Purpose: We determine the most common etiology of spontaneous perirenal hemorrhage. Materials and Methods: A MEDLINE search of the English language literature from 1985 to 1999 revealed 47 publications and 165 cases of spontaneous renal hemorrhage meeting our study entry criteria. These criteria were presentation of raw data including imaging modality, pathological confirmation (123 cases) or long-term (greater than 2 years) (42) imaging and/or clinical followup and no history of recent trauma, anticoagulant use, dialysis or renal transplant. Meta-analysis was performed using analysis of counts derived from contingency tables and pooled and stratified analysis. Results: Hemorrhage was identified by ultrasound in 56 of 100 cases (56%) and by computerized tomography (CT) in all 135 cases assessed (100%). Etiology was correctly identified with an overall sensitivity and specificity of 0.11 and 0.33 for ultrasound and 0.57 and 0.82 for CT. Angiography in 81 cases revealed active bleeding in 11. The most common etiology of spontaneous renal hemorrhage was benign or malignant neoplasm (101 cases, 61%) with angiomyolipoma being predominant (48) followed closely by renal cell carcinoma (43). Vascular disease was the next most common offender (28 cases, 17%) with polyarteritis nodosa occurring most frequently (20). Conclusions: The most common cause of spontaneous perirenal hemorrhage is renal neoplasm and approximately 50% of such neoplasms are malignant. CT is the method of choice for evaluation of perirenal hemorrhage, although its sensitivity for detection of underlying etiology is only moderate.
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