches can reduce snails. Infected humans continue the cycle of infection by soiling water sources with urine or feces, so places with active sanitation efforts can significantly reduce their schistosomiasis burden. Large health organizations have proposed blanket treatment of school aged children with praziquantel, potentially yearly in some high risk communities, to both control human disease and reduce the reservoirs that lead to reinfection. This will be hugely expensive, but is probably necessary as part of a larger prevention effort.

I am looking forward to spending some time with the students on a large island in Lake Victoria where, we are told, 100% of the population has schistosomiasis. I expect we will see a vast array of tropical birds and fish and wide expanses of beautiful water, meet new and interesting people and see all kinds of tragic and preventable pathology. I might even go swimming. More later!

Friday, June 6, 2014

They do make an ultrasound probe that plugs into a USB port!

"They should make an ultrasound probe that plugs into your laptop. It could just hook into a USB port."

Ultrasound technology has become progressively more accessible to doctors who aren't radiologists. During my training, some obstetricians imaged the bellies of their pregnant patients to quickly see how the baby was lying in the womb and assess its progress. Other than that, ultrasound resided in the realm of the radiologists, who lived in dark rooms and interpreted blurry pictures for the rest of us. Since ultrasound is not expensive and has many potential applications, far beyond just seeing fetuses, other specialties have adopted it and doctors in resource poor countries where there are no radiologists have come to rely on it for all sorts of information. Trauma surgeons and emergency physicians can use it to rule in or out life threatening conditions, and internal medicine physicians like me can improve on the accuracy of our physical exams and sometimes avoid the cost of more complex and dangerous imaging procedures. Ultrasound can be used to guide procedures, making them safer. The machines have become smaller and are even pocket sized. It's all so very exciting.

So why not an app for the iphone? Why not Google glasses with which one can see ultrasound images of the patient in front of me? Why not a wireless ultrasound transducer?

The possible avenues of progress in very portable ultrasound technology have been slow for various reasons. First, many people are happy with radiologists imaging the body and cardiologists imaging the heart using large and expensive machines. The system works. It doesn't require the rest of us to learn ultrasound and the pictures are good and the rather large charges benefit hospitals. Bedside ultrasonographers are looking for inexpensive machines and it is unclear how much the use of these will increase the revenue stream which drives much of what happens in research and development in medicine.

Having wandered through the healthcare device industry's displays at many ultrasound conferences and having surfed the internet I thought I knew what kind of technology was available for doing bedside ultrasound imaging. I had seen an ultrasound transducer that plugged into an iPhone made by a company called Mobisante, and had seen their iPad/transducer combo. The software was buggy and the pictures were not impressive and the whole package did not end up being handy or attractive. I bought the GE Vscan machine which is about the size of my hand, and like my hand, fits in my pocket. The pictures are good and it does most of what I want it to do. So when people asked about just buying a transducer for a laptop and plugging it in I told them that clearly that was a great idea but it didn't exist.

Except that I was wrong. The company Interson, out of the Bay Area in California, makes transducers for imaging blood vessels, deeper structures such as abdominal organs, and cavities such as the throat and vagina/uterus. I had the opportunity to try their abdominal probe in the last few weeks. It is definitely a clever and versatile device, despite several drawbacks.

The probe is called SeeMore, which will probably not help sell the product. It is about as heavy as a small hardback book and it is a little big to have comfortably in a pocket. It has an inescapable resemblance to a personal vibrator which will also not help sell it. It is actually the same transducer that Mobisante used in their iPhone device. On the very positive side, though, it gives really good pictures of the abdomen, uterus and bladder. Its resolution is good enough that it could be used to rule in or out a pneumothorax, which my Vscan is not quite up to. Its image acquisition is slow so when looking at the heart it is not possible to see the delicate movement of the heart walls or valves, though it is possible to see grossly abnormal cardiac function or pericardial effusion from an abdominal approach. It does not do color doppler, so it cannot give any indication of blood flow. It has its own software that loads quickly onto a laptop and it could be used with a tablet so long as it has a windows operating system. The USB attachment can go into a USB to mini-USB converter so the tablet doesn't even need to have a full size USB port. Once the software is loaded it has calculations that are user friendly and intuitive calipers for measurements plus all of the usual gain adjustments that a person might want. There is a button on the transducer that freezes and unfreezes the image. After images are stored they can be printed or transmitted easily as JPEGs. If I worked in a bush hospital somewhere and needed my ultrasound just to evaluate unborn babies or critically ill or traumatized patients, this transducer would be just the ticket. If I used a laptop as I went from room to room, as I did at my last job, I can imagine information from this device being integrated seamlessly into my documentation as I examined the patient. The transducer I tried does not visualize superficial structures, like blood vessels or bones or tendons, abscesses or thyroids, but Interson makes a linear transducer that does. Each transducer costs $4000 new, and the software, support and hefty plastic case with tiny tube of ultrasound gel are included. My Vscan cost over $8000 and the cheapest portable ultrasound machine that hospitals in the US buy costs over $40,000 new. (Veterinary ultrasound machines and ones that are used in developing countries can cost much less than this, even in the sub $1000 range for a used machine.) From where I stand this USB transducer is an affordable alternative for point of care ultrasound, though I do like a machine that gives better pictures of the heart.

What about the Google glasses thing? I think somebody has a patent for that, though it's not commercially available. What about the wireless transducer? Yes. It exists. It is not Bluetooth, a proprietary short distance wireless connection that uses ultra high frequency radio waves. It uses a different proprietary ultra wide band wireless connection which can handle more information. The one that I found is called the Freestyle, by Acuson, which is now owned by Siemens. It looks like a TV remote and I think it's just for superficial structures.

As there is demand, these machines will get lighter, cheaper, more versatile and attractive. The potential is awesome and I'm looking forward to trying out new toys that will allow me more capably to help my patients.