Advancing CKD tied to microvascular alterations

Progression in chronic kidney disease (CKD) appears to be accompanied by decreasing structural and functional capillary density, a recent study has found.

Ninety-six CKD patients participated in the study and were divided into four subgroups (n=24 for each), according to disease stage: 2, 3a, 3b, and 4. Nailfold video capillaroscopy was performed to measure capillary density at three points: baseline, after 4 minutes of arterial occlusion, and after 2 minutes of venous occlusion.

At baseline, capillary density significantly declined with advancing CKD stage. Those with stage 2 disease showed a density of 32.6±2.8 capillaries/mm², dropping to 31.2±3.8 and 32.5±3.3 capillaries/mm² in patients with stage 3a and 3b CKD, respectively. By stage 4, density was at a low of 28.5±3.1 capillaries/mm² (p=0.011).

During post-occlusive hyperaemia, the correlation between capillary density and CKD stage remained significant. Density was 39.4±3.0 capillaries/mm² among patients with stage 2 disease and decreased to 33.8±3.3 capillaries/mm² in the most advanced stage (p=0.021). A similar trend was observed during venous congestion (stage 2 to 4 CKD: 41.1±3.1 to 35.2±3.4 capillaries/mm²; p=0.032).

On the other hand, office pulse wave velocity and common carotid intima-media thickness both increased with advancing CKD, though not significantly so. Multivariate analysis identified estimated glomerular filtration rate was a positive predictor of post-occlusive capillary density (β per ml/min increase, 0.053, 95 percent confidence interval [CI], 0.004–0.101).

“[T]his study suggests that, in parallel to arteriosclerosis and atherosclerosis in the large and medium-sized arteries, structural alterations at the microvascular level do exist in CKD and deteriorate with renal function loss,” the researchers said.

“Further studies with valid methodology should assess the extent to which this capillary rarefaction affects the incidence of cardiovascular events in our patients,” they added.