Left Flank Pain in Korea: Kidney Stones, Kidney Infection or Pancreatitis, and Which Hospital Department to Visit
Left flank pain has many possible causes. Official sources list kidney stones, kidney infection, spine and disc problems, muscle spasms, shingles, and gallbladder, liver or digestive disease. The US National Library of Medicine (MedlinePlus) says flank pain that comes with fever, chills, blood in the urine, or frequent or urgent urination is more likely a kidney problem. It advises contacting a doctor if the pain comes with high fever, chills, nausea or vomiting, if urine looks red or brown, if unexplained pain continues, or if eating or drinking becomes hard. This guide is for travelers and residents in Korea. It draws on Korea's national disease agency (KDCA) and two major Seoul hospitals, Asan Medical Center and Seoul National University Hospital. It explains how each source separates the main causes and which department each hospital lists, so you can walk into a Korean hospital better prepared. All sources were checked on November 11, 2026.
What counts as flank pain
Sources describe the area slightly differently. Asan Medical Center's symptom encyclopedia describes flank pain as pain felt in the rib area between the chest and the back. MedlinePlus defines it as pain on one side of the body, between the upper abdomen and the back.
MedlinePlus lists these possible causes: arthritis or infection of the spine, back problems such as disc disease, gallbladder disease, gastrointestinal disease, kidney stones, kidney infection or abscess, liver disease, muscle spasm, shingles (pain with a rash on one side) and spinal fracture. Because the list is so wide, the symptoms that come with the pain tell doctors more than the location alone.
None of the sources says the side of the pain identifies the cause by itself. The sections below describe the symptom combinations each institution links to three conditions. They are background for talking with a doctor, not a way to diagnose yourself.
Kidney stones: severe pain that painkillers may not settle
Asan Medical Center describes urinary stones as stones that form along the urinary tract. Depending on where they form, they are called kidney, ureter, bladder or urethral stones. The hospital says the flank pain can be severe enough that painkillers do not easily relieve it. It can affect one or both sides of the lower back and can spread toward the lower abdomen or testicles. It can also be confused with appendicitis.
According to the hospital, blood in the urine, indigestion, nausea and vomiting can occur. Fever is usually absent, but a high fever can develop if a bacterial infection is also present. For stones under 5mm, the hospital describes a watch-and-wait approach: drinking plenty of water, taking painkillers and having regular X-rays to see whether the stone passes on its own.
If the ureter is blocked and an infection causes severe fever, nausea or vomiting, or if the patient has only one kidney, Asan Medical Center says doctors do an emergency procedure to open a drainage path for urine. The options are a percutaneous nephrostomy or a ureteral stent. Asan Medical Center lists urology as the department for urinary stones.
Kidney infection (acute pyelonephritis) versus a bladder infection
Korea Disease Control and Prevention Agency (KDCA) runs the government's national health information portal. It lists these symptoms of upper urinary tract infections such as pyelonephritis: fever and chills, flank and lower back pain, headache, and nausea, vomiting or abdominal pain. It notes that urinary symptoms may be absent.
KDCA separates the two types by whole-body symptoms. Upper infections of the kidneys and ureters come with systemic symptoms such as fever and flank pain. Lower infections of the bladder and urethra (cystitis) mainly cause painful urination, frequent urination and a feeling that the bladder has not emptied, without whole-body symptoms. KDCA also notes that children, older adults, people with neurogenic bladder and catheter users may not show the typical symptoms.
Seoul National University Hospital says E. coli causes 85% of acute pyelonephritis cases. Flank pain and fever are the main symptoms, sometimes with nausea and vomiting. Simple cases can be treated as an outpatient with 1 to 2 weeks of oral antibiotics. Patients who cannot take pills or have severe symptoms are admitted for IV antibiotics. The hospital warns that pyelonephritis that is not treated properly can lead to sepsis. Asan Medical Center gives the usual treatment length as 7 to 14 days.
KDCA says imaging to check for complications may be needed if fever continues after more than 72 hours of appropriate antibiotics. It defines recurrent infection as two or more episodes within 6 months, or three or more within a year.
Korea's national health information portal explains how upper and lower urinary tract infections differ. · Photo: 질병관리청 국가건강정보포털 공식
Acute pancreatitis: the left-side pattern
Seoul National University Hospital describes a pattern that specifically involves the left side. Acute pancreatitis pain often starts in the upper abdomen or around the navel and spreads to the back or the left flank. The pain gets worse when lying flat, so patients often bend forward and pull their knees up. It usually worsens after eating.
The hospital names gallstones and alcohol as the most common causes, together accounting for 60 to 80% of cases. It says acute pancreatitis can be diagnosed when serum amylase is at least three times the normal level and the typical abdominal pain is present, if no other cause is found. It lists gastroenterology, surgery and pediatrics as the departments for this condition.
Choosing a department at a Korean hospital
Large Korean hospitals sort patients by specialty department, and the same condition can be listed under different departments. Seoul National University Hospital lists nephrology, urology and pediatrics for pyelonephritis. Asan Medical Center lists infectious diseases, nephrology and pediatric nephrology for the same condition. For urinary stones, Asan Medical Center lists urology. For acute pancreatitis, Seoul National University Hospital lists gastroenterology, surgery and pediatrics.
As a quick reference: severe pain that painkillers do not settle, spreading toward the groin, with blood in the urine, matches the urinary stone description (urology). Fever and chills with flank pain matches the upper urinary tract infection description (nephrology, infectious diseases or urology, depending on the hospital). Upper abdominal pain spreading to the back or left flank that worsens after meals or when lying flat matches the pancreatitis description (gastroenterology or surgery).
Tell staff where the pain is, when it started and what it feels like. MedlinePlus says doctors ask about exactly these three things first. Writing them down beforehand can help if you are worried about a language barrier.
Tests to expect and a prevention tip
MedlinePlus says that depending on the case, doctors may order a urinalysis and urine culture and blood tests for kidney and liver function. Imaging may include an abdominal or kidney ultrasound, an abdominal CT scan, chest or abdominal X-rays, or lumbosacral spine X-rays.
For stone prevention, Asan Medical Center says the most important step is keeping daily urine output at 2L or more. It recommends drinking at least 10 glasses of water a day. It says there is no need to restrict calcium, that about 3 glasses of milk a day is fine, and that high-dose vitamin C of 2g or more a day should be avoided. This is useful to keep in mind if you spend long days walking around Seoul.
Left flank pain can come from muscles, the spine, the digestive system or the kidneys. According to the official sources, the symptoms that come with it matter more than the location. Fever and chills point toward a kidney infection. Severe pain with blood in the urine matches the urinary stone description. Pain that spreads from the upper abdomen to the left flank and worsens after meals or when lying flat matches the pancreatitis description. Contact a doctor if the pain comes with high fever, chills, nausea or vomiting, if your urine turns red or brown, if the pain continues without explanation, or if you cannot eat or drink. The departments listed above can help you find the right place in a Korean hospital.
