* From the Department of Radiology, State University of New York, Downstate Medical Center and Kings County Hospital Center,

Brooklyn, New York.

DECEMBER, 1972

740

ACUTE RENAL CARBUNCLE*

THE ROENTGENOGRAPHIC CLARIFICATION OF A MEDICAL ENIGMA

By JACK G. RABINOWITZ, M.D., MAHESH N. KINKHABWALA, M.D.,THEODORE ROBINSON, M.D., EFITHIMIOS SPYROPOULOS, M.D., and

JOSHUA A. BECKER, M.D.BROOKLYN, NEW YORK

]�1 OST roentgenographic descriptions ofI’J renal carbuncle emphasize the fea-

tures, depicting mainly the subacute and

chronic varieties.25’6 Although the diagnos-

tic criteria for renal carbuncle have im-proved, the over-all diagnostic accuracy

prior to surgery is still poor and rarely ex-

tends beyond 20 per cent in most series. An

even greater diagnostic challenge is the

acute renal carbuncle. This at one time was

almost never accurately diagnosed. Never-

theless, this form of renal infection is by nomeans uncommon or insignificant, and with

the problem of increasing drug addictionby “mainlining” is becoming more fre-

quent. The diagnosis may be clinically sus-

pected when symptoms of fever, chills,and pain localized to the flank, or the signs

of sepsis are present. More often, however,symptoms related to the urinary tract are

absent, and the urinalysis is practically al-

ways normal or nondiagnostic. In addition,

if one waits for gross urographic changes tooccur before making the diagnosis, muchvaluable time will be lost.4 Evans et al.,5

and Himmelfarb et al.,6 in their descriptionsof renal carbuncle, alluded to many roent-

genographic findings observed in the acutephase. Precise analysis of these findings andtheir relation to an exact diagnosis were not

stressed.The purpose of this paper is to further

analyze the major roentgenographic find-

ings of acute renal carbuncle, so that ac-

curate and definitive criteria can be estab-

lished.

CASE MATERIAL

A total of 6 patients are presented in this

paper (Table 1). Their ages range from i�

to 6o years. Surprisingly, there appears to

be an equal distribution of sex, with 3 fe-males and 3 males. Two of the men were in

the older age group and the primary diseasewas related to the prostate gland. In both,the involved organism was E. co/i. In theremaining 4 cases, the causative agent was

Staphylococcus aureus. The 3 females werein their twenties and all were drug addicts.

Furunculosis was the initial focus of infec-

tion in the remaining male patient.

PATHOLOGY

Since the roentgenographic pattern is areflection of the underlying pathologicchanges, a brief review is in order.

Acute infection of the kidney, in general,

arises either on a hem atogenous basis or via

a cysto-ureteric route. Staphylococcus au-

reus is the most common bloodborn organ-

ism and E. co/i the causative agent in as-

cending infections.

The definition of an acute carbuncle is an

area of severe suppurative pyelonephritis

containing many micro-abscesses coalescing

into larger confluent abscesses with as yetnot well defined walls. Originally, multiple

small abscesses of varying size are formedwithin the cortex from either septic embolilodged within the smaller vessels or bylymphatic extension from a suppurative

pyelonephritis arising within the medulla.

Cortical involvement stimulates a pro-nounced inflammatory response primarily

because of the large blood supply feeding

the cortex, and secondarily because of the

lower levels of interstitial pressure. Thelatter enables the cells to move easily intothe inflammatory area.8 The process maybe diffuse, virtually involving the entire

V01.. ,i6, No. Acute Renal Carbuncle 741

TABLE I

SUMMARY OF FINDINGS IN 6 CASES

CaseNo.

SexDrug

.Addict

Age(yr.)

Plain

Roentgeno-grams

IntravenousPyelograms

RetrogradePvelograms

-

�

- -

Arteriograms

a. No displacement.

D. �parse orancning-

c. LOSS Of cortico-

medullary junction

--

Lomments

furunculosis

Kesults

i. drainage andantibiotics

2. returned tonormal

I M no 14 questionable

changes

i. partial

visualization2. mass effect

II F yes 24 mass of left

kidney

nonvisualiza-

tion

i. displacement

of calyces2. mass

a., b., c.

i. surgical re-

moval2. carbuncle of

upper pole

III F yes 28 mass of

right kidney

poor visualiza-

tion

- refused 1. lost tofollow-up

i. drainage

2. clinically

improved3. intravenous

pyelogram-

normal

IV F yes 20s

?

mass of

left kidney

partial to poor

visualizationa., b., c.

V M no no mass nonvisualiza-

tion- questionable

a., b., c.prostaticcarcinoma

1. surgical re-moval

2. diffuse involve-ment

VI M no 62 not available nonvisualiza-tion

i. dilatedcalyces

2. no displace-

ment3. filling defect

in ureter

a., b., C.

septic coursefollowingprostatec-

tomy

i. surgical re-moval

2. diffuse involve-

ment

kidney, or remain limited to only a portion

or portions of the kidney. It is basically

parenchymal in location and does not com-municate with the collecting system in its

early form. Extension through the capsuleinto the perirenal tissues is nevertheless al-most always present, and at one time was

thought to be the primary site of involve-ment. It is now believed that perirenal in-

fection arises secondarily from lesions

within the renal cortex via the peripheral

lymphatics.

ROENTGENOGRAPHIC FEATURES

The roentgenographic features described

represent the composite findings of the 6

patients presented and some personal ob-servations noted in other patients. In gen-

eral, the entire spectrum of the roentgeno-graphic features prior to angiographic stud-

ies consists of a combination of changes in

dicating both the presence of interstitiaor parenchymal disease with associatedperirenal involvement.

A. FLAT FILM ROENTGENOGRAPHY OF THE ABDOMEN

With the kidney either diffusely or par-tially involved by the inflammatory process,a supine roentgenogram of the abdomen

demonstrates either diffuse or local en-largement of the renal shadow. Simultane-

ously occurring perirenal disease is commonand, when present, obscures the renal and

the psoas muscle shadows (Fig. i). In � ofour cases, pronounced perirenal involve-ment was present, causing an increased

density within the retroperitoneum as wellas associated scoliosis. In i patient, the dis-

eased kidney was also fixed during respira-tion (Fig. 2). Further extension of the pro-

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/ -�-Rabinowitz ci al. l)�.�st K, 1()72

11G. i. Plain film roentgenogram of the abdomen re-veals a vague density involving the left abdomen.Both the renal and the psoas muscle shadows are

dithcult to evaluate. Scoliosis with deviation away

from the involved area is noted.

cess into the surrounding area, displacing

the kidney and the ureter can also occur.’

B. INTRAVENOUS IVELOGRAPHY

The findings encountered on intravenous

pyelographv vary from partial to poor, to

complete nonvisualization of the collecting

systems (Fig. 3, �1-C). Partial visualiza-

tion was observed in 50 per cent of patients.

Specific calyceal changes can be noted in

the locally infected area. The calvces were

either poorl�’ opacified or amputated in con-

trast to the remaining fairly adequately

visualized collecting systems. In some cases,

the affected calvces were stretched and

draped around a suggested localized mass.

C. RETROGRADE PYELOGRAPHY

The need for retrograde pyelography in

the diagnosis of acute renal carbuncle is

limited. Most of the necessary information

can be derived from intravenous pyelog-

raphy and nephrotomography. However, in

cases where the collecting s��stems are corn-

pletely nonvisualized, this procedure may

be necessary to exclude the presence of

either ureteral obstruction by calculus or

pyonephrosis. Although the clinical presen-

tation of both these latter entities resembles

that observed in acute carbuncle, the thera-

peutic approach is quite different. Differen-

tiation is therefore very important. In i

patient with a nonvisualized collecting sys-

tem, no evidence of obstruction was dem-

onstrated by retrograde pyelography. The

calyces were well outlined and displaced

downward by a large mass in the upper pole

(Fig. �). In another patient, ureteral ob-

struction caused by tissue slough within the

ureter was demonstrated and a specific

diagnosis in this case could not be accom-

plished. Following surgical removal, the

kidney demonstrated diffuse parenchymal

disease and necrosis.

D. NEI�HROTOMOGRAPHY

Nephrotomograph v was not performed

on any of our patients. However, in our in-

stitution, as well as in others, tomography

is now being utilized almost routinek in

conjunction with high dose p\-elograph\,

and is once again becoming an important

diagnostic procedure. In patients showing

some degree of visualization, it may prove

worthwhile to eliminate the need for ar-

teriographv, speed the diagnostic time, and

FIG. 2. Roentgenogram taken during respirationshows a poorly opacifying right kidney that isfixed in position. On the left, the collecting systemsare well opacified, but mobile.

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I

Acti te l�enal Carhu ncle 743

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744 Rabinowitz et a/. I)ECEMBER, 1972

11G. 4. Retrograde pyelogram in a patient with non-

visualization of the collecting system (Fig. 3C).The study reveals moderate dilatation of the cal)’-

ceal structures, which are displaced downward bya mass within the upper pole (arrows).

spare the patient the morbidity of an addi-tional vascular procedure.

The features described during this phase

correspond to those obtained during the

nephrogram phase of arteriography, and to

some cases shown to us by our colleagues.

One major feature is the suggestion of a

renal mass, when the acute carbuncle is

localized, or renal enlargement, when dif-

fuse. The margin of the kidney, due to the

surrounding inflammatory process is poorly

defined or unsharp.’ The density of the

carbuncle, when localized, varies and may

demonstrate either opacifi cation or a vague

over-all lucency. Occasionally, multiple

lucencies, oval or rounded in configuration,

representing multiple abscesses undergoing

coalescence, may be apparent. In I patient,

linear lucencies radiating through the mass

were noted (Fig. 5). The surgical specimen

revealed these to be dilated collecting tu-

bules distended with pus. This striated

pattern may be duplicated by any diffuse

interstitial process, and has been described

in a case of renal vein thrombosis.3 (The

explanation for these findings presented in

the latter situation differs slightly from

ours.)

E. ARTERIOGRA1’HY

Arteriography was performed in � cases.

The most characteristic angiographic fea-

ture, particularly in the localized acute

carbuncle, is the absence of obvious vascu-

lar displacement by a mass despite its sug-

gested presence on all the preliminary stud-

ies (Fig. 6, 11-C). Instead, the vessels tra-

verse through the infected area regardless

of its location, with minimal, if an�’, dis-

placement (Fig. 6�1). They are, neverthe-

less, slightly spread apart and somewhat

less opacified than the vessels within the

normal portion of the kidney, in some cases,

l’IG. 5. Nephrographic phase, in a patient with anacute carbuncle localized to the left upper pole,reveals diffusely radiating linear lucencies whichon the surgical specimen were markedly dilatedtubules filled with pus. Note the normal appearing

lower pole

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VOL. ii6, No. � Acute Renal Carbuncle 745

�, ‘-�

�0

FIG. 7. Nephrogritphic phase. This is the Patient seen

in Figure 6C. There is a distinct loss of the cortico-medullary junction in the lower pole. The normalupper part of the kidney is within normal limits. Adiagnosis of an acute renal carbuncle was made,but because of the lack of clinical symptornatology,

the patient was not adequately treated. As pre-dicted, she returned 10 days following the studywith an exacerbation of the symptoms, and, at

surgery, an acute carbuncle within the lower poleof the left kidney was drained.

746 Rabinowitz et al. DFCEMBER, 1972

the affected vessels branch sparsely and ap-

pear denuded (Fig. 6, B and C). Poor and

slow perfusion within the infected area may

also be apparent. Multiple factors probably

account for these changes. The relatively

poor arborization of the vessels is appar-

ently caused by compression of these ves-

sels by the surrounding inflammatory in-

filtration. It has also been demonstrated

that in the presence of an inflammatory pro-

cess, an extensive capillary network be-

comes functional.2 This network is always

existent, but under normal conditions non-

functioning. When operational, normal exit

via existing venule pathways is distinctly

impaired and slowed. This phenomenon

may be partially responsible for the slow

perfusion noticed during the studies.

During the nephrographic phase, the nor-

mal cortico-medullarv junction is fre-

quently lost and replaced by a diffuse and

relatively homogenous blush outlining the

suggested mass noticed on the previous ex-

aminations (Fig. 7). This feature, when

present, is both distinctive and important.

In i patient who presented with a well lo-

calized acute carbuncle in which the vascu-

lar features were subtle, the loss of the

cortico-medullary junction was diagnostic

(Fig. 7). The over-all increased permeabil-ity and diffusion found at the capillary and

venule level is responsible for this feature.

In addition, most of the other findings de-

scribed under the paragraph of nephroto-

mography may be seen in this stage.

DIFFERENTIAL DIAGNOSIS

The roentgenographic findings of acutecarbuncle in the kidney must be distin-

guished from other interstitial processes

that may involve this organ; e.g., edema,

interstitial nephri tis, infiltrating tumors,

etc. In all situations, the combined features

noted on preliminary studies of interstitial

disease, either diffuse or localized, associ-

ated with a perirenal inflammatory process

should suggest the diagnosis of an acute

carbuncle. Most other interstitial renal

diseases do not demonstrate perirenal ex-

tension. In the differential diagnosis of

renal mass lesions, the findings of the acute

renal carbuncle noted at arteriography are

characteristic, in which one encounters the

absence of mass displacement despite previ-

ous features of a mass. The presence of

either renal cell or renal pelvic carcinoma is

also easily excluded in this phase, since

these neoplasias are associated with a spe-

cific neovascularity.7 In some pelvic tu-

mors, particularly of the squamous variety,

diffuse interstitial spread may be the only

manifestation of the disease, and differen-

tiation from an acute carbuncle may be

difficult. However, the acute renal car-

VOL. ii6, No. � Acute Renal Carbuncle 747

buncle rarely invades the collecting sys.-

tems directly. The distinction of neoplasmfrom chronic renal carbuncle, however, may

be difficult since the latter has a highly de-veloped abscess wall with neovascularity.Renal vein thrombosis is easily distin-

guished from the diffuse acute carbuncle

when either the collateral venous circula-

tion or the thrombus is demonstrated.

DISCUSSION

From the above findings and an analysisof the patients and their presentation(Table i), a few interesting clinical and

pathologic Suggestions are noted. These,however, require further confirmation. In 2

of the 6 cases, the process was overwhelm-

ing and involved the entire kidney. Both

these patients were males, above 50 yearsof age, and had prostatic disease, car-cinoma in one patient, and benign hyper-

trophy in the other. The renal infection

evolved as an ascending infection in whichthe causative agents were gram negative in

origin.The remaining 4 renal infections were of

hematogenous origin. Interestingly enough,

three were females, all in their twenties, and

all suffering from drug addiction. The re-maining patient was a young male withfurunculosis. In contrast to the diffuse renal

involvement associated with the ascendinginfections encountered in the elderly males,

the renal carbuncles of hematogenousorigin were all localized in nature. It istherefore conceivable that a definite patho-

logic pattern of the acute renal carbunclemay be present.

As far as the over-all roentgenographic

features of renal infection are concerned,most have been confined to the diagnosis of

acute pyelonephritis with changes limited

to blunting of the calyces and dilatation ofthe ureter. Although the latter has re-

ceived a great deal of stress in the litera-

ture, the features of acute carbuncle are farmore impressive and just as vital. Failureto make a prompt diagnosis can result in

loss of either the kidney or the patient.

Moreover, the clinical picture may be ob-

scured when the patient is partially treatedwith antibiotics. This stimulates the car-

buncle to further coalesce, wall off, and

proceed into the subacute or chronic phase.

Inadequate therapy may also allow further

perforation of the infection with involve-ment of surrounding neighboring struc-

tures. Consequently, early institution oftherapy, either medical or surgical, is im-

perative and will often salvage the kidney.

The radiologist should now be alerted to

this diagnosis, if and when the clinical statussuggests an underlying infective process

and the roentgen findings are as described

above.

SUMMARY

The roentgenographic findings of acuterenal carbuncle observed in 6 patients are

described. Basically, these findings con-sisted of:

i. Interstitial disease associated with

perirenal involvement demonstrated onpreliminary studies;

2. No mass displacement of the vessels

in the involved area on angiography despite

the suggestion of a mass on the earlier ex-

aminations;

3. Loss of the cortico-medullary junctionon the nephrogram.

The early diagnosis of acute carbuncle is

essential since prompt therapy may salvage

the kidney. With the ever increasing prob-lem of drug addiction and its associated

complications, acute renal carbuncle is

slowly becoming a common disease of

youth.

Jack G. Rabinowitz, M.D.Department of RadiologyState University of New YorkDownstate Medical Center& Kings County Hospital Center450 Clarkson AvenueBrooklyn, New York 11203

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