Causes and pathogenesis of megaureter

The causes of the megaureter are congenital anatomical obstruction in the lower ureter, which leads to a violation of the urine outflow above the obstruction to increased intra-ureter pressure, a gradual expansion of the lumen of the entire ureter, a violation of its contractility, the expansion of PMS, hydroureteronephrosis with gross irreversible morphological changes in the kidneys.

The congenital absence of a closure device in the ICP leads to similar changes. In these cases, the ureteral orifice is widened and gaping. These changes correspond to neuromuscular dysplasia of the lower cystoid ureter (achalasia) followed by the development of lesions of all sections of the megoureter and kidneys (ureterohydronephrosis).

Neuromuscular dysplasia of the ureter is one of the most frequent and severe anomalies of the VMP. Despite the large number of works devoted to the study of this anomaly, there is still no consensus on etiology, pathogenesis and treatment. On the difference in the views of authors on these questions, the names of the megaureter: atonia, dalatation, enlargement of the ureter, giant ureter, dysplasia testify. Megourareter, megadolichoureter. Ureteral hydroacuperation, forced ureter, etc.

The causes and pathogenesis of a megaureter are explained in different ways. Some authors believe that the inadequate development of the neuromuscular device of the ureter lies at the heart of congenital ureteral expansion, while others associate the development of a megaureter with a functional or organic obstruction localized at the level of the pre-tubercular, juxtavezic or intramural ureter. Recently, neuromuscular dysplasia is understood as a combination of congenital narrowing of the ureter and its intramural part with neuromuscular dysplasia of the lower cyst.

Comparing the number of patients with this ureteral malformation detected in a polyclinic with the number of patients on treatment in the clinic, we noted that ureteral dysplasia would be detected much more frequently if this category of patients were subjected to a urological examination.

The most frequent dysplasia of ureters in the early stage is found in children from 3 to 15 years, mainly at the age of 6-10 years. In adults, dysplasia of ureters is more often observed in later stages of development, complicated by pyelonephritis and renal insufficiency. Females are more likely to suffer from this developmental malformation (the ratio of women and men is 1.5: 1). Two-sided dysplasia of ureters occurs more often than one-sided dysplasia. The vice is localized on the right almost 2 times more often than on the left.

ON. Lopatkin, A.Yu. Svidler (1971) observed 104 patients and conducted a microscopic examination of 33 resected ureters, as well as ureters taken during autopsy from corpses. The authors found that the amount of nerve fibers in the wall of the dysplastic ureter (from the pelvis to the pre-tubercular part of it) was sharply reduced. In most drugs, they are not detected. Such changes were found in dysplastic ureters of patients of different ages - from 26 weeks to 45 years. In the study of the so-called aganglionary zone in the pre-tubular part of the ureter, the same basic nerve elements as in the ureter of healthy people are identified. This allowed us to assume that the motor ability of the pre-tuberous ureter during dysplasia should not be disturbed. The congenital absence of intramural nerve plexuses throughout the ureter, with the exception of the pre-tubercular department, means congenital degeneration of the neuromuscular elements of the ureter and leads to the complete exclusion of its walls from the contractions.

Megoureter should be considered as a manifestation of dysplasia. In this case, the phenomena of dysplasia can be expressed in the zone of only the last or penultimate cyst. In such cases, one can speak of achalasia of the ureter. This treatment of the etiology of giant ureters explains the reason for the rapid expansion of the ureter throughout the entire length or in a limited area and allows one to treat achalasia and megaureters as stages of the same process. At the same time, it should be noted that the inevitable consequence of ahalasia is the megaureter. Which leads to ureterohydronephrosis.

There are several classifications of ureteral dysplasia, but first of all it should be emphasized that neuromuscular dysplasia of ureters is a bilateral anomaly.

Consequences of the narrowing of the opening and intramural section of the ureter, as well as the violation of the ureter's tone, can be the elongation and expansion of cystoids. The expansion of the lower cyst is called achalasia. In this case, the urodynamics of the upper cysts is preserved. The involvement of the two upper cystoids with an increase in the length of the ureter is called a megaureter. Moreover, the ureter is sharply enlarged and elongated, its contractile movements are substantially slowed down or absent, the dynamics of emptying are severely impaired. This allows me to distinguish the following stages of ureter dysplasia:

• I - latent, or compensated (achalasia of ureters);
• II - occurrence of a mega -ureter as the process progresses;
• III - development of ureterohydronephrosis.

Neuro-muscular dysplasia of the ureters does not have a characteristic manifestation, and it is usually found in the urinary tract infection.

Anatomical or functional obstruction in the lower part of the ureter leads to urinary stasis above the obstruction, increased intra-ureter pressure, a gradual widening of the lumen of the entire ureter, a violation of its contractility, an expansion of the pelvioureteral segment, uregeral hydronephrosis with coarse irreversible morphological changes in the kidneys.

In connection with the fact that the anomaly is bilateral, the slow progression of the pathological process in the kidneys leads to the development of severe chronic renal failure. The unfavorable outcome of the disease is explained by the absence of pathognomonic symptoms for this developmental malformation and late diagnosis.

Macroscopically, with a mega -ureter, the ureters are sharply enlarged, elongated, as a result of which they bend in the retroperitoneal space in the most bizarre way. The diameter of the ureters reaches the diameter of the small intestine. The intramural and juxtavezic parts of the ureters over a distance of 0.5-1.0 cm are narrowed to 0.5-0.6 cm, their wall is thickened. In this case, apparently, one should speak not about the true, but about the relative narrowing in comparison with the sharply widened overlying ureter.

[1], [2], [3], [4], [5]

Classification megaureter

Obstructive mega -ureter is a consequence of impaired PMS. It occurs with neuromuscular dysplasia of the ureter, congenital stricture of the PMS and the ureter valve.

The most appropriate is the classification of the mega-ureter proposed by NA Lopatkin and A.G. Pugachev in 1940, based on the secretory function of the kidneys, estimated using radioisotope dynamic nephroscintigraphy.

Classification megaureter NA. Lopatkina and A.G. Pugacheva by the degree of impaired renal function

• Degree I - decreased secretory function of the kidney less than 30%.
• Degree II - decreased secretory function of the kidney by 30-60%.
• Degree III - decreased secretory function of the kidney more than 60%.

[6], [7]