THE PELVIS 



363 



level with the first coccygeal vertebra, because the lumen of 

 the tube is distinctly narrower at these two points. When a 

 radiogram shows a shadow which might be an ureteral calculus, 

 its horizontal level is of as great importance as its vertical plane 

 as an aid to differential diagnosis. 



FIG. 113. Radiogram showing the lower abdominal and the pelvic portions 

 of the Ureters, displayed by the introduction of bougies. 



The surgical approach for the removal of an impacted ureteral 

 calculus may be either retro-peritoneal or infra-peritoneal. 



Calculi impacted near the pelvic brim are best approached 

 by the retro -peritoneal route (p.' 274). 



Infra-peritoneal Route. In order to obtain access to the 

 terminal part of the ureter, an oblique incision, which is directed 

 downwards and medially, is made through the lower part of 

 the anterior abdominal wall^(Fig. 71). In its medial two-thirds 

 this incision crosses the rectus muscle below the level of the 

 linea semicircularis (of Douglas). The aponeuroses of the 



