What is the most likely diagnosis for a patient with flank pain, hematuria, and calcium oxalate crystals in urine?

The symptoms described—flank pain, hematuria, and the presence of calcium oxalate crystals in the urine—are indicative of renal calculi, commonly known as kidney stones. Flank pain suggests that the issue is occurring in the kidney area, while hematuria, or blood in the urine, often occurs when stones irritate the urinary tract lining or cause obstruction.

The presence of calcium oxalate crystals strongly supports this diagnosis because calcium oxalate is the most common type of urinary stone. These crystals are typically formed when there is an excess of calcium in the urine or when oxalate levels are elevated. The combination of these symptoms—especially the type of crystals identified—clearly points toward the formation of kidney stones rather than other potential diagnoses.

Other diagnoses, while they may present with similar symptoms, do not align as closely with the combination of flank pain, hematuria, and specific crystal formation. Conditions like acute kidney injury, kidney infections, or bladder cancer would likely present with additional or different clinical features that are not necessarily consistent with this specific presentation. Thus, the most likely diagnosis based on the provided symptoms is renal calculi.