Clinical Decision Score
Moore et al,17 authors of the Size, Topography, Location, Obstruction, Number of stones, and Evaluation (STONE) scoring system, developed a classification system for patients with suspected nephrolithiasis. This system places patients into low-, moderate-, and high-score groups, with corresponding probabilities of ureteral stone based on symptoms and epidemiological classifications.
The intent of the STONE system is to accurately predict, based on classification, the likelihood of a patient having a simple ureteral stone versus a more significant, complicated stone and to help guide which, if any, imaging studies are indicated. For example, a lower STONE score would help guide the decision to defer advanced imaging studies that would be unlikely to reveal an alternate serious diagnosis. Likewise, an individual with a high STONE score could potentially receive ultrasonography, reduced-dose CT, or no further imaging.
The STONE score performs fairly well and appears to be superior to physician gestalt, with an area under the receiver operating characteristic curve (AUC) of .78 compared to .68 with physician gestalt. This system, however, is not always accurate in its classification and has been shown to have 87% specificity at the high end to rule in stone and 96% sensitivity rate at the low end to rule out a stone. Of course, when using a clinical decision rule to rule in or rule out a stone, a tool with a very high specificity is preferred. Although the STONE scoring system does show promise, further studies are needed before it can be applied clinically.17
Treatment
Analgesia
By inhibiting prostaglandin synthesis, NSAIDs reduce inflammation and ureteral muscular hyperactivity.18 A recent Cochrane review of over 50 studies concluded that NSAIDs were effective in relieving acute renal colic pain.19 A systematic review by Holdgate and Pollock20 shows that patients treated with NSAIDs achieve greater reductions in pain scores and are less likely to require additional analgesia in the short term compared to patients treated with opioids. Although opioid medications are effective in relieving pain associated with nephrolithiasis, this class of drugs can exacerbate the nausea often associated with this condition. This same study also showed that patients who were prescribed NSAIDs following an ED visit for renal colic required less medication for pain control, experienced less nausea, and had greater improvements in their pain.20
Nevertheless, the utility of opiates as an adjunct therapy should not be overlooked. For example, in patients with renal colic, numerous studies show treatment with a combination of an NSAID and opiate provides superior pain relief compared to either treatment modality in isolation.21 Opioid analgesia may be indicated in patients in whom NSAIDs are not recommended or contraindicated (eg, elderly patients, patients with renal disease). While NSAIDs address the underlying pathophysiology associated with renal colic, they are sometimes not the best treatment option. Depending on the situation, treatment with an opioid should instead be considered.
Intravenous Fluid Therapy
A 2012 Cochrane Review of randomized control trials (RCT) on intravenous (IV) fluid therapy hydration/diuretic use concluded that there was “no reliable evidence in the literature to support the use of diuretics and high-volume fluid therapy for people with acute ureteric colic.” The review, however, did note that further investigation is warranted for a definitive answer.22 Another study by Springhart et al23 showed no difference in pain or stone expulsion between large-volume (2 L IV fluids over 2 hours) and small-volume fluid administration (20 mL/h). Regarding administration, the use of IV fluids in renal colic is no different than the usual indications for fluid therapy in the ED and should be restricted to patients with signs of dehydration or kidney injury.
Many patients with renal colic will have decreased oral intake from the pain and nausea associated with the stone and may be vomiting. Under these circumstances, it is reasonable to rehydrate the patients, even though large-volume hydration with the intent of aiding stone expulsion or improving pain has not been shown efficacious. Conversely, in addition to the perceived benefit of rehydrating patients, a small amount of fluid hydration may improve the visualization of hydronephrosis on ultrasound.24
Medical Expulsive Therapy
For many years, clinicians have considered the use of tamsulosin, an α1-receptor blocker, as well as nifedipine, a calcium channel blocker, in treating renal colic due to the theoretical benefit of reducing ureteral smooth muscle spasm/constriction thus expediting stone passage. Over the years, dozens of studies showed positive benefit in the use of medical expulsive therapy (MET). A 2014 Cochrane Review demonstrated that patients treated with α1-blockers experienced a higher stone-free rate and shorter time to stone expulsion, and concluded that α1-blockers should be offered as one of the primary treatment modalities in MET.25 This review, however, has been criticized for using a number of studies with very small patient samples, non-peer-reviewed abstracts, and low-quality study designs.26