Introduction:Solidification of enteral nutrition may cause gastrointestinal obstruction, with severe complications. The effect of the composition of enteral nutrition on the tendency of casein to coagulate is increasingly acknowledged and new formulas may prevent solidification. To recognize patients in need of specific enteral nutrition, we have to identify the clinical risk factors for the development of gastrointestinal obstruction by the solidification of enteral nutrition. Materials and methods:The 58 cases summarized in this review were identified through a PubMed search. Results:Critically ill patients have several risk factors, including impaired digestion, and they are treated with medication that interferes with gastrointestinal function. Surgery of the upper gastrointestinal tract is thought to be the most important risk factor, leading to changes in both the anatomical structure and neurohormonal functioning of the gastrointestinal tract, and to altered secretion of digestive enzymes. Conclusions:Awareness of risk factors in critically ill patients may help intensivists and surgeons take appropriate measures to prevent this complication. Critically ill patients with impaired digestion (e.g. after Whipple surgery) should be considered for alternative enteral nutrition formulas with noncoagulating proteins or hydrolyzed proteins.