The ureteral lumen during peristalsis.

This study concerns the size and shape of the ureteral lumen and an assessment of its enlargement during peristalsis. To stop the action of the living dog ureter, it was flooded with isopentane close to its freezing point (160°C). The ureter remained frozen until completion of all technical procedures. Photographs of the cut end of active ureters also provided evidence of its luminal characteristics and a movie was achieved of its continuous action. The totally collapsed lumen is stellate in form, epithelial surfaces being in virtual contact. As the lumen opens the points of the stars are last to go, but a square shape and finally a circle result. In a typical experiment, the collapsed lumen had a cross sectional area of 0.12 mm2, enlarging to 2 mm2 in diuresis. This X 17 enlargement occurred over a 3 cm length of the peristaltic wave. Enlargement of the lumen is largely accommodated by thinning of the muscle coats and attenuation of the mucous membrane, there being relatively little gross enlargement of the total segment. Direct photography of the cut end of the proximal segment of the ureter completely confirms the section studies. As an aid in understanding abnormal conditions affecting the ureter, there is much current interest in its normal hydrodynamics. A little information has recently been forthcoming concerning peristalsis and discharge rate (Tsuchida, '69), but there appears to be no data in the literature bearing on the shape or size of the lumen in its varying functioning states. It is not difficult to observe the ureter during peristaltic activity in an anesthetized dog and its lumen can be studied and photographed after sectioning. But the production of objective data as to size and shape that represents the living, functioning characteristics of the tube presents difficulties. Although there were a number of failures, success was achieved in many cases through the use of a quick freezing technique. With ureteral peristalsis going on, a section of the tube in action was rapidly flooded with isopentane brought close to its freezing point by immersion in liquid nitrogen. Isopentane (2-methylbutane) freezes at 160°C, and remains liquid till close to that temperature. After flooding and almost instantaneous freezing, the section of ureter was quickly removed and AM. J. ANAT., 133: 255-258. immersed in the same fluid. Transferred to a freezing storage area, i t was subsequently cut into blocks and these were sectioned on a freezing microtome. The sections were then stained and cleared on the slide. Intermittent serial sections through the various blocks allowed microscopic observations of luminal characteristics throughout the length of the segment undergoing peristalsis (figs. 1 a-4a). Analysis of the irregular luminal shapes that resulted presented some difficulties. No formulae or planimetric methods were found to be feasible to determine area for the luminal cross section. This was finally achieved by comparison to standard circular cross sectional areas through the weight relations of paper cut-outs. The straight line relationship between weight and area of standard circular cut-outs was expressed as a line graph and the crosssectional area of irregular luminal shapes was then derived through the weight of the cut-out. Standard "Aquabee" layout bond paper was used and the histological sections were projected to 100 diameters. Many visual observations of the ureter in action were made. Since the peristaltic