- Email: [email protected]
Xanthogranulomatous pyelonephritis: Clinical findings and surgical considerations
ADULT
UROLOGY
XANTHOGRANULOMATOUS PYELONEPHRITIS: CLINICAL FINDINGS AND SURGICAL CONSIDERATIONS JAMES EASTHAM, M.D. THOMAS AHLERING, M.D. EILA SKINNER, M.D. From the Department of Urology, University of Southern California, Los Angeles, California
ABSTRACT-Objective. Xanthogranulomatous pyelonephritis (XGP) is an uncommon but well-characterized inflammatory process of the kidney. Few reports, however, have correlated preoperative radiographic features with findings at surgical exploration. We report our experience in the surgical management of XGP with emphasis on the use of computed tomography (CT) in the preoperative evaluation. Methods. We retrospectively reviewed all medical records including radiographic materials of 27 patients with a pathologic diagnosis of XGP. In particular, preoperative CT features were analyzed to see if they correlated with surgical findings. Results. A CT scan was performed in 23 of the 27 patients. Of these 23 patients 20 (87%) were diagnosed with XGP based on the CT findings. CT accurately defined the extent of the perinephric inflammatory reaction, identifying 8 patients with muscular extension, 3 with splenic involvement, 1 with extension into the colon, and 5 with encasement of the great vessels. In no case did CT underestimate the involvement of adjacent tissues. Conclusions. Although XGP is a rare disease, a careful preoperative evaluation can suggest its diagnosis. CT is particularly valuable in that it not only demonstrates characteristic renal findings, but also shows the extent of inflammation and extent into adjacent tissues. This will aid in surgical planning in choosing an approach that will provide adequate exposure and facilitate patient care.
Xanthogranulomatous pyelonephritis (XGP) is a chronic bacterial infection of the kidney resulting in the normal renal parenchyma being replaced by characteristic foamy histiocytes. Although XGP is uncommon, numerous reports describing the clinical presentation, radiologic features, and pathologic findings exist.lm5 Few reports, however, have correlated preoperative radiographic features with findings at surgical exploration. We report our experience in the surgical management of XGP MATERIAL AND METHODS An examination of all nephrectomy specimens at the Los Angeles County-University of Southern California Medical Center from 1984 to 1992 disSubmitted- Sfpffmher
IJROLOG’r
I h, 1993,accepted:
/ MAKC H
October-
1.5,199.3
1994 / Vo[uMr4.1.NINI~K 3
closed 27 patients with a pathologi’c diagnosis of XGP All medical records including, radiographic materials were reviewed with respect to clinical presentation, laboratory and radiologic features, and findings at surgical exploration. In particular, preoperative CT features were analyzed to see if they correlated with surgical findings. RESULTS A total of 27 patients with XGP have been treated over the past eight years. There were 25 females and 2 males, with an average age of fortyfive years (range 26-63 years). All cases were unilateral with the left kidney involved in 19 and the right kidney in 8. Approximately one third of the patients (8) were diabetic. The clinical symptoms and signs are presented in Table 1. The most frequent complaints were
295
TABLE I.
TABLE
Symptoms/signs at presentation in 2 7 XCP patients
Flank/abdominal paln Palpable mass Fever Recurrent urinary infectlon Weight loss!anorexlaimalalse Drarnlng flank sinus Empyemaipneumonla
No.
(o/o1
24 13 12 13 9 2 2
(891 1481 (441 1481 (33) 171 (71
abdominal/flank pain (89%), fever (44%), and anorexia/malaise (33%). A palpable mass was present in 48 percent. A history of recurrent urinary tract infections was also common (48%). Two patients (7%) presented with a draining flank sinus: 1 had had intermittent drainage over a ten-year period following a pyelolithotomy; the other had a six-month history of persistent purulent drainage after percutaneous nephrolithotomy. Both were found to have a pyelocutaneous fistula at surgical exploration. Abnormal laboratory findings were common in our group of patients (Table II). Anemia (hemoglobin less than 12 g/dL) was present in 22 (81%) of the patients, while 15 (56%) had a leukocytosis (white blood cells greater than 10,000/mm3). An elevated alkaline phosphatase or hypoalbuminemia, suggestive of hepatic dysfunction was present in 21 (78%) and 19 (70%), respectively Eight patients had repeat alkaline phosphatase determinations, with 6 patients having normal levels at three months following nephrectomy. Four patients had urinary cytology examinations. None was found to have malignant or foam cells. All patients had preoperative urine and intraoperative cultures (Table III). Of 27 patients, 6 (22%) were found to have sterile preoperative cultures. Proteus mirabilis was the most frequent organism and was found in 15 of 21 (71%) positive cultures. Escherichia coli was found in 5 of 21 (24%) while 2 of 21 (9%) had anaerobic (Bacteroides) infection. Seven of 21 (26%) had mixed infections. Radiologic evaluation usually began with either an intravenous urogram (IVU) or an abdominal ultrasound. Thirteen of the 27 patients had an IVU as their initial study. Typical findings included an enlarged renal shadow and nonfunction. Twelve of Fhe 13 patients who had an IVU had an associated renal pelvis stone, all > 2 cm in largest dimension. The remaining patient had no stone. All 13 patients had a normal-appearing contralateral kidney. 296
II.
Abnormal laboratory in 2 7 XCP patients
Azotemla [creatinine > 1 3 mg/dL] Anemia [hemoglobin < 12 g/dL) Leukocytosls (white blood count > 10,OOO/mms) Elevated alkaline phosphatase (> IlOUiL] Hypoalbumlnemla [albumrn < 3 2 mg/dL) Urine “foam cells” on cytology (N = 4)
TABLE
findings No.
(OhI
8 22
(301 (81)
15
1561
21
I781
19 0
(701 0)
Bacteriology in 2 1 positive III. cultures7 with mixed infections
urine
Organism
No.
I”/01
P mlrabllrs E. co11 K. pneumoniae Bacteroldes species Enterococcus Pseudomonas Citrobacter Serratia
15 5 2 2 2 1 1 1
(711 124)
(91 (9)
191 (5) (5) (51
Abdominal ultrasound was the first radiologic study in 12 of 27 patients. All had hydronephrosis and a renal pelvis stone. There was increased echogenicity of the fluid within the hydronephrotic spaces, consistent with pyonephrosis. Two patients had studies other than an IVU or ultrasound as their first radiologic investigation. One, with a chronically draining fistula, had a retrograde urogram that documented a pyelocutaneous fistula. A renal scan showed no function of the involved renal unit, and the patient underwent successful nephrectomy. The other patient presented with a palpable abdominal mass and underwent a CT scan which demonstrated features consistent with XGP (discussed later). A CT scan was performed in 23 of the 27 patients (including 1 patient who had a CT scan as her only imaging study). Twenty of these 23 (87%) patients were considered to have a diagnosis of XGP based on the CT scan findings. The typical CT scan characteristics of XGP include an enlarged kidney, a calculus in a contracted renal pelvis, low-density ovoid areas consistent with a hydronephrotic pattern, and a rim of tissue surrounding these hydronephrotic areas that strongly enhances with intravenous contrast media but does not excrete the dye even on delayed films (Fig. 1).
UROLOGY
/
bfAR(
!I
19Y4
/
L’oI.I:v~
43. NI’MMR .J
FIGURE 1. [A) Abdominal CT scan without intravenous contrast media demonstrates low-density ovoid areas with a hydronephrotic pattern. A large perinephric abscess is also demonstrated. [B) After the injection of intravenous contrast media, the rim of tissue that surrounds the spaces enhances, but does not excrete contrast.
In addition to suggesting the diagnosis, CT also accurately defined the extent of the perinephric inflammatory reaction. Eight patients had extension into the quadratus lumborum and/or psoas muscle. Three had extension into the spleen, 1 into thle descending colon, and 5 had encasement of the great vessels. All of these findings were confirmed at surgical exploration. In no case did CT underestimate the involvement of adjacent tissues. As previously mentioned, 21 of the 27 patients had a preoperative elevation of the alkaline phosphatase, suggestive of hepatic dysfunction. Nineteen of these 21 patients had a CT scan while the remaining 2 had an abdominal ultrasound. In all 21 cases, the liver and biliary system was believed to be normal from a radiologic standpoint. Three of the 23 patients (13%) who had a CT scan did not have a diagnosis of XGP preoperatively. All 3 were considered to have a poorly functioning kidney with an associated obstructing renal stone. None of these 3 had extension of the inflammatory process outside the kidney either by CT scan or surgically. Five of our patients underwent magnetic resonance imaging (MRI). All also had had a CT scan. MRI adequately demonstrated the extent of the inflammatory process and correlated well with the surgical findings. However, MRI added no new information that was not already known from the prior CT scan. Overall, 20 of the 27 patients (74%) had a preoperative diagnosis of XGP based on CT scan. All 20 had a CT scan. All 20 were approached via a thoracoabdominal incision with transperitoneal control of the renal vessels prior to mobilizing the kidney. This approach provided excellent expo-
sure and facilitated the dissection when the inflammatory process involved adjacent structures. Three patients had simultaneous splencctomy and 1 had partial colectomy. All patients had chest tubes placed intraoperatively which were removed on the second or third postoperative day. There were no complications related to entering the thorax, even in the presence of gross pus. Seven of the 27 patients (26O/o) did not have a preoperative diagnosis of XGP Threle of these 7 had had a CT scan. All 7 were considered to have a poorly functioning kidney with an associated renal stone. All 7 were approached via the flank position. Three were believed to be candidates for an anatropic nephrolithotomy, but because of the findings at surgery a nephrectomy was performed. Review of the operative reports outlined the difficulty of the procedure especially in ,gaining control of the renal vessels. This was attr-lbuted to the extent of inflammation and the poor exposure provided by this approach. Pathologic examination of all specimens revealed an enlarged kidney with markedly dilated calices. The collecting system was filled with pus. This corresponded to the pyonephrosis demonstrated by ultrasonography and the dilated, lowdensity ovoid areas seen on CT scan Microscopically, there was diffuse infiltration of the kidney by an inflammatory reaction consisting of foamy histiocytes admixed with neutrophils, lymphocytes, and plasma cells. None of our cases revealed only focal involvement of the kidnev. COMMENT Xanthogranulomatous pyelonephritis is an uncommon but well-characterized chronic 297
inflammatory process of the kidney, Although the etiology of XGP is unknown, it clearly is related to a combination of renal obstruction and chronic bacterial infection. Povysil and Konickova” were able to induce XGP in rats by ligating the ureter and injecting a low virulence strain of E. coli. Most large series, including our own, have found XGP in association with either a renal stone or congenital obstruction.‘-4 In the largest series to date, Parsons and associates3 found that 86 of 87 patients had obstruction of the involved kidney. The clinical features of our group of patients is typical of those reported elsewhere. XGP commonly occurs in middle-aged women, although cases have been seen in children and the elderly.2-7 Fever, flank pain, a palpable flank mass, and malaise with weight loss were common in our patients, and have been described in up to two thirds of patients.8 Although 8 of our 27 patients were diabetic, there does not seem to be a predisposition for XGP among diabetics.‘,3 Prior to the advent of the CT scan, the radiologic diagnosis of XGP was difficult. With CT, however, the diagnosis can usually be made preoperatively. Indeed, 20 of our 23 patients (87%) who had CT scans were correctly diagnosed as having XGI? Our findings on CT scan are similar to those noted by other authors.5,y,‘0 Claes et al.” consider the CT characteristics of XGP to include a large calculus in the renal collecting system, absence of excretion of contrast medium, spherical areas arranged in a hydronephrotic pattern, with higher attenuation than urine and no enhancement, large lesions with ill-defined borders and extension beyond the expected confines of the kidney, preservation of the reniform outline, and enhancing rims surrounding the spherical lowdensity areas. We consider this last finding, enhancement of the cortical tissue surrounding hydronephrotic spaces, to be most characteristic (Fig. 1). This appears to result from replacement of the normal renal cortex by inflammatory tissue and is similar to the appearance of an abscess wall. In addition to the characteristic renal findings of XGP, CT is quite accurate in assessing the extent of the adjacent inflammatory reaction. CT findings in 8 of our patients suggested extension into the back muscles, 3 with splenic involvement, 1 with descending colon involvement, and 5 with encasement of the great vessels. All of these CT findings were confirmed at surgical exploration. In addition, review of preoperative CT scans and operative reports suggests that CT did not underestimate the extent of the inflammatory reaction,
The information provided by CT, not only the renal but also the perirenal involvement, is valuable in planning surgery. All of our patients with a preoperative diagnosis of XGP were approached via a thoracoabdominal incision. We believe that the anterior exposure provided by this route is critical in performing a safe and complete dissection especially in the presence of a large inflammatory renal mass with involvement of adjacent structures. One concern with entry into the thorax is the risk of empyema. None of our 20 patients had this complication. We consider the exposure gained by this surgical approach to far outweigh the apparent low risk of empyema. All of our patients had diffuse involvement of the kidney with XGP Several authors, however, have described a variant of XGP with only focal involvement of the kidney2,‘,” A preoperative diagnosis of XGP was rarely made, with most of these cases defined pathologically after partial or total nephrectomy for stone disease, chronic infection, or in one rare case of transitional cell carcinoma of the renal pelvis. This suggests that in some cases, the xanthogranulomatous process may start as a localized involvement of the kidney. If identified at this stage, successful treatment with partial nephrectomy could be performed thus preserving renal parenchyma. In summary, although XGP is a rare disease, a careful preoperative evaluation can suggest its diagnosis. In particular, the presence of an enlarged, hydronephrotic kidney with a renal stone on IVU or ultrasound is a common finding. A subsequent CT scan should be obtained because it not only demonstrates the characteristic renal findings, but also shows the extent of inflammation and extent into adjacent structures. This will guide surgical planning in choosing an approach that will provide adequate exposure and facilitate patient care. James A. Eastham, M.D. Baylor College ofMedicine Department of Urology 6560 Fannin, Suite 1035 Houston, Texas 770.30 REFERENCES 1. Goodman M, Curry T, and Russell T: Xanthogranulomatous pyelonephritis (XGP): a local disease with systemic manifestations. Medicine 58: 171-181, 1979. 2. Chuang CK, Lai MK. Chang PL, Huang MH, Chu SH, Wu CJ, and Wu HR: Xanthogranulomatous pyelonephritis: experience in 36 cases. J Ural 147: 333-336, 1992. 3. Parsons MA, Harris SC. Longstaff AJ, and Grainger RG: Xanthogranulomatous pyelonephritis: a pathological. clinical and aetiological analysis of 87 cases. Diag Histopath 6: 203219, 1983.
-J TO~I.I EM, Iloreta A. Freed SZ, Fruchtman R. Bennett 13, and Newman 1111- ~anthogranulomatous p>,elonephritis: dctailed analvsi\ 01 29 cahes and a brief description of atypical prcscnratlons 1 Ural 126: 437-442, 1981. 5. Solomon A. Rral %. Pap” J. and Merlmsky C. Computerlzctl tcm1ography In ~anthogranulornat~~~l~ lq elonephritls. J I rol 130: 323-?825. 1983 I_: Experimental santhogran6. Povy\il ( _.~ndKonickova ulomatou5 pycloncphritis. Invest Urol 9: 3 I 3-3 18. 1972. 7. Yaz.Al T. I\hika\hza S. Ogawa Y, Takahashi 5. Ncmoto S, R~n&o h. K,lnoh S, and Kitagawa R: XanthogranLllomatoLla p>,elonephrlti\ 111 childhood: casr report and rcvicw of Eng] Ilrol 127: W-83, 1982. lish and lapanesc Ilttraturc.
8. Eldrr IS: Xanthogranulomatous pyelonephrltis and gas forming lnlection~ of the urinary tract All.\ L:pdatc Series 3. WI 31, 1984. 9. Claes 11. Vcrccckcn R, Oycn R. and ban Dammc 8: Nanthogranulomatous pyelonephrltis with emphasis on computcrized tomography scan. Urology 29: 389-W. 1987. IO. Goldman SM, Hartman DS, Fishmdn Ek. Fimzm JP, Latewood OM, and Siegelman SS: (‘1. of ~anthogranulomatous pyelonephritis: radiologic-pathologic corrclatmn Am J Rocntgenol 141: 963-969. 1984. I I. Malck RS, and Elder JS >;anttiogranLllomatous pyclonephritis: a critical analysis of 26 ca\cs and the litcra1978. turc. J Ural 119. 589-593.
299
UROLOGY
XANTHOGRANULOMATOUS PYELONEPHRITIS: CLINICAL FINDINGS AND SURGICAL CONSIDERATIONS JAMES EASTHAM, M.D. THOMAS AHLERING, M.D. EILA SKINNER, M.D. From the Department of Urology, University of Southern California, Los Angeles, California
ABSTRACT-Objective. Xanthogranulomatous pyelonephritis (XGP) is an uncommon but well-characterized inflammatory process of the kidney. Few reports, however, have correlated preoperative radiographic features with findings at surgical exploration. We report our experience in the surgical management of XGP with emphasis on the use of computed tomography (CT) in the preoperative evaluation. Methods. We retrospectively reviewed all medical records including radiographic materials of 27 patients with a pathologic diagnosis of XGP. In particular, preoperative CT features were analyzed to see if they correlated with surgical findings. Results. A CT scan was performed in 23 of the 27 patients. Of these 23 patients 20 (87%) were diagnosed with XGP based on the CT findings. CT accurately defined the extent of the perinephric inflammatory reaction, identifying 8 patients with muscular extension, 3 with splenic involvement, 1 with extension into the colon, and 5 with encasement of the great vessels. In no case did CT underestimate the involvement of adjacent tissues. Conclusions. Although XGP is a rare disease, a careful preoperative evaluation can suggest its diagnosis. CT is particularly valuable in that it not only demonstrates characteristic renal findings, but also shows the extent of inflammation and extent into adjacent tissues. This will aid in surgical planning in choosing an approach that will provide adequate exposure and facilitate patient care.
Xanthogranulomatous pyelonephritis (XGP) is a chronic bacterial infection of the kidney resulting in the normal renal parenchyma being replaced by characteristic foamy histiocytes. Although XGP is uncommon, numerous reports describing the clinical presentation, radiologic features, and pathologic findings exist.lm5 Few reports, however, have correlated preoperative radiographic features with findings at surgical exploration. We report our experience in the surgical management of XGP MATERIAL AND METHODS An examination of all nephrectomy specimens at the Los Angeles County-University of Southern California Medical Center from 1984 to 1992 disSubmitted- Sfpffmher
IJROLOG’r
I h, 1993,accepted:
/ MAKC H
October-
1.5,199.3
1994 / Vo[uMr4.1.NINI~K 3
closed 27 patients with a pathologi’c diagnosis of XGP All medical records including, radiographic materials were reviewed with respect to clinical presentation, laboratory and radiologic features, and findings at surgical exploration. In particular, preoperative CT features were analyzed to see if they correlated with surgical findings. RESULTS A total of 27 patients with XGP have been treated over the past eight years. There were 25 females and 2 males, with an average age of fortyfive years (range 26-63 years). All cases were unilateral with the left kidney involved in 19 and the right kidney in 8. Approximately one third of the patients (8) were diabetic. The clinical symptoms and signs are presented in Table 1. The most frequent complaints were
295
TABLE I.
TABLE
Symptoms/signs at presentation in 2 7 XCP patients
Flank/abdominal paln Palpable mass Fever Recurrent urinary infectlon Weight loss!anorexlaimalalse Drarnlng flank sinus Empyemaipneumonla
No.
(o/o1
24 13 12 13 9 2 2
(891 1481 (441 1481 (33) 171 (71
abdominal/flank pain (89%), fever (44%), and anorexia/malaise (33%). A palpable mass was present in 48 percent. A history of recurrent urinary tract infections was also common (48%). Two patients (7%) presented with a draining flank sinus: 1 had had intermittent drainage over a ten-year period following a pyelolithotomy; the other had a six-month history of persistent purulent drainage after percutaneous nephrolithotomy. Both were found to have a pyelocutaneous fistula at surgical exploration. Abnormal laboratory findings were common in our group of patients (Table II). Anemia (hemoglobin less than 12 g/dL) was present in 22 (81%) of the patients, while 15 (56%) had a leukocytosis (white blood cells greater than 10,000/mm3). An elevated alkaline phosphatase or hypoalbuminemia, suggestive of hepatic dysfunction was present in 21 (78%) and 19 (70%), respectively Eight patients had repeat alkaline phosphatase determinations, with 6 patients having normal levels at three months following nephrectomy. Four patients had urinary cytology examinations. None was found to have malignant or foam cells. All patients had preoperative urine and intraoperative cultures (Table III). Of 27 patients, 6 (22%) were found to have sterile preoperative cultures. Proteus mirabilis was the most frequent organism and was found in 15 of 21 (71%) positive cultures. Escherichia coli was found in 5 of 21 (24%) while 2 of 21 (9%) had anaerobic (Bacteroides) infection. Seven of 21 (26%) had mixed infections. Radiologic evaluation usually began with either an intravenous urogram (IVU) or an abdominal ultrasound. Thirteen of the 27 patients had an IVU as their initial study. Typical findings included an enlarged renal shadow and nonfunction. Twelve of Fhe 13 patients who had an IVU had an associated renal pelvis stone, all > 2 cm in largest dimension. The remaining patient had no stone. All 13 patients had a normal-appearing contralateral kidney. 296
II.
Abnormal laboratory in 2 7 XCP patients
Azotemla [creatinine > 1 3 mg/dL] Anemia [hemoglobin < 12 g/dL) Leukocytosls (white blood count > 10,OOO/mms) Elevated alkaline phosphatase (> IlOUiL] Hypoalbumlnemla [albumrn < 3 2 mg/dL) Urine “foam cells” on cytology (N = 4)
TABLE
findings No.
(OhI
8 22
(301 (81)
15
1561
21
I781
19 0
(701 0)
Bacteriology in 2 1 positive III. cultures7 with mixed infections
urine
Organism
No.
I”/01
P mlrabllrs E. co11 K. pneumoniae Bacteroldes species Enterococcus Pseudomonas Citrobacter Serratia
15 5 2 2 2 1 1 1
(711 124)
(91 (9)
191 (5) (5) (51
Abdominal ultrasound was the first radiologic study in 12 of 27 patients. All had hydronephrosis and a renal pelvis stone. There was increased echogenicity of the fluid within the hydronephrotic spaces, consistent with pyonephrosis. Two patients had studies other than an IVU or ultrasound as their first radiologic investigation. One, with a chronically draining fistula, had a retrograde urogram that documented a pyelocutaneous fistula. A renal scan showed no function of the involved renal unit, and the patient underwent successful nephrectomy. The other patient presented with a palpable abdominal mass and underwent a CT scan which demonstrated features consistent with XGP (discussed later). A CT scan was performed in 23 of the 27 patients (including 1 patient who had a CT scan as her only imaging study). Twenty of these 23 (87%) patients were considered to have a diagnosis of XGP based on the CT scan findings. The typical CT scan characteristics of XGP include an enlarged kidney, a calculus in a contracted renal pelvis, low-density ovoid areas consistent with a hydronephrotic pattern, and a rim of tissue surrounding these hydronephrotic areas that strongly enhances with intravenous contrast media but does not excrete the dye even on delayed films (Fig. 1).
UROLOGY
/
bfAR(
!I
19Y4
/
L’oI.I:v~
43. NI’MMR .J
FIGURE 1. [A) Abdominal CT scan without intravenous contrast media demonstrates low-density ovoid areas with a hydronephrotic pattern. A large perinephric abscess is also demonstrated. [B) After the injection of intravenous contrast media, the rim of tissue that surrounds the spaces enhances, but does not excrete contrast.
In addition to suggesting the diagnosis, CT also accurately defined the extent of the perinephric inflammatory reaction. Eight patients had extension into the quadratus lumborum and/or psoas muscle. Three had extension into the spleen, 1 into thle descending colon, and 5 had encasement of the great vessels. All of these findings were confirmed at surgical exploration. In no case did CT underestimate the involvement of adjacent tissues. As previously mentioned, 21 of the 27 patients had a preoperative elevation of the alkaline phosphatase, suggestive of hepatic dysfunction. Nineteen of these 21 patients had a CT scan while the remaining 2 had an abdominal ultrasound. In all 21 cases, the liver and biliary system was believed to be normal from a radiologic standpoint. Three of the 23 patients (13%) who had a CT scan did not have a diagnosis of XGP preoperatively. All 3 were considered to have a poorly functioning kidney with an associated obstructing renal stone. None of these 3 had extension of the inflammatory process outside the kidney either by CT scan or surgically. Five of our patients underwent magnetic resonance imaging (MRI). All also had had a CT scan. MRI adequately demonstrated the extent of the inflammatory process and correlated well with the surgical findings. However, MRI added no new information that was not already known from the prior CT scan. Overall, 20 of the 27 patients (74%) had a preoperative diagnosis of XGP based on CT scan. All 20 had a CT scan. All 20 were approached via a thoracoabdominal incision with transperitoneal control of the renal vessels prior to mobilizing the kidney. This approach provided excellent expo-
sure and facilitated the dissection when the inflammatory process involved adjacent structures. Three patients had simultaneous splencctomy and 1 had partial colectomy. All patients had chest tubes placed intraoperatively which were removed on the second or third postoperative day. There were no complications related to entering the thorax, even in the presence of gross pus. Seven of the 27 patients (26O/o) did not have a preoperative diagnosis of XGP Threle of these 7 had had a CT scan. All 7 were considered to have a poorly functioning kidney with an associated renal stone. All 7 were approached via the flank position. Three were believed to be candidates for an anatropic nephrolithotomy, but because of the findings at surgery a nephrectomy was performed. Review of the operative reports outlined the difficulty of the procedure especially in ,gaining control of the renal vessels. This was attr-lbuted to the extent of inflammation and the poor exposure provided by this approach. Pathologic examination of all specimens revealed an enlarged kidney with markedly dilated calices. The collecting system was filled with pus. This corresponded to the pyonephrosis demonstrated by ultrasonography and the dilated, lowdensity ovoid areas seen on CT scan Microscopically, there was diffuse infiltration of the kidney by an inflammatory reaction consisting of foamy histiocytes admixed with neutrophils, lymphocytes, and plasma cells. None of our cases revealed only focal involvement of the kidnev. COMMENT Xanthogranulomatous pyelonephritis is an uncommon but well-characterized chronic 297
inflammatory process of the kidney, Although the etiology of XGP is unknown, it clearly is related to a combination of renal obstruction and chronic bacterial infection. Povysil and Konickova” were able to induce XGP in rats by ligating the ureter and injecting a low virulence strain of E. coli. Most large series, including our own, have found XGP in association with either a renal stone or congenital obstruction.‘-4 In the largest series to date, Parsons and associates3 found that 86 of 87 patients had obstruction of the involved kidney. The clinical features of our group of patients is typical of those reported elsewhere. XGP commonly occurs in middle-aged women, although cases have been seen in children and the elderly.2-7 Fever, flank pain, a palpable flank mass, and malaise with weight loss were common in our patients, and have been described in up to two thirds of patients.8 Although 8 of our 27 patients were diabetic, there does not seem to be a predisposition for XGP among diabetics.‘,3 Prior to the advent of the CT scan, the radiologic diagnosis of XGP was difficult. With CT, however, the diagnosis can usually be made preoperatively. Indeed, 20 of our 23 patients (87%) who had CT scans were correctly diagnosed as having XGI? Our findings on CT scan are similar to those noted by other authors.5,y,‘0 Claes et al.” consider the CT characteristics of XGP to include a large calculus in the renal collecting system, absence of excretion of contrast medium, spherical areas arranged in a hydronephrotic pattern, with higher attenuation than urine and no enhancement, large lesions with ill-defined borders and extension beyond the expected confines of the kidney, preservation of the reniform outline, and enhancing rims surrounding the spherical lowdensity areas. We consider this last finding, enhancement of the cortical tissue surrounding hydronephrotic spaces, to be most characteristic (Fig. 1). This appears to result from replacement of the normal renal cortex by inflammatory tissue and is similar to the appearance of an abscess wall. In addition to the characteristic renal findings of XGP, CT is quite accurate in assessing the extent of the adjacent inflammatory reaction. CT findings in 8 of our patients suggested extension into the back muscles, 3 with splenic involvement, 1 with descending colon involvement, and 5 with encasement of the great vessels. All of these CT findings were confirmed at surgical exploration. In addition, review of preoperative CT scans and operative reports suggests that CT did not underestimate the extent of the inflammatory reaction,
The information provided by CT, not only the renal but also the perirenal involvement, is valuable in planning surgery. All of our patients with a preoperative diagnosis of XGP were approached via a thoracoabdominal incision. We believe that the anterior exposure provided by this route is critical in performing a safe and complete dissection especially in the presence of a large inflammatory renal mass with involvement of adjacent structures. One concern with entry into the thorax is the risk of empyema. None of our 20 patients had this complication. We consider the exposure gained by this surgical approach to far outweigh the apparent low risk of empyema. All of our patients had diffuse involvement of the kidney with XGP Several authors, however, have described a variant of XGP with only focal involvement of the kidney2,‘,” A preoperative diagnosis of XGP was rarely made, with most of these cases defined pathologically after partial or total nephrectomy for stone disease, chronic infection, or in one rare case of transitional cell carcinoma of the renal pelvis. This suggests that in some cases, the xanthogranulomatous process may start as a localized involvement of the kidney. If identified at this stage, successful treatment with partial nephrectomy could be performed thus preserving renal parenchyma. In summary, although XGP is a rare disease, a careful preoperative evaluation can suggest its diagnosis. In particular, the presence of an enlarged, hydronephrotic kidney with a renal stone on IVU or ultrasound is a common finding. A subsequent CT scan should be obtained because it not only demonstrates the characteristic renal findings, but also shows the extent of inflammation and extent into adjacent structures. This will guide surgical planning in choosing an approach that will provide adequate exposure and facilitate patient care. James A. Eastham, M.D. Baylor College ofMedicine Department of Urology 6560 Fannin, Suite 1035 Houston, Texas 770.30 REFERENCES 1. Goodman M, Curry T, and Russell T: Xanthogranulomatous pyelonephritis (XGP): a local disease with systemic manifestations. Medicine 58: 171-181, 1979. 2. Chuang CK, Lai MK. Chang PL, Huang MH, Chu SH, Wu CJ, and Wu HR: Xanthogranulomatous pyelonephritis: experience in 36 cases. J Ural 147: 333-336, 1992. 3. Parsons MA, Harris SC. Longstaff AJ, and Grainger RG: Xanthogranulomatous pyelonephritis: a pathological. clinical and aetiological analysis of 87 cases. Diag Histopath 6: 203219, 1983.
-J TO~I.I EM, Iloreta A. Freed SZ, Fruchtman R. Bennett 13, and Newman 1111- ~anthogranulomatous p>,elonephritis: dctailed analvsi\ 01 29 cahes and a brief description of atypical prcscnratlons 1 Ural 126: 437-442, 1981. 5. Solomon A. Rral %. Pap” J. and Merlmsky C. Computerlzctl tcm1ography In ~anthogranulornat~~~l~ lq elonephritls. J I rol 130: 323-?825. 1983 I_: Experimental santhogran6. Povy\il ( _.~ndKonickova ulomatou5 pycloncphritis. Invest Urol 9: 3 I 3-3 18. 1972. 7. Yaz.Al T. I\hika\hza S. Ogawa Y, Takahashi 5. Ncmoto S, R~n&o h. K,lnoh S, and Kitagawa R: XanthogranLllomatoLla p>,elonephrlti\ 111 childhood: casr report and rcvicw of Eng] Ilrol 127: W-83, 1982. lish and lapanesc Ilttraturc.
8. Eldrr IS: Xanthogranulomatous pyelonephrltis and gas forming lnlection~ of the urinary tract All.\ L:pdatc Series 3. WI 31, 1984. 9. Claes 11. Vcrccckcn R, Oycn R. and ban Dammc 8: Nanthogranulomatous pyelonephrltis with emphasis on computcrized tomography scan. Urology 29: 389-W. 1987. IO. Goldman SM, Hartman DS, Fishmdn Ek. Fimzm JP, Latewood OM, and Siegelman SS: (‘1. of ~anthogranulomatous pyelonephritis: radiologic-pathologic corrclatmn Am J Rocntgenol 141: 963-969. 1984. I I. Malck RS, and Elder JS >;anttiogranLllomatous pyclonephritis: a critical analysis of 26 ca\cs and the litcra1978. turc. J Ural 119. 589-593.
299