Case Report: Acute Focal Bacterial Pyelonephritis (Lobar Nephronia)-Presentation as a Palpable Abdominal Mass ELEANOR E. HARRIS, BA, MATTHEW SWEAT, MD, GEORGE R. ARONOFF, MD
ABSTRACT: Acute lobar nephronia, or focal pyelonephritis, is an uncommon form of renal infection with a distinct computerized tomographic appearance. A patient is presented with lobar nephronia characterized by fever, flank pain, urosepsis, and painful abdominal mass. Differentiating this condition from abscess or other renal mass is important, because the treatment of lobar nephronia is nonsurgical. The infection responds to antibiotic therapy. KEY INDEXING TERMS: Focal pyelonephritis; N ephronia. [Am J Med Sci 1992; 304(5):303-305.]
A
cute lobar nephronia is a form of focal pyelonephritis characterized by fever, flank pain, and pyuria. The diagnosis is confirmed with the findings of focal swelling of the renal parenchyma on an excretory urogram, solid mass with diminished echogenicity by sonography, or inhomogeneous enhancement after intravenous contrast medium on computed tomographic scans. We report one case of acute focal pyelonephritis in a patient with the extremely unusual finding of a tender, midline abdominal mass palpable during abdominal examination. Case Report A 35-year-old woman was admitted to the hospital complaining of worsening back pain that had existed for the past week. In the previous 24 hours she experienced fever and chills, mid-epigastric and right upper quadrant abdominal pain, nausea, and vomiting. She denied dysuria, urinary frequency or urgency, and hematuria. She was taking prednisone 5 mg every other day for Lupus erythematosus. She had undergone cholecystectomy for gallstones 4 years From the Department of Medicine, Nephrology Division, University of Louisville School of Medicine and Louisville Veterans AffairsMedical Center, Louisville, Kentucky. Correspondence: George R. Aronoff, MD, FACP, Kidney Disease Program, University of Louisville School of Medicine, 500 S. Floyd Street, Louisville, KY 40292.
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WARD A. KATSANIS, MD,
earlier and had had an appendectomy 6 years before admission. She had been treated with an antibiotic 6 months earlier for a presumed urinary tract infection. An examination showed her to be in distress from abdominal pain. Her blood pressure was 112/70 mm Hg and her pulse was SS/min without orthostasis. Her respiratory rate was IS/min and her temperature was 37.5° C. Her right flank was tender to percussion. Bowel sounds were present and there was no abdominal rigidity or guarding. There was a tender 3 X 5 cm right upper quadrant abdominal mass that protruded into the epigastrium. Laboratory studies included a peripheral white blood cell count of 24,500/IlL. Differential analysis of the white blood cells revealed 5% band forms, 84% mature polymorphonuclear leukocytes, and 11 % lymphocytes. Her blood urea concentration was 6.4 mmol/L and her serum creatinine concentration was 97 Ilmol/L. Microscopic examination of her urine revealed more than 50 white blood cells and one to four red blood cells in each high power field. Bacteria also were seen. Treatment with ampicillin and gentamicin was begun on admission to the hospital. Urine and blood cultures subsequently grew Escherichia coli sensitive to these antibiotics. Renal ultrasound examination showed the right kidney was 12.3 cm long and the left kidney was l1.S cm long. A 5.3 cm simple cyst was noted in the right kidney. A computed tomograph of the abdomen with contrast enhancement made the day after hospital admission is shown in Figure 1. Both kidneys demonstrated multiple wedgeshaped areas of decreased attenuation. The simple cyst of the right kidney was confirmed, and this kidney was shown to protrude to the right upper quadrant anterior abdominal wall. During the first five days of hospitalization, the patient's temperature increased to 40° C. She remained afebrile after the fourth hospital day and was discharged after 7 days, continuing to take oral antibiotics as an outpatient for a total of 14 days of antimicrobial treatment. A computed tomograph of the abdomen made 2 months after antibiotic treatment and resolution of the patient's symptoms is shown in Figure 2. The simple renal cyst of the right kidney was again seen. However, the right kidney no longer protruded into the anterior abdomen.
Discussion
A tender, upper quadrant or midline abdominal mass is unusual in patients with uncomplicated renal infection. Acute pyelonephritis is characterized by the sudden onset of fever, chills, urinary urgency, dysuria, and costovertebral angle tenderness. Microscopic examination of the urine reveals pyuria, hematuria, and bacteriuria. In most cases, this clinical presentation, supported by the laboratory confirmation, is sufficient ev-
303
Acute Lobar Nephronia
Figure 1. Enhanced computed abdominal tomograph showing multiple wedge-shaped areas of decreased attenuation in the right kidney. The kidney is swollen and extends to the anterior abdominal wall. A 5 cm simple cyst also is present.
idence for treating the patient with appropriate antibiotic therapy. Uncomplicated cases of pyelonephritis respond to antimicrobial treatment with rapid resolution of symptoms. The need for radiographic imaging of the kidneys is indicated by recurrent or refractory renal infection. Intravenous pyelography, renal sonography, and computed tomography may be helpful for evaluating abnormal urinary tract anatomy or the presence of a renal abscess. 1 Acute lobar nephronia, alternately termed acute focal bacterial nephritis, is an uncommon form of renal infection. Patients usually present with flank pain, fever, pyuria, and bacteriuria. Vomiting and abdominal pain also have been reported. 2 Renal imaging may show a focal renal mass on computed tomography, excretory urography, and renal sonography.2-5 Histologically, lobar nephronia is characterized by the finding of localized inflammation with interstitial edema, hyperemia, and leukocyte infiltration. Biopsy of the lesions also may include microabscesses. 6,7 This more severe form of pyelonephritis may be an intermediate phase of renal infection between simple pyelonephritis and renal abscess formation. s Clear differentiation from abscess or tumor is important, because treatment for acute lobar nephronia is nonsurgical. This infection usually responds to in-
304
tensive antibiotic therapy. As in other reported cases, computerized renal tomography in our patient demonstrated wedge-shaped, poorly outlined areas of decreased nephrographic density. This radiographic study easily differentiated the lesions from renal abscess, which would have appeared as a well-defined lower density mass within the renal parenchyma or a perinephric abscess outside the renal parenchyma. The present case is unusual in that the patient had a tender, right upper quadrant abdominal mass that extended to the mid-epigastrium. Palpable abdominal mass in a patient with lobar nephronia has been reported only once before.9 Davidson and Talner described a patient with a pulsatile left paramedian abdominal mass. Selective renal arteriography showed increased size of the lower pole of the right kidney with slow filling of the vessels. Their report does not indicate that the palpable mass was the kidney nor that the mass resolved with treatment. The distinction between acute lobar nephronia and other causes of palpable renal mass is needed to avoid unnecessary surgery. As in our case, patients with acute focal pyelonephritis may experience a protracted febrile illness. However, continued appropriate antibiotic treatment results in resolution of the focal mass, restoration of normal renal parenchyma, and minimal fo~ cal renal tissue loss.2,4,9
November 1992 Volume 304 Number 5
Harris et al
Figure 2. Computed abdominal tomograph made 2 months after antibiotic treatment. The kidney no longer protrudes into the anterior abdomen. The renal parenchyma appears normal. The cyst remains unchanged.
References 1. Wycks JB and Thornbury JR: Acute renal infections in adults. Radiol Clin North Am 17:245-257, 1979. 2. Zaontz MR, Pahira JJ, Wolfman M, Gargurevich AJ, Zeman RK: Acute focal bacterial nephritis: A systematic approach to diagnosis and treatment. J UroI133:752-756, 1985. 3. Rosenfeld AT, Glickman MG, Taylor KJW, Crade M, Hodson J : Acute focal bacterial nephritis (acute lobar nephronia). Radiology 132:553-561, 1979. 4. Wegenke JD, Malek GH, Alter AJ, Olson JG: Acute lobular nephronia. J Urol 135:343-345, 1986. 5. Nosher JL, Tamminen JL, Amorosa JK, Kallich M: Acute focal bacterial nephritis. Am J Kidney Dis 11:36-42, 1988.
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6. Silver TM, Kass EJ, Thornbury JR, Konnak JW, Wolfman MG: The radiological spectrum of acute pyelonephritis in adults and adoles!!ents. Radiology 118:65-71, 1976. 7. Morehouse HT, Weiner SN, Hoffman JC: Imaging in inflammatory disease of the kidney. American Journal of Roentgenology 143:135-141,1984. 8. McDonough WD, Sandler CM, Benson GS: Acute focal bacterial nephritis: focal pyelonephritis that may simulate renal abscess. J Urol 126:670-673, 1981. 9. Davidson AJ, Talner LB: Urographic and angiographic abnormalities in adult-onset acute bacterial nephritis. Radiology 106: 249-256, 1973.
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ABSTRACT: Acute lobar nephronia, or focal pyelonephritis, is an uncommon form of renal infection with a distinct computerized tomographic appearance. A patient is presented with lobar nephronia characterized by fever, flank pain, urosepsis, and painful abdominal mass. Differentiating this condition from abscess or other renal mass is important, because the treatment of lobar nephronia is nonsurgical. The infection responds to antibiotic therapy. KEY INDEXING TERMS: Focal pyelonephritis; N ephronia. [Am J Med Sci 1992; 304(5):303-305.]
A
cute lobar nephronia is a form of focal pyelonephritis characterized by fever, flank pain, and pyuria. The diagnosis is confirmed with the findings of focal swelling of the renal parenchyma on an excretory urogram, solid mass with diminished echogenicity by sonography, or inhomogeneous enhancement after intravenous contrast medium on computed tomographic scans. We report one case of acute focal pyelonephritis in a patient with the extremely unusual finding of a tender, midline abdominal mass palpable during abdominal examination. Case Report A 35-year-old woman was admitted to the hospital complaining of worsening back pain that had existed for the past week. In the previous 24 hours she experienced fever and chills, mid-epigastric and right upper quadrant abdominal pain, nausea, and vomiting. She denied dysuria, urinary frequency or urgency, and hematuria. She was taking prednisone 5 mg every other day for Lupus erythematosus. She had undergone cholecystectomy for gallstones 4 years From the Department of Medicine, Nephrology Division, University of Louisville School of Medicine and Louisville Veterans AffairsMedical Center, Louisville, Kentucky. Correspondence: George R. Aronoff, MD, FACP, Kidney Disease Program, University of Louisville School of Medicine, 500 S. Floyd Street, Louisville, KY 40292.
THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES
WARD A. KATSANIS, MD,
earlier and had had an appendectomy 6 years before admission. She had been treated with an antibiotic 6 months earlier for a presumed urinary tract infection. An examination showed her to be in distress from abdominal pain. Her blood pressure was 112/70 mm Hg and her pulse was SS/min without orthostasis. Her respiratory rate was IS/min and her temperature was 37.5° C. Her right flank was tender to percussion. Bowel sounds were present and there was no abdominal rigidity or guarding. There was a tender 3 X 5 cm right upper quadrant abdominal mass that protruded into the epigastrium. Laboratory studies included a peripheral white blood cell count of 24,500/IlL. Differential analysis of the white blood cells revealed 5% band forms, 84% mature polymorphonuclear leukocytes, and 11 % lymphocytes. Her blood urea concentration was 6.4 mmol/L and her serum creatinine concentration was 97 Ilmol/L. Microscopic examination of her urine revealed more than 50 white blood cells and one to four red blood cells in each high power field. Bacteria also were seen. Treatment with ampicillin and gentamicin was begun on admission to the hospital. Urine and blood cultures subsequently grew Escherichia coli sensitive to these antibiotics. Renal ultrasound examination showed the right kidney was 12.3 cm long and the left kidney was l1.S cm long. A 5.3 cm simple cyst was noted in the right kidney. A computed tomograph of the abdomen with contrast enhancement made the day after hospital admission is shown in Figure 1. Both kidneys demonstrated multiple wedgeshaped areas of decreased attenuation. The simple cyst of the right kidney was confirmed, and this kidney was shown to protrude to the right upper quadrant anterior abdominal wall. During the first five days of hospitalization, the patient's temperature increased to 40° C. She remained afebrile after the fourth hospital day and was discharged after 7 days, continuing to take oral antibiotics as an outpatient for a total of 14 days of antimicrobial treatment. A computed tomograph of the abdomen made 2 months after antibiotic treatment and resolution of the patient's symptoms is shown in Figure 2. The simple renal cyst of the right kidney was again seen. However, the right kidney no longer protruded into the anterior abdomen.
Discussion
A tender, upper quadrant or midline abdominal mass is unusual in patients with uncomplicated renal infection. Acute pyelonephritis is characterized by the sudden onset of fever, chills, urinary urgency, dysuria, and costovertebral angle tenderness. Microscopic examination of the urine reveals pyuria, hematuria, and bacteriuria. In most cases, this clinical presentation, supported by the laboratory confirmation, is sufficient ev-
303
Acute Lobar Nephronia
Figure 1. Enhanced computed abdominal tomograph showing multiple wedge-shaped areas of decreased attenuation in the right kidney. The kidney is swollen and extends to the anterior abdominal wall. A 5 cm simple cyst also is present.
idence for treating the patient with appropriate antibiotic therapy. Uncomplicated cases of pyelonephritis respond to antimicrobial treatment with rapid resolution of symptoms. The need for radiographic imaging of the kidneys is indicated by recurrent or refractory renal infection. Intravenous pyelography, renal sonography, and computed tomography may be helpful for evaluating abnormal urinary tract anatomy or the presence of a renal abscess. 1 Acute lobar nephronia, alternately termed acute focal bacterial nephritis, is an uncommon form of renal infection. Patients usually present with flank pain, fever, pyuria, and bacteriuria. Vomiting and abdominal pain also have been reported. 2 Renal imaging may show a focal renal mass on computed tomography, excretory urography, and renal sonography.2-5 Histologically, lobar nephronia is characterized by the finding of localized inflammation with interstitial edema, hyperemia, and leukocyte infiltration. Biopsy of the lesions also may include microabscesses. 6,7 This more severe form of pyelonephritis may be an intermediate phase of renal infection between simple pyelonephritis and renal abscess formation. s Clear differentiation from abscess or tumor is important, because treatment for acute lobar nephronia is nonsurgical. This infection usually responds to in-
304
tensive antibiotic therapy. As in other reported cases, computerized renal tomography in our patient demonstrated wedge-shaped, poorly outlined areas of decreased nephrographic density. This radiographic study easily differentiated the lesions from renal abscess, which would have appeared as a well-defined lower density mass within the renal parenchyma or a perinephric abscess outside the renal parenchyma. The present case is unusual in that the patient had a tender, right upper quadrant abdominal mass that extended to the mid-epigastrium. Palpable abdominal mass in a patient with lobar nephronia has been reported only once before.9 Davidson and Talner described a patient with a pulsatile left paramedian abdominal mass. Selective renal arteriography showed increased size of the lower pole of the right kidney with slow filling of the vessels. Their report does not indicate that the palpable mass was the kidney nor that the mass resolved with treatment. The distinction between acute lobar nephronia and other causes of palpable renal mass is needed to avoid unnecessary surgery. As in our case, patients with acute focal pyelonephritis may experience a protracted febrile illness. However, continued appropriate antibiotic treatment results in resolution of the focal mass, restoration of normal renal parenchyma, and minimal fo~ cal renal tissue loss.2,4,9
November 1992 Volume 304 Number 5
Harris et al
Figure 2. Computed abdominal tomograph made 2 months after antibiotic treatment. The kidney no longer protrudes into the anterior abdomen. The renal parenchyma appears normal. The cyst remains unchanged.
References 1. Wycks JB and Thornbury JR: Acute renal infections in adults. Radiol Clin North Am 17:245-257, 1979. 2. Zaontz MR, Pahira JJ, Wolfman M, Gargurevich AJ, Zeman RK: Acute focal bacterial nephritis: A systematic approach to diagnosis and treatment. J UroI133:752-756, 1985. 3. Rosenfeld AT, Glickman MG, Taylor KJW, Crade M, Hodson J : Acute focal bacterial nephritis (acute lobar nephronia). Radiology 132:553-561, 1979. 4. Wegenke JD, Malek GH, Alter AJ, Olson JG: Acute lobular nephronia. J Urol 135:343-345, 1986. 5. Nosher JL, Tamminen JL, Amorosa JK, Kallich M: Acute focal bacterial nephritis. Am J Kidney Dis 11:36-42, 1988.
THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES
6. Silver TM, Kass EJ, Thornbury JR, Konnak JW, Wolfman MG: The radiological spectrum of acute pyelonephritis in adults and adoles!!ents. Radiology 118:65-71, 1976. 7. Morehouse HT, Weiner SN, Hoffman JC: Imaging in inflammatory disease of the kidney. American Journal of Roentgenology 143:135-141,1984. 8. McDonough WD, Sandler CM, Benson GS: Acute focal bacterial nephritis: focal pyelonephritis that may simulate renal abscess. J Urol 126:670-673, 1981. 9. Davidson AJ, Talner LB: Urographic and angiographic abnormalities in adult-onset acute bacterial nephritis. Radiology 106: 249-256, 1973.
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