醫學筆記匯整 ED Notes

Megacolon

Cecal dilatation > the dimension of 12 cm
sigmoid colon dilatation > 6.5 cm
measured at the pelvic brim.

Dilatation of the colon can be broadly categorized into 3 clinical entities : 

 Acute megacolon (Ogilvie's syndrome) 
The colonic dilatation is attributed to a sympathetically mediated reflex response
to a number of serious medical or surgical conditions in elderly patients.

The initial tasks are to exclude mechanical obstruction
(with a hypaque enema)
to discontinue enabling medications
to correct metabolic disturbances.

Dilatation of the cecum > 12 cm diameter is a cause for grave concern.
The rectum should be decompressed by indwelling tube and tap water enemas.

Intravenous neostigmine is generally effective and safe
for patients with colonic distention
unresponsive to such conservative therapies.

Endoscopic decompression is necessary for patients
who do not respond to, or relapse after neostigmine,
or in whom neostigmine is contraindicated.

Signs of peritonitis may imply colonic perforation,
and surgery will be needed, often on an emergent basis. 

 Chronic megacolon 
It may be congenital (due to Hirschsprung's disease)
or may represent the end-stage of any form of refractory constipation
(slow transit constipation or pelvic floor dysfunction).

The initial treatment for Hirschsprung's disease is surgery,
while pelvic floor dysfunction and encopresis respond to biofeedback therapy.

In chronic idiopathic megacolon, medical measures,
such as colonic evacuation with enemas,
fiber supplementation, and laxatives may suffice.
If severe motor dysfunction is confined to the colon,
a subtotal colectomy with an ileorectal anastomosis,
or an ileostomy may occasionally be necessary.

 Toxic megacolon : 
Acute colonic distension
secondary to an identifiable inflammation of the colon
Therapy is directed toward specific treatment for the underlying disorder,
inflammatory bowel disease, or infectious colitis.
Bowel rest and close monitoring of the clinical status is vital.
Colectomy may be needed under emergency circumstances. 

* Accompanied by

• Abdominal distension (bloating)
• Fever
• Abdomen pain
• Shock
• Leukocytosis

* 是 Inflammatory bowel disease, infectious colitis 的 complication 
  ( 較常見於 UC )

The colon (typically transverse colon) becomes dilated to at least 6 cm
There is additional loss of haustral markings,
with pseudopolyps often extending into the lumen.
Thumbprinting from mucosal oedema may be present.

Thumbprinting sign 代表的就是 wall 腫, non specific 

- Ischemic bowel
- Inflammatory bowel