A comprehensive overview of clinically important infections of the urinary tract Urinary tract infections (UTIs) continue to rank among the most common infectious diseases of humans, despite remarkable progress in the ability to detect and treat them, Recurrent UTIs are a continuing problem and represent a clear threat as antibiotic-resistant organisms and infection-prone populations grow,
Urinary Tract Infections: Molecular Pathogenesis and Clinical Management brings the scientific community up to date on the research related to these infections that has occurred in the nearly two decades since the first edition, The editors have assembled a team of leading experts to cover critical topics in these main areas:
This essential reference serves as both a resource and a stimulus for future research endeavors for anyone with an interest in understanding these important infections, from the classroom to the laboratory and the clinic,
DUANE R. HICKLING,1 TUNG-TIEN SUN,2 and XUE-RU WU3,4
The mammalian urinary tract is a contiguous hollow-organ system whose primary function is to collect, transport, store, and expel urine periodically and in a highly coordinated fashion (1,2). In so doing, the urinary tract ensures the elimination of metabolic products and toxic wastes generated in the kidneys. The process of constant urine flow in the upper urinary tract and intermittent elimination from the lower urinary tract also plays a crucially important part in cleansing the urinary tract, ridding it of microbes that might have already gained access (3). When not eliminating urine, the urinary tract acts effectively as a closed system, inaccessible to the microbes. Comprised, from proximal to distal, of renal papillae, renal pelvis, ureters, bladder, and urethra, each component of the urinary tract has distinct anatomic features and performs critical functions.
The renal papilla, into which each renal tubule-rich pyramid drains, is considered the first gross structure of the upper collecting system. In humans and other higher mammals, renal papillae are individually cupped by a minor calyx, which in turn narrows into an infundibulum. Infundibuli vary in number, length, and diameter but consistently combine to form either 2 or 3 major calyces. These branches are termed upper, middle, and lower-pole calyces depending upon which pole of the kidney they drain. The renal pelvis represents the confluence of these major calyceal branches and itself can vary greatly in size and location (intra-renal vs extra-renal) (Fig. 1). It should be noted that, in rodents, there is only one renal papilla with a corresponding calyx.
FIGURE 1 Normal anatomy of the kidney and upper urinary tract. (Reprinted from reference 163, with permission of the publisher.)
The ureters are bilateral fibromuscular tubes that drain urine from the renal pelvis to the bladder. They are generally 22–30 cm in length and course through the retroperitoneum. They originate at the ureteropelvic junction (UPJ) behind the renal artery and vein and then progress inferiorly along the anterior portion of the psoas muscle. As the ureters enter the pelvic cavity they turn medially and cross in front of the common iliac bifurcation. The ureters pierce the bladder wall obliquely (termed the ureterovesical junction or UVJ and travel in this orientation for 1.5 to 2.0 cm within the bladder wall to terminate in the bladder lumen as ureteral orifices (4). The intramural ureter is compressed by the bladder wall passively during storage and dynamically during emptying. This, in effect, prevents vesicoureteric reflux during steady state and micturition (Fig. 2). Along the length of the ureter there are three segments that physiologically narrow: the ureteropelvic junction, the ureterovesical junction, and where the ureters cross the common iliac vessels. These areas are clinically relevant as they represent the most common locations where ureteral calculi become trapped, causing obstruction.
FIGURE 2 The ureterovesical junction. In this figure, A represents an orthotopic ureteral orifice. There is adequate length of ureteral tunnel in the bladder and therefore no reflux. Lateral and/or superior insertion of the ureteral orifice (B& C) can lead to inadequate submucosal ureter length and, potentially, reflux. (Reprinted from reference162, with permission of the publisher.)
The bladder is a hollow, distensible pelvic viscus that is tetrahedral when empty and ovoid when filled. It is composed primarily of smooth muscle and collagen and, to a much lesser degree, elastin (5). Its superior portion is defined by the urachus, a fibrous remnant of the allantois. The
