A retroperitoneal hematoma is basically a deep bruise behind the abdominal lining. Blood vessels tear, fluid collects, and the space fills silently. Most people feel nothing at first, then vague aches appear. The list below keeps things simple. Early warning flares A dull throb in the flank or low back is common. It can wrap forward into the groin. Sitting upright may ease it slightly, while deep breaths make it worse. Some individuals notice mild nausea or a full feeling long before any skin changes show. As the puddle grows The belly bloats, jeans feel tight, yet weight stays stable.... Learn more