Abdominal Compartment Syndrome (ASC) is defined by an Intra Abdominal Hypertension (IAH) associated with a new organ failure. The occurrence of this syndrome is not well known in infants. Preterm birth is frequently associated with gastrointestinal complications, particularly Necrotizing Enterocolitis. In this pathology it is likely that the intra abdominal pressure (IAP) increases and can participate in the occurrence of organ failures. Newborn, in particular with digestive malformation as diaphragmatic hernias, gastroschisis, could themselves be suffering from this syndrome. It would be interesting to make early diagnosis in order to optimize the management of these children. This requires reliable measurements methods and standards. Intravesical Pressure (IVP) is the most reliable validated indirect method to measure intra-abdominal pressure. In order to measure the IVP, the bladder must contain a minimum of liquid. However, using inappropriate volumes could give erroneous IAP readings. The optimal amount of saline to inject in older children, determined from pressure-volume curves study is 1 ml/kg. In preterm and term infants, this volume appear extremely low (e.g. 0 8cc if taking a child to 800 g). The question that arises is whether this quantity is sufficient to obtain reliable and reproducible measurements of IVP in preterm and term.

Inclusion Criteria:

• Preterm or term newborn admitted in paediatric intensive care unit
• With an urethral catheter
• Consent signed by parents

Exclusion Criteria:

• Weight > 4.5 kg
• Urinary tract or bladder pathology