Peregrina C. Labay

Ureteral Dimensions and Specifications for Bioengineering Modeling

Publisher Summary This chapter discusses ureteral dimensions and specifications for bioengineering modeling. Ureter is an adaptive organ, functioning as an adaptive system that alters one or more of its characteristics and dimensions to meet its functional requirements. A new ureter must be actively contractile so that it empties and sterilizes itself completely. It must carry no residual urine and should imitate normal rhythms, bolus volumes, and functional demands. A new ureter must be patent and offer low resistance to the elaboration of urine by the nephron. It should not absorb urinary constituents and should have a smooth lumen that provides no nidus for calculus formation, infection, or obstruction. It should allow only unidirectional flow with no retrograde peristalsis or reflux. The wall of the new ureter must be tolerated biologically and immunologically, and should not secrete substances into the urinary tract.

Surgical Implications of Ureteral Neurology

Ureteral nerves have been dissected, described, photographed and successfully stimulated. Acceleration of peristalsis by sympathomimetic drugs has been easily demonstrated. Critical experiments have a

Principles of Bladder Function

Bladder rhythm is an important concept of physiology. Bladder physiology can be described by the classifical organ model, by the urodynamic model and by the neurophysiological model. The organ model deals with the coordinated functions of the smooth muscle in the detrusor and bladder neck, and of the skeletal muscle of the urethra and external sphincter. The urodynamic model describes the bladder capacity, shape, pressure gradients, flow rate and outflow resistance by the armamentarium of a urodynamics laboratory. The neurophysiological model describes the innervation, pathways, and the centers in the spinal cord and brain stem dealing with the control, coordination, integration, onset and cessation of the micturition. Once these concepts are understood, specific urodynamic abnormalities can be suggested from specific features of the patient’s history, physical examination, cystoscopy and intravenous urograms. Urethrovesical coordination is controlled by many reflexes. Continence should be classified and quantitated in order to be rationally treated. The various surgical procedures for the management of incontinence are analyzed in terms of their underlying physiological effects.

A Comparison of Other Conduit Organs with the Ureter: Reaching toward a Clearer Concept of Ureteral Peristalsis

Publisher Summary This chapter focuses on the comparison of other conduit organs with the ureter to highlight ureteral peristalsis. The similarities between the ureter and other conduit organs deserve exploration as they offer an approach to modeling, to descriptive science, and to laboratory and surgical techniques in the development of the ideal ureteral replacement. A number of organs can be considered as a possible model for the ureter such as the vas deferens, the fallopian tubes, a muscular artery, a vein, a single-tube heart of the fish and primitive vertebrates, various segments of the gastrointestinal tract, the appendix, and the bile duct. The vas deferens has a thick muscularis like the ureter but does not show the distensibility of the ureter. Its muscularis consists of an inner, thinner, and outer, thicker longitudinal layer with powerful circular intermediary layer. The fallopian tube shows rhythmic contractions and is extremely responsive to prostaglandin; it has other pharmacologic and endocrinologic receptors in common with the ureter. The bile duct is more comparable to a urethra than to a ureter because it has no active propulsion of its own.

Laboratory Models of Diseases Altering Ureteral Hydrodynamics

Publisher Summary This chapter focuses on several laboratory models of diseases altering ureteral hydrodynamics. The simplest anatomic examples of abnormalities in the ureter that alter peristalsis are the immobile segment, a defect bridged by a plastic tube, a fibrotic segment, and a ureter encased in a periureteral fibrosis. Ureteral stricture is a constricted aperistaltic segment that acts as a physiological dam to increase the resistance through that segment and, eventually, to diminish the maximum flow rate. It tends to elevate the intraluminal pressure above the point of obstruction and to distend the ureteral segment proximal to the stricture. The ureter at the level of the obstruction develops inflammatory edema, followed by proliferative changes to form a ureteral bar, fibrotic inflammatory tissues, and then a scar. Below the calculus, the ureter is empty, unstimulated, and inactive. A model or schema can be synthesized from these various conditions to summarize the factors modifying the pathophysiologic effects of ureteral obstructions with renal, ureteral, and intraluminal factors.

Observations on the Ureter after Renal Autotransplantation

Publisher Summary This chapter discusses several observations on the ureter after renal autotransplantation in dogs. In a study described in the chapter, female dogs were divided into two groups according to the method of ureteral reanastomosis. The first group consisted of five dogs that underwent ureteroneocystostomy; the second group included five dogs that had ureteropyelostomy. In the first postoperative week, intravenous urography showed the pelvis of all the transplants to be slightly or moderately dilated. This dilatation reached a maximum by the third or fourth week and gradually receded. After ureteroneocystostomy, the lower ureter remained slightly dilated, possibly as a result of the stenosis at anastomosis or to urinary tract infection. After ureteropyelostomy, the ureter was also slightly dilated in its entire length. All dogs showed urinary tract infection as a result of Pseudomonas or Escherichia coli; three of six recovered by the fourth month. The result shows that periureteral fibrosis must be considered as a factor in all renal and ureteral transplantations.

Ureteral Peristaltic Pressure Methods

Publisher Summary This chapter discusses several methods that help in better understanding of ureteral physiology. Direct observation of the ureter reveals the color and caliber of the wall, the presence or absence of peristaltic activity, and its rate and direction. Causes of malfunction such as constrictive adhesion and compression or tenting by the catheter tip can be determined. Ureteral peristaltic pressure is measured with indwelling catheters after ureteral catheterization during cystoscopy, through a nephrostomy or ureterostomy tube, or after bladder explantation. Ureteral pressure is measured through the catheter to the transducer, which is connected to a recorder. It is necessary that the whole system be airtight and bubble-free; there should be no clots or shreds in the lumen and no kinks or bends. Ureteral peristalsis is sensitive to temperature, pH, and mechanical stretching. The ureteral perfusion method offers an entirely different concept of ureteral peristaltic activity as it measures the resistance to flow, demonstrating its dynamic variability.