Help! doctors/hospital unable to diagnose extreme abdominal pain

I appreciate any help/pointers that anyone can provide. I research daily and beg for tests to rule out/in issues. My 70-year-old sister has had extreme abdominal pain for months and doctors/hospitals have been unable to diagnose the issue.

70-year-old female with severe stomach pain – sharp pain in lower right abdomen and dull pain across the abdomen. Desperate for answer/diagnosis since she screams with pain each time she exerts herself and hospitals/doctors seen have no answer.
Symptoms started months ago, paired with severe headaches. Initially, both stomach/head pain occurred upon exertion (walking to the bathroom, etc.) and resolved ~ 15 minutes after resting. The thought was that the stomach/head pain was connected. Over time, the headaches have not been as frequent, and do not always occur in unison with the stomach pain. I’ve researched and researched, and have brought her to the ED (emergency department) and to doctors & hospitals for various tests, but no one has an answer.

Medical background:
• Patient has dementia and is unable to provide details on pain/illness (dementia since April 2025 when fully functioning at hospital entrance, but zombie by next morning. Diltiazem prescribed by PCP is culprit).
• Patient has bradycardia (since April 2025)
• Patient has high blood pressure (or, has had high blood pressure…it is currently 110s-120s/high 60s-mid 70s). Not currently giving patient BP meds (Lisinopril 5MG due to low BP which was 90s/high 50s last week)
• Patient is on Eliquis due to prior saddle PE (prescription for uterine fibroids tied to issue) and recurring DVT.
• Patient uses walker (started with cane, then walker ~ 2 years ago. I suspect pulmonary issues due to lack of oxygen prior to PE and while seen regularly by PCP/gyno. Desperately trying to schedule pulmonary consult to prevent further decline; Boston hospitals booking 6-9 months out).
• Patient has implanted loop recorder for sick sinus/bradycardia. Has often felt lightheaded “I think I’m going to pass out”. Messaged electrophysiologist.
• Patient just finished meds for UTI (3rd in 6 months). This time, the UTI showed > 100,000 ecoli

Tests/visits done to try to rule out related medical issues:
• NC Myocardial Perfusion Pharmacologic Stress (mobility issues prevent typical stress test). This test was completed while hospitalized. She threw up during and after the test. Hospital said there was no ischemia. Some notes from test:
“A pharmacological stress test was performed using regadenoson. Patient experienced dyspnea, flushing, headaches and nausea with the pharmacologic agent. Nonspecific ST abnormalities noted on ECG post regadenoson administration not meeting diagnostic criteria for ischemia”

• MRI – neuro (headache) doctor we met with [virtually] days before hospitalization suspected a spinal leak. MRI with contrast ruled this out. This test was completed while hospitalized.
Hospital discharged patient “we don’t always find the cause”

• MRA – outpatient test ordered by neuro headache doctor ruled out ischemia; identified hypoplastic right cerebral artery

• CTA with contrast – outpatient test ordered by general surgery/hernia PA after meeting to discuss possible relation to patient’s umbilical or hiatal hernia. Showed no ischemia or abdominal wall thickening. I note the wall thickening since I suspected bowel obstruction from possible hysterectomy scar tissue.

• Umbilical/hiatal hernias – met with PA regarding hernias. PA said neither are responsible for the pain as both are small and would not raise the pain to the current level. PA ordered CTA.

• Gastroenterology – met with gastroenterologist who asked a bunch of questions, had no answers, and scheduled follow up appointment 6 months out.