The ureter is a complex functional conduit carrying urine from the kidneys to the bladder. Any pathologic process that interferes with this activity can cause renal abnormalities; the most common sequels are hydronephrosis (see Chapter 14) and infection. Disorders of the ureter can be classified as congenital or acquired.
CONGENITAL ANOMALIES OF THE URETER
Congenital ureteral malformations are common and range from complete absence to duplication of the ureter. They may cause severe obstruction requiring urgent attention, or they may be asymptomatic and of no clinical significance. The nomenclature can be confusing and has been standardized to prevent ambiguity (Glassberg et al, 1984).
The ureter may be absent entirely, or it may end blindly after extending only part of the way to the flank. These anomalies are caused during embryologic development, by failure of the ureteral bud to form from the mesonephric duct or by an arrest in its development before it contacts the metanephric blastema. The molecular and genetic determinants of bud development and the causes of bud abnormalities are complex but are being elucidated (Nagalakshmi and Yu). In any event, the result of an atretic ureteral bud is an absent or multicystic dysplastic kidney. The multicystic kidney is usually unilateral and asymptomatic and of no clinical significance. In rare cases, it can be associated with hypertension, infection, or tumor. Contralateral vesicoureteral reflux is common, but usually of limited clinical significance. There has been a concern about the risk of malignancy in these cases; however, the preponderance of evidence now suggests that no treatment is necessary and indeed no follow-up is needed from a urological standpoint (Onal and Kogan, 2006).
DUPLICATION OF THE URETER
Complete or incomplete duplication of the ureter is one of the most common congenital malformations of the urinary tract. Nation (1944) found some form of duplication of the ureter in 0.9% of a series of autopsies. The condition occurs more frequently in females than in males and is often bilateral.
The incomplete (Y) type of duplication is caused by branching of the ureteral bud before it reaches the metanephric blastema. In most cases, this anomaly is associated with no clinical abnormality. However, disorders of peristalsis may occur near the point of union (Figure 37–1).
Duplication of the ureter. Incomplete (Y) type with hydronephrosis of lower pole of left kidney. Ureteroureteral (yo-yo) reflux can also occur and account for the radiographic appearance.
In complete duplication of the ureter, the presence of two ureteral buds leads to the formation of two totally separate ureters and two renal pelves. Because the ureter to the upper segment arises from a cephalad position on the mesonephric duct, it remains attached to ...