Paper - Double ureters in human and pig embryos
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Double Ureters in Human and Pig Embryos
The double ureter has a certain developmental importance in that it furnishes a clew for the disappearance of the cloacal segment of the Wolffian duct, and its manner of incorporation into the bladder. Two cases of complete double ureter were reported in 1905; one is the Mall embryo, no. 175 (13 mm.) and the other in the Keibel embryo, Piper (24 mm.). Both of these embryos show that the ureter from the lower part of the kidney lies dorsal to the ureter from the upper pole, and as they swing around to occupy a lateral position on the Wolffian duct, the dorsal or lower ureter is displaced lateralward, while the ventral or upper ureter lies between it and the Wolffian duct. This rotation from a dorsal position on the Wolffian duct to a lateral one is completed at the time when the cloacal segment of the duct has expanded into the lateral funnel-shaped process of the bladder proper. The accompanying figures, nos. 27 to 24, inclusive, and‘ 22 and 19, are taken from drawings made of the Keibel embryo, which is at present not available for study. figure 27, the lowest of the series, shows the. convexity of the right ureter A, and 26, the section immediately above it, shows the opening of this ureter into the bladder. The next section up indicates the convexity of ureter B, indicated in black, and section 24 its orifice in the bladder. In figure 22, ureter B lies slightly dorsolateral to ureter A, and the convexity of the curve of the left ureter is shown with its orifice in the bladder three sections higher up (19). This latter figure shows the double ureter on the right lying almost in the sagittal plane, i.e., the ureter B from the lower pole of the kidney practically dorsal to ureter A from the upper pole. Both of these ureters have already migrated to a position cephalad to the opening of the Wolffian duct, and the interval between the orifices is so small that in a gross specimen they might readily be mistaken for a single orifice.
In the Mall embryo the orifices of the two ureters and the Wolffian duct are, so far as I was able to determine them, in common. It would seem, therefore, that where we have wide displacements of the orifices of the two ureters they are to be found in displacement downward of the median one, i.e., the one lying between the normal ureter orifice and the opening of the Wolffian duct.
I also called attention to the fact that the rotation of the ureter around the Wolffian duct was entirely independent of kidney rotation and position; and that the displacement of the ureter was completed at the time that the cloacal segment of the Wolffian duct was definitely incorporated into the bladder. In the pig the rotation seems to be accomplished before this absorption is completed, so that the ureter opens laterally into the Wolffian duct at some distance from the orifices of the duct into the urogenital sinus. '
I have found but two pigs with evident ureteral duplication or diverticulae. Pig 47 has a complete double ureter on the left side. figure 9-24 shows the emergence of the upper ureter from the pelvis of the kidney. figure 10-5 shows that of the lower ureter from its pelvis. In 11-1 the ureter from the lower pelvis B is already lateral to ureter A from the upper pelvis, and maintains this position through 11-2, 11-3, and 11-4. In 11-3 the two ureters open into the lateral expansion of the Wolffian duct in about a normal position as indicated in the normal ureter on the right; ureter B lying in front of ureter A.
The only essential difference between the relations as shown in fig. 47 and the human embryo is that the twist of the two ureters in the pig appears to run to a higher level than in the human being, and, second, that a cloacal segment of the Wolffian duct persists in the pig at the time that the rotation has been completed.
Cases have been reported in the human being, however, where this general rule, that the ureter from the upper pelvis comes to lie medial to the ureter from the lower pelvis and in consequence has a lower orifice in the bladder, does not obtain. Weigert,
Hyrtl and Kerr have reported cases in which the rule above stated has not prevailed. Kerr has made a report on a case of a double ureter in which the ureter from the upper pelvis lies lateral to the ureter from the lower pelvis as the two curve toward the bladder. In so far as I am aware, there is no developmental explanation. for this anomaly, however, a somewhat similar condition was found in pig 3. figure 10-8 shows the origin of the right ureter from the kidney. figure 10-15 shows the lower pole of this kidney with the two ureters, right and left, running forward. In figure 10-17 shows the right ureter A, and behind it a blind ending ureteral diverticulum indicated in black and marked RX. Following this down 10-20 shows it somewhat more medial than in 17, and in 10:23 and 10-24 this lower dorsal ureteral diverticulum comes to occupy the position of the normal ureter from the upper pelvis of the kidney. It appears to end blindly or to fuse with the right ureter in 10-22. Unfortunately, this pig series was cut at 50,; and the finer details of structure cannot be definitely determined.
It would, however, appear possible that this diverticulum to form a second ureter might have arisen from the first ureter but close to its orifice in the Wolffian duct, and on its medio—inferior aspect, and that it was merely dragged out in the upward migration of the kidney. However, had this aberrant ureter connected functionally with the kidney proper, it would have taken exactly the position described in these cases which appear contrary to the rule, and would also mean that Where the ureter from the lower part of the kidney comes to lie medial to the ureter from the upper part of the kidney, that the two orifices into the bladder are close together, in other words, we would not expect a displacement of the medial orifice away from a normal position.
This would, therefore, merely be an exaggeration of an incompletely double ureter, and it would only differ from the latter by reason of the origin of the lower ureter close to the orifice of the upper ureter in the Wolffian duct. It would, of course, be possible to establish this point quite definitely if sufficient number of ureteral duplications could be observed in serial sections. The anomaly is so unusual that the chance of finding intermediate stages, even in the analysis of large numbers of series, is very slight.
I am merely reporting this anomaly because it is so unusual and because it seems to offer some sort of explanation for the few cases of complete ureter duplication which do not follow the rule.
- Abnormalities in the form of the kidney and ureter dependent on the development of the renal bud. A. G. Pohlman, Johns Hopkins Hospital Bull., vol. 16, Feb., 1905.
- Complete double ureter in man by A. T. Kerr, Anatomical Record, vol. 5, 1911, p. 55.
Cite this page: Hill, M.A. (2020, June 6) Embryology Paper - Double ureters in human and pig embryos. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_Double_ureters_in_human_and_pig_embryos
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