The Lower Urinary Tract






Figure 11.1


Urinary tract, x-ray

This intravenous pyelogram image is obtained following intravenous injection of a radiopaque contrast agent filtered out of the glomeruli into the urinary tract. It shows a normal urinary tract, with contrast material filling the renal pelves (♦), then the ureters (▲), and finally the bladder (∗). The kidneys are at the level of vertebrae T12–L3.



Figure 11.2


Double ureters, gross

Complete ureteral duplication is shown, with two ureters (◀) exiting from each kidney and extending to the bladder, opened anteriorly. A segment of aorta lies between the normal kidneys. A partial or complete duplication of one or both ureters occurs in 1 in 150 people. There is a potential for urinary obstruction owing to abnormal flow of urine and the entrance of two ureters into the bladder in close proximity; however, most of the time, this condition is an incidental finding.



Figure 11.3


Normal ureter, microscopic

This normal ureter in cross-section is shown at low magnification, with an inner longitudinal layer (◼) and an outer circular layer (▪) of smooth muscle (the opposite of the bowel) to supply peristaltic movement of urine down to the bladder from the renal pelvis. There is a lining of urothelium (▲) and underlying lamina propria (♦). Ordinarily, the lumen remains nearly closed because ureters do not store urine. Prolonged stasis of fluid predisposes to infection in the urinary tract.



Figure 11.4


Normal urothelium, microscopic

This normal urothelium with an underlying basement membrane is stratified and no more than 5 to 7 cell layers thick, and 2 to 3 cells thick in a distended bladder. The topmost superficial layer is composed of plump (“umbrella”) cells that have microplicae on the luminal border, have tight junctions between them, and can stretch laterally as the urine passes or collects within the lumen.

The bladder urothelium produces a mucoid secretion with natural antibacterial properties. This feature, along with normal complete episodic emptying of the bladder, helps to prevent urinary tract infections. The underlying lamina propria has connective tissue with scattered small vessels.



Figure 11.5


Ureteropelvic junction stenosis, gross

There is irregular scarring over the cortical surface of this kidney because of chronic obstruction and development of acute and chronic pyelonephritis. The renal pelvis (∗) is markedly dilated, but the ureter (♦) is not, indicating that the point of obstruction is at the ureteropelvic junction (▲). This condition usually manifests in childhood and most often affects boys. This is the most common cause of hydronephrosis in infants and children.



Figure 11.6


Hydroureter, gross

A long-standing obstruction (congenital) at the ureteral orifice through which the metal probe passes led to the marked hydroureter and hydronephrosis seen here. This patient had recurrent urinary tract infections complicated by pyelonephritis. Functional or anatomic obstruction of the urinary tract is termed obstructive uropathy. Developmental anatomic anomalies account for most cases of obstructive uropathy in children. In adults, calculi, prostatic hyperplasia, and neoplasms may lead to obstruction.



Figure 11.7


Hydroureter, CT image

The left ureter (♦) seen near the left renal pelvis in this abdominal CT scan without contrast exhibits hydroureter because of obstruction from the presence of urinary tract calculi. Each kidney is normal in size. Calculi are the most common cause for obstructive uropathy in adults. During pregnancy, transient dilation can normally occur.



Figure 11.8


Ureteral calculus, CT image

The CT scan without contrast is taken in the prone position (the reverse of the usual CT imaging position with the patient supine) and reveals a bright ureteral calculus (▲) at the vesicoureteral junction. Because many urinary tract calculi contain calcium (calcium oxalate or calcium phosphate), they can appear bright with radiographic imaging. Purely radiolucent stones identified with CT imaging are most often composed of uric acid, while cystine stones are rare.



Figure 11.9


Ureteritis cystica, gross

The small, smooth, glistening bumps (▼) seen here over the ureteral mucosa are termed ureteritis cystica and represent cystic areas of glandular metaplasia resulting from inflammation, producing cystic nodules 1 to 5 mm in size. Such lesions are of insufficient size to impede urine flow. They are more commonly seen in the bladder, where they are called cystitis cystica . These lesions are unlikely to have premalignant potential.



Figure 11.10


Urinary bladder, gross

This urinary bladder is opened anteriorly at autopsy and has a normal shape and size, but there is prominent trabeculation (▲) seen over the mucosal surface. This is the consequence of bladder muscular hypertrophy from bladder outlet obstruction with nodular prostatic hyperplasia. The outpouchings of mucosa between the muscular trabeculations are “pseudodiverticula,” which do not have a complete muscular layer. The stasis from obstruction also predisposes to urinary tract infections because there is incomplete emptying of the bladder with residual urine. The urethral obstruction can also lead eventually to bilateral hydroureter and hydronephrosis.

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Dec 29, 2020 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on The Lower Urinary Tract
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