What is the most likely cause of severe right-sided flank pain in a patient with autosomal dominant polycystic kidney disease?

In patients with autosomal dominant polycystic kidney disease (ADPKD), severe right-sided flank pain can often be attributed to cyst hemorrhage. This condition is characterized by the formation of numerous cysts in the kidneys, which can become large and distended over time. When these cysts rupture or bleed into themselves, it can cause significant pain due to irritation of surrounding tissues and the activation of pain receptors in the area.

Cyst hemorrhage is particularly likely to occur with larger cysts, especially if there is an increase in intrarenal pressure, trauma, or even spontaneous rupture. Clinicians often find this mechanism significant in the differential diagnosis of flank pain in patients with ADPKD.

While cyst infection, cyst torsion, and renal calculus can also lead to flank pain, they are less common in the context of ADPKD. Cyst infections, while possible, typically present with fever and systemic symptoms indicating an infectious process. Cyst torsion is a rare occurrence, and although it could cause acute pain, it is less frequent than hemorrhage. Renal calculi can cause flank pain, but their association with ADPKD is not as direct as cyst hemorrhage, which is often a more immediate complication of the