|Dynamic type may become adynamic|
|Includes partial mechanical obstruction|
|Ileus and Pseudo-obstruction varieties of same thing|
|Entire intestine is affected|
|Aggravated by drugs and metabolic disturbance (hypokalemia)|
|Post severe acute illness, pneumonia, cardiac bypass, head injury|
|Mostly post abdominal surgery|
|In the main more small bowel than colon|
|In the main more colonic than small bowel|
|Gastrografin enema differentiates from mechanical colonic obstruction|
|Neostigamine may help [PSK99]|
|If neostigamine is no good try colonic decompression|
One clinician may say the patient has ileus and another pseudo-obstruction, both may be correct.
Ileus is often used to describe poor function of the intestine after abdominal surgery. The trauma and handling of the bowel causes it to cease functioning for a period. It can be difficult to differentiate post-operative ileus from a post-operative adynamic obstruction. Normally an ileus will resolve within 10 days.
Early on in intestinal obstruction the function of the bowel is increased as it tries to overcome the obstruction but later on it may `give up' and cease its efforts. Examination of the patient early on in intestinal obstruction may reveal visible peristalsis, and the bowel sounds may be markedly increased. Later on there may be no visible peristalsis and the bowel sounds become reduced. This second appearance is akin to paralytic ileus.
The term ileus is usually used for this adynamic appearance in the post operative setting. In particular if it appears that there is no great involvement of the colon on plain radiology. However, the condition affects the entire intestine.
The term pseudo-obstruction is usually used to refer to non obstruction when the main area of concern is the colon, however, the small bowel is also affected. Any acute severe illness, many drugs, and mischief in the retroperitoneum may cause a lack of motor function in the small bowel and colon. This in essence causes a functional obstruction where there is no mechanical reason (stricture etc.). This is termed Ogilvie's syndrome.5The importance of these functional problems is that they mask a real obstruction (for instance in a patient with a head injury or post cardiac bypass), they impair the digestive function of the intestine and delay the patient's recovery. If distension becomes severe, they may even perforate their colon and develop peritonitis.
Conservative treatment of non-obstructions include naso-gastric aspiration and intra-venous fluid replacement. Metabolic derangements should be corrected. Any drugs that may be contributing, in particular opiates, should be reduced or preferably withdrawn. In the ileus type pattern, if the ileus does not appear to be settling it may be wise to try a therapeutic and diagnostic Gastrografin meal with subsequent CT scanning. In the colonic pseudo-obstruction setting serial abdominal films will document the progress, if the colon continues to dilate (? to more than 12 cm) in particular if the caecum is distended, the clinician may recommend passage of a flatus tube. If this does not work try neostigamine (2 mg IV over 3-5 minutes) and failing that colonoscopic decompression. Colonoscopic decompression is associated with a perforation rate of about 3%, in this setting [Rex97]. If the patient develops peritonitis or perforates then surgical intervention is the only option, and is associated with a high mortality in frail patients with multiple co-morbidities.