1. Renal colic is excruciating and can lead to dangerous complications in the kidneys, so there’s a natural tendency to refer these patients to hospital right away. Yet most stones will pass spontaneously if given time, and conservative management can bring long-term benefit. The common modern method of breaking up stones using focused shockwaves (extracorporeal shockwave lithotripsy) has actually increased the recurrence rate because it leaves fragments, around which new stones can form. Passing a whole stone avoids this risk.
2. Prevalence is rising. Lifetime risk is about 12% for men and 4% for women. Patients with a history of stones are at much higher risk. If the causes aren’t treated, stones generally recur.
3. Flank or loin pain is the typical presentation, often radiating to the groin. The pain is extreme, with periodic exacerbations, and not much relieved by position changes. Differential diagnoses include peritonitis and pyelonephritis, plus salpingitis in women and testicular torsion in men. With right-sided pain, consider appendicitis. When it’s left-sided, consider diverticulitis. Remember also with left-sided pain the small but dangerous possibility of ruptured aortic aneurysm.
4. Tenderness can be a sign of obstruction or infection. Renal colic patients with fever need to be in hospital; this could signal kidney infection.
5. The urine dipstick test will reveal hematuria in 80-90% of patients with new-onset stones. But this proportion falls over the following days to about two-thirds. Negative dipstick doesn’t exclude stones.
6. The next step should be CT scan. Ordinary x-rays may miss urate and cystine stones. If you can’t get a CT scan within a week, it’s probably best to admit the patient straight away.
7. Other patients who should be admitted include: kidney transplant recipients or donors, and those with pre-existing impaired renal function, suspected bilateral involvement, uncontrolled pain or diagnostic uncertainty.
8. Once you know the size of a calculus, you can decide what intervention is necessary. Over 90% of stones < 4 mm will pass within a month, but only half of 4-6 mm stones and hardly any over 6 mm.
9. While low fluid intake can certainly trigger renal colic, very high intake doesn’t speed the passing of stones. Rather it can lead to hydronephrosis, inhibiting ureteric peristalsis and reducing the rate of spontaneous passage. Patients should drink normal, healthy amounts of water. Urate and cystine stones grow in low pH urine, while struvite stones appear at the high pH (> 7.0) of infected urine, and oxalate stones are pH-insensitive. Patients should ideally void into a container or filter to catch any calculi so they can be identified.
10. The mainstay of pain management is the NSAID diclofenac, rectal 100 mg or intramuscular 75 mg. Tramadol oral 100 mg is a less effective alternative for the NSAID-intolerant. Meperidine can supplement diclofenac in severe cases, and isosorbide dinitrate has shown efficacy when used with NSAIDs. Calcium channel or alpha-blockers can encourage stone passage.
