What condition is indicated by flank pain accompanied by gross hematuria?

The presence of flank pain accompanied by gross hematuria is most commonly indicative of nephrolithiasis, or kidney stones. This condition occurs when minerals and salts in urine crystallize to form stones, which can cause obstruction in the urinary tract. When a stone passes, it can lead to intense pain in the flank area as well as blood in the urine due to irritation of the lining of the urinary tract.

Flank pain and hematuria are classic symptoms, as the movement of the stone may trigger spasms in the ureters, and the resulting friction can cause bleeding. This is why nephrolithiasis aligns well with the symptoms described in the question. Other conditions may present with flank pain and hematuria, but the combination of acute, sharp flank pain and the sudden appearance of blood in the urine is particularly characteristic of kidney stones.