What could be causing my persistent dull lower back pain, primarily on the left side, accompanied by flank pain, achy limbs and joints, stiff neck, and frequent urination with a feeling of incomplete bladder emptying?

Clinical Assessment: Likely Urinary Tract Pathology with Systemic Features

You need urgent evaluation for a urinary tract infection (UTI) or bladder pain syndrome, with kidney stone disease as a key differential—your combination of left flank pain, urinary frequency (10x/day), incomplete bladder emptying, and systemic symptoms (achy joints, stiff neck) strongly suggests complicated UTI or interstitial cystitis/bladder pain syndrome (IC/BPS), and you should see a healthcare provider within 24-48 hours for urinalysis, urine culture, and possible imaging. 1

Primary Diagnostic Considerations

Most Likely: Complicated UTI or Bladder Pain Syndrome

• Your symptom pattern matches IC/BPS or complicated UTI: The combination of flank pain, pelvic discomfort, urinary frequency, and pain throughout multiple body regions (lower back, mid-back, joints, neck) is characteristic of IC/BPS, which presents with pain "throughout the pelvis and in extragenital locations such as the lower abdomen and back." 1
• The urinary symptoms are diagnostic: Frequency (10x/day), sensation of incomplete emptying, and pressure to "get it all out" with dribbling are hallmark features of bladder dysfunction associated with IC/BPS or UTI. 1
• Men with these symptoms warrant serious consideration: In males, this presentation overlaps significantly with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), characterized by pain in the suprapubic region with voiding symptoms including incomplete bladder emptying and urinary frequency. 1

Critical Differential: Kidney Stone Disease

• Left flank pain is the classic presentation: Your "traditional flank pain" on the lower left side could represent ureteral stone with obstruction—kidney stones affect 19% of men by age 70 and present with colicky flank pain due to ureteral hyperperistalsis. 2
• Urinary symptoms fit: Frequency and urgency can accompany stone disease, though the lack of hematuria (blood in urine) makes this slightly less likely. 2

Immediate Actions Required

Essential Diagnostic Workup

• Urinalysis and urine culture are mandatory first steps: These will identify infection (pyuria, bacteriuria) or hematuria suggesting stones. 1
• Non-contrast CT abdomen/pelvis is the gold standard if stone disease is suspected: This imaging has 98-100% sensitivity and specificity for detecting stones and identifies extraurinary causes in one-third of patients with flank pain. 3, 2
• Ultrasound kidneys and bladder is an acceptable alternative: Particularly useful for detecting hydronephrosis (kidney swelling from obstruction) without radiation exposure, though less sensitive for small stones. 3

Red Flags Requiring Urgent Evaluation

• Fever, chills, or worsening systemic symptoms: These would indicate possible pyelonephritis (kidney infection) or urosepsis, which requires immediate emergency care. 1
• Inability to urinate or severe pain: Suggests complete obstruction requiring urgent intervention. 1

Why Your Systemic Symptoms Matter

The Joint/Limb Achiness and Neck Stiffness

• These are consistent with IC/BPS: Patients with bladder pain syndrome commonly report pain in multiple body regions beyond the pelvis, including generalized body aches. 1
• Could represent early systemic infection: Complicated UTIs can present with malaise and body aches before frank fever develops—you're at the 48-hour window where bacteremia could be developing. 1
• Rule out reactive arthritis: Though less common, urinary tract infections can trigger reactive arthritis with joint pain and stiffness. 1

Treatment Approach Based on Diagnosis

If Complicated UTI is Confirmed

• Empiric antibiotics for 7-14 days: For men, 14 days is recommended when prostatitis cannot be excluded. 1
• Appropriate antibiotic selection depends on local resistance patterns: Combination therapy (amoxicillin plus aminoglycoside or third-generation cephalosporin) is recommended for complicated UTI with systemic symptoms. 1
• Avoid fluoroquinolones if you've used them in the last 6 months: Resistance rates make them inappropriate for empiric therapy in urology patients. 1

If IC/BPS is Diagnosed

• This is a clinical diagnosis: Based on your symptom pattern of bladder-related pain with urinary frequency and urgency, without other identifiable causes. 1
• Treatment is multimodal: Includes behavioral modifications, dietary changes (avoiding bladder irritants), physical therapy, and potentially medications targeting bladder pain. 1

If Kidney Stone is Found

• Stone size and location determine management: Stones <5mm often pass spontaneously with hydration and pain control; larger stones may require intervention. 1
• Your high water intake is appropriate: Continue this regardless of diagnosis. 1

Critical Pitfalls to Avoid

• Don't dismiss this as musculoskeletal: The urinary symptoms (frequency, incomplete emptying, dribbling) point to urogenital pathology, not just "sleeping wrong." 1
• Don't wait for fever to develop: Complicated UTIs can progress to urosepsis, which has 10% mortality—early intervention is crucial. 1
• Don't assume normal urination rules out infection: Many IC/BPS and UTI patients report pressure rather than frank pain with urination, and may even deny pain when asked directly. 1
• Don't get repeat imaging without clinical indication: If initial workup is negative, focus on clinical diagnosis of IC/BPS rather than chasing imaging findings. 1

Bottom Line

See a healthcare provider within 24-48 hours for urinalysis, urine culture, and clinical assessment. 1 Your symptom constellation—left flank pain, urinary frequency with incomplete emptying, and systemic achiness—represents either complicated UTI requiring antibiotics, kidney stone requiring imaging and possible intervention, or IC/BPS requiring specialized management. The 10x/day urination with dribbling and incomplete emptying is not normal even with high water intake and demands evaluation. 1