When should I refer a patient with renal colic due to nephrolithiasis (kidney stones) to a specialist, such as a urologist?

When to Refer a Patient with Nephrolithiasis to a Specialist

Patients with kidney stones should be referred to a urologist immediately if they have failed analgesia after one hour, fever, solitary kidney, or when there is doubt regarding the diagnosis of renal colic. 1

Immediate Referral Criteria

• Failed pain control: Patients who do not respond to analgesia within one hour should be immediately admitted to hospital 1
• Fever or signs of infection: Presence of fever with an obstructing stone represents a urologic emergency requiring immediate drainage 2
• Solitary kidney: Patients with a single kidney require immediate evaluation 1
• Diagnostic uncertainty: When there is doubt about the diagnosis of renal colic 1
• High-grade obstruction: Severe hydronephrosis visible on imaging requires prompt intervention 1

Urgent Referral Criteria (Within 1 Week)

• Stone size >5mm: Larger stones are less likely to pass spontaneously and may require intervention 1
• Stone location: Stones in the proximal ureter or renal pelvis are less likely to pass spontaneously 1
• Recurrent severe pain: Abrupt recurrence of severe pain after initial relief warrants urgent referral 1
• Imaging findings requiring intervention: When renal imaging shows a problem requiring intervention, an urgent urology appointment should be arranged within a week 1

Non-Urgent Referral Criteria

• Recurrent stone formers: Patients with ≥2 stone episodes, bilateral disease, or strong family history should be referred for metabolic evaluation 1
• Children and young adults: All patients aged ≤25 years with kidney stones should be referred for evaluation of potential genetic causes 1
• Adults >25 years with suspected inherited or metabolic disorders: These patients require specialized evaluation 1
• Stone composition: Non-calcium stones (uric acid, struvite, cystine) require specialized management 2

Diagnostic Approach Before Referral

• Imaging: Ultrasound is the primary diagnostic tool, but non-contrast CT is the standard for acute flank pain after ultrasound (sensitivity 93.1%, specificity 96.6%) 1
• Laboratory testing: Basic workup includes urinalysis, serum creatinine, uric acid, ionized calcium, sodium, potassium, blood cell count, and C-reactive protein 1
• Stone retrieval: Patients should be instructed to strain their urine to catch any passed stones for analysis 1, 2

Primary Care Management Before Referral

• Pain control: Intramuscular diclofenac 75mg is recommended as first-line treatment when diagnosis is clear and there are no signs of complications 1
• Hydration: Patients should maintain adequate fluid intake, though intensive hydration is not currently recommended 3
• Follow-up: Primary care physician should follow up with a telephone call one hour after initial assessment and analgesia administration 1
• Fast-track investigation: All patients should be offered expedited urological investigation with follow-up, ideally within seven days of symptom onset 1

Pitfalls to Avoid

• Delayed referral of patients with fever and obstruction, which can rapidly progress to sepsis 2
• Missing alternative diagnoses in atypical presentations (consider abdominal aortic aneurysm in patients >60 years, ectopic pregnancy in women with delayed menses) 1
• Inadequate pain control leading to unnecessary emergency department visits 4
• Failure to arrange appropriate follow-up imaging to confirm stone passage 1
• Overlooking metabolic evaluation in recurrent stone formers, which can prevent future episodes 2

By following these referral guidelines, primary care physicians can ensure appropriate and timely specialist care for patients with nephrolithiasis while avoiding unnecessary hospital admissions.