354 THE ABDOMEN AND PELVIS 



and third parts of the duodenum ; between the latter and the 

 root of the mesentery, the right colic, spermatic, and ileo-colic 

 vessels cross its anterior surface and separate it from the 

 peritoneum (Fig. 107). On account of these relations the 

 lumbo-ilio-inguinal route (p. 274) for exposure of the ureter is 

 to be preferred to the trans-peritoneal route. 



On the left side, the ureter lies behind the peritoneum of the 

 left infra-colic compartment, and as it enters the pelvis it is 

 crossed by the pelvic meso-colon. The left colic, spermatic, 

 and sigmoid vessels cross its anterior surface (Fig. 107). 



The blood-supply of the ureter is derived from the renal, 

 spermatic, superior, and inferior vesical arteries. These branches 

 anastomose freely with one another, and as a result large segments 

 of the ureter can be freed without any subsequent sloughing. 



The nerve-supply of the renal pelvis and the ureter is derived 

 from the eleventh and twelfth thoracic and the first and second 

 lumbar segments. In renal colic strong waves of contraction 

 pass down the ureter, and the pain is successively referred to 

 the skin areas supplied by these segments. When the calculus 

 is situated in the renal pelvis, the pain begins in the loin in the 

 area supplied by T. n, and passes obliquely round the lower 

 part of the abdominal wall affecting the areas supplied by 

 T. 12 and L. i (ilio-hypogastric). Sometimes the pain shoots 

 into the testis, and testicular hypersesthesia may persist after 

 the attack. This is due to the sensory branch which the external 

 spermatic (genital branch of genito-crural) nerve (L. i and 2) 

 gives to the tunica vaginalis testis (Mackenzie). At the same 

 time, the afferent impulses from the strongly contracting ureter 

 may excite a viscero-motor reflex (p. 251). The lower portions 

 of the lateral abdominal muscles become rigid, and the cremaster 

 muscle may contract and draw the testis up towards the 

 subcutaneous inguinal ring. All the muscles affected are 

 innervated from the same segments as supply the skin areas 

 over which the pain is felt. The viscero-sensory reflex may 

 also affect the lumbo-inguinal nerve (crural branch of genito- 

 crural) and the posterior rami of the upper lumbar nerves so 

 that pain is experienced in the front of the thigh and in the 

 buttock. 



