Correct Answer: D. Distal intestinal obstruction
The clinical presentation—recurrent pulmonary infections, bulky greasy stools (steatorrhea), and quantitative stool fat >10 g/day—is pathognomonic for cystic fibrosis (CF). In CF, pancreatic insufficiency leads to malabsorption of fat and fat-soluble vitamins. The key discriminator for this question is recognizing that distal intestinal obstruction syndrome (DIOS) is a characteristic GI complication of CF in children, occurring in 5–15% of CF patients. DIOS results from inspissated (thick, sticky) intestinal secretions mixed with incompletely digested fat and protein, forming a putty-like mass that obstructs the terminal ileum and proximal colon. This occurs because CF patients have abnormally thick, dehydrated intestinal secretions due to defective CFTR-mediated chloride and water secretion. DIOS typically presents with acute abdominal pain, abdominal distension, and palpable abdominal mass (the "meconium ileus equivalent" in older children). It is a well-recognized complication in Indian CF cohorts and is managed with N-acetylcysteine, polyethylene glycol solutions, or rarely surgical intervention. The other options represent either non-specific malabsorption findings or complications that do not specifically characterize CF.
Why the other options are wrong
A. Protein losing enteropathy — While CF can cause mild protein malabsorption due to pancreatic insufficiency, protein-losing enteropathy (PLE) is not a characteristic feature of CF. PLE is seen in conditions with mucosal inflammation or lymphatic obstruction (e.g., Crohn's disease, Whipple's disease, lymphangiectasia). CF primarily causes fat and fat-soluble vitamin malabsorption, not protein loss. This is a distractor that confuses malabsorption with protein loss. B. Rectal prolapse occurs after treatment — Rectal prolapse can occur in CF due to chronic malnutrition and straining, but it is not a post-treatment phenomenon—it occurs during active disease and may improve with nutritional rehabilitation. The statement 'after treatment' is misleading; prolapse is a complication of untreated CF, not a consequence of starting pancreatic enzyme replacement. This option misrepresents the temporal relationship and is a semantic trap. C. Hypernatremia — CF causes hyponatremia (low serum sodium) due to excessive salt loss in sweat, especially in hot climates—a well-known Indian clinical context. Hypernatremia is not a feature of CF; in fact, CF patients are at risk of hyponatremic dehydration. This is a direct factual error and a classic NBE trap pairing CF with the opposite electrolyte disturbance.
High-Yield Facts
- Stool fat >7 g/day defines steatorrhea; CF typically presents with >10 g/day due to pancreatic insufficiency.
- Distal intestinal obstruction syndrome (DIOS) is the CF equivalent of meconium ileus in older children, caused by inspissated secretions in the terminal ileum.
- CFTR mutation impairs chloride secretion → thick, dehydrated mucus in lungs (recurrent infections) and GI tract (obstruction).
- Hyponatremia and hypokalemia (not hypernatremia) occur in CF due to excessive sweat salt loss, especially in Indian tropical climate.
- Pancreatic enzyme replacement + fat-soluble vitamin supplementation (A, D, E, K) is the cornerstone of CF management in India.
Mnemonics
CF Complications: DIOS Distal Intestinal Obstruction Syndrome = meconium ileus equivalent in older CF children; thick, putty-like secretions block terminal ileum. Treat with N-acetylcysteine or PEG solutions. CF Triad (Indian context) Recurrent lung infections (thick airway mucus) + Steatorrhea (pancreatic insufficiency) + Failure to thrive (malabsorption). Remember: Salty sweat (hyponatremia risk in heat) is the diagnostic clue.
NBE Trap
NBE pairs CF with hypernatremia (opposite of true hyponatremia) and protein-losing enteropathy (confusing fat malabsorption with protein loss) to trap students who memorize malabsorption generically rather than understanding CF's specific pathophysiology. The "rectal prolapse after treatment" option exploits temporal confusion about when CF complications occur.
Clinical Pearl
In Indian pediatric practice, CF is often diagnosed late because neonatal screening is not universal; the combination of recurrent lower respiratory tract infections with bulky stools in a child should immediately trigger CF screening (sweat chloride test). DIOS presenting as acute abdominal pain in a known CF patient is a medical emergency that mimics appendicitis—awareness prevents unnecessary surgery.
_Reference: Harrison Ch. 340 (Cystic Fibrosis); OP Ghai Ch. 9 (Pediatric GI disorders); KD Tripathi Ch. 45 (Pancreatic enzymes and malabsorption)_