In a patient presenting with acute ureteric colic and red blood cells and white blood cells on urine dip‑stick or microscopy, what is the significance of these findings and how should they direct immediate management, including infection assessment, analgesia, hydration, α‑blocker therapy, imaging, and the need for antibiotics or urological intervention?

Interpretation of WBC and RBC in Acute Ureteric Colic

Significance of Hematuria (RBC)

Hematuria on dipstick or microscopy supports the diagnosis of ureteric colic but is neither sensitive nor specific enough to rule the condition in or out. 1

• Hematuria is present in approximately 80% of patients with confirmed ureteric stones, meaning 20% of genuine cases will have a negative urine dipstick 2
• The presence of RBCs does not predict stone size, location, or likelihood of spontaneous passage 3
• A negative urine dipstick for blood does not exclude ureteric colic—clinical presentation and imaging remain the diagnostic cornerstones 1, 2

Significance of Pyuria (WBC)

White blood cells in the urine do NOT predict spontaneous stone passage and should NOT influence conservative management decisions in afebrile patients. 3

• The largest contemporary cohort study (4,170 patients across 71 hospitals) found that WBC count, neutrophil count, and C-reactive protein had no association with spontaneous stone passage rates (adjusted OR 0.97,95% CI 0.91–1.04, P=0.38) 3
• This contradicts older single-center data 4 and represents the highest-quality evidence available on this question
• Pyuria alone (without fever) does not mandate antibiotics or alter the conservative management pathway 3

Critical Red-Flag Assessment: Infection Screening

Before initiating analgesia, vital signs must be checked to identify fever or hemodynamic instability—either finding mandates immediate hospital admission and urgent intervention. 2

Immediate admission criteria (any one of the following):

• Fever of any degree (suggests infected obstruction/pyonephrosis requiring urgent decompression) 2, 5
• Hemodynamic shock (systolic BP <100 mmHg, tachycardia, altered mental status) 2
• Anuria or severe oliguria (≤1 void in 24 hours) 2, 5
• Persistent vomiting despite analgesia 2
• Pain uncontrolled after 60 minutes of appropriate analgesia 1, 5

Emergency decompression pathway (when infection + obstruction coexist):

• Obtain urine culture before any intervention 2
• Initiate empiric broad-spectrum antibiotics within 1 hour (third-generation cephalosporin or aminoglycoside-based regimen) 2
• Perform urgent percutaneous nephrostomy or retrograde ureteral stenting—antibiotics alone are insufficient and timely decompression is lifesaving 2

Immediate Management Algorithm for Afebrile Patients

Step 1: Analgesia (First-Line)

Intramuscular diclofenac 75 mg is the gold-standard first-line analgesic, providing pain relief within 30 minutes and maintaining control for at least 6 hours. 1, 2, 5

• The intramuscular route is mandatory because oral/rectal administration is unreliable in acute severe pain 1, 2
• NSAIDs reduce the need for rescue analgesia by ~50% compared to opioids and cause significantly less vomiting 2, 5

Step 2: NSAID Safety Screening

Before giving diclofenac, exclude:

• Reduced GFR or pre-existing renal impairment 2, 5
• Active peptic ulcer disease or history of GI bleeding 2
• Significant cardiovascular disease (especially in elderly patients) 2
• Age >60 years: actively exclude leaking abdominal aortic aneurysm 2
• Women of reproductive age with delayed menses: exclude ruptured ectopic pregnancy 2

Step 3: Opioid Use (When NSAIDs Contraindicated)

If NSAIDs cannot be given, use morphine sulfate combined with cyclizine (anti-emetic). 1, 2, 5

• Avoid pethidine (causes vomiting in ~74% of cases and requires additional analgesia) 2, 5
• In renal impairment, fentanyl is the only safe opioid—never use morphine, codeine, or tramadol in renal failure 2, 5

Step 4: One-Hour Reassessment

Telephone follow-up 1 hour after initial analgesia is mandatory to confirm pain control and screen for fever. 1, 2

• If pain persists beyond 60 minutes, arrange immediate hospital admission 1, 5
• If fever develops, activate the emergency infected-obstruction pathway 2

Hydration and Medical Expulsive Therapy

Hydration

• Advise increased oral fluid intake (no specific volume target in guidelines) 1
• Instruct the patient to strain all urine through a fine mesh to capture the stone for laboratory analysis 1, 2

Alpha-Blocker Therapy (Tamsulosin)

Alpha-blockers are recommended ONLY for distal ureteral stones >5 mm—they provide no benefit for stones ≤5 mm. 1, 2, 5

• For stones >5 mm in the distal ureter, tamsulosin increases spontaneous passage rates by approximately 50% 2
• Approximately 90% of stones <5 mm pass spontaneously without pharmacologic assistance 1, 2
• The largest contemporary cohort study found no overall benefit from medical expulsive therapy across all stone sizes 3

Imaging and Follow-Up

Imaging Timeline

All patients—whether managed at home or admitted—should receive fast-track imaging (non-contrast CT or renal ultrasound) within 7 days to confirm stone size, location, and degree of obstruction. 1, 2

• Ultrasound alone has limited sensitivity for detecting ureteral stones (52–57% for right kidney, 32–39% for left kidney) 1
• However, normal renal ultrasound (no hydronephrosis) predicts no need for urological intervention in 90 days and allows safe conservative management 1
• Moderate-to-severe hydronephrosis on ultrasound has a 97% sensitivity for predicting subsequent urological intervention 1

Urological Follow-Up

• If the stone remains on imaging, arrange urgent urology outpatient appointment within 14 days 2

Predictors of Spontaneous Stone Passage

Stone size and position are the only clinically useful predictors of spontaneous passage—inflammatory markers (WBC, neutrophils, CRP) do not predict outcomes. 3

Spontaneous passage rates by stone size:

• <5 mm: 89% (95% CI 87–90%) 3
• 5–7 mm: 49% (95% CI 44–53%) 3

• 7 mm: 29% (95% CI 23–36%) 3

Spontaneous passage rates by location:

• Upper ureter: 52% (95% CI 48–56%) 3
• Mid ureter: 70% (95% CI 64–76%) 3
• Lower ureter: 83% (95% CI 81–85%) 3

Common Pitfalls to Avoid

• Never discharge a patient with fever and renal colic—untreated obstructive pyelonephritis carries ~10% mortality 2
• Do not rely on pyuria or elevated WBC to guide conservative management decisions in afebrile patients—these markers do not predict stone passage 3
• Do not prescribe alpha-blockers for stones ≤5 mm—they provide no benefit and expose patients to unnecessary side effects 1, 2
• Do not use standard opioid dosing in renal impairment—start with lower doses and use only fentanyl if opioids are required 2, 5
• Do not assume hematuria is always present—20% of confirmed ureteric stones have negative urine dipsticks 2