Written and clinically reviewed by Dr Brendan Dias
Consultant Urologist & Robotic Surgeon · MBBS, MS (General Surgery), DrNB (Urology), IntFRCS (England), FUSANZ, FRACS (Urology)
Last clinically reviewed: 10 September 2026
Kidney stone pain has a reputation, and it earns it. Most people who experience renal colic describe it as the worst pain of their life — sudden, severe, and impossible to sit still through. What is less well known is why stones form in the first place, and how much of that is modifiable.
This guide covers the symptoms of a kidney stone, what causes them, how they are diagnosed, when the pain is an emergency, and what actually reduces the risk of the next one — from Dr Brendan Dias, urologist in Melbourne's west and north.
Symptoms of a Kidney Stone
A stone sitting quietly in the kidney often causes nothing at all — many are found incidentally on scans done for other reasons. Symptoms begin when the stone moves into the ureter and blocks the flow of urine.
- Renal colic — sudden, severe pain in the back or side below the ribs, coming in waves of 20–60 minutes
- Radiating pain — the pain moves down towards the lower abdomen, groin, testicle or labia as the stone descends
- Restlessness — unlike appendicitis or peritonitis, people with renal colic cannot lie still and tend to pace
- Nausea and vomiting — extremely common with severe colic
- Blood in the urine — visible or detected only on testing; present in most cases
- Urinary urgency and frequency — develops when the stone reaches the lower ureter near the bladder
- Burning on urination — as the stone passes into the bladder or urethra
- Cloudy or foul-smelling urine — suggests associated infection
Where the Pain Is Tells You Where the Stone Is
| Stone Position | Typical Pain Location | Other Features |
|---|---|---|
| In the kidney | Often none; dull flank ache if large | Frequently found incidentally on imaging |
| Upper ureter | Flank and back, below the ribs | Classic severe colic with vomiting |
| Mid ureter | Radiating to the lower abdomen | Can mimic appendicitis or diverticulitis |
| Lower ureter | Groin, testicle or labia | Urgency, frequency and burning appear |
| Bladder | Low central pelvic discomfort | Interrupted stream; see bladder stones |
When Kidney Stone Pain Is an Emergency
Go to an emergency department immediately if you have:
- Fever or shaking chills with the pain — this may be an infected, obstructed kidney
- Pain not controlled by ordinary pain relief
- Persistent vomiting preventing you from keeping fluids or tablets down
- Passing little or no urine
- A single functioning kidney, a transplant kidney, or pregnancy
An obstructed kidney with infection is a genuine surgical emergency. It is treated by urgently draining the kidney with a ureteric stent or nephrostomy tube; the stone itself is dealt with once the infection has settled.
What Causes Kidney Stones?
Stones form when urine becomes supersaturated — there is more dissolved mineral than the fluid can hold, so crystals form, stick together, and grow. Whether that happens depends on how concentrated the urine is, what is in it, and how much of the body's natural crystal inhibitor (citrate) is present.
The Main Risk Factors
- Inadequate fluid intake — the single biggest modifiable factor. Concentrated urine is supersaturated urine
- High salt intake — sodium drives calcium excretion into the urine, which is why salt matters more than dietary calcium
- High animal protein — increases uric acid and calcium in the urine and lowers protective citrate
- Low dietary calcium — counter-intuitively, restricting calcium increases stone risk, because dietary calcium binds oxalate in the gut
- High-oxalate foods — spinach, rhubarb, nuts, beetroot and strong tea, for oxalate formers
- Obesity and diabetes — both produce more acidic urine and raise uric acid stone risk
- Family history — roughly doubles the risk
- Hot climate and heavy sweating — fluid lost through skin is fluid not flushing the kidney
- Medical conditions — gout, hyperparathyroidism, renal tubular acidosis, inflammatory bowel disease, and bariatric surgery
- Medications — including topiramate, acetazolamide, some diuretics and excessive vitamin C
- Recurrent urinary infections — certain bacteria create struvite (infection) stones; see our UTI guide
Stone Types and What They Mean
| Stone Type | Frequency | Main Driver |
|---|---|---|
| Calcium oxalate | ~70–80% | Low fluid, high salt, high oxalate, low citrate |
| Calcium phosphate | ~10% | Alkaline urine, renal tubular acidosis, hyperparathyroidism |
| Uric acid | ~5–10% | Acidic urine, gout, obesity, diabetes — can be dissolved medically |
| Struvite (infection) | ~5% | Urea-splitting bacteria; can grow into large staghorn stones |
| Cystine | <1% | Inherited condition; presents young and recurs frequently |
This is why we ask you to catch and keep the stone if you pass one. Stone analysis changes the prevention plan — a uric acid stone can often be dissolved with urinary alkalinisation, whereas a calcium oxalate stone cannot.
How Kidney Stones Are Diagnosed
- CT KUB — a low-dose, non-contrast CT of the kidneys, ureters and bladder; the gold standard, showing size, position and density
- Ultrasound — first choice in pregnancy and useful for monitoring known stones
- Urine tests — for blood and infection
- Blood tests — kidney function, calcium, urate and inflammatory markers
- Metabolic stone workup — a 24-hour urine collection plus blood tests for recurrent or young stone formers, identifying the specific abnormality driving stone formation
Will the Stone Pass?
Size is the strongest predictor:
- Under 5mm — around 70–80% pass spontaneously, usually within four weeks
- 5–10mm — around 40–50% pass; many need intervention
- Over 10mm — rarely pass; treatment is generally required
While waiting for a small stone to pass, treatment is supportive: good fluid intake, regular anti-inflammatory pain relief unless contraindicated, and sometimes tamsulosin to relax the lower ureter. You will be given a strainer to catch the stone, and asked to return promptly if fever develops.
When a stone does need treating, the options include ureteroscopy with laser lithotripsy, shockwave therapy (ESWL), and PCNL or miniPCNL for large or staghorn stones — all covered in detail in our guide on kidney stone treatment options in Melbourne.
Preventing the Next Stone
Without prevention, roughly half of people who form a stone will form another within 5–10 years. The fundamentals:
- Fluid — enough to produce about 2.5 litres of pale urine daily; more in summer or if you work outdoors
- Reduce salt — under 5g of salt per day lowers urinary calcium substantially
- Moderate animal protein — keep meat and fish to sensible portions
- Keep normal dietary calcium — do not cut dairy; take calcium with meals rather than between them
- Citrate — lemon juice in water, or prescribed potassium citrate, inhibits crystal formation
- Limit high-oxalate foods — only if you are a confirmed oxalate former
- Targeted medication — thiazides, allopurinol or citrate, based on your metabolic workup
Our kidney stone prevention diet guide goes into each of these in more depth.
When to See a Urologist
See Dr Brendan Dias if you have a stone that has not passed after four weeks, a stone larger than 5mm, recurrent stones, a stone causing obstruction or recurrent infection, or a single kidney. Dr Dias offers the full range of stone treatments and metabolic prevention planning, and consults across Melbourne's western and northern suburbs, with referrals seen within two weeks.
Frequently Asked Questions
What are the first symptoms of a kidney stone?
The first symptom is usually sudden, severe pain in the back or side below the ribs, which comes in waves and may radiate down towards the groin. This is called renal colic. It is often accompanied by nausea, vomiting, restlessness, blood in the urine, and a frequent urge to pass urine as the stone moves closer to the bladder.
What causes kidney stones?
Kidney stones form when the urine becomes concentrated enough for minerals to crystallise and clump together. The most common contributors are not drinking enough fluid, a high-salt diet, high animal protein intake, obesity, certain medications, and medical conditions such as gout, hyperparathyroidism, and inflammatory bowel disease. Around 80% of stones are calcium oxalate. A family history significantly increases risk.
How painful is a kidney stone?
Renal colic is widely described as one of the most severe pains in medicine, frequently compared to or rated above childbirth. The pain comes in waves lasting 20–60 minutes as the ureter spasms around the stone. Unlike most abdominal pain, people with renal colic cannot find a comfortable position and tend to pace or move constantly.
Can a kidney stone pass on its own?
Yes, frequently. Stones under 5mm pass spontaneously in roughly 70–80% of cases, usually within four weeks, with fluids and pain relief. Stones of 5–10mm pass around 40–50% of the time and often need help. Stones larger than 10mm rarely pass and generally require surgical treatment such as ureteroscopy with laser lithotripsy.
When is a kidney stone an emergency?
Seek emergency care immediately if you have fever or chills with stone pain, are vomiting and cannot keep fluids down, have pain that is not controlled by ordinary pain relief, are passing very little or no urine, or have only one functioning kidney. Fever with an obstructing stone can mean an infected, blocked kidney — a surgical emergency requiring urgent drainage.
How are kidney stones diagnosed?
A non-contrast CT scan of the kidneys, ureters and bladder (CT KUB) is the definitive test — it identifies the size, position and density of the stone with high accuracy. Ultrasound is used in pregnancy and for follow-up. Urine testing checks for blood and infection, and blood tests assess kidney function and calcium levels.
How do I stop kidney stones coming back?
Recurrence is common — around half of people form another stone within 5–10 years without prevention. The core strategies are drinking enough fluid to produce 2.5 litres of urine daily, reducing salt, moderating animal protein, keeping normal dietary calcium, and limiting high-oxalate foods if you form oxalate stones. A metabolic stone workup identifies your specific risk factors so prevention can be targeted.
The Bottom Line
Sudden severe one-sided back pain that comes in waves, with nausea and blood in the urine, is a kidney stone until proven otherwise — and fever alongside it is an emergency. Most small stones pass, most large ones need treatment, and almost all of them are worth preventing. Knowing what your stone was made of is the single most useful step towards not having another.