What is the cause of "shoulder tip" pain in relation to an ectopic pregnancy?

Shoulder tip pain in the context of an ectopic pregnancy is primarily caused by blood from a ruptured ectopic pregnancy pressing on the diaphragm. When there is internal bleeding due to a ruptured ectopic pregnancy, the blood can irritate the diaphragm because of its anatomical proximity. The diaphragm is innervated by the phrenic nerve, which also supplies sensation to the shoulder area. As a result, this irritation can manifest as referred pain to the shoulder, known as "Kehr’s sign," which is classically associated with internal bleeding in the abdominal cavity.

Understanding this mechanism is crucial in the clinical assessment of suspected ectopic pregnancies, as shoulder tip pain can serve as a key indicator for healthcare professionals to consider potential complications such as rupture or significant internal bleeding.