Which condition is best explained by severe abdominal pain that originates in the flank and radiates to the groin, accompanied by nausea and tenderness in the left flank?

The condition best explained by severe abdominal pain that originates in the flank and radiates to the groin, accompanied by nausea and tenderness in the left flank, is ureteral calculus.

This presentation is characteristic of renal colic, which occurs when a stone obstructs the passage of urine through the urinary tract. The pain typically starts in the flank, where the kidney is located, and can travel along the path of the ureter to the groin as the stone moves. This radiating pain, combined with symptoms such as nausea, highlights the intense visceral pain often associated with kidney stones. Tenderness in the flank further supports the likelihood of a stone in that area causing irritation and pain.

Other conditions, such as colon neoplasm or diverticulitis, present differently. Colon neoplasms may cause abdominal pain and changes in bowel habits rather than the sharp, radiating pain typical of urolithiasis. Diverticulitis is associated with left lower quadrant pain and may also include fever and changes in bowel habits, not necessarily the characteristic flank-to-groin pain. Renal infarction could present similarly but is less common and would typically entail a more systemic presentation, such as hematuria or a significant acute change in renal function.