The kidneys are essential components of the urinary system. They are bean-shaped organs that lie within the abdominal (retroperitoneal) cavity. The main function of the kidneys is formation of urine by filtration of the blood. The kidneys also play an essential role in maintaining homeostasis in the body.
Due to the location of the liver in the right abdominal cavity, the right kidney lies at a lower level than the left kidney. Both the kidneys are protected by the surrounding fat and other structures of the abdominal cavity. However, due to the close proximity of the kidneys to other organs, it is difficult to distinguish pain arising from kidneys from pain arising from nearby structures.
What do the kidneys do?
The two kidneys receive oxygenated blood through the branches of renal arteries, which themselves branch off from the aorta in the abdominal region. The oxygen-rich blood received by the kidneys is then filtered to remove waste products and some electrolytes. The blood from the kidneys returns to the inferior vena cava through the renal veins. Pathological changes in the renal arteries and veins adversely affect the functioning of the kidneys.
The urine formed by the kidneys is carried to the urinary bladder through two long tubes known as the ureters. The flow of urine from the kidneys to the urinary bladder can be hampered if the ureters get compressed by the abdominal or peritoneal structures that lie nearby.
On top of the kidneys lie the adrenal glands. Also known as the suprarenal glands, the adrenal glands are endocrine organs that synthesize and secrete hormones (adrenalin and cortisol) that play an important role in stress response. Due to the close proximity of adrenal glands and the kidneys, disorders of the adrenal gland can contribute to kidney pain.
Kidney Pain Location
The kidneys lie just below the diaphragm and to the sides of the abdomen (in the retroperitoneal cavity). Therefore, pain arising from the kidneys is usually felt in the abdominal flanks and the back. However, it is important to note that not all pain in the flanks and the back region can be attributed to kidney pain.
Pain felt after trauma (such as a punch to the flanks of the abdominal wall) or after intense physical exertion (such as after running hard) usually has muscular rather than renal origin. In addition, pain caused by other nearby organs in the abdominal cavity can also be mistaken for kidney pain. In women, pain caused by menstruation, fallopian tubes, ovaries, and ovulation could be mistaken for kidney pain.
Signs and Symptoms
Kidney pain is usually felt in the abdominal flank or the mid-back region. It may be accompanied by the following signs and symptoms:
- A burning sensation or pain may occur during urination. Alternately, the pain sensation may also get relieved by urination.
- Blood may also occur in the urine (a condition known as hematuria).
- Urination may become difficult and require straining. Dribbling of urine and an erratic start-stop flow may occur.
- The volume of urine may decrease. If this is accompanied by swelling in the lower limbs, abdomen or the whole body, then medical attention must be sought immediately.
- The color of the urine may undergo changes. Sediments may also be seen in the urine.
The above mentioned signs and symptoms may also arise due to disorders of other organs of the urinary system, such as the ureters, urinary bladder and urethra. Disorders of the prostate gland in men may also cause similar signs and symptoms.
It is important to note that kidney pain may also occur without any other accompanying signs and symptoms. Kidney pain is diagnosed by a doctor by using the Murphy’s punch sign test. During physical examination, a gentle tapping on the back (at the level of the kidney) can elicit pain if there is an infection in or around the kidney.
Read more on signs of kidney problems.
Causes of Kidney Pain
Kidney infections can occur when bacteria reach the kidneys from other parts of the urinary system. For example, an abscess can develop in the kidney when bacteria from the ureter or blood manage to reach the kidneys.
Abscess in the kidneys requires immediate medical attention. Infection of the kidney (pyelonephritis) may be accompanied by kidney pain, chills, fever, loss of appetite, fatigue, hematuria, and dysuria. If the kidney infection is recurring or chronic, then the underlying cause should be identified and treated.
Inflammation of the kidney is technically referred to as nephritis. There are multiple causes for kidney inflammation, including infections, obstruction, trauma, and autoimmune diseases. Kidney inflammation is commonly accompanied by swelling and pain. Hematuria, proteinuria and edema may also be present.
Kidney pain may also be caused by tumors of the kidney and ureter. A common cause is a cancer known as urothelial cancer, which affects the kidneys, ureter, and the bladder. Along with kidney pain, these cancers may also cause hematuria, reduced urine output, loss of appetite, and weight loss.
Kidney pain may occur when there is either an obstruction to the flow of blood through the kidneys or an obstruction to the flow of urine to the bladder. Depending on the site of obstruction, the pain can either be unilateral or bilateral. Hematuria, decreased urine output and other signs and symptoms may also be present.
An obstruction to the flow of blood through the kidneys (usually caused by renal embolism, stenosis of renal artery, atherosclerosis, renal vein thrombosis and entrapment) results in renovascular hypertension. This can ultimately result in permanent kidney damage. Obstruction to the outflow of urine (usually caused by kidney stones) can cause swelling of the kidney (hydronephrosis).
Read more on kidney stones.
Changes in nutrition and fluid intake can also adversely affect the kidneys. Examples of nutritional changes that may impact the kidneys include eating disorders, chronic fasting, dehydration, bodybuilding supplements and diets, and weight loss diets. Renal insufficiency and kidney failure can also occur in some of these cases.
Poisoning (such as fluoride poisoning, arsenic poisoning, and antifreeze poisoning) can adversely affect kidney function as the toxins may accumulate within the kidneys. This may cause kidney pain, hematuria, dysuria, changes in urine output and changes in the color of the urine.
Even though the kidneys are protected by many surrounding tissues, a blow to the overlying region (as in assault or accident) can injure the kidneys. This can result in inflammation and renal hemorrhage.
Renal insufficiency occurs when the kidneys are not able to effectively carry out their primary function of filtration. Chronic renal insufficiency can ultimately lead to kidney failure. Kidney pain, edema and itchy skin may indicate renal failure. When chronic, all the previously mentioned causes of kidney pain can cause renal insufficiency and renal failure.
Other potential causes of renal insufficiency and renal failure include alcohol abuse, hypertension, diabetic nephropathy, amyloidosis, liver diseases, polycystic kidney disease, poisoning, and sickle cell disease.