People with diabetes who develop kidney disease are more likely to also have another diabetes complication: peripheral arterial disease (PAD), in which fatty deposits restrict blood flow to vessels serving the legs and feet. The finding comes from a recent study of about 900 people with type 2, aged 50 to 85.

The study also found that the association works in reverse: People with PAD have higher rates of kidney disease.

PAD often creeps in slowly, showing no symptoms but posing a growing threat to a person’s cardiovascular health. Often, by the time symptoms like leg pain (experienced while walking but ceasing at rest) become noticable, the disease has set in with a vengeance, quadrupling the risk of heart attack, stroke, or loss of a limb.

Luckily, measurement of the leg-to-arm blood pressure ratio—the ankle-brachial index (ABI)—has proven effective at detecting the disease even in its early, presymptomatic phases, which is why researchers in the current study used the index to detect early PAD signs among their type 2 participants.

Their analyses revealed that people with PAD who did not yet have symptoms were more likely to also have other diabetes complications like neuropathy and retinopathy—and the rates went up with high LDL cholesterol, smoking, and longer diabetes duration. But presymptomatic PAD most commonly co-occurred with kidney disease: Its prevalence increased by over 60 percent in the presence of kidney disease.

The researchers aren’t sure why PAD and kidney disease appear together so often. One might help spur the other, or there could be no such relationship. “It’s possible that people with PAD also have problems in their [kidney] arteries,” says lead author Jose Mostaza, MD, PhD, of Hospital Carlos III in Madrid, Spain. “Or it could be that [kidney] disease favors the development of PAD.”

What is certain, says Mostaza, is testing with the ABI can detect a stealthy, potentially deadly diabetes complication before it’s too late. And, he adds, this study suggests that people with diabetes and kidney disease should make ABI testing a priority.

The study was published online in Feb. 2008 in the European Journal of Internal Medicine.