OSAKA -- A research team from Toyama University has found that symptoms of the pollution-related illness "itai-itai disease" are more complicated than originally thought, it has emerged.
The researchers discovered that the kidneys in deceased patients with itai-itai disease typically shrink by about 60 percent prior to death. The team also discovered that the parts of the kidney responsible for regulating water levels and secreting hematopoietic hormones are heavily damaged by itai-itai disease.
On May 8, 1968, the disease was officially recognized as a pollution-related illness. The team's discovery, half a century later, throws new light onto the disease, whereby kidney tissues are affected chiefly by cadmium poisoning. The word "itai" means painful in Japanese.
Looking ahead, the team's findings are expected to help prevent conditions such as nephropathy caused by cadmium poisoning and also lead to the development of new therapies -- with the possibility of preventative measures emerging for health problems in other countries such as China.
The team, which includes Toyama University professor Joji Imura, analyzed the autopsy documents of 26 women aged 70 or above who died of causes other than itai-itai disease, and compared them with those of 38 itai-itai disease patients stored at the university. In particular, they made comparisons in relation to which parts of the kidneys had been damaged.
As a result, they found that on average the size of kidneys in patients with itai-itai disease was about 60 percent smaller than those in people without the disease. Specifically, it was discovered that glomeruli -- a network of capillaries in both kidneys that filter waste products in the blood -- were heavily damaged near the surface but not so deeper down.
Moreover, in the kidney tubules, obvious lesions were observed on the proximal kidney tubules, but hardly any were seen on the distal kidney tubules. Also, the parts which store hematopoietic hormones that create red blood cells had also decreased.
Among patients with itai-itai disease, as well as the preceding illness cadmium nephropathy, many people have anemia as well as difficulty regulating water levels. However, not many require dialysis. Until the team's findings, it was thought that the sole adverse symptom of itai-itai disease was damage to the proximal kidney tubules -- but the team's findings indicate that the disease consists of more complex symptoms.
With itai-itai disease, kidney function worsens for a long period of time due to cadmium poisoning, resulting in fragile bones due to a lack of calcium.
(Japanese original by Ryo Watanabe, Osaka Science and Environment News Department)