What could be causing my flank pain and hematuria (blood in the urine) with pinkish to reddish urine?

Flank Pain with Hematuria: Differential Diagnosis and Management

The combination of flank pain and pinkish to reddish urine (gross hematuria) most commonly indicates urolithiasis (kidney stones), but this presentation requires urgent evaluation to exclude other serious conditions including renal colic, urinary tract infection with obstruction, renal trauma, vascular abnormalities, or malignancy. 1

Immediate Assessment Required

You need urgent medical evaluation within 30 minutes if experiencing acute severe flank pain. 1 The diagnosis centers on the abrupt onset of severe unilateral flank pain radiating into the groin or genitals, accompanied by visible blood in the urine. 1

Critical Red Flags Requiring Emergency Department Evaluation

• Age over 60 years: Must exclude leaking abdominal aortic aneurysm 1
• Hemodynamic instability: Shock, persistent hypotension, or tachycardia 1
• Fever with flank pain: Suggests infected obstructed kidney (urologic emergency) 1
• Inability to control pain: Failure to respond to initial analgesia within one hour 1

Most Likely Diagnoses by Clinical Pattern

Urolithiasis (Kidney Stones) - Most Common

• Classic presentation: Sudden onset severe colicky flank pain radiating to groin with hematuria 1
• Important caveat: 11-19% of patients with confirmed kidney stones have NO hematuria on urinalysis 2
• Conversely: 51% of patients WITHOUT stones have hematuria from other causes 2
• Gold standard imaging: Non-contrast CT abdomen/pelvis (97% sensitivity) 1

Alternative Serious Diagnoses to Consider

Gross hematuria warrants urologic evaluation even when self-limited, as it carries >10-25% risk of underlying cancer or significant pathology. 1

Renal/Urinary Tract Malignancy

• Painless gross hematuria is the classic presentation of bladder or renal cancer 1
• All adults with gross hematuria require cystoscopy and imaging regardless of anticoagulation status 1

Page Kidney (Subcapsular Hematoma)

• Presents identically to nephrolithiasis with flank pain and hematuria 3
• Causes secondary hypertension through renal compression 3
• May occur without trauma history 3

Nutcracker Syndrome

• Left renal vein compression causing flank pain and hematuria 4
• Can be missed if other causes of hematuria coexist 4

Loin Pain Hematuria Syndrome

• Severe intermittent or persistent flank pain with microscopic or gross hematuria 5
• Diagnosis of exclusion with normal renal function and no infections 5
• Prevalence approximately 0.012% 5

Infection-Related

• Pyelonephritis with obstruction: Fever, flank pain, pyuria, and hematuria 1
• Requires urgent imaging and possible intervention 1

Diagnostic Workup Algorithm

Initial Evaluation (Within 30 Minutes)

1. Vital signs assessment: Blood pressure, heart rate, temperature to exclude shock and systemic infection 1
2. Abdominal examination: Establish site of maximal tenderness, exclude peritonitis 1
3. Urinalysis: While hematuria supports urolithiasis diagnosis, its absence does NOT exclude stones 1, 2

Imaging Strategy

Non-contrast CT abdomen/pelvis is the reference standard for evaluating acute flank pain with suspected urolithiasis (97% sensitivity). 1

• First-line imaging: CT abdomen/pelvis WITHOUT IV contrast 1
• Detects virtually all renal calculi regardless of composition 1
• Identifies secondary signs: ureteral dilation, perinephric inflammation 1
• Evaluates alternative diagnoses causing flank pain 1

Contrast-enhanced CT is NOT appropriate as first-line test because enhancing renal parenchyma obscures stones in the collecting system. 1

When to Obtain Additional Studies

• Renal function: Serum creatinine and BUN if obstruction suspected 6
• Complete blood count: Assess for infection or anemia from bleeding 6
• Blood pressure monitoring: Elevated BP may indicate renal vascular pathology 7

Immediate Management

Pain Control

Injectable diclofenac 75 mg intramuscularly is the preferred first-line analgesic, with pain relief expected within 30 minutes. 1

• Oral and rectal routes are unreliable in acute renal colic 1
• If NSAIDs contraindicated: morphine sulfate with antiemetic (cyclizine) 1
• If pain not controlled within 1 hour: Immediate hospital admission required 1

Supportive Measures

• Increase fluid intake 1
• Strain urine to capture any passed stones for analysis 1
• Follow-up phone call at 1 hour post-assessment 1

Urgent Urologic Referral Indications

All patients with gross hematuria require urologic evaluation with cystoscopy and imaging, even if hematuria is self-limited. 1

Additional urgent referral criteria:

• Failure of conservative pain management 1
• Imaging showing stones requiring intervention 1
• Suspected malignancy 1
• Recurrent episodes without identified cause 5

Common Pitfalls to Avoid

• Do not rely on absence of hematuria to exclude urolithiasis: 11-19% of stone patients have no RBCs on urinalysis 2
• Do not assume hematuria confirms stones: 51% of non-stone patients have hematuria from other causes 2
• Do not delay imaging in patients over 60: Must exclude vascular catastrophe 1
• Do not obtain urine cytology or molecular markers initially: These are not indicated in initial hematuria evaluation 1
• Do not withhold evaluation in anticoagulated patients: Anticoagulation does not explain away hematuria; underlying pathology must still be investigated 1