Persistent and chronic diarrhoea — formative SAQs

SAQ 1 — The thriving toddler with loose stools (20 marks, ~15 minutes)

A 2-year-old is brought in by anxious parents with a three-month history of four to six loose stools a day that often contain recognisable undigested food such as peas and carrots. The first stool of the day is the largest and they become looser as the day goes on. There is no blood and no night-time diarrhoea. The child is active and well, and the growth chart shows steady tracking along the 50th centile for weight and height. The parents have switched to a low-fat diet and the child drinks about a litre of fruit juice and squash a day. ^[4]

Questions

1. Give the most likely diagnosis and the three features of this history that support it. (5 marks) ^[4]
2. Explain the two dietary contributors and the physiology by which each produces loose stools. (5 marks) ^[5]
3. State what investigations, if any, you would perform and justify your answer. (4 marks) ^[1]
4. Outline your management and the advice you would give the parents. (4 marks) ^[4]
5. State the features that, if present, would change your diagnosis and prompt investigation. (2 marks) ^[1]

Model answer (must-hit)

1. The most likely diagnosis is chronic nonspecific diarrhoea of childhood (toddler's diarrhoea). The three supporting features are the normal growth and thriving state of the child, the presence of recognisable undigested food in the stool with the stools becoming looser through the day, and the complete absence of red flags — no blood, no weight loss and no nocturnal diarrhoea. It is a positive clinical diagnosis in a well, growing child. ^[4]
2. The first contributor is the excessive fruit juice and squash: the fructose and sorbitol they contain exceed the small bowel's absorptive capacity, remain in the lumen and act as an osmotic load that draws water into the colon and produces loose stools. The second is the low-fat diet the parents have adopted, which paradoxically worsens the problem by speeding intestinal transit and reducing the contact time for water absorption; adequate dietary fat slows transit and firms the stool. ^{[5] [4]}
3. In a thriving child with this classic history, no investigations are required. The diagnosis is clinical, and a battery of tests risks harm and anxiety without benefit. A three-day stool and food diary to quantify the juice and fat intake is the most useful step, and coeliac serology may be considered if there is any doubt, taken while the child is still eating gluten. ^{[1] [6]}
4. Management is dietary and reassuring: reduce the fruit juice and sorbitol-containing drinks, ensure an adequate normal fat intake, avoid the counterproductive low-fat diet, and maintain a balanced fibre and fluid intake. Give firm reassurance that the child is well, is growing normally and will grow out of the condition, usually by school age, and that no medication or antidiarrhoeal is needed. Arrange follow-up to confirm continued normal growth. ^[4]
5. Any of blood in the stool, weight loss or faltering growth, nocturnal diarrhoea that wakes the child, dehydration, or onset in early infancy would exclude toddler's diarrhoea and mandate investigation for an organic cause. ^[1]