A good diagnosis is more than finding the stone. It also defines its exact size, location, density, the impact on the kidney upstream, and any infection - all of which shape the treatment plan.
The diagnosis usually starts with the history. Classic renal colic - sudden onset, severe loin-to-groin pain, restlessness, nausea - is highly suggestive of a stone, though other causes must still be excluded (see symptoms). The examination focuses on vital signs, any fever, abdominal tenderness, and whether the kidney is tender to percussion.
A urine dipstick is done at the first visit. With a stone, blood is usually detected even if not visible to the naked eye; nitrites and leucocytes suggest infection. A midstream urine sample is sent for culture because:
A low-dose non-contrast CT of the kidneys, ureters, and bladder is the first-line imaging test for acute renal colic in adults. It is fast, widely available, and highly accurate - the EAU 2025 guideline's own systematic review reports pooled sensitivity around 95 per cent and specificity around 96 per cent for urinary stones.1, 2 A low-dose CT KUB typically delivers a radiation dose comparable to a few plain abdominal x-rays.
A CT KUB tells us:
Ultrasound is the first-line imaging test in pregnancy and children, and it is often used as an initial test in the community when CT is not immediately available. Ultrasound is very good at detecting hydronephrosis but less sensitive for the stone itself - small stones, and stones in the mid ureter, are often missed. A negative ultrasound therefore does not exclude a stone.
Plain x-ray is no longer used to diagnose a new stone but is occasionally useful for follow-up of a known radio-opaque stone - for example, to track progress during conservative management, or before a shockwave treatment. Pure uric acid stones are radiolucent and do not show on plain x-ray.
Intravenous urogram (IVU) has been largely replaced by CT. MR urography is used in selected cases where ionising radiation must be avoided, particularly in pregnancy when ultrasound has not given a clear answer.
If a stone is passed or retrieved at surgery, it should be sent for mineral analysis by infrared spectroscopy or x-ray diffraction. The result directly identifies the type of stone - calcium oxalate, calcium phosphate, uric acid, struvite, or cystine - and guides preventive management.1
Patients who form more than one stone, or who form a stone when they are young, overweight, or have a strong family history, are offered a full metabolic evaluation. This is usually organised after the acute episode is over and typically includes:
Dr Kooner works with renal physician colleagues who specialise in stone disease; patients with recurrent or complex stone disease are often referred into that dedicated metabolic clinic pathway for comprehensive prevention.
If you have a CT report to hand, these are the key items that influence treatment planning:
Renal pelvis, upper/mid/lower pole of the kidney, or ureter (proximal, mid, distal). Distal ureteric stones are most likely to pass spontaneously; lower-pole kidney stones are the hardest to clear with shockwave.
Largest dimension in mm. Under 5 mm: usually passes. Over 7 mm: usually needs treatment. Over 20 mm: PCNL is first-line.
Hard stones (>1000 HU, often pure calcium oxalate monohydrate) respond less well to ESWL and are often better treated with ureteroscopy.
"None", "mild", "moderate", or "severe" describe the degree of backpressure on the kidney. Moderate or severe hydronephrosis in a symptomatic stone usually prompts earlier intervention.
Once the diagnosis is established, Dr Kooner discusses the realistic management options - observation, medical expulsive therapy, ESWL, ureteroscopy, or PCNL - with the evidence for each, so that the chosen approach is individualised to the stone and to the patient.
Arrange a consultation or request a second opinion on an acute stone, a recurrent stone problem, or a recommended procedure.