Causes of Kidney Pain

Everything you need to know about renal pain

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Kidney pain, also known as renal pain, is caused by the injury, impairment, or infection of the kidneys. The kidneys are a pair of bean-shaped organs situated on either side of the spine that are responsible for filtering blood and maintaining the correct balance of fluids and electrolytes in the body. The pain may be described as dull and throbbing or sharp and severe depending on the underlying cause. While kidney pain is sometimes mistaken for back pain, the sensation is far deeper and located higher on the upper back, just below the ribs.

Kidney pain can be classified as unilateral if one kidney is affected or bilateral if both kidneys are affected. This may provide a clue as to whether the problem is intrinsic (occurring within the kidneys), prerenal (related to an organ above the kidneys), or postrenal (related to obstruction or disorder below the kidneys).

Causes

The causes of kidney pain are extensive and can be broadly characterized as either an infection, trauma, obstruction, or growth.

Kidney Infection

A renal infection, also known as pyelonephritis, is typically caused by bacteria and can affect one or both kidneys. Acute pyelonephritis is a type that strikes suddenly and severely, while milder, recurrent cases are referred to as chronic pyelonephritis. Pyelonephritis is usually caused by an infection that has spread from the lower urinary tract, including the ureters, bladder, or urethra.

Acute pyelonephritis can often develop over the span of two days. Symptoms include:

  • Unilateral or bilateral kidney pain, often blunt and intense, felt in the flank (back and side), abdomen, or groin
  • High fever (greater than 102 Fahrenheit)
  • Body chills
  • Nausea and vomiting
  • Fatigue
  • Confusion
  • Painful or burning urination (dysuria)
  • Cloudy or fishy-smelling urine
  • Blood in urine (hematuria)
  • A frequent need to urinate (urinary urgency)

Chronic pyelonephritis is experienced less intensely, and, in some cases, there may be no symptoms. If symptoms do develop, they may include a dull ache in the flank accompanied by malaise and a low-grade fever.

Kidney Trauma

Renal trauma is caused by either a blunt-force impact or a penetrating wound that lacerates one or both kidneys. Because of the kidneys' vulnerable position in the abdomen, injuries like these are not uncommon. In fact, as many as 10 percent of abdominal injuries will sustain damage to the kidneys. Vehicle accidents, physical assaults, and severe falls account for the majority of renal traumas.

The challenge with these injuries is that they are not always overtly symptomatic. While some may present with pain, the pain may be dull rather than specific, and there may or may not be any signs of bruising or physical injury. With that being said, touching the kidney area will usually cause pain.

Other characteristic symptoms may include fever, hematuria, an inability to urinate (urinary retention), decreased alertness, rapid heart rate (tachycardia), and abdominal pain and swelling. Symptoms like these warrant emergency treatment.

Renal Obstruction

Renal obstruction can occur in the kidneys or as the result of urinary blockage downstream. Those that are intrinsic or affect the ureters may cause unilateral or bilateral pain. A blockage downstream in the bladder or urethra tends to impact both kidneys.

Also known as obstructive uropathy, the blockage may be caused by any number of conditions, including:

When an obstruction occurs for whatever reason, the kidneys will begin to swell, a condition referred to as hydronephrosis. Symptoms include pain in the flank, groin, or abdomen alongside fever, dysuria, urinary urgency, and nausea.

The symptoms can vary by the location and severity of the obstruction. Kidney stones often cause the most pain, typically centered in the flank and radiating to the abdomen and groin in waves. Others are less specific but can worsen if the blockage is left untreated, leading to fever, sweating, chills, vomiting, hematuria, and diminished urine output.

Renal Tumors or Cysts

Renal tumors or cysts do not typically cause pain unless the growth is advanced or the disbursement is extensive. The three most common growth abnormalities include:

  • Renal adenoma: A type of benign tumor that can grow to a substantial size
  • Renal cell carcinoma (RCC): A type of cancer that usually begins in the tubules of the kidneys
  • Polycystic kidney disease (PKD): An inherited disorder in which benign, fluid-filled cysts proliferate throughout the kidneys

By and large, renal tumors, whether benign or cancerous, do not cause pain until their size compromises the architecture of the kidney. It is at this stage that the pain will usually be persistent, aching, and likely to worsen over time. The pain would most often be unilateral and accompanied by hematuria, either visible (gross hematuria) or invisible (microscopic hematuria).

If cancer is involved, persistent malaise and unexplained weight loss are tell-tale signs suggestive of an advanced malignancy.

PKD may also be symptom-free until such time as the formation of cysts causes structural damage to the kidney. In addition to flank pain, usually bilateral, PKD may cause progressively worsening symptoms, including headaches, high blood pressure, hematuria, abdominal pain and swelling, recurrent kidney stones, recurrent UTIs, and renal failure.

As opposed to many of the other renal conditions, PKD is associated with excessive urination (polyuria) rather than impaired urination. The most common form of PKD, known as autosomal dominant PKD, manifests with symptoms when patients are in their 30s and 40s. Around 10 percent will advance to renal failure.

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When to See a Doctor

People will often assume that sudden flank pain is caused by a pulled muscle or overexertion, and, in many cases, it will be.

If the pain persists, worsens, or is accompanied by urinary symptoms or signs of infections, you should see your doctor as soon as possible. This is especially true if you are experiencing high fever, chills, vomiting, or the inability to urinate.

Even if a kidney infection is mild, it can sometimes progress and lead to bacteremia if left untreated. This is a condition in which a local bacterial infection “spills over” over into the bloodstream, causing systemic and potentially life-threatening symptoms, including irregular body temperatures, disruptions in breathing, a severe drop in blood pressure, and shock. Given that acute pyelonephritis can strike in as little as two days, a rapid response is essential.

The same applies if you experience a dull but persistent pain alongside uncommon symptoms such as painful urination, chronic fatigue, or unexplained weight loss. None of these should be considered normal, and you shouldn’t wait until there is visible blood in urine to seek care.

If you are pregnant, don't assume that a persistent back pain is pregnancy-related. Be cognizant if there is a dull ache across your lower back or along the sides of your back between the ribs and hips. If accompanied by symptoms of infection or changes in urination, call your doctor immediately. This is especially true if you are suddenly unable to urinate. This may be a sign of an obstruction in need of urgent care.

When Should You See a Kidney Doctor?

Diagnosis

Only a medical evaluation can confirm a kidney condition or pinpoint the cause of a kidney pain. There are no reliable self-exams or tests to do at home. The diagnostic tools include lab and urine tests to evaluate your body chemistry and imaging tests to identify and characterize the nature of the disease.

Labs and Tests

A urinalysis is central to the diagnosis of any renal disorder. A complete urinalysis is performed by a lab to assess the chemical composition of your urine and to find any evidence of kidney dysfunction, including excessive protein, albumin, or red blood cells. Abnormal findings will suggest a kidney problem. Normal findings, by contrast, can usually rule out the kidneys as the cause.

Blood tests will also be used to evaluate your kidney function. These include:

  • Serum creatinine (SCr), which measures the level of a substance called creatinine that the body produces and excretes in urine at a regular rate
  • Glomerular filtration rate (GFR), which uses the SCr to calculate how much blood is being filtered by the kidneys
  • Blood urea nitrogen (BUN), which measures the level of a compound called urea that is also produced and excreted in urine at a constant rate

Any abnormalities in the excretion would indicate that the kidneys are not working as they should.

If an infection is suspected, a blood test known as erythrocyte sedimentation rate (ESR) may be used to check for inflammation, while a urine culture can help isolate and identify specific bacterial or fungal infections.

Finally, a complete blood count (CBC) and liver function test (LFT) can offer further insights as to whether the dysfunction is caused by an associated disease (such as high blood pressure, diabetes, or cirrhosis) or if changes in the blood chemistry are consistent with cancer. (There are no blood or urine tests that detect renal cancer).

Understanding Kidney Function Test Results

Imaging Tests

Imaging tests are used as a means to indirectly visualize the kidneys and adjacent structures. They can identify irregularities in the shape or structure of the kidneys, identify cysts and solid tumors, or pinpoint the location of a bleed or obstruction.

Among the three tools commonly used for this:

  • Ultrasounds use sound waves to create high-contrast images of internal organs. It is often the first test used as it is fast, portable, and does not expose you to ionizing radiation. Ultrasounds are particularly useful in differentiating cysts from solid tumors.
  • Computed tomography (CT) uses a series of X-rays to create a cross-sectional image of your kidneys. The test is ideal for identifying lesions, abscesses, stones, tumors, and other abnormalities that an ultrasound or X-ray might miss. While radiation is kept to a minimum, it may still be 200 times that of standard chest X-ray.
  • Magnetic resonance imaging (MRI) uses a magnetic field and radio waves to visualize the kidneys, providing finer details than a CT or ultrasound. While an MRI doesn’t expose you to ionizing radiation, a radioactive contrast agent may be needed to visualize certain tissues.

Other Procedures

If imaging tests are unable to provide a clear image of an obstruction or disorder of the lower urinary tract, the doctor may recommend a procedure known as cystoscopy. This involves the insertion of flexible fiberoptic scope into the urethra to view the bladder and is commonly used to help diagnose bladder stones, cystitis, strictures, and cancer.

Cystoscopy is performed under local anesthesia and may cause pain and mild bleeding. Infection is also possible.

If cancer is suspected, a biopsy may be performed to obtain a sample of cells from suspicious growth. It can be performed with a fine needle aspiration (FNA), in which a narrow needle is inserted into a tumor with the aid of an ultrasound, or a core needle biopsy (CNB), which utilizes a thicker, hollow-core needle. Both are nearly equal in their ability to correctly diagnose renal cancer.

Differential Diagnoses

People will often be surprised at how high up the kidneys are in the back. In many cases, a persistent pain will be incorrectly attributed to the kidneys when it is, in fact, muscle or skeletal problem. To this end, doctors will often need to explore other causes of "kidney pain" if urinalysis and other tests do not suggest a renal disorder.

Examples include:

  • A fracture of the 11th or 12th rib, which can mimic a renal injury
  • An upper thoracic or lumbar spine injury, in which spinal nerve pain can radiate to the flank (known as referred pain)
  • Neuropathic flank pain caused by shingles (herpes zoster)
  • Pleuritis, inflammation of the pleura (lining of the lungs)
  • A retroperitoneal abscess, a serious pus-filled infection situated between the anterior abdominal wall and the peritoneum (lining of the abdominal cavity)

While some people assume that kidney pain is a sign of kidney failure, it rarely is. Whether you have chronic kidney disease (CKD) or acute renal failure (ARF), you are more likely to feel pain in the joints and muscles (due to the build-up of toxins and depletion of electrolytes) than in the kidneys.

Treatment

The treatment of kidney pain is as varied as the causes themselves. Severe disorders typically require the care of a kidney specialist known as a nephrologist or a urinary tract specialist known as a urologist.

Kidney Infection

Most kidney infections are bacterial and readily treated with broad-spectrum antibiotics. Fungal and viral infections are most commonly seen in people with compromised immune systems, including organ transplant recipients and people with advanced HIV.

A urine culture can help isolate the bacterial strain so that the most appropriate antibiotic is chosen. The most commonly prescribed antibiotics include ampicillin, cotrimoxazole, ciprofloxacin, and levofloxacin. Severe cases may require intravenous rather than oral antibiotics. Resistant bacterial strains may require combination antibiotic therapy or more potent antibiotics like carbapenem.

During treatment, you'll need to drink plenty of water to promote urination and help flush the upper and lower urinary tract.

Kidney Trauma

Treatment of a renal trauma is directed by the grading of the injury as follows:

  • Grade 1 for a renal contusion (bruised kidney) or a non-expanding hematoma (blood clot)
  • Grade 2 for a laceration of less than 1 centimeter
  • Grade 3 for a laceration greater than 1 centimeter
  • Grade 4 for a laceration greater than 1 centimeter that causes internal bleeding
  • Grade 5 for a detached or shattered kidney or one in which the renal artery is blocked

Low-grade injuries can often be treated with extended bed rest. More severe events may require surgical repair, including the placement of renal stents to open obstructed vessels. Selective embolism, in which a chemical agent or metallic coil is used to block a blood vessel, may help control bleeding.

In the worst-case scenario, a surgical procedure known as nephrectomy may be needed to remove one or, less commonly, both kidneys. While you can function normally with just one kidney, the removal of both would require you to be placed on dialysis until an organ donor can be found.

Renal Obstruction

Treatment is primarily focused on relieving the source of the obstruction. This may involve antibiotics to resolve an infection, nephrostomy (the drainage of urine with a urethral catheter), or surgery if a stone cannot be passed on its own.

Severe hydronephrosis may require percutaneous nephrostomy, a procedure in which a tube is inserted through your back to directly drain the kidneys. A ureter stent may also be placed during cystoscopy to open a blocked ureter.

Additional treatments may be needed to address the underlying cause.

Renal Tumors or Cysts

Depending on the findings, treatment may involve selective embolism to reduce the size of a tumor (essential "starving" the tumor of the blood needed for growth) or nephrectomy to remove part or all of the affected kidney. Benign tumors are often treated in the same way as cancerous ones if they obstruct vessels or tubules inside of the kidney.

Cancer therapy is directed by the stage of the malignancy which is based on the size of the tumor, the number of nearby lymph nodes affected, and whether the tumor has metastasized (spread). Treatment options include chemotherapy, radiation therapy, immunotherapy, and newer-generation targeted therapy.

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There are no treatments for PKD. Treatment would instead be focused on the avoidance of complications (including high blood pressure, renal infection, kidney failure, and brain aneurysm) in tandem with routine disease monitoring.

A Word From Verywell

The development of kidney pain isn't something you should ignore. While over-the-counter painkillers like Advil (ibuprofen) or Tylenol (acetaminophen) may provide short-term relief, they are unable to treat the underlying cause, which in some cases may be serious and otherwise asymptomatic.

The same applies to hydration. While drinking plenty of water or cranberry juice may help ease a mild urinary tract infection, it is not considered curative. If in doubt as to whether you need a doctor, simply call your doctor's office or check if your health insurance company offers free telemedicine consultations.

On the other hand, if you experience sudden, severe kidney pain—whether or not there is blood, fever, nausea, or any other symptom—you need to seek emergency care without exception.

When Should You See a Kidney Doctor?
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