Do non-obstructing kidney stones cause pain?

Non-obstructing Kidney Stones Can Cause Pain

Yes, non-obstructing kidney stones can cause pain even when they are not causing obstruction. Recent evidence from a 2024 multicenter observational trial demonstrates that patients with non-obstructing calyceal stones experience significant pain relief and improved quality of life following stone removal 1.

Evidence for Pain from Non-obstructing Stones

Research Supporting Pain Association

• A 2024 prospective multicenter study showed that patients with non-obstructing renal stones up to 10mm had significant pain reduction after stone removal, with mean pain scores decreasing from 5.5 to 1.8 and worst pain scores decreasing from 7.2 to 2.8 at 12 weeks post-procedure 1
• The "small stone syndrome" describes patients with flank pain attributed to small (≤4mm) non-obstructing calyceal stones, with 85% reporting complete pain resolution and 15% reporting partial resolution following ureteroscopic treatment 2
• A 2008 study concluded that non-obstructing renal stones on unenhanced CT are likely to be the cause of acute pain in patients presenting with renal colic when no other cause is identified 3

Natural History of Non-obstructing Stones

• In a study of 160 asymptomatic non-obstructing renal stones managed with active surveillance, 28% eventually caused symptoms during an average follow-up of 41 months 4
• Upper pole/mid renal stones were more likely than lower pole stones to become symptomatic (40.6% vs 24.3%) 4

Management of Non-obstructing Kidney Stones

Observation vs. Intervention

According to the European Association of Urology (EAU) guidelines:

• The natural history of small non-obstructing renal stones remains unclear, with spontaneous passage occurring in 3-29% of cases 5
• Symptoms develop in 7-77% of cases with non-obstructing stones 5
• Stone growth occurs in 5-66% of cases and the need for surgery in 7-26% 5

Indications for Stone Removal

The EAU guidelines recommend removal of renal stones if there is:

• Stone growth
• High risk of stone formation 5

For asymptomatic non-obstructing caliceal stones:

• Active surveillance is acceptable for stones up to 15mm according to EAU guidelines 5
• Treatment is indicated for stones that are symptomatic or causing obstruction 5
• Specific situations such as vocational reasons may warrant treatment of asymptomatic stones 5

Imaging for Kidney Stone Detection

First-line Imaging

• Non-contrast CT of the abdomen and pelvis is the first-line imaging modality for ruling out kidney stones in non-pregnant patients, with high sensitivity (up to 97%) and specificity (95%) 6
• Ultrasound is recommended as the first-line imaging modality for pregnant patients, though it has decreased sensitivity (24-57%) for smaller stones 6

Follow-up Imaging

• For follow-up of known radiopaque stones, KUB (kidney, ureter, bladder) X-ray or ultrasound are recommended to reduce radiation exposure 6
• Low-dose CT is recommended for uric acid or small stones 6

Treatment Options for Symptomatic Non-obstructing Stones

Based on stone size and location:

• For stones <10mm in the renal pelvis or upper/middle calyx: flexible ureteroscopy (fURS) or shock wave lithotripsy (SWL) are first-line treatments 5
• For stones 10-20mm: fURS, SWL, or percutaneous nephrolithotomy (PCNL) are options 5
• For stones >20mm: PCNL is the first option regardless of location 5

For lower pole stones specifically:

• <10mm: fURS or SWL are primary treatments 5
• 10-20mm: fURS and PCNL are suggested options 5

Clinical Implications

The recognition that non-obstructing stones can cause pain has important implications:

• Patients with flank pain and non-obstructing stones should not be dismissed as having pain from another cause
• Surgical removal of non-obstructing stones should be considered as a treatment option for patients with pain
• Regular follow-up imaging is important even for asymptomatic stones, as 3% of initially asymptomatic stones in one study caused silent obstruction requiring intervention 4

When evaluating patients with flank pain and non-obstructing stones, it's important to rule out other potential causes of pain, but the evidence strongly suggests that the stones themselves can be the primary pain generator, and removal can provide significant symptom relief.