Acute changes in kidney size during IV urography were studied in normal rats and in rats with artificial unilateral renal artery stenosis. In normal rats, IV bolus injection of sodium iothalamate (400 mg I/ml), 1.5 ml/kg body weight, produced an increase in area of the renal silhouette by an average maximum of 12.7% after 60 seconds. In nine out of ten rats which developed hypertension after left sided renal artery clamping, renal distension was either small or absent on the stenosed side, while the contralateral right kidney showed normal distension during IV urography. Two out of three rats, which remained normotensive after renal arterial clamping, showed normal distension of both kidneys. These results confirm earlier observations in man that the acute changes in size of the kidney during IV urography can be used as an aid in the urographic screening of hypertensive patients for significant renal arterial stenosis. In all rats with arterial clamp and hypertension, the stenosed kidney was smaller than its contralateral mate. An index between the size of the non-stenosed and the stenosed kidneys greater than 1.15 was only seen in these particular rats.

The development of hypertension after kidney transplantation was examined in a consecutive series of 83 transplantations (79 patients) with a graft survival of more than 30 days. After transplantation, 50% of the normotensive recipients developed mild or severe hypertension, while 74% of the hypertensive recipients remained hypertensive. Stenosis of the graft artery with a narrowing of the diameter of more than 50% was found in 13 patients and in 3 patients a minor or peripheral stenosis was found. Significantly more stenoses were seen in the presence of two donor arteries, whereas no other etiological factors could be shown. In arterial stenosis, severe hypertension was established within a few months after transplantation, but in spite of satisfactory controlled blood pressure and good graft function, hypertensive crises could arise. It is therefore concluded that arteriography and renin analysis should be considered in all cases of severe hypertension, and surgical correction should be considered when arterial stenosis is present.

A photoelectric device for repeated, noninvasive registration of blood pressure in the tail of the rat was built, mainly using available materials and components. A description of the measuring system is given. Comparison between blood pressure measurements performed simultaneously in the tail of the rat and intravascularly in the aorta are in good agreement.