Kidney bruise: symptoms & treatment of a bruised kidney

Compared to many other kidney diseases, which can sometimes take on life-threatening proportions, a kidney bruise or contusion in most cases means only mild lesions that can be resolved without complications with appropriate treatment measures. However, there are exceptions where the contusion causes more serious damage to the kidney. For this reason, kidney bruises, regardless of their suspected severity, should always be examined by a doctor. T he treatment of a bruised kidney depends on the cause and severity, but in many cases consists of rest, sufficient fluids, use of painkillers and/or surgery. The prognosis is usually favorable. Timely diagnosis and treatment is important to prevent complications.

  • Kidneys
  • What is a kidney bruise?
  • Symptoms of a bruised kidney
  • Phenomena
  • Flank pain
  • Blood in the urine
  • Shock
  • Classification by severity
  • Grade I renal contusion
  • Grade II renal contusion
  • Grade III renal contusion
  • Grade IV renal contusion
  • Grade V renal contusion
  • Causes of a kidney bruise
  • Examination and diagnosis
  • Interview and physical examination
  • Follow-up research
  • Treatment of a kidney bruise
  • Mild kidney contusion
  • Severe kidney contusion
  • Complications
  • Prognosis


Location of the kidneys and bladder / Source: Nerthuz/


The kidneys are essential for metabolism. Not only do they regulate the body’s water balance by producing urine necessary for natural drainage, they also use it to remove harmful toxins from the body. In addition, remnants of useful substances are also absorbed in the kidneys, so that the metabolism ensures the best possible use of nutrients. The kidneys are even involved in the formation of blood and regulating blood pressure. The excretion of fluid affects blood volume, which also regulates the pressure in the blood vessels. In addition, the kidneys also produce hormones such as erythropoietin, which acts on the bone marrow where it stimulates the production of red blood cells.
The kidneys are located high in the abdominal cavity, behind the peritoneum. They are protected both from the front by the numerous abdominal organs and from the back by the spine, ribs and the strong muscles of the back muscles and they are well fixed. Due to their location, the kidneys are rarely affected by injury unless they are struck by violent external trauma. And this is exactly where kidney contusion has its origins. A kidney bruise is usually the result of an accident. Medically speaking, kidney bruises are classified as so-called kidney trauma.

What is a kidney bruise?

A renal contusion is an injury to one or both kidneys caused by blunt force trauma without directly destroying tissue in the organ. A kidney contusion is considered a kidney trauma. Kidney trauma is blunt in roughly 9095% of cases and penetrating in 510%.

Symptoms of a bruised kidney


The main symptoms of a bruised kidney are the typical bruise (hematoma) and severe flank pain in the affected kidney area. The bruise may also be associated with typical injury symptoms, some of which can be easily seen or felt from the outside, including:

  • external bleeding (if there is a wound)
  • pressure pain in the area of the bruise
  • becoming warm in the affected area
  • blue discoloration under the skin
  • redness
  • swelling


Flank pain

Flank pain is usually described by people affected by a bruised kidney as dull and piercing, but can also be stabbing. The pain is usually localized on one side, related to the bruised kidney, possibly radiating to other parts of the back and abdomen. As a result, it often happens that those affected go to their doctor with abdominal pain or back pain without realizing that the pain is coming from their kidney.
Flank pain does not necessarily have to occur immediately after the event, but can also occur later. Because the kidneys are partially protected by the ribs and also have a connective tissue capsule and a fat pad, it can take some time before the tensions in the kidney capsule caused by the ruptured blood vessels become so great that they lead to pain. For this reason, pain in the side that only occurs later after an accident must also be taken into account. A typical scenario here is a mild rear-end collision, which initially appears to have no consequences for those involved in the accident and which only causes severe flank pain one or two days later, indicating kidney trauma.

Blood in the urine

Another symptom that may occur with a kidney bruise is blood in the urine (hematuria). This symptom occurs mainly in fourth and fifth degree renal contusions and is due to the job of the kidneys to filter the blood flowing through them by removing excess body water and waste products from the blood. In the case of renal contusion, which is associated with deeper injuries to the kidneys, there are varying degrees of minor or major bleeding in the renal corpuscles or tubules. If the ureters are also involved, the leaked blood can enter directly into the draining ureters and discolor the urine.
Due to the filter function in the renal tubules, the bleeding is often not clearly visible to the eye, as the red blood cells are usually returned to the bloodstream here. Even small amounts of blood are sometimes not so clearly visible in the urine. In such cases it is called microscopic hematuria, which can only be detected by laboratory tests (urinalysis) due to the small amount of blood. However, the situation is different in case of bleeding in the urinary tract. The urine is no longer filtered here, which is why the blood in the urine or the associated red discoloration of the urine can usually be seen with the naked eye. Medically, this form of hematuria is also called macroscopic hematuria.
The amount of blood found in the urine does not always provide information about the extent of the damage, but it does serve as a criterion for the healing process for the treating physician.


If there is heavy internal bleeding or if the person involved suffers shock, a serious kidney contusion as a result of an accident quickly escalates into a life-threatening situation. Quick intervention by medical staff is necessary. Shock due to kidney trauma can lead to the following symptoms:

  • decreased consciousness (restlessness, confusion, drowsiness),
  • pale skin
  • drop in blood pressure (hypotension)
  • cold sweat
  • fast, flat pulse (tachycardia)


Classification by severity

In general, kidney injuries account for only about two percent of all injuries in daily life. However , if the abdominal and pelvic area is affected by external violence (for example, due to a traffic accident), the risk of kidney involvement increases to approximately 35 percent. Depending on how severe the trauma in the kidney area was, a kidney contusion can be more or less dangerous. Different degrees of severity are distinguished.

Grade I renal contusion

More than two-thirds of all kidney bruises are first-degree bruises, which involve a minor bruise and not a serious injury. Kidney bruises of this kind are therefore not dangerous, as the bruise is limited to the connective tissue capsule that surrounds the kidney. The renal corpuscles and tubules are not damaged.

Grade II renal contusion

A second-degree renal contusion is accompanied by additional damage to the parenchyma or renal gland tissue, even though this is still relatively mild in a second-degree noncontusion. This is often a crack of less than a centimeter. The injury is therefore largely harmless and can be easily resolved with appropriate treatment. In a grade II renal contusion, the hematoma may enlarge outside the connective tissue capsule.

Grade III renal contusion

In the case of a third-degree renal contusion, the parenchymal tear is considerably larger, namely more than a centimeter. In addition, bruises of this severity almost always have a deeper hematoma. In this case, however, conservative treatment methods are usually still sufficient.

Grade IV renal contusion

Kidney bruises become really serious when they exceed the first three degrees of severity. A fourth-degree contusion means that serious injuries have occurred to the functional structures of the kidney, as a result of which urinary tract disorders may occur. Surgical measures to treat the bruise can hardly be avoided in such a scenario.

Grade V renal contusion

A kidney contusion of the fifth degree occurs after a very strong external force and, in addition to kidney damage, injuries to the urinary tract also occur. The lower urinary tract can even be completely torn from the kidney, resulting in a life-threatening condition. Only emergency surgery can prevent fatal kidney failure here. Fortunately, such kidney injuries are rare.

Causes of a kidney bruise

In most cases, kidney bruises are caused by a blunt injury, which is usually caused by a fall, collision, punch or the like. The skin remains intact, but a bruise or bleeding occurs under the skin. Typical scenarios in which such violence affects the kidneys are:

  • traffic accidents, such as a pop-tail collision
  • sports accidents, for example in contact or combat sports
  • everyday accidents, such as falls from a great height
  • accidents at work, where something hits you with force
  • physical conflicts, for example a kick or blow to the kidney

In connection with car accidents, kidney contusions are even relatively common, because the person affected can collapse very strongly back into the car seat during the accident. In addition, so-called blunt abdominal trauma (an accident in which external force has occurred without penetrating the abdominal wall) can have an adverse effect on the kidney area due to the force exerted. Physical attacks, especially blows or kicks to the side, are the second most common cause of kidney injuries after car accidents.

Examination and diagnosis

Interview and physical examination

The diagnosis of a kidney contusion is relatively easy to make with the right resources. The main focus is on preventing serious damage to the kidney, which in the most serious cases requires surgical intervention. The doctor first starts by taking the patient’s medical history. You are asked about acute complaints, pain and previous events. This is followed by a physical examination. The doctor looks for visible signs of a kidney bruise such as redness, swelling and bruising and palpates the affected area. Pressure pain is almost always present with a kidney bruise.

Follow-up research

In addition, a urine sample will be taken to test for the presence of blood . Imaging research in the form of ultrasound is also an option. This cannot accurately assess the severity of the trauma, but it can distinguish between a kidney contusion and a more serious kidney injury. With a kidney contusion, only the hematoma under the capsule can be seen in the photo. So there is a clear kidney enlargement. Sometimes additional research is necessary. Computed tomography may be useful for accurate assessment of the kidneys. This is a diagnostic research method in which cross-sections of a body part can be made. A CT scan makes it possible to make statements about the size, the areas involved and the adjacent damage caused by the injury. Magnetic resonance imaging (MRI) can be performed occasionally. If the kidney is mildly bruised, CT or MRI is not used.

Treatment of a kidney bruise

Mild kidney contusion

After the injury, you should rest and, if necessary, cool the affected area with light pressure from outside. Any physical activity should be avoided and a doctor should be consulted. In mild cases of kidney contusion, the kidney recovers spontaneously within one to two weeks and rest promotes the recovery process. You must also drink enough to maintain blood pressure and ensure good blood flow to the kidney. You can take paracetamol as a painkiller if necessary.

Severe kidney contusion

Surgical intervention is only indicated in cases of severe renal trauma, especially if bleeding cannot be considered controlled.


A kidney bruise is usually without complications. However, in rare cases, kidney bruises can cause complications. Older or debilitated people in particular can be affected by complications. A possible complication is inflammation of the renal pelvis or lower urinary tract. The tissue irritated by the impact is temporarily weakened and therefore more susceptible to inflammation.
In some cases, the leaking blood can also promote inflammation, especially in debilitated patients. If fever occurs in addition to the existing symptoms of a bruised kidney, further investigation is needed. Usually a short dose of antibiotics solves the problem. Secondary bleeding can also occur, so you should carefully check your urine for the presence of blood.


A kidney contusion is a painful injury. However, the chance of long-term damage is low. A bruised kidney usually heals on its own within a few days to weeks. The prognosis is generally favorable. It is only dangerous if a serious injury is trivialized and therefore left untreated.

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