Patients with renal colic typically present with sudden onset of flank pain radiating laterally to the abdomen and/or to the groin. Patients often report a dull constant level of pain with colicky episodes of increased pain. The constant pain is often due to stretching of the renal capsule due to obstruction, whereas colicky pain can be caused by peristalsis of the ureteral smooth muscle. Many patients report associated nausea or vomiting, and some may report gross hematuria. As the stone migrates distally and approaches the bladder, the patient may experience dysuria, urinary frequency, urgency, or difficulty in urination.

Patients experiencing renal colic may present in very severe pain. Classically, these patients are unable to find a comfortable position and are often writhing or constantly pacing around the examination table. The exam may reveal flank pain more commonly than abdominal pain, and the skin may be cool or diaphoretic. There is often a prior personal or family history history of stones, recent ureteroscopic surgery, or just after removal of a double J stent. 

In the case of recent ureteroscopy or immediately after removal of a double J stent, the history alone can provide the diagnosis. In these cases, the renal colic is due to ureteral spasm which effectively causes an obstruction with resultant proximal ureteral and renal dilation even without a stone. The pain can be just as intense as from an obstructing ureteral stone.

Diagnosis is made through a combination of history and physical exam, laboratory testing, and imaging studies. Urinalysis shows some degree of microscopic or gross hematuria in 85% of stone patients, but should also be evaluated for signs of infection (e.g., white blood cells, bacteria). Urinary pH greater than 7.5 may be suggestive of a urease producing bacterial infection, while pH values less than 5.5 may indicate the presence of uric acid calculi.

A basic metabolic panel (BMP) should be obtained to assess for renal function, dehydration, acid-base status, and electrolyte balance. Serum calcium should be checked. A complete blood count (CBC) can be considered to evaluate for leukocytosis if there is a concern for infection although a mild elevation of WBCs is common secondary to white blood cell demargination.

Hematuria is present in 85% of acute renal colic cases caused by calculi. While the presence of hematuria is suggestive of a stone, it is not definitive and neither does the absence of hematuria prove that a stone is not present. 

Consider obtaining a parathyroid hormone (PTH) level if hypercalcemia is present and therefore primary hyperparathyroidism is suspected. If possible, urine should be strained to capture stones for chemical analysis to help determine optimal preventive prophylactic measures. Further metabolic testing, such as a 24-hour urine collection for volume, pH, calcium, oxalate, uric acid, citrate, sodium, magnesium and potassium concentrations, should be considered in high-risk first-time stone formers, pediatric patients or recurrent stone formers. It is highly recommended in nephrolithiasis patients with solitary kidneys, renal failure, renal transplants, gastrointestinal (GI) bypass, and any patient with high or increased anesthesia risk.

Renal ultrasonography can be used to establish hydronephrosis and measure resistive index and track larger renal stones (especially uric acid), but it will often miss stones smaller than 5 mm in size and is not a reliable imaging modality for visualizing ureteral calculi. The degree of perinephric fluid can be a predictor of the degree of obstruction.[3] Resistive index can be useful in diagnosing ureteral obstructions. It is defined as (peak systolic velocity - end diastolic velocity)/ peak systolic velocity) where normal is typically 0.7 or less. Higher levels indicate either obstruction or intrinsic renal disease. [11][12]  

Unenhanced (or helical) CT is the gold standard for the initial diagnosis of suspected renal colic; with a sensitivity of 98%, the specificity of 100%, and negative predictive value of 97%. This modality allows rapid identification of stone, provides information as to the location and size of the stone, and any associated hydroureter, hydronephrosis, or ureteral edema, and can give information regarding potential other etiologies of pain (e.g., abdominal aortic aneurysm, malignancy). In those patients with no previous history of nephrolithiasis, CT should be performed to guide management. CT scans may underestimate stone size in comparison with an intravenous pyelogram or abdominal x-ray. 

However, CT scans do expose patients to a significant radiation burden and they can be costly. In some patients with a history of renal colic that present with pain similar to previous obstructing urolithiasis, it may be sufficient to perform ultrasonography (US). While US is less sensitive (60% to 76%) than CT for detecting calculi less than 5 mm, it can reliably detect hydronephrosis and evidence of obstruction (increased resistive index in the affected kidney). It is also the modality of choice for evaluating a pregnant patient with concern for renal colic. Studies have shown that using ultrasonography as a primary imaging modality does not lead to an increase in complications in comparison to CT. Ultrasound is also a good way to follow a patient known to have uric acid urinary stones.

An abdominal x-ray (KUB) can identify many stones, but 10% to 20% of renal calculi are radiolucent and provide little information regarding hydronephrosis, obstruction, or the renal anatomy. Additionally, bowel gas, the bony pelvis, and abdominal organs may obstruct stone visualization. The KUB is recommended in kidney stone cases when the CT scan is positive, and the exact location of the stone is known. This helps in clearly identifying those stones that can be tracked by follow-up KUB and those that might be amenable to lithotripsy.

Combining renal ultrasound (which can easily demonstrate hydronephrosis but is less reliable in detecting stones) with a KUB (which has good sensitivity for imaging calculi but not dilation), can be very cost effective as an alternative to CT scans with lower cost and reduced radiation. Symptomatic stones are likely to produce hydronephrosis or obstruction (visible on ultrasound) or will be seen directly on the KUB. The combination of KUB radiography with renal ultrasonography provides a reported diagnostic accuracy for an obstructing stone of 90%, specificity of 93%, and a sensitivity of 88%.[13]

If the stone should pass before imaging can be performed, some evidence of residual inflammation may remain, such as hydronephrosis or pain, even if no stone is specifically or definitively identified. 

Treatment includes the following:

1. Immediate intervention with analgesia and antiemetics. NSAIDs and opiates are first-line therapies for analgesia. NSAIDs work in two ways in renal colic. First, NSAIDs decrease the production of arachidonic acid metabolites, which mediate pain receptors, alleviating pain caused by distension of the renal capsule. Additionally, they cause contraction of the efferent arterioles to the glomerulus, causing a reduction in glomerular filtration, and reducing hydrostatic pressure across the glomerulus. Because patients are frequently unable to tolerate oral medications, parenteral NSAIDs such as ketorolac (15 mg to 30 mg intravenously (IV) or intramuscularly (IM)) or diclofenac (37.5 mg IV) are most commonly used. [5][6]
2. Successful use of intravenous lidocaine for renal colic has been reported. The protocol is to inject lidocaine 120 mg in 100 mL normal saline intravenously over 10 minutes for pain management. It has been quite effective for intractable renal colic unresponsive to standard therapy and typically starts to work in 3-5 minutes. No adverse events have been reported.[14]
3. Opiate pain medication, such as morphine sulfate (0.1 mg/kg IV or IM) or hydromorphone (0.02 mg/kg IV or IM), can also be used effectively for analgesia, especially when other measures have failed. However, opiates are associated with respiratory depression and sedation, and there is a risk of dependence associated with prolonged opiate use. 
4. Fluid hydration. Although there is no evidence to support that empiric fluid will help “flush out” a stone, many patients are dehydrated secondary to decreased oral intake or vomiting and can benefit from hydration.
5. Medical expulsive therapy. Alpha 1 adrenergic receptors exist in increasing concentration in the distal ureter. The use of alpha blockade medications (for example, tamsulosin or nifedipine) is theorized to facilitate stone passage by decreasing intra-ureteral pressure and dilating the distal ureter. However, data from randomized control trials are somewhat mixed as to whether these medications improved stone passage. The consensus opinion is they may be helpful in smaller stones in the lower or distal ureter.  They are probably of little use in larger stones in the proximal ureter.
6. Definitive management of impacted stones. There are several invasive methods to improve stone passage. These include shock wave lithotripsy, in which high energy shock waves are used to fragment stones, ureteroscopy with either laser or electrohydraulic stone fragmentation, or in rare cases, open surgery.  In the presence of infection, a double J stent or percutaneous nephrostomy may be used to help with urinary drainage of the affected renal unit with definitive stone therapy postponed until the patient is stable.
7. Optimal timing of intervention for renal colic depends on the underlying etiology. For an obstructing stone, intervention is suggested even in asymptomatic patients after 30 days due to the increased risk of scarring and other complications. 
8. Behavior modification and preventative management. Increase fluid intake to optimize urine output with a goal of 2 L to 2.5 L of urine daily. Patients with calcium stones and high urine calcium concentrations should limit sodium intake and have a goal of moderate calcium intake of 1000 mg to 1200 mg dietary calcium daily. Those with calcium stones and low urinary citrate or those with uric acid stones and high urinary uric acid should increase intake of fruits and vegetables and decrease non-dairy animal protein. They may benefit from potassium citrate supplementation. Uric acid stone formers are usually best treated with potassium citrate (urinary alkalinizer) to a pH of 6.5.  Hyperuricosuric calcium stone formers can benefit from allopurinol. Thiazide diuretics are indicated in those with high urinary calcium and recurrent calcium stones to reduce the amount of urinary calcium. Patients with hyperoxaluria should be encouraged to lower their oxalate intake (spinach, nuts, chocolate, green leafy vegetables). [14][15][16]
9. Nerve blocks can often be helpful, especially in chronic cases of flank pain. An anesthetic injection is typically injection proximal to the area of the 11th or 12th intercostal nerve. Good efficacy of a nerve block suggests a musculoskeletal or neuropathic etiology. Paraveterbral, splanchnic and intercostal nerve blocks have all shown varying degrees of efficacy in relief from flank pain.[17][18][19]
10. 24-hour urine testing for kidney stone prophylaxis is now recommended for all high risk and recurrent stone formers.  The American Urological Association Guidelines recommends informing even first time stone formers about 24-hour urine testing and prophylactic therapy. Good guidelines for interpretation of 24 hour urine tests and optimal treatment selection have been published and are now available for free download.[20]

• Aortic aneurysms
• Biliary colic
• Iliac aneurysms
• Endometriosis
• Ovarian torsion
• Peritonitis
• Pyelonephritis
• Renal cancer
• Renovascular compromise

Calculus size, location, and patient discomfort predict the likelihood of spontaneous stone passage. Approximately 90% of stones less than 5 mm pass within four weeks. Up to 95% of stones larger than 8 mm can become impacted, requiring intervention to pass.

Indications for hospital admission include a significant renal stone in a solitary kidney, severe kidney injury, an infected renal stone, intractable pain or nausea, urinary extravasation, or hypercalcemic crisis.

Patients with infected stones (e.g., nephrolithiasis plus evidence of urinary tract infection) require special and more urgent treatment. The infected stone acts as a nidus for infection and leads to stasis, decreasing the ability to manage infections. Frequently, these stones need to be removed in their entirety operatively to prevent a repeat infection and the formation of new stones.

Intervention for a stone is recommended by 4 weeks with no changes even if the patient is asymptomatic. This is due to the likelihood of scarring and other complications. It can be difficult to convince an asymptomatic patient to agree to a surgery. We have found the most effective technique is to explain the policy early so patients understand the need for a procedure if a stone or obstruction appears stuck and is not resolving on its own.

24-hour urine tests are the cornerstone of long-term preventive therapy, but they require very high levels of patient dedication and compliance to be successful. Nevertheless, they should be offered to all nephrolithiasis patients; especially those with recurrent stones and a high risk of new stone formation.

The management of renal stones is by an interprofessional team that consists of a nephrologist, emergency department physician, radiologist, urologist, and a primary care provider. The majority of renal stones pass within four weeks, but stones larger than 8 mm may require some intervention before they can pass. Healthcare workers, including nurse practitioners who see patients with kidney stones, should contact the urologist when large stones fail to pass. Urologic nurses are involved in treatment, monitor patients, and update the team on changes in patient status. Pharmacists review prescribed medications for appropriate dosages, interactions, and provide patient education. In some cases of infected stones, surgery may be required. Because the recurrence of kidney stones is common, the patient should be educated on fluid intake and avoidance of certain foods. The prognosis for most patients with kidney stones is good. [Level 5]