Anyone who has had renal colic never forgets it: it is one of the most intense pains there is. Behind it lies nephrolithiasis, the formation of stones in the kidney or the urinary tract. It is a common problem with a strong tendency to recur, but also a very preventable one once we understand why it happens.
What they are and why they form
Stones are solid aggregates that form when the urine is too concentrated and certain substances — mainly calcium, oxalate and uric acid — crystallise and bind together. They are not all the same: the most common are calcium oxalate stones, followed by uric acid, struvite (linked to infections) and other rarer types. Knowing the type of stone is key, because it guides both treatment and prevention.
Renal colic
When a stone moves and obstructs the urinary tract, colic appears: a sudden, intense pain in the lower back or flank that may radiate to the abdomen and groin, often with nausea, restlessness and blood in the urine. Many small stones pass on their own with hydration and pain relief; others, because of their size or location, need treatment to break them up or remove them.
A stone that causes pain with fever, or that stops you passing urine, is an emergency: obstruction with infection cannot wait.
Signs that call for urgent care
- Severe flank pain that doesn't ease with usual painkillers.
- Fever or chills together with the pain (possible infection on top of the obstruction).
- Persistent vomiting or inability to pass urine.
- Heavy blood in the urine.
Preventing new stones
Stones recur often, but relapses can be greatly reduced. The measures with the strongest evidence are:
- Drink more water: the cornerstone of prevention. The usual goal is plentiful, clear urine throughout the day.
- Moderate salt: excess sodium raises the amount of calcium in the urine.
- Keep dietary calcium: restricting it is usually counterproductive; a normal intake, preferably with meals, is advisable.
- Tailor the diet to the stone type: limiting oxalate-rich foods or excess animal protein and purines when appropriate.
- Metabolic work-up in those who form recurrent stones, to treat the specific cause.
Analysing the stone's composition and running urine and blood studies makes it possible to move from "waiting for the next stone" to prevention tailored to each person. That is the goal of follow-up in the nephrology clinic.