What is the most appropriate next step for a patient with a 2-day history of right flank pain radiating to the groin, nausea, and recent increased bone pain and fatigue, who has experienced similar symptoms before, presents with trace protein and 1+ lupocytes in the urine, and an unremarkable medical history?

Most Appropriate Next Step

The most appropriate next step is to obtain a non-contrast CT scan of the abdomen and pelvis immediately, as this patient's constellation of recurrent flank pain radiating to the groin, recent bone pain and fatigue, and proteinuria with minimal pyuria suggests either nephrolithiasis with possible underlying metabolic bone disease (such as hyperparathyroidism causing hypercalciuria) or an alternative serious diagnosis requiring urgent identification. 1, 2

Clinical Reasoning

Why Imaging is Mandatory Now

• Non-contrast CT abdomen/pelvis is the gold standard with 98-100% sensitivity and specificity for detecting urinary stones regardless of size, location, or chemical composition, and critically identifies alternative diagnoses in approximately one-third of patients presenting with acute flank pain 1, 2, 3

• The urinalysis findings are atypical for simple nephrolithiasis: trace protein with 1+ leukocytes but negative leukocyte esterase and nitrites suggests this is NOT an infectious process, yet the proteinuria requires explanation beyond simple stone disease 2

• Normal urinalysis does not exclude significant urologic pathology—over 20% of patients with confirmed urinary stones may have negative or minimal findings on urinalysis 1, 4

Red Flags Demanding Urgent Evaluation

This patient has multiple concerning features that elevate urgency:

• Recurrent episodes with previous "lost hours" (likely emergency department visits or hospitalizations) indicates this is not benign, self-limited disease 1

• New onset bone pain and fatigue over several months raises concern for metabolic bone disease (hyperparathyroidism, multiple myeloma, metastatic disease) or systemic illness that could be causing both the bone symptoms and recurrent nephrolithiasis 4

• The combination of flank pain with proteinuria may indicate glomerular disease, renal vein thrombosis, or other renal parenchymal pathology rather than simple urolithiasis 2

Specific Imaging Protocol

• Order unenhanced (non-contrast) helical CT abdomen and pelvis as the initial study—this is completed within 5 minutes and requires no contrast agent 3, 5

• If the non-contrast CT is non-diagnostic and infection or alternative diagnoses are suspected based on clinical deterioration, proceed to contrast-enhanced CT 2

Critical Management Concurrent with Imaging

While arranging urgent imaging:

• Provide rapid analgesia with NSAIDs (diclofenac intramuscular preferred) within 30 minutes and reassess pain control within one hour 1, 4

• Failure of analgesia after 1 hour mandates immediate hospital admission regardless of imaging results 1, 4

• Instruct the patient to maintain high fluid intake and strain urine to catch any passed stones 1

Additional Workup Based on Bone Pain History

Given the several months of bone pain and fatigue, the following laboratory studies should be obtained concurrently with imaging:

• Serum calcium, phosphate, parathyroid hormone (PTH), and alkaline phosphatase to evaluate for hyperparathyroidism, which causes both recurrent calcium stones and bone pain 4

• Serum albumin to determine if nephrotic syndrome is present, which would explain the proteinuria 2

• Complete blood count and comprehensive metabolic panel to assess for systemic illness, anemia, or renal impairment 4

Decision Points After CT Results

If Ureterolithiasis Confirmed:

• Stones <5 mm: Conservative management with hydration, analgesia, and outpatient follow-up with fast-track radiology within 7 days 1

• Stones >5 mm or complete obstruction: Urgent urology referral within 7-14 days for consideration of endoscopic removal 1, 2

• Pursue metabolic stone workup including 24-hour urine collection for calcium, oxalate, citrate, and uric acid given recurrent episodes 4

If CT Shows Alternative Diagnosis:

• CT identifies extraurinary causes in one-third of patients with flank pain, including right colonic diverticulitis, appendicitis, gynecologic pathology (ovarian torsion, ectopic pregnancy if reproductive age), or vascular emergencies 1, 3

• Management depends on specific diagnosis identified 1

If CT is Negative for Obstruction:

• The presence of proteinuria without clear stone disease requires renal biopsy consideration when nephrotic-range proteinuria is present without clear etiology on imaging, or when suspicion for glomerular disease is high 2

• Consider renal vein thrombosis, especially if proteinuria is significant 2

Common Pitfalls to Avoid

• Do not assume all flank pain is kidney stone-related—the bone pain and fatigue history suggests systemic disease that must be investigated 1, 4

• Do not delay imaging based on minimal urinalysis findings—the clinical presentation (recurrent flank pain radiating to groin) is classic for renal colic regardless of urinalysis results 1, 4

• Do not miss underlying malignancy—in patients with known or suspected cancer history and flank pain, evaluate for epidural/leptomeningeal metastases, bone fracture, or visceral obstruction from tumor 4

• Do not discharge without definitive imaging given the recurrent nature and systemic symptoms—this patient requires diagnosis, not empiric management 1