Sonographic findings in myoglobinuric renal failure and their clinical implications

Acute Renal Failure Secondary to Rhabdomyolysis

MR imaging of the kidney was performed in 6 patients with acute renal failure (ARF) secondary to rhabdomyolysis caused by snake bite (n = 4), crush injury (n = 1), and carbon monoxide poisoning (n = 1). A test for urine myoglobin was positive in all 6 patients and MR imaging was done 6 to 18 days after the causative event of the rhabdomyolysis. MR images in all 6 patients showed globular swelling of the kidneys, preserved corticomedullary contrast on T1-weighted images, and obliteration of corticomedullary contrast on T2-weighted images. Unlike other medical renal diseases in which corticomedullary contrast is lost on T1-weighted images, preservation of the corticomedullary contrast on T1-weighted MR images with globular renal swelling was a constant finding in patients with ARF secondary to rhabdomyolysis.

B-mode sonography in acute renal failure

B-mode sonography is an extremely useful and cost-effective method to eliminate urinary obstruction as a cause of acute renal failure and should be performed on all patients in whom obstruction is likely or in whom the cause of renal failure is not apparent. The threshold should be reduced in patients with solitary kidneys and sonography is probably indicated in all transplant patients. Sonography has very little utility in the management of other patients with acute renal failure. Although sonographic changes do occur in acute tubular necrosis, they are difficult to detect in the absence of baseline studies and are nonspecific.

Sonographic evaluation of renal failure

Sonography is a critical component of the evaluation of both acute and chronic renal failure; however, most nephrologists have a limited knowledge of this procedure. The acoustic properties, limited spectrum of pathological changes, and ease of visualization of the kidneys, coupled with the safety, simplicity, and low cost of sonography, make it the modality of choice for renal imaging. This review discusses the basics of sonography as they apply to the kidney and describes the findings encountered in the more common causes of renal failure. Although many sonographic findings are nonspecific, their diagnostic use is greatly enhanced by a familiarity with the clinical presentation and a thorough understanding of renal pathophysiological characteristics. Therefore, nephrologists should be knowledgeable about renal sonography and participate in its interpretation.