Acute renal colic is a form of sudden and severe flank or side pain that typically starts in the lower back and can radiate around the front of the body and toward the abdomen or groin. The most common cause of renal colic is a kidney stone that gets stuck while traveling from the kidney through the ureter, the narrow tube that carries urine from the kidney to the bladder.

The amount of pain is not related to how large the stone is or the extent of the obstruction, but smaller stones are often easier to treat as there is a better chance of them passing on their own.

Mechanisms of Obstruction

There are three ways kidney stones can cause renal colic. The most common is the stone getting stuck and causing increased pressure in the mucosa or lining of the ureter. Stones can also cause renal colic by irritating the lining of the ureter, or they can cause stretching and edema, which can block urine flow.

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Characteristics of Pain

Pain is the most common symptom of renal colic, and it usually comes on suddenly and is not relieved by position changes or over-the-counter pain medication. Symptoms usually appear at night or early in the morning, often awakening the person. That said, symptoms can appear during the day, but in these cases, the pain usually occurs more gradually and may follow heavy exercise.

About a third of patients with renal colic have severe pain within 30 minutes of first noticing any symptoms at all. The pain can last anywhere from four to 12 hours, and it may be dull and continuous, accompanied by periods of increased intensity.

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Other Symptoms

In addition to pain, people with renal colic may experience a loss of appetite, nausea, and vomiting and typically have an elevated heart rate and blood pressure. Chills and fever are not typical signs of a kidney stone or renal colic and may indicate an infection, especially if accompanied by low blood pressure.

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Risk Factors for Kidney Stones

Kidney stones are the most common cause of renal colic. Risk factors for developing kidney stones include a family or personal history of kidney stones, dehydration, obesity, inflammatory bowel disease, gastric bypass surgery, frequency urinary tract infections, and diets high in protein, sugar, and salt.

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Diagnosing renal colic involves a combination of history and physical exam, lab tests, and imaging. About 85 percent of people with renal colic from a kidney stone have blood in their urine. X-rays of the kidneys and urinary tract and CT scans can show the number of stones, as well as their size and location and the degree of blockage.

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Initial treatment of renal colic focuses on reducing pain, typically with IV NSAIDs and opiates, as patients with renal colic are often unable to tolerate taking anything by mouth. IV fluids may be necessary to prevent dehydration, not to help them pass the stone.

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Passing or Removing Stones

Most kidney stones pass on their own—about 90 percent of stones smaller than 6mm and 59 percent larger than 6mm. Some medications can help pass kidney stones if they are low enough in the urinary system, though this approach is of little use for larger stones. To eliminate those, the patient may need shock wave therapy, a urinary scope with laser treatment to break up the stone, or open surgery.

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The best way to prevent renal colic is to prevent kidney stones, which you may be able to do with some simple lifestyle changes. For many people, adequate hydration is the best approach. People who do not have kidney failure should drink between 48 and 64 ounces of water a day.

Those who live in hot climates or exercise and sweat a lot will need more. The goal should be to produce between two and 2.5 liters of urine every day.

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If kidney stones and renal colic are left untreated, complications can occur. The obstruction and subsequent irritation and inflammation that cause renal colic can cause urine to back up into the kidney.

If the ureter or any part of the urinary tract is completely obstructed, it can eventually lead to a loss of renal function. Infection is also a risk with obstruction and can be life-threatening.

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Follow-up and Prognosis

After someone experiences renal colic, they will likely need a follow-up evaluation within a week or two to determine if they are at risk for developing another obstruction. After about six weeks, doctors may do blood and urine tests to determine what caused the stones and what the patient can do to prevent more from forming, but as many as 50 percent of people who have had a kidney stone episode will have another within ten years.

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