Do infundibular renal stones cause pain?

Do Infundibular Renal Stones Cause Pain?

Infundibular renal stones typically do not cause pain unless they obstruct the collecting system or migrate into the ureter, as pain from nephrolithiasis is caused by obstruction and distension of the collecting system rather than the mere presence of a stone in the kidney. 1

Mechanism of Pain in Renal Stones

• Pain occurs through obstruction and distension of the collecting system, not from the stone's static presence in the kidney. 1
• Stones located within the kidney itself, including those in the infundibulum, can cause pain through direct irritation of the renal collecting system and inflammation of surrounding tissues. 1
• The characteristic renal colic pain is colicky in nature, with waves of severe pain followed by periods of less intense discomfort, caused by internal pressure from obstruction rather than external compression. 1, 2

Clinical Presentation Based on Stone Location

• Stones that remain in the kidney and don't cause obstruction may be completely asymptomatic and discovered incidentally on imaging. 2
• Kidney stones in non-obstructing locations, including the lower pole and infundibular regions, can cause dull, aching flank pain or be asymptomatic if not causing obstruction. 2
• Pain severity does not correlate with stone size; more severe pain does not indicate a larger stone or worse prognosis. 3

Anatomical Considerations for Infundibular Stones

• Infundibular anatomy significantly affects stone clearance and potential for obstruction. 4
• A small lower infundibulopelvic angle, long infundibular length, and tight infundibular width are unfavorable anatomical factors that can predispose to obstruction and subsequent pain. 4
• Infundibular stenosis can complicate stone management and may require specific percutaneous treatment approaches. 5

When Infundibular Stones Become Symptomatic

• Pain develops when infundibular stones cause obstruction, leading to hydronephrosis and increased pressure in the collecting system. 2
• Secondary signs of obstruction include hydronephrosis, ureterectasis, and perinephric fluid, which may not develop until 2 hours after the onset of obstruction. 6
• Stone migration from the infundibulum into the ureter triggers severe colicky pain that may radiate to the lower abdomen and groin. 2

Diagnostic Approach

• Non-contrast CT is the gold standard for diagnosing nephrolithiasis, with sensitivity as high as 97%. 1
• Ultrasound can detect hydronephrosis with up to 100% sensitivity and 90% specificity in patients presenting with acute flank pain, though it is less sensitive within the first 2 hours of presentation. 6
• The addition of color Doppler with assessment of twinkling artifact can improve sensitivity for small renal stones to 99% for stones <5 mm. 6, 1

Management Implications

• Asymptomatic infundibular stones may be observed, but indications for removal include stone growth, high risk of stone formation, or development of symptoms. 6
• Treatment decisions should consider stone size (larger stones >5mm are more likely to cause symptoms), location, and patient symptoms. 1
• The natural history of small nonobstructing renal stones shows spontaneous passage in 3-29% of cases, while symptoms develop in 7-77%, and stone growth occurs in 5-66% of cases. 6