Bruised kidneys (sometimes referred to renal trauma) typically result from blunt forces sustained from automobile accidents, contact-sport injuries or falls. Treatment of renal trauma depends on the seriousness of the injury, and bruised kidneys will most likely heal on their own without medical treatment. The Merck Manual indicates that even patients with very serious kidney injuries will recover if the patient receives a correct diagnosis followed by proper treatment in a timely manner.
Doctors generally consider a bruise to the kidney as a mild injury compared with more serious renal injuries such as lacerations or torn attachments. Primary symptoms of kidney injury include abdominal pain and blood in the urine. According to the Merck Manual, most cases of blood in the urine involve some form of kidney injury. If only trace amounts of blood appear in the urine, the patient most likely has a minor bruise, and the injury will typically heal on its own without treatment. Larger amounts of blood and acute upper abdominal pain typically indicate a more serious injury. Bruising does not usually lead to more serious complications, since the kidney has the ability to heal on its own and the injury will not require surgical intrusions that could lead to infections.
A 2009 study by the Universidad del Valle in Cali, Colombia, titled "Clinical Management of Renal Injuries at Hospital Universitario Del Valle" explored the types of treatments that patients diagnosed with renal trauma received. Of the 106 patients evaluated, the doctors applied conservative treatment to most of the cases considered minor in severity, which includes bruising. (Conservative treatment involves therapies that allow the kidney to heal on its own, such as controlling the intake of fluids and bed rest.) Only very serious kidney injuries such as lacerations and torn attachments required surgery, and the study found that surgery in itself came with additional risks and complications.
A study by the Cairo University Pediatric Hospital in Egypt titled "Management of Major Blunt Pediatric Renal Trauma" explored the long-term effects of managing kidney injuries in children ranging from infants to 14-year-olds. For the group that sustained less-serious injuries (including kidney bruising that resulted from falls and automobile accidents), the researchers deemed the outcome "excellent." Only patients who had severe injuries beyond bruising or who had pre-existing renal conditions required surgery and suffered serious complications, leading the researchers to conclude that in most cases of minor renal injuries such as bruising, the kidneys will recover in full over the long term with nonoperative management.