[Low-grade renal trauma (part I): diagnostic validity of haematuria].

PURPOSE OF THE STUDY

The aim of the study was to evaluate the diagnostic validity of haematuria findings in patients with low-grade renal trauma.

MATERIAL AND METHODS

The group studied comprised the patients hospitalised between 1994 and 2008 in the University Hospital Královské Vinohrady, Prague, for blunt renal trauma, classified as grade I or grade II according to the Organ Injury Scaling Committee of the American Association for the Surgery of Trauma, in whom trauma to the lower urinary tract (urinary bladder and urethra) was excluded because of the mechanism of injury (direct blow to the kidney region) or by clinical examination or imaging methods. It included 116 patients (72 men and 44 women) at the age between 17 and 86 years (average, 38 years). The urine was examined for the presence of blood by clinical and laboratory methods and, based on the results, the patients were allocated to three groups with macroscopic haematuria, microscopic haematuria and negative findings, respectively. The results in each group were then related to those of the imaging methods (computed tomography /CT/ and ultrasonography /US/) and, using Epi Info Version 6 CZ software, the statistical significance was evaluated by the Chi-square test with the level of significance set at 0.5 %.

RESULTS

Haematuria, either macroscopic or microscopic, was confirmed in 102 (88 %) patients. No blood in the urine was detected in 14 (12 %) patients. Positive CT or US findings were recorded in 76 (66 %) patients with subcapsular haematoma, renal contusion or perirenal haematoma. In the patients with haematuria, the confirmation of their diagnosis by imaging methods was not significant (p=0.076). The sensitivity of macrohaematuria was 53 ;% and that of microhaematuria was 21 % the specificity was 21 % and 13 %, respectively. The sensitivity of imaging methods was 62 % and their specificity was 38 %.

DISCUSSION

A consistent exclusion of all patients diagnosed with injury to the lower urinary tract allowed us to relate haematuria in our group only to renal parenchymal trauma. The authors consider this an important part of the study method. However, although this method of patient selection was strictly observed, haematuria failed to be detected in all patients diagnosed with low grade renal trauma. The CT or US findings of renal trauma in the patients with no haematuria can be explained by the fact that the lesion occurred in the superficial renal cortex with bleeding detected as a subcapsular haematoma or perirenal collection without blood leaking into the renal tubular system. The statistical evaluation of the results confirmed the randomness of both the clinical manifestation of a trauma and the diagnostic method presentation of a renal trauma. The changes in tissues and their manifestations are highly variable including a potential negative finding without causality. Even though the group under study fails to be exactly evaluated by statistical methods, it is obvious that the validity of a diagnosis of low grade renal trauma is higher if haematuria is present together with positive CT or US findings.

CONCLUSIONS

The finding of haematuria is a valuable piece of information in low grade renal trauma. Particularly, if imaging methods fail to detect an injury, haematuria is a sign indicating renal trauma following a typical blunt force mechanism, even though our results of its evaluation were not statistically significant. The absence of macroscopic or microscopic haematuria did not exclude the existence of renal trauma in our group, and it is therefore necessary to pay increased attention to the evaluation of findings obtained by imaging methods in patients involved in a typical blunt force accident.