RETROPERITONEAL SUPPUEATION. 389 



and an area of dulness may be found over the ribs posteriorly, 

 owing to the upraising of the diaphragm in this region. 



The Pelvic Region is often the site of intraperitoneal abscess. 

 It may be invaded from any of the viscera which it contains. 

 It is also open to invasion from the lumbar regions as already 

 explained, and in cases of sudden perforation of the stomach 

 the great omentum may direct the stomach contents directly to 

 the pelvis. The region is accessible to examination by the 

 rectum or vagina. The proximity of the abscess to the bladder 

 may lead to painful micturition or retention of urine, and even to 

 exfoliation of parts of the mucous membrane of the bladder. Its 

 relation to the rectum may cause tenesmus. The abscess may 

 discharge into bladder or bowel. It is often shut in above by 

 matted coils of intestine and by the great omentum. 



RETROPERITONEAL SUPPURATION. 



Retroperitoneal abscesses may lie in the retroperitoneal con- 

 nective tissue or beneath the deep fascia of the abdomen. 

 Abscesses in the areolar tissue are usually derived from the 

 appendix, but may originate in the caecum, lymphatic glands or 

 the tissue around the uterus or rectum. When the appendix is 

 closely bound down to the abdominal parietes by developmental 

 or inflammatory adhesions it is in a favourable position to infect 

 the planes of connective tissue. The pus may spread freely and 

 track in various directions. Upward extension involves the 

 retroperitoneal tissue of the lumbar region, and may give rise 

 to perinephritic abscess. The posterior, non-peritoneal, surface 

 of the liver may be invaded, and even the subpleural tissue 

 giving rise to infection of the pleural sac. In other cases the 

 abscess spreads inwards towards the spine surrounding and 

 eroding the bodies of the vertebrae. - Sometimes the pus makes 

 its way along the inguinal canal or even along the femoral 

 sheath. It may invade the connective tissue planes of the 

 pelvis, and has been known to pass through the obturator 

 foramen into the buttock. Perforation of the psoas fascia may 



