What condition presents with abdominal pain and a rigid abdomen?

The condition characterized by abdominal pain and a rigid abdomen is abruptio placentae. This condition occurs when the placenta detaches from the uterine wall before delivery, leading to significant bleeding and potential complications for both the mother and the fetus. The detachment causes intense abdominal pain and can result in a tight or rigid abdomen due to the accumulation of blood and muscle spasm in response to injury.

When evaluating this condition, abdominal rigidity can be associated with the body's response to internal bleeding, as the muscles may tense in reaction to pain or the physical distress caused by the separation of the placenta. In cases of abruptio placentae, this may also include symptoms like vaginal bleeding and fetal distress, depending on the severity of the detachment.

The other conditions mentioned generally present with different signs or symptoms that do not align as closely with the combination of abdominal pain and a rigid abdomen. For example, pyelonephritis typically involves flank pain and fever, while ectopic pregnancy may feature unilateral pain and potentially shoulder pain due to diaphragm irritation. Placenta previa usually presents with painless vaginal bleeding rather than abdominal rigidity. Understanding these distinctions helps clarify why abruptio placentae is the most appropriate condition associated with the given symptoms.