Distal intestinal obstruction syndrome (DIOS), formerly known as meconium ileus equivalent, is one of the many abdominal manifestations of cystic fibrosis. In older children or young adults with cystic fibrosis, the distal small bowel may become obstructed with a mucofaeculent material in the distal ileum and right colon.

Epidemiology

Distal intestinal obstruction syndrome is a common gastrointestinal complication of cystic fibrosis and occurs in 10-15% of patients, although the incidence is said to have decreased with the administration of microsphere pancreatic enzymes ². Prevalence is highest in the 2^nd and 3^rd decades of life ².

Risk factors

Risk factors include ⁵:

• poor adherence with pancreatic enzyme replacement therapy

• change of diet or reduced oral intake

• dehydration

• severe cystic fibrosis phenotype (e.g. homozygous F508del-CFTR mutation)

• previous abdominal surgery

• use of anticholinergic drugs

• use of opioid drugs

• known intestinal dysmotility

• previous meconium ileus as an infant

• following solid organ (e.g. lung) transplantation 

Clinical presentation

Clinical manifestations of distal intestinal obstruction syndrome include ³:

• abdominal pain: recurrent bouts of colicky abdominal pain

• palpable cecal masses that may pass spontaneously

• abdominal distention and flatulence are common

Clinical findings may mimic those of appendicitis or partial intestinal obstruction due to stricture or adhesions from previous bowel surgery. Despite the common distension of the appendix by inspissated secretions, the reported prevalence of acute appendicitis in cystic fibrosis patients is lower than that in the general population.

Pathology

Pathologic mechanisms for this syndrome include inspissated intestinal secretions and pancreatic insufficiency, undigested food residue, disordered intestinal motility, fecal stasis, and dehydration.

Radiographic features

Plain radiograph

• features of small bowel obstruction

• bubbly soft tissue mass in the right lower quadrant

Fluoroscopy

Water soluble contrast enema

• may help to find the level of obstruction

• aids in treatment/reduction of obstruction

CT

• typically seen to affect the right colon

• colonic wall thickening

• mural striation

• mesenteric soft-tissue infiltration

• increased pericolonic fat

• intussusception may be a complication

• the appendix is routinely distended (>6 mm) in the absence of appendicitis due to mucoid impaction, and therefore the diagnosis of appendicitis should not be made unless secondary signs are present

Treatment and prognosis

Medical management is the mainstay, with surgery only being a last resort. Treatment options include:

• adequate hydration

• aperients, including water-soluble (e.g. Gastrografin) contrast enemas which result in an osmotic influx of water into the lumen of the bowel ⁵

• intestinal lavage is reserved for recurrent but not complete obstruction, the aim is to wash out the accumulated secretions

• colonoscopy is rarely necessary

• surgical decompression if conservative management fails

Differential diagnosis

Small bowel obstruction from other causes including:

• intussusception

• adhesions from previous surgery

• hernias

• volvulus