The kidneys and the eyes are sensitive to blood pressure changes. The kidney participates in blood pressure control and renal disease can cause arterial hypertension and be aggravated by hypertension, entering a vicious circle between both alterations. In human patients with hypertension, increased vascular resistance is observed in renal and ocular arteries. This increased vascular resistance can be measured with Doppler ultrasound by calculating resistive and pulsatility indices. Increased renal and ocular indices have been observed in human patients with hypertension, and a correlation between the indices and the systolic blood pressure and hypertensive damage has also been reported. The indices values in normal animals vary slightly among the studies and the technique, the operator and, the administration of sedative or anaesthetic drugs can cause variation of the indices. Then, obtaining your own reference values is necessary. The aim of this study is to determine if increased vascular resistance is found in dogs and cats with diseases that can cause hypertension and whether they are related with arterial blood pressure. Values were obtained in non-sedated healthy animals and the effect of a sedative protocol appropriated to be used in ill animals, if necessary, was evaluated. Then renal and ocular resistive and pulsatility indices and systolic blood pressure were obtained in dogs and cats with diseases that can cause hypertension, such as renal disease, diabetes mellitus, hyperadrenocorticism, and hepatic disease. Significant increased renal indices were found in the disease groups in comparison to healthy animals. Correlations with blood parameters and the indices were also found in different diseases. Correlation with blood pressure was not found in any of the groups. In conclusion, increased peripheral vascular resistance was found in the kidney in animals with these diseases, as well as certain degree of relationship with the severity of the disease (evaluated by means of blood parameters). However, no correlation with systolic blood pressure was observed.