Renal Colic Tips

Renal colic is a type of pain commonly experienced in kidney stones.The pain typically begins inthe kidney area or below it and radiates through the flank until itreaches the bladder. It may come in two varieties: dull and acute;the acute variation is particularly unpleasant and has been describedas one of the strongest pain sensations felt by humans.

Depending on the type and sizes of the kidney stones moving throughthe urinal tract the pain may be stronger in the renal or bladderarea or equally strong in both.

Last Updated -15th December 2005

Acute renal colic is probably the most excruciatingly painful eventa person can endure. Striking without warning, the pain is often describedas being worse than childbirth, broken bones, gunshot wounds, burns,or surgery. Renal colic affects approximately 1.2 million people eachyear and accounts for approximately 1% of all hospital admissions.

The overall lifetime rate of kidney stones in the general populationis approximately 12% for men and 4% for women. Having a family memberwith a history of stones doubles these rates. Approximately 30 millionpeople are at risk in the United States. Peak incidence occurs inpeople aged 35-45 years, but the disease can affect anyone at anyage. Initial stones in elderly people and in children are relativelyuncommon; however, consider kidney stones whenever acute back or flankpain is encountered, regardless of patient age. When stones occurin persons in these uncommon age groups, a metabolic workup consistingof a 24-hour urine collection and appropriate serum laboratory testingis recommended.

Renal failure and stones

While nephrolithiasis is not a common cause of renal failure, certainproblems, such as preexisting azotemia and solitary functional kidneys,clearly present a higher risk of additional renal damage. Other high-riskfactors include diabetes and struvite staghorn calculi and varioushereditary diseases such as primary hyperoxaluria, Dent disease, cystinuria,and polycystic kidney disease. Spinal cord injuries and similar functionalor anatomical urological anomalies also predispose patients with kidneystones to an increased risk of renal failure. Recurrent obstruction,especially when associated with infection and tubular epithelial orrenal interstitial cell damage from microcrystals, may activate thefibrogenic cascade, which is mainly responsible for the actual lossof functional renal parenchyma.

In emergent settings in which concern exists about possible renalfailure, the focus of treatment should be on correcting dehydration,treating urinary infections, preventing scarring, identifying patientswith a solitary functional kidney, and reducing risks of acute renalfailure from contrast nephrotoxicity, particularly in patients withpreexisting azotemia (creatinine >2 mg/dL), diabetes, dehydration,or multiple myeloma. Adequate intravenous hydration is essential tominimize the nephrotoxic effects of intravenous contrast agents. Choosingimaging studies that do not require intravenous contrast (eg, ultrasound,abdominal flat plate radiographs, noncontrast CT scans) is wise, especiallyin patients at increased risk for developing renal failure.

Predicting spontaneous stone passage

In general, smaller stones are more likely to pass spontaneously,but stone passage also depends on the exact shape and location ofthe stone and the specific anatomy of the upper urinary tract in theparticular individual. For example, the presence of a ureteropelvicjunction (UPJ) obstruction or a ureteral stricture could make passingeven very small stones difficult or impossible. If the stone is 4mm or smaller, the stone is eventually passed 90% of the time. Stones5-7 mm generally have a 50% chance of passing spontaneously. Calculilarger than 7 mm are unlikely to pass unassisted. However, nothingis more difficult in managing an acute kidney stone attack than predictingwhat will happen with the stone. Most experienced ED physicians andurologists have observed very large stones passing and some very smallstones that do not move.

Phases of the acute renal colic attack

The actual pain attack tends to occur in somewhat predictable phases,with the pain reaching its peak in most patients within 2 hours ofonset. The pain roughly follows the dermatomes of T-10 to S-4. Theentire process typically lasts 3-18 hours.

The typical attack starts early in the morning or at night, wakingthe patient from sleep. When it begins during the day, patients mostcommonly describe the attack as starting slowly and insidiously. Thepain is usually steady, increasingly severe, and continuous; somepatients experience intermittent paroxysms of even more excruciatingpain. The pain level may increase to maximum intensity in as littleas 30 minutes after initial onset or more slowly, taking up to 6 hoursor longer to peak. The typical patient reaches maximum pain 1-2 hoursafter the start of the renal colic attack.

Constant phase

Once the pain reaches maximum intensity, it tends to remain constantuntil it is either treated or allowed to diminish spontaneously. Theperiod of sustained maximal pain is called the constant phase of therenal colic attack. This phase usually lasts 1-4 hours but can persistlonger than 12 hours in some cases. Most patients arrive in the EDduring this phase of the attack.

Abatement or relief phase

During this final phase, the pain diminishes fairly quickly, andpatients finally feel relief. Relief can occur spontaneously at anytime after the initial onset of the colic. Patients may fall asleep,especially if they have been administered strong analgesic medication.Upon awakening, the patient notices that the pain has disappeared.This final phase of the attack most commonly lasts 1.5-3 hours.

Medical treatment

Initial treatment of a renal colic patient in the ED starts withobtaining intravenous access to allow fluid, analgesic, and antiemeticmedications to be administered. Many of these patients are dehydratedfrom nausea and vomiting.

Using hydration and diuretics as a therapy to assist stone passageremains controversial. Some experts believe hydration may increasethe speed of passage of a stone through the urinary tract, while othersworry that the extra liquid only increases the hydrostatic fluid pressureinside the blocked renal unit, exacerbating the pain. The ED at theauthor's affiliated hospital prefers to administer extra hydratingfluid, especially when the stone is 4 mm or smaller, but no firm datasupport either theory. Clearly, extra fluid should be administeredto patients with laboratory or clinical evidence of dehydration, diabetes,or renal failure.

Straining the urine

Collecting any passed kidney stones is extremely important in theevaluation of a patient with nephrolithiasis for stone-preventivetherapy. Yet, in a busy ED, the simple instruction to strain all theurine for stones can be easily overlooked. Knowing when a stone isgoing to pass is impossible regardless of its size or location. Evenafter a stone has passed, residual swelling and spasms can cause continuingdiscomfort for some time. Be certain that all urine is actually strainedfor any possible stones. An aquarium net makes an excellent urinarystone strainer for home use because of its tight nylon weave, convenienthandle, and collapsible nature, making it very portable; it easilyfits into a pocket or purse.

Types of Stones