We present a 12-yr-old boy who received a combined liver–pancreas small bowel transplantation at the age of two. The post-operative period was complicated by wound closure problems resulting in a large asymptomatic abdominal wall defect. Further follow-up was uneventful, with the exception of new onset growth failure not explained by extensive routine investigations. An indirect calorimetry was performed. The resting energy expenditure (REE) was significantly increased (126% of predicted), demanding a daily caloric intake of 123 kcal/kg body weight (normal for age: 80 kcal/kg). In the absence of classic reasons for increased REE, a thermal camera revealed increased dermal heat loss at the abdominal wall defect (estimated surplus in energy loss of at least 29 kcal/day: 10.4% of the elevated REE). In addition, we found lower total lung capacity due to impaired abdominal breathing. In the exploration of growth failure in children after (ITx), increased REE must be taken into account. Indirect calorimetry can serve as a valuable diagnostic tool for evaluating individual energy requirements and nutritional support. In this child, exaggerated heat loss through an aberrant abdominal wall could be a potential important contributor to the patient's increased energy requirements.