What is the recommended treatment for a suspected kidney stone in an outpatient setting?

Treatment of Suspected Kidney Stone in an Outpatient Setting

For acute renal colic, administer intramuscular diclofenac 75 mg as first-line therapy, which provides superior pain relief within 30 minutes compared to opioids while avoiding dependence risks. 1, 2, 3

Immediate Pain Management

NSAIDs are the definitive first-line analgesic for acute kidney stone pain, not opioids, because they directly decrease ureteral smooth muscle tone and spasm rather than just masking symptoms. 1, 2, 3

• Diclofenac 75 mg IM is the preferred agent, with ibuprofen or metamizole as acceptable alternatives. 1, 2
• Use the lowest effective NSAID dose to minimize cardiovascular and gastrointestinal risks. 1
• Exercise caution with NSAIDs in patients with reduced glomerular filtration rate as they may worsen renal function. 1
• Reserve opioids (hydromorphine, pentazocine, or tramadol) only when NSAIDs are contraindicated due to cardiovascular disease, gastrointestinal comorbidities, hypertension, renal insufficiency, heart failure, or peptic ulcer disease. 1, 2, 3
• Avoid pethidine due to high vomiting rates. 1

Determining Outpatient vs. Inpatient Management

Immediate hospital admission is mandatory for:

• Shock or fever (sepsis with obstruction is a urologic emergency requiring urgent drainage). 2, 3
• Failure to respond to analgesia within one hour. 2, 3
• Abrupt recurrence of severe pain after initial relief. 2, 3
• Patients over 60 years of age. 2, 3
• Women with delayed menses. 2, 3

For sepsis with obstructed kidney, urgent decompression via percutaneous nephrostomy or ureteral stenting is mandatory and cannot wait. 1, 2

Conservative Management for Appropriate Outpatients

For uncomplicated ureteral stones ≤10 mm, offer observation with medical expulsive therapy (MET) if pain is well-controlled, sepsis is absent, and renal function is adequate. 1, 2, 3

Medical Expulsive Therapy:

• Prescribe alpha-blockers (tamsulosin) for stones >5 mm in the distal ureter, which increases stone-free rates to 77.3% versus 54.4% for placebo. 1, 2, 3
• Alpha-blockers provide greatest benefit for distal ureteral stones >5 mm. 1, 2
• The maximum duration of conservative treatment is 4-6 weeks from initial presentation. 1, 2, 3
• Mandatory periodic imaging is required to monitor stone position and assess for hydronephrosis. 1

Supportive Care Instructions:

• Instruct patients to drink fluids targeting urine output of at least 2.5 liters daily to promote stone passage. 4, 2, 3
• Coffee, tea, wine, and orange juice are associated with lower stone risk, while sugar-sweetened beverages should be avoided. 4, 2
• Have patients void into a container or tea strainer to catch stones for analysis. 3

Initial Diagnostic Workup

Obtain the following tests to guide management:

• Urinalysis with both dipstick and microscopic evaluation to assess urine pH, infection indicators, and identify pathognomonic crystals. 2, 3
• Serum chemistries including electrolytes, calcium, creatinine, and uric acid to identify underlying metabolic conditions. 4, 2, 3
• Renal ultrasonography as first-line imaging to quantify stone burden, with imaging within 7 days if stone has not passed. 2, 3
• Stone analysis at least once when available, as composition directs specific preventive measures. 4, 2, 3

Stone Type-Specific Medical Management

For Calcium Stones:

• Offer thiazide diuretics (hydrochlorothiazide) to patients with hypercalciuria and recurrent calcium stones. 2
• Counsel patients to limit sodium intake to 100 mEq (2,300 mg) daily and consume 1,000-1,200 mg per day of dietary calcium. 4

For Uric Acid Stones:

• Potassium citrate is first-line therapy to alkalinize urine to pH 6.0-7.2, as most patients have low urinary pH rather than hyperuricosuria. 1, 2, 3
• Oral chemolysis with alkalinization has an 80.5% success rate. 1
• Do not prescribe allopurinol as first-line therapy—urinary alkalinization is the correct initial approach. 2, 3

For Cystine Stones:

• First-line treatment includes increased fluid intake, sodium/protein restriction, and urinary alkalinization to pH 7.0. 2, 3
• Add cystine-binding thiol drugs (tiopronin) if unresponsive to dietary modifications. 2, 3

When to Refer for Surgical Intervention

For stones >10 mm, most will require surgical treatment:

• Ureteroscopy (URS) is the first-line surgical treatment for distal ureteral stones >10 mm. 1, 2
• For distal stones <10 mm, both ureteroscopy and shock wave lithotripsy are acceptable options. 1
• URS yields significantly higher stone-free rates compared to shock wave lithotripsy but has slightly higher complication rates. 1

Follow-Up Requirements

• Obtain imaging within 7 days if stone has not passed to monitor position and hydronephrosis. 2, 3
• Perform additional metabolic testing (24-hour urine collection) in high-risk or recurrent stone formers. 4
• Obtain periodic blood testing to assess for adverse effects in patients on pharmacological therapy (thiazides, allopurinol, tiopronin). 2

Critical Pitfalls to Avoid

• Do not use opioids as first-line therapy—NSAIDs are superior and avoid dependence risks. 1, 2, 3
• Do not delay admission for fever with obstruction—this represents sepsis requiring urgent drainage. 1, 2, 3
• Do not offer prolonged conservative management beyond 6 weeks without reassessment. 1, 2
• Do not use routine stenting before shock wave lithotripsy—it provides no benefit and causes frequent stent-related symptoms. 1