<h1><br></h1><h2>Definition of a Renal Abscess</h2><p>A renal abscess is a collection of pus within the kidney. The kidney infection may extend into the retroperitoneum. </p><h2>Etiology of Renal Abscess</h2><h3>Gram-negative Bacteria: </h3><p>A renal abscess is most common caused by gram-negative bacteria such as E. coli and Proteus. <a href="http://www.urology-textbook.com/acute-pyelonephritis.html"><u><font color="#0066cc">Ascending urinary tract infections (pyelonephritis)</font></u></a>, tubular obstruction and nephrolithiasis are common risk factors for a renal abscess. Perinephric abscess may result from the rupture of a renal abscess with cortical location. </p><h3>Staphylococci:</h3><p>Before the antibiotic era, renal abscesses were often caused by the hematogenous spread of staphylococci. Today's risk groups for hematogenous spread of staphylococci: intravenous drug abuse, intensive care, dialysis patients, valvular heart disease and endocarditis. </p><p>. </p><h2>Signs and Symptoms of a Renal Abscess</h2><ul title="symptoms of a renal abscess"><li>Fever and chills</li><li><a href="http://www.urology-textbook.com/abdominal-pain.html"><u><font color="#0066cc">Flank pain or abdominal pain</font></u></a></li><li>Weight loss, malaise</li><li>Urosepsis</li></ul><h2>Kidney Abscess: Diagnostic Work-Up </h2><h4>Urine culture:</h4><p><a href="http://www.urology-textbook.com/urine-culture.html"><u><font color="#0066cc">Urine culture</font></u></a> can often isolate the responsible bacteria and is needed for antibiotic resistance testing. </p><h4>Laboratory tests:</h4><p>Blood culture (positive in 50%). Blood count, coagulation tests, CRP, liver enzymes, creatinine. In suspected urosepsis, determination of sepsis parameters such as blood gas testing, AT III and fibrinogen.</p><h4>Ultrasonography:</h4><p>Sonographic signs for a renal abscess in <a href="http://www.urology-textbook.com/renal-ultrasound.html"><u><font color="#0066cc">renal ultrasound</font></u></a> are a hypoechoic mass within the renal capsule, which may have inclusion of air (echogenic reflex with dorsal shadowing). Doppler sonography may show increased blood flow at the margin of the renal abscess, whereas blood flow is often not visible in the center of the mass. </p><h4>Computed tomography:</h4><p>CT is the diagnostic test of choice [fig. <a href="http://www.urology-textbook.com/renal-abscess.html#perinephritischer_abszess_ct"><u><font color="#0066cc">perinephric abscess</font></u></a>]. The perinephric abscess appears as a hypodense area. Air inclusion is possible. After administration of contrast media, there is an ring-like enhancement of the abscess capsule. </p><p><br></p><div><a name="renal_abscess_CT1"></a> <table><tbody><tr><td width="45%"><img title="renal abscess" alt="figure: CT of a septated left-sided renal abscess with air inclusions." src="https://img1.daumcdn.net/relay/cafe/original/?fname=http%3A%2F%2Fwww.urology-textbook.com%2F01%2Frenal_abscess_CT1.jpg"></td></tr><tr><td width="45%" style="vertical-align: bottom;"><p><strong>Septated left-sided renal abscess and perinephric abscess with air inclusions.</strong> By courtesy, Dr. G. Antes, Kempten. </p></td></tr></tbody></table></div><p><br></p><h4>Intravenous urography:</h4><p>Intravenous urography has only historical value in suspected renal abscess and is now replaced by CT. If done, KUB x-ray may show an increased renal shadow and nephrolithiasis. The excretion of contrast media is often delayed with displacement of the pyelocaliceal system. Urography may be normal and may fail to diagnose renal abscess. <br></p>
<!-- -->
