In man, intra-abdominal hypertension (IAH) has been shown to impair renal perfusion. Renal microcirculation is difficult to study in vivo and little is known about the effect of increased intra-abdominal pressure (IAP) on kidney microcirculation. For the first time, we evaluated renal cortex microcirculation with side-stream dark field (SDF) imaging in a porcine model of IAH.

We studied five anesthetized and ventilated pigs (46 ± 3 kg) during incremental IAP levels (10, 20 and 30 mmHg during 45 min each) by infusing warmed saline into the peritoneal cavity. The renal venous pressure (RVP) was measured with a renal vein catheter. After right mini-lumbotomy and gentle removal of the renal capsule, the SDF device was positioned intermittently on the renal cortex, avoiding pressure artefacts. Subsequently, representative video-clips (10 s) were captured and the microvascular flow index (MFI) was scored blindly by three independent observers, based on the semiquantitative method of Boerma and colleagues 1.

The MFI decreased significantly from 2.51 ± 0.30 to 1.76 ± 0.26 (P < 0.03) when the IAP increased from 10 to 30 mmHg. The RVP increased significantly from 10 ± 4 to 34 ± 5 mmHg (P < 0.00003) with the IAP increasing from 6 to 30 mmHg. There was an inverse correlation (r = -0.63, P < 0.003) between the MFI and RVP (Fig. 1).