Making the Diagnosis of CIP
To help distinguish the patient with Chronic Intestinal Pseudo-Obstruction from the patient with mechanical obstruction, it is important to review the history (previous surgeries, the presence of adhesions, diverticula, and intestinal cancer in the family), and perform a thorough examination. Warning signs, which include weight loss, hematemesis, hematochezia, melena, obstipation, or rebound tenderness, warrant a more urgent workup and possible early surgical intervention.
Hypoactive bowel sounds may be seen in intestinal pseudo-obstruction as opposed to the high-pitched bowel sounds in mechanical obstruction. Abdominal distension and “tympany” on percussion may be seen in both disorders. Peristaltic waves are more common in mechanical obstruction.
Initially, patients should be evaluated for organic disease with laboratory tests including serum electrolytes, complete blood count, albumin, thyroid-stimulating hormone, celiac antibodies/antigens, and specialized tests to eliminate systemic diseases, including autoimmune processes, neoplastic, and endocrine disorders.
Plain Abdominal Radiograph
The initial obligatory study is a plain radiograph of the abdomen (supine, upright, and chest) to look for intestinal distension, free air, volvulus, air-fluid levels, or transition points which could identify a possible site of obstruction. CIP cannot be diagnosed if an ileus, air-fluid levels, or distended loops of bowel are not identified. In one study all 20 patients had radiological dilatation of the small intestine, usually involving the duodenal loop.
Imaging Studies
Computed tomography may identify bowel wall thickening, pneumoperitoneum, or pneumatosis intestinalis, which are all potential complications of intestinal pseudo-obstruction. Barium studies (enteroclysis or upper GI with small bowel follow-through) to examine the upper GI tract, followed by barium enema, is often required to rule out mechanical obstruction and provide evidence of intestinal dilatation secondary to pseudo-obstruction.Consideration must always be given to the risk of barium impaction should complete obstruction be present.Alternatives may include water-soluble contrast or small amounts of barium with air contrast.
Barium studies may also demonstrate a lack of peristalsis (myopathic processes) or chaotic peristalsis (neuropathic processes). An upper GI series may demonstrate isolated megaduodenum or wide-mouthed intestinal diverticula, commonly seen with myopathic processes such as scleroderma. Loss of haustral markings, a dilated colon, or a markedly dilated and redundant colon (megacolon) may be present. Endoscopic evaluation (upper endoscopy, colonoscopy, and capsule endoscopy) for masses, strictures, or physical obstruction (or lack thereof) may aid in establishing the diagnosis of CIP.