Clinical scenario: cystic fibrosis/ abdominal pain/ billious vomiting
A 13-year-old boy with cystic fibrosis and pancreatic insufficiency is admitted with a 24-hour history of progressively worsening colicky abdominal pain, abdominal distension, bilious vomiting, and constipation. He has had two similar episodes over the past year that resolved with medical treatment. On examination, he is mildly dehydrated. His abdomen is distended, with tenderness and a palpable mass in the right iliac fossa. There is no rebound tenderness or guarding, and bowel sounds are exaggerated.
What is the most likely diagnosis?
A. Acute appendicitis
B. Distal intestinal obstruction syndrome
C. Intussusception
D. Small bowel volvulus
E. Toxic megacolon
Correct answer & Explanation:
Correct Answer: B. Distal intestinal obstruction syndrome
Explanation: cystic fibrosis/ distal intestinal obstruction
This child has distal intestinal obstruction syndrome (DIOS), a well-recognized gastrointestinal complication of cystic fibrosis, particularly in older children and adolescents with pancreatic insufficiency.
The diagnosis is suggested by:
- Known cystic fibrosis
- Pancreatic insufficiency
- Acute colicky abdominal pain
- Bilious vomiting
- Right lower quadrant mass
- Radiographic evidence of fecal impaction in the terminal ileum and cecum
DIOS results from the accumulation of thick, inspissated intestinal contents at the ileocecal region, causing partial or complete bowel obstruction.
Why the other options are incorrect
A. Acute appendicitis
May present with right lower quadrant pain but usually does not produce fecal loading of the terminal ileum or the typical obstructive picture seen in DIOS.
B. Distal intestinal obstruction syndrome
Correct. This is the classic presentation in an older child with cystic fibrosis and pancreatic insufficiency.
C. Intussusception
Can occur in cystic fibrosis but is less common and usually presents with intermittent severe pain, a sausage-shaped abdominal mass, and sometimes “currant jelly” stools.
D. Meconium ileus
Occurs in the neonatal period and is often the first manifestation of cystic fibrosis, not in a 12-year-old.
E. Volvulus
Typically presents with rapidly progressive obstruction and signs of bowel ischemia; the imaging findings are not typical.
Learning Point
Distal intestinal obstruction syndrome (DIOS) is a characteristic complication of cystic fibrosis in older children and adolescents. It should be suspected in any patient with cystic fibrosis who develops:
- Acute abdominal pain
- Bilious vomiting
- Right lower quadrant mass
- Features of small bowel obstruction
It is distinguished from meconium ileus, which presents in the neonatal period.
