Nephrolithiasis: Clinical sciences

Nephrolithiasis, also known as renal calculi or renal stones, is a painful condition where crystals form in the kidney, potentially causing urinary tract obstruction. Renal stones usually form when urine becomes oversaturated with minerals and salts, including calcium, oxalate, and uric acid. Common renal stone types include calcium oxalate-, calcium phosphate-, uric acid-, cystine-, and struvite stones.

Now, if your patient presents with a chief concern suggesting nephrolithiasis, you should first perform an ABCDE assessment to determine if your patient is unstable or stable. If unstable, stabilize the airway, breathing, and circulation. Next, obtain IV access and put your patient on continuous vital sign monitoring, including blood pressure, heart rate, and pulse oximetry. Finally, if needed, provide supplemental oxygen.

Now, here’s a clinical pearl to keep in mind! Nephrolithiasis associated with a urinary tract infection is a medical emergency that requires immediate decompression and drainage. Left untreated, it can cause complications such as pyelonephritis, renal abscess, or even sepsis. Nephrolithiasis is also an emergency when it occurs alongside renal failure, anuria, bilateral ureteral obstruction, or a single-functioning kidney. In these cases, consult the urology team immediately.

Now that we're done with unstable patients, let’s go back to the ABCDE assessment and discuss the stable ones. In these individuals, first, obtain a focused history and physical examination and order a urinalysis. Patients with nephrolithiasis typically present with an acute onset of excruciating flank pain, along with hematuria. They may also experience dysuria, nausea, or vomiting. The physical examination usually reveals unilateral flank tenderness, and urinalysis can show red blood cells, white blood cells, and crystals in the urine.

If your patient presents with these findings, you should suspect nephrolithiasis. Next, order a non-contrast helical CT scan of the abdomen and pelvis to check for stone presence. If there’s no stones on the scan, then consider alternative diagnoses. Alternatively, if the CT scan reveals a stone, that confirms the diagnosis of nephrolithiasis.

Now here’s a clinical pearl to keep in mind! When suspecting nephrolithiasis, a helical CT scan is the preferred imaging choice over both X-rays and ultrasound, because it can detect both radiolucent and radiopaque stones as small as 1 mm. Additionally, this imaging method can identify hydronephrosis. X-rays can only detect larger radiopaque stones; while ultrasound can detect hydronephrosis, but it is not reliable for identifying stones beyond the proximal ureter.

Now, once you diagnose nephrolithiasis, your next step is pain management. This can be achieved with an intravenous nonsteroidal anti-inflammatory drug, or NSAID, such as ketorolac. Avoid opioids whenever possible, as NSAIDs provide effective pain relief and have fewer adverse effects. Opioids are reserved for patients with contraindications to NSAIDs, severe kidney function impairment, or those with inadequate pain relief with NSAIDs.

After pain management, review the CT scan to assess the stone size, which will guide treatment. If the stone measures 6 millimeters or more, it's unlikely to pass on its own, so you should consult the urology team to discuss treatment options. These can include extracorporeal shock wave lithotripsy, or endoscopic removal.

On the other hand, if the stone is less than 6 millimeters, it’s possible that it might pass on its own. In this case, observe your patient for spontaneous stone passage for 4 weeks and instruct them to strain their urine using a calculi strainer, and save any stones they pass. Additionally, consider prescribing alpha-blockers, such as tamsulosin, as this can help relax the ureteral smooth muscle to facilitate stone passage.

Next, assess whether or not the stone has passed after 4 weeks. If there is no evidence of stone passage within this time frame or if the patient continues to experience symptoms, obtain a urological consult for extracorporeal shock wave lithotripsy or endoscopic removal. Also, keep in mind that patients with unpassed renal stones are at a high risk for developing hydronephrosis. So make sure you follow these patients with a renal ultrasound every 2 weeks, to ensure there’s no hydronephrosis or proximal ureteral obstruction. On the flip side, if the stone passes, no further consultations are needed.