Early determination of laminitis by use of Doppler ultrasonography in diet induced hyperinsulinemia in Shetlandponies

Abstract

The aim of this study is to investigate the usefulness of Doppler ultrasonography in early detection of laminitis in ponies. This is done by studying the effects of diet-induced insulin intolerance on the diameter and blood flow in the lateral palmar digital artery in Shetland ponies. The hypothesis for this study is that by using Doppler ultrasonography changes can be measured in the diameter and blood flow from the lateral palmar digital artery as result of diet-induced insulin intolerance, which is a part of Equine Metabolic Syndrome (EMS). More specifically, the expectation is that due to EMS, the diameter will be smaller, the artery will be less flexible and thus blood flow will be lower. There were two groups of Shetland ponies. One experimental group of seven ponies and one control group of four ponies. The experimental group was fed with a high concentrate diet to induce weight gain and so diet-induced hyperinsulinemia. The control group was fed according to daily requirements. In five weeks, three measurements were done every other week. Doppler ultrasonography images were made from the digital palmar lateral artery, with the focus to determine blood flow in the artery. Also ultrasonography images were made to determine the diameter of the artery. The ponies developed signs of EMS, but none of the ponies developed clinical laminitis. Diameter was smaller at every time of measuring in the experimental group compared with the control group, one time a trend was visible, one time there was a significant difference. Resistive index, pulsatility index and systolic-/diastolic velocity ratio are indices of resistance of blood flow. Most of these parameters were significantly higher in the experimental group at all times, which indicates a higher resistance of blood flow in the artery. Blood flow was lower in the experimental group at every time of measuring, significantly at two times, indicating that due to the stiffness in the artery, less blood could pass. In conclusion, Doppler ultrasonography is useful to measure diameter and blood flow from the lateral palmar digital artery. However it requires a person who is experienced in making these ultrasounds. To obtain reliable measurements and further research needs to be done before these parameters can be used as reliable measurements for the early detection of insulin intolerance induced laminitis.