pediagenosis: Urinary
Article Update
Loading...
Showing posts with label Urinary. Show all posts
Showing posts with label Urinary. Show all posts

Sunday, May 9, 2021

RETROCAVAL URETER

RETROCAVAL URETER


RETROCAVAL URETER
The normal right ureter runs lateral to the inferior vena cava (IVC). A retrocaval (also known as circumcaval) ureter is a congenital anomaly in which the right ureter passes posterior to the IVC, emerges between the IVC and aorta, and then recrosses the iliac vessels anteriorly before inserting into the bladder. The portion of the ureter lying posterior to the IVC becomes obstructed, leading to dilation of the more proximal parts of the urine collecting system. This obstruction can become symptomatic during childhood or, more commonly, adulthood. The exact incidence of retrocaval ureter is uncertain but is likely 1 : 1000 to 1 : 1500, with males affected more often than females.

RETROCAVAL URETER

Embryology
A retrocaval ureter reflects abnormal development not of the ureter, but rather of the IVC. In the fourth week of gestation, the cardinal system of veins drains the body of the developing embryo. This system is divided into the two major branches: the anterior cardinal veins, which drain the superior portion of the embryo; and the posterior cardinal veins, which drain the inferior portion of the embryo. These join to form a common cardinal vein, which drains into the sinus venosus. Meanwhile, the vitelline veins, the precursors of the portal system, drain blood from the yolk sac to the sinus venosus. Finally, the umbilical veins carry oxygenated blood from the placenta to the embryo.
VESICOURETERAL REFLUX

VESICOURETERAL REFLUX


VESICOURETERAL REFLUX
Vesicoureteral reflux (VUR) is defined as the retrograde flow of urine from the bladder into the ureter and, in many cases, the renal pelvicalyceal system. This condition is considered problematic because it facilitates propulsion of bacteria toward the kidneys, which can cause recurrent pyelonephritis, renal scarring, and eventual renal dysfunction.
VUR is generally diagnosed during childhood. The overall incidence has been difficult to estimate because the condition is often undetected and frequently resolves with age. It has been reported, however, that 70% of infants who have urinary tract infections (UTIs) also have reflux. Although VUR is more common in male infants, it is more common in females after the first year of life.
MECHANISM AND GRADING OF VESICOURETERAL REFLUX

Pathogenesis
Normal ureteral continence relies on a valve mechanism formed as the ureter courses between the bladder mucosa and detrusor muscle before terminating at the ureteric orifice. When the bladder contracts, compression of the intramural segment of each ureter prevents the retrograde flow of urine.
URETERAL DUPLICATION

URETERAL DUPLICATION


URETERAL DUPLICATION
As shown in Plate 2-1, the ureteric buds appear toward the caudal ends of the mesonephric ducts at 5 weeks of gestation. Each bud grows into its adjacent mass of metanephric mesenchyme, the precursor of the kidney, to form a ureter, a pelvicalyceal system, and collecting ducts.
Ureteral duplication results from abnormalities of the ureteric bud. It is one of the most common congenital malformations of the urinary tract, with an incidence of approximately 1 in 125. Duplication is more often unilateral than bilateral, and more often incomplete than complete. There does not appear to be any predilection for a particular side.

COMPLETE URETERAL DUPLICATION

Complete Ureteral Duplication
In complete ureteral duplication, the kidney is drained by two distinct renal pelves, each of which leads to a ureter with its own insertion into the bladder. This anomaly occurs when a single mesonephric duct sprouts two ureteric buds, each of which induces a separate portion of the adjacent metanephric mesenchyme. The more cranial of the two ureteric buds becomes the collecting system of the upper pole, while the more caudal of the ureteric buds becomes the collecting system of the lower pole. Because of the manner in which the mesonephric ducts exstrophy into the bladder; however, the upper pole ureter terminates at an orifice located inferior and medial to that of the lower pole ureter. In many cases, the upper pole ureter has an ectopic site of termination, reflecting an especially cranial position of the ureteric bud from which it originated. The consistent pattern of ureteral crossing seen in a duplicated system, where the ureter serving the upper pole terminates inferior to the ureter serving the lower pole, is known as the Weigert-Meyer law.
ECTOPIC URETER

ECTOPIC URETER


ECTOPIC URETER
An ectopic ureter terminates caudal to the normal position in the trigone. Although a ureter that terminates cranial to the normal position is clearly abnormal, and is often associated with vesicoureteral reflux (see Plate 2-21), the term “ectopic” is generally not applied.
In males, the most common sites of ureteral ectopia are the prostatic urethra and seminal glands (vesicles), whereas in females, the most common sites are the urethra and vagina. The incidence of ectopic ureter is not known with precision, although one series estimated it at 1 in 1900. The condition is at least twice as common in females than in males, for unknown reasons.

ECTOPIC URETER

Pathogenesis
As described on page 30, the ureteric buds appear toward the caudal ends of the mesonephric ducts during the fifth week of gestation. Each ureteric bud grows into the adjacent mass of metanephric mesenchyme, the precursor of the kidney, to form a ureter, a pyelocalyceal system, and collecting ducts.
URETEROCELE

URETEROCELE


URETEROCELE
A ureterocele is a cystic dilation of the terminal ureter that balloons into the bladder. About 80% of ureteroceles are associated with ureteral duplication, occurring in the ureter that drains the upper pole (see Plate 2-23). About 10% of ureteroceles are bilateral.
A ureterocele is known as “intravesical” if it extends only into the bladder, and “ectopic” if it reaches the bladder neck or urethra. The orifice is termed “stenotic” if a pinpoint opening is seen and “sphincteric” if it lies distal to the bladder neck. If the orifice possesses both of these characteristics, it is known as “sphincterostenotic.”
The overall incidence of ureteroceles is difficult to estimate because many small ureteroceles are not identified. The clinical incidence of ureterocele, however, appears to range from 1 in 5000 to 1 in 12,000. In contrast, one autopsy series reported the incidence to be as high as 1 in 500. For unknown reasons, there is a female : male ratio of 4 : 1, and most cases occur in whites.

GROSS AND FINE APPEARANCE OF URETEROCELE

Pathogenesis
The embryologic basis for ureteroceles is unknown, but several theories have been proposed. One is that ureteroceles result from incomplete breakdown of the Chwalla membrane, a normally transient structure that divides the ureter from the bladder. Although this theory explains ureteroceles with stenotic orifices, it does not explain those with patent orifices. Another theory is that the terminal ureter is lined with an inadequate number of smooth muscle cells, which causes it to become dilated.
URETERAL DUPLICATION

URETERAL DUPLICATION


PRUNE BELLY SYNDROME
The prune belly syndrome (PBS, also known as Eagle-Barrett or triad syndrome) is a rare, congenital disorder that occurs almost exclusively in males. Its major features include deficient abdominal wall musculature, bilateral cryptorchidism, and urinary tract anomalies that include renal dysplasia, hydronephrosis, and dilation of the ureters and bladder.
PBS occurs in approximately 3.5 per 100,000 live male births. Blacks are at increased risk and Hispanics are at decreased risk when compared with the overall population. There are rare reports of females born with deficient abdominal wall musculature and urinary tract anomalies, although their ovaries are generally normal.

Appearance of abdominal wall in prune belly syndrome

Pathogenesis
The pathogenesis of PBS remains poorly understood. One theory argues that early obstruction of the bladder outlet causes dilation of the bladder, ureters, and then renal pelves. Such dilation is posited to cause an increase in intraabdominal pressure that results in atrophy of the abdominal wall musculature and inhibition of normal testicular descent. This hypothesis, however, is challenged by the fact that many patients with PBS do not have an anatomic outlet obstruction, and that many patients who do have such obstructions (such as those with posterior urethral valves) do not have PBS.

Tuesday, April 27, 2021

ANOMALIES OF THE URACHUS

ANOMALIES OF THE URACHUS


ANOMALIES OF THE URACHUS
As described on page 32, the urorectal septum partitions the cloaca into the primitive urogenital sinus and the rectum. The urogenital sinus, which gives rise to the bladder, is initially continuous with the allantois, a tube that extends into the connecting stalk (see Plate 2-4 for an illustration). As the bladder matures and descends into the pelvis, however, the allantois narrows to form a thick, epithelial-lined tube known as the urachus. Normally the urachus regresses into a fibrous cord, known as the median umbilical ligament. For uncertain reasons, however, this normal regression process sometimes fails, resulting in a persistent urachus that is either partially or completely patent. Because many urachal anomalies are undiagnosed, their overall incidence is unknown.


Presentation And Diagnosis
An entirely patent urachus, which permits drainage of urine from the bladder to the umbilicus, accounts for about half of urachal anomalies. It typically presents during the neonatal period as dribbling of fluid from the umbilicus. The fluid leakage may increase in response to bladder contraction during either purposeful voiding or other increases in intraabdominal pressure, such as during crying or straining. Umbilical edema and delayed healing of the umbilical stump may also be noted. The diagnosis can be confirmed with either sonographic evaluation of the bladder or with more invasive studies, such as a retrograde fistulogram or voiding cystourethrogram (VCUG).
BLADDER DUPLICATION AND SEPTATION

BLADDER DUPLICATION AND SEPTATION


BLADDER DUPLICATION AND SEPTATION
Bladder duplication and septation are very rare congenital abnormalities, with only a small number of cases reported in the scientific literature. In either duplication or septation, division of the bladder may be complete or incomplete, and it may occur in the coronal or sagittal plane.
In duplication, each half of the divided bladder receives its own ureter and possesses its own full thickness wall. In incomplete duplication, the two halves typically unite above the level of the bladder neck and then drain together into a single urethra. In complete duplication, the two halves remain separate to the level of the bladder neck and can even drain into two independent urethras, each with its own external meatus. In some cases, however, one of the bladder halves lacks a urethral component, resulting in outlet obstruction and ipsilateral renal abnormalities.
In septation, a fibromuscular wall divides the bladder into separate compartments. In contrast to duplication, septation produces two compartments that share a common wall. Like duplication, septation can be incomplete or complete, depending on how far the wall extends toward the bladder neck. Septation, however, is not associated with duplication of the urethra, and thus both compartments must be in open communication with the urethra. In some cases, however, fusion of the septum with the bladder neck causes one compartment to lose access to the urethra, resulting in obstruction.
Bladder duplication and septation are frequently associated with other anomalies, especially in the genitourinary system. For example, vesicoureteral reflux may be seen on one or both sides, resulting in hydronephrosis if severe. Likewise, one or both of the bladder components may lack a normal continence mechanism. If there is complete duplication of the bladder, concurrent duplication of the external genitalia may be seen as well. Less often, duplication may also occur in the lower gastrointestinal tract or spine.
BLADDER DUPLICATION AND SEPTATION


Pathogenesis
The embryologic basis for these various anomalies is unknown. It is possible that complete duplication of the bladder and adjacent organ systems reflects partial twinning of the embryonic tail early in gestation. In contrast, isolated defects of the bladder may reflect abnormalities during cloacal septation (see Plate 2-4).

Anatomy Physiology

[AnatomyPhysiology][recentbylabel2]

Featured

[Featured][recentbylabel2]
Notification
This is just an example, you can fill it later with your own note.
Done