Wearable haemodialysis
'Portable kidneys' have been prototyped since the 1970s, without ever catching on. But with the UK's haemodialysis units close to capacity, the need for home dialysis is urgent, and our ever-improving ability to miniaturize technology is creating new solutions. A pilot study in The Lancet tries the latest of these – a wearable haemodialysis machine – in eight patients, with encouraging results. Though there were minor problems, such as clotting of the venous access, all patients said that the device was an improvement over standard treatment, and would recommend it to others.
Cannabis and the lung
In the recent fuss about whether smoking cannabis causes psychosis, we’ve lost sight of a much more obvious question: does it cause lung damage? A cross-sectional study from New Zealand in Thorax adds to the evidence that it does. Using pulmonary function tests and high-resolution CT, the investigators found a dose–response relationship between cannabis smoking and airflow obstruction, impaired large airways function and hyperinflation. One joint of cannabis seems to be about as bad as five cigarettes, although few cannabis smokers are likely to be on forty a day.
Vitamin D in renal disease
In patients with chronic kidney disease, vitamin D compounds such as 1 α-hydroxyvitamin D3 or calcitriol are often used to prevent and treat secondary hyperparathyroidism. But a systematic review in Annals of Internal Medicine says they don’t work. Combining data from 76 trials that enrolled more than 3500 patients produced no evidence that vitamin D compounds reduced the risk of death, bone pain, vascular calcification, or parathyroidectomy. Worse still, they were associated with increased risk of hypercalcaemia and, for some compounds, hyperphosphataemia.
Adjuvant chemotherapy in resected colon cancer
Whether the toxicity and inconvenience of adjuvant chemotherapy is justified in colon cancer patients with stage II (node negative) disease who have undergone successful resection has been the subject of debate. A multinational study in The Lancet suggests that it may be worthwhile, albeit not spectacularly so. The authors randomly assigned ~3000 patients to either fluorouracil and folinic acid (with levamisole in some early patients) or observation-only until recurrence. At a median follow-up of 5.5 years, all-cause mortality was about 20% lower in the treated patients, which as survival rates without chemotherapy are high, means only a small absolute difference. The study ran from 1994, however, so newer treatments may be more effective.
Vertebral fracture and BMD
As readers will know, vertebral fracture is the most common osteoporotic fracture. A long-term US study of its risk factors in women, published in JAMA, contains few surprises in terms of aetiology. Low bone mineral density (BMD) and previous vertebral fracture remain the major predictors, supporting the idea that all patients who sustain a vertebral fracture should be treated for osteoporosis. The size of these effects is worth noting: a woman with a previous vertebral fracture and BMD in the osteoporotic range had a chance of sustaining another such fracture over the next 15 years of about 55%, compared to about 10% in a woman with neither risk factor.
Diagnosing pulmonary embolism
Many centres now favour computed tomography pulmonary angiography (CTPA) over ventilation-perfusion lung scanning as the method of choice for diagnosing pulmonary embolism (PE). But does it miss clinically important clots? An RCT published in JAMA suggests not, with similar outcomes in those in whom PE was excluded, regardless of the technique used. However, CTPA involves more radiation exposure, and has more adverse effects and contraindications. It also identified ~30% more patients as having PE, and more research is needed to clarify whether these are false positives.
Bariatric surgery
The relentless rise of obesity has given us a new word and a new medical specialty – bariatrics. A clinical review in The Lancet deals with surgical approaches to the treatment of morbid obesity, and reckons there is good evidence that bariatric surgery is more effective than non-surgical approaches in the management of patients with BMIs that exceed 35. A range of procedures can be used, including laparoscopic gastric banding, Roux-en-Y gastric bypass and biliopancreatic diversion, but all have their disadvantages, and no single operation is ideal for every obese patient.
Screening
Almost everyone, even some doctors, believes that screening for disease must be a good thing. They assume (often wrongly) that if a condition is caught early, treatment will be more effective. In fact, clear thinking about a screening programme often leads to the conclusion that it is unlikely to be either clinically effective or cost-effective in improving health. The US Preventive Services Task Force did this recently, when they recommended against screening for carotid artery stenosis in asymptomatic people. The BMJ, on the other hand, is enthusiastic about the possibility of screening for celiac disease. A study from Hungary describes a rapid antibody test that can be used by nurses in pre-school children. Dr Lydgate suspects that they’ve forgotten Muir Gray’s aphorism: All screening programmes do harm; some can do good as well.
