The costodiaphragmatic recess, also called the costophrenic recess or phrenicocostal sinus,[1] is a potential space in the pleural cavity, at the posterior-most tips of the cavity, located at the junction of the costal pleura and diaphragmatic pleura (in the costophrenic angle). It measures approximately 5 cm vertically and extends from the eighth to the tenth rib along the mid-axillary line.