The stone in the ER
The patient who can't find a position that helps, a CT that takes four minutes, and a decision tree that hinges on two numbers: how big and how high. Most stones pass on their own — your job is to know which ones won't, and which 'stone' is an aneurysm in disguise.
The one-liner
Non-contrast CT is the test; size and location predict passage. Stones <5 mm usually pass — offer tamsulosin 0.4 mg for distal stones 5–10 mm. NSAIDs beat opioids for the pain. The fever changes everything: that's a drainage problem, not a stone problem.
Renal colic is pain that refuses to be still. The classic story — sudden, severe loin-to-groin pain in a patient writhing on the stretcher, unable to find the position that helps — is doing real diagnostic work, because the peritonitic patient lies perfectly still and the colicky one cannot. But the same picture has a dangerous twin, and the first job in any older patient is to make sure you are not calling an aneurysm a stone.
Before anything: the mimic that kills
A ruptured or leaking abdominal aortic aneurysm presents as flank or back pain that walks and talks like a stone. In any patient over 50with a first episode of “renal colic,” the AAA is the thing you rule out before you commit to the stone story — a pulsatile mass, hypotension, or simply the wrong demographic should move your imaging and your urgency. The stone is common; the aneurysm is the one that buries people who anchored too early.
The test
Non-contrast CT of the abdomen and pelvis is the gold standard — it finds essentially every stone, sizes it, locates it, and shows hydronephrosis, all in a few minutes. Modern low-dose protocols keep the radiation under ~4 mSv, which matters because stone formers come back. Ultrasound is the first-line answer in pregnancy and in young patients you want to spare radiation, accepting that it is better at showing hydronephrosis than the stone itself.
What everyone gets wrong
Reaching for the opioid first. For acute stone pain, NSAIDs are first-line and outperform opioids — ketorolac or diclofenac reduce the ureteral wall edema and smooth muscle activity that generate the colic, not just the perception of it. Opioids are the add-on for breakthrough pain or when NSAIDs are contraindicated, not the opening move.
The two numbers that decide everything
Whether a stone passes on its own comes down to size and location:
- < 5 mm — most pass spontaneously; manage expectantly with analgesia and time.
- 5–10 mm — passage is uncertain; this is the zone where medical expulsive therapy earns its keep.
- > 10 mm — unlikely to pass; plan intervention.
Location matters because the ureter narrows at three points — the UPJ, the pelvic brim where it crosses the iliac vessels, and the UVJ — and the further down the stone already is, the better its odds.
Medical expulsive therapy
For a distal ureteric stone of 5–10 mm, offer tamsulosin 0.4 mg daily for up to 4 weeks. The α-blocker relaxes the smooth muscle of the distal ureter and UVJ, and the benefit is real but concentrated in exactly that subgroup — larger, lower stones. It does little for the small stones that would have passed anyway. Set the expectation that the patient strains urine and returns if things change.
When watchful waiting ends
The indications to stop waiting and intervene:
- Infection behind the stone— fever, a septic picture. This is the emergency; see the infected-obstructed kidney. Decompress, don’t laser.
- Refractory pain or vomitingthe patient can’t manage at home.
- Acute kidney injury, or obstruction of a solitary kidney, or bilateral obstruction.
- Failure to progress over weeks, or a stone too large to expect passage.
The fever is not a detail in the stone story. It is a different story — an obstructed, infected system that needs a drain within hours, not a stone that needs a plan.
How it eventually comes out
When intervention is needed, the menu is driven by stone size, location, and density (Hounsfield units):
- Ureteroscopy + laser — versatile, high stone-free rates, the workhorse for ureteric and many renal stones.
- Shockwave lithotripsy — non-invasive, best for smaller, softer stones; struggles with HU > ~1000 and lower-pole anatomy.
- Percutaneous nephrolithotomy — for large (> 2 cm) or staghorn renal stones; the highest clearance for big burdens.
If you remember one thing
Size and location predict the future. Small and low passes; large and high does not; and a fever anywhere in the story turns a stone-management problem into a drainage emergency. Rule out the aneurysm, reach for the NSAID, and let the two numbers do the rest.