0521779407-14 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:16
960 Mediastinal Masses MegacolonPrognosis
■Depends on underlying histopathology
■For benign lesions, survival is normal, unless there is compression
of vital structures
■Thymoma:
➣30% recur after resection
➣Encapsulated: Normal survival
➣Invasive: 50–77% 5-y; 30–55% 10-y
■Germ cell tumors:
➣Very radio- and chemosensitive
➣Long-term survival∼80%
■Lymphoma:
➣Very radio- and chemosensitiveMEGACOLON
GEORGE TRIADAFILOPOULOS, MD
history & physical
Megacolon implies cecal dilation of more than 12 cm or sigmoid colon
dilation more than 6.5 cm. Primary megacolon is associated with neu-
rogenic dysfunction. If it is acute (Ogilvie’s syndrome) the megacolon is
a reflex response to various medical or surgical conditions. Secondary
chronic megacolon and megarectum develop later in life as a response
to chronic fecal retention. Toxic megacolon is a serious complication of
inflammatory bowel disease (IBD) or infectious colitis that is associated
with systemic toxicity. Colonic dilatation is also seen with congenital
megacolon (Hirshsprung’s disease) and chronic intestinal pseudoob-
struction, a manifestation of diffuse gastrointestinal dysmotility of var-
ious causes.Risk Factors
■Children or physically and mentally impaired elderly with longstand-
ing constipation or defecatory difficulties and fecal impaction are
particularly at risk. Megacolon may also be seen in Hirschsprung’s
disease, meningomyelocele, or spinal cord lesions. Toxic megacolon
often affects patients with IBD early in their disease. C. difficile infec-
tion, Salmonella, Shigella, Campylobacter and amebic colitis may
also be complicated by toxic megacolon. In patients with HIV infec-
tion or AIDS, cytomegalovirus (CMV) colitis is the leading cause of
toxic megacolon.