Kidney Stone, UTI, or Kidney Infection: How to Tell the Difference
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It hurts to urinate, your side aches, and Dr. Google offers three suspects that all sound alike: a kidney stone, a urinary tract infection (UTI), or a kidney infection. They share symptoms because they live in the same neighborhood — but they are very different problems, with very different urgency. This guide lays out how they typically differ, and the combinations that mean getting care now rather than waiting.
It is general education only. These conditions overlap, and only testing — usually a urine test, sometimes a scan — can say which one you actually have.
The Three, in One Sentence Each
- Kidney stone: a hard mineral deposit that forms in a kidney and causes trouble mainly when it moves into the narrow tube (ureter) draining the kidney.
- UTI: a bacterial infection of the lower urinary tract — the bladder and urethra.
- Kidney infection (pyelonephritis): an infection that has reached the kidney itself, usually by climbing up from a bladder infection. This is the serious one of the three.
Where It Hurts, and How
- Stone: pain is the headline — often severe, in the flank (side/back under the ribs), coming in waves as the ureter squeezes around the stone, and frequently traveling downward toward the groin. People with stone pain typically cannot find a comfortable position and pace or rock.
- UTI: pain is lower and duller — pressure or aching above the pubic bone, with burning when you urinate. Uncomfortable, rarely agonizing.
- Kidney infection: a deep, constant ache in the flank or back on the affected side — sore rather than wave-like, and often tender if the area is pressed or thumped gently.
The Company Each One Keeps
- Stone: nausea and vomiting are common; blood in the urine (pink, red, or tea-colored) is a classic companion; a constant urge to urinate when the stone nears the bladder. Fever is not a normal stone symptom (see the warning below).
- UTI: urinary frequency, urgency, burning, cloudy or strong-smelling urine, small amounts each trip. Generally no fever, or only a slight one.
- Kidney infection: fever — often high — with chills, flank pain, nausea and vomiting, plus the UTI symptoms underneath. People usually feel properly ill, not just uncomfortable.
The Combinations That Mean "Go Now"
- Fever plus flank pain — with or without a known stone. A blocked, infected kidney is an emergency: the infection cannot drain, and it can spread to the bloodstream.
- Unable to urinate at all, or vomiting so much you cannot keep fluids or medicine down.
- Pregnancy, a single kidney, a weakened immune system, or diabetes — lower the threshold for everything above; get assessed promptly.
- Pain that is severe and not controlled by the medicine you have at home.
How Doctors Tell Them Apart
A urine test is the workhorse: infection shows bacteria, white blood cells, and often nitrites; stones typically show blood. Blood tests show whether an infection has become body-wide and how the kidneys are coping. A CT scan or ultrasound finds a stone and — just as important — shows whether it is blocking drainage (a swollen kidney), which changes the treatment from "help it pass" to "we need to relieve this." Kidney infections are treated with antibiotics, sometimes in hospital; UTIs usually with a short antibiotic course; stones with pain control, fluids, time, or a procedure — depending on size, place, and whether infection is in the picture.
The Bottom Line
Burning and frequency with low pressure pain points toward a bladder infection. Severe, wave-like flank pain traveling to the groin points toward a stone. Fever, chills, and a sore flank point toward the kidney itself — and that one never waits. When the symptoms mix, and they often do, a urine test sorts it out faster than any amount of anxious searching.
Telling a stone from an infection is bedside detective work, and the detective here is you. The larger story — infections and stones scarring kidneys toward failure — is why the Cardio Renal Foundation supports research toward a future beyond dialysis, including a swallowed capsule designed to remove excess fluid through the gut. Sort the symptoms with this article; that research is aimed at the damage repeated episodes can leave behind.
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At the Cardio Renal Foundation, we believe plain-language education like this is a genuine first line of defense, and support from readers like you helps us keep publishing it for the patients and families who need it.
This article is informational only and is not meant to replace the advice of your qualified healthcare provider. As with any issues related to your health, check with your doctor.