Causes of Kidney Pain

Everything you need to know about renal pain

Kidney pain, also known as renal pain, can be caused by injury, disease, 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. Since the kidneys are close to the spine/back and gallbladder, it's important to differentiate kidney pain from other causes of pain.

The pain may be described as dull and throbbing or sharp and severe, depending on the underlying cause. It is usually deeper than back pain and located on the upper back, just below the ribs.

Kidney pain is classified as unilateral if one kidney is affected or bilateral if both kidneys are affected. The cause can be intrinsic (occurring within the kidneys), prerenal (related to an organ above the kidneys), or postrenal (related to obstruction or disorder below the kidneys).

kidney pain causes
Illustration by Alexandra Gordon, Verywell


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 strikes suddenly and severely, often over the span of two days. Chronic pyelonephritis is recurrent and usually milder.

Pyelonephritis is usually caused by an infection that has spread from the lower urinary tract, including the ureters, bladder, or urethra.

Symptoms include:

  • Unilateral or bilateral kidney pain, often blunt and intense, felt in the flank (back and side), abdomen, or groin
  • High fever (higher than 102 degrees F)
  • Body chills
  • Nausea and vomiting
  • Fatigue
  • Confusion
  • Dysuria (painful or burning urination)
  • Cloudy or fishy-smelling urine
  • Hematuria (blood in urine)
  • Urinary urgency (a frequent need to urinate)

Symptoms of chronic pyelonephritis are not usually intense, 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. The kidneys are located in a vulnerable position in the abdomen.

As many as 10% of abdominal injuries will sustain damage to the kidneys. Vehicle accidents, physical assaults, and severe falls account for the majority of renal traumas.

These injuries are not always overtly symptomatic, and some may cause dull pain. 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.

Symptoms that warrant emergency treatment include fever, blood in the urine, an inability to urinate, decreased alertness, tachycardia (rapid heart rate), and abdominal pain and swelling.

Renal Obstruction

Renal obstruction can occur in the kidneys or as the result of urinary blockage downstream. Those that 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:

  • Kidney stones
  • Bladder stones
  • Urinary tract infection (UTI)
  • Retention of urine from an enlarged prostate
  • Strictures (scarring) of the ureter
  • Pregnancy
  • Long-term catheterization
  • Renal vein thrombosis (a blood clot in the kidney)
  • Neurogenic bladder (nerve-related bladder weakness)
  • Bladder, cervical, colorectal, prostate, or uterine cancer
  • Vesicoureteral reflux, a congenital disorder in which the urine backflows into the kidneys

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 occurring in waves, centered in the flank and radiating to the abdomen and groin. Other causes have less specific symptoms, and 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 extensive.

The most common growths in the kidneys 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 they are large enough to compromise the structure 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 either gross (visible) hematuria or microscopic hematuria.

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

PKD may be symptom-free until the cysts cause structural damage to the kidney. In addition to flank pain, which is 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 between ages 30 and 50. Around 10% will advance to renal failure.

When to See a Healthcare Provider

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

If the pain persists, worsens, or is accompanied by urinary symptoms or signs of infections, you should see your healthcare provider 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.

Get medical attention if you experience a dull, persistent pain alongside symptoms such as painful urination, chronic fatigue, or unexplained weight loss. If you are suddenly unable to urinate, this may be a sign of an obstruction in need of urgent care.

If you are pregnant, don't assume that persistent back pain is pregnancy-related. Tell your doctor if you have 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 healthcare provider immediately.


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 growths or other structural issues.

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 identify signs of kidney dysfunction, including excessive protein, albumin, or red blood cells.

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 produced and excreted in urine at a constant rate

Abnormalities in these values would indicate that the kidneys are not working as they should.

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.

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.

Imaging Tests

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

Among the tests commonly used:

  • 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 the kidneys. The test is used 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 be 200 times that of a 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. An MRI doesn’t expose you to ionizing radiation.

Other Procedures

If imaging tests don't provide a clear image of an obstruction or disorder of the lower urinary tract, the healthcare provider may recommend a procedure known as cystoscopy. This involves the insertion of a flexible or rigid 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 a possible complication.

If there is an abnormality in the ureter or inside the kidney, you may get a ureteroscopy, which is done under anesthesia. This is when a urologist inserts a small flexible or rigid tube from your bladder all the way up into the ureter and kidney.

If cancer is suspected, a biopsy may be performed to obtain a sample of cells from a 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, healthcare providers will often need to explore other causes of flank 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)

Kidney pain is not a typical sign of kidney failure. With chronic kidney disease (CKD) or acute renal failure (ARF), you are more likely to feel pain in your joints and muscles (due to the build-up of toxins and depletion of electrolytes) than in your kidneys.


The treatment of kidney pain varies based on the causes. Severe disorders typically require the care of a nephrologist (kidney specialist) or a urologist (urinary tract specialist).

Kidney Infection

Most kidney infections are bacterial and readily treated with broad-spectrum antibiotics. Fungal and viral infections can affect people who have 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, co-trimoxazole, 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: Renal contusion (bruised kidney) or a non-expanding hematoma (blood clot)
  • Grade 2: Laceration of less than 1 centimeter
  • Grade 3: Laceration greater than 1 centimeter
  • Grade 4: Laceration greater than 1 centimeter that causes internal bleeding
  • Grade 5: Detached or shattered kidney or one in which the renal artery is blocked

Low and moderate grade injuries can often be treated with observation, serial imaging, and extended bed rest. Severe injuries 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 from select parts of the kidney.

A surgical procedure known as nephrectomy may be needed to remove one or, less commonly, both kidneys if repair is not possible. 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

Treatments may need to be done in a staged fashion. In acute or emergency settings. tubes may be placed to bypass the blockage. Tubes can be placed from your back directly into your kidney (nephrostomy tube). A tube can also be placed up into the ureter and kidney through your bladder (ureter stent). Both these tubes can help open or remove the blockage to help your kidney drain urine properly.

If the blockage is from an infection, then antibiotics may be given through an IV or orally. If the blockage is from a stone, then you may need a procedure to remove the stone. If the blockage is from a tumor or mass in the lining of your ureter or kidney, a biopsy will be needed.

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 targeted therapy.

There are no treatments for PKD. Treatment is focused on avoiding complications (including high blood pressure, renal infection, kidney failure, and brain aneurysm) and routine disease monitoring.

Tumors of the kidneys can be in the actual meat of the kidney (where the blood is filtered into the urine) or in the inside lining of the kidney (where urine collects).

Frequently Asked Questions

  • Where is flank pain located?

    Flank pain is located on the sides and back of your torso, below your ribs and above your pelvis. The pain is usually worse on one side of the body, but it can affect both sides.

  • What does kidney cyst pain feel like?

    It sometimes won't cause any symptoms. When it does, you may experience flank pain along with fever, blood in the urine, dark urine, or frequent urination. It might also cause high blood pressure if it's keeping your kidney from filtering extra fluid from your blood.

  • Can drinking fluids help prevent kidney problems?

    In some cases, yes. Drinking enough fluids can prevent dehydration, and may make it harder for kidney stones to form by keeping the crystals from sticking together. While a typical recommendation is to drink eight glasses of water a day, that amount may vary depending on your age and health.

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Additional Reading

By James Myhre & Dennis Sifris, MD
Dennis Sifris, MD, is an HIV specialist and Medical Director of LifeSense Disease Management. James Myhre is an American journalist and HIV educator.