Can non-obstructing renal stones cause loin pain and lower abdominal pain?

Non-Obstructing Renal Stones Can Cause Loin Pain and Lower Abdominal Pain

Yes, non-obstructing renal stones can cause significant loin pain and lower abdominal pain, and surgical removal of these stones should be considered as a treatment option for symptomatic patients. 1

Pathophysiology and Clinical Presentation

Non-obstructing renal stones can cause pain through several mechanisms:

• While urinary tract obstruction is the classic cause of renal colic, small non-obstructing calyceal stones can also trigger pain, a condition sometimes referred to as "small stone syndrome" 2
• Pain may result from:
  • Microcrystal movement within the collecting system
  • Irritation of the renal parenchyma
  • Local inflammation
  • Intermittent partial obstruction not captured on imaging

The pain pattern typically includes:

• Loin pain (flank pain) on the affected side
• Lower abdominal pain that may radiate to the groin
• Pain that can be persistent or intermittent

Evidence Supporting Pain from Non-Obstructing Stones

Recent high-quality evidence confirms that non-obstructing stones can cause significant pain:

• A 2024 multicenter prospective study demonstrated that patients with non-obstructing calyceal stones up to 10mm experienced significant pain (mean pain score 5.5/10) before treatment 1
• After surgical removal of these non-obstructing stones, 86% of patients had at least a 20% reduction in pain scores, and 69% had at least a 50% reduction 1
• An earlier study found that 85% of patients with small (≤4mm) non-obstructing calyceal stones reported complete resolution of pain following ureteroscopic treatment 2

Diagnostic Considerations

When evaluating patients with loin pain and lower abdominal pain potentially caused by non-obstructing stones:

• Non-contrast CT is the gold standard for diagnosis with approximately 97% sensitivity and 95% specificity 3
• Low-dose CT protocols (<3 mSv) maintain excellent diagnostic performance while reducing radiation exposure 3
• Ultrasound with KUB radiography can be an acceptable alternative with combined sensitivity of 79-90% 3
• Consider other causes of similar pain patterns (appendicitis, diverticulitis, etc.) as part of the differential diagnosis 4

Management Approach

For patients with suspected symptomatic non-obstructing renal stones:

1. Confirm diagnosis with appropriate imaging (preferably non-contrast CT)
2. Rule out obstruction - ensure there are no signs of hydronephrosis or obstruction
3. Consider treatment options:
   • Surgical removal (ureteroscopy) should be offered as a treatment option for symptomatic patients 1
   • Active surveillance may be appropriate for truly asymptomatic stones 5

Important Caveats

• Silent hydronephrosis can occur in approximately 3% of patients with initially non-obstructing stones, highlighting the importance of follow-up imaging 5
• Lower pole stones are less likely to cause symptoms or pass spontaneously compared to upper/mid pole stones 5
• Infected stones require complete removal as they can lead to recurrent infections and sepsis 6
• Matrix stones can present atypically on imaging but still cause significant symptoms 7

Conclusion

The evidence clearly demonstrates that non-obstructing renal stones can cause significant loin pain and lower abdominal pain. The 2024 multicenter study provides the strongest evidence that surgical removal of these stones results in significant pain reduction and improved quality of life 1. Therefore, non-obstructing stones should be considered as a potential cause of loin and lower abdominal pain, and treatment should be offered to symptomatic patients.