Most often, the obstruction is a blood clot that traveled from elsewhere in the body. Most commonly, this is from a deep vein thrombosis (DVT) in the legs or pelvis. Risk factors are conditions that increase the risk of clotting. This includes genetic (factor V Leiden) and acquired conditions (cancer). Trauma, surgery, and prolonged bed-rest are common risks. Covid-19 is a recent risk factor.This obstruction increases the pulmonary vascular resistance. If large enough, the clot increases the load on the right side of the heart. The right ventricle must work harder to pump blood to the lungs. With back-up of blood, the right ventricle can begin to dilate. Right heart failure can ensue, leading to shock and death.A PE is considered "massive" when it causes hypotension or shock. A submassive PE causes right heart dysfunction without hypotension. Cardiac tamponade
A pericardial effusion is fluid in the pericardial sac. When large enough, the pressure compresses the heart. This causes shock by preventing the heart from filling with blood. This is called cardiac tamponade. The chambers of the heart can collapse from this pressure. The right heart has thinner walls and collapses more easily. With less venous return, cardiac output decreases. The lack of blood flow to vital organs can cause death.Various conditions can cause a pericardial effusion. Inflammation of the pericardium is called pericarditis. This is caused by infection, renal failure or autoimmune disease. Trauma can cause blood to fill the pericardium. Cancer can also cause effusions.
Angiotensin converting enzyme inhibitors are thought to be beneficial, as they reduce intraglomerular pressure and, presumably, reduce renal tubular congestion with RBCs.Possible treatment regimens

General
Angiotensin inhibition
Reduce the risk of nephrolithiasis

Pain control
Opioid therapy
Inpatient therapy
Intravenous opioid regimen
Antiemetic drugs
Pruritus management
Maintenance therapy between pain exacerbations

Invasive therapy
Implantable drug delivery system
Surgical renal denervation
Renal autotransplantation
Nephrectomy (NOT recommended)
Other invasive therapies (but not proven effective)
Pulse radio frequency
Celiac plexus block
Intraureteric capsaicin infusionSurgery (autotransplantation) is thought by some to be of benefit in selected individuals and advocated in some centres, but usually considered the last resort.Physicians discourage surgery, as LPHS symptoms often re-occur after autotransplantation. Epidemiology
LPHS is listed as a rare disease in the US National Institute of Health Rare Diseases database. While exact numbers worldwide are not available, the primary LPHS research clinic located in Ohio has over 200 patients. In addition, several hundred other patients have been reported in one study as of 2006. The prevalence of LPHS is estimated  at about 0.012 percent, which qualifies LPHS as a rare disease (prevalence less than 0.07 percent) according to the Rare Diseases Act of 2002. Those affected are usually young, with an average age of 31 years, and 70% to 80% are women. See also
Pelvic pain

References
External links

Loin Pain - Patient UK