Date of Award

9-22-2010

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

First Advisor

Christopher Moore

Abstract

Computed tomography (CT) is now a first-line test for renal colic, but is costly, potentially harmful, and rarely changes patient care. Hydronephrosis is often present with symptomatic kidney stones, and is reliably determined using point-of-care ultrasound at the bedside, but it is unknown whether the presence of hydronephrosis indicates a large stone that is more likely to require intervention (6mm or greater). We hypothesized that while hydronephrosis would be associated with symptomatic ureterolithiasis, neither the presence nor the degree of hydronephrosis would accurately predict the size of urinary tract stone. This was a two-center retrospective study of randomly selected patients from a 4-year period, abstracted by a single blinded reviewer. We obtained a list of all patients who received a CT scan for suspected renal colic between 04/05 04/09. Hematuria was defined as >5RBCs per HPF. Symptomatic stones were defined as those in the renal pelvis, ureter or bladder. The presence and the degree of hydro were reported as they appeared in the dictated CT result. 630 charts were randomly selected from 2973 records. 53 charts were excluded because they didnt include urinalyses, and 15 were excluded because of age <18 years, leaving 562 chart records for analysis. 48% were male with a mean age of 45 years. 216 (38%) had no stone, 71 (13%) had asymptomatic stones, and 275 (49%) patients had symptomatic stones. Of the patients with symptomatic stones, 29 (11%) had hematuria alone, 82 (30%) had hydro alone, 154 (56%) had both hematuria and hydro, and 10 (4%) had neither. The combination of hydro and hematuria was 56% sensitive and 97% specific for detecting a symptomatic stone with a positive likelihood ratio (LR+) of 20.1 (95% CI 10.1-40.1). Of the patients with symptomatic stones, 229 (83%) were small and 46 (17%) were large. Hydronephrosis alone did not distinguish large stones from small stones (OR 1.7, 95% CI 0.6-4.7), though moderate or severe hydronephrosis was mildly indicative of a larger stone (OR 3.1, 95% CI 1.4-6.9). The combination of hydronephrosis and microscopic hematuria as a predictor of symptomatic urinary tract stone disease has a greater specificity and positive likelihood ratio than either parameter alone. Hydronephrosis of any degree does not distinguish stones likely to require intervention (6mm or greater) from those unlikely to require intervention, though moderate/ severe hydronephrosis is associated with larger stones. The results of this study may be helpful in the creation of a clinical decision rule to limit the use of CT scans for patients with suspected renal colic.

Comments

This is an Open Access Thesis.

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