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Perinephric Abscess: Current Concepts
0022-534 7/87 /1372-0191$02.00/0 Vol. 137, February Printed in U.S.A.
THE JOURNAL OF UROLOGY
Copyright© 1987 by The Williams & Wilkins Co.
Review Article PERINEPHRIC ABSCESS: CURRENT CONCEPTS JOEL SHEINFELD,* ERDAL ERTURK, ROBERT F. SPATARO
AND
ABRAHAM T. K. COCKETT
From the Departments of Urology and Radiology, School of Medicine and Dentistry, University of Rochester, Rochester, New York
Despite dramatic technical advances in the various fields of diagnostic radiology and the advent of sophisticated antimicrobial therapy, the prompt and accurate recognition of a perinephric abscess continues to elude even the most experienced urologist. Its onset and course are insidious, and its symptomatology is highly variable. Unrecognized and untreated, perinephric abscesses result in considerable morbidity and mortality. We present our recent experience with 15 patients with perinephric abscess and review the literature. Particular emphasis is placed on the pathogenesis, predisposing factors, clinical presentation, complications and bacteriology of perinephric abscesses. Pertinent radiological abnormalities on chest and abdominal x-rays, excretory urograms (IVPs), ultrasonograms and computerized tomography (CT) scans are discussed. Our experience indicates that CT is the diagnostic modality of choice. Effective treatment requires appropriate antibiotic coverage and drainage of the abscess. Newer percutaneous techniques have spared several patients from a major operation and have provided a viable alternative for patients who are poor surgical risks. The diagnosis of a perinephric abscess notoriously is difficult to make. 1 The condition frequently mimics intra-abdominal, neurological, orthopedic or lower urinary tract disease. 2 Untreated, a perinephric abscess almost invariably will result in death. Perinephric abscess is a rare entity, with the reported incidence ranging from 0.9 to 4.0 cases per 10,000 hospital admissions and comprising 0.2 per cent of all urological procedures. The right side is involved slightly more often than the left side, while the disease is bilateral in 2 per cent of the patients. 1
neously draining abscess. Downward extension between the anterior and posterior layers of Gerota's fascia may produce an abscess in the groin or paravesical area. The abscess may extend medially and penetrate into the peritoneum or laterally and perforate the colon. Finally, the process may extend superiorly as a subphrenic abscess or penetrate the diaphragm, resulting in empyema, lung abscess or perinephrobronchial fistula. 5 ETIOLOGY
Campbell classified a perinephric abscess according to its renal or extrarenal origin. 2 Currently, the majority ofperinephric abscesses can be attributed to renal causes, including rupture into the perinephric space of an intrarenal abscess, renal cortical abscess or pyonephrosis, as well as chronic or recurrent pyelonephritis (particularly in the presence of obstruction), xanthogranulomatous pyelonephritis and renal carbuncle. 1 • 6- 9 Before the advent of antibiotics, hematogenous seeding from a distant pyogenic focus accounted for 80 per cent of perinephric abscesses and the causative organism almost invariably was Staphylococcus aureus. 9 The retroperitoneal lymphatic channels provide a second avenue for the arrival of bacteria, and infection has been reported to ascend via the lymphatics from the bladder, seminal vesicles, prostate, fallopian tubes, or perirectal or other pelvic tissues. 2 Contiguous structures provide a third source for the extrarenal origin of a perinephric abscess. Inflammatory lesions of the liver, gallbladder, pancreas and high retrocecal appendix, as well as Crohn's disease and osteomyelitis of the ribs and vertebrae all have been implicated.
ANATOMICAL CONSIDERATIONS MICROBIOLOGY
A perinephric abscess is an accumulation of pus in the perinephric space, that is the space between the renal capsule and Gerota's fascia. 3 The perinephric fat surrounds both kidneys and adrenal glands, and is enclosed by Gerota's fascia, which is comprised of a thin anterior layer also known as the fascia of Toldt and a thicker posterior layer known as the fascia of Zuckerkandl. These layers fuse superiorly with the diaphragm and laterally with the transversalis fascia. Medially, the anterior layer passes in front of the great vessels and is continuous with that of the contralateral side, while the posterior layer of Gerota's fascia fuses with the fascia covering the psoas and quadratus lumborum muscles, and the vertebral bodies. Inferiorly, the anterior and posterior leaves of Gerota's fascia fail to fuse and the perinephric fat is continuous with the pelvic fat. 4 As pus accumulates in the perinephric space it may extend in several directions. The pus may penetrate beneath or through Petit's lumbar triangle and present as a pointing or sponta-
The organisms isolated from perinephric abscesses usually are gram-negative rods, most commonly Proteus and Escherichia coli, which account for more than 50 per cent of the cases. 1 Of the abscesses cultured 14 per cent yield Staph. aureus and another 13 per cent yield more than 1 organism. Blood cultures are positive in 10 to 40 per cent of the cases and urine cultures are positive in 50 to 80 per cent. Pathogens isolated from abscess cultures do not always correlate with those isolated from the urine and some investigators have noted a 30 per cent discrepancy. 8 Sterile cultures account for 5 to 10 per cent of the cases and usually indicate inadequate culture technique (anaerobic organism), prior antibiotic coverage or a fastidious organism. Therefore, it is important to perform gramstain of purulent material obtained from abscess cavities and, if necessary, to perform special stains for acid-fast bacilli and the various fungi. 7
Read at annual meeting of American Urological Association, New Orleans, Louisiana, May 6-10, 1984. * Requests for reprints: Department of Urology, Box 656, University of Rochester Medical Center, 601 Elmwood Ave., Rochester, New York 14642.
At presentation the majority of patients were symptomatic for longer than 2 weeks. Thorley and associates noted that 50 per cent of the patients had symptoms for longer than 2 weeks, 1 while Adachi and Carter,1° and Truesdale and associates 3 re-
CLINICAL PRESENTATION
191
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SHEINFELD AND ASSOCIATES
ported an average duration of symptoms of 42 and 55 days, respectively. Pain, usually localized to the ipsilateral flank (70 per cent) or abdomen (45 per cent), is a common complaint. Less frequently, pleuritic chest pain may be present owing to diaphragmatic irritation from a highly situated abscess or one that is dissecting in the cephalad direction. Irritation of the psoas muscle, or iliohypogastric, ilioinguinal, genitofemoral or femoral-cutaneous nerves may refer the pain to the ipsilateral hip, thigh, inguinal area or genitalia. Most patients (83 per cent) also have a history of fever and chills. Approximately a third of the patients with a perinephric abscess complain of voiding symptoms, such as dysuria, urgency and frequency. This finding is in sharp contrast to early investigators who reported that voiding symptoms characteristically were absent in patients with this clinical entity and lends further support to the changing clinicopathological pattern of infection from extrarenal sources to those arising in the genitourinary system. 1 • 3 ' 7- 9 Weight loss, nausea, vomiting and weakness are less common complaints. The most common physical findings are flank or costovertebral angle tenderness (69 per cent), while abdominal tenderness is found in 46 per cent, and a palpable mass, either in the flank or abdomen, is found in 37 per cent. LABORATORY TESTS
Routine laboratory tests are helpful but nonspecific. In 1 study sedimentation rate was elevated invariably, with a third of the patients having an erythrocyte sedimentation rate of greater than 100 mm. per hour. 11 The white blood count usually is elevated, with approximately 90 per cent of the patients having greater than 10,000 leukocytes per mm. 3 with a shift to the left and 53 per cent having a white blood count of greater than 20,000 leukocytes per mm. 3 • About 25 per cent of the patients are anemic, with hemoglobin concentrations of less than 10 gm.jdl. and approximately 25 per cent have a blood urea nitrogen (BUN) level of greater than 40 mg./dl. 1 RADIOGRAPHIC STUDIES
Chest x-rays. The value of chest x-rays in the evaluation of a patient in whom a perinephric abscess is suspected should not be underestimated. Associated findings include an elevated or fixed hemidiaphragm, pleural effusion, empyema, lung abscess, lower lobe infiltrates or atelectasis, and apical scarring, particularly in patients with tuberculous abscesses. A.bdominal x-rays. Abdominal x-rays also may be helpful. 12 The most common abnormalities include thoracolumbar scoliosis with the concavity towards the side of the abscess (this must be interpreted with caution, since poor positioning, true scoliosis, neuromuscular disease and osseous abnormalities all may present with this finding), mass effect, renal calculi, poorly visualized or absent renal outline, poorly visualized or absent psoas shadows, gas pattern in the kidney or perinephric area and Mathe's sign of renal fixation. 13 A poorly visualized or absent psoas shadow must be interpreted with extreme caution. 1 The psoas shadow is a radiolucent band that usually is seen because retroperitoneal fat, having approximately three-fourths the radiographic density of muscle, has its greatest saggital depth along the psoas muscle. A poorly developed psoas muscle, obesity, abdominal masses, ascites or any process that causes edema of the retroperitoneal tissues and thereby increases their relative density will obscure or obliterate the lateral border of the psoas muscle. In a study of 200 IVPs in adults without upper tract abnormalities Parks found that the psoas shadow was not visualized in 18 patients bilaterally, and in 14 on the left and 8 on the right side. Of 100 IVPs in children without any genitourinary abnormalities 52 per cent failed to demonstrate at least 1 psoas shadow. 12 The examination for Mathe's sign of renal fixation may be
performed with fluoroscopy, prone and upright films, or inspiration and expiration films. The normal kidney descends from 2 to 6 cm. during deep inspiration or upon the patient assuming the upright position. Perirenal inflammatory changes will decrease or eliminate this mobility in up to 90 per cent of the patients. 7 However, tumors, previous infections and a prior operation must be excluded. !VP. An IVP with tomography will show an abnormality on the involved side approximately 80 to 85 per cent of the time. 1 These abnormalities include poor visualization or nonvisualization of the kidney, presence of a mass, displacement of the kidney, renal pelvis or ureter, calculi, calicectasis and urinary tract obstruction (with or without a calculus). Nuclear imaging. Radionuclide scanning with 67 gallium citrate or rnindium does not have a role in the diagnostic studies for a perinephric abscess. These studies require 48 to 72 hours following injection of the radionuclide before an adequate interpretation can be made. No anatomical detail is provided and increased uptake may be secondary to tumor, acute tubular necrosis, pyelonephritis or other renal parenchymal diseases. 14 Ultrasound. Following an IVP, either ultrasonography or a CT scan should be the next diagnostic technique. Ultrasonography is suited best for thin subjects. A sonogram of a perinephric abscess shows a sonolucent mass, usually with irregular walls and occasionally multiloculated, and internal echoes that represent necrotic and particulate debris. If the abscess is caused by a gas-forming organism the mass may be highly echogenic. CT scan. Most recent studies and our own experience indicate that a CT scan is the diagnostic technique of choice for the evaluation of a perinephric abscess, since it identifies the lesion, and defines precisely its extent and surrounding anatomy. 14- 16 Abnormalities on a CT scan include a soft tissue mass of central low attenuation (O to 20 Hounsfield units), an inflammatory wall with a slightly higher attenuation coefficient on unenhanced views, the rind sign (a rim of increased density in the wall of the abscess after injection of contrast material, which is secondary to the hypervascularity of the abscess wall), obliteration of surrounding tissue planes, ipsilateral enlargement of the kidney or psoas muscle, thickening of Gerota's fascia and gas or air-fluid levels within the lesion. 16 Subsequent needle aspiration of the abscess should then be done under sonographic, fluoroscopic or CT guidance following appropriate parenteral antibiotic coverage. An aminoglycoside and an antibiotic effective against Staph. aureus will reduce significantly the possibility of a severe septic episode. The only absolute contraindication to this procedure is the absence of a safe percutaneous route. 16 Obviously, great care must be taken to avoid the pleural cavity, colon, spleen, liver and other surrounding structures. Coagulopathic conditions usually can be corrected with the administration of appropriate clotting factors. Once the needle aspirate confirms the diagnosis of a perinephric abscess, it then should be drained percutaneously. TREATMENT
In a certain percentage of cases percutaneous abscess drainage in conjunction with parenteral antibiotics will suffice in the treatment of perinephric abscess. The catheters should be removed only after an adequate clinical response, that is once the fever has defervesced, the white blood count has returned to normal, drainage has stopped and followup studies, preferably repeat CT scans, show resolution of the abscess. 16• 17 Septation of an abscess can result in incomplete drainage unless there are intercommunications between the locules, or unless they are drained or disrupted individually. 16 Therefore, a number of patients will require a subsequent operation following percutaneous drainage of a perinephric abscess. The ability of the patient to tolerate an open procedure, as well as associated pathological findings and the viability of the involved kidney all contribute heavily in the choice of a subse-
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PERINEPHRIC ABSCESS
quent operation. Patients with poorly functioning or nonfunctioning kidneys, as well as those with multiple intrarenal abscesses in kidneys with extensive parenchymal damage will benefit from a nephrectomy, wide debridement and postoperative drainage. It equally is important to deal with predisposing factors, such as bladder outlet obstruction and urinary calculi, to avoid a delay in the clinical response, possible complications of urosepsis and recurrences. Until recently the morbidity and mortality rates for patients with perinephric abscess remained high. Errors and delays in diagnosis are responsible primarily for mortality rates as high as 57 per cent. In a series of 71 patients Salvatierra and associates noted a correct admission diagnosis in only 18 per cent, 6 while Thorley and associates reported a correct admission diagnosis of 36 per cent. 1 Up to 34 per cent of all perinephric abscesses are discovered at autopsy. 1 The most common misdiagnosis is pyelonephritis. In an effort to identify factors that would distinguish pyelonephritis from perinephric abscesses Thorley and associates studied 46 patients hospitalized with the diagnosis of pyelonephritis, 9 of whom actually had a perinephric abscess. 1 Based on this study Thorley and associates concluded that the duration of symptoms before hospitalization and the duration of fever after antibiotic treatment is started are the most important clinical features that distinguish these 2 entities. 1 Of 9 patients with a perinephric abscess 7 were symptomatic for longer than 5 days before hospitalization and none defervesced until the abscesses were drained surgically. Of the 37 patients with pyelonephritis 33 were symptomatic for less than 5 days before hospitalization and all defervesced within 4 days after antibiotic therapy was started, most within the first 2 days. 1
TABLE 2. Signs and symptoms in 15 patients at our hospital No.(%) Pain: Flank Abdominal Unspecified Tenderness: Flank Abdominal Mass Fever Chills White blood count (leukocytes/mm. 3 ): 10,000 20,000 BUN 40 mg./dL Voiding symptoms Wt. loss Nausea/vomiting Weakness Draining sinus Psoas sign/hip pain
4 (26,6) 4 (26,6)
2 (13.3) 3 (20.0) 1 (6,6) 2 (13.3) 10 (66.6) 6 (40,0) 14 (93.3)
8 (53.3) 2 (13,3) 4 (26.6)
2 (13,3) 2 (13.3) 3 (20,0) 1 (6,6) 2 (13.3)
ipsilateral hip pain. The average white blood count was 23,100 leukocytes per mm. 3 • The organisms isolated from the abscess were Proteus mirabilis (5 patients), E. coli (3), Staph. aureus (3), Klebsiella (3), Bacteroides fragilis (1), Pseudomonas (1), Morganella morganii (1) and acid-fast bacilli (1). Cultures of 4 abscesses yielded more than 1 organism. Twelve patients (80 per cent) were evaluated by a CT scan. Seven patients underwent percutaneous drainage of the abscess, including 3 who subsequently required nephrectomy of a nonfunctioning kidney. There were a total of 7 nephrectomies. Four patients underwent open drainage procedures. There were no postprocedure complications and no deaths in our series.
EXPERIENCE AT OUR HOSPITAL
CONCLUSIONS
The hospital records of 15 patients with a proved perinephric abscess seen between March 1979 and May 1983 were reviewed. The records were examined for age, sex, etiology of infection, predisposing factors, clinical signs and symptoms, laboratory abnormalities, radiographic evaluation, organisms isolated, therapeutic modalities, complications and length of hospitalization. Average patient age was 54 years and the female-to-male ratio was 2:1. The source of the perinephric abscess was noted to be of renal origin in 13 patients and of nonrenal (hematogenous) origin in 2. The most common predisposing factors were renal calculi (8 patients), a history of pyelonephritis or urinary tract infection (6), urinary tract obstruction (4) and diabetes mellitus (3) (table 1). The most common signs and symptoms are listed in table 2, Fever, chills, weakness, weight loss, and abdominal and/or ipsilateral flank pain were the common complaints. Four patients had significant voiding symptoms and 2 had marked
Insidious in onset and with variable symptomatology, the diagnosis of a perinephric abscess has been notoriously difficult to establish. 6 The advent of CT has facilitated the diagnosis and management of these potentially life-threatening abscesses. Furthermore, by defining precisely the exact site and extent of the abscess, as well as the surrounding structures, CT has made perinephric abscesses amenable to percutaneous drainage. 1" In conjunction with parenteral antibiotics percutaneous drainage is a safe, effective and, occasionally, definitive mode of therapy that is suited particularly to the high risk patient. It is widely applicable, and avoids the expense and risk of an operation and general anesthesia. 18 Surgical correction of underlying and predisposing conditions often is required. Renal. calculi, a history of urinary tract infection, diabetes mellitus and urinary tract obstruction are the most common predisposing conditions. Gram-negative rods have replaced Staph. aureus as the most common organism isolated from these abscesses. Since a perinephric abscess may present a variety of clinical pictures it always should be considered in cases of prolonged fever, particularly if the patient is unresponsive to antibiotic therapy and has a history of urinary tract infections, calculous disease, urinary tract obstruction, flank and/or abdominal pain or tenderness, and an elevated white blood count and erythrocyte sedimentation rate. Adachi and Carter state that "the most important single step in the diagnosis of a perinephric abscess is to remember that the condition exists" .10
TABLE 1. Predisposing factors in 15 patients at our hospital No,(%) Renal calculi Pyelonephritis/previous urinary tract infection Urinary tract obstruction: Calculi Neoplasm N eurogenic bladder Bladder outlet obstruction Benign prostatic hypertrophy Papillary necrosis Diabetes mellitus Others: Steroid therapy Compromised host Debilitated pt. Trauma Intravenous drug abuse Ureterovesical reflux
8 (53,5) 6 (40,0) 4 (26,6)
REFERENCES 3 (20,0) 3 (20.0)
1. Thorley, J. D., Jones, S. R. and Sanford, J.P.: Perinephric abscess.
Medicine, 53: 441, 1974. 2. Campbell, M. F.: Perinephritic abscess. Surg., Gynec. & Obst., 51: 674, 1930. 3. Truesdale, B. H., Rous, S. N. and Nelson, R. P.: Perinephric abscess: a review of 26 cases. J. Ural., 118: 910, 1977, 4. Atcheson, D. W.: Perinephric abscess with a review of 117 cases. J. Ural., 46: 201, 1941.
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5. Hotchkiss, R. S.: Perinephric abscess. Amer. J. Surg., 85: 471, 1953. 6. Salvatierra, 0., Jr., Bucklew, W. B. and Morrow, J. W.: Perinephric abscess: a report of 71 cases. J. Urol., 98: 296, 1967. 7. Saiki, J., Vaziri, N. D. and Barton, C.: Perinephric and intranephric abscesses: a review of the literature. West. J. Med., 136: 95, 1982. 8. Malgieri, J. J., Kursh, E. D. and Persky, L.: The changing clinicopathological pattern of abscesses in or adjacent to the kidney. J. Urol., 118: 230, 1977. 9. Timmons, J. W. and Perlmutter, A. D.: Renal abscess: a changing concept. J. Urol., 115: 299, 1976. 10. Adachi, R. T. and Carter, R.: Perinephric abscess: current concepts in diagnosis and management. Amer. Surg., 35: 72, 1968. 11. Obrant, 0.: Perirenal abscess. Acta Chir. Scand., 97: 338, 1949. 12. Parks, R. E.: The radiographic diagnosis of perinephric abscess. J. Urol., 64: 555, 1950.
13. Mathe, C. P.: Diagnosis and treatment ofperinephric abscess: renal fixation, a new roentgenographic diagnostic sign. Amer. J. Surg., 38: 35, 1937. 14. Mendez, G., Jr., Isikoff, M. B. and Morillo, G.: The role of computed tomography in the diagnosis of renal and perirenal abscesses. J. Urol., 122: 582, 1979. 15. Moody, T., Mills, P., Cochran, T. and Williams, D.: Computerized axial tomography in diagnosis of retroperitoneal abscess. Urology, 16: 536, 1980. 16. Gerzof, S. G. and Gale, M. E.: Computed tomography and ultrasonography for diagnosis and treatment of renal and retroperitoneal abscesses. Urol. Clin. N. Amer., 9: 185, 1982. 17. Gerzof, S. G.: Percutaneous drainage of renal and perirenal abscess. Urol. Rad., 2: 171, 1981. 18. Cronan, J. J., Amis, E. S., Jr. and Dorfman, G. S.: Percutaneous drainage ofrenal abscesses. Amer. J. Roentgen., 142: 351, 1984.
THE JOURNAL OF UROLOGY
Copyright© 1987 by The Williams & Wilkins Co.
Review Article PERINEPHRIC ABSCESS: CURRENT CONCEPTS JOEL SHEINFELD,* ERDAL ERTURK, ROBERT F. SPATARO
AND
ABRAHAM T. K. COCKETT
From the Departments of Urology and Radiology, School of Medicine and Dentistry, University of Rochester, Rochester, New York
Despite dramatic technical advances in the various fields of diagnostic radiology and the advent of sophisticated antimicrobial therapy, the prompt and accurate recognition of a perinephric abscess continues to elude even the most experienced urologist. Its onset and course are insidious, and its symptomatology is highly variable. Unrecognized and untreated, perinephric abscesses result in considerable morbidity and mortality. We present our recent experience with 15 patients with perinephric abscess and review the literature. Particular emphasis is placed on the pathogenesis, predisposing factors, clinical presentation, complications and bacteriology of perinephric abscesses. Pertinent radiological abnormalities on chest and abdominal x-rays, excretory urograms (IVPs), ultrasonograms and computerized tomography (CT) scans are discussed. Our experience indicates that CT is the diagnostic modality of choice. Effective treatment requires appropriate antibiotic coverage and drainage of the abscess. Newer percutaneous techniques have spared several patients from a major operation and have provided a viable alternative for patients who are poor surgical risks. The diagnosis of a perinephric abscess notoriously is difficult to make. 1 The condition frequently mimics intra-abdominal, neurological, orthopedic or lower urinary tract disease. 2 Untreated, a perinephric abscess almost invariably will result in death. Perinephric abscess is a rare entity, with the reported incidence ranging from 0.9 to 4.0 cases per 10,000 hospital admissions and comprising 0.2 per cent of all urological procedures. The right side is involved slightly more often than the left side, while the disease is bilateral in 2 per cent of the patients. 1
neously draining abscess. Downward extension between the anterior and posterior layers of Gerota's fascia may produce an abscess in the groin or paravesical area. The abscess may extend medially and penetrate into the peritoneum or laterally and perforate the colon. Finally, the process may extend superiorly as a subphrenic abscess or penetrate the diaphragm, resulting in empyema, lung abscess or perinephrobronchial fistula. 5 ETIOLOGY
Campbell classified a perinephric abscess according to its renal or extrarenal origin. 2 Currently, the majority ofperinephric abscesses can be attributed to renal causes, including rupture into the perinephric space of an intrarenal abscess, renal cortical abscess or pyonephrosis, as well as chronic or recurrent pyelonephritis (particularly in the presence of obstruction), xanthogranulomatous pyelonephritis and renal carbuncle. 1 • 6- 9 Before the advent of antibiotics, hematogenous seeding from a distant pyogenic focus accounted for 80 per cent of perinephric abscesses and the causative organism almost invariably was Staphylococcus aureus. 9 The retroperitoneal lymphatic channels provide a second avenue for the arrival of bacteria, and infection has been reported to ascend via the lymphatics from the bladder, seminal vesicles, prostate, fallopian tubes, or perirectal or other pelvic tissues. 2 Contiguous structures provide a third source for the extrarenal origin of a perinephric abscess. Inflammatory lesions of the liver, gallbladder, pancreas and high retrocecal appendix, as well as Crohn's disease and osteomyelitis of the ribs and vertebrae all have been implicated.
ANATOMICAL CONSIDERATIONS MICROBIOLOGY
A perinephric abscess is an accumulation of pus in the perinephric space, that is the space between the renal capsule and Gerota's fascia. 3 The perinephric fat surrounds both kidneys and adrenal glands, and is enclosed by Gerota's fascia, which is comprised of a thin anterior layer also known as the fascia of Toldt and a thicker posterior layer known as the fascia of Zuckerkandl. These layers fuse superiorly with the diaphragm and laterally with the transversalis fascia. Medially, the anterior layer passes in front of the great vessels and is continuous with that of the contralateral side, while the posterior layer of Gerota's fascia fuses with the fascia covering the psoas and quadratus lumborum muscles, and the vertebral bodies. Inferiorly, the anterior and posterior leaves of Gerota's fascia fail to fuse and the perinephric fat is continuous with the pelvic fat. 4 As pus accumulates in the perinephric space it may extend in several directions. The pus may penetrate beneath or through Petit's lumbar triangle and present as a pointing or sponta-
The organisms isolated from perinephric abscesses usually are gram-negative rods, most commonly Proteus and Escherichia coli, which account for more than 50 per cent of the cases. 1 Of the abscesses cultured 14 per cent yield Staph. aureus and another 13 per cent yield more than 1 organism. Blood cultures are positive in 10 to 40 per cent of the cases and urine cultures are positive in 50 to 80 per cent. Pathogens isolated from abscess cultures do not always correlate with those isolated from the urine and some investigators have noted a 30 per cent discrepancy. 8 Sterile cultures account for 5 to 10 per cent of the cases and usually indicate inadequate culture technique (anaerobic organism), prior antibiotic coverage or a fastidious organism. Therefore, it is important to perform gramstain of purulent material obtained from abscess cavities and, if necessary, to perform special stains for acid-fast bacilli and the various fungi. 7
Read at annual meeting of American Urological Association, New Orleans, Louisiana, May 6-10, 1984. * Requests for reprints: Department of Urology, Box 656, University of Rochester Medical Center, 601 Elmwood Ave., Rochester, New York 14642.
At presentation the majority of patients were symptomatic for longer than 2 weeks. Thorley and associates noted that 50 per cent of the patients had symptoms for longer than 2 weeks, 1 while Adachi and Carter,1° and Truesdale and associates 3 re-
CLINICAL PRESENTATION
191
192
SHEINFELD AND ASSOCIATES
ported an average duration of symptoms of 42 and 55 days, respectively. Pain, usually localized to the ipsilateral flank (70 per cent) or abdomen (45 per cent), is a common complaint. Less frequently, pleuritic chest pain may be present owing to diaphragmatic irritation from a highly situated abscess or one that is dissecting in the cephalad direction. Irritation of the psoas muscle, or iliohypogastric, ilioinguinal, genitofemoral or femoral-cutaneous nerves may refer the pain to the ipsilateral hip, thigh, inguinal area or genitalia. Most patients (83 per cent) also have a history of fever and chills. Approximately a third of the patients with a perinephric abscess complain of voiding symptoms, such as dysuria, urgency and frequency. This finding is in sharp contrast to early investigators who reported that voiding symptoms characteristically were absent in patients with this clinical entity and lends further support to the changing clinicopathological pattern of infection from extrarenal sources to those arising in the genitourinary system. 1 • 3 ' 7- 9 Weight loss, nausea, vomiting and weakness are less common complaints. The most common physical findings are flank or costovertebral angle tenderness (69 per cent), while abdominal tenderness is found in 46 per cent, and a palpable mass, either in the flank or abdomen, is found in 37 per cent. LABORATORY TESTS
Routine laboratory tests are helpful but nonspecific. In 1 study sedimentation rate was elevated invariably, with a third of the patients having an erythrocyte sedimentation rate of greater than 100 mm. per hour. 11 The white blood count usually is elevated, with approximately 90 per cent of the patients having greater than 10,000 leukocytes per mm. 3 with a shift to the left and 53 per cent having a white blood count of greater than 20,000 leukocytes per mm. 3 • About 25 per cent of the patients are anemic, with hemoglobin concentrations of less than 10 gm.jdl. and approximately 25 per cent have a blood urea nitrogen (BUN) level of greater than 40 mg./dl. 1 RADIOGRAPHIC STUDIES
Chest x-rays. The value of chest x-rays in the evaluation of a patient in whom a perinephric abscess is suspected should not be underestimated. Associated findings include an elevated or fixed hemidiaphragm, pleural effusion, empyema, lung abscess, lower lobe infiltrates or atelectasis, and apical scarring, particularly in patients with tuberculous abscesses. A.bdominal x-rays. Abdominal x-rays also may be helpful. 12 The most common abnormalities include thoracolumbar scoliosis with the concavity towards the side of the abscess (this must be interpreted with caution, since poor positioning, true scoliosis, neuromuscular disease and osseous abnormalities all may present with this finding), mass effect, renal calculi, poorly visualized or absent renal outline, poorly visualized or absent psoas shadows, gas pattern in the kidney or perinephric area and Mathe's sign of renal fixation. 13 A poorly visualized or absent psoas shadow must be interpreted with extreme caution. 1 The psoas shadow is a radiolucent band that usually is seen because retroperitoneal fat, having approximately three-fourths the radiographic density of muscle, has its greatest saggital depth along the psoas muscle. A poorly developed psoas muscle, obesity, abdominal masses, ascites or any process that causes edema of the retroperitoneal tissues and thereby increases their relative density will obscure or obliterate the lateral border of the psoas muscle. In a study of 200 IVPs in adults without upper tract abnormalities Parks found that the psoas shadow was not visualized in 18 patients bilaterally, and in 14 on the left and 8 on the right side. Of 100 IVPs in children without any genitourinary abnormalities 52 per cent failed to demonstrate at least 1 psoas shadow. 12 The examination for Mathe's sign of renal fixation may be
performed with fluoroscopy, prone and upright films, or inspiration and expiration films. The normal kidney descends from 2 to 6 cm. during deep inspiration or upon the patient assuming the upright position. Perirenal inflammatory changes will decrease or eliminate this mobility in up to 90 per cent of the patients. 7 However, tumors, previous infections and a prior operation must be excluded. !VP. An IVP with tomography will show an abnormality on the involved side approximately 80 to 85 per cent of the time. 1 These abnormalities include poor visualization or nonvisualization of the kidney, presence of a mass, displacement of the kidney, renal pelvis or ureter, calculi, calicectasis and urinary tract obstruction (with or without a calculus). Nuclear imaging. Radionuclide scanning with 67 gallium citrate or rnindium does not have a role in the diagnostic studies for a perinephric abscess. These studies require 48 to 72 hours following injection of the radionuclide before an adequate interpretation can be made. No anatomical detail is provided and increased uptake may be secondary to tumor, acute tubular necrosis, pyelonephritis or other renal parenchymal diseases. 14 Ultrasound. Following an IVP, either ultrasonography or a CT scan should be the next diagnostic technique. Ultrasonography is suited best for thin subjects. A sonogram of a perinephric abscess shows a sonolucent mass, usually with irregular walls and occasionally multiloculated, and internal echoes that represent necrotic and particulate debris. If the abscess is caused by a gas-forming organism the mass may be highly echogenic. CT scan. Most recent studies and our own experience indicate that a CT scan is the diagnostic technique of choice for the evaluation of a perinephric abscess, since it identifies the lesion, and defines precisely its extent and surrounding anatomy. 14- 16 Abnormalities on a CT scan include a soft tissue mass of central low attenuation (O to 20 Hounsfield units), an inflammatory wall with a slightly higher attenuation coefficient on unenhanced views, the rind sign (a rim of increased density in the wall of the abscess after injection of contrast material, which is secondary to the hypervascularity of the abscess wall), obliteration of surrounding tissue planes, ipsilateral enlargement of the kidney or psoas muscle, thickening of Gerota's fascia and gas or air-fluid levels within the lesion. 16 Subsequent needle aspiration of the abscess should then be done under sonographic, fluoroscopic or CT guidance following appropriate parenteral antibiotic coverage. An aminoglycoside and an antibiotic effective against Staph. aureus will reduce significantly the possibility of a severe septic episode. The only absolute contraindication to this procedure is the absence of a safe percutaneous route. 16 Obviously, great care must be taken to avoid the pleural cavity, colon, spleen, liver and other surrounding structures. Coagulopathic conditions usually can be corrected with the administration of appropriate clotting factors. Once the needle aspirate confirms the diagnosis of a perinephric abscess, it then should be drained percutaneously. TREATMENT
In a certain percentage of cases percutaneous abscess drainage in conjunction with parenteral antibiotics will suffice in the treatment of perinephric abscess. The catheters should be removed only after an adequate clinical response, that is once the fever has defervesced, the white blood count has returned to normal, drainage has stopped and followup studies, preferably repeat CT scans, show resolution of the abscess. 16• 17 Septation of an abscess can result in incomplete drainage unless there are intercommunications between the locules, or unless they are drained or disrupted individually. 16 Therefore, a number of patients will require a subsequent operation following percutaneous drainage of a perinephric abscess. The ability of the patient to tolerate an open procedure, as well as associated pathological findings and the viability of the involved kidney all contribute heavily in the choice of a subse-
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quent operation. Patients with poorly functioning or nonfunctioning kidneys, as well as those with multiple intrarenal abscesses in kidneys with extensive parenchymal damage will benefit from a nephrectomy, wide debridement and postoperative drainage. It equally is important to deal with predisposing factors, such as bladder outlet obstruction and urinary calculi, to avoid a delay in the clinical response, possible complications of urosepsis and recurrences. Until recently the morbidity and mortality rates for patients with perinephric abscess remained high. Errors and delays in diagnosis are responsible primarily for mortality rates as high as 57 per cent. In a series of 71 patients Salvatierra and associates noted a correct admission diagnosis in only 18 per cent, 6 while Thorley and associates reported a correct admission diagnosis of 36 per cent. 1 Up to 34 per cent of all perinephric abscesses are discovered at autopsy. 1 The most common misdiagnosis is pyelonephritis. In an effort to identify factors that would distinguish pyelonephritis from perinephric abscesses Thorley and associates studied 46 patients hospitalized with the diagnosis of pyelonephritis, 9 of whom actually had a perinephric abscess. 1 Based on this study Thorley and associates concluded that the duration of symptoms before hospitalization and the duration of fever after antibiotic treatment is started are the most important clinical features that distinguish these 2 entities. 1 Of 9 patients with a perinephric abscess 7 were symptomatic for longer than 5 days before hospitalization and none defervesced until the abscesses were drained surgically. Of the 37 patients with pyelonephritis 33 were symptomatic for less than 5 days before hospitalization and all defervesced within 4 days after antibiotic therapy was started, most within the first 2 days. 1
TABLE 2. Signs and symptoms in 15 patients at our hospital No.(%) Pain: Flank Abdominal Unspecified Tenderness: Flank Abdominal Mass Fever Chills White blood count (leukocytes/mm. 3 ): 10,000 20,000 BUN 40 mg./dL Voiding symptoms Wt. loss Nausea/vomiting Weakness Draining sinus Psoas sign/hip pain
4 (26,6) 4 (26,6)
2 (13.3) 3 (20.0) 1 (6,6) 2 (13.3) 10 (66.6) 6 (40,0) 14 (93.3)
8 (53.3) 2 (13,3) 4 (26.6)
2 (13,3) 2 (13.3) 3 (20,0) 1 (6,6) 2 (13.3)
ipsilateral hip pain. The average white blood count was 23,100 leukocytes per mm. 3 • The organisms isolated from the abscess were Proteus mirabilis (5 patients), E. coli (3), Staph. aureus (3), Klebsiella (3), Bacteroides fragilis (1), Pseudomonas (1), Morganella morganii (1) and acid-fast bacilli (1). Cultures of 4 abscesses yielded more than 1 organism. Twelve patients (80 per cent) were evaluated by a CT scan. Seven patients underwent percutaneous drainage of the abscess, including 3 who subsequently required nephrectomy of a nonfunctioning kidney. There were a total of 7 nephrectomies. Four patients underwent open drainage procedures. There were no postprocedure complications and no deaths in our series.
EXPERIENCE AT OUR HOSPITAL
CONCLUSIONS
The hospital records of 15 patients with a proved perinephric abscess seen between March 1979 and May 1983 were reviewed. The records were examined for age, sex, etiology of infection, predisposing factors, clinical signs and symptoms, laboratory abnormalities, radiographic evaluation, organisms isolated, therapeutic modalities, complications and length of hospitalization. Average patient age was 54 years and the female-to-male ratio was 2:1. The source of the perinephric abscess was noted to be of renal origin in 13 patients and of nonrenal (hematogenous) origin in 2. The most common predisposing factors were renal calculi (8 patients), a history of pyelonephritis or urinary tract infection (6), urinary tract obstruction (4) and diabetes mellitus (3) (table 1). The most common signs and symptoms are listed in table 2, Fever, chills, weakness, weight loss, and abdominal and/or ipsilateral flank pain were the common complaints. Four patients had significant voiding symptoms and 2 had marked
Insidious in onset and with variable symptomatology, the diagnosis of a perinephric abscess has been notoriously difficult to establish. 6 The advent of CT has facilitated the diagnosis and management of these potentially life-threatening abscesses. Furthermore, by defining precisely the exact site and extent of the abscess, as well as the surrounding structures, CT has made perinephric abscesses amenable to percutaneous drainage. 1" In conjunction with parenteral antibiotics percutaneous drainage is a safe, effective and, occasionally, definitive mode of therapy that is suited particularly to the high risk patient. It is widely applicable, and avoids the expense and risk of an operation and general anesthesia. 18 Surgical correction of underlying and predisposing conditions often is required. Renal. calculi, a history of urinary tract infection, diabetes mellitus and urinary tract obstruction are the most common predisposing conditions. Gram-negative rods have replaced Staph. aureus as the most common organism isolated from these abscesses. Since a perinephric abscess may present a variety of clinical pictures it always should be considered in cases of prolonged fever, particularly if the patient is unresponsive to antibiotic therapy and has a history of urinary tract infections, calculous disease, urinary tract obstruction, flank and/or abdominal pain or tenderness, and an elevated white blood count and erythrocyte sedimentation rate. Adachi and Carter state that "the most important single step in the diagnosis of a perinephric abscess is to remember that the condition exists" .10
TABLE 1. Predisposing factors in 15 patients at our hospital No,(%) Renal calculi Pyelonephritis/previous urinary tract infection Urinary tract obstruction: Calculi Neoplasm N eurogenic bladder Bladder outlet obstruction Benign prostatic hypertrophy Papillary necrosis Diabetes mellitus Others: Steroid therapy Compromised host Debilitated pt. Trauma Intravenous drug abuse Ureterovesical reflux
8 (53,5) 6 (40,0) 4 (26,6)
REFERENCES 3 (20,0) 3 (20.0)
1. Thorley, J. D., Jones, S. R. and Sanford, J.P.: Perinephric abscess.
Medicine, 53: 441, 1974. 2. Campbell, M. F.: Perinephritic abscess. Surg., Gynec. & Obst., 51: 674, 1930. 3. Truesdale, B. H., Rous, S. N. and Nelson, R. P.: Perinephric abscess: a review of 26 cases. J. Ural., 118: 910, 1977, 4. Atcheson, D. W.: Perinephric abscess with a review of 117 cases. J. Ural., 46: 201, 1941.
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5. Hotchkiss, R. S.: Perinephric abscess. Amer. J. Surg., 85: 471, 1953. 6. Salvatierra, 0., Jr., Bucklew, W. B. and Morrow, J. W.: Perinephric abscess: a report of 71 cases. J. Urol., 98: 296, 1967. 7. Saiki, J., Vaziri, N. D. and Barton, C.: Perinephric and intranephric abscesses: a review of the literature. West. J. Med., 136: 95, 1982. 8. Malgieri, J. J., Kursh, E. D. and Persky, L.: The changing clinicopathological pattern of abscesses in or adjacent to the kidney. J. Urol., 118: 230, 1977. 9. Timmons, J. W. and Perlmutter, A. D.: Renal abscess: a changing concept. J. Urol., 115: 299, 1976. 10. Adachi, R. T. and Carter, R.: Perinephric abscess: current concepts in diagnosis and management. Amer. Surg., 35: 72, 1968. 11. Obrant, 0.: Perirenal abscess. Acta Chir. Scand., 97: 338, 1949. 12. Parks, R. E.: The radiographic diagnosis of perinephric abscess. J. Urol., 64: 555, 1950.
13. Mathe, C. P.: Diagnosis and treatment ofperinephric abscess: renal fixation, a new roentgenographic diagnostic sign. Amer. J. Surg., 38: 35, 1937. 14. Mendez, G., Jr., Isikoff, M. B. and Morillo, G.: The role of computed tomography in the diagnosis of renal and perirenal abscesses. J. Urol., 122: 582, 1979. 15. Moody, T., Mills, P., Cochran, T. and Williams, D.: Computerized axial tomography in diagnosis of retroperitoneal abscess. Urology, 16: 536, 1980. 16. Gerzof, S. G. and Gale, M. E.: Computed tomography and ultrasonography for diagnosis and treatment of renal and retroperitoneal abscesses. Urol. Clin. N. Amer., 9: 185, 1982. 17. Gerzof, S. G.: Percutaneous drainage of renal and perirenal abscess. Urol. Rad., 2: 171, 1981. 18. Cronan, J. J., Amis, E. S., Jr. and Dorfman, G. S.: Percutaneous drainage ofrenal abscesses. Amer. J. Roentgen., 142: 351, 1984.