…but the obvious predictors are, well, obvious.
Ureterolithiasis sounds miserable. Luckily, it is typically self-limited, temporary, and results in minimal lasting morbidity. However, infected ureterolithiasis is a higher-risk clinical syndrome – and, even worse, infected, obstructed ureterolithiasis is a potential urologic emergency. Thus, suspected infected ureterolithiasis certainly ought to be considered for imaging.
In this review of consecutive patients with suspected ureterolithiasis, 7.8% had concomitant urinary tract infection verified by urine culture. Female, fever, and history of urinary tract infection were fair predictors of UTI, and increasing levels of pyuria and nitrates on urinalysis were strong predictors. Overall, the presence of greater than 5 WBCs/hpf on microscopic examination was 86% sensitive and 79% specific for UTI. No predictive feature was universally present, and specificity could be increased only at significant cost to sensitivity.
So, UTI complicating ureterolithiasis is uncommon and inconclusively diagnosed – but the strongest predictors are the obvious ones we’ve been accounting for already.
Fun tidbit: Stone size ranged from 1 to 50mm. 50mm!
Somewhat-related plea: These folks performed CT on ~90% of patients. Many cases of ureterolithiasis can be diagnosed to reasonable certainty simply on clinical grounds. Stop the cost/irradiation madness!
Somewhat-related plea #2: There isn’t any proven pro-expulsion therapy. All the tamulosin trials are small, manufacturer-sponsored, and non-compelling. IV fluids also don’t help. If the benefits aren’t proven, then all you have left are costs & potential harms.
“Association of Pyuria and Clinical Characteristics With the Presence of Urinary Tract Infection Among Patients With Acute Nephrolithiasis”
http://www.ncbi.nlm.nih.gov/pubmed/23850311