Purpose: The intervention time of asymptomatic lower pole calculi remains controversial. In this prospective study we evaluated the natural history and progression rate of asymptomatic lower pole stones.
Materials and methods: Patients were followed every 6 months. Computerized tomography in even years, ultrasound scan in odd years after initial visit and abdominal plain films between these visits were evaluated. The largest diameter was measured for each calculus and the cumulative diameter was calculated for cases of multiple stones. Disease progression was defined as pain experienced during followup, stone growth or the need for intervention.
Results: A total of 24 patients, 14 male and 10 female, were followed for a mean of 52.3 months (range 24 to 72). Of the 24 patients 3 had bilateral lower pole stones. Mean cumulative stone diameter at presentation was 8.8 mm (range 2.0 to 26.0). Progression in stone size was demonstrated in 9 of 27 renal units (33.3%) with 2 (11.1%) requiring intervention. There was no need for intervention during the first 2 years of followup. Three stones passed spontaneously without any symptoms. Pain developed in 3 patients during followup, and 2 of them passed a stone and responded to the analgesics without further treatment. None of the patients had a pyelonephritic attack during followup.
Conclusions: Our results showed that observation could be considered for patients with asymptomatic lower pole stones. However, patients should be counseled about the 33% disease progression and 11% intervention rates.