Login to Access Video or Poster Abstract: MP01-06
Sources of Funding: Funding support was provided by NIH R21-DK-109433 (TC) and NIH NIDDK K12-DK-07-006 (TC).

Introduction

Classically, acute flank pain and renal colic in nephrolithiasis is attributed to the presence of hydronephrosis and distention of the renal capsule. Patients often present with stones and no collecting system dilation, however, creating a therapeutic dilemma for urologists. Given that the biophysical mechanisms of visceral flank pain are not well understood, we aimed to characterize predictors of renal colic among stone patients without hydronephrosis.

Methods

From October 2015 to May 2016, new stone patients at the University of California, San Francisco (UCSF) were prospectively enrolled into the Registry for Stones of the Kidneys and Ureter (ReSKU). This electronic medical record (EMR) based stone registry captures patient clinical and imaging data for research purposes. For this study, we identified all patients with imaging-confirmed upper tract urinary stones and absence of hydronephrosis based on ultrasound or cross-sectional computed tomography imaging. Data analysis was performed on STATA Version 14.1 to identify factors associated with flank pain.

Results

During the study period, 116 patients with nephrolithiasis and no hydronephrosis were identified. 62.7% (n=74) had no flank pain associated with an ipsilateral stone, while 35.6% (n=42) had flank pain with an ipsilateral stone. There were no statistically significant differences between patients with and without flank pain with respect to age (60.0±2.1 vs. 57.3±2.6 years old), gender (51 vs. 45% male), smoking history (28.2 vs. 32.4% smoker), drinking history (48.7 vs. 42.3% none), BMI (28.4±1.0 vs. 26.4±1.5), or stone burden (1.86±2.6 vs. 1.80±4.0 cm). For patients with flank pain, those with renal stones were more likely to have flank pain compared with patients with ureteral stones (78.7 vs. 21.4%, p=0.018, Pearson chi-squared test).

Conclusions

Stones in the renal pelvis or calyces are more likely to cause pain in patients without hydronephrosis when compared with ureteral stones. Alternate mechanisms for acute renal colic must exist beyond obstruction and renal capsule distension. Understanding these mechanisms is critical to developing effective treatments for a subgroup of difficult-to-treat patients and warrants additional study.

Funding

Funding support was provided by NIH R21-DK-109433 (TC) and NIH NIDDK K12-DK-07-006 (TC).