Flank Pain

Flank Pain is a highly discomforting condition that affects a staggering percentage of the population worldwide. Read on to know what is Flank Pain, as well as its causes, symptoms, diagnosis, treatment and more.

Flank Pain Definition

Medical researchers define flank pain as a discomforting sensation arising in the flank. Flank refers to the region lying between the hip and the last rib.

Pain in the flanks may be any of these two types:

  • Unilateral – Pain in right or left flank
  • Bilateral – Flank pain on both sides

Flank Pain Location

The pain arises in the flank, the region of the body that is above the Ilium and below the rib. Usually, it begins in a posterior fashion or in the middle part of the axillary line. It results from the stimulation of specific nerve endings upon stretching of the renal capsule or ureter.

Flank Pain Causes

Some of the main causes of Flank pain are:

Kidney problems

Pain in the flanks may arise due to diseases and other problems affecting the kidney, such as kidney stones, renal infection (Pyelonephritis), polycystic kidney disorders, abscesses and renal infarction. In some cases, flank pain may be a symptom of cancerous conditions in the kidney. In case of kidney cancer, there can be blood in the urine along with flank pain.

Abdominal Aortic Aneurysm (AAA)

Approximately 10% patients of Abdominal Aortic Aneurysms (AAA) are seen to develop painful symptoms. The aneurysm is supposed to be a result of stretching or trauma of the nerve plexus surrounding the celiac axis as well as other aortic arterial branches that stimulate the nerves. The aneurysm can lie immediately beside the ureter and give rise to Hematuria from local ureteral trauma or irritation.

Back ailments

A pain in flanks may also arise in case of a traumatic strain in the back muscle due to intense physical activity. A herniated or slipped disc can put pressure over the adjoining regions and result in origin of pain on one side of the human body.

Patients of acute back conditions, such as Spinal Arthritis, frequently experience pain between the back and the abdomen.


This condition is generally characterized by a pain that is milder in intensity than a typical renal colic ache. The condition is characterized by highly discomforting symptoms, such as

  • Fever
  • Chills
  • Nausea
  • Vomiting
  • Stiff neck
  • Headache

The condition also gives rise to tenderness in the flanks that is often more acute in intensity than in renal colic patients.

Gastrointestinal disorders

Aches in the flank area may also arise due to problems in the gastrointestinal system, such as

  • Pancreatitis
  • Stomach ulcers
  • Irritable bowel syndrome
  • Food poisoning

The problem may also originate due to stomach infections such as Diverticulitis that result from entrapment of bacteria in the colon. Other digestive problems may also lead to pain in flanks. In such cases, pain is usually accompanied by other symptoms like abdominal discomfort, nausea and vomiting.

Gynecological problems

In women, pain in the flanks may arise due to presence of an Ovarian Cyst.

Renal abscesses

This condition usually gives rise to pain that is more intense than Pyelonephritis patients can experience. This is due to the fact that inflammation and edema stretches the renal capsule to an even greater extent. In some cases, it gives rise to palpable lumps on flanks. This may be accompanied by other symptoms like irritation of the diaphragm.

Blood clots

Sometimes, blood clots can obstruct the uterus and become responsible for an acute renal colic attack. These blood clots may arise due to underlying medical problems like

  • Renal pelvis tumors
  • Parenchymal tumors
  • Hemophilia
  • Glomerulonephritis
  • Sickle cell disease
  • Angiomyolipoma

These can also originate as a consequence of percutaneous renal biopsies. Use of streptokinase medications has been found to produce successful results in some cases.

Herpes Zoster Infection

The Herpes zoster is a type of virus that gives rise to a viral infection. A Herpes infection can give rise to a mild burning pain, generally in the region surrounding the flank. Generally, the pain arises prior to the occurrence of skin changes characteristic of this infection.  With time, vesicles arise over the affected region, making it possible for doctors to easily diagnose the condition.

Treatment of this viral infection depends on the symptoms, with antiviral agents and analgesics being the medications of choice.


This condition arises due to trauma (injury) of the roots of the lumbar thoracic nerve. It can result in pain in the flanks. A pain characteristic of this condition may also develop due to a trauma to the costovertebral junctions. The pain is similar to Renal Colic when there is pain in the 10th, 11th or 12th ribs. The pain arising due to this disorder is is often found to be an acute one. An injury or scarring of the intercostal nerve can be the main source of the pain.

Flank Pain Symptoms

The condition, as the name indicates, is characterized by a pain in the flank region. The ache usually worsens with movement. The intensity of pain varies from moderate to acute and generally depends on the underlying causative condition. The side where the pain is felt indicates which kidney has been affected. A right flank pain indicates a problem in the right kidney whereas left flank pain suggests a pain in the left kidney. A minor cause may give rise to a moderate pain that can advance with increased body movements, usually unaccompanied by other signs. In acute cases, the pain may be acute and piercing without showing any sign of enhancement or reduction with movements. The pain may spread in a downward direction and result in testicular pain (in men) and labial pain (in women). Acute flank pain may be accompanied by other discomforting symptoms, such as

  • Abdominal pain
  • Fever
  • Muscular tenderness
  • Nausea
  • Pain and discomforts while passing urine
  • Vomiting
  • Pink or Red Urine (due to small amounts of blood in the urine)

Flank Pain Diagnosis

The diagnosis of this problem is usually done by physical examination that involves medical tests like:

  • Abdominal CT scan
  • Cytoscopy
  • Retrograde ureteropyelography
  • Ultrasound examination of the abdomen or the kidney
  • Intravenous pyelography (IVP)
  • Lumbosacral spine x-ray
  • Urine Culture
  • Urinalysis
  • Voiding Cystourethrography

The medical history of the patient is taken into account white determining the cause of the painful symptoms. Physical examination helps in diagnosing the exact cause of the pain. Laboratory tests such as X-rays and blood test are also conducted.

Flank Pain Differential Diagnosis

The differential diagnosis of this disease involves distinguishing it from other disorders, such as:

  • Diarrhea
  • Chronic Digestive Conditions
  • Appendicitis
  • Food poisoning

Flank Pain Treatment

Treatment for flank pain, which usually depends on the underlying cause, includes:

  • Hydration
  • Analgesics (pain medications)
  • Antibiotic medicines

Doctors recommend patients to get enough rest for treatment of mild flank pain. This should be followed by exercise and physical therapy for complete cure. Patients of Spinal Arthritis are prescribed anti-inflammatory medicines. Antibiotic medications are used for treatment of infections in the urinary tract and kidneys. Analgesics (pain relieving medicines) and high intake of fluids can help in case stones are diagnosed in kidneys.

In case of acute flank pain, immediate hospitalization may be required.

Flank Pain Prevention

Pain in the flanks can be prevented by following a healthy lifestyle which involves:

  • Daily intake of healthy foods
  • Drinking enough fluid to keep the body hydrated
  • Exercising regularly

Right Flank Pain

Pain in the flank in the right side of the body may arise due to infections in the urinary tract and the bladder, kidney problems as well as gynecological disorders. Individuals suffering from arthritis or diabetes may also suffer from this pain. It may also originate due to muscle pull or injury in the lower back area. In women, Ovarian Cyst development may be one of the major causes of right flank pain.

Left Flank Pain

The flank in the left side of the human body can pain due common problems like muscular spasms or severe cases of infections like acute Pyelonephritis. Gastrointestinal Disorders, Kidney Problems, Urinary Tract ailments and Diverticulitis may also give rise to this pain. If stones develop in the left kidney, there can be a left-sided flank ache in sufferers.

Lower Left Flank Pain

Pain in the lower left region of the flank is usually dull and stabbing in nature. It can arise due to problems in the viscera or the internal organs of an individual. Pain may also originate due to structures external to the abdomen. Lower left pain maybe harmless or acute. Lower abdominal pain that arises rapidly may be a sign of a serious underlying condition and can be treated by an experienced medical professional.

Left Flank Pain after Eating

Many individuals experience a stabbing pain in the left side of the abdomen just after having food. The pain can be acute enough to make it difficult to perform daily activities. Patients usually feel an overwhelming urge to lie down while moving about.

The pain may arise due to problems in organs like gallbladder, pancreas, appendix and liver. CT Scan, Ultrasound examinations, Endoscopy, Colonoscopy and blood or urine tests can help diagnose these problems.

Intermittent Flank Pain

Many patients of Irritable Bowel syndrome (IBS) are found to suffer from intermittent pain in the flanks. The problem can also arise in sufferers of Medullary Sponge Kidney (MSK). Pain may arise during waking hours as also in times when a patient is asleep. Dull pain may cause discomforts while sharp flank ache may actually disrupt sleep and compel sufferers to sit up. Flank muscle pain due to trauma encountered during sports activities may also be a cause of this problem.

Chronic Flank Pain

Chronic cases of this condition may arise due to persisting kidney problems like:

  • Kidney stones
  • Kidney abscesses
  • Kidney tumors
  • Kidney cysts
  • Kidney Infection (Acute Pyelonephritis)
  • Glomerulonephritis

The causes of flank pain may be different in men and women. In men, pain in the left flank may arise due to problems like :

  • Spermatic cord disorders
  • Testicular disorders
  • Sexually transmitted diseases (such as Gonorrhea)

Left flank pain in women may be a result of problems like:

  • Mid-cycle pain (Mittleschmerz)
  • Polycystic ovarian syndrome
  • Miscarriages
  • Ovarian Cysts
  • Pelvic Inflammatory Disease
  • Endometritis
  • Ectopic pregnancy

In both men and women, painful symptoms may arise due to other reasons like :

  • Constipation
  • Splenic flexure syndrome
  • Colon Cancer
  • Inflammatory bowel disease (such as Ulcerative Colitis and Crohn’s disease)
  • Diverticulitis
  • Ischemic/Microscopic colitis
  • Diverticulosis
  • Appendicitis
  • Infected or enlarged spleen

Severe colicky flank pain that radiates to the groin, scrotum and the labia may be a result of Acute Renal Colic. Renal Colic pain commonly arises when a small stone passes down the ureter, the tubular structure connecting the kidney to the bladder.

Flank Pain During Pregnancy

Many pregnant women are also found to suffer from pain in their flanks during pregnancy. Approximately 200,000 pregnant women in the U.S have been estimated to have this problem every year. This can occur due to the presence of conditions like

  • Ureteral Obstruction
  • Ovarian Tumor
  • Renal Calculus
  • Ovarian Torsion
  • Placental Abruption
  • Strain or rupture of the abdominal muscle

Flank Pain ICD 9 Code

The ICD 9 code for flank pain is roughly 789.07, which falls under “other symptoms involving abdomen and pelvis”. However, this does not specify the exact point of origin of the pain.

If you are suffering from a persisting pain in the flanks, immediately get in touch with an experienced health-care provider. A good doctor will ascertain the underlying cause and treat the condition accordingly. An early diagnosis and treatment can help you make an early recovery from the disorder. So if you are having flank pain, do not delay treatment.








  1. Janet June 23, 2015
  2. foakleys.org November 28, 2016
  3. bv lu April 10, 2018

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