An apparatus for monitoring intra-abdominal pressure in a medical patient includes a urinary catheter connected to a urine valve having selectable communication positions between a discharge end of the urinary catheter and either a drain or a fluid source. Preferably, the urine valve has a housing adapted to resist patient discomfort from body-valve contact. A plumbing structure desirably maintains fluid supply and drain conduits in a substantially parallel arrangement to assist routing those conduits between a patient's legs. When the urine valve is oriented for communication with the fluid source, a syringe may be used to introduce a known quantity of fluid through the urine valve into the patient's bladder where the fluid's pressure can be measured. Desirably, a double check valve is included in a fluid supply path and arranged to permit repetitive operation of the syringe to introduce a bolus of fluid into the patient's bladder.