The Roentgen Features of Renal Carbuncle

Vol. 108, December Printed in U.S.A.

THE JOURNAL OF UROLOGY

Copyright© 1972 by The Williams & Wilkins Co.

THE ROENTGEN FEATURES OF RENAL CARBUNCLE ELLIOT H. HIMMELFARB, JACK G. RABINOWITZ, MARESH N. KINKHABWALA AND JOSHUA A. BECKER From the Department of Radiology, State University of New York, Downstate Medical Center and the Kings County Huspital Medical Center, Brooklyn, New York

pathologic diagnosis of multiple small abscesses associated with chronic pyelonephritis were not included in this study. Roentgen findings varied according to the stage of presentation and pathologic development and could be classified as representative of acute, subacute and chronic stages.

Although the clinical and roentgenographic features of renal carbuncle are known, the cmTect diagnosis is established preoperatively in only 20 per cent of cases. 1 This diagnostic difficulty is related to a confusing clinical presentation and a myriad of roentgenographic findings. The onset of symptoms may at times be acute, accompanied by sepsis and simulate an acute abdomen. More often the onset is insidious and the symptoms vague. A preceding source of a pyogenic infection such as furuncle is often overlooked and urinalysis is negative or nondiagnostic. The roentgenographic changes are non-

PATHOLOGY

Renal carbuncle is defined as a localized inflammatory abscess of the kidney, usually secondary to a hematogenous spread of bacteria or to an ascending

Fm. 1. Acute carbuncle in 14-year-old patient who had abdominal pain and high fever for 5 days. A, IVP reveals incompletely filled lower calix and poorly demarcated inferior margin of right kidney. B, following operation that entailed drainage of large perinephric and lower pole abscess IVP demonstrates well functioning kidney with normal visualization of renal outline. specific. Findings ranging from partial non-function of the collecting system on excretory urography (IVP) to neovascularization resembling tumor on angiographic study have been described. 1, 2 In an effort to improve upon this diagnostic dilemma, the x-ray features of 8 patients with lesions classified as carbuncle were reviewed and correlated with the underlying pathologic stage. Patients with the Accepted for publication May 5, 1972. Caplan, L. H., Siegelman, S. S. and Bosniak, M. A. : Angiography in inflammatory space-occupying lesions of the kidney. Radiology, 88: 14, 1967. 2 Salmon, R. B. and Koehler, P. R.: Angiography in renal and perirenal inflammatory masses. Report of three cases. Radiology, 88: 9, 1967. 1

pyelonephritis. 3 The causative agent is usually staphylococcal when the carbuncle is of hematogenous origin and it is usually of the coliform group when the carbuncle is secondary to a localized pyelonephritis. The distinction between renal abscess and carbuncle is not clear and it is based essentially upon the over-all size of the lesion. In general, a renal abscess is a fairly well encapsulated collection of pus most commonly found within the renal pyramids whereas a carbuncle is a large conglomeration of many confluent inflammatory abscesses. Initially the disease is diffuse. Multiple small 3 Anderson, W. A. D.: Pathology, 5th ed. St. Louis: C. V. Mosby Co., vol. 1, p. 199, 1966.

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Fm. 2. Acute carbuncle in 2:1-year-old woman with sepsis and left flank pain. A, IVP reveals non-functioning left kidney. B, retrograde study shows downward displacement of collecting system by what appears to be mass within upper pole (arrows). C, arteriographic study reveals minimal spreading of vessels feeding upper pole and minimal displacement outlining mass. Peripheral branches are attenuated. D, nephrographic phase demonstrates relatively uniform opacification throughout kidney. However, in area involved, linear lucencies radiating inferiorly toward hilum are seen. abscesses are formed either from septic emboli lodged within the smaller vessels or via lymphatic extension from a suppurative pyelonephritis. Perirenal disease is almost always present and at one time was thought to be the primary path of entry for the organism. However, it is now believed that the perirenal infection arises secondarily via cortical lymphatics from a minute lesion in the renal cortex. 3 The disease passes into a subacute and chronic phase as the multiple abscesses coalesce, organize and form a pseudocapsule. During this sequence the carbuncle may either rupture into the pelviocaliceal system or perinephric tissue or stabilize with further encapsulation. In this chronic stage, a large necrotic area containing several foci of suppuration is separated from the rest of the kidney by a broad zone of granulation tissue. The renal tissue surrounding the lesion is virtually intact.

ROENTGK\fOGRAPHIC FEA'l'URJ,S

The roentgenographic findings correspond with the underlying pathologic changes. Acute. The early phase of renal carbuncle represents a stage of initial confluence and localization of a diffuse pyelonephritis, frequently accompanied by a surrounding perinephritis. A film of the abdomen often shows diffuse or focal renal enlargement. When perinephritis is present, the outlines of the kidney may be somewhat obscured. In addition, blurring of the iliac muscle shadow, fixation of the kidney position on inspiration and expiration, sympathetic pleural effusion and pneumonia and localized lumbar scoliosis may be present. Axial displacement of the kidney or occasional perirenal gas collection may also be noted. Renal function sometimes is diminished on IVP, although impairment is more rre,qu1entl:\ localized to the affected area (figs, A and 2, A). decrease

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F1G. 3. Left kidney reveals acute confluent carbuncle within upper pole. Dilated tubules filled with pus are noted throughout mass.

in function can be attributed to the interstitial infiltration compressing the renal tubules and vessels. Retrograde study may demonstrate non-filling or amputation of a calix or some degree of caliceal displacement (fig. 2, B). Nephrotomography reveals a poorly defined mass difficult to differentiate from normal parenchyma. With the addition of contrast medium, varying amounts of radiolucency are present within the lesion. The arteriographic findings in the acute phase demonstrate minimal spreading of the intrarenal branches with attenuation and some loss of the normal peripheral arborization pattern (fig. 2, C). In addition, the arterial flow is slowed owing to the narrowed or occluded renal artery branches. Relative lack of vessel displacement characteristic of a mass and absence of neovascularity and arteriovenous shunting are important aspects in this stao·e of this disease. Due to the inflammatory proce;s, visualization of a distinct corticomedullary junction is lost (fig. 2, D). In the nephrogram phase an illdefined blush similar to that seen on nephrotomography may be identified. This has been related to a dilated capillary network plus increased vascular permeability. 1 In 1 patient linear lucent streaks were noted throughout the involved portions of the

kidney (fig. 2, D). These streaks extended from the c?rtex to the medullary region and represented distended tubules and interstitial tissue filled with pus (fig. 3). It is possible that any interstitial process for example inflammation or edema, could produc~ this finding. Subacute or chronic. Since the difference between the pathological findings in the subacute and chronic phases is subtle, the radiological features of these 2 stages will be considered together. In these stages the roentgenographic features more clearly define a local mass (figs. 4 and 6). Renal enlargement is usually noted on an abdominal film. In addition, calcification, which may be flaky, ring-like or flocculent, is sometimes present in more advanced lesions (figs. 5 and 6). This may or may not be associated with calculi in the collecting system. When calcification is present, differentiation from renal cell carcinoma may be difficult. Renal function is frequently fair to good; IVP reveals the collecting systems to be elongated and displaced by the mass (fig. 4, A). If the carbuncle continues to develop, interval examination will show an increase in the size of the mass (fig. 6, C). Nephrotomography will demonstrate a poorly demarcated, thick-walled radiolucent lesion. In both the subacute and chronic phases many smaller cortical abscesses may be seen (fig. 4, B). The arteriographic study demonstrates a spectrum of findings extending from an avascular mass to one with marked neovascularity. In both stages draping and displacement of the vessels are present (figs. 4, C, 4, D, 5, B and 6, B). Subacute lesions may be single or rn.ultiloculated. Small vessel irregularity and fine arterial vascularization can be detected at the margins of the lesion (fig. 4, C). The latter produces a fine blush. Early venous drainage is sometimes apparent and there is no significant slowing of arterial flow. Similar findings may be seen in the chronic carbuncle, although a well defined capsule is more easily demonstrated owing to fine late arterial arborization within the capsule and compressed renal parenchyma (figs. 5, B, 6, Band C). Occasionally, hypertrophied and tortuous ureteral and capsular vessels are present. If warranted epinephrine studies will occasionally enhance th~ detail of neovascularity, particularly in centrally located lesions. These lesions are not often quiescent and sequential studies may demonstrate communication with the caliceal system following rupture of the carbuncle. This results in loss of volume of the mass due to internal drainage (fig. 4, B). With time and therapy, they may further decrease to resemble pyelogenic cysts (fig. 4, E). Perinephric abscess formation may also occur and causes either cutaneous, ureteral, intestinal or occasionally bronchial fistulas. A special type of chronic carbuncle is tumefactive xanthogranulomatous pyelonephritis, in which the abscess contains a granulomatous element with lipoid containing macrophages. 4 Calcification within 4

Becker, J. A.: Xanthogranulomatous pyelone-

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F10. 4. Subacute carbuncle in 22-year-old asymptomatic woman who presented 2 weeks after acute episode of left flank pain. Initially she was treated for possible pyelonephritis with relatively low doses of antibiotics. A, large upper pole mass is seen displacing duplicated collecting system both inferiorly and laterally. B, sequential study performed 2 weeks later reveals definite decrease in size of mass. Multiple small abscesses filling with opaque material are present. C, arteriographic study reveals obvious displacement of intrarenal vessels by multilocular avascular masses. D, on later film, small vessel irregularity is present at periphery of lesions and there is fine neovascularization at margins of expanding relatively lucent lesions. Increased opacification surrounding these areas represents combination of compressed renal tissue and fine capillary vascularization within wall of pseudocapsule. After arteriography contrast material filled abscesses. E, following further antibiotic treatment these decreased in size to resemble pyelogenic cysts.

the mass is frequently associated with renal calculi (fig. 6, A). Obstructed and arrp'.ltated calices are also common (fig. 6, B). Neova~cularity is quite prominent and simulates a hypernephroma (fig. 6, Band C). DISCUSSIO;';

The diagnosis of renal carbuncle is most strongly suggested by the presence of an enlarging mass accompanied by manifestations of focal renal infection or sepsis. These clinical findings are frequently present in the acute phase. 5 Nevertheless, many phritis. A case report with angiographic findings. Acta Radiol., 4: 139, 1966. 5 Campbell, M. F. and Harrison, J. H.: Urology,

advanced lesions are asymptomatic or indolent and mimic an intra-abdominal inflammatory process (including appendicitis, cholecystitis and pancreatitis). IVP should be performed in all patients with a somewhat confusing intra-abdominal symptomatology. It is frequently necessary to differentiate pyonephrosis from an acute and subacute carbuncle. 6 In pyonephrosis there is ureteral obstruction with a non-functioning kidney and contrast 3rd ed. Philadelphia: W. B. Saunders Co., vol. 1, p. 433, 1970. 6 Emmett, J. L. and Witten, D. M.: Clinical Urography. Philadelphia: W. B. Saunders Co., vol. 2, p. 809, 1971. .

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Fm. 5. Chronic carbuncle in 74-year-old man in whom IVP was performed prior to prostatic operation. No symptoms referable to kidney were noted. A, film of abdomen reveals mass in which ring-like calcifications are present throughout. In addition, stone is present in upper collecting system. B, arteriography performed following retroperitoneal air insuffiation revealed displacement of vessels around relatively avascular mass. During nephrogram phase remaining kidney was well demarcated. Diagnosis of multiple cysts was considered. C, 1 month later patient returned with flank pain and sepsis. Studies revealed considerable increase in size of mass. Nephrectomy was performed and moderate-sized perinephric abscess with lower pole renal carbuncle was present. Escherichia coli was cultured from lesion. medium will fill irregular dilated calices on retrograde examination. An acute carbuncle in a patient with sepsis or flank pain must be differentiated from other renal interstitial processes causing a non-functioning or poorly functioning kidney. These include acute pyelonephritis, non-bacterial interstitial nephritis, reactive interstitial nephritis (secondary to perinephric abscess or pancreatitis), renal vein thrombosis and infiltrative transitional cell pelvic carcinoma. Renal vein thrombosis and pelvic carcinoma can be diagnosed with appropriate vascular studies, such as renal arteriography, renal phlebography and cavography. The other processes may be difficult to differentiate but ancillary signs, such as loss of psoas muscle outline or loss of a sharp renal contour, are helpful. The absence of clear-cut impression of a mass should not exclude a carbuncle. In the more chronic inflammatory lesions differentiation from hypernephroma and other inflammatory processes constitutes the major diagnostic problem. Usually a single roentgen examination is inconclusive regarding the exact character and etiology of a lesion. Sequential studies based on strong

clinical suspicion may give conclusive information. Many carbuncles change form during the stage of development. This is particularly evident in carbuncles that eventually rupture into the collecting system or into the perinephric space. A definitive preoperative diagnosis of carbuncle is important since complete healing and resolution can occur with antibiotic therapy and without surgical intervention. A correct diagnosis of extensive fulminating acute carbuncle may in many instances be lifesaving. Despite all our diagnostic criteria, many lesions will probably remain indistinguishable from tumor except at operation. SUMMARY

The roentgenographic features of renal carbuncle were evaluated and noted to correspond with the underlying pathologic appearance. These were classified into acute and subacute or chronic stages. The acute phase is a relatively diffuse infection and although the kidney may be enlarged there is a decrease in function on the IVP and a diffuse spreading of the intrarenal vessels on arteriography in the area involved. However, there is no definite impres-

ROENTGEN FEATURES OF RENAL CARBUNCLE

Fm. 6. Xanthogranulomatous pyelonephritis in 74-year-old man treated 2 months previously for sepsis and right ureteral calculi. A, IVP at this time reveals large mass containing irregular areas of calcification within lower pole. Lower calix is obliterated (arrow). B, arteriographic study reveals draping of vessels around previously described mass. Prominent ureteral vessels are also visualized. C, nephrogram phase shows fairly thick and somewhat irregular wall around mass. These findings would probably suggest hypernephroma.

sion of mass. In chronic or subacute carbuncle the disease has coalesced and there is an impression of a mass displacing the collecting systems and the intrarenal vessels. In addition, neovascularity is observed in the more chronic lesions, particularly in xanthogranulomatous pyelonephritis. Renal carbuncle must be differentiated from hypernephroma and other inflammatory lesions. A

correct preoperative diagnosis can be made by correlating the clinical and roentgenographic features. Sequential studies, if feasible, are often useful in evaluating these lesions. Although the diagnosis of renal carbuncle will often be made at the operating table, it is hoped that by proper evaluation of the findings, an early clinical diagnosis may be achieved.