What sign may indicate thrombophlebitis?

A hard, red swelling in the posterior calf is indicative of thrombophlebitis because this condition involves inflammation of the veins, often in the legs, typically due to a blood clot. The classic signs of thrombophlebitis include warmth, redness, swelling, and tenderness at the site of the affected vein. The posterior calf is a common location for this type of inflammation because many superficial veins located there are susceptible to clot formation and irritation.

In contrast, other symptoms such as shortness of breath can relate to different conditions, particularly those affecting the lungs, and while they may occur in cases of deep vein thrombosis (DVT) that may lead to pulmonary embolism, they do not specifically point to thrombophlebitis. Pain in the lower abdomen could suggest various issues unrelated to clot formation in the veins of the leg. An increased heart rate can be a response to pain or a range of other medical conditions but isn't a direct indication of thrombophlebitis. Thus, the localized signs of swelling, hardness, and redness specifically highlight the presence of thrombophlebitis.